Analysis of Voltage Surge in the Free-Running Transistor Inverter

The collector voltage surge in the free-running transistor inverter is investigated. In the period of commutation, the collector-emitter voltage increases sharply with a reduction in m.m.f. of the core. This surge is undesirable from the viewpoint of the reliability of transistor and the efficiency. However, since this surge makes the other transistor turn on, this phenomenon is unavoidable. The mechanism of the surge generation is unknown, so we analyze the surge voltage by using a high-frequency equivalent circuit (pi model) of transistor.