The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 09, 2003
Filed:
Feb. 26, 1999
Lowell F. Bohn, Jr., Boulder, CO (US);
Douglas J. McKnight, Boulder, CO (US);
Three-Five Systems, Inc., Tempe, AZ (US);
Abstract
A drive circuit for a time sequential color LED based display device allows the overall brightness of a display device to be adjusted without affecting the color balance. The circuit includes a boost switching converter, which provides constant power to each of a plurality of different colored LEDs associated with a pixel, independent of the forward voltage across each LED. The boost switching converter receives a pulse width modulated drive signal for activating each LED, when enabled, during a frame. The on-time of the drive signal varies during each frame according to which LED is to be activated at a particular point in time, to provide the appropriate power to the LED. The LEDs are enabled sequentially during a frame by separate enable signals. The cathode of each LED is connected to a positive power supply voltage when the LED is enabled.