According to one embodiment, a control section receives supply of control power from a control power supply section through a capacitive element and divides, a period of each half cycle of an alternating-current voltage into a first section, a second section, and a third section. In the first section, the control section subjects a switch section to conduction control to supply electric power to a load and stops a converting action of the control power supply section. In the second section, the control section subjects the switch section to non-conduction control to interrupt the power supply to the load and stops the converting action of the control power supply section. In the third section, the control section subjects the switch section to the non-conduction control to interrupt the power supply to the load and causes the converting action of the control power supply to operate.