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Methods and apparatus for increasing accuracy of RMS measurements of signals with a high crest factor

  • US 9,766,275 B2
  • Filed: 05/15/2014
  • Issued: 09/19/2017
  • Est. Priority Date: 06/04/2013
  • Status: Active Grant
First Claim
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1. An apparatus for determining a root-mean-square (RMS) voltage of an input voltage signal, comprising:

  • an amplifier to modify an amplitude of an input voltage signal, wherein the input voltage signal is a pulse width modulated signal supplied to a lamp driver;

    an amplitude detector, coupled to the amplifier, that outputs a normalized signal having an amplitude equal to an amplitude of the input voltage signal, with a longer duration of time than the input voltage signal; and

    a root-mean-square (RMS) converter, coupled to the amplitude detector, to determine the RMS voltage of the input voltage signal over the longer duration of time, wherein a bandwidth of the RMS converter includes a desired frequency region, and wherein the bandwidth of the RMS converter is smaller than a frequency range of the input voltage signal and larger than a frequency range of the normalized signal such that RMS voltage calculation error is reduced.

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