A Pulse Width Modulation (PWM) controller is a device or circuit that is used to control the speed of motors or the intensity of electrical signals by adjusting the duty cycle of a pulsating signal. PWM is widely used in various applications, including motor control, LED dimming, power regulation, and more.
The purpose of a PWM controller is to achieve variable control of an output, such as the speed of a motor, without relying on continuous analog signals. Instead, it employs a digital signal with a fixed frequency and adjusts the ratio of the ON time to the OFF time, known as the duty cycle, to control the average power delivered to the load.
Here's how a PWM controller controls motor speed:
Generating the PWM signal: The PWM controller generates a square wave signal with a fixed frequency. The frequency can be high, typically in the range of several kHz to MHz, depending on the application. This high frequency helps avoid audible noise in motors.
Duty cycle control: The duty cycle is the percentage of time the signal is in the ON state compared to the total period (ON + OFF). For example, a 50% duty cycle means the signal is ON half of the time and OFF the other half. By changing the duty cycle, the average voltage or current applied to the motor can be adjusted.
Motor speed control: When the PWM signal is applied to a motor, it effectively chops the supply voltage into pulses. The motor responds to the average voltage, not the instantaneous voltage, delivered during these pulses. Higher duty cycles mean longer periods of the signal being ON, delivering a higher average voltage to the motor, and thus increasing the motor's speed. Conversely, lower duty cycles reduce the average voltage, leading to slower motor speed.
Speed precision: By rapidly changing the duty cycle at high frequencies, PWM controllers can achieve precise control over motor speed or any other application that requires continuous analog-like control.
PWM controllers are used in various motor-driven applications like robotics, fans, pumps, and industrial machinery, where variable speed control is required to optimize performance, reduce energy consumption, and minimize wear and tear on the motor. The digital nature of PWM also makes it easy to interface with microcontrollers or other digital control systems.