# Introduction to stepper motor driver-Control, drive and safety of stepping motor

by：V&T Technologies     2020-01-08
This paper introduces the control and driving principle of stepping motor, motor driver and safety technology of motor drive. The operation mode of stepping motor, the basic operation mode of stepping motor is called'Excitation mode' , Can make the stepping motor work in full-step mode, half-step mode and micro-step mode, of which micro-step mode can effectively reduce the phase current noise of the stepping motor and improve the inherent noise and vibration problem of the stepping motor. Three excitation modes will be introduced below. • Full-step mode, the so-called full-step mode, is to design a fixed step angle to work according to the inherent structure of the motor, an electric pulse, and a step angle for the stepping motor to advance. This step angle is determined by the design structure of the motor, which can also be understood as the motor rotates at the maximum step angle. • Half-Step mode half-step mode performs step rotation at half angle of step angle determined by the inherent structure of the motor. As shown in the following figure, the total number of poles of the stepping motor is 4, and the corresponding step angle is 90 degrees, then in the half-step mode, each pulse of the stepping motor rotates 45 degrees. • The micro-step mode is similar to the half-step mode, with a smaller step angle, I . e. 1/4 steps, 1/8 steps, and 1/16 steps, which can reach a very high subdivision. The corresponding step angle is multiplied by the micro step coefficient at the angle of the whole step. The smaller the step angle of the stepping motor is, the higher the required machining accuracy will be, and the greater the error of the corresponding step angle during micro-step will be. The motor controls the driver. The stepping motor cannot be directly connected to the power frequency AC or DC power supply to work, but must use a special stepping motor driver, it consists of pulse generation control unit, power drive unit, protection unit, etc. As shown in. The direct coupling between the drive unit and the stepping motor can also be understood as the power interface of the stepping motor microcomputer controller. The following is an example of a system that uses MCU and separated components. MCU is equivalent to the brain that controls the motor. It sends the step angle Time, rotation direction and repetition times of the motor to discrete devices, while discrete devices send signals according to MCU, amplifies voltage and current and sends them to the motor to drive the motor to rotate. As shown in the above figure, the system uses MCU and motor control driver IC. From the input control signal to distinguish, stepping motor controller IC can be divided into phase Force type and clock force type. The phase-in force type means that the current direction of each excitation phase of the motor is controlled by the input signal, while the clock-in force type means that the drive of the motor is controlled by the pulse signal. • Phase-in force type, phase-in force type motor driver needs two-phase control signals of A and B, only clock signal is needed, MCU that needs control signal does more transportation work. • Clock input force type, clock input force type motor driver control interface, clock signal (Single pulse signal) Input, its control signal is relatively simple, MCU resources occupy less. Motor Drive safety technology •Power-on reset function (POR) The power-on reset function will monitor the motor driver and the power supply of the motor drive controller. In order to prevent motor operation failure, it will force the output signal to be turned off until the power supply voltage remains stable. As shown in. •Overcurrent detection function (ISD) The overcurrent shutdown function will monitor the current of the output unit. If the current exceeds the specified value, the output will be forcibly shut down. The purpose of this function is to temporarily stop the IC output when a short circuit occurs. As shown in. •Thermal shutdown function (TSD) The thermal shutdown function is to turn off the output when the temperature of the motor control driver chip exceeds the specified value and keep the state until the temperature drops. TAG stepper motor, stepper motor driver
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