Ultra-High Frequent Switching with GaN-HEMTs using the Coss-Capacitances as non-dissipative Snubbers

Inhalt:
The intent of building high efficient and very compact buck-converters with wide-band-gap transistors in a classic hard-switching operation is limited by the losses arising from dissipative reloading of the output capacitors Coss. The switching cycle of a 650V GaN-HEMT half-bridge is analyzed in terms of the Coss-related effects. A linearized model serves for deriving the relations and explaining how the Coss can be deployed for minimizing the losses. This is achieved by using Coss as an integrated non-dissipative snubber, providing soft switching for the internal transistor channel. EMI-measurements at 1MHz switching frequency are finally showing the reduction of radiated emissions when using soft-switching mode.