Patent ID: 6704183
Filing Date: 2004-03-09
Classification: H02H

Abstract:
A bias circuit for light emitting diodes comprising:a switch, connected to power, having an input; a light emitting diode connected to the switch; two bias current legs, electrically connected in parallel, interposing the light emitting diode and ground, each bias current leg including, a current-sensing resistor connected to the light emitting diode; and a current magnifying circuit, connected to the current-sensing resistor; a first comparator, having a negative input connected to the input of the bias current legs and a positive input receives a low DC voltage signal; a second comparator, having a positive input connected to one of the two bias current legs and a negative input connected to the other of the two bias current legs; and a logic OR gate, having an output connected to the input of the switch digital circuit, receiving an output from the first and second comparators.