Abstract: A resonant recovery circuit operates to discharge switching energy losses stored in a snubber capacitor associated with each pole of an inverter to return the discharged current to the DC supply by means of an inductor coupled to the resonant recovery switch. In a multiple pole inverter, the snubber capacitors associated with each of the pole's switching devices is sequentially discharged during the clock cycle of the switching frequency. A plurality of recovery circuits may be used in a multi-phase inverter.

Abstract: A circuit for extending the operation of an electrical load after interruption of its power source. The circuit includes bulk capacitors charged by the power source and regulated to a predetermined voltage near their peak-voltage rating. The bulk capacitors are isolated from the power source capacitors during normal power source operation. When the power source is interrupted, the bulk capacitors are used to hold-up the load. The circuit obtains maximum hold-up time for a given physical bulk capacitor size, while also providing a consistent hold-up time over a range of power source voltages.