COUNTER ELECTROMOTIVE FORCE DETECTOR CIRCUIT OF SENSORLESS BLDC MOTOR AND METHOD THEREOF

摘要

PURPOSE: A counter-electromotive force detecting circuit of a sensorless BLDC motor and a method thereof are provided to output a rotor position detection signal adjacent to a detection signal of a hole sensor by synchronizing the detection signal with a pulse modulation signal. CONSTITUTION: A three phase full bridge circuit(10) operates a motor unit(20). A detecting unit(30) detects counter-electromotive force by comparing a counter-electromotive force level with a reference voltage value. The detecting unit includes a first LPF(Low Pass Filter)(31) connected with an output terminal of each phase of the motor unit and three of first comparators(32) comparing an output signal of each phase with the reference voltage value. A pulse modulating unit(40) outputs a pulse modulation signal by comparing a DC link current with a signal filtered at different frequency bands. A synchronizing unit(50) outputs a rotor position detection signal by synchronizing a synchronizes detection signal with the pulse modulation signal. [Reference numerals] (41) Second LPF; (AA) Third LPF;