Efficiency optimization control for single-phase brushless dc fan motors

This paper proposes a modeling method for characterization of single-phase brushless dc (BLDC) fan motors in applications to information appliances. The nonlinear back-EMF induced by the rotor flux with stator winding is modeled by a look-up table. By parameter identification and computer simulation, this modeling method assists designers in waveform analysis and control loop design. Simulation results have been verified with the measured experimental results. Moreover, in order to improve the efficiency of the BLDC fan motor over the entire speed control range, this paper develops an efficiency optimization control method based on a closed-loop current control scheme by using the Hall sensor feedback. The proposed control scheme has been realized and compared with the conventional open-loop PWM control scheme. Experimental results show a 40% reduction of peak current and 18% reduction of RMS current have been achieved at rotation speed of 3000 RPM.