LED driving circuitry with variable load to control output light

Details LED driving circuitry with variable load to control output light LED driving circuitry with variable load to control output light

1998-08-31

2000-10-03

Wong, Don

Electric lamp and discharge devices: systems

With radiant energy sensitive control means

Electric switch controlled by the radiant energy responsive...

315112, 315117, 315158, 315307, G05F 100

Patent

active

061277843

ABSTRACT:
Circuitry for driving an LED array and a lamp including such circuitry. A fixed current source outputs a fixed current to an LED array. A variable load is provided in parallel to the LED array to also receive an output from the fixed current power supply. The variable load senses a condition affecting a luminous output of the LED array and varies an impedance based on this sensed condition. This variable load may typically include a thermistor or a photodetector. As the impedance of the variable load changes, current diverted from the LED to the variable load changes. Thereby, current supplied to the LED array, and thereby the intensity LED, can be controlled based on the impedance changing element in the variable load.

REFERENCES:
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patent: 5229870 (1993-07-01), Inoguchi
patent: 5406172 (1995-04-01), Bennett
patent: 5623139 (1997-04-01), Sliski
patent: 5661645 (1997-08-01), Hochstein
patent: 5783909 (1998-07-01), Hochstein
patent: 5834908 (1998-11-01), Boland et al.
"Temperature Compensation Circuit for Constant LED Intensity" Application Brief 1-012; Hewlett Packard.
"Digital Feedback Light-Emitting Diode Control" by D.C. Thomas, Jr. and W.O. Tyndall, Jr. IBM Technical Disclosure Bulletin vol. 16 No. 8 Jan. 1974, pp. 2598-2600.

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