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Sample and hold time stamp for sensing zero crossing of back electromotive force in 3-phase brushless DC motors

  • US 8,030,867 B1
  • Filed: 07/29/2006
  • Issued: 10/04/2011
  • Est. Priority Date: 07/29/2006
  • Status: Expired due to Fees
First Claim
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1. A method comprising:

  • (a) sampling a first phase voltage at a first time;

    (b) storing the first phase voltage and an associated first time stamp, wherein the first time stamp indicates the first time;

    (c) sampling a second phase voltage at a second time;

    (d) storing the second phase voltage and an associated second time stamp, wherein the second time stamp indicates the second time; and

    (e) determining a time of zero crossing of back electromotive force using the first phase voltage, the first time stamp, the second phase voltage and the second time stamp, wherein the first phase voltage is digitized when a sample and hold circuit receives a hold signal, and wherein the first time stamp is captured in a register when the hold signal is received onto a load input lead of the register.

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