Abstract: A power supply circuit includes a regulator and a smoothing capacitor disposed at the input side of the regulator circuit for supplying power to a microcomputer included in a control system of an electric apparatus. The power supply circuit further includes a series circuit of a Zener diode and a resistor connected to the smoothing capacitor in a parallel fashion. When power supply is initiated, the node provided between the Zener diode and the resistor develops an initial reset pulse which is applied to a reset terminal of the microcomputer for initializing the microcomputer.