Patent ID: 6667585
Filing Date: 2003-12-23
Classification: H05B

Abstract:
A method for fluorescent ballast and control process coupled to apply an output voltage to a fluorescent lamp load comprising steps of:selecting and providing a fluorescent ballast circuit driven by a drive signal from a drive signal generator, the fluorescent ballast circuit providing a change in its output voltage to the lamp load in response to a change in a drive signal frequency and pulse; monitoring the brightness of the lamp load with an optical detector positioned to be optically coupled to at least a ray of light from the fluorescent lamp load to develop a brightness signal characterizing the brightness of the fluorescent lamp load; comparing the brightness signal with a reference signal to develop an error signal indicating that the brightness of the lamp load is above or below a predetermined brightness level; and providing a drive frequency control signal to the drive signal generator to adjust the drive signal frequency in response to the error signal to reduce the magnitude of the error signal, wherein, the brightness of the lamp load is maintained at a predetermined level.