Patent ID: 7466170

Claim:
A circuit, comprising: a power conversion means to convert an AC signal into a DC signal; a switching means coupled to a load and coupled to receive the DC signal from the power conversion means during normal circuit operation, wherein the switching means applies a voltage of a first polarity across the load during a first on time period and wherein the switching means applies a voltage of the opposite polarity of the first polarity during a second on time period; and sensing means coupled to the load for sensing the voltage across the load for a first sense period during the first on period and for a second sense period during the second on period, wherein the switching means is controlled to maintain a magnitude of the voltage across the load during the first on period substantially equal to the voltage across the load during the second on period; wherein the sensing means comprises a capacitor and a current charging means coupled to the capacitor for charging and discharging the capacitor.