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Reference frequency from ambient light signal

  • US 9,184,698 B1
  • Filed: 03/11/2014
  • Issued: 11/10/2015
  • Est. Priority Date: 03/11/2014
  • Status: Active Grant
First Claim
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1. A system comprising:

  • an adjustable oscillator configured to generate a periodically varying output signal at an oscillator frequency, wherein the oscillator frequency is at least partially based on an input control signal;

    a light-sensitive element configured to generate an output signal indicative of an intensity of light incident on the light-sensitive element;

    a controller configured to;

    (i) receive a first input signal based on the output signal from the light-sensitive element, wherein the first input signal has a frequency based on a reference frequency at which an intensity of light incident on the light-sensitive element periodically varies;

    (ii) generate a control signal based in part on the reference frequency; and

    (iii) provide the generated control signal to the adjustable oscillator to thereby adjust the oscillator frequency; and

    a pulse generation circuit configured to generate the first input signal received by the controller, wherein the pulse generation circuit comprises a comparator configured to;

    (i) receive a voltage signal based on the output signal from the light-sensitive element; and

    (ii) output a series of voltage pulses, wherein each voltage pulse corresponds to the received voltage signal exceeding a threshold voltage.

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