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Sample and hold method to achieve square-wave PWM current source for light emitting diode arrays

  • US 6,734,639 B2
  • Filed: 08/15/2001
  • Issued: 05/11/2004
  • Est. Priority Date: 08/15/2001
  • Status: Expired due to Term
First Claim
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1. An apparatus for controlling voltage and current in a switched LED array that is energized via a switched voltage converter, comprising:

  • a semiconductor switching device for connecting the LED array to a voltage biasing rail from the switched voltage converter;

    a current detecting means for generating a signal proportional to a current being conducted through the LED array during an activation time; and

    a sample and hold means for retaining the generated signal during an inactivation time.

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