PURPOSE: To extend the operational range of a power supply voltage, by applying start pulse to a gate electrode of a silicon controlled rectifier element, in the power supply circuit using the silicon controlled rectifier element.

CONSTITUTION: A DC input voltage B1 is led to a DC power supply input terminal when a power supply switch 39 is turned on. When the divided and decreased voltage is higher than a switching voltage of a silicon bidirectional switching element 44', the switching element 44' turns on, the silicon controlled rectifier element 13 turns on, a DC output voltage B2 is increased and starts a horizontal output circuit 14 and the like at the rated voltage. Then, since an output of a start pulse supply circuit 26 is held to a value sufficiently lower than the gate voltage of the rectifier element 13, there exists no effect to the silicon controlled rectifier element 13.