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Duty factor probing of a triac-based dimmer

  • US 8,941,316 B2
  • Filed: 11/02/2011
  • Issued: 01/27/2015
  • Est. Priority Date: 08/17/2010
  • Status: Expired due to Fees
First Claim
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1. A method of determining a dimming control value of a thyristor-switched dimmer, the method comprising:

  • predicting zero-crossings of a voltage of an AC power source that supplies power to the thyristor-switched dimmer;

    probing the output of the thyristor-switched dimmer by periodically or intermittently applying a minimum conductance across the output of the thyristor-switched dimmer from a turn-on time of the thyristor-switched dimmer circuit at least until the predicting has gathered sufficient information to predict the next zero-cross time of the voltage of the AC power source;

    detecting a leading edge of a waveform of an output voltage of the thyristor-switched dimmer circuit subsequent to the next zero-cross time; and

    determining the dimming control value of the thyristor-switched dimmer from a time interval extending from the next zero-cross time of the voltage of the AC power source to the detected leading edge.

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