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Transistor ladder network for driving a light emitting diode series string

  • US 8,476,837 B2
  • Filed: 07/02/2010
  • Issued: 07/02/2013
  • Est. Priority Date: 07/02/2010
  • Status: Expired due to Fees
First Claim
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1. A circuit for controlling operation of a string of light emitting diodes (LEDS), comprising:

  • a number of sections connected in series, the sections being configured for connection to a power source, wherein each section comprises;

    at least one LED;

    a variable resistive element coupled to the LED section;

    a transistor coupled to the variable resistive element; and

    a switch coupled to the LED section, the variable resistive element, and the transistor,wherein the switch with the variable resistive element and the transistor activates the LED section and controls current through the LED,wherein, when receiving power from the power source, the sections activate the LED sections in sequence throughout the series of the sections,further comprising a first resistive element coupled between the switch and the variable resistive element and a second resistive element coupled between the switch and the transistor.

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