Active clamping on series connected free-wheel diodes through active voltage control

This paper presents an active voltage control technique, for series connected freewheel diodes in bridge legs, which suppresses the oscillation due to diode snap recovery, and clamps the overshoot sustained during reverse recovery. The need to utilise passive snubbers with this active voltage control technique to overcome the shortcoming of the active clamping, is analysed. This technique allows active balancing of the reverse voltage sharing among series connected free-wheel diodes. Experimental results are presented for the suppression of the oscillation seen by the free-wheeling diodes and the active clamping of the overshoot voltage with and without passive snubbers.