Controller of position sensorless brushless DC motor

摘要

PURPOSE:To shift to a position sensorless operation in a short time by increasing an exciting voltage of a motor in a last exciting phase or setting it to '0' by a synchronous operation in real time based on presence or absence of rotor position detection through a drive circuit when the synchronous operation is switched to the sensorless operation. CONSTITUTION:Control means 6 operates to switch transistors Ta+, Tb+, Tc+ and Ta-, Tb-, Tc- of an inverter 4 based on a rotor position detection signal from rotor position detecting means 5 and switches an exciting phase. When the signal is not obtained, it is regarded that sufficient rotating speed is not obtained to increase an exciting voltage. When the signal is not obtained even if it exceeds an exciting time of last synchronous rotating speed, the voltage is set to '0' to stop exciting of a brushless DC motor 1. When the signal is obtained, the means 6 starts it to rapidly shift to a position sensorless operation.