Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2002-08-27
2004-02-10
Vu, Bao Q. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S274000, C323S303000
Reexamination Certificate
active
06690146
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to driver circuitry. The invention more specifically relates to a high efficiency LED (light emitting diode) driver.
BACKGROUND OF THE INVENTION
LEDs, and driver circuits to energize them, are well known. The brightness of an LED is directly related to the current applied. The voltage developed across an LED depends primarily upon the semiconductor design and technology used and upon manufacturing tolerances. Where multiple LEDs are used in close proximity, it is often desirable that they operate at fairly matched light output levels. Various circuits and approaches have been previously developed for achieving uniform illumination of LEDs. But these previously developed techniques have suffered from one or more disadvantages. For example, these techniques may have driver circuits operating very inefficiently. Also, the techniques may require LEDs manufactured to a close tolerance or with matched parameters established by testing. This drives up cost.
Energy efficiency is particularly important in portable devices energized by primary cells, such as the familiar alkaline “battery”.
REFERENCES:
patent: 6522558 (2003-02-01), Henry
patent: 6556067 (2003-04-01), Henry
Burgyan Lajos
Prinz Francois
Fairchild Semiconductor Corporation
Sidley Austin Brown & Wood LLP
Vu Bao Q.
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