Patent ID: 8547072

Claim:
A phase control apparatus for performing phase-control or reverse phase control of power that is supplied to a load connected to an alternating current power supply, comprising: a first transistor whose source or emitter is connected to one end of the alternating current power supply, and whose drain or collector is connected to one end of the load; a second transistor whose source or emitter is connected to the other end of the alternating current power supply, and whose drain or collector is connected to the other end of the load; a diode bridge that rectifies an alternating current voltage of the alternating current power supply; and a parallel circuit of a zener diode and a capacitor, wherein the parallel circuit generates a high potential relative to a potential at a negative output terminal of the diode bridge, or generates a low potential relative to a potential at a positive output terminal of the diode bridge, using an output of the diode bridge, and a potential at a control terminal of the first transistor and a potential at a control terminal of the second transistor are switched between the high potential and the potential at the negative output terminal of the diode bridge or between the low potential and the potential at the positive output terminal of the diode bridge.