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Maintaining LED luminous intensity

  • US 5,783,909 A
  • Filed: 01/10/1997
  • Issued: 07/21/1998
  • Est. Priority Date: 01/10/1997
  • Status: Expired due to Term
First Claim
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1. A circuit for maintaining the luminous output of a light emitting diode, said circuit comprising:

  • at least one light emitting diode (LED) (12) for producing a luminous output;

    a sensor (22,24) for sensing a condition proportional to said luminous output of said LED (12) and for producing a luminous output signal;

    a power supply (16) electrically connected to said LED (12) for supplying ON/OFF pulses of electrical energy to produce the luminous output of said LED (12); and

    said power supply (16) including a switching device responsive to said luminous output signal for adjusting the electrical energy supplied by said pulses per unit of time to adjust the average of said current passing through said LED (12) to maintain the luminous output of said LED (12) at a predetermined level.

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