Patent ID: 7760524

Claim:
A driver circuit for use in a power supply having a rectifier coupled to generate a rectified voltage in response to a single phase AC voltage at an input of the power supply, the driver circuit comprising: a drive signal generator to generate a drive signal to be coupled to a variable impedance element, the variable impedance element to be coupled to a low voltage capacitance and to a high voltage capacitance; and a voltage sensor coupled to the drive signal generator and to be coupled to sense a voltage across the high voltage capacitance, wherein the drive circuit is to be coupled to control the variable impedance element in response to the voltage sensor such that both the low voltage capacitance and the high voltage capacitance are allowed to receive current from the input of the power supply if the voltage across the high voltage capacitance is less than a second threshold value and the low voltage capacitance is prevented from receiving current from the input of the power supply if the voltage across the high voltage capacitance is greater than a first threshold value.