Pulse-Width Modulation (PWM) is a modulation technique used in electronic systems to control the average voltage level supplied to a device or component. It's commonly used in applications such as motor control, LED dimming, audio synthesis, and more. PWM allows you to vary the intensity or output of a device by adjusting the width of the pulses within a fixed period, without changing the voltage level.
A PWM signal consists of a repeating cycle called a period, during which there are two main components:
Pulses: These are high (on) voltage levels that represent the "active" state or the desired output level. The width of the pulse is the portion of the period during which the voltage is high.
Gaps: These are low (off) voltage levels that represent the "inactive" state or zero output. The width of the gap is the portion of the period during which the voltage is low.
The ratio of the pulse width to the total period is called the "duty cycle." The duty cycle is often expressed as a percentage and indicates the proportion of time the PWM signal is in the high state (on) compared to the total period.
The PWM signal can be generated using various methods and components, such as microcontrollers, timers, dedicated PWM generator ICs, and even programmable logic devices. Here's a simplified explanation of how it's generated using a microcontroller:
Microcontroller Configuration: The microcontroller's hardware timers are set up to generate PWM signals. The timers have registers to set the period and the compare value.
Setting the Duty Cycle: To generate a specific duty cycle, you set the compare value to determine when the output should transition from high to low (or vice versa) within a single period. For example, to achieve a 50% duty cycle, you would set the compare value to half of the period value.
Timer Operation: The timer counts up from 0 to the set period value. When the timer's value matches the compare value, the output is toggled.
Output Signal: The microcontroller's output pin connected to the device/component being controlled produces the PWM signal. The voltage on this pin changes between high and low states according to the timer's operation.
By adjusting the period and the compare value, you can change the frequency and duty cycle of the PWM signal. This, in turn, affects the average voltage delivered to the device, allowing you to effectively control its behavior without changing the actual supply voltage.