Patent ID: 7411359
Filing Date: 2008-08-12
Classification: H05B,Y10S

Abstract:
1. Apparatus for providing dimming control of an electrical lamp of the type driven by a ballast that is provided between an AC supply and the lamp, comprising means located in series between the AC supply and the ballast for inserting an auxiliary voltage, said auxiliary voltage being out of phase with said AC supply, whereby the supply voltage is the vectorial combination of a voltage applied to the ballast and the auxiliary voltage, such that the magnitude of the voltage applied to the ballast is smaller than the magnitude of the voltage of the AC supply, and further comprising means for controlling the auxiliary voltage for varying the voltage applied to the lamp, wherein the phase of the auxiliary voltage is maintained 90 or 270 degrees out of phase with a current flowing through said apparatus, and wherein the magnitude of the auxiliary voltage is used for varying the voltage applied to the lamp.