Patent ID: 8008801

Claim:
A vehicle power supply device which is mounted on a vehicle and connected to a motor rotating with a driving wheel via an external input-output section so as to supply the motor with driving electric power during power running of the motor and to recover regenerative electric power of the motor during regeneration of the motor, the vehicle power supply device comprising: an inverter which has first and second input-output sections with the first input-output section connected to the external input-output section and which generates a driving voltage of the motor from a DC voltage, which is input to the second input-output section, and outputs the driving voltage from the first input-output section during the power running of the motor, while converting a regenerative voltage of the motor, which is input to the first input-output section, to a DC voltage and outputting the DC voltage from the second input-output section during the regeneration of the motor; a fuel cell; a capacitor connected in parallel with the fuel cell; a first bidirectional DC-DC converter which has first and second input-output sections and wherein the first input-output section is connected to the second input-output section of the inverter and the second input-output section is connected to the fuel cell and the capacitor; a secondary battery; a second bidirectional DC-DC converter which has first and second input-output sections and wherein the first input-output section is connected to the second input-output section of the inverter and the second input-output section is connected to the secondary battery; and a sensor; a voltage control means which places one of the first DC-DC converter and the second DC-DC converter in a direct connection state, detects an output voltage of the DC-DC converter placed in the direct connection state during at least one of the power running and the regeneration of the motor by the sensor and controls an output voltage of the other DC-DC converter according to analysis of the detection signal from the sensor; and a capacitor voltage detection means which detects a voltage between terminals of the capacitor, wherein the voltage control means controls the inverter so that an output voltage from the second input-output section of the inverter becomes higher than the voltage between the terminals of the capacitor by a predetermined level, which enables charging of the capacitor with the regenerative electric power of the motor, to place the first DC-DC converter in the direct connection state during the regeneration of the motor.