Patent ID: 7042170

Claim:
A ballast for a gas discharge lamp comprising: a switching section generating an AC drive current for driving a gas discharge lamp; a voltage controlled oscillator (VCO) supplying switching signals to the switching section to control the switching frequency of the switching section; a VCO control logic circuit supplying a VCO control signal to the VCO to control the frequencies of the switching signals supplied by the VCO in response to a lamp current feedback signal and a lamp current control signal; a signal conditioner generating said lamp current control signal such that the lamp current control signal has a voltage corresponding to a pulse width of a pulse width modulated signal received by the signal conditioner; and a microcontroller providing said pulse width modulated signal to the VCO control logic circuit, wherein the microcontroller controls the pulse width of the pulse width modulated signal to control the drive current supplied by the switching section and wherein the microcontroller controls dimming of a lamp coupled to the ballast by producing a pulse width modulated signal that increases the frequencies of the VCO switching signals to dim the lamp and produces a pulse width modulated signal that decreases the frequencies of the VCO switching signals to brighten the lamp.