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Circuit for interfacing between a conventional traffic signal conflict monitor and light emitting diodes replacing a conventional incandescent bulb in the signal

  • US 6,150,771 A
  • Filed: 06/11/1997
  • Issued: 11/21/2000
  • Est. Priority Date: 06/11/1997
  • Status: Expired due to Fees
First Claim
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1. A circuit interfacing between a traffic signal'"'"'s load switch and conflict monitor and a plurality of light emitting diodes (LEDs) replacing at least one incandescent signal lamp of said traffic signal, said interface circuit being connected to an input voltage and an input current from said load switch, said interface circuit comprising:

  • a regulated current source for driving said LEDs with a regulated load current so as to control said LEDs'"'"' light intensity, said current source providing a power factor of substantially unity by switching said input current so that said input current has an envelope that is substantially the same as said input voltage, said current source being regulated by a feedback signal derived from said load current flowing through said LEDs'"'"'; and

    a sensing circuit for simulating an open filament condition to said conflict monitor when said input voltage is at a predetermined voltage level and said load current drops by at least a predetermined amount.

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