When a switch of a load component is turned on, current flows from a rated AC power supply to a zerocross detection circuit. In the zerocross detection circuit, zerocross points of a waveform of current are detected and input to an output control circuit. The output control circuit selects in advance a sampling pattern and inputs a signal corresponding to this sampling pattern to an SSR by counting the zerocross points. In accordance with the sampling pattern, the SSR repeats a conductive state and a non-conductive state with a cycle of the waveform of current being one unit. In the conductive state, the current flows from the rated AC power supply to the load components. In this way, the average value of the current flowed to the load components is reduced at a predetermined rate with respect to entire output of the rated AC power supply.