Patent ID: 6285139
Filing Date: 2001-09-04
Classification: G01R,H05B

Abstract:
A substantially constant intensity light source comprising:a) a controllable dc voltage and current source having first and second terminals;b) a non-linear light-emitting load connected between the first and second terminals and supplied with dc voltage and current from the controllable dc voltage and current source;c) a current sensor circuit connected in series with the non-linear light-emitting load between said first and second terminals, 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; andd) a voltage and current control feedback circuit connected between said current sensor circuit and said controllable dc voltage and current source and through which the dc voltage and current source is controlled 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.