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Power measurement in a two-wire load control device

  • US 9,250,669 B2
  • Filed: 03/11/2013
  • Issued: 02/02/2016
  • Est. Priority Date: 09/14/2012
  • Status: Active Grant
First Claim
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1. A two-wire load control device for controlling an amount of power delivered from an AC power source to an electrical load, the load control device comprising:

  • a controllably conductive device that operates in a non-conductive state during a first portion of a half-cycle of an alternating current (AC) waveform and in a conductive state during a second portion of the half-cycle;

    a voltage measuring circuit that measures a voltage across the two-wire load control device during the first portion of the half-cycle;

    a signal generator that generates a complementary voltage waveform that approximates a voltage across the load during the second portion of the half-cycle, wherein the complementary voltage waveform is based on the voltage measured across the two-wire load control device during the first portion of the half-cycle;

    a current measuring circuit that measures a current supplied to the load from the two-wire load control device during the second portion of the half-cycle; and

    a control circuit that computes an estimated amount of power consumed by the load based on the complementary voltage waveform and the current supplied to the load during the second portion of the half-cycle.

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