Power supply device and electric power steering device including power supply device

A power supply device comprising:

• a main power supply unit that is capable of supplying power to a load;
• an auxiliary power supply unit that is connected to the main power supply unit and is capable of supplying charged power to the load;
• a booster that is connected to the main power supply unit in parallel to the auxiliary power supply unit and is capable of boosting a voltage supplied from the main power supply unit and applying a resulting boosted voltage to the auxiliary power supply unit;
• a circuit switching unit that is interposed between the main power supply unit and the load and closes one of a first connection circuit and a second connection circuit, the first connection circuit extending from the main power supply unit to the load, the second connection circuit extending from the main power supply unit to the load via the auxiliary power supply unit;
• and
• a controller that performs switching control on the circuit switching unit;
• a first open/close unit that is interposed between the booster and the auxiliary power supply unit, and opens or closes a first contact provided on a path extending from the booster to the auxiliary power supply unit;
• and
• a second open/close unit that is interposed between the circuit switching unit and the auxiliary power supply unit, and opens or closes a second contact provided on a path extending from the circuit switching unit to the auxiliary power supply unit, wherein
• the controller obtains information regarding a magnitude of power required by the load and, in a case where the magnitude of the power required by the load and indicated by the obtained information exceeds a predetermined first threshold, performs switching control on the circuit switching unit so as to close the second connection circuit and controls the second open/close unit to close the second contact, and
• the controller controls the first open/close unit so as to close the first contact in a case where a magnitude of the charged power of the auxiliary power supply unit is smaller than a predetermined second threshold.