Non-linear light-emitting load current control

A method for keeping the intensity of a light source substantially constant, comprising:

• a) supplying from a controllable dc voltage and current source a dc voltage and current to a non-linear light-emitting load;
• b) supplying at least a portion of the current through said non-linear light-emitting load to a current sensor circuit having an impedance varying with a condition of operation of the light-emitting load, whereby the variable impedance produces a variable current-representative signal;
• and
• c) feedback controlling said dc voltage and current in relation to the variable current-representative signal to adjust the dc voltage and current to amplitudes that keep the light intensity produced by the light source substantially constant.

A substantially constant intensity light source comprising:

• a) a non-linear light-emitting load;
• b) a controllable dc voltage and current source for supplying the non-linear light-emitting load with dc voltage and current;
• c) a current sensor circuit connected in series with the non-linear light-emitting load and the controllable dc voltage and current source, the current sensor circuit having an impedance varying with a condition of operation of the light-emitting load and being supplied with at least a portion of the current through said non-linear light-emitting load, whereby the variable impedance produces a variable current-representative signal;
• and
• d) a voltage and current control feedback circuit connected between said current sensor circuit and said controllable dc voltage and current source for controlling the dc voltage and current source in relation to the variable current-representative signal to thereby adjust the dc voltage and current to amplitudes that keep the light intensity produced by the light source substantially constant.