Patent ID: 8174197

Claim:
A light source comprising: a controllable power source for supplying power to a non-linear light-emitting load; a current sensing circuit connected to the non-linear light-emitting load that generates a current representative signal representing the current flowing through the non-linear light-emitting load; a voltage sensing circuit connected to the non-linear light-emitting load that generates a voltage representative signal representing the voltage across the non-linear light-emitting load; a power sensing circuit connected to the current and voltage sensing circuits that receives the current and voltage representative signals and determines the power consumption of the light-emitting load and generates a power-representative signal; and a power feedback control circuit connected between the power sensing circuit and the controllable power source through which the power source is controlled in relation to the power-representative signal to maintain the power consumption of the light source substantially constant, wherein the power feedback control circuit comprises: a comparison circuit having a first input for receiving the power-representative signal, a second input for receiving a fixed power-representative reference signal, and an output for producing a comparison-representative signal representative of a comparison between the power-representative signal and the fixed power-representative reference signal; and a controller through which the power source is controlled in relation to the comparison-representative signal to adjust the output of the power supply such that the power consumption and light intensity produced by the light source are substantially constant.