US Patent 7323828 LED current bias control using a step down regulator

Patent 7323828 was granted and assigned to Catalyst Semiconductor on January, 2008 by the United States Patent and Trademark Office.

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Is a

Patent

Patent attributes

Current Assignee

Catalyst Semiconductor

Patent Jurisdiction

United States Patent and Trademark Office

Patent Number

7323828

Date of Patent

January 29, 2008

Patent Application Number

11114516

Date Filed

April 25, 2005

Patent Primary Examiner

Douglas W Owens

Patent abstract

A step down switching regulator circuit that is particularly well-suited to drive high power LEDs includes a crossover conduction mode (XCM) control circuit that maintains operation at the crossover point between continuous conduction mode (CCM) and discontinuous conduction mode (DCM). This XCM operation provides an inductor current waveform that ramps up and down between zero and a desired maximum current. One or more comparators in the XCM control circuit can be used to control switching between the inductor current ramp up and ramp down phases. In this manner, complex feedback loop logic and PID controlled PWM signal generation logic can be avoided, and the need for external sense resistors and associated interface pins can be eliminated.