Pulse-Width Modulation (PWM) is a widely used technique in electronics and digital control systems to control the average voltage or current delivered to a device or component. It involves rapidly switching a signal on and off at a constant frequency while varying the ratio of time the signal is in the "on" state (high level) to the time it is in the "off" state (low level). The ratio of on-time to off-time is referred to as the duty cycle.
The PWM signal can be represented as a square wave, where the voltage level stays high during the on-time and low during the off-time. By adjusting the duty cycle, you can control the effective voltage or current delivered to the load.
In motor control applications, PWM is commonly used to regulate the speed of a motor. Here's how it works:
Motor Driver: To control the motor, you need a motor driver circuit. This circuit receives the PWM signal and uses it to control the power supplied to the motor.
H-Bridge Configuration: The motor driver usually employs an H-bridge configuration. An H-bridge is an electronic circuit that allows you to change the direction of the current flowing through the motor, which determines the motor's rotation direction.
Speed Control: By adjusting the duty cycle of the PWM signal, you can control the average voltage applied to the motor. For example, if the duty cycle is 50%, the motor will receive an average of 50% of the maximum voltage, and it will run at approximately half of its maximum speed. Similarly, a duty cycle of 25% will result in a slower speed, while a duty cycle of 75% will make the motor run faster.
Smoothness and Efficiency: PWM control provides a smooth and continuous adjustment of the motor speed, as opposed to other methods that simply use resistors to reduce voltage (which can lead to power loss as heat). PWM offers higher efficiency because it modulates the power rather than dissipating it as heat.
Torque Control: Besides speed control, PWM can also be used for torque control in some motor types. By adjusting the duty cycle dynamically, you can change the motor's torque output.
PWM is a fundamental technique in motor control systems because it allows for precise and efficient control of motor speed and, in some cases, torque. It is used in a wide range of applications, including robotics, automation, fans, pumps, electric vehicles, and many other devices that involve motor-driven systems.