Design Of BLDCM Controller In Automotive Air-conditioning Blower

Brushless DC motor (BLDCM) has been widely used in automotive air-conditioner blower system, because it has some merits:fast dynamic response; efficiency; energy efficiency; long service life and son. There are mainly four kinds of control mode of BLDCM for automotive air-conditioner blower system:mechanical resistance mode、linear switch mode、PWM mode and based on MCU with sensor mode. Three kinds of these control modes have some merits:simple implementation process and low hardware cost. However, these modes can bring high heat with low speed, low energy utilization rate. The fourth one can been realized intelligent control. Meanwhile it can bring low heat with low speed and high speed range. However, it via sensors to commutate, and deeply depends on the hardware. The efficiency of this mode can’t be optimized. Therefore, the traditional modes cannot meet the low carbon environmental protection、energy saving、safety and stability.In order to solve the problem, the paper gives a speed control scheme of BLDCM with sensorless. It uses fixed pulse method to detect rotor position, and via RAMP-UP method to detect center point voltage to start a motor which belongs to inertial load. It uses analog sine mode to correct motor balance. According to the theoretical analysis and experimental data, the control scheme is feasible.The paper develops a speed control system for brushless blower with sensorless. The hardware mainly contains PWM communication circuit、power drive circuit、inverter circuit、back electromotive force(BEMF) detection circuit and son. The software mainly contains rotor position detection、starting and acceleration、BEMF detection、zero-crossing detection、PI closed-loop control and protected function.Finally, a three-phase star connected DC brushless motor is offered by Jiangsu Chaoli Electrical Appliance Co., Ltd, and the system is tested in the auto controller test center of Jiangsu Haofeng Automobile Accessories Co., Ltd. According to some tests, not only the control scheme works out the above problems, but also meets the targets of automobile air conditioning system and EMC level three. The control scheme is deeply proved to be actionable and feasible.