Patent ID: 6583568
Filing Date: 2003-06-24
Classification: H05B,Y10S

Abstract:
A fixed frame rate method of providing drive signals to a ballast to control the brightness of a fluorescent lamp load, the method comprising the steps of:A. providing a high frequency clock signal, B. monotonically incrementing the value of a digital variable COUNT-F with the high frequency clock signals, the digital value of the variable COUNT-F COUNT-Fing from an initial value to a final value in a frame interval of fixed duration, the value of the digital number being reset to the initial value at the end of each frame interval, C. sampling an input signal and scaling the sample to form a digital input variable BRIGHT, the digital value of BRIGHT being scaled to represent a portion of the value of the range of variable COUNT-F, D. while the value of COUNT-F is incrementing monotonically from its initial value to a value equivalent to the value of the BRIGHT variable, outputing a ballast pulse of power to the lamp load with each increment of the value of the COUNT-F variable, and E. repeating steps C and D.