Wide Input Voltage,1/256 Microstep Motor Driver

Stepper motor is a kind of open loop control element which can transform electric pulse signal into linear or angular displacement.It is widely used in daily life and industrial production.With the development and improvement of stepper motor,the stepper motor driver has also experienced a long development.From the 1970 s to the 1980 s,the stepper motor driver has experienced the evolution of single voltage driving,high and low voltage driving and chopper driving,and the efficiency of the driving circuit has gradually improved.In the mid-1980 s,foreign research institutions invented subdivision driving on the basis of chopper driving.Subdivision driving is to control the size and direction of each phase winding current in the stepper motor,so that they change in accordance with the law,so as to achieve a higher resolution.The application of subdivision technology greatly improves the driving accuracy of stepper motor.With the further advancement of industrialization in our country and the improvement of industrial production requirements,it is very necessary and urgent to study the high performance stepper motor driver chip.Nowadays,most of the stepper motor driver chips in the market are high-voltage chips for industrial production,and a few of the driver chips for consumer electronic products have problems such as low stepper precision and high power consumption.In order to meet the market demand for low voltage and high precision,based on the principle of subdivision drive circuit,this thesis designs a wide voltage range and high precision stepper motor driver circuit.The circuit adopts 0.18 μm CSMC 80 V BCD process,the operating voltage range is 2.5～10V,the system is based on PWM control,the single bridge output effective current is 1.4 A.The sleep mode of the system is designed with ultra-low power consumption,and the current is less than 10 μA in the sleep mode.The stepping mode,rotation direction,turn-off time,torque magnitude and decay mode of the system can be adjusted.The system has automatic decay function,in the automatic decay mode,the decay state is only related to the current size,so the system can rotate more smoothly,and is not affected by the aging degree of the motor and the external environment;The system can achieve up to 1/256 micro-step subdivision control,step precision is higher.The system circuit includes power processing module,band-gap reference module,LDO module,oscillator module,charge pump module,counting module,DAC module,comparator module,decay module,system logic module,driving module,and protection module.Completed the circuit design and simulation,and participated in the layout design.This thesis focuses on solving the problems of low-voltage design,high subdivision and automatic decay technology.Circuit working voltage range is wide,need to take into account the low voltage and high voltage can work normally,so the design of each module need to consider the low voltage design.Because the over-driving voltage of the power tube is low when it works at low pressure,the on-going resistance of the power tube is large.Therefore,the charge pump is used to drive the power tube at low voltages instead of the internal lowvoltage power supply.The system can achieve up to 256 subdivisions,which increases the design difficulty while providing high precision.Each doubling of the fine fraction means that the resistors and switches need to be doubled,and a large number of resistors and switches make wiring more difficult.Therefore,the layout of DAC module is personalized according to the rules of components.Automatic decay technology greatly improves the performance of the drive system,but its logic is quite complex.As well as the direction transformation and mode transformation in the process of operation of the solution to the problem,this thesis has been deeply discussed.