A new short circuit protection scheme for small inverters

This paper suggests an applicable new overcurrent detecting circuit for small inverters. Normally the small capacity inverter removes current sensor for low cost and miniaturization, also conducts phase current and overcurrent sensing by using current sensing resistor for Emitter of IGBT. Emitter detecting resistor has advantage of a simple circuit and underpricing. However there is a weakness that Emitter detecting resistor cannot detect overcurrent flow only thorough high side IGBT like Ground Fault. To make up for the weak point, there is a way to add high-side of DC-link to shunt resistor. However the drawback is that it is hard to accomplish inverter for miniaturization because of adding an extra insulation tab to SMPS in order for power source of detecting circuit. To compensate for above-mentioned weaknesses, this paper proposes the bootstrap power supply circuit that can operate the current detection circuit of high-side of DC-link only adding diode and capacitor without an extra tap of SPMS, and then verifies a result through a simulation.