Optimisation of the reverse conducting IGBT for zero-voltage switching applications such as induction cookers

The reverse conducting-IGBT (RC-IGBT) is a well suited device for soft switching applications, that is, zero voltage switching (ZVS). However, standard RC-IGBTs are optimised for hard switching, which shows different switching waveforms compared with soft switching. In this study, the optimisation of the RC-IGBT is described for soft switching applications using the example of an induction cooker. The investigated induction cooker is implemented by using the single-ended quasi-resonant topology. Simulations show that main losses of the induction cooker occur in the induction coil and the RC-IGBT (power switch). The performance of the coil can be improved mainly by minimising the coil resistance. The IGBT-optimisation is based on the reduction of tail current in the soft switching mode. The IGBT thickness is decreased and the local lifetime is used to achieve lower tail current. A reduction of the overall losses by 30% is achievable. As a result, the cooling system of the IGBT can be smaller and cheaper.