IGBT over voltage protection scheme in quasi resonant induction heating applications

Induction heating for domestic usage is quite popular and in some countries, it is a highly cost-sensitive product. A single IGBT (Insulated Gate Bipolar Transistor) quasi resonant power stage is the most popular topology for this application. In this paper we explain method in which the topology works reliably irrespective of widely varying input voltage, open loop operation and inconsistent utensil material. A protection scheme involving both hardware and firmware has been discussed. The protection scheme comprises of an efficient control-algorithms and the IGBT behaves as an active self-clamp. An induction cooker/heater prototype of 1.8kW rating has been developed with the proposed protection scheme. The results reveal that the scheme proposed provides an enhanced protection to the IGBT and increases the end product reliability manifold while reducing warranty costs to the manufacturer.