公开(公告)号：US09819290B2

公开(公告)日：2017-11-14

申请号：US15260815

申请日：2016-09-09

申请人： Johnson Electric S.A.

发明人： Hai Bo Ma ,  Yong Gang Li ,  Yong Sheng Gao ,  Jin Yun Gan ,  Yuk Tung Lo ,  Wei Long Lan

IPC分类号： H02P1/04 ,  H02P6/18 ,  H02P6/20 ,  H02K7/14 ,  B25F5/00

CPC分类号： H02P6/183 ,  B25F5/00 ,  H02K7/145 ,  H02P6/181 ,  H02P6/20

摘要： A power tool and a motor drive circuit thereof are provided. The motor drive circuit includes an inverter, a controller and a current sensor. The inverter includes a plurality of semiconductor switches and configured to convert a voltage from a power supply into an alternating current for an electric motor. The controller is configured to output detecting signals and drive signals for the inverter. The current sensor is configured to sample a current flowing through the motor, the current comprising a plurality of driving current portions corresponding to the drive signals and a plurality of position detecting current portions corresponding to the detecting signals. The controller determines the drive signals at least based on the position detecting current portions of the current so as to control power modes of the semiconductor switches in the inverter in a starting stage of the motor.