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Off line LED driver with integrated synthesized digital optical feedback

  • US 7,598,685 B1
  • Filed: 09/19/2005
  • Issued: 10/06/2009
  • Est. Priority Date: 09/20/2004
  • Status: Active Grant
First Claim
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1. An off-line driver for powering a plurality of light emitting diodes, the off-line driver comprising:

  • a power switch;

    an AC bridge, a first terminal of the AC bridge coupled to a first terminal of the power switch;

    a magnetic inductor, a first terminal of the magnetic inductor coupled to a second terminal of the AC bridge and couplable through an anode of a rectifier to the plurality of light emitting diodes, and a second terminal of the magnetic inductor couplable to a second terminal of the power switch;

    the rectifier, a cathode of the rectifier couplable to the plurality of light emitting diodes; and

    a regulator, comprising a voltage sense, an error amplifier, an integrator, a comparator, a latch, a switch driver, and a first current sense, the voltage sense couplable through the rectifier or the current sense to the plurality of light emitting diodes, the current sense coupled to the second terminal of the power switch and couplable to the plurality of light emitting diodes;

    the error amplifier comprising a negative terminal coupled to the current sense and a positive terminal coupled to a combination of a customer set signal and an output signal of an optical model of the plurality of light emitting diodes;

    the integrator coupled to a reset switch and having an input terminal coupled to the voltage sense, the integrator integrating only during an on-time of the power switch;

    the comparator comprising a first terminal coupled to an output of the error amplifier and a second terminal coupled to an output of the integrator;

    the latch comprising a set terminal coupled to an oscillator and a reset terminal coupled to an output of the comparator; and

    the switch driver coupled to an output of the latch.

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