Auxiliary voltage snubber circuit

摘要

In an inverter comprising power transistors selectively switched on and off to supply a predetermined current waveform to an inductive load, including a standard RC voltage snubber for suppressing load generated voltage surges during turn-off transitions of the switching transistors, an auxiliary snubber is connected across the load to provide snubbing at the start of the turn-off transitions when the conventional voltage snubber is inoperative due to an inherent snubber time constant. The auxiliary snubber comprises a grounded capacitor that is maintained charged directly from the voltage supply. The output of the capacitor is connected to the load through an SCR that is gated on during the on periods of the switching transistors during normal operation. The output voltage is equal to the auxiliary snubber capacitor voltage during normal operation so that there is no current flow through the SCR. During a load current overload, the switching transistors are turned off. Because the output voltage during overload is less than the auxiliary snubber capacitor voltage, the capacitor immediately discharges into the load to supply the overload current.