Development of Sensorless Driver of 42V Brushless Motor for Cars

In this study, we developed a sensorless BLM driver with a BEMF-detecting circuit, which detects the rotor position in a digital way. Through the position-feedback control immediately after the activation of the driver, and the real-time adjustment of lead angle in response to load current, we succeeded in attaining higher accuracy of position detection over a wider operating range, which improved the motor characteristics to the equivalent level to those of the motor with a position sensor. Also, for fuel pump application, high-speed start-up of the BLM within hundreds of milliseconds was successfully achieved.