Patent ID: 6690122
Filing Date: 2004-02-10
Classification: H05B,Y02B

Abstract:
An electronic ballast for powering at least one lamp, comprising:an input stage for receiving a rectified mains voltage and for providing a substantially direct current (DC) output voltage, the mains voltage having a mains frequency, wherein the input stage comprises: (a) a SEPIC converter that is operated in a mode with a discontinuous current profile, the SEPIC converter including a semiconductor switch having a control electrode; and (b) a microcontroller for controlling the SEPIC converter, wherein the microcontroller is operable to; (i) sample the DC output voltage at sampling intervals that are at least as long as 1% of the period of the main frequency; and (ii) provide a signal to the control electrode of the semiconductor switch, the signal having a duty ratio that is varied in dependence on the sampled DC output voltage to provide a predetermined desired value for the DC Output voltage.