On dynamic diode characteristics and EMI performance of an inverter with Undeland snubber

In this paper, two different power diodes were modeled in SPICE and implemented in a 100kW inverter. The reverse and forward recovery characteristics of the diodes were simulated and compared with hardware measurement to verify the validity of the SPICE diode models. The diodes showed different dynamic and static performance and simulations were performed to investigate which parameters that influence the losses and EMI-performance most. The simulations showed that the conducted emissions were reduced with approximately 3dB by selecting a diode with softer dynamic characteristics on expense of increased losses. Furthermore, an Undeland snubber was implemented which resulted in a reduction of the conducted emissions, recovery of the snubber energy and reduction of the losses in the switching elements. However, the forward and reverse recovery characteristics of the snubber diodes must be considered when designing the circuit since they also have an impact on the conducted emissions and the losses in the circuit.