JP2012186970A - Power conversion device and on-vehicle power supply device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and stably generate three kinds of supply voltages in a power conversion device for supplying a plurality of loads with power stepped down from a voltage of a high voltage battery for driving a vehicle traction motor.SOLUTION: A DC voltage of a high voltage battery 1 is stepped down in a first DC/DC converter 2, which inputs a voltage V1 into a second DC/DC converter 20. The second DC/DC converter 20 has first and second capacitors 5a, 5b connected in series, first and second switching elements 3a, 3b connected in series, and an inductor 4 connected between a junction of the first and second capacitors 5a, 5b and a junction of the first and second switching elements 3a, 3b, and transfers the power between the first and second capacitors 5a, 5b to control voltages of the first and second capacitors 5a, 5b to desired divided voltages V2, V3. Supply voltages are now generated at the voltages V1, V2, V3.

Description

  The present invention relates to a power conversion device that converts DC power into DC power having a different voltage and outputs the power, and an in-vehicle power supply device including the power conversion device.

  In recent years, in addition to conventional vehicles that run only with conventional engines, electric vehicles such as hybrid vehicles that combine an engine and a motor generator and electric vehicles that run only with a motor have appeared, and the use of electric vehicles has been spreading. In the electric vehicle, in addition to the conventional low voltage battery, a high voltage battery is used to supply energy to the motor generator. Further, as vehicle electrical components, there are high-voltage loads such as heaters and air conditioner compressors, and low-voltage loads such as headlights and wipers, and the use voltages of various loads are often lower than the use voltages of motors. For this reason, the voltage of the high voltage battery is stepped down by the DC / DC converter and supplied to the load.

  In the conventional power conversion device, a high-voltage side DC output having the same voltage as the output voltage of the DC power supply and a low-voltage side DC output having a voltage lower than the output voltage of the DC power supply can be supplied. A first DC power supply having the same output voltage as the output, and a second DC power supply having an output voltage that is the difference between the high-voltage side DC output and the output voltage of the first DC power supply, connected in series; An output in which the first and second DC power supplies are connected in series is supplied as the high-voltage DC output, and the output of the first DC power supply and the second DC power supply are connected as the low-voltage DC output. An output that is stepped down by a DC-DC converter is supplied (for example, Patent Document 1).

JP 2001-136735 A (FIGS. 7 and 1)

  In the above-described conventional power converter, the voltage lower by the output voltage of the first DC power supply may be stepped down from the DC power supply. However, the DC-DC converter deals with the load power connected to the first DC power supply. Since the amount of power increases, the reduction of the power capacity of the DC-DC converter is limited. Further, two types of power supply voltages, ie, a high-voltage side DC output and a low-voltage side DC output, are obtained, and three types of power supply voltages cannot be stably obtained.

  The present invention has been made in order to solve the above-described problems, and in a power conversion device that steps down the voltage of a battery and supplies it to a plurality of loads, three types of power supply voltages can be stably supplied. An object is to obtain a highly efficient power conversion device that can be generated and has a reduced power capacity. It is a second object of the present invention to provide an in-vehicle power supply device that includes such a power conversion device and is mounted on a vehicle.

  A power converter according to the present invention is connected in series so as to divide the output voltage between a first DC / DC converter that steps down and outputs a DC voltage of a battery, and an output terminal of the first DC / DC converter. The first and second capacitors, the first and second switching elements connected in series between the output terminals, and the connection point between the first and second capacitors and the first and second switching elements A second DC / DC converter having an inductor connected to a connection point of the elements and transferring power between the first and second capacitors; the first DC / DC converter; and And a control circuit for controlling the output of the second DC / DC converter. The control circuit controls the first DC / DC converter so that the output voltage of the first DC / DC converter becomes a target voltage, and the voltages of the first and second capacitors are divided into desired voltages. The second DC / DC converter is controlled by drivingly controlling the first and second switching elements so as to obtain a voltage.

  Moreover, the vehicle-mounted power supply device by this invention is provided with the said power converter device and the said battery as a battery for driving | running | working motor drive.

  According to the present invention, in the second DC / DC converter, each voltage of the first and second capacitors that divide the battery becomes an output voltage, and three kinds of power sources are combined with the output voltage of the first DC / DC converter. Voltage can be generated stably. In addition, since the second DC / DC converter transfers the DC power of the first and second capacitors bidirectionally, the amount of power handled is extremely low with a low voltage conversion ratio. Therefore, the power capacity of the power conversion device can be greatly reduced, and the conversion efficiency can be improved and the device configuration can be effectively reduced in size. Further, since the output voltage of the first DC / DC converter is the sum of the two output voltages of the second DC / DC converter, the first and second DC / DC converters are linked to increase the conversion efficiency. Control becomes possible.

  Further, according to the present invention, it is possible to stably supply three kinds of power supply voltages, and to obtain a small and highly reliable on-vehicle power supply device.

It is a figure which shows the structure of the power converter device and vehicle-mounted power supply device by Embodiment 1 of this invention. It is a figure explaining the operation | movement of the 1st, 2nd DC / DC converter by Embodiment 2 of this invention. It is operation | movement explanatory drawing of the 1st, 2nd DC / DC converter by Embodiment 2 of this invention.

Embodiment 1 FIG.
Hereinafter, a power converter according to Embodiment 1 of the present invention and an in-vehicle power supply device including the power converter will be described with reference to the drawings.
1 is a configuration diagram of a power conversion device and an in-vehicle power supply device according to Embodiment 1 of the present invention.
As shown in FIG. 1, the main circuit of the power converter includes a first DC / DC converter 2 that steps down the voltage VA of the battery 1 and outputs a voltage V1, and steps down the voltage V1 to obtain voltages V2 and V3. The control circuit 15 controls the output of the first and second DC / DC converters 2 and 20. The in-vehicle power supply device includes a high-voltage battery 1 for driving a vehicle driving motor and a power conversion device for stepping down the voltage of the battery 1 and supplying power to the first to third loads 11 to 13. The

  The second DC / DC converter 20 includes first and second MOSFETs 3a and 3b as first and second switching elements connected in series, and first and second capacitors 5a and 5b connected in series. The inductor 4 connected between the connection point of the first and second MOSFETs 3a and 3b and the connection point of the first and second capacitors 5a and 5b, the input terminals 6a and 6b, and the output terminals 7a and 7b. , 7c. In the first and second MOSFETs 3a and 3b, diodes are connected in antiparallel, and parasitic diodes built into the elements may be used as the diodes.

The first DC / DC converter 2 steps down the voltage VA of the battery 1 input between the input terminals 2a and 2b, and outputs the voltage V1 between the output terminals 2c and 2d.
The output terminals 2c and 2d of the first DC / DC converter 2 are connected to the input terminals 6a and 6b of the second DC / DC converter 20, and the output voltage V1 of the first DC / DC converter 2 is Are input between the input terminals 6a and 6b of the DC / DC converter 20.

  In the second DC / DC converter 20, the input terminal 6b is connected to the source terminal of the first MOSFET 3a, one end of the first capacitor 5a, and the output terminal 7c, respectively, and the input terminal 6a is the drain of the second MOSFET 3b. The terminal, one end of the second capacitor 5b, and the output terminal 7a are connected. The drain terminal of the first MOSFET 3 a and the source terminal of the second MOSFET 3 b are connected to each other, and the connection point is connected to one end of the inductor 4. The other end of the inductor 4 is connected to the other end of the first capacitor 5a, the other end of the second capacitor 5b, and the output terminal 7b. The voltage V1 input between the input terminals 6a and 6b is divided by the first capacitor 5a and the second capacitor 5b, and the voltages V2 and V3 are output between the output terminals.

  The first load 11 is connected between the output terminals 2 c and 2 d of the first DC / DC converter 2. The second load 12 is connected between the output terminals 7b and 7c of the second DC / DC converter 20 which is also both terminals of the first capacitor 5a. The third load 13 is connected between the output terminals 7a and 7b of the second DC / DC converter 20 which is also both terminals of the second capacitor 5b.

Next, operation | movement of a power converter device is demonstrated below.
The first DC / DC converter 2 steps down a voltage VA from the battery 1, for example, a high voltage of 200 V to 400 V, generates a voltage V1 of, for example, 42 V, and supplies power to the first load 11. The second DC / DC converter 20 steps down the voltage V1 input from the first DC / DC converter 2, and supplies the voltages V2, V3, for example, 14V and 28V, of the first and second capacitors 5a and 5b. Generate and supply power to the second load 12 and the third load 13.

The control circuit 15 acquires the potentials of the input / output terminals 2a to 2d of the first DC / DC converter 2, detects the input voltage VA and the output voltage V1 of the first DC / DC converter 2, and detects these Based on the voltage, the first DC / DC converter 2 is controlled so that the output voltage V1 becomes the target voltage.
In addition, the control circuit 15 acquires the potentials of the input / output terminals 6a, 6b, and 7a to 7c of the second DC / DC converter 20, and the voltage V1 that is the input voltage of the second DC / DC converter 20 and The voltages V2 and V3 of the first and second capacitors 5a and 5b, which are output voltages, are detected, and gate signals to the first and second MOSFETs 3a and 3b are output based on these voltages to output the first and second capacitors 5a and 5b. The second MOSFETs 3a and 3b are driven and controlled, and the output of the second DC / DC converter 20 is controlled.
The second DC / DC converter 20 is controlled so that the voltages V2 and V3 of the first and second capacitors 5a and 5b become desired voltages. Since the sum of the voltage V2 and the voltage V3 is always equal to the voltage V1, in this case, the voltage V3 can be controlled to 28V by controlling the voltage V2 to the target voltage, for example, 14V.

  The output terminals 2c and 2d of the first DC / DC converter 2 and the input terminals 6a and 6b of the second DC / DC converter 20 may be used together, and the voltage V1 is between either one of the terminals. The voltage may be detected and used to control both the first and second DC / DC converters 2 and 20.

Details of the operation of the second DC / DC converter 20 will be described below.
The second DC / DC converter 20 operates so as to exchange power between the first and second capacitors 5a and 5b, and the voltage V2 is controlled to a target voltage.
When the voltage V2 is smaller than the target voltage, the first MOSFET 5a is turned on and off by the first control described below to transfer energy from the second capacitor 5b to the first capacitor 5a. The voltage V2 is increased.
First, when the first MOSFET 3a is turned off and the second MOSFET 3b is turned on, a current flows through a path of the second capacitor 5b-second MOSFET 3b-inductor 4, and the energy of the second capacitor 5b is changed to the inductor 4 Migrate to Next, when the second MOSFET 3b is turned off, a current flows through the path of the inductor 4-the first capacitor 5a-the diode of the first MOSFET 3a, and the energy of the inductor 4 is transferred to the first capacitor 5a. By repeating these states, energy is transferred from the second capacitor 5b to the first capacitor 5a, and the voltage V2 is controlled.

On the other hand, when the voltage V2 is larger than the target voltage, the first MOSFET 3a is turned on and off by the second control shown below, and the energy is transferred from the first capacitor 5a to the second capacitor 5b. The voltage V2 of the capacitor 5a is reduced.
First, when the second MOSFET 3b is turned off and the first MOSFET 3a is turned on, a current flows through the path of the first capacitor 5a-inductor 4-first MOSFET 3a, and the energy of the first capacitor 5a is changed to the inductor 4 Migrate to Next, when the first MOSFET 3a is turned off, a current flows through the path of the inductor 4-the diode of the second MOSFET 3b-the second capacitor 5b, and the energy of the inductor 4 is transferred to the second capacitor 5b. By repeating these states, energy is transferred from the first capacitor 5a to the second capacitor 5b, and the voltage V2 is controlled.

In the second DC / DC converter 20, the target voltage of the voltage V2 is set so that the balanced state of the divided voltage shared by the first and second capacitors 5a and 5b is maintained, that is, the voltage V2 is constant and stable. It is determined according to the second load 12 and the third load 13 so as to be in a state. Desirably, the current flowing through the second load 12 and the current flowing through the third load 13 are determined to be equal.
When the current flowing through the second load 12 and the current flowing through the third load 13 are equal, the balanced state of the divided voltages shared by the voltages V2 and V3 of the first and second capacitors 5a and 5b is maintained. If the voltage V2 is the target voltage in the equilibrium state, the second DC / DC converter 20 can output the desired voltages V2 and V3 and supply power to the second and third loads 12 and 13 in the stopped state.

  When the current flowing through the second load 12 is larger than the current flowing through the third load 13, the voltage V2 decreases and the voltage V3 increases. For this reason, energy is transferred from the second capacitor 5b to the first capacitor 5a by the first control, and the voltage V2 is controlled. When the current flowing through the second load 12 is smaller than the current flowing through the third load 13, the voltage V2 increases and the voltage V3 decreases. For this reason, energy is transferred from the first capacitor 5a to the second capacitor 5b by the second control, and the voltage V2 is controlled.

  In this way, the first and second DC / DC converters 2 and 20 can control the output voltages V1, V2, and V3 (= V1−V2) to the target voltage. Further, the power capacity handled by the second DC / DC converter 20 is only a power difference that is a power component based on the current difference between the second load 12 and the third load 13, and the power capacity can be greatly reduced. The second DC / DC converter 20 has high conversion efficiency and can promote downsizing. For this reason, the power conversion apparatus as a whole including the first and second DC / DC converters 2 and 20 also has three types using the power of the battery 1 with a small configuration that can greatly reduce the power capacity and have high power conversion efficiency. Can be generated stably. In addition, by using such a power conversion device and the battery 1, three types of power supply voltages can be stably supplied, and a small and highly reliable on-vehicle power supply device can be obtained.

  The target voltage of the voltage V2 may be calculated by the control circuit 15, but may be calculated by an external calculation device and given to the control circuit 15. Alternatively, the control circuit 15 may control the voltage V2 so as to fluctuate, detect a stable state, and control the voltage V2 at that time as the target voltage.

In the first embodiment, description has been made using MOSFETs as the first and second switching elements 3a and 3b. However, a bipolar transistor, an insulated bipolar transistor (IGBT), a silicon carbide transistor, or a wide transistor is described. The same effect can be obtained by using a MOSFET formed of a band gap semiconductor.
A wide band gap semiconductor is a semiconductor having a larger band gap than silicon, for example, silicon carbide, gallium nitride-based material, or diamond. Since the switching element formed of such a wide band gap semiconductor has high voltage resistance and high allowable current density, the switching element can be reduced in size. By using these reduced switching elements, Miniaturization of the in-vehicle power supply device can be promoted. Furthermore, since the power loss is low, the efficiency of the switching element can be increased, and the efficiency of the in-vehicle power supply device can be increased.
In addition, since switching elements made of wide band gap semiconductors have high heat resistance, it is usually possible to reduce the size of the heat sink fins of the heat sink provided in the in-vehicle power supply device and to cool the water cooling part. Further downsizing becomes possible.

  Moreover, in the said Embodiment 1, although the power converter device applied what is applied to a vehicle-mounted power supply device, it is applicable also except for vehicles, and the same effect is acquired.

Embodiment 2. FIG.
In the second embodiment, a power conversion device having a circuit configuration similar to that of the first embodiment is used, and the output voltage V1 of the first and second DC / DC converters 2 and 20 is the same as in the first embodiment. , V2, V3 (= V1-V2) are controlled to target voltages. In this case, a V2 lower limit value to a V2 upper limit value, which are a predetermined voltage range, are provided as the target voltage of the voltage V2. That is, when the voltage V2 is within the range of the V2 lower limit value to the V2 upper limit value, the second DC / DC converter 20 stops its operation. At this time, in the power converter, only the first DC / DC converter 2 operates and outputs voltages V1, V2, and V3.

Further, a voltage range (V1 lower limit value to V1 upper limit value) is set to the target voltage for the output voltage V1 of the first DC / DC converter 2 so that the output voltage V1 can be adjusted.
First, when the current balance between the second load 12 and the third load 13 is lost, and the value of the voltage V2 becomes larger than the V2 upper limit value, as shown in FIG. The output voltage V1 is adjusted so as to decrease within the voltage range from the V1 lower limit value to the V1 upper limit value. Thereby, the voltage V2 and the voltage V3 (= V1-V2) are lowered while maintaining the voltage ratio, and the voltage V2 is controlled within the V2 lower limit value to the V2 upper limit value. At this time, with the second DC / DC converter 20 stopped operating, only the first DC / DC converter 2 operates and outputs voltages V1, V2, and V3.

  Next, when the current balance between the second load 12 and the third load 13 is lost and the value of the voltage V2 becomes smaller than the V2 lower limit value, as shown in FIG. 3, the first DC / DC converter 2 Is adjusted so as to increase within the voltage range of the V1 lower limit value to the V1 upper limit value. Thus, the voltage V2 and the voltage V3 (= V1−V2) are increased while maintaining the voltage ratio, and the voltage V2 is controlled within the V2 lower limit value to the V2 upper limit value. At this time, with the second DC / DC converter 20 stopped operating, only the first DC / DC converter 2 operates and outputs voltages V1, V2, and V3.

  Thus, the control circuit 15 increases or decreases the output voltage V1 of the first DC / DC converter 2 within the voltage range of the target voltage so that the voltage V2 falls within the range of the V2 lower limit value to the V2 upper limit value. adjust. Thereby, the conversion loss in the 2nd DC / DC converter 20 is lost, and the conversion efficiency of the whole power converter device improves.

Even if the output voltage V1 of the first DC / DC converter 2 is adjusted to be increased or decreased within the voltage range from the V1 lower limit value to the V1 upper limit value, the voltage V2 does not fall within the V2 lower limit value to the V2 upper limit value. If not, the second DC / DC converter 20 is operated to control the voltage V2 to fall within the V2 lower limit value to the V2 upper limit value, as in the first embodiment.
That is, the control circuit 15 adjusts the output voltage of the first DC / DC converter 2 by increasing or decreasing it within the voltage range of the target voltage so that the voltage V2 approaches the V2 lower limit value to the V2 upper limit value, The second DC / DC converter 20 is operated so that the voltage V2 falls within the V2 lower limit value to the V2 upper limit value by power transfer between the first and second capacitors 5a and 5b. Also in this case, the voltage ratio and the amount of power converted by the second DC / DC converter 20 can be reduced as compared with those before the adjustment of the output voltage V1, and the conversion efficiency can be improved.

The V2 lower limit value to the V2 upper limit value, which are predetermined voltage ranges, are provided as the target voltage of the voltage V2, and the voltage V2 falls within the range of the V2 lower limit value to the V2 upper limit value, or the V2 lower limit value to the V2 upper limit value. Although it has been shown that the voltage V1 is adjusted to be increased or decreased within the voltage range of the target voltage so as to approach the value, the same control can be performed on the voltage V3 instead of the voltage V2. That is, a predetermined voltage range V3 lower limit value to V3 upper limit value is provided as a target voltage of the voltage V3 so that the voltage V3 falls within the range of V3 lower limit value to V3 upper limit value, or V3 lower limit value to V3 upper limit value. The voltage V1 is adjusted by increasing / decreasing within the voltage range of the target voltage so as to approach the inside.
Furthermore, instead of the voltage V2, both the voltage V2 and the voltage V3 can be used. That is, the V2 lower limit value to the V2 upper limit value and the V3 lower limit value to the V3 upper limit value, which are predetermined voltage ranges, are set as the target voltages of the voltages V2 and V3 so that the voltage V2 falls within the range of the V2 lower limit value to the V2 upper limit value. In addition, the voltage V1 is adjusted by increasing / decreasing within the voltage range of the target voltage so that the voltage V3 falls within the range of the V3 lower limit value to the V3 upper limit value. Alternatively, the voltage V1 is adjusted by increasing / decreasing within the voltage range of the target voltage so as to approach the V2 lower limit value to the V2 upper limit value and to approach the V3 lower limit value to the V3 upper limit value.

  In this embodiment, the same effect as that of the first embodiment can be obtained, the amount of power handled by the second DC / DC converter 20 can be further reduced, and further high efficiency and downsizing can be promoted. And the vehicle-mounted power supply device using the same is obtained.

Embodiment 3 FIG.
In the third embodiment, a power conversion device having a circuit configuration similar to that in the first embodiment is used, and the output voltage V1 of the first and second DC / DC converters 2 and 20 is the same as in the first embodiment. , V2, V3 (= V1-V2) are controlled to target voltages. In this case, it is assumed that the second load 12 and the third load 13 are driven with an equivalent voltage, for example, 14V. The first load 11 is driven with a voltage 28 V that is twice that of the second and third loads 12 and 13. That is, in the second DC / DC converter 20, the voltage V2 and the voltage V3 are controlled to be equal to 14V, and in the first DC / DC converter 2, the output voltage V1 is controlled to 28V, which is twice the voltage V2.

  In this embodiment, a plurality of load devices driven with an equivalent voltage (14 V) are distributed into two groups, one of which is the second load 12 and the output terminals 7 b and 7 c of the second DC / DC converter 20. The other is connected between the output terminals 7 a and 7 b of the second DC / DC converter 20 as the third load 13. At this time, the plurality of load devices are distributed and arranged so that the total current flowing through each load device that is the second load 12 and the total current flowing through each load device that is the third load 13 are close to each other. The

  Also in this embodiment, as in the first embodiment, the power capacity handled by the second DC / DC converter 20 is only the power difference based on the current difference between the second load 12 and the third load 13. It is. Therefore, as described above, the second DC / DC converter is provided by distributing the second and third loads 12 and 13 so that the currents of the second load 12 and the third load 13 are balanced. Thus, a power conversion device that can reduce the amount of power handled by 20 and can promote higher efficiency and miniaturization, and an in-vehicle power supply device using the same can be obtained.

  In this case as well, the second embodiment can be applied. In this case, the voltage V2 and the voltage V3 are controlled within the same voltage range, and may not be the same voltage.

Embodiment 4 FIG.
In the fourth embodiment, a power conversion device having the same circuit configuration as that of the first embodiment is used, and the output voltage V1 of the first and second DC / DC converters 2 and 20 is the same as in the first embodiment. , V2, V3 (= V1-V2) are controlled to target voltages.
In this case, a plurality of load devices driven with an equivalent voltage (for example, 14 V) are connected between the output terminals 7 b and 7 c of the second DC / DC converter 20 as the second load 12. One of the plurality of load devices is used as a second battery 12a (not shown), and power is supplied to the other load device 12b (not shown) from the second battery 12a. A lead battery or the like that outputs a voltage of 14 V is used for the second battery 12a, and a load that requires high reliability, such as a brake pump or a headlight, is connected as the other load device 12b.

During normal operation, the first and second DC / DC converters 2 and 20 operate in the same manner as in the first embodiment, and step down the voltage of the battery 1 to supply power to the first to third loads 11 to 13. To do. The second load 12 is supplied with power from the first capacitor 5a, and the second battery 12a is also charged as one of the second loads 12 at normal times.
If the first DC / DC converter 2 or the second DC / DC converter 20 fails or the battery 1 fails, the second load 12 is not normally supplied with power from the first capacitor 5a. Then, power is supplied from the second battery 12a to the load device 12b, which is another second load 12. Thereby, it is possible to continuously supply power to the load device 12b requiring high reliability even when the power conversion device is abnormal, and the reliability of the power conversion device and the in-vehicle power supply device is improved.

  In the above-described embodiment, the configuration in which the load device 12b having a high reliability requirement and the second battery 12a serving as an auxiliary power source of the load device 12b are arranged as the second load 12 is described. Instead of the second load 12, the third load 13 may have the same configuration.

1 battery, 2 first DC / DC converter, 3a first MOSFET,
3b second MOSFET, 4 inductor, 5a first capacitor,
5b second capacitor, 11 first load, 12 second load, 13 third load,
15 control circuit, 20 second DC / DC converter, VA battery voltage,
V1 output voltage of the first DC / DC converter, V2 voltage of the first capacitor,
V3 Voltage of the second capacitor.

Claims (10)

A first DC / DC converter that steps down and outputs a DC voltage of the battery;
First and second capacitors connected in series so as to divide the output voltage between output terminals of the first DC / DC converter, and first and second switching elements connected in series between the output terminals And an inductor connected between the connection point of the first and second capacitors and the connection point of the first and second switching elements, and between the first and second capacitors. A second DC / DC converter that exchanges power with each other;
A control circuit for controlling the output of the first DC / DC converter and the second DC / DC converter,
The control circuit controls the first DC / DC converter so that the output voltage of the first DC / DC converter becomes a target voltage, and the voltages of the first and second capacitors are divided into desired voltages. A power converter that controls the second DC / DC converter by drivingly controlling the first and second switching elements so as to be a voltage. A predetermined voltage range is provided as the desired divided voltage,
The control circuit stops the operation of the second DC / DC converter and operates only the first DC / DC converter when the voltages of the first and second capacitors are within the predetermined voltage range. The power converter according to claim 1, wherein: The target voltage of the first DC / DC converter has a voltage range;
The control circuit increases or decreases the output voltage of the first DC / DC converter within the voltage range of the target voltage so that the voltages of the first and second capacitors are within the predetermined voltage range. The power conversion device according to claim 2, wherein the power conversion device is adjusted. When the voltage of the first and second capacitors does not fall within the predetermined voltage range even when the control circuit operates only the first DC / DC converter, the voltage of the first and second capacitors Is adjusted by increasing / decreasing the output voltage of the first DC / DC converter within the voltage range of the target voltage, and the power between the first and second capacitors is adjusted so that the voltage approaches the predetermined voltage range. 4. The power converter according to claim 3, wherein the second DC / DC converter is operated so that the voltages of the first and second capacitors fall within the predetermined voltage range by transfer. The output power of the first DC / DC converter is supplied to a first load, and the direct-current power of the first and second capacitors of the second DC / DC converter is supplied to the second and third loads. It supplies, The power converter device of any one of Claims 1-4 characterized by the above-mentioned. The desired divided voltage of the first and second capacitors is determined according to the second and third loads so that an equilibrium state is maintained at the divided voltage. The power conversion device according to claim 5. A plurality of load devices having the same power supply voltage are distributed and arranged in two groups as the second and third loads,
The distribution of the two groups is determined so that the total current flowing through each load device as the second load approaches the total current flowing through each load device as the third load,
The control circuit sets the target voltage of the first DC / DC converter to twice the power supply voltage of the load devices and the desired divided voltage of the first and second capacitors to the power supply voltage. The power converter according to claim 6, wherein the first and second DC / DC converters are controlled. A plurality of load devices having the same power supply voltage are arranged as one of the second and third loads, and one of the plurality of load devices supplies power to other load devices as an auxiliary power source. It was set as the battery, The power converter device of any one of Claims 5-7 characterized by the above-mentioned. 9. The first and second switching elements in the second DC / DC converter are formed of a wide band gap semiconductor having a wider band gap than silicon. The power converter device described in 1. An in-vehicle power supply device comprising: the power conversion device according to any one of claims 1 to 9; and the battery as a battery for driving a traveling motor.

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