Maximizing efficiency of battery-powered LED drivers
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United States of America Patent
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Sep 13, 2011
Grant Date -
May 14, 2009
app pub date -
Jan 20, 2009
filing date -
Apr 1, 2005
priority date (Note) -
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Abstract
An apparatus and method is provided for optimizing LED driver efficiency. The present invention offers low cost solutions for powering LEDs while minimizing overall power dissipation in devices powered by a depletable power source. Low system cost is attained using a charge pump to increase LED drive voltage level and implementing combinations of drive techniques to overcome the inefficiency of the charge pump. A switch bypasses the charge pump when depletable power source output voltage is sufficient to directly drive an LED load. At certain output voltage levels, the switch can be opened causing the charge pump to boost drive voltage. The output voltage may also be PWM modulated to drive the LED load and, at some voltages, the depletable power source may drive the LED load directly. Efficiency levels of 90-97% are attainable.
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