Patent ID: 8120347

Claim:
In an AC electrical system having a source producing a sinusoidal source voltage (Vs) and an sinusoidal source current (Is), the source interconnected through an energy storage device (L 1 ) with a load (Z 1 ), and a unity power factor control circuit; a method for maintaining unity power factor, comprising the steps of: producing a sample and hold voltage (V 6 ) related to both an input voltage (V 1 ) and an output voltage (Vo) wherein the sample and hold voltage (V 6 ) maintains a constant value between pulses of a clock signal (V 5 ), that is, while the clock signal (V 5 ) is low; turning on a modulated signal (V 9 ) each time the clock signal (V 5 ) assumes the low value thereby producing a current feedback voltage (V 8 ) proportional to the source current (Is); storing energy in the energy storage device (L 1 ) while the sample and hold voltage (V 6 ) is greater than the current feedback voltage (V 8 ); delivering the source current (Is) and energy stored in the energy storage device (L 1 ) to the load (Z 1 ) each time the current feedback voltage (V 8 ) exceeds the sample and hold voltage (V 6 ); whereby controlling the amount of energy that is stored in energy storage device (L 1 ), the source voltage (Vs) and the source current (Is) are drawn into phase.