Abstract: A power supply device in which an inverter circuit is supplied with power directly from a rectification circuit, the inverter circuit has a pair of switching elements connected in series with each other and connected between both ends of the rectification circuit through an impedance element, a series circuit of the impedance element, two capacitors and an inductor is connected in parallel to one of the switching elements of the inverter circuit connected to positive polarity one of the both ends of the rectification circuit, a load is connected across one of the capacitor, a valley filling circuit receives an output of the inverter circuit through a diode provided in the valley filling circuit and supplies it to a power supply capacitor provided therein and, when a DC output voltage of the rectification circuit drops, the valley filling circuit supplies power to the inverter circuit via the power supply capacitor and another diode provided therein.