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US 6,633,145 B2Granted
Circuit for improved back EMF detection
AssigneeSTMicroelectronics S.r.l.
InventorsJianwen Shao, Dennis C. Nolan, Kwan A. Haughton, Thomas L. Hopkins
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AssigneeSTMicroelectronics S.r.l.
InventorsJianwen Shao, Dennis C. Nolan, Kwan A. Haughton, Thomas L. Hopkins
Estimating the term…
A system and method of advancing the commutation sequence of a brushless DC motor is provided. The motor having a plurality of coils, each of the coils coupled together at one end to a common center tap and coupled at an opposite end, through a respective coil tap, to both a source voltage and ground via selectively actuateable switches having diodes coupled in parallel therewith. The motor operates in a pulse width modulation (PWM) mode having PWM-on states and PWM-off states. During PWM-off states, a coil tap voltage from the coil tap of a floating phase is provided to a preconditioning circuit. The preconditioning circuit adjusts the floating phase coil tap voltage to compensate for an amount of voltage substantially equal to an amount of voltage by which a voltage at the center tap deviates from zero. The preconditioning circuit further includes sharpening circuitry for amplifying the adjusted floating phase coil tap voltage. A signal output from the preconditioning circuit is provided to a zero-crossing detection circuit for detecting zero-crossing and determining when to advance in the commutation sequence.
A driver circuit for a brushless motor having a first coil coupled between a first coil tap and a center tap, a second coil coupled between a second coil tap and the center tap, and a third coil coupled between a third coil tap and the center tap, the driver circuit operating in a pulse width modulation (PWM) mode having a PWM-on state and a PWM-off state, the driver circuit comprising:
A method for determining when to advance in a commutation sequence of a brushless DC motor, the motor including a first phase having a first coil coupled between a first coil tap and a center tap, a second phase having a second coil coupled between a second coil tap and the center tap, and a third phase having a third coil coupled between a third coil tap and the center tap, the method comprising the steps of:
A motor having a plurality of coils coupled together in one of a delta or wye configuration, each of the coils coupled at one end, through a respective coil tap, to both a source voltage and ground via selectively actuateable switches, each of the switches having a diode coupled in parallel with the respective switch, the motor comprising:
Dependencies are inferred from the claim text.