Direct Approach of Simultaneously Eliminating EMI-Critical Oscillations and Decreasing Switching Losses for Wide Bandgap Power Semiconductors

Most power electronic circuits naturally suffer from undesirable oscillations, which increase circuit stress and electromagnetic interference. These oscillations can, for example, arise from commutation cell resonance, and are particularly problematic in fast-switching SiC and GaN circuits. Damping these oscillations by active gate driving has been previously proposed as an alternative to limiting the switching speed or further minimizing parasitic inductance. However, for active drivers with almost unlimited degrees of freedom in the choice of gate driving profiles, fast and efficient profile optimization techniques have yet to be developed. This letter analytically determines four key measurable indicators, which help to find optimal gate signal shaping settings for an active driver. These include the device voltage gradient, as well as the gradient and overshoot level at specific points in the transient current. This optimization strategy is tested by using it to find the optimal settings for a variable-resistance active gate driver in a 400V-GaN boost converter. Measurements of switching transients and radiated electromagnetic emissions show experimentally that the proposed strategy reduces noise and switching loss at the same time. Compared to slower nonactive driving, radiated electromagnetic emissions are down by 10 dB, and losses by 6%.