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Capacitor step-down LED driver and driving method using the same

  • US 10,356,856 B2
  • Filed: 09/03/2014
  • Issued: 07/16/2019
  • Est. Priority Date: 03/11/2013
  • Status: Active Grant
First Claim
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1. A capacitor step-down LED driver for receiving an AC power supply at an input side and generating an output voltage and an output current at an output side to drive a LED load, comprising an input capacitor, a rectifier circuit, an output capacitor, a control circuit and a switching circuit,wherein a first terminal of said input capacitor is coupled to a first terminal of said AC power supply, a second terminal of said input capacitor is coupled to a first input terminal of said rectifier circuit, and a second input terminal of said rectifier circuit is coupled to a second terminal of said AC power supply;

  • said output capacitor is coupled in parallel to said LED load;

    said switching circuit is coupled between output terminals of said rectifier circuit and said output capacitor;

    said control circuit turns on or off said switching circuit in response to said output current, and thus controls an amount of energy supplied from said input side to said output side, so as to compensate variations of said AC power supply and said input capacitor to maintain said output current to be a value of said desired driving current,wherein said switching circuit is controlled not to supply energy from said input side to said output side in a first operation state when said output current is larger than a desired driving current by circulating said energy in a loop of said AC power supply, said input capacitor and said rectifier circuit to decrease said output of current of said capacitor step-down LED driver; and

    said switching circuit is controlled to supply energy from said input side to said output side in a second operation state when said output current is less than said desired driving current to increase said output current.

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