Controller for dc-dc converter and dc-dc converter

1. A controller for a DC-DC converter mounted on a vehicle, the DC-DC converter including:

a bidirectional DC-DC converter that is connected between a capacitor for pre-charging connected to a first battery and a second battery differing from the first battery and can perform bidirectional output; and

a unidirectional DC-DC converter that is connected in parallel with the bidirectional DC-DC converter and can perform output in one direction to a side of the second battery,

the controller being configured to during activation of a vehicle:

actuate the bidirectional DC-DC converter to start pre-charging the capacitor by using power of the second battery; and

start actuating the unidirectional DC-DC converter later than initiation of the actuation of the bidirectional DC-DC converter.

2. The controller according to claim 1 , wherein the controller is configured to:

after a specified time elapses after starting actuating the bidirectional DC-DC converter, start actuating the unidirectional DC-DC converter.

3. The controller according to claim 2 , wherein

the specified time is set based on a time required until the pre-charging of the capacitor is completed.

4. The controller according to claim 1 , wherein the controller is configured to:

detect completion of the pre-charging of the capacitor after starting actuating after the bidirectional DC-DC converter; and

start actuating the unidirectional DC-DC converter after detection of completion of the pre-charging.

5. The controller according to claim 4 , wherein

the controller is configured to determine that the pre-charging of the capacitor is completed when a voltage of the capacitor acquired from the bidirectional DC-DC converter is equal to or higher than a specified voltage value.

6. The controller according to claim 4 , wherein

the controller is configured to determine that the pre-charging of the capacitor is completed when receiving specified notification that is based on a voltage of the capacitor from the bidirectional DC-DC converter.

7. The controller according to claim 4 , wherein

the controller is configured to acquire a voltage of the capacitor and, if the acquired voltage is equal to or higher than a specified voltage value, determine that the pre-charging of the capacitor is completed.

8. The controller according to claim 1 , wherein

the capacitor is connected to the first battery via a relay, and

the controller is configured to:

actuate the bidirectional DC-DC converter in a disconnected state of the relay during the activation of the vehicle so as to start pre-charging the capacitor by using the power of the second battery; and

after starting actuating the bidirectional DC-DC converter and the relay is closed, start actuating the unidirectional DC-DC converter.

9. A unidirectional DC-DC converter configured to:

be connected between a primary side and a secondary side of a vehicle;

perform unidirectional output from the primary side to the secondary side;

be connected in parallel with a bidirectional DC-DC converter configured to perform bidirectional output, the bidirectional DC-DC converter being configured to:

monitor a current flowing from the primary side in a direction toward the secondary side;

perform output when the monitored current is equal to or larger than a specified current value; and

stop the output when the monitored current is smaller than the specified current value; and

during activation of the vehicle, actuate later than initiation of actuation of the bidirectional DC-DC converter.

10. The unidirectional DC-DC converter according to claim 9 , wherein

the unidirectional DC-DC converter is configured to monitor the current by a current sensor that is provided on the secondary side of the vehicle.