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United States Patent ( 10 ) Patent No . : US 7 , 649 , 326 B 2
| Content Provider | Semantic Scholar |
|---|---|
| Author | Vu, David Hung Brady, Wade James |
| Copyright Year | 2017 |
| Abstract | (21) Appl. No.: 11/691,.687 A current Source generates, with high efficiency, a current that (22) Filed: Mar 27, 2007 is Substantially constant over a wide range of output Voltages. This current is injected into the first end of a series-connected (65) Prior Publication Data string of LEDs, with the second end of the string connected through a resistor to ground. The Voltage developed across US 2007/O257623 A1 Nov. 8, 2007 this resistor, which is a measure of current flow in the series O O string, is fed back to the current source, wherein feedback Related U.S. Application Data maintains nearly constant current output over a wide range of (60) Provisional application No. 60/743,804, filed on Mar. output voltages. A field effect transistor (FET) is placed in 27, 2006. parallel with each LED in the string. A level shiftgate driver couples a pulse width modulated control signal to the gate of (51) Int. Cl. each FET. With the FET being coupled across a particular H05B 3700 (2006.01) LED, the LED can be bypassed when the FET is actuated or (52) U.S. Cl. ................... 315/291; 315/185R, 315/192 receive current when the FET is deactuated. By modulating 315/193 the duty cycle of each FET, the brightness of each associated (58) Field of Classification Search ................. 315,291, LED may be varied smoothly over its full range. 315/307, 185R, 192, 193 See application file for complete search history. 10 Claims, 4 Drawing Sheets |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://patentimages.storage.googleapis.com/d3/35/92/9de0bbc80e860c/US7649326.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Patent |
