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Digital adaptive sensorless commutational drive controller for a brushless DC motor

  • US 6,901,212 B2
  • Filed: 06/13/2002
  • Issued: 05/31/2005
  • Est. Priority Date: 06/13/2002
  • Status: Expired due to Term
First Claim
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1. A method of providing synchronous commutation to a plurality of phase windings in a brushless, sensorless, direct current (DC) motor comprising:

  • receiving binary back electromotive force (BEMF) level signals associated with each phase winding, said BEMF level signals indicating whether the voltage level in the associated phase winding is above or below a threshold voltage level;

    operating a state machine, said state machine sequentially advancing through a plurality of states, each state being based on the position and motion of the DC motor rotor and each state dictating which of the phase windings in the DC motor are supplied drive power;

    detecting changes in the logic level of the BEMF level signals;

    counting the amount of time that elapses between adjacent logic level changes in the BEMF level signals;

    generating a switch time that is some fraction of the elapsed time between adjacent logic level changes; and

    advancing the state machine when the switch time elapses following the most recent logic level change.

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