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     * Ligne n°35 : * Patent Resources
     * Ligne n°62 : A main power source is, for example, an ordinary Pb battery. At the time of starting an engine, the main power source supplies power to a starter. The main power source is given a higher priority than an auxiliary power source to supply power to ordinary loads. The auxiliary power source is a high performance battery (e.g., Li ion battery), which has superior charge acceptance capability and better state detectability over the main power source. The auxiliary power source stores regenerative power, which is generated by a generator at the time of deceleration of a vehicle, and is used as a redundant power source for the main power source. The main power source and the auxiliary power source are connected to each other through a supply circuit, which has a DC/DC converter, and a second supply circuit, which has a switch.
     * Ligne n°124 : 1. A vehicle power supply system comprising: a generator, which is mounted on a vehicle; a main power source, to which an ordinary load is connected; an auxiliary powersource, which is connected to the generator, wherein the auxiliary power source recovers regenerative electric power, which is generated by the generator using kinetic energy or thermal energy, and the auxiliary power source stores electric power that isgenerated by the generator; a first supply circuit, which connects the auxiliary power source to the main power source and the ordinary load through a DC/DC converter; a second supply circuit, which is in parallel with the first supply circuit andwhich connects the auxiliary power source to the main power source and the ordinary load through a switch; and a control means for controlling operation of the DC/DC converter and operation of the switch, wherein the control means is enabled to selectone of: a first control state, in which the DC/DC
       converter is driven, and
     * Ligne n°127 : 2. A vehicle power supply system comprising: a generator, which is driven by an engine to generate electric power; a main power source, to which an ordinary load, such as a lamp or an audio device, is connected; an auxiliary power source,which is connected to the generator, wherein the auxiliary power source recovers regenerative electric power, which is generated by the generator at time of deceleration of a vehicle, and the auxiliary power source stores electric power that is generatedby the generator through driving of the generator by the engine; a first supply circuit, which connects the auxiliary power source to the main power source and the ordinary load through a DC/DC converter; a second supply circuit, which is in parallelwith the first supply circuit and which connects the auxiliary power source to the main power source and the ordinary load through a switch; and a control means for controlling operation of the DC/DC converter and operation of the
       switch, wherein
     * Ligne n°132 : 4. The vehicle power supply system according to claim 1, wherein the main power source has a greater nominal voltage or nominal capacity over the auxiliary power source.
     * Ligne n°134 : 5. The vehicle power supply system according to claim 1, wherein the main power source has a smaller nominal voltage or nominal capacity over the auxiliary power source.
     * Ligne n°136 : 6. The vehicle power supply system according to claim 1, wherein the main power source and the auxiliary power source have a common operational range, in which a working voltage of the main power source generally coincides with a workingvoltage of the auxiliary power source.
     * Ligne n°138 : 7. The vehicle power supply system according to claim 1, wherein the main power source has greater low-temperature discharge characteristics than the auxiliary power source.
     * Ligne n°140 : 8. The vehicle power supply system according to claim 1, wherein the auxiliary power source has a greater charge acceptance capability and a greater state detectability than the main power source.
     * Ligne n°142 : 9. The vehicle power supply system according to claim 1, wherein: the main power source is one of a lead battery, a Li ion battery and a Ni hydrogen battery; and the auxiliary power source is one of a lead battery, a Li ion battery, a Nihydrogen battery and an electrical double-layer capacitor.
     * Ligne n°144 : 10. The vehicle power supply system according to claim 1, wherein at time of supplying power from the auxiliary power source to the main power source and the ordinary load, the control means selects the second control state when the voltage ofthe auxiliary power source has fallen to or below an allowable rated voltage of the ordinary load.
     * Ligne n°146 : 11. The vehicle power supply system according to claim 1, wherein the control means selects one of the first control state and the second control state in accordance with the power supply level, and the power supply level is a level of powersupplied from the auxiliary power source to the main power source and the ordinary load, or a level of power supplied from the main power source to the auxiliary power source and the ordinary load.
     * Ligne n°150 : 13. The vehicle power supply system according to claim 1, wherein the control means selects one of the first control state and the second control state in accordance with a voltage difference between the main power source and the auxiliarypower source.
     * Ligne n°152 : 14. The vehicle power supply system according to claim 13, wherein: the control means selects the second control state when the voltage difference between the main power source and the auxiliary power source is equal to or below a predeterminedvalue; and the control means selects the first control state when the voltage difference between the main power source and the auxiliary power source is above the predetermined value.
     * Ligne n°154 : 15. The vehicle power supply system according to claim 1, wherein the control means selects one of the first control state and the second control state in accordance with: a voltage difference between the main power source and the auxiliarypower source; and a level of power supplied from the auxiliary power source to the main power source and the ordinary load, or a level of power supplied from the main power source to the auxiliary power source and the ordinary load.
     * Ligne n°156 : 16. The vehicle power supply system according to claim 15, wherein: the control means first selects the first control state when the voltage of the auxiliary power source is higher than that of the main power source and also the power levelsupplied from the auxiliary power source to the main power source and the ordinary load is greater than a predetermined value; and the control means then shifts from the first control state to the second control state after the voltage of the auxiliarypower source falls to or below the allowable rated voltage of the ordinary load.
     * Ligne n°158 : 17. The vehicle power supply system according to claim 1, further comprising: a third supply circuit, which supplies electric power from the auxiliary power source to an important load, which is involved in a basic running operation or a safetyoperation of the vehicle; and a fourth supply circuit, which supplies electric power from the main power source to the important load, wherein each of the third supply circuit and the fourth supply circuit has a diode, which limits a reverse flow of anelectric current therethrough.
     * Ligne n°160 : 18. The vehicle power supply system according to claim 1, further comprising: a third supply circuit, which supplies electric power from the auxiliary power source to an important load, which is involved in a basic running operation or a safetyoperation of the vehicle; and a fourth supply circuit, which supplies electric power from the main power source to the important load, wherein the third supply circuit has a diode, which limits a reverse flow of an electric current therethrough, in acase where the main power source has a higher nominal voltage or nominal capacity over the auxiliary power source.
     * Ligne n°162 : 19. The vehicle power supply system according to claim 1, further comprising: a third supply circuit, which supplies electric power from the auxiliary power source to an important load, which is involved in a basic running operation or a safetyoperation of the vehicle; and a fourth supply circuit, which supplies electric power from the main power source to the important load, wherein the fourth supply circuit has a diode, which limits a reverse flow of an electric current therethrough, in acase the main power source has a lower nominal voltage or nominal capacity over the auxiliary power source.
     * Ligne n°164 : 20. The vehicle power supply system according to claim 17, wherein the control means opens the switch when one of the main power source and the auxiliary power source fails in a state where the second control state is selected by the controlmeans.
     * Ligne n°166 : 21. The vehicle power supply system according to claim 20, wherein the control means opens the switch when short-circuiting occurs between a cathode and an anode of one of the main power source and the auxiliary power source.
     * Ligne n°168 : 22. The vehicle power supply system according to claim 17, wherein the control means opens the switch when performance of the main power source falls.
     * Ligne n°170 : 23. The vehicle power supply system according to claim 17, wherein the control means opens the switch when performance of the auxiliary power source falls.
     * Ligne n°172 : 24. The vehicle power supply system according to claim 20, wherein the control means stops the DC/DC converter when one of the main power source and the auxiliary power source fails in a state where the first control state is selected by thecontrol means.
     * Ligne n°176 : 26. The vehicle power supply system according to claim 1, wherein the ordinary load, which is connected to the main power source, includes an electrical load, which requires a dark current after stopping of the engine.
     * Ligne n°178 : 27. The vehicle power supply system according to claim 1, wherein at time of shifting from the first control state to the second control state or at time of shifting from the second control state to the first control state, the control meansincreases an output voltage of the DC/DC converter to a higher one of a voltage of the main power source and a voltage of the auxiliary power source or decreases the output voltage of the DC/DC converter to a lower one of the voltage of the main powersource and the voltage of the auxiliary power source, and then the control means shifts from the first control state to the second control state or shifts from the second control state to the first control state.
     * Ligne n°186 : 31. The vehicle power supply system according to claim 1, wherein the control means senses a charge acceptance capability of the main power source based on an output state of the DC/DC converter when the first control state is selected by thecontrol means.
     * Ligne n°188 : 32. The vehicle power supply system according to claim 1, wherein: the control means senses a voltage of the auxiliary power source and an output voltage of the DC/DC converter based on a running state of the vehicle; and the control meanscontrols an output of the generator based on a sensed result of the voltage of the auxiliary power source and of the output voltage of the DC/DC converter.
     * Ligne n°190 : 33. The vehicle power supply system according to claim 1, wherein the auxiliary power source supplies electric power to an electrical load, which does not require a dark current.
     * Ligne n°194 : 35. The vehicle power supply system according to claim 1, further comprising a dark current blocking means for blocking the dark current, wherein the auxiliary power source supplies electric power to an electrical load, which does not requirethe dark current.
     * Ligne n°196 : 36. The vehicle power supply system according to claim 1, wherein an auxiliary power source switch is connected in series with the auxiliary power source.
     * Ligne n°198 : 37. The vehicle power supply system according to claim 36, wherein the auxiliary power source switch is disposed between the generator and the auxiliary power source in such a manner that the auxiliary power source switch is positioned on agenerator side of an input side connection of the DC/DC converter.
     * Ligne n°202 : 39. The vehicle power supply system according to claim 1, wherein in a case where a fully charged state of the auxiliary power source is sensed at time of performing regenerative power generation of the generator, the generator carries out theregenerative power generation at a voltage that is lower than a voltage of the auxiliary power source measured in the fully charged state of the auxiliary power source and supplies electric power to the ordinary load in one of the first control state andthe second control state.
     * Ligne n°204 : 40. The vehicle power supply system according to claim 3, wherein in a case where a fully charged state of the auxiliary power source is sensed at time of performing regenerative power generation of the generator, the generator carries out theregenerative power generation at a voltage that is lower than a voltage of the auxiliary power source measured in the fully charged state of the auxiliary power source and supplies electric power to the ordinary load in one of the first control state,the second control state and the third control state.
     * Ligne n°206 : 41. The vehicle power supply system according to claim 1, wherein the main power source is maintained in a fully charged state in the first control state.
     * Ligne n°208 : 42. A vehicle power supply system comprising: a generating means for generating regenerative energy at time of decelerating a vehicle; a high-performance main power storage means for directly storing the regenerative energy, which is generatedby the generating means, and for supplying electric power to an electrical load, which is mounted on the vehicle; an auxiliary power storage means for receiving and storing the electric power supplied from the main power storage means, wherein theauxiliary power storage means has a greater discharge characteristics at a low temperature than the main power storage means; and a starting device power source switching means for selecting one or both of the main power storage means and the auxiliarypower storage means as a power source based on an engine starting temperature to supply electric power to a starting device for starting an engine at time of starting the engine, wherein the engine starting temperature is an engine
       temperature or
     * Ligne n°211 : 43. The vehicle power supply system according to claim 42, wherein: a temperature range below a predetermined temperature T1 is an extremely low temperature range; a temperature range between the predetermined temperature T1 and apredetermined temperature T2 (T1<T2) is a low temperature range; a temperature range between the predetermined temperature T2 and a predetermined temperature T3 (T2<T3) is a normal temperature range; a temperature range above the predeterminedtemperature T3 is a high temperature range; the starting device power source switching means selects the main power storage means when the engine starting temperature is in the normal temperature range; and the starting device power source switchingmeans switches to use both the main power storage means and the auxiliary power storage means when the engine starting temperature is in one of the extremely low temperature range and the high temperature range.
     * Ligne n°217 : 46. A vehicle power supply system comprising: a generating means for generating regenerative energy at time of decelerating a vehicle; a high-performance main power storage means for directly storing the regenerative energy, which is generatedby the generating means, and for supplying electric power to an electrical load, which is mounted on the vehicle; an auxiliary power storage means for receiving and storing the electric power supplied from the main power storage means, so that theauxiliary power storage means is charged, wherein the auxiliary power storage means has superior discharge characteristics at a low temperature over the main power storage means; an automatic engine stopping/starting control device, which automaticallycontrols stopping and restarting of an engine; and a starting device power source switching means for selecting one of the auxiliary power storage means and the main power storage means as a power source to supply electric power to a
       starting device
     * Ligne n°218 : forstarting the engine, wherein the starting device power source switching means selects the auxiliary power storage means at time of starting the engine first time and selects the main power storage means at time of restarting the engine through use of theautomatic engine stopping/starting control device.
     * Ligne n°275 : The invention relates to a vehicle power supply system having two batteries (a main power source and an auxiliary power source).
     * Ligne n°303 : To achieve the first objective mentioned above, a first aspect of the present application provides a vehicle power supply system including: a generator, which is mounted on a vehicle; a main power source, to which an ordinary load, such as a lampor an audio device, is connected; an auxiliary power source, which is connected to the generator, wherein the auxiliary power source recovers regenerative electric power, which is generated by the generator using kinetic energy, such as kinetic energy ofdeceleration, or thermal energy, such as thermal energy of exhaust heat, and the auxiliary power source stores electric power that is generated by the generator; a first supply circuit, which connects the auxiliary power source to the main power sourceand the ordinary load through a DC/DC converter; a second supply circuit, which is in parallel with the first supply circuit and which connects the auxiliary power source to the main power source and the ordinary load
       through a switch; and a
     * Ligne n°306 : With this construction, since regenerative energy can be recovered directly to the auxiliary power source from the generator without passing through the DC/DC converter, energy recovery can be carried out efficiently. Since the main power sourceis charged by the auxiliary power source via the first supply circuit and the second supply circuit (i.e. it is not connected to the generator directly), for example when the generator is carrying out regeneration during deceleration of the vehicle, nolarge voltage fluctuations act on the main power source, and it is possible to supply power stably to the electrical loads connected to the main power source.
     * Ligne n°308 : Since the control means can select a first control state and a second control state in correspondence with the running state of the vehicle and the charge states of the main power source and the auxiliary power source, the efficiency of chargingfrom the auxiliary power source to the main power source or from the main power source to the auxiliary power source can be raised.
     * Ligne n°310 : The vehicle power supply system described above is preferably constructed so that the generator is driven by the engine, and the auxiliary power source, which is connected to the generator, recovers regenerative electric power, which is generatedby the generator at time of deceleration of a vehicle, and the auxiliary power source stores electric power that is generated by the generator through driving of the generator by the engine.
     * Ligne n°312 : With this construction, since energy regenerated during vehicle deceleration can be recovered directly to the auxiliary power source without going through the DC/DC converter, energy recovery can be carried out with good efficiency.
     * Ligne n°314 : In the vehicle power supply system described above, the control means may be also enabled to select a third control state, in which the DC/DC converter is driven, and the switch is closed. In this case, for example when there is no surplus inthe output capability of the DC/DC converter, since power can be supplied from the auxiliary power source to the main power source or from the main power source to the auxiliary power source with the third control state selected, the thermal affects canbe reduced.
     * Ligne n°316 : In the vehicle power supply system described above, preferably the main power source has a greater nominal voltage or nominal capacity over the auxiliary power source. In this case, power can be supplied from the main power source to theauxiliary power source just by the switch being turned on. Furthermore, since the voltage of the auxiliary power source is lower, the voltage difference between the generator and the auxiliary power source is greater than in an ordinary combination of agenerator and a main power source only, and power generated by the generator can be stored more efficiently.
     * Ligne n°318 : In the vehicle power supply system described above, the main power source has a smaller nominal voltage or nominal capacity over the auxiliary power source. In this case, when power regenerated during deceleration is stored in the auxiliarypower source, since the voltage of the auxiliary power source is higher than that of the main power source, regenerative electric power can be supplied to the ordinary loads from the auxiliary power source just by turning on the switch.
     * Ligne n°320 : In the vehicle power supply system described above, alternatively, the nominal voltage of the main power source may coincide with the nominal voltage of the auxiliary power source. In this case, when power regenerated during deceleration isstored in the auxiliary power source, the charge percentage of the auxiliary power source becomes higher than that of the main power source to cause an increase in the voltage of the auxiliary power source. Thus, regenerative power can be supplied fromthe auxiliary power source to the ordinary loads just by closing the switch.
     * Ligne n°322 : In the vehicle power supply system described above, preferably the main power source and the auxiliary power source have a common operational range, in which a working voltage of the main power source generally coincides with a working voltage ofthe auxiliary power source. In this case, when one of the power sources has failed, redundancy of a power source can be ensured easily, and the safety of the vehicle as dependent on the power supply system improves. When the second control state isselected and power is exchanged between the main power source and the auxiliary power source, voltage fluctuation caused by voltage difference when the switch is turned on/off can be suppressed. Also, with a combination of two power sources (main powersource and auxiliary power source) having a small voltage difference so that their working voltages have ranges where they are approximately the same, when a series regulator is used as the DC/DC converter, voltage adjustment with
       that series
     * Ligne n°325 : In the vehicle power supply system described above, preferably the main power source has superior low-temperature discharge characteristics over the auxiliary power source. By connecting the starter to a main power source having goodlow-temperature discharge characteristics, it is possible to improve the startability of the engine at low temperatures.
     * Ligne n°327 : In the vehicle power supply system described above, preferably the auxiliary power source has superior charge acceptance capability and better state detectability over the main power source. In this case, energy recovery during vehicledeceleration can be carried out efficiently.
     * Ligne n°329 : In the vehicle power supply system described above, preferably, the main power source is one of a lead battery, a Li ion battery and a Ni hydrogen battery, and the auxiliary power source is one of a lead battery, a Li ion battery, a Ni hydrogenbattery and an electrical double-layer capacitor. When lead batteries are used for the main power source and the auxiliary power source, it is possible to keep down their cost and achieve both energy recovery during deceleration and stable power supplyto the ordinary loads. When a Li ion battery or a Ni hydrogen battery is used as the main power source, the life of the power supply system as a whole can be increased. When a Li ion battery, a Ni hydrogen battery or an electrical double-layercapacitor is used as the auxiliary power source, the regeneration capability during deceleration can be increased and its charge acceptance capability is also excellent.
     * Ligne n°331 : In the vehicle power supply system described above, preferably, at time of supplying power from the auxiliary power source to the main power source and the ordinary load, the control means selects the second control state when the voltage of theauxiliary power source has fallen to or below an allowable rated voltage of the ordinary load. In this case, power can be supplied with an efficient switch (the second supply circuit) without applying stress to the ordinary loads.
     * Ligne n°333 : In the vehicle power supply system described above, when a level of power supplied from the auxiliary power source to the main power source and the ordinary load, or a level of power supplied from the main power source to the auxiliary powersource and the ordinary load, is called as a power supply level, the control means selects one of the first control state and the second control state in accordance with the power supply level. Since the characteristics of the DC/DC converter and theswitch differ (may be suitable or unsuitable) depending on the power supply level, by selecting either the first control state or the second control state in accordance with the power supply level it is possible to optimize the combination.
     * Ligne n°337 : In the vehicle power supply system described above, the control means may select one of the first control state and the second control state in accordance with a voltage difference between the main power source and the auxiliary power source. Inthis case, the states of the main power source and the auxiliary power source can be sensed by their voltages only, and an optimal control state can be selected in accordance with the sensed voltage difference between the two power sources.
     * Ligne n°339 : In the vehicle power supply system described above, preferably the control means selects the second control state when the voltage difference between the main power source and the auxiliary power source is equal to or below a predetermined value,and the control means selects the first control state when the voltage difference between the main power source and the auxiliary power source is above the predetermined value. In this case, when the voltage difference between the two power sources islarge, the voltages can be adjusted in the DC/DC converter and supplied in a low voltage difference state, and when the voltage difference between the two power sources is small, the power can be supplied with an efficient switch (the second supplycircuit).
     * Ligne n°341 : In the vehicle power supply system described above, when a level of power supplied from the auxiliary power source to the main power source and the ordinary load, or a level of power supplied from the main power source to the auxiliary powersource and the ordinary load, is called as a power supply level, the control means may select one of the first control state and the second control state in accordance with the voltage difference between the main power source and the auxiliary powersource and the power supply level. By selecting the control state based on both the power supply level and the voltage difference between the two power sources instead of the power supply level alone or the voltage difference between the two powersources alone, it is possible to select a more optimal control state.
     * Ligne n°343 : In the vehicle power supply system described above, preferably, the control means first selects the first control state when the voltage of the auxiliary power source is higher than that of the main power source and also the power level suppliedfrom the auxiliary power source to the main power source and the ordinary load is greater than a predetermined value and the control means then shifts from the first control state to the second control state after the voltage of the auxiliary powersource falls to or below the allowable rated voltage of the ordinary load. In this case, no overvoltage is applied to electrical loads such as lights, and reduction in the lives of the electrical loads can be suppressed. Efficient power supply using aswitch becomes possible.
     * Ligne n°345 : In the vehicle power supply system described above, preferably, there are further provided third and fourth supply circuits. The third supply circuit supplies electric power from the auxiliary power source to an important load, which is involvedin a basic running operation or a safety operation of the vehicle. The fourth supply circuit supplies electric power from the main power source to the important load, wherein each of the third supply circuit and the fourth supply circuit has a diode,which limits a reverse flow of an electric current therethrough. With this construction, since it is possible to provide redundancy of a power source with respect to the important loads, even when one or the other of the main power source and theauxiliary power source has failed, power can be supplied to the important loads without fail, and the safety of the vehicle improves. By the third supply circuit and the fourth supply circuit each being provided with a diode, since
       reverse currents canbe
     * Ligne n°348 : In the vehicle power supply system described above, preferably, there are further provided third and fourth supply circuits, which are different from the above ones. The third supply circuit supplies electric power from the auxiliary powersource to an important load, which is involved in a basic running operation or a safety operation of the vehicle. The fourth supply circuit supplies electric power from the main power source to the important load, wherein the third supply circuit has adiode, which limits a reverse flow of an electric current therethrough, in a case where the main power source has a higher nominal voltage or nominal capacity over the auxiliary power source. With this construction, since it is possible to provideredundancy of a power source with respect to the important loads, even when one or the other of the main power source and the auxiliary power source has failed, power can be supplied to the important loads without fail, and the safety of
       the
     * Ligne n°349 : vehicleimproves. By the third supply circuit being provided with a diode, since current can be prevented from flowing reversely through the third supply circuit from the main power source, which has a higher nominal voltage than the auxiliary power source, astable power supply to the important loads can be ensured. Also, since a diode is provided in the third supply circuit only, compared to a case where diodes are provided in both the third supply circuit and the fourth supply circuit, a reduction in costcorresponding to the reduction in the number of diodes is possible. Furthermore, when power is supplied to the important loads from the main power source, the power can be supplied efficiently, without suffering a loss due to a diode.
     * Ligne n°351 : In the vehicle power supply system described above, preferably, there are further provide third and fourth supply circuits, which are different from the above ones. The third supply circuit supplies electric power from the auxiliary power sourceto an important load, which is involved in a basic running operation or a safety operation of the vehicle, and the fourth supply circuit supplies electric power from the main power source to the important load, wherein the fourth supply circuit has adiode, which limits a reverse flow of an electric current therethrough, in a case the main power source has a lower nominal voltage or nominal capacity over the auxiliary power source. With this construction, since it is possible to provide redundancyof a power source with respect to the important loads, even when one or the other of the main power source and the auxiliary power source has failed, power can be supplied to the important loads without fail, and the safety of the
       vehicle improves.
     * Ligne n°352 : Bythe fourth supply circuit being provided with a diode, since current can be prevented from flowing reversely through the fourth supply circuit from the auxiliary power source, which has a higher nominal voltage than the main power source, a stable powersupply to the important loads can be ensured. Also, since a diode is provided in the fourth supply circuit only, compared to a case where diodes are provided in both the third supply circuit and the fourth supply circuit, a reduction in costcorresponding to the reduction in the number of diodes is possible. Furthermore, when power is supplied to the important loads from the auxiliary power source, the power can be supplied efficiently, without suffering a loss due to a diode.
     * Ligne n°354 : In the vehicle power supply system described above, preferably, the control means opens the switch when one of the main power source and the auxiliary power source fails in a state where the second control state is selected by the control means. For example, when the main power source has failed (e.g., grounded), since by turning the switch off it is possible to separate the failed main power source from the auxiliary power source, power can be supplied stably from the auxiliary power source tothe important loads, and the redundancy of a power source with respect to the important loads can be ensured.
     * Ligne n°356 : In the vehicle power supply system described above, preferably, the control means opens the switch when short-circuiting occurs between a cathode and an anode of one of the main power source and the auxiliary power source. Since this separatesthe main power source from the auxiliary power source, redundancy of a power supply to the ordinary loads from the power source functioning normally can be realized.
     * Ligne n°358 : In the vehicle power supply system described above, preferably, the control means opens the switch when performance of the main power source falls. Since this separates the main power source from the auxiliary power source, redundancy of a powersupply to the ordinary loads from the auxiliary power source can be realized.
     * Ligne n°360 : In the vehicle power supply system described above, preferably, the control means opens the switch when performance of the auxiliary power source falls. Since this separates the main power source from the auxiliary power source, redundancy of apower supply to the ordinary loads from the main power source can be realized.
     * Ligne n°362 : In the vehicle power supply system described above, preferably, the control means stops the DC/DC converter when one of the main power source and the auxiliary power source fails in a state where the first control state is selected by the controlmeans. For example when the main power source has failed (e.g., grounded), since by stopping the DC/DC converter it is possible to separate the failed main power source from the auxiliary power source, power can be supplied stably from the auxiliarypower source to the important loads, and redundancy of a power source with respect to the important loads can be ensured.
     * Ligne n°366 : In the vehicle power supply system described above, the ordinary load, which is connected to the main power source, may include an electrical load, which requires a dark current after stopping of the engine. The dark current is a current that isrequired to maintain a minimum function of the electrical load even when an ignition key of the vehicle is turned off. In this case, after the engine has stopped, with respect to the electrical loads needing a dark current from the main power source,power can be supplied from the main power source.
     * Ligne n°368 : In the vehicle power supply system described above, preferably, at time of shifting from the first control state to the second control state or at time of shifting from the second control state to the first control state, the control meansincreases an output voltage of the DC/DC converter to a higher one of a voltage of the main power source and a voltage of the auxiliary power source or decreases the output voltage of the DC/DC converter to a lower one of the voltage of the main powersource and the voltage of the auxiliary power source, and then the control means shifts from the first control state to the second control state or shifts from the second control state to the first control state. Since this makes it possible to suppressvoltage fluctuations occurring when the control state is changed over, flickering of lights and so on can be prevented.
     * Ligne n°372 : In the vehicle power supply system described above, preferably, the control means makes an output voltage of the DC/DC converter generally equal to an output voltage of the generator. In this way, it is possible to limit voltage fluctuations ofthe main power source, and thereby it is possible to implement stable voltage supply to the electrical loads. Furthermore, a contact arcing of the switch provided in the second power supply circuit can be made small to allow a size reduction.
     * Ligne n°374 : In the vehicle power supply system described above, preferably, the control means may control an output voltage of the generator such that the output voltage of the generator generally coincides with an output voltage of the DC/DC converter whenthe first control state is selected by the control means. Since this makes it possible to suppress voltage fluctuation of the main power source, it is possible to realize a stable voltage supply to the electrical loads. Contact arcing of the switchprovided in the second supply circuit can be made small and the switch can be made small.
     * Ligne n°376 : In the vehicle power supply system described above, the control means may sense a charge acceptance capability of the main power source based on an output state of the DC/DC converter when the first control state is selected by the control means. In this case, since it is not necessary for the charge acceptance capability of the main power source to be sensed with a sensor, a low-cost system can be realized.
     * Ligne n°378 : In the vehicle power supply system described above, the control means may sense a voltage of the auxiliary power source and an output voltage of the DC/DC converter based on a running state of the vehicle, and the control means may control anoutput of the generator based on a sensed result of the voltage of the auxiliary power source and of the output voltage of the DC/DC converter. By this means it is possible to control the output of the generator efficiently in accordance with therunning state of the vehicle.
     * Ligne n°380 : In the vehicle power supply system described above, the auxiliary power source may supply electric power to an electrical load, which does not require a dark current. For example, with respect to battery death of the main power source that wouldnormally occur when the vehicle is parked for a long period or left with a door half-open, by cutting the power supply to devices of which resetting is allowable, it is possible to prevent life and performance reduction of the main power source, and withrespect to electrical loads not needing a dark current, power can be supplied from the auxiliary power source.
     * Ligne n°384 : In the vehicle power supply system described above, there may be further provided a dark current blocking means for blocking the dark current, wherein the auxiliary power source supplies electric power to an electrical load (e.g., an electricalload, such as an ECU, which allows resetting of its internal memory), which enables blocking of dark current. By this means, even when dark current has been blocked by the dark current blocking means, power can be supplied from the auxiliary powersource.
     * Ligne n°386 : In the vehicle power supply system described above, an auxiliary power source switch may be connected in series with the auxiliary power source. In this case, for example when the auxiliary power source has failed, since the auxiliary powersource can be separated from the main system by the auxiliary power source switch being turned off, the safety of the main system can be ensured.
     * Ligne n°388 : In the vehicle power supply system described above, preferably, the auxiliary power source switch is disposed between the generator and the auxiliary power source in such a manner that the auxiliary power source switch is positioned on agenerator side of an input side connection of the DC/DC converter. In this case, the input voltage of the DC/DC converter can be limited to the voltage of the auxiliary power source, and the cost of the DC/DC converter can be reduced.
     * Ligne n°390 : In the vehicle power supply system described above, the DC/DC converter may include a series regulator. The objective of this is to remove noise caused by power device switching by taking advantage of the fact that the voltage difference betweenthe main power source and the auxiliary power source is small (or their voltages are the same), and by this means it is possible to prevent the circuit being complicated by noise countermeasures.
     * Ligne n°392 : In the vehicle power supply system described above, preferably, in a case where a fully charged state of the auxiliary power source is sensed at time of performing regenerative power generation of the generator during, for example, decelerationof the vehicle, the generator carries out the regenerative power generation at a voltage that is lower than a voltage of the auxiliary power source measured in the fully charged state of the auxiliary power source and supplies electric power to theordinary load in one of the first control state and the second control state. When the auxiliary power source is charged further after it has become fully charged, there is a risk of battery deterioration or the like caused by overcharging. To avoidthis, preferably, when it has been sensed by voltage or charge level detecting means or the like that the auxiliary power source is fully charged, the generator is controlled to a voltage such that it cannot charge the auxiliary power
       source (a
     * Ligne n°393 : lowervoltage than the that of the auxiliary power source), and power supply to the ordinary loads is effected by means of the first control state or the second control state. In this case, for example on roads such as long downhill slopes, even after theauxiliary power source has become fully charged by regenerative power generation, by consuming regenerative electric power with the ordinary loads, it is possible to utilize the regenerative electric power effectively.
     * Ligne n°395 : In the vehicle power supply system described above, in a case where a fully charged state of the auxiliary power source is sensed at time of performing regenerative power generation of the generator during, for example, deceleration of thevehicle, the generator may carry out the regenerative power generation at a voltage that is lower than a voltage of the auxiliary power source measured in the fully charged state of the auxiliary power source and may supply electric power to the ordinaryload in one of the first control state, the second control state and the third control state.
     * Ligne n°397 : In the vehicle power supply system described above, the main power source may be maintained in a fully charged state in the first control state. By the battery state of the main power source being sensed based on a battery voltage or dischargecurrent and power from the auxiliary power source or the generator being supplied to the ordinary loads using the DC/DC converter (the first control state), it is possible to keep the main power source in a fully charged state. By this means, whereaswhen the main power source is for example a lead battery or the like a phenomenon of the battery life deteriorating due to cumulative discharge is known, this can be suppressed and increased life can be achieved.
     * Ligne n°399 : Next, to achieve the second objective mentioned earlier, a second aspect of the present application provides a vehicle power supply system including: a generating means for generating regenerative energy at time of decelerating a vehicle; ahigh-performance main power storage means for directly storing the regenerative energy, which is generated by the generating means, and for supplying electric power to an electrical load, which is mounted on the vehicle; an auxiliary power storage meansfor receiving and storing the electric power supplied from the main power storage means, wherein the auxiliary power storage means has superior discharge characteristics at a low temperature over the main power storage means; and a starting device powersource switching means for selecting one or both of the main power storage means and the auxiliary power storage means as a power source based on an engine starting temperature to supply electric power to a starting device for
       starting an engine at
     * Ligne n°404 : In the vehicle power supply system according to this second aspect of the application, preferably, a temperature range below a predetermined temperature T1 is called as an extremely low temperature range; a temperature range between thepredetermined temperature T1 and a predetermined temperature T2 (T1<T2) is called as a low temperature range; a temperature range between the predetermined temperature T2 and a predetermined temperature T3 (T2<T3) is called as a normal temperaturerange; a temperature range above the predetermined temperature T3 is called as a high temperature range; the starting device power source switching means selects the main power storage means when the engine starting temperature is in the normaltemperature range; and the starting device power source switching means switches to use both the main power storage means and the auxiliary power storage means when the engine starting temperature is in one of the extremely low temperature range and
       thehigh
     * Ligne n°412 : In the vehicle power supply system of the second aspect, preferably, there is provided an automatic engine stopping/starting control device, which automatically controls stopping and restarting of an engine, and a starting device power sourceswitching means selects the auxiliary power storage means at time of starting the engine first time and selects the main power storage means at time of restarting the engine through use of the automatic engine stopping/starting control device. With thisconstruction, since either the main power storage means or the auxiliary power storage means is selected as the power source of the starting device depending on whether the engine is being started for the first time or being restarted after beingautomatically stopped, the main power storage means and the auxiliary power storage means can be used effectively in accordance with their respective characteristics.
     * Ligne n°469 : FIG. 3 is a voltage waveform graph of a main power source on engine starting in the first embodiment.
     * Ligne n°533 : The power supply system S includes a generator 1 and two power sources (a main power source 2 and an auxiliary power source 3) and supplies electric power to electrical loads (described below) mounted on the vehicle. The generator 1 is driven bythe engine (not shown).
     * Ligne n°535 : The generator 1 is an alternator, which has an IC regulator. The generator 1 is driven by the engine through a drive belt and generates a voltage of, for example, 13 to 14 V. The generator 1 is connected directly to the auxiliary power source(sub-power source) 3 and is also connected to the main power source 2 through a power supply circuit described below.
     * Ligne n°537 : The power supply circuit includes a first supply circuit 5 and a second supply circuit 7, which are connected in parallel between the auxiliary power source 3 and the main power source 2. The first supply circuit 5 includes a DC/DC converter 4,which uses, for example, a series regulator. The second supply circuit 7 includes a switch 6. Although in FIG. 1, a relay-type switch 6 is shown in the second supply circuit 7, a semiconductor switch may be alternatively used instead of the relay-typeswitch 6.
     * Ligne n°539 : The main power source 2 is, for example, an ordinary Pb (lead) battery and produces a voltage of 12 to 13 V (nominal voltage 12 V). The main power source 2 is given a higher priority for supplying electric power to the ordinary electrical loads8 than the auxiliary power source 3. Important loads (further discussed later), which are involved in a basic running operation and a safety operation of the vehicle, are connected to the main power source 2 through a third supply circuit 9. The thirdsupply circuit 9 includes diodes 10, 11, which limit a reverse flow of an electric current from the auxiliary power source 3 side.
     * Ligne n°541 : The auxiliary power source 3 is a high-performance battery (e.g., a Lithium ion battery), which has superior charge acceptance capability over the main power source 2 and which allows easy state detection. Furthermore, the auxiliary power source3 has a smaller internal resistance per unit capacity over the main power source 2 and produces a voltage of, for example, 9 to 12 V (nominal voltage 10.8 V). The auxiliary power source 3, for example, recovers regenerative electric power, which isgenerated by the generator 1 during deceleration of the vehicle. Also, the auxiliary power source 3 stores other electric power generated by the generator 1 such as electric power generated by the generator 1 in a non-deceleration period. Theabove-mentioned important loads are connected to the generator 1 and the auxiliary power source 3 through a fourth supply circuit 12. The fourth supply circuit 12 includes a diode 13, which limits a reverse flow of an electric current from
       the mainpower source
     * Ligne n°544 : The above-mentioned ordinary loads 8 include a starter 8a and other ordinary loads 8b mounted on the vehicle. The starter 8a starts (cranks) the engine. The other ordinary loads 8b include, for example, lamps, wipers, audio devices and anair-conditioning system. Again, the main power source 2 is given the higher priority for supplying electric power to these ordinary loads 8b than the auxiliary power source 3. However, when a power supply capability of the main power source 2 isreduced to a low level, the auxiliary power source 3 or the generator 1 is used to supply electric power to the ordinary loads 8b.
     * Ligne n°546 : The important loads, which are involved in the basic running operation and the safety operation of the vehicle, include, for example, a control unit (hereinafter, referred to as a safety ECU 16) and an electronic control unit (hereinafter,referred to as a system ECU 17). The control unit (the safety ECU 16) electronically controls various actuators 14 through a relay 15. The actuators 14 are involved in the basic running operation and/or the safety operation of the vehicle. Theelectronic control unit (the system ECU 17) electronically controls the power supply system S (e.g., the generator 1, the DC/DC converter 4, the switch 6). Even in a case where either the main power source 2 or the auxiliary power source 3 fails, theimportant loads can directly receive electric power from the remaining one of the main power source 2 and the auxiliary power source 3. That is, redundancy of a power source with respect to the important loads is provided.
     * Ligne n°554 : At step 10, an IG key (ignition key), which is an engine start switch, is turned to an ST position (a position for supplying electric power to the starter 8a). At step 11, power is supplied from the main power source 2 to the starter 8a. Atstep 12, it is determined whether the output voltage of the auxiliary power source 3 is equal to or above a fixed value. The voltage of the auxiliary power source 3 can be sensed by, for example, a voltmeter 18 shown in FIG. 1. When the result of thisdetermination is YES, control proceeds to the following step 13. In contrast, when the determination result is NO, control jumps to step 15 where the supply of electric power from the auxiliary power source 3 to the starter 8a is stopped.
     * Ligne n°556 : At step 13, a timing for supplying electric power from the auxiliary power source 3 to the starter 8a is determined. Specifically, it is determined whether the voltage across the terminals of the main power source 2 has recovered to apredetermined voltage. Alternatively, it may be determined whether fixed time has elapsed from the start of power supply to the starter 8a. As shown in FIG. 3, the voltage across the terminals of the main power source 2 drops sharply when a largecurrent flows to the starter 8a in an initial stage and then gradually recovers while dipping slightly each time a piston passes a top dead center. Accordingly, it is possible to determine the timing for supplying electric power from the auxiliary powersource 3 to the starter 8a by monitoring the voltage across the terminals of the main power source 2.
     * Ligne n°558 : At step 14, when the determination result of step 13 is YES, the switch 6 provided in the second supply circuit 7 is switched on, i.e., turned on, so that power is supplied from the auxiliary power source 3 to the starter 8a through the secondsupply circuit 7 (this will be called power assistance). At step 15, it is determined whether the engine has started. This starting determination can be made based on, for example, the engine speed or the voltage across the terminals of the main powersource 2. When the result of this determination is NO, control proceeds to step 16. In contrast, when the determination result is YES, control proceeds to step 17. At step 16, the engine start operation is carried out once again. At step 17, the IGkey is turned from the ST position to an OFF position, and the present control operation is terminated.
     * Ligne n°560 : According to the first embodiment, by performing the power assistance through use of the auxiliary power source 3 at the predetermined timing after the initiation of the power supply from the main power source 2 to the starter 8a, the output ofthe starter 8a is increased, and the engine can be started more quickly. In particular, in a vehicle equipped with an automatic stopping and restarting device (idle stop device), each time the engine is restarted after being automatically stopped, thestarting feeling experienced by the occupants of the vehicle can be improved since the starting time is shorter.
     * Ligne n°562 : Furthermore, there are the two electric power supply paths to the safety ECU 16, which is an important load. These two power supply paths include a first supply path, which connects the main power source 2 to the safety ECU 16 through the thirdsupply circuit 9, and a second supply path, which connects the auxiliary power source 3 to the safety ECU 16 through the fourth supply circuit 12. Thus, even when one of the two power sources or one of the two paths fails, power can be still supplied bymeans of the remaining power source and the remaining path, thereby implementing the redundancy. Furthermore, since the third supply circuit 9 and the fourth supply circuit 12 are provided with the diodes 10 and 13, respectively, for limiting a reverseflow of current, the two power sources (the main power source 2 and the auxiliary power source 3) are never connected to each other through the third supply circuit 9 or the fourth supply circuit 12.
     * Ligne n°566 : Also, in the case of the power supply system S set forth in the first embodiment, the main power source 2 has the higher output voltage (nominal voltage) over the auxiliary power source 3. However, it should be noted that the present inventionis equally applicable to a case where the auxiliary power source 3 has a higher output voltage (nominal voltage) than the main power source 2. For example, the main power source 2 may produce a voltage of 12 to 13 V (nominal voltage 12 V) as in thefirst embodiment, and the auxiliary power source 3 may produce a voltage of 12 to 16.4 V (nominal voltage 14.4 V). In such an instance, since the output voltage of the auxiliary power source 3 is higher, the generating capacity of the generator 1 shouldbe correspondingly high to produce a voltage of 13 to 17 V.
     * Ligne n°568 : Further alternatively, the output voltage (nominal voltage) of the main power source 2 may be set to be the same as the output voltage (nominal voltage) of the auxiliary power source 3. In this case, when regenerative electric power derived fromthe deceleration is stored in the auxiliary power source 3, the State of Charge (SOC), which is an available capacity of a battery expressed as a percentage of its rated capacity, of the auxiliary power source 3 becomes higher than that of the main powersource 2. Thus, the voltage of the auxiliary power source 3 is higher, and therefore the regenerative electric power can be supplied from the auxiliary power source 3 to the ordinary loads by simply closing the switch 6.
     * Ligne n°572 : Next, as a second embodiment, a power supply control operation for controlling supply of power from the generator 1 or the auxiliary power source 3 to the main power source 2 will be described with reference to a flowchart shown in FIG. 4. Thisis a method in which the charge level of the auxiliary power source 3 is sensed and is used for the power supply control operation.
     * Ligne n°574 : At step 20, it is determined whether the output capability of the DC/DC converter 4 is greater than the total power consumption of all of the electrical loads (this will be referred to as an overall load value), and the charge capacity per unittime of the auxiliary power source 3 is greater than the overall load value. When the determination result is YES, control proceeds to step 21. In contrast, when the determination result is NO, control proceeds to step 22. At step 21, since there isthe surplus in the charge capacity of the auxiliary power source 3 with respect to the overall load value, and there is also the surplus in the output capability of the DC/DC converter 4, the power generation by the generator 1 is cut off, and electricpower is supplied from the auxiliary power source 3 to the main power source 2 through the first supply circuit 5 having the DC/DC converter 4 (first control state).
     * Ligne n°576 : At step 22, it is determined whether the output capability of the DC/DC converter 4 is below the overall load value, and furthermore the capacity per unit time of the auxiliary power source 3 is greater than the overall load value, oralternatively the temperature of the DC/DC converter 4 is higher than a fixed value. When the determination result is YES, control proceeds to step 23. In contrast, when the determination result is NO, control proceeds to step 24. At step 23, sincethere is the surplus in the charge capacity of the auxiliary power source 3 with respect to the overall load value, but there is no surplus in the output capability of the DC/DC converter 4 (or alternatively, the temperature of the DC/DC converter 4 ishigh), power generation by the generator 1 is cut off, and electric power is supplied from the auxiliary power source 3 to the main power source 2 through the first supply circuit 5 and the second supply circuit 7 (shown as a switch circuit
       in thefigure) (third
     * Ligne n°579 : At step 24, it is determined whether the output capability of the DC/DC converter 4 is equal to or below the overall load value, and furthermore the capacity per unit time of the auxiliary power source 3 is equal to or below the overall loadvalue. When the determination result is YES, control proceeds to step 25. In contrast, when it is NO, control proceeds to step 26. At step 25, since there is no surplus in the charge capacity of the auxiliary power source 3 with respect to the overallload value, and furthermore there is no surplus in the output capability of the DC/DC converter 4 (but, the temperature of the DC/DC converter 4 is equal to or below a fixed value), power generation (at a Lo level) by the generator 1 is carried out, andelectric power is supplied from the generator 1 to the main power source 2 through the first supply circuit 5 and the second supply circuit 7 (third control state).
     * Ligne n°581 : At step 26, it is determined whether the temperature of the DC/DC converter 4 is higher than a fixed value, or the auxiliary power source 3 capacity is higher than a fixed value. When the determination result is YES, control proceeds to step 27. In contrast, when it is NO, control proceeds to step 28. At step 27, to prevent heat-induced failure of the DC/DC converter 4, and to prevent overcharging of the auxiliary power source 3, electric power is supplied from the generator 1 to the main powersource 2 using the second supply circuit 7 only (second control state). At this time, the power generation level (Lo) of the generator 1 is a level, at which power supply that corresponds to the ordinary loads 8b is possible even if the auxiliary powersource 3 is fully charged.
     * Ligne n°583 : At step 28, it is determined whether the charge capacity of the auxiliary power source 3 is within a first corresponding predetermined range (e.g., between 40% and 50%). When the determination result is YES, control proceeds to step 29. Incontrast, when the determination result is NO, control proceeds to step 30. At step 29, since the charge capacity of the auxiliary power source 3 is low, the generating capacity of the generator 1 is raised (to a Hi level. The Lo and Hi levels arerelative terms. That is, the Lo level is used to express a relatively low power generation level of the generator, and the Hi level is used to express a relatively high power generation level of the generator, which is higher than the Lo level). Also,when high loads, which consume a large amount of electric power, have been turned on, an idle speed is increased by a predetermined amount (first idle increase).
     * Ligne n°585 : At step 30, it is determined whether the charge capacity of the auxiliary power source 3 is within a second corresponding predetermined range (e.g., between 30% to 40%). When the determination result is YES, control proceeds to step 31. Incontrast, when the determination result is NO, control proceeds to step 32. At step 31, since the charge capacity of the auxiliary power source 3 is low, or the charge capacity of the auxiliary power source 3 is not increased even though the powergeneration capacity of the generator 1 has been increased, the first idle increase is carried out, and also the supply of power to the ordinary loads 8b is cut off (or limited). When the high load, which is among the ordinary loads 8b and consumes alarge amount of electric power, has been turned on, the idle speed is increased further by a predetermined amount (second idle increase). In contrast, at step 32, abnormality (failure) of the auxiliary power source 3 is reported, i.e., is
       warned to thedriver
     * Ligne n°588 : According to the second embodiment, when the output capability of the DC/DC converter 4 is equal to or below the overall load value, the switch 6 is switched on, and the second supply circuit 7 is used. In this way, it is possible to supplyelectric power from the generator 1 or the auxiliary power source 3 to the main power source 2 even at the time of shortage of the supply of electric power from the DC/DC converter 4 or at the time of failure of the DC/DC converter 4.
     * Ligne n°590 : When the temperature of the DC/DC converter 4 has become higher than the fixed value, the supply capability of the DC/DC converter 4 is limited, or the switch 6 is switched on, and only the second supply circuit 7 is used. In this way, theheat-induced failure of the DC/DC converter 4 can be limited. Thus, as discussed above, the second supply circuit 7, which has the switch 6, is provided between the auxiliary power source 3 and the main power source 2 in parallel with the first supplycircuit 5, which has the DC/DC converter 4. In this way, it is possible to reduce the capacity and the size of the DC/DC converter 4.
     * Ligne n°592 : Also, as discussed with reference to step 27, even in the fully charged state of the auxiliary power source 3, the power generation level (Lo) of the generator 1 is kept to a level which enables the supply of electric power in the amount thatcorresponds to the ordinary loads 8b. In this way, the power is supplied from the generator 1 to the ordinary loads 8b instead of charging the auxiliary power source 3 during the deceleration of the vehicle. For example, on a long downward slope, evenafter the amount of regenerative electric power is stored in the auxiliary power source 3 (the fully charged state), the regenerative electric power is consumed by the ordinary loads 8b. Thus, the regenerative electric power can be used effectively.
     * Ligne n°594 : The control operation of the second embodiment can be used irrespective of which of the main power source 2 and the auxiliary power source 3 has the higher output voltage (nominal voltage). That is, it can be used in the case where the outputvoltage (nominal voltage) of the main power source 2 is higher than that of the auxiliary power source 3, or in the case where the output voltage (nominal voltage) of the auxiliary power source 3 is higher than that of the main power source 2.
     * Ligne n°598 : Next, as a third embodiment, a control operation of the generator 1 will be described with reference to a flowchart shown in FIG. 5. In this method, the control operation is carried out based on the power source voltages only without using asensing means of a State of Charge (SOC).
     * Ligne n°600 : At step 40, it is determined whether the output voltage V1 of the auxiliary power source 3 is equal to or above a fixed value (e.g., 12 V). When the determination result is YES, control proceeds to step 44. In contrast, when the determinationresult is NO, control proceeds to step 42. At step 44, it is determined whether the vehicle is decelerating. When the determination result at step 44 is NO, control proceeds to step 41. At step 41, since there is the surplus in the charge capacity ofthe auxiliary power source 3, power generation by the generator 1 is cut off, and electric power is supplied from the auxiliary power source 3 to the main power source 2 through the first supply circuit 5 (the DC/DC converter 4) (first control state).
     * Ligne n°602 : At step 42, it is determined whether the vehicle is decelerating. When the determination result is YES, control proceeds to step 43. In contrast, when the determination result is NO, control proceeds to step 46. At step 43, regenerativeelectric power, which is generated by the generator 1, is recovered into the auxiliary power source 3, and electric power is also supplied to the main power source 2 through the first supply circuit 5 (first control state).
     * Ligne n°604 : Returning to step 44, when the determination result is YES, control proceeds to step 45. At step 45, since the output voltage V1 of the auxiliary power source 3 is larger than the fixed value although the vehicle is in the decelerating state,regenerative electric power (Lo level), which is generated by the generator 1, is supplied to the main power source 2 through the first supply circuit 5 and the second supply circuit 7 (shown as a switch in the figure) (third control state). Alternatively, electric power is supplied to the main power source 2 through one the first supply circuit 5 and the second supply circuit 7. In this way, power supply, which corresponds to the ordinary loads 8b, is effected even in the fully chargedstate of the auxiliary power source 3, and it is possible to realize regeneration on deceleration by supplying power to the ordinary loads 8b instead of by charging.
     * Ligne n°606 : At step 46, it is determined whether the vehicle is in the steady traveling state or in the accelerating state, and furthermore, whether the output voltage V2 of the DC/DC converter 4 is within a predetermined range (e.g., between 12.5 V and 13V). When the determination result is YES, control proceeds to step 47. In contrast, when the determination result is NO, control proceeds to step 48. At step 47, the supply capability of the DC/DC converter 4 is increased, and electric power issupplied from the generator 1 to the main power source 2 through the first supply circuit 5 (first control state). This corresponds to the state where the charge level of the main power source 2 is reduced, and the output instruction to the DC/DCconverter 4 is insufficient. Thus, in such a case, to counteract against this situation, the output of the DC/DC converter 4 is increased, and the charge level of the main power source 2 is kept to a relatively high level, so that
       deterioration of themain power
     * Ligne n°607 : source 2 caused by electrical discharge is limited.
     * Ligne n°609 : At step 48, it is determined whether the temperature of the DC/DC converter 4 is greater than a fixed value, or whether the output voltage V1 of the auxiliary power source 3 is within a predetermined range (e.g., between 11 V and 12 V). When thedetermination result is YES, control proceeds to step 49. In contrast, when the determination result is NO, control proceeds to step 50. At step 49, the generator 1 is controlled to always generate electric power (Lo level), and electric power issupplied from the generator 1 to the main power source 2 through the second supply circuit 7 (second control state). This is performed to limit temperature increase of the DC/DC converter 4.
     * Ligne n°611 : At step 50, it is determined whether the output voltage V1 of the auxiliary power source 3 is smaller than a fixed value (e.g., 11 V), and furthermore the output voltage V2 of the DC/DC converter 4 is within a predetermined range (e.g., between12 V and 12.5 V). When the determination result is YES, control proceeds to step 51. In contrast, when the determination result is NO, control proceeds to step 52. At step 51, the first idle increase is carried out to increase the idle speed, and thesupply of power to the ordinary loads 8b is cut off (or limited) since the charge capacity of the auxiliary power source 3 is low, and the output voltage V2 of the DC/DC converter 4 is also low even though the generator 1 is generating (at the Lo level). Furthermore, when the high load, which is among the ordinary loads 8b and which consumes a large amount of electric power, is turned on, the second idle increase is carried out to raise the idle speed further. Here, since the
       generated power
     * Ligne n°614 : According to the third embodiment, the output of the generator 1 can be effectively controlled according to the output voltage V1 of the auxiliary power source 3 and the output voltage V2 of the DC/DC converter 4.
     * Ligne n°616 : Furthermore, since the generator 1 is connected to the high-performance auxiliary power source 3, the charge acceptance of which is higher than that of the main power source 2 and which allows easy detection of its operational state with highaccuracy, it is possible to recover regenerative electric power generated by the generator 1 to the auxiliary power source 3 with good efficiency during the deceleration of the vehicle. That is, in order to recover a large amount of regenerative energyin the short time of deceleration, it is important to have a relatively large difference between the voltage of the generator 1 and the voltage of the power source (e.g., the voltage of the auxiliary power source 3).
     * Ligne n°618 : However, in the case (e.g., the case of the main power source 2, the charge acceptance of which is lower than that of the auxiliary power source 3) where the difference between the voltage of the generator 1 and the voltage of the power source isrelatively small, and the internal resistance of the power source is relatively large, the power source 2 is not charged to an acceptable SOC within a predetermined deceleration time A, as shown in FIG. 6(b). In such a case, the power source cannot becharged sufficiently. Furthermore, when the difference between the voltage of the generator 1 and the voltage of the power source becomes excessively large, overshooting beyond the acceptable SOC occurs, as shown in FIG. 6(c). In such a situation, inthe high performance battery, such as the auxiliary power source 3 (Li ion battery), heat production becomes large, and performance may be deteriorated due to increased internal resistance and so on.
     * Ligne n°620 : In contrast, in the power supply system S, since the output voltage of the auxiliary power source 3, which recovers regenerative electric power during the deceleration of the vehicle, is smaller than that of the main power source 2 and theinternal resistance of the auxiliary power source 3 is also small, the charge acceptance capability of the auxiliary power source 3 is good. Thus, as shown in FIG. 6(a), it is possible to recover a large amount of regenerative energy in thepredetermined deceleration time A. As a result, it is possible to carry out maximum regenerative charging from the generator 1 to the auxiliary power source 3 within a short time of deceleration. Also, through the cutting of the power generation of thegenerator 1 in the steady traveling state or in the accelerating state, the load on the engine is reduced, thereby contributing to a reduction in the fuel consumption.
     * Ligne n°622 : In the third embodiment, there is described the case where the output voltage (nominal voltage) of the auxiliary power source 3 is lower than that of the main power source 2. However, the same control operation can also be applied to a casewhere the auxiliary power source 3 has a higher output voltage (nominal voltage) over the main power source 2. However, since the output voltage of the auxiliary power source 3 becomes higher, the voltage determination values of the respective steps(S40, S42, S44, S48, S50 in FIG. 5) used in the determination of the output voltage V1 of the auxiliary power source 3 need to be changed accordingly. For example, the voltage determination values, which are used in the case where the output voltage(nominal voltage) of the auxiliary power source 3 is set to be 14.4 V, are shown in the flowchart of FIG. 7 (S40a, S42a, S44a, S48a, S50a).
     * Ligne n°626 : Next, as a fourth embodiment, a control operation in a case where the output voltage of the auxiliary power source 3 is higher than that of the main power source 2, will be described with reference to a flowchart shown in FIG. 8.
     * Ligne n°628 : At step 60, it is determined whether the output voltage of the auxiliary power source 3 is higher than that of the main power source 2. When the determination result is NO (i.e. auxiliary power source voltage.ltoreq.main power source voltage),control proceeds to step 61. In contrast, when the determination result is YES, control proceeds to step 62. At step 61, power generation is carried out by the generator 1, and the auxiliary power source 3 is charged. This process is continued untilthe output voltage of the auxiliary power source 3 becomes higher than that of the main power source 2.
     * Ligne n°630 : At step 62, it is determined whether the level of electric power, which is supplied from the auxiliary power source 3 to the main power source 2 and the ordinary loads 8b, is above a predetermined value. When the determination result is NO,control proceeds to step 63. In contrast, when the determination result is YES, control proceeds, to step 64. At step 63, the first control state is selected. That is, the DC/DC converter 4 is driven (ON), and the switch 6 is opened (OFF). Thus, therequired power is supplied from the auxiliary power source 3 to the main power source 2 and the ordinary loads 8b through the first supply circuit 5. In this control operation, for example, the voltage of the output side of the DC/DC converter 4 iscontrolled to have a fixed value. After that, control proceeds to step 65. In contrast, at step 64, the large amount of electric power needs to be supplied, so that the electric power is supplied at the maximum output of the DC/DC
       converter 4 (shortageof the
     * Ligne n°631 : electric power being compensated through discharge from the main power source 2).
     * Ligne n°633 : At step 65, it is determined whether the output voltage of the auxiliary power source 3 is equal to or below the acceptable rated voltage of the ordinary loads 8b. When the determination result is YES, control proceeds to step 66. In contrast,when the determination result is NO, control returns to step 62. At step 66, the second control state is selected. That is, the DC/DC converter 4 is stopped (OFF), and the switch 6 is closed (ON). Thus, the electric power is supplied from theauxiliary power source 3 to the main power source 2 and the ordinary loads 8b through the second supply circuit 7.
     * Ligne n°635 : According to the control operation of the fourth embodiment, an excessive voltage is not applied to the ordinary loads 8b, such as the lights, and therefore a reduction in the lifetime of the ordinary loads 8b can be limited. Furthermore, in thecase where the output voltage of the auxiliary power source 3 has fallen to or below the acceptable rated voltage of the ordinary loads 8b, the path is shifted from the DC/DC converter 4 to the switch 6. Therefore, a loss associated with the DC/DCconverter is eliminated, and thereby effective power supply can be implemented.
     * Ligne n°641 : At step 70, a switch command for switching the control state is issued. Specifically, switch command is a command for switching from the first control state to the second control state or a command for switching from the second control state tothe first control state. At step 71, it is determined whether the voltage difference between the main power source 2 and the auxiliary power source 3 is greater than a predetermined value. When the determination result is YES, control proceeds to step72. In contrast, when the determination result is NO, control jumps to step 73.
     * Ligne n°643 : At step 72, the ECU 17 (serving as a first control means) controls the output voltage of the DC/DC converter 4. More specifically, at step 72, the output voltage of the DC/DC converter 4 is increased to a higher one of the voltage of the mainpower source 2 and the voltage of the auxiliary power source 3 or is decreased to a lower one of the voltage of the main power source 2 and the voltage of the auxiliary power source 3. Thereafter, control returns to step 71. At step 73, the secondcontrol state (or the first control state) is selected since the voltage difference between the main power source 2 and the auxiliary power source 3 is smaller than the predetermined value.
     * Ligne n°659 : FIG. 11 is an electrical circuit diagram of a power supply system S according to a seventh embodiment. In the power supply system S of the seventh embodiment, as shown in FIG. 11, an auxiliary power source switch 19 (e.g., a relay switch) isconnected to the anode side of the auxiliary power source 3, and the auxiliary power source switch 19 is controlled by the system ECU 17.
     * Ligne n°661 : With this construction, for example, when the auxiliary power source 3 fails, the auxiliary power source switch 19 is switched off at the time of evacuating the vehicle to a safe place or at the time of driving the vehicle to an automobiledealer. Thus, the auxiliary power source 3 is electrically isolated from the power system S. As a result, the safety of the power supply system S is ensured.
     * Ligne n°663 : In the case where electrical loads, which consume a relatively large amount of electric power among ordinary loads 8b, are operated, the auxiliary power source switch 19 may be switched off to reliably supply the electric power from the generator1 to the main power source 2 and the ordinary loads 8b. This is true even when the electric power is supplied from the generator 1 through the first supply circuit 5 or through the second supply circuit 7 or through both the first and second supplycircuits 5, 7.
     * Ligne n°665 : Also, in a case where the vehicle is equipped with an idle stop device, which automatically stops the engine when the vehicle has stopped, for example, at a red traffic light at an intersection, the auxiliary power switch 19 may be turned off atthe time of stopping the engine, for example, at the red traffic light to effectively enable the next engine start (restarting after the automatic stop). By turning off the auxiliary power source switch 19, the required electrical capacity that isrequired for the restarting of the engine can be ensured at the time of restarting the engine.
     * Ligne n°667 : Also, when rapid charging is carried out on the deceleration of the vehicle in the state where the 100% capacity voltage of the auxiliary power source 3 is smaller than the output voltage of the generator 1, the auxiliary power source switch 19may be turned off. In this way, in a case of encountering a failure, such as control failure of the power generation, the excessive charging of the auxiliary power source 3 can be cut by turning off the auxiliary power switch 19.
     * Ligne n°669 : The auxiliary power source switch 19 may be alternatively connected to the cathode side of the auxiliary power source 3, as shown in FIG. 12 or FIG. 13. In the example shown in FIG. 13, the auxiliary power source switch 19 is disposed betweenthe generator 1 and the auxiliary power source 3 on the generator 1 side of the input side connection point B of the DC/DC converter 4.
     * Ligne n°673 : FIG. 14 is an electrical circuit diagram of a power supply system S according to an eighth embodiment. In the power supply system S of the eighth embodiment, as shown in FIG. 14, a capacitor 20 is connected to the output side (the main powersource 2 side) of the DC/DC converter 4 of the first supply circuit 5. When a relatively large power is supplied from the DC/DC converter 4 to the main power source 2, the capacitor 20 smoothes the voltage. In this way, it is possible to supply a morestable voltage to the main power source 2 through the DC/DC converter 4.
     * Ligne n°677 : FIG. 15 is an electrical circuit diagram of a power supply system S according to a ninth embodiment. In the power supply system S of the ninth embodiment, as shown in FIG. 15, the charge acceptance capability of the main power source 2 is sensedby monitoring the output voltage of the main power source 2 with a voltmeter 21 or the like. In this way, detecting the charge acceptance capability of the main power source 2 with a sensor (e.g., a sensor for sensing the current, the voltage, or thetemperature), so a low-cost system can be realized.
     * Ligne n°681 : FIG. 16 is an electrical circuit diagram of a power supply system S according to a tenth embodiment. In the power supply system S of the tenth embodiment, as shown in FIG. 16, electrical loads 22 (e.g., a defogger, a seat heater), which toleratevoltage fluctuations and do not require a dark current, are connected to the auxiliary power source 3 and the generator 1 through a relay 23 rather than connecting to the main power source 2. The electrical load, which does not require the dark current,may be one of an electrical load, such as an ECU that does not have an internal memory, and an electrical load, such as an ECU that always uses an initial constant of an internal memory. A controller 24 (an ECU), which opens and closes the relay 23, isconnected to the main power source 2 and receives a power supply from the main power source 2.
     * Ligne n°683 : In this way, the power source (the dark current) only to the resettable loads (i.e., loads that can be properly reset even upon a power interruption) can be cut to limit complete discharging of the battery 2, which occurs, for example, over atime during which the vehicle is parked for an extended period (e.g., weeks, months or years), or over a time of unintentionally leaving the vehicle door open to cause the lamp in the vehicle to be turned and left on for hours or days. Thereby, thedeterioration of the lifetime of the main power source 2 and the deterioration of the performance of the main power source 2 can be limited. Furthermore, the electrical loads 22, which do not require the dark current, can receive electric power from theauxiliary power source 3 or the generator 1. The means for cutting off the dark current (dark current blocking means of the present invention) may include the following, i.e., a) a means having a timer function for cutting off a dark
       current after
     * Ligne n°684 : fixedtime; b) a means for sensing the capacity of the auxiliary power source 3; c) a means for receiving an external communication signal; d) a means for sensing termination of signal transmission or signal reception at a radio transmitter; and e) a switch,such as a touch panel switch at an exterior of the vehicle.
     * Ligne n°688 : FIG. 17 is an electrical circuit diagram of a power supply system S according to an eleventh embodiment. In the power supply system S of the eleventh embodiment, a bypass circuit 25, which is connected to the fourth supply circuit 12 whilebypassing the auxiliary power source switch 19, is provided to the circuit of FIG. 13, which includes the auxiliary power switch 19.
     * Ligne n°690 : In this way, even in the case where the auxiliary power source switch 19 is turned off, electric power can be supplied from the main power source 2 or the auxiliary power source 3 to the safety ECU 16. Thus, the redundant system is provided tothe safety ECU 16, which is involved in the travel safety.
     * Ligne n°698 : In the first embodiment, the two power sources (the main power source 2 and the auxiliary power source 3), which are used in the power supply system S of the first aspect of the present application, are described such that the nominal voltage (orthe nominal capacity) of the main power source 2 is higher than that of the auxiliary power source 3. However, alternative to this construction, the nominal voltage (or the nominal capacity) of the auxiliary power source 3 may be higher than that of themain power source 2. Further alternatively, the main power source 2 and the auxiliary power source 3 may have a common operational range, in which a working voltage of the main power source 2 coincides with a working voltage of the auxiliary powersource 3.
     * Ligne n°700 : In the first embodiment, the Pb battery and the Li ion battery are described as examples of the main power source 2 and the auxiliary power source 3, respectively. However, the present invention is not limited to this. For example, besides thePb battery, the main power source 2 may be a Li ion battery or a Ni hydrogen battery. Also, besides the Li ion battery, the auxiliary power source 3 may be a Pb battery, a Ni hydrogen battery or an electrical double-layer capacitor.
     * Ligne n°788 : Furthermore, one of or both of the main battery 105 and the sub-battery 106 is used as the power source of the starter 107 based on the engine temperature. Thus, the batteries 105, 106 can be effectively used according to the characteristics ofthe batteries.
     * Ligne n°863 : The charging circuit 207 is provided with a MOSFET 207a, which serves as an ON-OFF means. Turning on and off of the MOSFET 207a is controlled at a certain time rate by a power source monitor ECU 210. A relay 208a, which serves as an ON-OFFswitch, is arranged in the assist circuit 208. At the time of performing the power assistance from the first battery 202, the relay 208a is turned on by the power source monitor ECU 210.
     * Ligne n°865 : The distributor 209 includes a DC/DC converter 209a and a diode 209b. The DC/DC converter 209a is provided between the first battery 202 and the important loads 205. The diode 209b is provided between the second battery 203 and the importantloads 205. The DC/DC converter 209a is controlled by the power source monitor ECU 210. Particularly, at the time of stopping the engine, operation of the DC/DC converter 209a is stopped by the power source monitor ECU 210 to limit flow of a darkcurrent from the first battery 202 to the important loads 205. Thus, at the time of stopping the engine, the dark current is provided to the important loads from the second battery 203.
     * Ligne n°867 : The power source monitor ECU 210 monitors the voltage across the terminals of the first battery 202 and the voltage across the terminals of the second battery 203. Based on the charge state of the first battery 202 and the charge state of thesecond battery 203, the power source monitor ECU 210 controls the MOSFET 207a, the relay 208a and the DC/DC converter 209a.
     * Ligne n°869 : A control procedure (shown in the flowchart of FIG. 28) at the time of starting the engine through use of the power source monitor ECU 210 is the same as that of the fifteenth embodiment, and thus will not be described here for the sake ofsimplicity.
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