Patent ID: 9154009
Filing Date: 2015-10-06
Classification: B25F,H02K,H02P

Abstract:
1. A power tool comprising: a housing; a brushless direct current (BLDC) motor housed inside the housing, the motor including a stator and a rotor pivotably arranged inside the stator; a plurality of high-side and low-side switches arranged between a power source and the motor and configured as a three-phase bridge to commutate the motor, each phase of the bridge being connected to a corresponding phase of the stator; a control unit configured to provide drive signals to drive each of the high-side and low-side switches to control, for each phase of the bridge, a pulse-width modulation (PWM) of one of the high-side or low-side switches, and immediately following a first cycle ending with a falling edge of the drive signal for one of the high-side or low-side switches, to introduce a special commutation edge pulse in the drive signal of the other of the high-side or low-side switches to shunt the current from the motor before turning both the high-side and the low-side switches off during a second cycle.