Research And Design Of Brushless DC Motor Driver Chip

In recent years,brushless DC motor due to simple structure,high efficiency and other significant advantages are widely used in national defense,robotics,automotive electronics and other fields.Motor driver chip is a key part of controlling motor operation,with the improvement of integrated circuit design and process level,the performance and cost of motor driver chip put forward higher requirements.Therefore,the in-depth study of brushless DC motor driver chip is of great significance.Based on the basic and control theory of brushless DC motors,this thesis determines the full-bridge drive mode and selects LDMOS as the switching device.Based on the CSMC 0.25μm BCD process,a brushless DC motor driver chip is designed,with a typical operating voltage of 42 V,a maximum output current of 2A,and an operating temperature range from-40°C to 145°C.The chip is composed of reference circuit,logic control circuit,low side control circuit,high side control circuit and protection circuit and other modules;The high side control circuit includes an oscillator,a charge pump,and bootstrap circuit.This thesis first designed the reference circuit to provide voltage signals and current signals.The logic control circuit implements the logic outputs by NAND and NOT.A hysteresis comparator is used to prevent output oscillation,and a cross-coupling circuit is used to generate dead time.Secondly,the charge pump takes the form of a level shift circuit combined with a Darlington structure When the chip operating frequency is low,the bootstrap capacitor can be charged supplemented.In addition,the bootstrap circuit controls PMOS through the feedback circuit,which can quickly charge the bootstrap capacitance,and realize the bootstrap function that the gate potential of the high side mosfet is always 6V higher than the source potential.The temperature protection circuit adopts a bistable structure with hysteresis,the alarm temperature is 145.7°C,the hysteresis is 10°C;and the shutdown temperature is 165.4°C,the hysteresis is 14°C.Finally,to prevent excessive current from burning the chip,the overcurrent protection circuit was designed to ensure that the chip stopped operating when the current exceeded10 A.After the design and simulation of each module meet the chip design parameters,the general simulation of the chip was carried out,the functions of static power consumption,forward rotation,reverse rotation,and braking are verified,all meet the design requirements.