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Driving circuit for LED lamp

  • US 8,368,322 B2
  • Filed: 02/18/2011
  • Issued: 02/05/2013
  • Est. Priority Date: 06/22/2010
  • Status: Expired due to Fees
First Claim
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1. A driving circuit for a light-emitting diode (LED) lamp comprising no more than 4 strings each having an input and an output terminals and comprising a plurality of LEDs coupled in series between the input and the output terminals, the driving circuit for receiving an on-off control signal and a dimming control signal and outputting a direct-current (DC) voltage of no more than 70 volts to the input terminals of the strings, the driving circuit comprising:

  • a plurality of diodes, each having an anode terminal coupled to the output terminal of a corresponding string and a cathode terminal;

    an overvoltage protection circuit, coupled to the cathode terminals of the diodes, for outputting an overvoltage control signal when a voltage at the output terminal of one of the strings is greater than a threshold voltage;

    a plurality of constant current circuits, each coupled between the output terminal of a corresponding string and ground, the on-off control signal for controlling whether the constant current circuits work or not so as to control whether the LED lamp works or not, the dimming control signal for controlling a duty cycle of working of the constant current circuits so as to control a brightness of the LED lamp; and

    a switch for forcing the on-off control signal to control the constant current circuits not to work when receiving the overvoltage control signal.

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