JP2013063002A - Auxiliary power supply device for vehicle - Google Patents

Abstract

The present invention provides an auxiliary power supply device for a vehicle that can efficiently use regenerative power by controlling the voltage / current at the time of charging / discharging of a capacitor, and that does not cause a problem even when the discharge voltage of the capacitor decreases.
An auxiliary power supply device for a vehicle is provided that includes a battery that is connected in parallel to a generator that is linked to an engine and stores electric power to be supplied to a load. A current limiting circuit 10 that limits a current from the generator 2 to the capacitor 8, a converter 11 that converts the output voltage of the capacitor 8, outputs the converted voltage to the load 3, and detects an output voltage of the converter 11. A second voltage detection circuit 6; and a rectifier circuit D connected between the output terminal of the generator 2 and the output terminal of the converter 11 and having a forward direction from the generator 2 to the converter 11 as a first direction. When the output voltage value of the generator 2 detected by the voltage detection circuit 4 is higher than a predetermined value, the switch SW1 between the generator 2 and the current limit circuit 10 is turned on to operate the current limit circuit 10.
[Selection] Figure 1

Description

  The present invention relates to a vehicular auxiliary power supply device that is connected in parallel to a generator that is linked to an engine and that has a capacitor that stores electric power to be supplied to a load.

In electric locomotives and trains, a regenerative brake that generates power with a main motor during braking and returns the generated power to an overhead line has been put into practical use for a long time, and the generated power is called regenerative power. Also in electric vehicles and hybrid cars, regenerative brakes that regenerate electric power with a motor by rotating wheels during braking and charge a storage battery mounted on the vehicle have been put into practical use.
In recent years, in general engine-driven vehicles other than electric vehicles and hybrid vehicles, an alternator (alternator, on-vehicle generator) is operated at a high load especially during deceleration to obtain regenerative power. And there are things that reduce the operational load during cruising and improve fuel economy.

FIG. 7 is a block diagram showing a configuration example of an auxiliary power supply device for a vehicle (Japanese Patent Application No. 2011-200589) filed earlier by the applicant of the present application.
This auxiliary power device for a vehicle is suitably used for a general engine-driven vehicle, and can control the voltage and current during charging / discharging of a capacitor to efficiently use regenerative power and improve the fuel consumption of the vehicle. Is possible.

The vehicle auxiliary power supply 16 is connected in parallel to an alternator (generator, AC generator) 2 that generates electric power, rectifies and outputs in conjunction with the engine 1, a battery 15, and loads 12, 13, and 14 mounted on the vehicle. It is connected to the. The voltage detector 4 detects output voltage values of the alternator 2 and the battery 15.
The vehicular auxiliary power supply 16 charges the battery 8 with the power supplied from the alternator 2 and the battery 15 through the switch SW1, the current detector 5, and the current limiting circuit 10. The current limiting circuit 10 is, for example, a DC / DC converter for controlling a charging current value to the battery 8.

The battery 8 is configured by, for example, connecting a plurality of electric double layer capacitors in series. The voltage detector 7 detects the output voltage value of the battery 8.
The electric power discharged from the battery 8 is given to a load (for example, an oil pump motor or a cooling water pump motor) 3 related to the rotation of the engine 1 through the DC / DC converter 11 and the switch SW2. The voltage detector 6 detects the output voltage value of the DC / DC converter 11.
The DC / DC converter 11 performs DC / DC conversion so that the voltage value detected by the voltage detector 6 becomes the drive voltage value of the load 3 based on the output voltage value of the battery 8 detected by the voltage detector 7.

The control unit 9 of the auxiliary power supply device 16 for the vehicle includes a rotation speed signal of the engine 1, a vehicle speed signal, a signal indicating an on / off state of the ignition switch, a voltage value signal detected by the voltage detectors 4, 6, and 7, and a current The current value signal detected by the detector 5 is given. The control unit 9 performs on / off control of the switches SW1 and SW2 based on the given signals, and drives and controls the current limiting circuit 10 and the DC / DC converter 11.
For example, the output voltage value of the alternator 2 is 12.5V to 14.5V, and the maximum output voltage value of the battery 15 is 13V. The switch SW1 is turned on when the voltage value detected by the voltage detector 4 exceeds 13.5V, and the output voltage value of the DC / DC converter 11 is 10V to 12.5V.

  Patent Document 1 discloses a vehicle power source including a vehicular generator driven by a traveling engine and main power storage means, a backup power storage means, and a bidirectional connection between the vehicle power supply and the backup power storage means. A vehicle power control device including a DC-DC converter capable of switching connection and voltage conversion is disclosed. The DC-DC is configured to detect the traveling state of the vehicle, charge the reserve power storage means at the time of deceleration, and discharge the charged power prior to the main power storage means at a time other than the deceleration to supply to the vehicle electrical load. An electronic arithmetic unit for switching and controlling the converter is provided.

Japanese Patent No. 3465293

  In the vehicle auxiliary power supply device described above, when the engine 1 is rotating, the switch SW2 is turned on, and the DC / DC converter 11 converts the output voltage of the battery 8 to the vicinity of the output voltage values of the alternator 2 and the battery 15. To load 3. However, when the output voltage value of the battery 8 drops below a certain value, there is a problem that the DC / DC converter 11 cannot boost the voltage value required by the load 3. In this case, it is possible to supply power from the battery 15 to the load 3 through the current limiting circuit 10 and the DC / DC converter 11, but there is a problem that power that is not regenerative power is stored in the capacitor 8.

  The present invention has been made in view of the circumstances as described above, and by controlling the voltage and current during charging and discharging of the battery, it is possible to efficiently use the regenerative power and improve the fuel efficiency of the vehicle. Therefore, it is an object of the present invention to provide an auxiliary power supply device for a vehicle that does not cause a problem even when the discharge voltage of the battery is lowered.

  An auxiliary power supply for a vehicle according to a first aspect of the present invention is the auxiliary power supply for a vehicle, which is connected in parallel to a generator linked to the engine and stores a power for supplying power to a load. A first voltage detection circuit for detecting a value of the current, a current limiting circuit for limiting a current from the generator to the capacitor, a switch for turning on / off between the generator and the current limiting circuit, A converter that converts an output voltage and outputs the converted voltage to the load; a second voltage detection circuit that detects an output voltage of the converter; and an output terminal of the generator and an output terminal of the converter A rectifier circuit connected in a forward direction from the generator to the converter, and when the voltage value detected by the first voltage detection circuit is higher than a predetermined value, the switch is turned on, and the current Activate limit circuit Characterized in that are configured to cause.

In this vehicular auxiliary power supply device, the battery is connected in parallel to a generator interlocked with the engine, and a capacitor accumulates electric power to be supplied to a load. The first voltage detection circuit detects the value of the output voltage of the generator, and the current limiting circuit limits the current from the generator to the battery. The switch turns on / off between the generator and the current limiting circuit, and the converter converts the output voltage of the battery and outputs the converted voltage to the load. The second voltage detection circuit detects the output voltage of the converter, and the rectifier circuit connected between the output terminal of the generator and the output terminal of the converter sets the direction from the generator to the converter as the forward direction. . When the voltage value detected by the first voltage detection circuit is higher than a predetermined value, the switch is turned on to activate the current limiting circuit.
Thereby, when the output voltage of a converter falls, the output voltage from a generator or a battery is given to a load through a rectifier circuit.

  According to a second aspect of the present invention, there is provided a vehicle auxiliary power supply device comprising: a third voltage detection circuit that detects an output voltage value of the capacitor; a current detection circuit that detects a current value flowing through the load; the capacitor and a fixed potential terminal; A second switch for turning on / off between the output voltage value, the output voltage value detected by the third voltage detection circuit is lower than a second predetermined value lower than the predetermined value, and the current value detected by the current detection circuit is When smaller than the third predetermined value, the switch and the current limiting circuit are turned on, and the second switch is turned off.

In this auxiliary power supply for a vehicle, the third voltage detection circuit detects the output voltage value of the capacitor, the current detection circuit detects the current value flowing through the load, and the second switch includes the capacitor and the fixed potential terminal. Turn the interval on / off. When the output voltage value detected by the third voltage detection circuit is lower than the second predetermined value lower than the predetermined value and the current value detected by the current detection circuit is lower than the third predetermined value, the switch and the current limiting circuit are turned on, Turn off the second switch.
As a result, it is possible to supply power to the load using the smaller one of the loss through the rectifier circuit and the current limit circuit and the converter.

  The auxiliary power supply for a vehicle according to a third aspect of the present invention further includes a third switch for turning on / off between the load and the converter.

  In this vehicular auxiliary power supply, the third switch turns on / off between the load and the converter. Thereby, when the vehicle is idling stopped, discharge from the battery can be prevented.

  The auxiliary power supply for a vehicle according to a fourth aspect of the invention is characterized in that a maximum value of a current flowing through the converter is configured to be smaller than a maximum value of a current flowing through the current limiting circuit. To do.

  In this vehicle auxiliary power supply device, the maximum value of the current flowing through the converter is configured to be smaller than the maximum value of the current flowing through the current limiting circuit.

  The vehicular auxiliary power supply according to a fifth aspect of the present invention further includes a second current detection circuit that detects a current value flowing through the current limiting circuit, and the current limiting circuit detects the current detected by the second current detection circuit. The value is configured to operate so as to be smaller than a fourth predetermined value that is larger than the third predetermined value.

  In this auxiliary power supply for a vehicle, the second current detection circuit detects the current value flowing through the current limit circuit, and the current limit circuit detects that the current value detected by the second current detection circuit is greater than the third predetermined value. It operates so as to be smaller than the large fourth predetermined value.

  The auxiliary power supply for a vehicle according to a sixth aspect of the present invention further comprises means for determining whether or not the engine is rotating, and when it is determined that the means is not rotating, the third switch is turned off, The converter is configured to be stopped.

  In this auxiliary power supply for a vehicle, the determining means determines whether or not the engine is rotating, and when it is determined that the determining means is not rotating, the third switch is turned off and the converter is stopped. Let Thereby, when the vehicle is idling stopped, discharging from the battery can be stopped.

  In the vehicular auxiliary power device according to a seventh aspect of the present invention, the converter converts the voltage to a voltage value corresponding to the load based on the voltage values detected by the second voltage detection circuit and the third voltage detection circuit, respectively. It is configured.

  In this auxiliary power supply for a vehicle, the converter converts the voltage value corresponding to the load based on the voltage values detected by the second voltage detection circuit and the third voltage detection circuit, respectively.

  According to the auxiliary power supply device for a vehicle according to the present invention, it is possible to efficiently use the regenerative power by controlling the voltage and current during charging and discharging of the battery, and to improve the fuel consumption of the battery. Even if the discharge voltage is lowered, it is possible to realize an auxiliary power supply for a vehicle that does not cause a problem.

It is a block diagram which shows the structure of embodiment of the auxiliary power supply device for vehicles which concerns on this invention. It is a timing chart which shows the example of operation of the auxiliary power unit for vehicles carried in the idle stop car. It is a timing chart which shows the example of operation of the auxiliary power unit for vehicles carried in vehicles which are not idle stop vehicles. It is a timing chart which shows the example of operation of the auxiliary power unit for vehicles concerning the present invention. It is a block diagram which shows the structure of embodiment of the auxiliary power supply device for vehicles which concerns on this invention. It is a flowchart which shows the example of operation | movement of the auxiliary power supply device for vehicles which concerns on this invention. It is a block diagram which shows the structural example of the auxiliary power supply device for vehicles applied previously.

Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the first embodiment of the auxiliary power supply for a vehicle according to the present invention.
The vehicle auxiliary power supply 16 is connected in parallel to an alternator (generator, AC generator) 2 that generates electric power, rectifies and outputs in conjunction with the engine 1, a battery 15, and loads 12, 13, and 14 mounted on the vehicle. It is connected to the. A voltage detector (first voltage detection circuit) 4 detects output voltage values of the alternator 2 and the battery 15.

The auxiliary power supply device 16 for the vehicle charges the battery 8 with the power supplied from the alternator 2 and the battery 15 through the switch SW1, the current detector (second current detection circuit) 5, and the current limiting circuit 10. The current limiting circuit 10 includes a power MOSFET (Metal oxide Semiconductor Field Effect Transistor), a DC / DC converter, or the like, and controls a charging current value to the battery 8.
The battery 8 is configured by, for example, connecting a plurality of electric double layer capacitors in series. A voltage detector (third voltage detection circuit) 7 detects the output voltage value of the battery 8.

The electric power discharged from the battery 8 is given to a load (for example, an oil pump motor or a cooling water pump motor) 3 related to the rotation of the engine 1 through a DC / DC converter (converter) 11 and a switch (third switch) SW2. It is done. A voltage detector (second voltage detection circuit) 6 detects the output voltage value of the DC / DC converter 11.
The DC / DC converter 11 performs DC / DC conversion so that the voltage value detected by the voltage detector 6 becomes the drive voltage value of the load 3 based on the output voltage value of the battery 8 detected by the voltage detector 7.
A diode (rectifier circuit) D has an anode connected to the output terminal of the alternator 2 and the battery 15 and a cathode connected to the output terminal of the DC / DC converter 11.

Here, the charging current value passed by the current limiting circuit 10 and the discharging current value passed by the DC / DC converter 11 are set such that their maximum values are different, and in particular, the maximum value of the discharging current. Is set smaller than the maximum value (fourth predetermined value) of the charging current. Thereby, the electric wire (thin diameter electric wire compared with the charge side) and the DC / DC converter 11 according to the flowing current can be used as the power supply path to the specific load 3, and the regenerative power is effectively utilized. It becomes possible.
The current limiting circuit 10 operates so that the charging current value detected by the current detector 5 is smaller than the set maximum value.

The control unit 9 of the auxiliary power supply device 16 for the vehicle includes a rotation speed signal of the engine 1, a vehicle speed signal, a signal indicating an on / off state of the ignition switch, a voltage value signal detected by the voltage detectors 4, 6, and 7, and a current The current value signal detected by the detector 5 is given. The control unit 9 performs on / off control of the switches SW1 and SW2 based on the given signals, and drives and controls the current limiting circuit 10 and the DC / DC converter 11.
For example, the output voltage value of the alternator 2 is 12.5V to 14.5V, and the maximum output voltage value of the battery 15 is 13V. The switch SW1 is turned on when the voltage value detected by the voltage detector 4 exceeds 13.5V, and the output voltage value of the DC / DC converter 11 is 10V to 12.5V. The directional voltage drop is 0.5V.

In the vehicular auxiliary power supply device 16 having such a configuration, the control unit 9 determines whether or not the engine 1 is rotating based on the rotation speed signal of the engine 1, and switches the switch if the engine 1 is rotating. The SW 2 is turned on, the DC / DC converter 11 is operated, the battery 8 is discharged, and the load 3 is supplied with power.
The controller 9 reads the output voltage value V1 of the alternator 2 and the battery 15 detected by the voltage detector 4 while discharging from the battery 8, and the read voltage value V1 is, for example, 13.5 V (predetermined value). Determine if it is higher.
When the voltage value V1 is higher than 13.5 V, the control unit 9 turns on the switch SW1, operates the current limiting circuit 10, and charges the battery 8 to charge.

When the engine 1 is not rotating, the control unit 9 turns off the switch SW2, stops the DC / DC converter 11, and stops the discharge from the battery 8.
In the vehicle auxiliary power supply 16, in the above-described operation, the voltage value boosted by the DC / DC converter 11 is lower than the output voltage value of the battery 15 by more than 0.5 V as a result of the decrease in the discharge voltage of the battery 8. When the diode D turns on. Thereby, the power output from the battery 15 is supplied to the load 3 through the diode D.

FIG. 2 is a timing chart showing an example of the operation of the auxiliary vehicle power supply device 16 mounted on the idle stop vehicle.
In this vehicle, the alternator 2 is operated with a high load (increasing the field current) particularly during deceleration (FIG. 2A), and a high voltage regenerative power (FIG. 2C) is obtained during acceleration and cruise, The operating load during acceleration and cruising is reduced to improve fuel efficiency. The vehicle auxiliary power supply device 16 charges the capacitor 8 with this high voltage regenerative power by turning on the switch SW1 (FIG. 2E) and operating the current limiting circuit 10 (FIG. 2D).

  When the engine 1 is an idle stop vehicle that automatically stops when the vehicle stops and is automatically started by an accelerator operation or a brake operation, the switch SW2 is turned off when the engine 1 is not rotating, including the case of an idle stop. (FIG. 2F), the DC / DC converter 11 is stopped, and the discharge from the battery 8 is stopped (FIGS. 2B and 2D). Thereby, when idling is stopped, the discharge from the battery 8 is stopped, so that the regenerative power can be used effectively.

FIG. 3 is a timing chart showing an example of the operation of the vehicular auxiliary power supply device 16 mounted on a vehicle that is not an idle stop vehicle.
In this vehicle, the switch SW2 shown in FIG. 1 is unnecessary, and the DC / DC converter 11 is operated to discharge from the battery 8 when the engine 1 rotates (FIGS. 3B and 3D). In addition, the alternator 2 is operated at a high load especially during deceleration (Fig. 3A), and a high voltage regenerative power (Fig. 3C) is obtained during acceleration and cruising, reducing the operating load during acceleration and cruising. And improve fuel economy. The vehicle auxiliary power supply 16 charges the capacitor 8 with this high voltage regenerative power by turning on the switch SW1 (FIG. 3E) and operating the current limiting circuit 10 (FIG. 3D).

FIG. 4 is a timing chart showing the operation when the discharge voltage of the battery 8 is lowered in the operation shown by the timing charts of FIGS.
Here, the output voltage (main power supply voltage) of the alternator 2 and the battery 15 is 12.5 V (FIG. 4B).
In the vehicular auxiliary power supply 16, when the discharge voltage (capacitor voltage) of the battery 8 decreases (FIG. 4A), the voltage value boosted by the DC / DC converter 11 falls below 12.5 V (FIG. 4C), and the load Similarly, the voltage applied to 3 decreases (FIG. 4D).

When the discharge voltage (capacitor voltage) of the battery 8 further decreases (FIG. 4A) and the voltage value boosted by the DC / DC converter 11 decreases to 12 V (FIG. 4C), the diode D is turned on, the alternator 2 and the battery 15 Output voltage (main power supply voltage) (FIG. 4B) is applied to the load 3 through the diode D with a drop of 0.5 V (FIG. 4D).
This state (FIGS. 4C and 4D) continues until the battery 8 is charged by the high voltage regenerative power (FIG. 4B) output from the alternator 2 when the vehicle is decelerated.

When the battery 8 is charged with regenerative power and the charging voltage (discharge voltage) increases, the voltage value boosted by the DC / DC converter 11 exceeds 12V (FIG. 4C), the diode D is turned off, and the DC The voltage boosted by the DC converter 11 is applied to the load 3 (FIG. 4D).
The DC / DC converter 11 boosts the output voltage to 12.5 V (FIG. 4C) and applies it to the load 3 (FIG. 4D) as the discharge voltage of the battery 8 increases (FIG. 4A).

(Embodiment 2)
FIG. 5 is a block diagram showing the configuration of the second embodiment of the auxiliary power supply for a vehicle according to the present invention.
In the auxiliary power supply device 16a for a vehicle, a switch (second switch) SW3 is connected between the capacitor 8 and the ground terminal, and the switch SW3 is controlled to be turned on / off by the control unit 9, and when turned off, the capacitor 8 Stop charging and discharging.
A current detector (current detection circuit) 17 for detecting a current flowing through the load 3 is provided between the switch SW2 and the load 3, and the current value detected by the current detector 17 is given to the control unit 9.

  Based on the current value I given from the current detector 17, the control unit 9 causes the loss (0.5 ××) through the diode D when the diode D (forward voltage drop 0.5 V) is turned on. I) is compared with the loss when passing through the current limiting circuit 10 and the DC / DC converter 11.

Here, since the loss of the current limiting circuit 10 and the DC / DC converter 11 is related to the on-resistance of the power MOSFET or the efficiency of the converter, it is proportional to the square of the current value I. Accordingly, when the current value I is larger than the predetermined value I1, the loss is smaller through the diode D, and when the current value I is smaller than the predetermined value I1, the current passes through the current limiting circuit 10 and the DC / DC converter 11. The loss is smaller.
Actually, the predetermined value I1 is obtained in advance by actual measurement or calculation and stored in a memory (not shown) built in the control unit 9. The other configuration is the same as the configuration of the first embodiment described above, and a description thereof will be omitted.

Hereinafter, an example of the operation of the vehicular auxiliary power supply device 16a having such a configuration will be described with reference to the flowchart of FIG. 6 showing the operation.
First, the control unit 9 reads the output voltage value Vc of the battery (capacitor) 8 from the voltage detector 7 (S1), and determines whether or not the output voltage value Vc is higher than 6V (S3). Note that 6V is a minimum input voltage value at which the DC / DC converter 11 can step up and output 12V.
If the output voltage value Vc is higher than 6V (S3), the controller 9 reads the output voltage value Vc of the battery 8 from the voltage detector 7 again (S1).

If the output voltage value Vc is not higher than 6V (S3), the controller 9 reads the current value I flowing through the load 3 from the current detector 17 (S5), and determines whether the current value I is smaller than the predetermined value I1. Is determined (S7).
If the current value I is not smaller than the predetermined value I1 (S7), the controller 9 reads the output voltage value Vc of the battery 8 from the voltage detector 7 as it is (S1). As a result, the diode D is turned on, and the output voltage of the battery 15 is stepped down to 12V via the diode D and applied to the load 3.

  If the current value I is smaller than the predetermined value I1 (S7), the control unit 9 turns on the switch SW1, turns off the switch SW3, operates the current limiting circuit 10 (S9), and then outputs the output voltage of the battery 8 The value Vc is read from the voltage detector 7 (S1). As a result, the output voltage of the battery 15 via the current limiting circuit 10 is boosted to 12.5 V by the DC / DC converter 11 and applied to the load 3. Further, the diode D is not conductive. Since other operations are the same as those of the first embodiment described above, description thereof is omitted.

1 Engine 2 Alternator (generator)
3 Load (load related to engine drive)
4 Voltage detector (first voltage detection circuit)
5 Current detector (second current detection circuit)
6 Voltage detector (second voltage detection circuit)
7 Voltage detector (third voltage detection circuit)
8 Capacitor 9 Control unit 10 Current limit circuit 11 DC / DC converter (converter)
12, 13, 14 Load 15 Battery 16, 16a Auxiliary power supply device for vehicle 17 Current detector (current detection circuit)
D Diode (rectifier circuit)
SW1 switch SW2 switch (third switch)
SW3 switch (second switch)

Claims (7)

In an auxiliary power supply for a vehicle, which is connected in parallel to a generator linked to an engine and includes a capacitor that stores electric power to be supplied to a load.
A first voltage detection circuit that detects a value of the output voltage of the generator, a current limit circuit that limits a current from the generator to the capacitor, and turns on / off between the generator and the current limit circuit A switch, a converter that converts the output voltage of the battery, and outputs the converted voltage to the load; a second voltage detection circuit that detects the output voltage of the converter; an output terminal of the generator and the conversion A rectifier circuit connected between output terminals of the generator and having a forward direction from the generator to the converter, and when the voltage value detected by the first voltage detection circuit is higher than a predetermined value, the switch An auxiliary power supply for a vehicle, wherein the current limiting circuit is activated by turning on the power.   A third voltage detection circuit for detecting an output voltage value of the capacitor, a current detection circuit for detecting a current value flowing through the load, and a second switch for turning on / off between the capacitor and a fixed potential terminal. And when the output voltage value detected by the third voltage detection circuit is lower than a second predetermined value lower than the predetermined value and the current value detected by the current detection circuit is lower than a third predetermined value, the switch and The auxiliary power supply for a vehicle according to claim 1, wherein a current limiting circuit is turned on and the second switch is turned off.   The auxiliary power supply for vehicles according to claim 1 or 2 further provided with the 3rd switch which turns on / off between said load and converters.   4. The vehicle auxiliary device according to claim 1, wherein a maximum value of a current flowing through the converter is configured to be smaller than a maximum value of a current flowing through the current limiting circuit. 5. Power supply.   The current limiting circuit further includes a second current detection circuit that detects a current value flowing through the current limiting circuit, and the current limiting circuit includes a fourth current value detected by the second current detection circuit that is greater than the third predetermined value. The auxiliary power supply for a vehicle according to any one of claims 1 to 4, wherein the auxiliary power supply for a vehicle is configured to operate so as to be smaller than a predetermined value.   The apparatus further comprises means for determining whether or not the engine is rotating. When it is determined that the means is not rotating, the third switch is turned off and the converter is stopped. The auxiliary power supply for a vehicle according to any one of claims 3 to 5.   The said converter is comprised so that it may convert into the voltage value according to the said load based on the voltage value which the said 2nd voltage detection circuit and the 3rd voltage detection circuit each detected. The auxiliary power supply for a vehicle according to item 1.

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