PURPOSE: To enable automatic voltage increase from zero to a high value through a simple circuit constitution, and realize improvement of the operational performance of a high-voltage generating power source by interlocking the operation of a high-voltage generating circuit with the operation of a gain correcting circuit, and controlling the output of the said high-voltage generating circuit when the output reaches a value corresponding to the set value of a standard- voltage source.

CONSTITUTION: A standard voltage supplied from a standard-voltage source 1 is amplified with an error amplifier 2, and is applied to a gate transistor(TR4) by means of a gain correcting circuit 3. A switching circuit 6, which controls whether or not the output of the circuit 3 is used as a control source for a high- voltage generating circuit 5, is provided between the (TR4) and the circuit 5 applying high voltage to a load(L). The gain correcting circuit 3 is used to stabilize the negative feedback, and the series circuit of a diode (D) and a capacitor (C2) is connected parallel to the series circuit of a resistance (R2) and a capacitor (C1). In addition, a switching circuit 7 interlocked with the switching circuit 6 is connected parallel to the capacitor(C2). As the result, the operational performance of the high-voltage generating power source can be increased.