JP2011130641A - Power supply device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device for vehicles that can be reduced in heat loss when feeding power from an auxiliary power supply. <P>SOLUTION: The power supply device for vehicles includes a capacitor 10 that is charged by an onboard generator 1 or a battery 4 and is configured such that an onboard load group 14-17 may be fed with power from the onboard generator 1, the battery 4, or the capacitor 10. The power supply device for vehicles includes a first switch circuit SW1 connected between the battery 4 and the onboard load group 14-17, a second switch circuit SW2 connected between the capacitor 10 and the onboard load group 14-17, a comparator (9) for comparing the output voltage values of the battery 4 and the capacitor 10, and a switcher 9 that switches the first switch circuit SW1 on and the second switch circuit SW2 off when the comparison results of the comparator indicates that the output voltage value of the battery 4 is higher, and switches the first switch circuit SW1 off and the second switch circuit SW2 on when the output voltage value of the capacitor 10 is higher. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention includes an on-vehicle generator or an accumulator as an auxiliary power source that is charged by a battery, and is configured to supply power to an on-vehicle load group by the on-vehicle generator, battery, or accumulator, and particularly when idling. The present invention relates to a vehicle power supply device that is preferably used in an idle stop vehicle that stops an engine.

In recent years, in order to improve fuel consumption and from environmental considerations, vehicles that perform idle stop that stops idling when the vehicle is stopped are increasing. In such a vehicle, since the engine is started more frequently than in the conventional vehicle, the power source of the starter for starting the engine is important. When starting the engine, since the starter consumes a large current, the voltage of the vehicle power supply device temporarily decreases. When the voltage is temporarily lowered, the voltage of an electric load such as a navigation device and an ECU (Electronic Control Unit) is also lowered, and there is a possibility that the operation becomes unstable.
Therefore, it is considered that a backup battery or an electric double layer capacitor is connected in parallel as an auxiliary power source to the battery (main power source) and the starter is assisted by discharging from the auxiliary power source.

  For example, in Patent Document 1, a backup battery (auxiliary power supply) is mounted separately from the main battery (main power supply), and the voltage drop of the diode is reduced when the power supply system of the main power supply fails (when the main power supply voltage is low). A power feeding circuit for a vehicle that uses and switches to power feeding from an auxiliary power source is disclosed.

JP 2004-282844 A

However, as described above, when the power supply is switched from the auxiliary power supply using the voltage drop of the diode when the main power supply voltage is low, the diode voltage drop (about 0.6V) is consumed as heat and lost. Therefore, there is a problem that a countermeasure for heat generation becomes complicated as the load current increases.
In addition, a battery and an electric double layer capacitor used as an auxiliary power source have a problem that a life is shortened when an applied voltage (charging voltage) is increased.

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a vehicle power supply device that can reduce heat loss when power is supplied from an auxiliary power supply.
Another object of the present invention is to provide a vehicular power supply device that can reduce heat loss during power feeding from an auxiliary power source and can maintain a proper charging voltage during charging of the auxiliary power source.

  A vehicular power supply device according to a first aspect of the present invention is a vehicular power supply device that includes an accumulator charged by an in-vehicle generator or a battery, and is configured to supply power to the in-vehicle load group by the in-vehicle generator, battery, or accumulator. A first switch circuit connected between the battery and the vehicle load group, a second switch circuit connected between the battery and the vehicle load group, means for comparing output voltages of the battery and the capacitor, Means for switching the first switch circuit on (off) and the second switch circuit off (on) when the comparison result of the means is higher in the battery (capacitor). To do.

  In this vehicle power supply device, the capacitor is charged by the on-vehicle generator or battery, and power is supplied to the on-vehicle load group by the on-vehicle generator, battery, or capacitor. The first switch circuit is connected between the battery and the vehicle load group, and the second switch circuit is connected between the capacitor and the vehicle load group. The means for comparing compares the output voltage values of the battery and the battery, and when the comparison result is higher for the battery (capacitor), the means for switching turns the first switch circuit on (off) and the second switch Switch the circuit off (on).

  According to a second aspect of the present invention, each of the first switch circuit and the second switch circuit includes a P-channel MOS FET, and the FET has a drain on the battery or capacitor side and a source on the load group. It is connected to the side.

  In this vehicle power supply device, each of the first switch circuit and the second switch circuit is provided with a P-channel MOS type FET, and these FETs have their drains on the battery or capacitor side opposite to the normal connection direction. In addition, the source is connected to the load group side.

  The vehicular power supply device according to a third aspect of the present invention further includes a charging voltage control circuit that controls a charging voltage value of the capacitor, the charging voltage control circuit including a first resistor connected between the battery and the capacitor, 2 resistors and a third switch circuit are connected in series, and have a series circuit connected in parallel to the capacitor, and means for comparing the charging voltage value and the predetermined voltage value, and the means has a higher charging voltage value. When it is determined that the voltage is high, the third switch circuit is configured to be turned off.

  In this vehicle power supply device, the charging voltage control circuit controls the charging voltage value of the battery. In the charging voltage control circuit, a first resistor is connected between the battery and the capacitor, and a series circuit in which a second resistor and a third switch circuit are connected in series is connected in parallel to the capacitor. When the comparing means compares the charge voltage value with the predetermined voltage value and determines that the charge voltage value is higher, the third switch circuit is turned off.

  A vehicle power supply device according to a fourth aspect of the present invention further includes a charging voltage control circuit that controls a charging voltage value of the battery, the charging voltage control circuit including a first resistor connected between the battery and the battery, 3 resistors and a current amplifying circuit are connected in series, and have a second series circuit connected in parallel to the battery, and means for detecting the charging voltage value, according to the level of the charging voltage value detected by the means The amplification factor of the current amplifier circuit is configured to increase or decrease.

  In this vehicle power supply device, the charging voltage control circuit controls the charging voltage value of the battery. In the charging voltage control circuit, a first resistor is connected between the battery and the capacitor, and a second series circuit in which a third resistor and a current amplifier circuit are connected in series is connected in parallel to the capacitor. The detecting means detects the charging voltage value, and increases or decreases the amplification factor of the current amplifying circuit according to the detected charging voltage value.

  A vehicular power supply device according to a fifth aspect of the present invention further includes a charging voltage control circuit that controls a charging voltage value of the battery, the charging voltage control circuit including a first resistor connected between the battery and the battery, A fourth switch circuit connected between the first resistor and the capacitor, and means for comparing the charging voltage value and the predetermined voltage value, and when the means determines that the charging voltage value is higher, The fourth switch circuit is configured to be turned off.

  In this vehicle power supply device, the charging voltage control circuit controls the charging voltage value of the battery. In the charging voltage control circuit, the first resistor is connected between the battery and the capacitor, and the fourth switch circuit is connected between the first resistor and the capacitor. When the comparing means compares the charge voltage value with the predetermined voltage value and determines that the charge voltage value is higher, the fourth switch circuit is turned off.

  According to the vehicle power supply device according to the first and second aspects of the invention, it is possible to realize a vehicle power supply device that can reduce heat loss when power is supplied from the auxiliary power supply.

  According to the vehicular power supply apparatus according to the third to fifth inventions, a vehicular power supply apparatus that can reduce heat loss at the time of power feeding from the auxiliary power supply and can maintain the charging voltage appropriately at the time of charging the auxiliary power supply is realized. be able to.

It is a block diagram which shows schematic structure of embodiment of the vehicle power supply device which concerns on this invention. It is a block diagram which shows the structural example of the auxiliary power supply module shown in FIG. 1 in detail. FIG. 3 is a block diagram illustrating in detail a configuration example of a switch control circuit and a switch circuit illustrated in FIG. 2. It is a block diagram which shows in detail the example of a structure of the auxiliary power module with which embodiment of the vehicle power supply device which concerns on this invention is provided. FIG. 5 is a circuit diagram showing in detail a configuration example of a control circuit and a current amplifier circuit shown in FIG. 4. FIG. 5 is a characteristic diagram illustrating characteristics of an output voltage of a charging control circuit including a control circuit and a current amplifier circuit illustrated in FIG. 4 and a charging voltage of an auxiliary power source. It is a block diagram which shows in detail the example of a structure of the auxiliary power module with which embodiment of the vehicle power supply device which concerns on this invention is provided. FIG. 8 is a circuit diagram illustrating in detail a configuration example of a switch control circuit and a switch circuit illustrated in FIG. 7.

Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of a vehicle power supply device according to the present invention.
In this vehicle power supply device, an alternator (on-vehicle generator, AC generator) 1 generates power in conjunction with an engine (not shown). The generated electric power is converted into direct current in the alternator 1 and mounted on the battery (main power supply, lead storage battery) 4 and the vehicle via the fuse in the electrical connection box 3, the accessory switch 6, the ignition switch 7, and the like. Given to the load group. Further, the generated and converted electric power is given to other load groups only through the fuse in the electric junction box 3.

An electric wire from the battery 4 (alternator 1) via the fuse and not via the switches is connected to the charging control circuit 8. Further, another electric wire from the battery 4 (alternator 1) via the fuse and not via the switches is connected to one terminal of the idle stop ECU 12, and a signal line from the other terminal is connected to the charging control circuit 8. ing.
Each on / off information of the accessory switch 6 and the ignition switch 7 is given to the charging control circuit 8 via each signal line. The charge control circuit 8 supplies the given on / off information of the ignition switch 7 to the idle stop ECU 12 via a signal line. The idle stop ECU 12 stops the engine when detecting idling of the engine.
An electric wire that does not pass through the fuse from the battery 4 is connected to the starter 2.

Connected to the charging control circuit 8 are an electric wire 28 to which the output voltage of the battery 4 (alternator 1) is applied and an electric wire 29 to which the output voltage (charging voltage) of the auxiliary power supply 10 is applied. The electric wire 29 is given the output voltage of the battery 4 (alternator 1) via the backflow prevention circuit in the charge control circuit 8.
The electric wire 28 is connected to the output switching circuit 11 through the switch circuit SW1, the electric wire 29 is connected to the output switching circuit 11 through the switch circuit SW2, and both the electric wires 28 and 29 are connected to the same terminal of the output switching circuit 11. Yes.
The auxiliary power supply 10 includes, for example, a plurality of electric double layer capacitors.

The switching circuit 9 connected to the electric wires 28 and 29 respectively controls the switch circuits SW1 and SW2 on / off.
The output switching circuit 11 has a fuse function and a disconnection detection function, and each ON / OFF information of the accessory switch 6 and the ignition switch 7 is given via a signal line (not shown), and the battery 4, the alternator 1 or the auxiliary power source 10 Output the output voltage. The output switching circuit 11 includes an output terminal whose output voltage is turned on / off according to the on / off state of the accessory switch 6, an output terminal whose output voltage is turned on / off according to the on / off state of the ignition switch 7, and switches. There is provided an output terminal whose output voltage is turned on regardless of the above. Each output terminal is connected to any one of ECUA14, ECUB15, ECUC16, and ECUD17 (vehicle load group).

The charge control circuit 8, the auxiliary power supply 10, the electric wires 28 and 29, the switching circuit 9, the switch circuits SW <b> 1 and SW <b> 2, and the output switching circuit 11 constitute an auxiliary power supply module 13.
In the vehicular power supply apparatus having such a configuration, the switching circuit 9 compares the applied voltages of the electric wires 28 and 29, and when the applied voltage of the electric wire 28 is higher, the switch circuit SW1 is turned on and the switch circuit SW2 is turned on. When the applied voltage of the electric wire 29 is higher, the switch circuit SW1 is turned off and the switch circuit SW2 is turned on.

FIG. 2 is a block diagram showing in detail a configuration example of the auxiliary power supply module 13 shown in FIG.
In the auxiliary power supply module 13, a voltage obtained by dividing the applied voltage of the electric wire 28 by the voltage dividing circuit 22 is given to the non-inverting input terminal of the operational amplifier 21 via the resistor R 6, and the applied voltage of the electric wire 29 is changed to the voltage dividing circuit 23. The voltage divided by is applied to the inverting input terminal of the operational amplifier 21 via the resistor R5. The operational amplifier 21 is subjected to positive feedback to constitute a comparison circuit.

The output terminal of the operational amplifier 21 (comparison circuit) is connected to the gate of the N-channel MOS type FET 20a. The source of the FET (field effect transistor) 20a is grounded, and the drain is connected to the gate of the N-channel MOS type FET 20b and the gate of the P-channel MOS type FET 18 through the resistor R2.
The drain of the FET 18 is connected to the charge control circuit 8 by an electric wire 28, and the source is connected to the output switching circuit 11. A resistor R1 is connected between the gate and source of the FET 18.
The charging voltage from the charging control circuit 8 is given to the auxiliary power source 10 by the electric wire 29 via the resistor R7.

The source of the FET 20b is grounded, and the drain is connected to the gate of the P-channel MOS type FET 19 through the resistor R4.
The drain of the FET 19 is connected to the charge control circuit 8 through the resistor R7 by the electric wire 29, and the source is commonly connected to the source of the FET 18 and the output switching circuit 11. A resistor R3 is connected between the gate and source of the FET 19.
A switch control circuit 24 is connected in parallel to the auxiliary power source 10, and a series circuit of a resistor R 8 and a switch circuit SW 3 is connected in parallel to the auxiliary power source 10. The switch control circuit 24 performs on / off control of the switch circuit SW3.
The sources and drains of the FETs 18 and 19 are connected so as to be opposite to the normal directions.

In the auxiliary power supply module 13 having such a configuration, when the electric wire 28 is higher among the applied voltages of the electric wires 28 and 29, the output of the operational amplifier 21 becomes H level and the FET 20a is turned on. When the FET 20a is turned on, the FET 18 is turned on with the gate at the L level. On the other hand, the FET 20b is turned off, and the FET 19 is turned off with the gate at the H level. Thereby, the applied voltage of the electric wire 28 is given to the output switching circuit 11.
When the electric wire 29 is higher among the applied voltages of the electric wires 28 and 29, the output of the operational amplifier 21 becomes 0 (L level, ground potential), and the FET 20a is turned off. When the FET 20a is turned off, the FET 18 is turned off with the gate at the H level. On the other hand, the FET 20b is turned on, and the FET 19 is turned on with the gate at the L level. Thereby, the applied voltage of the electric wire 29 is given to the output switching circuit 11.

When FETs 18 and 19 are connected as usual with the source on the power supply side and the drain on the load side as usual, both FETs 18 and 19 are turned off when the output on the main power supply side (Vb) / auxiliary power supply side (Vc) is switched. At the moment, the power supply becomes impossible.
Therefore, by connecting the drains and sources of the FETs 18 and 19 in the opposite direction, power is supplied through the respective parasitic diodes even when the FETs 18 and 19 are turned off.
If one of the FETs 18 and 19 is turned on, the current flows in accordance with the resistance ratio (several mΩ (parasitic diode): 0), so that the current flowing in the other parasitic diode is negligible. On the other side, since the source has a higher voltage than the diode, no current flows through the parasitic diode.

  The switch control circuit 24 compares the charging voltage (output voltage) of the auxiliary power supply 10 with a predetermined voltage, and turns on the switching circuit SW3 when the charging voltage is higher than the predetermined voltage. Thereby, a current flows through the resistor R8, and the charging voltage of the auxiliary power supply 10 is maintained at a predetermined voltage or lower.

FIG. 3 is a block diagram showing in detail a configuration example of the switch control circuit 24 and the switch circuit SW3 shown in FIG.
In the switch control circuit 24 and the switch circuit SW3, the voltage obtained by dividing the applied voltage of the electric wire 29 by the voltage dividing circuit 30 is given to the inverting input terminal of the operational amplifier 32 via the resistor R13, and the reference voltage Vref is divided by the voltage dividing circuit. The voltage divided by 31 is applied to the non-inverting input terminal of the operational amplifier 32 via the resistor R12. The operational amplifier 32 is subjected to positive feedback to constitute a comparison circuit.

  The output terminal of the operational amplifier 32 (comparison circuit) is pulled up to the reference voltage Vref through the resistor R19, and is connected to the base of the NPN transistor Tr1 through the resistor R11. The emitter of the transistor Tr1 is grounded, and the collector is supplied with the voltage via the ignition switch 7 through the resistor R14, and is connected to the base of the NPN transistor Tr2. The emitter of the transistor Tr2 is grounded, and the collector is connected to the electric wire 29 through the resistor R8.

In the switch control circuit 24 and the switch circuit SW3 having such a configuration, when the divided voltage of the charging voltage of the auxiliary power supply 10 applied to the electric wire 29 is higher than a predetermined voltage obtained by dividing the reference voltage Vref, the output of the operational amplifier 32 is output. Becomes 0 (L level, ground potential), and the transistor Tr1 is turned off. As a result, if the ignition switch 7 is on, the transistor Tr2 is turned on. Thereby, a current flows through the resistor R8, and the charging voltage of the auxiliary power supply 10 is maintained at a predetermined voltage or lower.
When the predetermined voltage obtained by dividing the reference voltage Vref is higher, the output of the operational amplifier 32 becomes H level and the transistor Tr1 is turned on. As a result, the transistor Tr2 is turned off.

(Embodiment 2)
FIG. 4 is a block diagram showing in detail a configuration example of an auxiliary power supply module included in the second embodiment of the vehicle power supply device according to the present invention. Since the schematic configuration of the second embodiment of the vehicle power supply device according to the present invention is the same as the schematic configuration (FIG. 1) described in the first embodiment, the description thereof is omitted.
In this auxiliary power supply module, a control circuit 25 is connected in parallel to the auxiliary power supply 10, and a series circuit in which a resistor R 9 and a current amplification circuit 26 are connected in series is connected in parallel to the auxiliary power supply 10. The control circuit 25 controls increase / decrease of the current amplification factor of the current amplifier circuit 26. The other configuration example of the auxiliary power supply module is the same as the configuration example (FIG. 2) of the auxiliary power supply module 13 described in the first embodiment, and thus the description thereof is omitted.

  In the auxiliary power supply module having such a configuration, the control circuit 25 detects the applied voltage of the electric wire 29 and controls the current amplification factor of the current amplifier circuit 26 to be high or low according to the detected applied voltage level. The other operations of this auxiliary power supply module are the same as the operations of the auxiliary power supply module 13 described in the first embodiment, and a description thereof will be omitted.

FIG. 5 is a circuit diagram showing in detail a configuration example of the control circuit 25 and the current amplifier circuit 26 shown in FIG.
In the control circuit 25 and the current amplifying circuit 26, the charging voltage (output voltage) Vc of the auxiliary power supply 10 is divided by a voltage dividing circuit including resistors R15 and R16, and applied to the base of the NPN transistor Tr3. The emitter of the transistor Tr3 is connected to the base of the NPN transistor Tr4, and the collector is connected to the electric wire 29 through the resistor R9. The emitter of the transistor Tr4 is grounded, and the collector is connected to the collector of the transistor Tr3. The transistors Tr3 and Tr4 are configured in a Darlington connection.

In the control circuit 25 and the current amplifier circuit 26 configured as described above, the combined base-emitter voltage Vbe of the Darlington-connected transistors Tr3 and Tr4 is Vbe = Vbe3 + Vbe4, which is obtained by adding the base-emitter voltages. The base current Ib3 of the transistor Tr3 is Ib3 = (Vin−Vbe) / R15 when the output voltage of the charge control circuit 8 is Vin.
The combined current amplification factor hfe of the Darlington-connected transistors Tr3 and Tr4 is hfe = hfe3 × hfe4 obtained by integrating the combined current amplification factors.
From the above, the current I flowing through the resistor R9 is I = hfe3 × hfe4 × Ib3.

Here, for example, hfe3 = 400 and hfe4 = 40, and a current of about I = 200 mA is passed.
When the output voltage Vin of the charge control circuit 8 rises and approaches a predetermined voltage, the combined current amplification factor hfe increases rapidly, and the current I flowing through the resistor R9 also increases rapidly. Therefore, the charging voltage Vc of the auxiliary power supply 10 is slowed down and becomes as shown in the characteristic diagram of FIG. 6, and does not easily exceed the predetermined voltage.

(Embodiment 3)
FIG. 7 is a block diagram illustrating in detail a configuration example of an auxiliary power supply module included in the third embodiment of the vehicle power supply device according to the present invention. Since the schematic configuration of the third embodiment of the vehicle power supply device according to the present invention is the same as the schematic configuration (FIG. 1) described in the first embodiment, the description thereof is omitted.
In this auxiliary power supply module, the switch control circuit 27 is connected in parallel to the auxiliary power supply 10, and the switch circuit SW4 is connected between the resistor R7 and the positive terminal of the auxiliary power supply 10. The switch control circuit 27 performs on / off control of the switch circuit SW4. The other configuration example of the auxiliary power supply module is the same as the configuration example (FIG. 2) of the auxiliary power supply module 13 described in the first embodiment, and thus the description thereof is omitted.

  In the auxiliary power supply module having such a configuration, the switch control circuit 27 detects the charging voltage (output voltage) Vc of the auxiliary power supply 10 and compares the detected charging voltage Vc with a predetermined voltage. When it is high, the switch circuit SW4 is turned off. The other operations of this auxiliary power supply module are the same as the operations of the auxiliary power supply module 13 described in the first embodiment, and a description thereof will be omitted.

FIG. 8 is a circuit diagram showing in detail a configuration example of the switch control circuit 27 and the switch circuit SW4 shown in FIG.
In the switch control circuit 27 and the switch circuit SW4, a voltage obtained by dividing the charging voltage (output voltage) Vc of the auxiliary power supply 10 by the voltage dividing circuit 33 is applied to the non-inverting input terminal of the operational amplifier 34 via the resistor R18. The reference voltage Vref is applied to the inverting input terminal of the operational amplifier 34 via the resistor R17. The operational amplifier 34 is subjected to positive feedback to constitute a comparison circuit.

  The output terminal of the operational amplifier 34 (comparison circuit) is connected to the gate of the P-channel MOS FET 35. The source of the FET 35 is connected to one terminal of the resistor R 7, and the drain is connected to the plus terminal of the auxiliary power supply 10. A resistor R20 is connected between the source and gate of the FET 35.

In the switch control circuit 27 and the switch circuit SW4 configured as described above, when the divided voltage of the charging voltage Vc of the auxiliary power supply 10 applied to the electric wire 29 is higher than the reference voltage Vref, the output of the operational amplifier 34 becomes H level, The FET 35 is turned off. As a result, the charging voltage Vc of the auxiliary power supply 10 is maintained below the reference voltage.
When the reference voltage Vref is higher, the output of the operational amplifier 34 is 0 (L level, ground potential), the FET 35 is turned on, and the auxiliary power supply 10 is charged.

1 Alternator (on-vehicle generator, AC generator)
2 Starter 4 Battery (Main power, lead acid battery)
6 Accessory Switch 7 Ignition Switch 8 Charge Control Circuit 9 Switching Circuit (Comparison Means, Switching Means)
10 auxiliary power supply 11 output switching circuit 12 idle stop ECU
13 Auxiliary power module 14-17 ECU (vehicle load group)
18, 19, 35 P-channel MOS type FET
20a, 20b N-channel MOS type FET
21, 32, 34 Operational amplifier 24, 27 Switch control circuit 25 Control circuit 26 Current amplification circuit 28, 29 Electric wire SW1-SW4 Switch circuit Tr1-Tr4 NPN transistor

Claims (5)

In a vehicle power supply device comprising an on-vehicle generator or a battery that is charged by a battery, and configured to supply power to an on-vehicle load group by the on-vehicle generator, battery, or capacitor,
A first switch circuit connected between the battery and the vehicle load group; a second switch circuit connected between the battery and the vehicle load group; means for comparing the output voltage values of the battery and the capacitor; When the battery (capacitor) has a higher comparison result, the first switch circuit is turned on (off), and the second switch circuit is turned off (on). Vehicle power supply device.   The first switch circuit and the second switch circuit each include a P-channel MOS type FET, and the FET has a drain connected to the battery or a capacitor side and a source connected to the load group side. Vehicle power supply device.   A charge voltage control circuit for controlling a charge voltage value of the battery, wherein the charge voltage control circuit includes a first resistor connected between the battery and the battery, a second resistor, and a third switch circuit connected in series; And a third circuit connected in parallel to the battery and means for comparing the charge voltage value and a predetermined voltage value, and when the means determines that the charge voltage value is higher, the third switch The power supply device for vehicles according to claim 1 or 2 constituted so that a circuit may be turned off.   The charging voltage control circuit further includes a charging voltage control circuit that controls a charging voltage value of the battery, and the charging voltage control circuit includes a first resistor connected between the battery and the battery, a third resistor, and a current amplifier circuit connected in series. And a second series circuit connected in parallel to the capacitor and means for detecting the charging voltage value, and the gain of the current amplifier circuit is increased or decreased according to the level of the charging voltage value detected by the means. The power supply device for vehicles according to claim 1 or 2 constituted so that it may do.   A charge voltage control circuit for controlling a charge voltage value of the capacitor, the charge voltage control circuit comprising: a first resistor connected between the battery and the capacitor; and a first resistor connected between the first resistor and the capacitor. A four-switch circuit and means for comparing the charge voltage value with a predetermined voltage value, and the means is configured to turn off the fourth switch circuit when the means determines that the charge voltage value is higher. The vehicle power supply device according to claim 1 or 2.

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