Circuitry for switching the body nodes of driver transistors in drive circuitry for brushless DC motors

摘要

Circuitry for selectably connecting the body node of drive transistors of a motor control circuit. In particular, those transistors that are turned off when operating the motor in a unipolar mode have their body nodes switched so as to be connected to a reference voltage, such as ground, during unipolar mode, and to be connected to the transistor source during bipolar mode (i.e., when the transistors are active). The circuitry also is operable to briefly connect the body nodes of the transistors to their source when the opposing drive transistor is commutated, in the unipolar mode. In this way, forward biasing of inherent diodes in the drive transistor is avoided in unipolar mode, except when useful to clamp the inductive kick of the motor coils.