Patent ID: 8547029

Claim:
A dimming ballast comprising: a rectifier to receive an alternating current (AC) voltage signal and produce a rectified voltage signal therefrom; a power factor correction circuit to receive the rectified voltage signal and to provide a corrected voltage signal; an inverter circuit to receive the corrected voltage signal and to provide a lamp current to energize a lamp; a dim interface to receive an input indicative of a selected lighting level; a control circuit connected to the dim interface to generate a pulse-width-modulated signal having a duty cycle corresponding to the selected lighting level; a switching network connected to the control circuit to receive the pulse-width-modulated signal, the switching network having a conductive state and a non-conductive state, wherein the switching network operates between the conductive state and the non-conductive state as a function of the pulse-width-modulated signal; and an impedance device connected across the switching network and configured to connect in series with the lamp so that the impedance device receives the lamp current when the switching network is operating in the non-conductive state and the lamp current bypasses the impedance device when the switching network is operating in the conductive state, resulting in the dimming of the lamp to the selected lighting level.