PURPOSE: A power supply device is provided to supply standby power without a separate standby power circuit, thereby reducing the number of components and costs. CONSTITUTION: An input filter(11) is connected to an AC power input terminal. A discharge resistor(12) is connected to the input filter in parallel. A main rectifying unit(13) is connected to the discharge resistor. The main rectifying unit rectifies AC power. A smoothing capacitor(14) is connected to the output terminal of the main rectifying unit. A relay(100) turns the power line off between the input filter and the discharge resistor. A standby power rectifying unit(300) supplies standby power to the smoothing capacitor.
