Patent ID: 7176658

Claim:
A system responsive to an alternating current input signal of relatively high maximum level varying voltage, for generating a regulated DC output signal having a predetermined output voltage, the system comprising: a rectifier for generating, from the input signal, a rectified DC signal having a predetermined initial maximum voltage, said initial maximum voltage being a high voltage relative to said predetermined output voltage; a regulator for generating, from the rectified DC signal, a regulated DC signal at a predetermined intermediate voltage, the predetermined intermediate voltage being a high voltage relative to said predetermined output voltage; and at least one DC to DC converter for generating, from the regulated higher voltage DC signal, the regulated DC output signal having said predetermined output voltage, the DC to DC converter including at least one switching element that tends to be subject to turn off losses, and further includes a capacitor disposed to limit the rate of change of voltage across the switching element during turn off, and a circuit for selectively discharging the capacitor to the output of the regulator, such that the capacitor is substantially fully discharged by the beginning of the next successive turn-off period, the circuit for selectively discharging the capacitor comprising an inductor, a second switching device, and a diode, the second switching device being connected in series with the inductor across the capacitor, with the diode disposed to provide a directional current path between the inductor and the output of the rectifier.