Patent ID: 7359221

Claim:
A power supply for use in an electronic electricity meter operable to receive and monitor a three-phase line voltage, the power supply comprising: a voltage rectifier positioned to receive the line voltage and generate a DC bus voltage; a transformer having a primary winding and a secondary winding, wherein the DC bus voltage is applied to the primary winding such that current flows through the primary winding, wherein the primary winding discharges to the secondary winding to define an output voltage of the power supply; a switch connected to the primary winding for selectively permitting and preventing the flow of current through the primary winding, wherein when the current is prevented from flowing through the primary winding, the primary winding discharges to the secondary winding; a control circuit coupled to the switch to provide a control signal to the switch to control the operation of the switch between an on and an off position; a voltage feedback circuit positioned to receive the output voltage from the secondary winding of the transformer and operable to compare the output voltage to a desired reference voltage, wherein the voltage feedback circuit prevents the flow of current through the primary winding when the output voltage exceeds the desired reference voltage; and an over voltage circuit positioned to receive the DC bus voltage and coupled to the control circuit, wherein the over voltage circuit is operable to generate an over voltage signal to the control circuit to prevent the generation of the control signal by the control circuit to prevent the flow of current through the primary winding when the DC bus voltage exceeds an upper voltage limit.