Importance

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Abstract

Control circuit for an electronically commutated motor which has a rotatable assembly and further has a stationary assembly with a plurality of winding stages having terminals for energization, and switches for applying a voltage to one or more of the terminals of the winding stages at a time and commutating the winding stages in a preselected sequence to rotate the rotatable assembly. A preselected sequence of winding stages are left correspondingly unpowered so that a plurality of the winding stages are unpowered at some time. The winding stages generate back emf signals and also couple electrical signals from each energized winding stage to the unpowered winding stages which signals can interfere with detection of back emf for position sensing purposes. The control circuit includes a first circuit for selecting at least two of the unpowered winding stages which have electrical signals coupled to them that have a predetermined relationship in polarity and magnitude. A second circuit produces an electrical output from the voltages on the winding stage terminals of the winding stages selected, so that the electrical signals coupled from each energized winding stage are substantially canceled when they have the predetermined relationship while the back emf is preserved for position sensing substantially free from interference from the electrical signals that are coupled from each energized winding stage to the unpowered winding stages. Other control circuits, electronically commutated motor systems and methods of control and operation are also disclosed.

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First Claim