PURPOSE: To provide an inverter type power unit which can easily be mounted on a circuit board, is reduced in size, weight, and cost, and has an leakage breaking function.

CONSTITUTION: A bridge balanced circuit composed of impedance elements R8, R9, R10, and R11 is cascade-connected to one set of output lines of the inverter circuit of this inverter type power unit and the connecting point of the resistances R10 and R11 which is one balanced point is earthed. When leakage occurs, the leaking current circulates to the connecting point of the resistances R10 and R11 through the ground and a potential difference is produced against the other balanced point. Therefore, the operation of the inverter circuit is stopped by detecting the potential difference by means of an operational amplifier 802.