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    Stepper Motor Driver vs. Servo Motor Driver

    A stepper motor is an actuator that converts electrical pulses into angular displacement. When the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction, and its rotation runs step by step at a fixed angle. The angular displacement can be controlled by controlling the number of issued pulses, so as to achieve the purpose of controlling the displacement. At the same time, the speed and acceleration of the motor rotation can be controlled by controlling the pulse frequency, so as to achieve the purpose of speed regulation. The rotor inside the servo motor is a permanent magnet. The U/V/W three-phase electricity controlled by the driver forms an electromagnetic field. The rotor rotates under the action of this magnetic field. At the same time, the encoder that comes with the motor feeds back the signal to the driver. The target value is compared and the angle of rotor rotation is adjusted. The accuracy of the servo motor is determined by the resolution of the encoder. So what are the differences between stepper motor driver and servo motor driver?

    Stepper Motor Driver vs. Servo Motor Driver

    Different working principle

    Stepper motor driver: It is an electronic product that can send out uniform pulse signals. After the signal it sends enters the stepper motor driver, it will be converted by the driver into a strong current signal required by the stepper motor to drive the stepper motor to run. The stepper motor controller can accurately control the stepper motor to rotate through every angle. What the driver receives is a pulse signal. Every time a pulse is received, the driver will give a pulse to the motor to make the motor rotate at a fixed angle. Because of this feature, stepper motors are widely used in various industries.

    Servo drive: It is a controller used to control servo motors. Its function is similar to that of frequency converters acting on ordinary AC motors. The servo motor driver is part of the servo system and is mainly used in high-precision positioning systems. Generally, the servo motor is controlled by three methods of position, speed and torque to achieve high-precision positioning of the transmission system. It is currently a high-end product of transmission technology.

    Different circuit composition

    Circuit composition of stepper motor driver

    1. Motor drive circuit: The stepper motor drive circuit is designed on the basis of the H bridge circuit. The use of discrete component MOS tubes to build a dual H-bridge drive circuit is a mature motor control solution. The circuit is not complicated. According to the different operating currents of the MOS tubes, the upper limit of the current can even be as high as tens of amperes. It is an ideal stepper motor driver solution.
    2. Motor parameter measurement circuit: The motor current sampling resistor is a constantan resistor, one end is connected to the bottom of the H Bridge, and the other end is connected to GND. The voltage and current signal conditioning circuit is built with LM324 operational amplifier. After the voltage is followed, it is sent to the MCU, and the MCU has a built-in 10Bit A/D converter for A/D sampling. The chassis temperature monitoring uses the digital temperature chip DS18B20, which is attached to the surface of the motor shell to monitor the temperature parameters in real time and send them to the MCU.
    3. Power supply and MCU control circuit: The drive circuit in the system is powered by the input voltage. The MCU and the Bluetooth module need an additional 3.3V voltage power supply. The traditional linear regulator has low efficiency, large size and serious heat generation. Therefore, a DC-DC power supply is used to provide 3.3V voltage to ensure the normal operation of the device.

    Circuit composition of servo motor driver

    1. Motor rectifier circuit: The main topology circuit of the rectifier unit is a three-phase full-bridge uncontrolled rectifier circuit, which is essentially a series of three-phase half-wave controllable rectifier circuits with a set of common cathodes and a set of common anodes. It is customary to connect the cathodes together. The three inter-thyristors are called a common cathode group; the three thyristors whose anodes are connected together are called a common anode group.
    2. Power drive circuit: The power drive unit generally adopts an intelligent power module, which rectifies the input three-phase power or mains power through a three-phase full-bridge rectifier circuit to obtain the corresponding DC. The power unit is a high-voltage inverter component that uses power electronic devices for rectification, filtering, and inversion. It is mainly composed of rectifier bridges, thyristors, electrolytic capacitors, and IGBTs. The whole process of the power drive unit can be simply said to be the process of AC-DC-AC.
    3. Motor control circuit: The main circuit uses a digital signal processor as the control core, which can implement more complex control algorithms and perform intelligent control.


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