Power supply device and method for making decision as to contactor weld of power supply device

A power supply device, comprising:

• a power supply that supplies electrical power to a load;
• a first contactor that is connected between the power supply and the load, and connected to a positive electrode terminal side of the power supply;
• a second contactor that is connected between the power supply and the load, and connected to a negative electrode terminal side of the power supply;
• a voltage detection circuit that detects a first voltage between a load side of the first contactor and a power supply side of the second contactor or a second voltage between the power supply side of the first contactor and the load side of the second contactor;
• and
• a control unit that sets the first contactor and the second contactor to an open state and a closed state, wherein:
• in a state in which the electrical power from the power supply has not been supplied to the load, a voltage which is greater than zero and less than a voltage at the power supply is applied between a positive electrode and a negative electrode on the load side;
• and
• after controlling the first contactor and the second contactor to an open state, the control unit makes a decision as to whether or not one of the first contactor and the second contactor is welded based upon detection results of the voltage detection circuit.