The so-called PWM is the pulse width modulator, which provides the motor with a pulse with a certain frequency and adjustable pulse width. The greater the pulse width, the greater the duty cycle, the greater the average voltage provided to the motor and the higher the motor speed. Conversely, the smaller the pulse width, the smaller the duty cycle. The smaller the average voltage supplied to the motor, the lower the motor speed.
No matter whether the PWM is high or low, the motor is rotating, and the speed of the motor depends on the average voltage.
The main electrical structure of extended data DC motor servo driver usually adopts H bridge, and the speed regulation mostly adopts PWM mode, and its modulation modes are roughly bipolar, unipolar and restricted unipolar. In different PWM modes, the operating characteristics of the motor and the switching loss and safety of the main circuit are different.
Brushless DC motor usually adopts three-phase full-bridge main circuit structure and operates with three-phase six-state square wave control. In any state, the two switches are controlled by PWM, and the PWM modulation mode is very similar to the H-bridge PWM modulation of DC motor, and two bridge arms are controlled at the same time. The selection of PWM mode for DC motor speed regulation should be based on technical requirements.
Usually, DC servo control system mostly adopts bipolar control, which can ensure the continuity of motor current and so on, thus ensuring the rapid response of motor; For the speed control system, the motor usually works at high speed and heavy load. At this time, you can choose monopole or restricted monopole, so that the main circuit is not easy to fail directly and the working reliability is high. At the same time, under different PWM modes, the loss, thermal balance and freewheeling feedback of bridge circuit power devices are also different.
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