Patent ID: 7898346

Claim:
A power supply apparatus that supplies a predetermined DC voltage to an anode electrode, a cathode electrode and a first collector electrode to an Nth collector electrode of an electron tube, the power supply apparatus comprising, when N is assumed to be a positive integer: an electrical discharge switch and a first resistor that are serially connected, and that are connected between said cathode electrode and said first collector electrode; N arresters that are serially connected, and that are inserted between a ground potential and a connection node of said electrical discharge switch and said first resistor; N second resistors that are inserted between said N arresters and a second collector electrode to the Nth collector electrode and a ground potential, respectively; and an electrical discharge control circuit that turns off said electrical discharge switch at a time of normal operation of said power supply apparatus to put said electrical discharge switch in an open state, and turns on said electrical discharge switch when stopping operation of said power supply apparatus to put said electrical discharge switch in a short-circuit state.