A driving circuit of a PMSM can include: a current sampling circuit that obtains a current sampling signal by sampling a rotor current of one phase of the PMSM; a sliding mode estimating circuit that receives the current sampling signal and a voltage sampling signal that represents a rotor voltage of the phase, estimates a back electromotive force information of the phase, and generates a first voltage signal that represents the back electromotive force information; a speed computing circuit that receives the first voltage signal, and generates an angular velocity signal that represents rotor cycle information; and a PWM control circuit that generates a PWM control signal according to the angular velocity signal, where the PWM control signal controls the turn on/off of switches in a three-phase inverter, to control an operating current of the PMSM to be a sine wave current.