Power supply device and method for detecting non-contact state of load connected to power supply device

A power supply device, comprising:

• a battery that includes rechargeable battery cells and supplies electric power to a load;
• a positive terminal contactor that is serially connected to a positive side of the battery;
• a negative terminal contactor that is serially connected to a negative side of the battery;
• and
• a control portion that determines whether the load is electrically in a connected state or a non-contact state to output sides of the positive terminal contactor and the negative terminal contactor,
• wherein the control portion comprises:
• a voltage detecting circuit that detects a capacitor voltage of a capacitor of the load, the voltage detecting circuit being connected to the capacitor at the output sides of the positive terminal contactor and the negative terminal contactor,
• a contactor controlling circuit that controls opening and closing of the positive terminal contactor and the negative terminal contactor, respectively, and
• a determination circuit that compares the capacitor voltage detected by the voltage detecting circuit with a first predetermined voltage to determine the connected state of the load to the power supply device,
• wherein the voltage detecting circuit is configured to detect the capacitor voltage with the negative terminal contractor being controlled in a closed state and the positive terminal contactor being controlled in an open state by the contactor controlling circuit at a time a start switch is turned ON, and the determination circuit is configured to determine that the load is in a normal connected state to the power supply device when the capacitor voltage is not smaller than the first predetermined voltage.