Low-inductance snubber arrays for high-power, high-bandwidth switch-mode amplifiers

This paper presents a low inductance snubber design incorporating a damped DC bus capacitance and multiple RC+RCD cells arranged in two arrays. The design suppresses transient over-voltage peaks seen at the switching transitions in hard-switched, high-frequency switch-mode circuits which are created by an unavoidable interaction between circuit parasitic inductances, IGBT turn-off current slopes and free-wheeling diode reverse recovery currents. The array arrangement allows the use of small surface-mount, ultrafast diodes by enforcing current sharing between many devices. An industrial application example is presented where the snubber design enables an increase in DC bus voltage from 200V to 400V when using 600V Si IGBTs operated at a switching frequency of 75 kHz. Simulation results are presented and compared to experimental measurements to illustrate the operating principle and effectiveness of the array design.