Non-dissipative Undeland snubber for electric vehicle drive inverters using GaAs anti-parallel diodes

Many techniques have been developed over the years for reducing the switching stresses and losses in the transistor switches of DC-AC inverters. Soft-switching techniques such as resonant-pole inverters, resonant DC link inverters and quasi-resonant DC link inverters suffer from substantially increased voltage or current ratings of the devices, additional controlled switches and increased complexity of control. Conventional snubbers are simple to use, but the dissipation in the snubber results in no overall improvement in the efficiency of the inverter. The Undeland snubber with a simple energy recovery circuit combines both the simplicity of the conventional snubber while reducing the switching stresses in the switches and improving the overall efficiency of the power circuit. Experiments are conducted on single-phase 1 kVA MOSFET inverter with GaAs anti-parallel diodes and operating from a DC bus of 135 V. The results are presented for operations in the hard-switched mode as well as with the regenerative Undeland snubber in operation. It is shown that the Undeland snubber improves efficiency as compared to the hard switched mode of operation. Practical limitations and design considerations of the Undeland snubber in the presence of improved devices such as low-reverse recovery current diodes like GaAs diodes are also shown.