3.2 Stepping motor drive circuit

[Music playing] Welcome to TI High Precision Laboratory Stepping motor series Chapter 2. My name is Rick Duncan, and today I will Discuss the driving circuit of stepping motor. Before we begin, let's review the stepper motor. Stepping motors are used in many applications, Because they do not require external sensors Or complex control algorithm Position control. Sometimes we call it open-loop position control. Stepping motor can provide continuous movement Or maintain a fixed rotor position, It depends on the system requirements. These characteristics make it easy to realize the stepping motor, It provides a low-cost solution for system designers. In this presentation, we will focus on The circuit required to drive the bipolar stepping motor. For bipolar stepping motor, two H-bridges allow Current in either direction Flow through windings. The shape of the FET in the H-bridge is like the letter H. The direction of current determines The polarity of the magnetic field generated by the winding. Integrated stepper drive by Control by exciting the stepper winding Rotor position. In this example, the microcontroller Send pulses to the stepper driver, To indicate that the step rotor should move to Next position. When the driver receives the step pulse, A phase in the drive train. When the driver receives the next pulse, The driver excites the next phase, The rotor can then continue to move. H-bridge integrated in stepping driver Control the current in the phase winding in both directions, Used to change the polarity of the winding and continue Make the rotor move. If the microcontroller stops sending pulses, Then the rotor will remain stationary and Magnetic field alignment in the excitation space. Integrated stepper drives typically provide protection Additional features such as micro stepping and step tuning. Now you can see the internal H-bridge of the stepper, The operation can be clearly displayed. The stepper motor can be driven by voltage or current. The voltage control is used to drive the stepping motor The easiest way. The voltage of H-bridge is set as the rated voltage of stepping motor Voltage. The current is limited by the motor resistance, It shall not exceed the rated value. Due to limited current changes, Therefore, the speed of the stepper motor will be limited. Modern stepping motor driver can adjust current To achieve better performance of stepping motor. Current regulation allows voltage supplied to H-bridge Much higher than that of stepping motor Rated voltage. For example, when using current regulation, Rated voltage less than 5 volts The stepper motor can be connected to a 24 volt H-axle drive. Since the current is regulated to a specific level, Therefore, the current flowing through the winding resistance The voltage generated by the current is located at the Within the rated value range. Operating at higher H-bridge voltage, It can also make The current reaches the specified level in a shorter time. Reach the specified current level faster The motor can rotate faster. Detection resistor displayed on the source of the low side FET Used to provide a feedback loop inside the drive. The current flowing through the detection resistor generates a voltage, This voltage will be compared with the reference voltage Compare to adjust the current. About stepping motor and TI integrated stepping For more information about drives, Please visit the step drive page on ti.com.