Method to reduce the commutation loss in a motor inverter

A circuit, comprising:

• a multiphase gate driver to be coupled to a multiphase inverter for driving a multiphase motor, wherein, for each phase, the multi-phase gate driver is to:
• in accordance with a pulse width modulation (PWM) control signal, turn on and off a high side transistor of a given pair of high and low side transistors of the multiphase inverter;
• discontinue the PWM control signal to the high side transistor of the given pair and turn off the high side transistor of the given pair;
• and
• turn on the low side transistor of the given pair until a current level through the low side transistor falls below a threshold, at which time, turn off the low side transistor.

A motor controller to drive an N-phase motor, comprising:

• a multiphase inverter including a plurality of pairs of high and low side transistors, the high and low side transistors of each pair connected together at a node, and wherein each node of a pair of high and low side transistors is to be coupled to a separate winding of the N-phase motor;
• a multiphase gate driver coupled to the multiphase inverter;
• and
• a microcontroller coupled to the multiphase gate driver and configured to, for each of the N phases:
• generate control signals to cause the multiphase gate driver to toggle on and off a low side transistor of a given pair of the pairs of high and low side transistors in accordance with a pulse width modulation (PWM) control signal;
• generate a first control signal to cause the multiphase gate driver to turn off the low side transistor of the given pair;
• and
• generate a second control signal to cause the multiphase gate driver to turn on the high side transistor of the given pair until current through the high side transistor falls below a threshold, at which time, to turn off the high side transistor.

A method of controlling a multiphase motor comprising a plurality of windings, comprising:

• for a given pair of power transistors among a plurality of pairs of power transistors, each pair comprising a high side transistor connected to a low side transistor, turning on and off the high side transistor of the given pair in accordance with a pulse width modulated (PWM) control signal;
• while turning on and off the high side transistor of the given pair, sequentially turning on the low side transistor of each of the other pairs of power transistors while turning off all other low side transistors;
• turning off the high side transistor of the given pair;
• turning on the low side transistor of the given pair;
• determining that current through the low side transistor of the given pair falls below a threshold indicative that energy has dissipated in a winding of the multiphase motor;
• and
• responsive to the determination that the current has falling below the threshold, turning off the low side transistor of the given pair.