Abstract: A motor having a differential phase back EMF sensing circuit for sensing rotor position includes a stationary assembly with at least three windings. The rotation of the rotor induces a back EMF in the windings. A control circuit energizes each of the windings with a current according to a preselected sequence. A switch network is coupled to the windings and provides two back EMF signals as a function of the back EMF induced in two of the windings when the control circuit is energizing the third winding. A signal processor is coupled to the switch network and produces a difference signal representative of a difference between the two back EMF signals. An integrator integrates the difference signal to produce an integrated difference signal. The motor includes a reference signal generator which produces a reference signal and a comparator which produces a trigger signal when the integrated difference signal exceeds the reference signal.

Abstract: A device for measuring energy delivered by a motor to a load is adapted to be connected to the motor which is coupled to the load and connected to a power source through first and second power supply lines. The device includes a line voltage sensing circuit for sensing the voltage across the power supply lines, a line current sensing circuit for sensing the current flowing through the motor and a pulse width modulator which modulates the sensed voltage to produce a pulse width modulated first electrical signal. The device also includes a first switch, responsive to the pulse width modulated first electrical signal which modulates an output of the line current sensing circuit to produce a power waveform and an integrator which integrates the power waveform to produce an output signal indicative of the energy delivered by the motor to the load.

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.