Patent ID: 7218061

Claim:
A circuit for producing a control signal for the purpose of dimming at least one lamp, the circuit comprising: a device for receiving an input voltage and a dimming input value, and for providing an output voltage having a modified phase gating angle, wherein the device is operable to modify the phase gating angle in dependence upon the dimming input value; a rectifier circuit for receiving the output voltage from the device and for providing a rectified version of the output voltage; a control output at which a control signal is provided; an amplitude detection device coupled to the rectifier circuit, wherein the amplitude detection device is operable to detect the amplitude of the input voltage and to provide a predeterminable voltage in dependence upon the amplitude of the input voltage; and a comparison device coupled to the rectifier circuit, the amplitude detection device, and the control output, wherein the comparison device is operable to: (i) compare the rectified output voltage with the predeterminable voltage; and (ii) provide the control signal in dependence upon the phase gating angle of the output voltage, wherein the control signal has an amplitude that is substantially independent of the magnitude of the input voltage.