PURPOSE: A bootstrap circuit for a high side switching device is provided to perform a charging operation without a low side drive circuit, thereby completely turning (+) side MOSFET or IGBT driving on. CONSTITUTION: An oscillation unit(11) is oscillated at a set frequency. A switching unit(12) performs a switching operation according to an oscillation frequency of the oscillation unit. An inductor(L1) performs charging/discharging operations according to a switching operation of the switching unit. A coupling condenser(C1) is operated by discharging of the inductor. A rectifying unit(13) outputs a DC component at the coupled voltage. A constant voltage unit(14) outputs a voltage of the rectifying unit by a constant voltage. A gate driving unit(15) drives a high side switching device by a voltage outputted from the rectifying unit. A level shift unit(16) shifts a voltage level of the gate driving unit.
