Patent ID: 8067926

Claim:
A power supply for a load control device for controlling the amount of power delivered to an electrical load from an AC power source, the load control device operable to receive an AC voltage waveform of the AC power source, the power supply operable to generate a DC voltage, the power supply comprising: an energy storage element; a controllably conductive switching circuit coupled in series electrical connection with the energy storage element for selectively charging the energy storage element to produce the DC voltage, the controllably conductive switching circuit switching to a conductive state after the magnitude of the AC voltage waveform exceeds approximately the magnitude of the DC voltage waveform during a half-cycle of the AC voltage waveform; a latching circuit coupled to the controllably conductive switching circuit, the latching circuit causing the controllably conductive switching circuit to become non-conductive in response to the magnitude of the DC voltage and in response to the amount of time that the energy storage element has been charging during the half-cycle; a first voltage-responsive current source that conducts a first current having a magnitude representative of the magnitude of the DC voltage; and a second time-responsive current source that conducts a second current having a magnitude representative of the amount of time that the energy storage element has been charging during the half-cycle, wherein the energy storage device charges for the length of a charging time period during the half-cycle, and the first and second current sources operate to maintain the length of the charging time period substantially the same from one half-cycle to the next.