Patent ID: 6072283
Filing Date: 2000-06-06
Classification: H05B,Y02B,Y10S

Abstract:
A micro-controller-operated high intensity discharge lamp ballast system for driving a high intensity discharge lamp, comprising:a boost pre-regulator arranged to receive a DC voltage signal and a regulation control signal and to provide a high DC voltage signal having a power level controlled by said regulation control signal;an inverter means connected to the boost pre-regulator means for converting said high DC voltage signal into a high frequency FM modulated square wave voltage signal having a frequency related to a drive frequency signal input;a lamp matching network and filter arranged to receive the FM modulated square wave voltage signal from the inverter means and to provide a high frequency FM modulated sine-wave current signal for driving said high intensity discharge lamp;a lamp current and voltage sensing circuit arranged to sense a lamp voltage and a lamp current across said high intensity discharge lamp; anda micro-controller arranged to generate said drive frequency signal in accordance with a predetermined drive frequency synthesis which is periodically altered to provide an FM modulated output signal from the inverter means and which has a drive frequency which is continuously shifted about a center point;said micro-controller further arranged to receive said sensed lamp current and voltage, to calculate an average lamp power function from the sensed lamp voltage and lamp current, to compare the average lamp power function with a pre-set value to produce a comparison signal, and to produce the regulation control signal as a function of the comparison signal.