Unloading circuit for power switch

摘要

A power switching stage (1) is coupled to a supply (UN) and to a mains filter (2) that consists of a capacitor (4) and an inductance (3). A varistor (5) is in parallel with the filter. Coupled across this is bypass diode (6) that has a protection circuit (7) consisting of a resistor (8) and a capacitor (9). In normal operation the unloading circuit is inactive. The circuit operates when the switch opens under load and a high arcing voltage condition is produced.