Controller for a multi-phase brushless dc motor

Abstract

Control of rotational speed of a direct current multi-phase brushless motor is provided using an apparatus and method that works at low speed but does not depend upon Hall effect sensors. An apparatus for accelerating rotation of the motor shaft has a power stage circuit coupled to a back Electromotive Force (EMF) sensor circuit and a microprocessor. The power stage pulses at a duty cycle less than 100% under control of the microprocessor. The back EMF sensor circuit measures an order with respect to voltage of at least one phase relative to one or more other phases during off-time. The microprocessor determines one or more phases to be pulsed, and the polarity of the pulses based on the measured order. A method for sustaining rotation pulses the phases, measures order with respect to voltage of at least one phase relative to one or more other phases, and updates commutation state based on the measured order. A method of accelerating rotation generates one or more power pulses, determines an order with respect to voltage of one phase relative to one or more other phases, and generates subsequent pulses on phases and with polarity determined by the measured order.

Dependencies are inferred from the claim text.