Driving circuit and method of permanent magnet synchronous motor

The invention discloses a driving circuit and method of a permanent magnet synchronous motor (PMSM). The method comprises steps of: estimating the counter-electromotive force information of a certain phase of a PMSM by sampling the voltage information and the current information of the phase; and computing an angle difference between a first voltage signal representing the counter-electromotive force information and a current sampling signal representing the current information in order to obtain an angle difference signal, wherein the angle difference signal is used for adjusting the amplitude of a first horseshoe-shaped modulating wave in order to control the current phase of a rotor to be consistent with the phase of the first horseshoe-shaped modulating wave and further achieve maximum torque per ampere. The method obtains the counter-electromotive force information by estimation, does not require complex coordinate transformation, and is simple in algorithm and easy to implement. In addition, the method changes a phase difference between the counter-electromotive force of the motor and the phase current by adjusting the current of the motor, thereby achieving maximum torque control and high motor efficiency.