Power conversion device and power supply system using same

1. A power conversion device comprising:

a first low voltage side circuit and a first high voltage side circuit which are connected via a first transformer;

a second low voltage side circuit and a second high voltage side circuit which are connected via a second transformer; and

a control circuit configured to:

control switching timings of the first high voltage side circuit and the second high voltage side circuit such that a current difference of an input current to the first low voltage side circuit and an input current to the second low voltage side circuit during a step-up operation is reduced and becomes smaller than a predetermined value to balance the input currents, and

control the first high voltage side circuit and the second high voltage side circuit during the step-up operation such that a period for electrically short-circuiting both terminals of any one transformer of the first transformer and the second transformer at the switching timing of the first high voltage side circuit or the second high voltage side circuit is provided.

2. The power conversion device according to claim 1 , wherein

a driver circuit to output a drive signal of a switching element is included in at least one of the first low voltage side circuit and the second low voltage side circuit.

3. The power conversion device according to claim 2 , wherein

the driver circuit to output the drive signal is included in each of the first low voltage side circuit and the second low voltage side circuit, and

the driver circuit outputs the drive signal, on the basis of a control signal common to the first low voltage side circuit and the second low voltage side circuit.

4. The power conversion device according to claim 1 , wherein

at least one of the first high voltage side circuit or the second high voltage side circuit has a first switching leg in which one terminal of the first transformer is connected to a connection point of an upper arm side switching element and a lower arm side switching element and a second switching leg in which the other terminal of the first transformer is connected to a connection point of an upper arm side switching element and a lower arm side switching element, and

the at least one of the first high voltage side circuit or the second high voltage side circuit is controlled such that a period for turning on the upper arm side switching element of the first switching leg and the upper arm side switching element of the second switching leg or turning on the lower arm side switching element of the first switching leg and the lower arm side switching element of the second switching leg is provided.

5. The power conversion device according to claim 1 , wherein

the period is calculated on the basis of the current difference of the input current to the first low voltage side circuit and the input current to the second low voltage side circuit.

6. The power conversion device according to claim 1 , wherein

the first high voltage side circuit is configured using a common switching leg connected to one terminal of the first transformer and connected to one terminal of the second transformer and a first switching leg connected to the other terminal of the first transformer, and

the second high voltage side circuit is configured using the common switching leg and a second switching leg connected to the other terminal of the second transformer.

7. A power supply system comprising:

the power conversion device according to claim 1 ;

a high voltage side battery which is connected to the first high voltage side circuit and the second high voltage side circuit; and

a low voltage side battery which is connected to the first low voltage side circuit and the second low voltage side circuit,

wherein the high voltage side battery is charged with a voltage of the low voltage side battery via the power conversion device.

8. A power supply system comprising:

the power conversion device according to claim 1 ;

a high voltage side battery which is connected to the first high voltage side circuit and the second high voltage side circuit;

a low voltage side battery which is connected to the first low voltage side circuit and the second low voltage side circuit; and

a load which is connected in parallel with the high voltage side battery,

wherein a voltage of the low voltage side battery is supplied to the load via the power conversion device.

9. A power supply system according to claim 7 , wherein

when a capacity of power supplied from the low voltage side battery is smaller than a predetermined value, an operation of any one of the first low voltage side circuit and the second low voltage side circuit is stopped, and

when the capacity of the power supplied from the low voltage side battery is larger than the predetermined value, both the first low voltage side circuit and the second low voltage side circuit are operated.

10. The power conversion device according to claim 1 , wherein

at least one of the first high voltage side circuit or the second high voltage side circuit has a first switching leg in which one terminal of the first transformer is connected to a connection point of an upper arm side switching element and a lower arm side switching element and a second switching leg in which the other terminal of the first transformer is connected to a connection point of an upper arm side switching element and a lower arm side switching element, and

the at least one of the first high voltage side circuit or the second high voltage side circuit is controlled such that a period for turning on the upper arm side switching element of the first switching leg and the upper arm side switching element of the second switching leg or turning on the lower arm side switching element of the first switching leg and the lower arm side switching element of the second switching leg is provided.

11. The power conversion device according to claim 4 , wherein

the period is calculated on the basis of the current difference of the input current to the first low voltage side circuit and the input current to the second low voltage side circuit.

12. The power conversion device according to claim 1 , wherein

the period is calculated on the basis of the current difference of the input current to the first low voltage side circuit and the input current to the second low voltage side circuit.

13. A power supply system comprising:

the power conversion device according to claim 2 ;

a high voltage side battery which is connected to the first high voltage side circuit and the second high voltage side circuit; and

a low voltage side battery which is connected to the first low voltage side circuit and the second low voltage side circuit,

wherein the high voltage side battery is charged with a voltage of the low voltage side battery via the power conversion device.

14. A power supply system comprising:

the power conversion device according to claim 2 ;

a high voltage side battery which is connected to the first high voltage side circuit and the second high voltage side circuit;

a low voltage side battery which is connected to the first low voltage side circuit and the second low voltage side circuit; and

a load which is connected in parallel with the high voltage side battery,

wherein a voltage of the low voltage side battery is supplied to the load via the power conversion device.

15. A power supply system according to claim 8 , wherein

when a capacity of power supplied from the low voltage side battery is smaller than a predetermined value, an operation of any one of the first low voltage side circuit and the second low voltage side circuit is stopped, and

when the capacity of the power supplied from the low voltage side battery is larger than the predetermined value, both the first low voltage side circuit and the second low voltage side circuit are operated.