JP2010104123A - Vehicular power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a vehicular power supply unit which stabilizes the output electric power of a generator by increasing the output of a generator and by supplying a stable field current to a field regulation circuit. <P>SOLUTION: The vehicular power supply unit includes: an AC power generating device 210, which is driven by a drive source of a vehicle; a rectifier 220, which rectifies an AC voltage generated by the AC power generating device to a direct current to output a DC voltage V1; a field regulation device 230, which regulates a field current to the AC power generating device and makes variable a generated voltage value of the AC power generating device; a voltage conversion device 400, which converts the DC voltage from the rectifier into a DC voltage V2 different in a voltage value; and a storage battery 700, into which the DC voltage outputted by the rectifier is charged and which supplies a current to an electric load via the voltage conversion device. In this power supply unit, a voltage control means 300 is provided which controls the generated voltage of the AC power generating device so as to reach a target voltage determined based on the rotational speed of at least the AC power generating device 210. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle power supply device.

  A generator mounted on a vehicle is provided with a three-phase armature winding on a stator armature core, and a field winding on a rotor magnetic core, which is driven by rotation of the internal combustion engine of the vehicle. A three-phase AC generator that is driven to generate power, a rectifier that rectifies the three-phase AC voltage generated thereby and converts it to a DC voltage, and detects the output voltage of the rectifier to make a field value to be a predetermined value. For example, Japanese Patent Application No. 2008-185450 (Japanese Patent Application Laid-Open No. 21-185) discloses a vehicle power supply device that uses a generator to adjust a field current flowing through a winding. ), A generator that is driven by the rotation of the internal combustion engine of the vehicle and outputs a DC voltage, and a voltage converter that converts the DC voltage from the generator into a DC voltage having a different voltage value. Vehicle power connected to the converter There are some which increase the output of the generator by changing the generated voltage of the generator according to the required load power to the air load.

  Further, as a conventional vehicle power supply device for changing the power generation voltage of the power generator to increase the power output of the power generator, for example, as disclosed in Japanese Patent Laid-Open No. 9-252546 (Patent No. 3624334), a switch to a lead storage battery is used. When it is judged that the vehicle is decelerating, the lead storage battery is disconnected from the electric double layer capacitor, and the generator voltage mounted on the vehicle is connected to the vehicle. When the electric double layer capacitor is charged by setting the maximum allowable voltage value of the mounted electric load (for example, wiper motor or pump) and the deceleration state is released, the voltage value of the electric double layer capacitor is If power generation by the generator is stopped until the voltage value of the lead storage battery drops due to power supply to the load, and the voltage value of the electric double layer capacitor falls below the voltage value of the lead storage battery The, as well as connect the electric double layer capacitor and lead-acid battery, there is to perform a normal power generation in the generator.

JP-A-9-252546

By the way, in such a vehicle power supply device, since the power generation voltage of the generator is adjusted to the power required from the electric load mounted on the vehicle, the power generator is not necessarily efficiently used at the power generation voltage that maximizes the power. There was a problem of not driving. In addition, a normal generator supplies a field current from the output side of the generator, and the voltage applied to the field adjustment circuit changes when the generator is operated with the generated voltage variable. For this reason, it is difficult to control the supply of a stable field current, and as a result, the output power of the generator may become unstable.
In addition, when the voltage on the output side of the generator is 0 V (for example, the voltage converter is an insulated voltage converter and immediately after the internal combustion engine of the vehicle is started), the field flowing through the field winding There was a problem that a magnetic current could not be supplied and as a result the generator could not generate electricity.

  This invention has been made to solve the above problems, and can drive a generator with a power generation voltage at which output power is maximized, whereby the output of the generator can be increased, It is another object of the present invention to provide a vehicular power supply apparatus that can supply a stable field current to the field adjustment circuit and stabilize the output power of the generator.

The vehicle power supply device according to the present invention includes an AC power generator driven by an internal combustion engine of a vehicle or other drive source, and a rectifier that outputs a DC voltage V1 by rectifying an AC voltage generated by the AC power generator into a direct current. A field adjustment device that adjusts a field current to the AC power generation device and varies a power generation voltage of the AC power generation device, and converts a DC voltage V1 from the rectifier to a DC voltage V2 having a different voltage value Based on a voltage converter that performs charging, a storage battery that charges a DC voltage output from the rectifier and supplies current to an electric load mounted on a vehicle via the voltage converter, and at least a rotational speed of the AC generator Voltage control means for controlling the power generation voltage of the AC power generator so that the determined target power generation voltage is obtained.

  In the vehicle power supply device described above, the current supply to the field adjustment device is performed from the DC voltage V2 on the output side of the voltage conversion device.

  Alternatively, in the above-described vehicle power supply device, the power conversion device is an insulated voltage conversion device, and the current supply to the field adjustment device is performed by using the DC voltage V1 on the input side of the voltage conversion device or the DC voltage V2 on the output side. Current supply switching means for switching between the first and second operations, and when the generated voltage in the AC generator is below a predetermined value, the output voltage is supplied to the field regulator by the DC voltage V2 on the output side, and the generated voltage is When the value is larger than the value, current is supplied to the field adjustment device by the DC voltage V1 on the input side.

  Furthermore, the vehicle power supply device according to the present invention outputs an AC power generator driven by an internal combustion engine of a vehicle or other drive source, and a DC voltage V1 by rectifying the AC voltage generated by the AC power generator into a direct current. A rectifying device that adjusts a field current to the AC power generation device and varies a power generation voltage of the AC power generation device, and a DC voltage V2 having a different voltage value from the DC voltage V1 from the rectification device. And a voltage control means for controlling the power generation voltage of the AC power generator so as to be a target power generation voltage determined based on at least the required electric load power and the rotational speed of the AC power generator. The current supply to the field adjustment device is performed from the DC voltage V2 on the output side of the voltage conversion device.

According to the vehicle power supply device of the present invention, since the output power of the alternator can be charged to the storage battery, the output is based on the rotational speed of the AC power generator regardless of the required load power of the electrical load mounted on the vehicle. Since the alternator can be generated with the power generation voltage that maximizes the electric power, the output of the alternator can be increased.
In addition, since the power generation of the alternator can be stopped during the period in which power is supplied to the electric load connected to the vehicle by discharging the storage battery, energy consumption by the internal combustion engine of the vehicle or other drive source can be reduced.

  In addition, since the field current flowing from the output side of the voltage converter to the field adjustment device is supplied, a stable field current can be supplied to the field adjustment device, and the output power of the alternator can be stabilized. it can.

  The above-described and other objects, features, and effects of the present invention will become more apparent from the detailed description and the drawings in the following embodiments.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol shall show the same or an equivalent part.
Embodiment 1 FIG.
1 is a configuration diagram of a vehicle power supply device according to Embodiment 1 of the present invention.
In FIG. 1, the alternator 200 includes an AC power generator 210, a rectifier 220, and a field adjustment device 230. The AC power generator 210 is provided with a three-phase armature winding on the armature core of the stator, and a field winding is provided on the magnetic pole core of the rotor. Are connected mechanically (both not shown).
The rectifier 220 is a rectifier that rectifies a three-phase AC voltage and supplies a DC voltage. The field adjusting device 230 is a device that adjusts the current flowing through the field winding of the AC power generator 210.
The voltage control means 300 calculates a target power generation voltage of the alternator 200 and controls the power generation voltage of the alternator 200 so that the target voltage value is obtained.
The storage battery 700 is, for example, an electric double layer capacitor, is charged by the DC voltage V1 output from the alternator 200, and supplies current to the electric load 600 mounted on the vehicle via the voltage conversion device 400. The voltage converter 400 converts the DC voltage V1 output from the rectifier 220 into a DC voltage V2 having a different voltage value and outputs the converted voltage. Reference numeral 500 denotes a lead storage battery, and 600 denotes an electric load mounted on the vehicle, both of which are connected to the output side of the voltage converter 400.

Next, the operation of the alternator 200 will be described.
The voltage control means 300 adjusts the current flowing through the field winding of the AC power generator 210 so that the detected voltage V1 becomes a target voltage value. When the detected voltage V1 is larger than the target voltage value, the current flowing through the field winding of the AC power generator 210 is adjusted to be small, and when the detected voltage V1 is smaller than the target voltage value The current flowing through the field winding of the AC power generator 210 is adjusted so as to increase. When the current flowing through the field winding is controlled, the amount of magnetic flux generated by the rotor having the field winding is controlled. The AC voltage induced in the three-phase armature winding changes according to the amount of magnetic flux generated by the rotor. The induced AC voltage is converted into a DC voltage by the rectifier 220 and output as a DC voltage V1.
In this way, the voltage control means 300 adjusts the current flowing through the field winding and controls the voltage output from the alternator 200 to be V1, so that the output of the alternator 200 is always the predetermined output voltage V1.

Next, output characteristics of the alternator 200 will be described.
In the alternator 200, when the current passed through the field winding is constant, the rotational speed of the AC power generator 210 increases and the output power increases. Along with this, the current of the three-phase armature winding also increases, and the alternator 200 generates heat. In order to ensure safety and reliability, it is necessary to maintain this heat generation below a predetermined value. In the alternator 200, the output current and the heat generation amount are adjusted by adjusting the current flowing through the field winding by the field adjustment device 230. However, since the heat generation amount depends on the current, the large output In order to obtain electric power, the generated voltage may be increased while keeping the current as it is.

  FIG. 2 shows a relationship between the rotational speed of the AC power generator 210 and the output power when the power generation voltage of the alternator 200 is 14 V and 28 V, for example. If the rotational speed of the AC power generator 210 is Na or less, a larger output power can be obtained when the power generation voltage of the alternator 200 is set to 14 V. If the rotational speed of the AC power generator 210 is faster than Na, the alternator 200 Larger output power can be obtained by setting the generated voltage to 28V.

Next, a processing flow in the vehicle power supply device of the first embodiment will be described with reference to the flowchart of FIG. In FIG. 3, in step S1, vehicle information such as the rotation speed of the internal combustion engine 100, required electric load power, and voltages V1 and V2 is acquired.
The rotational speed of the internal combustion engine 100 can be detected by using, for example, a crank angle sensor (not shown).
The required electric load power can be calculated, for example, by detecting an on / off signal (not shown) of the electric load 600 mounted on the vehicle.
The voltages V1 and V2 can be detected by using, for example, a voltage sensor (not shown).

Subsequently, drive determination of the alternator 200 is performed in step S2.
As a drive determination condition of the alternator 200, for example, an SOC (State of Charge) of the storage battery 700 is used. The SOC of the storage battery 700 can be detected from the voltage V2 or the like.
When the SOC of the storage battery 700 is equal to or less than the predetermined value, it is determined that the alternator 200 is driven, and the process proceeds to step S3. When the SOC of the storage battery 700 is larger than a predetermined value, the storage battery 700 is sufficiently charged, and the current supply to the electric load 600 connected to the vehicle can be performed by the storage battery 700, so that power generation by the alternator 200 is not necessary. It is determined that the alternator is not driven, and the process proceeds to step S6.

In step S3, the target voltage value Vt of the alternator 200 is calculated.
Here, the power generation voltage and output power of the alternator 200 at a predetermined rotational speed of the AC power generator 210 have a relationship as shown in FIG. That is, there is a point where the output power (P1 to P5) of the alternator 200 becomes maximum when the power generation voltage (Vo1 to Vo5) of the predetermined alternator 200 is set at a predetermined rotational speed of the AC power generator 210. I understand. From this relationship, the target voltage value Vt of the alternator 200 is determined according to the rotational speed (N1 to N5) of the AC power generator 210, as shown in FIG. FIG. 5 is a diagram in which the rotation speed (N1 to N5) of the AC power generator 210 and the target voltage value of the alternator 200 that maximizes the output power of the alternator 200 are plotted based on FIG.

In step S4, voltage control of the alternator 200 is performed.
The power generation voltage of the alternator 200 is controlled so as to be the target voltage value Vt of the alternator 200 calculated in step S3. Specifically, the processing flow shown in FIG. 6 is performed.
In FIG. 6, V1 is a DC voltage output from the alternator 200. In step S41, V1 is compared with the target voltage value Vt. If V1 is larger than the target voltage value Vt, the alternator is reduced by reducing the current flowing through the field winding of AC generator 210 in step S42. Reduce the generated voltage. When V1 is equal to or lower than the target voltage value Vt, the generated voltage of the alternator is increased by increasing the current flowing through the field winding of the AC power generator 210 in step S43. Thereby, the DC voltage output from the alternator 200 is controlled to be Vt.

In step S5, charging control of the storage battery 700 is performed.
As described above, since the target voltage value of the alternator 200 is set so that the output power of the alternator 200 is maximized, the output power of the alternator 200 is required by the electric load 600 mounted on the vehicle. It is likely to be larger than electric power. The electric power generated above the electric load electric power is charged in the storage battery 700, and the process proceeds to step S8.

  On the other hand, if it is determined in step S2 that the alternator 200 is not driven, the process proceeds to step S6. In step S6, power generation stop control of the alternator 200 is performed. Specifically, the power generation of the alternator 200 is stopped by setting the current flowing through the field winding of the AC power generator 210 to zero.

In step S7, discharge control of the storage battery 700 is performed.
In step S6, since the power generation of the alternator 200 is stopped, current supply to the electric load 600 connected to the vehicle is performed by discharging from the storage battery 700, and the process proceeds to step S8.

In step S8, the voltage converter 400 is controlled, and the processing flow of FIG. That is, in the voltage converter 400, the DC voltage V1 output from the alternator 200 or the storage battery 700 is converted into the DC voltage V2, or the DC voltage V1 is bypassed and output, and is supplied to the electric load 600 connected to the vehicle. Specifically, the processing flow shown in FIG. 7 is performed.
In FIG. 7, in step S81, the voltage deviation between the voltage V1 and the voltage V2 is compared with a predetermined value. If the voltage deviation between the voltage V1 and the voltage V2 is larger than the predetermined value, the DC voltage V1 is converted into a direct current in step S82. Step down to voltage V2 and output. If the voltage deviation between the voltage V1 and the voltage V2 is equal to or less than the predetermined value, the DC voltage V1 is bypassed and output in step S83.

As described above, according to the vehicle power supply device of the first embodiment of the present invention, the output power of the alternator 200 can be charged to the storage battery 700, so that the required load power of the electric load 600 mounted on the vehicle is concerned. Instead, the alternator 200 can be generated with the generated voltage that maximizes the output power based on the rotational speed of the AC power generator 210, and the alternator 200 can be increased in output.
In addition, since the power generation of the alternator 200 can be stopped during the period in which power is supplied to the electric load connected to the vehicle by discharging the storage battery 700, the energy consumption by the internal combustion engine 100 of the vehicle or other drive source (not shown). Can be reduced.

  Further, when the voltage deviation between the DC voltage V1 output from the rectifier 220 and the voltage V2 on the output side of the voltage converter 400 is equal to or less than a predetermined value, the step-down operation by the voltage converter 400 is stopped, so the voltage converter No switching loss occurs in the switching element in the voltage converter during the step-down operation, and the output power of the alternator 200 can be efficiently supplied to the electric load 600 connected to the vehicle.

As is clear from FIG. 2, when the generated voltage of the alternator 200 is increased, the output power is increased in the region where the rotational speed of the AC power generator 210 is high (> Na).
In general, the generated voltage of the alternator 200 may be set to a constant value (> V2) so that the output power of the alternator 200 is increased in consideration of the rotational speed region used for traveling of the vehicle, so that the alternator 200 has a high output. It becomes.

Embodiment 2. FIG.
FIG. 8 shows a configuration diagram of the vehicle power supply device according to the second embodiment of the present invention.
The vehicle power supply device according to the second embodiment is different from FIG. 8 in that it supplies a field current that is supplied to the field adjustment device 230 from the DC voltage V2 (for example, 14V) on the output side of the voltage conversion device 401. These are equivalent to the configuration of the first embodiment, and the same reference numerals are used for the same or corresponding parts as the configuration shown in FIG.
In addition, the processing flow in the second embodiment is completely the same as that in the first embodiment, and a description thereof will be omitted.
Here, for safety, it is necessary to change the configuration of the voltage conversion device 401 depending on the target power generation value range of the alternator 200. When the maximum target power generation value of the alternator 200 is set to be larger than 60 V, an insulation type voltage converter that insulates the input side and the output side of the voltage converter 401 is used. When the maximum target power generation value of the alternator 200 is set to 60 V or less, a non-insulated voltage converter is used.

As can be seen from the above, the target voltage value of the alternator 200 varies greatly depending on the rotational speed of the AC power generator 210. Since the power generation voltage of the alternator 200 is controlled by the current flowing through the field winding of the AC power generator 210 as described above, the voltage is constant to supply the current flowing through the field winding. Is desirable. This is equivalent to making the supply voltage for supplying the field current to the field adjustment device 230 constant. In the second embodiment, as shown in FIG. 8, the DC power on the output side of the voltage conversion device 401 is set. A field current to be supplied to the field adjusting device 230 is supplied from V2 (for example, 14V). For this reason, it becomes possible to supply a stable field current.
If the voltage conversion device 401 is an insulation type voltage conversion device, when the internal combustion engine of the vehicle is started, the voltage on the input side of the voltage conversion device 401 is 0 V, so that a field current flowing through the field winding is supplied. However, if it is a voltage on the output side of the voltage conversion device 401, it is possible to supply a current to flow through the field winding of the AC power generator 210.

FIG. 9 shows a modification of the second embodiment. As shown in FIG. 9, even when the storage battery 700 is not connected between the alternator 200 and the voltage converter 401, the voltage converter 401 By supplying a field current flowing from the output side to the field adjustment device 230, the voltage applied to the field adjustment device 230 becomes a fixed value V2 (for example, 14V), and a stable field current can be supplied.
However, in this configuration, the target power generation value of the alternator 200 depends not only on the rotational speed of the AC power generator 210 but also on the electric load power requested from the electric load 600 connected to the vehicle. Compared with this configuration, the power generation efficiency of the alternator 200 is low.

  As described above, according to the second embodiment of the present invention, in addition to the effects of the first embodiment, by supplying the field current flowing from the output side of the voltage conversion device 401 to the field adjustment device 230, the field The voltage supplied to the magnetic adjustment device 230 becomes a fixed value V2 (for example, 14V), and a stable field current can be supplied.

Embodiment 3 FIG.
FIG. 10 shows a configuration diagram of a vehicle power supply device according to Embodiment 3 of the present invention.
In the vehicle power supply device according to the third embodiment, in FIG. 10, the voltage conversion device 402 is an insulation type voltage conversion device, and the field magnet flowing from the input side or the output side of the voltage conversion device 402 to the field adjustment device 230. Except that the switch 800 for switching supply of current is provided, the configuration is the same as that of the first embodiment, and the same reference numerals are used for the same or corresponding parts as the configuration shown in FIG.
Further, since the operation is the same as that of the first embodiment except for the switching operation of the switch 800, the description other than the switching operation of the switch 800 is omitted.

As described above, when the maximum value of the target voltage value of the alternator 200 is set to 60 V or more, the insulated voltage converter 402 is used from the viewpoint of safety. However, since it is an insulated voltage converter, the DC voltage V1 on the input side of the voltage converter 402 is 0 V during the period when the alternator 200 is not generating power. For this reason, during the period when the alternator 200 is not generating power (for example, immediately after starting the internal combustion engine 100 of the vehicle), the field current cannot be supplied to the field adjustment device 230 from the input side of the voltage conversion device 402. Therefore, the switch 800 is operated so that the field current flowing through the field adjustment device 230 can be supplied from the output side of the voltage conversion device 402. When the generated voltage of the alternator 200 becomes equal to or higher than a predetermined value, the switch 800 is operated so that the field current flowing through the field adjustment device 230 can be supplied from the input side of the voltage conversion device 402.
In addition, it is possible that a component constituting the device such as the storage battery 700 fails and the DC voltage V1 on the input side of the voltage conversion device 402 becomes 0V. Even in such a case, the power generation by the alternator 200 can be continued by operating the switch 800 so that the field current flowing through the field adjustment device 230 can be supplied from the output side of the voltage conversion device 402. .

FIG. 11 shows a modification of the third embodiment. As shown in FIG. 11, the field adjustment device 230 even when the storage battery 700 is not connected between the alternator 200 and the voltage conversion device 402. Field switch is provided by switching the switch 800 according to the magnitude of the generated voltage of the alternator 200. The switch 800 switches whether to supply current to the input from the input side or output side of the insulated voltage converter 402. A stable field current can be supplied to the device 230, and the output power of the alternator 200 is stabilized.
However, in this configuration, the target power generation value of the alternator 200 depends not only on the rotational speed of the AC power generator 210 but also on the electric load power requested from the electric load 600 connected to the vehicle. Compared with this configuration, the power generation efficiency of the alternator 200 is low.

  As described above, according to the third embodiment of the present invention, the switch 800 for switching the current supply to the field adjustment device 230 from the input side or the output side of the insulated voltage conversion device 402 is provided, By switching the switch 800 according to the magnitude of the generated voltage of the alternator 200, it is possible to supply a stable field current to the field adjustment device 230, and the output power of the alternator 200 can be stabilized.

It is a figure which shows the structure of the vehicle power supply device of Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a figure which shows the relationship between the rotational speed of the alternating current generator with respect to the power generation voltage of an alternator, and the output electric power of an alternator. It is a flowchart which shows the process in Embodiment 1 of this invention. It is a figure which shows the relationship between the electric power generation voltage of an alternator with respect to the rotational speed of an alternating current generator, and output electric power in Embodiment 1 of this invention. It is a figure which shows the relationship between the rotational speed of an alternating current generator, and the target voltage value of an alternator in Embodiment 1 of this invention. It is a flowchart which shows the voltage control process of the alternator in Embodiment 1 of this invention. It is a flowchart which shows the process of control of the voltage converter in Embodiment 1 of this invention. It is a figure which shows the structure of the vehicle power supply device of Embodiment 2 of this invention. It is a figure which shows the modification which changed the structure of the power supply device for vehicles of Embodiment 2 of this invention partially. It is a figure which shows the structure of the vehicle power supply device of Embodiment 3 of this invention. It is a figure which shows the modification which changed the structure of the vehicle power supply device of Embodiment 3 of this invention partially.

Explanation of symbols

100 internal combustion engine, 200 alternator, 210 AC power generator,
220 rectifier, 230 field adjustment device, 300 voltage control means,
400, 401, 402 Voltage converter, 500 lead acid battery, 600 electric load,
700 storage battery, 800 switch (current supply switching means).

Claims (6)

  An AC power generator driven by an internal combustion engine of a vehicle or other drive source, a rectifier that rectifies an AC voltage generated by the AC power generator into a direct current and outputs a DC voltage V1, and a field to the AC power generator A field adjustment device that adjusts a magnetic current and varies a generated voltage of the AC generator, a voltage converter that converts a DC voltage V1 from the rectifier into a DC voltage V2 having a different voltage value, and the rectifier. A storage battery that charges a DC voltage to be output and supplies a current to an electric load mounted on the vehicle via the voltage converter, and a target generated voltage determined based on at least the rotational speed of the AC generator And a voltage control means for controlling the power generation voltage of the AC power generator.   2. The vehicle power supply device according to claim 1, wherein current supply to the field adjustment device is performed from a DC voltage V <b> 2 on the output side of the voltage conversion device.   The power converter is an insulated voltage converter, and the current supply for switching the current supply to the field adjustment device from the DC voltage V1 on the input side or the DC voltage V2 on the output side of the voltage converter Switching means, and when the generated voltage in the AC generator is below a predetermined value, current is supplied to the field adjustment device by the DC voltage V2 on the output side, and the generated voltage is greater than a predetermined value. The vehicle power supply device according to claim 1, wherein a current is supplied to the field adjustment device by the DC voltage V <b> 1 on the input side.   An AC power generator driven by an internal combustion engine of a vehicle or other drive source, a rectifier that rectifies an AC voltage generated by the AC power generator into a direct current and outputs a DC voltage V1, and a field to the AC power generator At least required is a field adjustment device that adjusts a magnetic current and varies a power generation voltage of the AC power generation device, and a voltage conversion device that converts a DC voltage V1 from the rectification device into a DC voltage V2 having a different voltage value. Voltage control means for controlling the power generation voltage of the AC power generation device so as to obtain a target power generation voltage determined based on the electric load power and the rotational speed of the AC power generation device, and a current to the field adjustment device Supplying from the DC voltage V2 of the output side of the said voltage converter, The vehicle power supply device characterized by the above-mentioned.   An AC power generator driven by an internal combustion engine of a vehicle or other drive source, a rectifier that rectifies an AC voltage generated by the AC power generator into a direct current and outputs a DC voltage V1, and a field to the AC power generator A field adjustment device that adjusts a magnetic current and varies a power generation voltage of the AC power generation device; an insulation type voltage conversion device that converts a DC voltage V1 from the rectification device into a DC voltage V2 having a different voltage value; Voltage control means for controlling the power generation voltage of the AC power generation device so as to be a target power generation voltage determined based on the electric load power thus generated and the rotational speed of the AC power generation device, and a current to the field adjustment device Current supply switching means for switching supply from the DC voltage V1 on the input side or the DC voltage V2 on the output side of the insulated voltage converter, the AC power generator When the generated voltage is less than or equal to a predetermined value, current is supplied to the field adjustment device by the output-side DC voltage V2, and when the generated voltage is greater than the predetermined value, the input-side DC voltage V1 A vehicle power supply device that supplies current to the field adjusting device by means of the above.   When the voltage deviation between the DC voltage V1 output from the rectifier and the voltage V2 on the output side of the voltage converter is equal to or less than a predetermined value, the step-down operation by the voltage converter is stopped and the rectifier outputs 6. The vehicle power supply device according to any one of claims 1 to 5, wherein a direct-current voltage is directly output.

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