Novel Solutions to Reduce the EM Emissions of Power Switching Circuits

The introduction of wide bandgap (WBG) devices in power modules has led to increased system efficiency, since those transistor switch faster. This, however, results also in increased electromagnetic emissions. In the last years, the research activity has tried to develop software techniques in order to address such an issue. Among them, the spread spectrum technique can be used, but this approach does not reduce the EM emission energy. In order to reduce the electromagnetic interference (EMI) energy, a first approach, that can be used whenever there are a pair of nodes switching opposite, consist in aligning the transition edges, reducing the common mode emissions significantly. However this approach is not sufficient, since the waveform edges are not perfectly equal and opposite, since the rising and falling time differ and some ringing can be present. To address this issue, recent investigations have shown that the switching transistors can be driven so that they behave as switches and as snubbers, simultaneously.