This study presented a sensor-less permanent magnet synchronous motor (PMSM) driver for controlling air-conditioner rotary compressor speed. In this study, a novel quasi-sine pulse-width modulation (PWM) driving method is proposed. Furthermore, the current feedback control scheme and rotor magnet pole position detection were included. The system structure was implemented using a digital signal processing (DSP) platform. The proposed driving scheme was compared with the square-wave driving without current feedback and six-step square-wave driving method with current feedback. Experimental results demonstrated that the proposed quasi-sine PWM driving method implemented in an air-conditioner compressor driver was capable of reducing the magnitude of rotational speed ripples, compressor vibration and system power consumption.