Patent ID: 7529107

Claim:
A circuit for powering a load, the circuit comprising: first and second AC input connections for receiving a conventional source of alternating current (AC) voltage; first and second load output connections for coupling to a load; a rectifier circuit having a pair of input connections and a pair of output connections, wherein the input connections are adapted to receive the source of AC voltage, and the rectifier circuit is operable to provide a rectified output voltage between the output connections; a DC-to-DC converter having a pair of input terminals and a pair of output terminals, wherein the input terminals are adapted to receive an input voltage, and the DC-to-DC converter is operable to provide a substantially direct current (DC) rail voltage between the output terminals; and a voltage clamping circuit coupled between the output connections of the rectifier circuit and the input terminals of the DC-to-DC converter, wherein the voltage clamping circuit is operable to prevent the input voltage provided to the input terminals of the DC-to-DC converter from exceeding a predetermined acceptable level, wherein said voltage clamping circuit comprises: first and second inputs coupled to the output connections of the rectifier circuit; first and second outputs coupled to the input terminals of the DC-to-DC converter, wherein the first input is coupled to the first output, the second input is coupled to the second output, and the second input and the second output are coupled to circuit ground; a voltage sensing circuit operatively coupled between the first and second inputs, wherein the voltage sensing circuit activates in response to a voltage signal exceeding a predetermined threshold, wherein the voltage signal is representative of the rectified output voltage; and an energy-limiting circuit coupled to the voltage sensing circuit and coupled between the first and second outputs, wherein the energy-limiting circuit is operable, in response to activation of the voltage sensing circuit, to turn on and limit the input voltage provided to the input terminals of the DC-to-DC converter to the predetermined acceptable level.