Patent AT-E400984-T1: [Translated] DIGITAL CONTROL FOR FLUORESCENT LAMPS

A method to control the illumination intensity of a gas discharge lamp is achieved. The method comprises, first, converting an analog lamp illumination signal into a digital lamp illumination signal. The analog lamp illumination signal is a function of the illumination intensity of a gas discharge lamp. Second, digital target signal is subtracted from the digital lamp illumination signal to create a digital error signal. Third, a digital frequency set point is adjusted from a current value to a new value based on the digital error signal. The digital frequency set point is a high resolution digital value. Fourth, the current value and the new value are averaged by a digital delta sigma modulator to create a smoothed frequency set point. The smoothed frequency set point is a medium resolution value. Finally, an oscillating voltage signal is generated with a drive frequency based on the smoothed frequency set point. The drive frequency determines the illumination intensity of the gas discharge lamp.