Patent ID: 8093905

Claim:
A power supply device comprising: a smoothing unit that smoothes a rectified output of an alternating-current power, the smoothing unit including a capacitor that includes a first capacitor directly subjected to a degradation diagnosis and at least one second capacitor not directly subjected to the degradation diagnosis; and a first discharge resistor connected to both ends of the first capacitor in parallel, wherein during a normal operation of the power supply device, the first capacitor and the second capacitor are connected electrically to a live line, while during the degradation diagnosis, the first capacitor is disconnected electrically from the live line, and the first capacitor and the second capacitor have life degradation characteristics such that, in a period of time until the second capacitor reaches an end of its life, a first period where an amount of change in discharge time of the first capacitor is larger than an amount of change in discharge time of the second capacitor is longer than a second period where the amount of change in discharge time of the second capacitor is larger than the amount of change in discharge time of the first capacitor.