Research And Design Of A Three-phase Brushless Motor Drive Chip

In the context of the increasing popularity of motors,the corresponding motor drive chips are also attracting attention.Nowadays,more intelligent and integrated drive chips are gradually replacing traditional drive chips with a single function,so the study of motor drive chips is becoming more and more valuable and meaningful.In this thesis,a three-phase brushless motor drive chip with speed control function is designed based on 0.18 μm BCD process,which can be used for driving low and medium voltage brushless motors.In the control session,the circuit completes the closed-loop regulation of the motor speed by PWM chopper control.The motor speed is realized to follow the reference speed.Firstly,the working principle and structure of the three-phase brushless motor are analyzed and demonstrated,then the phase change logic of the control circuit is determined,and the conditions affecting the motor speed are analyzed through the discussion of the modeling of the motor.The chip is driven by PWM chopper control,and a frequency comparator was constructed to adjust the voltage at the output of the charge pump by comparing the motor speed with the reference speed,In this way,the chip completes the PI control of the speed and realizes the closed-loop control of the motor speed.Due to the high duty cycle requirement of oscillators in digital circuits,this thesis also improves the traditional multi-harmonic oscillator by using a fully symmetrical structure so that the duty cycle of the oscillator can be close to 50%.Next,the structure of the bridge arm is determined according to the driving capability index requirements.The chip contains reasonable drive circuits and protection circuits to ensure the safety and reliability of the power devices.In the final simulation verification session,the sum of the on-resistance of the power MOSFETs on both high and low sides is 1.5 Ω,and the output current can reach2.5 A.This thesis doesn’t limit to the simulation of electrical parameters in Cadence,by establishing communication between Cadence and the Simulink platform in Matlab,the motor model in the Simulink model library is called and the control system in the chip is simulated jointly to verify the speed control function of the motor.