Related Terminologies

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What is Pulse Width Modulation?


Table of Contents

By breaking up a signal into smaller, more manageable chunks, pulse width modulation reduces the average power that an electrical signal can deliver. Instead of a continuously changing (analog) signal, the energy of the signal is distributed through a series of pulses in the PWM method.

How is a Pulse Width Modulation Signal generated?

Using a comparator, a pulse width modulating signal is produced. The comparator receives one part of its input as the modulating signal, while the comparator receives the other part as the sawtooth wave or non-sinusoidal wave. As its output waveform, the comparator compares two signals and produces a PWM signal.

The output signal is in the “High” state if the sawtooth signal is greater than the modulating signal. The comparator output, which specifies the width of the pulse generated at the output, is determined by the magnitude’s value.

Important Parameters associated with PWM signal

Duty Cycle of PWM

We are aware that a PWM signal remains “ON” or “OFF” for a specific amount of time. The duty cycle is the percentage of time that the signal stays “ON.” The signal must have a 100% duty cycle if it is constantly “ON.” The following is the formula for calculating the duty cycle:

The duty cycle determines the average voltage value. Controlling the width of a pulse’s “ON” can therefore alter the average value.

Frequency of PWM

The speed at which a PWM completes a period is determined by its frequency. The figure above depicts a pulse’s frequency.

The following is how the frequency of PWM can be determined:

Time Period is the sum of the On Time and Off Time.

Output Voltage of PWM signal

The percentage of the duty cycle will determine the PWM signal’s output voltage. For instance, if the operating voltage is 5 V and the duty cycle is 100%, then the output voltage will also be 5 V. On the other hand, if the duty cycle is 50%, then the output voltage will be 2.5 V.

Types of Pulse Width Modulation Technique

The following is a list of the three traditional types of pulse width modulation techniques:

Trail Edge Modulation: In this method, the signal’s lead edge is modulated while the trailing edge remains constant.
Lead Edge Adjustment – In this method, the sign’s lead edge is fixed, and the following edge is regulated.
Pulse Center Two Edge Modulation: In this method, both of the pulse’s edges are modulated while the pulse center remains constant.

Applications of Pulse Width Modulation

The PWM technique is used in a wide range of power applications due to its high efficiency, low power loss, and precise power control. The following are some examples of PWM’s applications:

Encoding is carried out in the field of telecommunication using the pulse width modulation method.
The PWM is used to regulate motor speed because it helps regulate voltage.
The computer’s CPU fan is controlled by the PWM method, which effectively dissipates heat.
Amplifiers for audio and video make use of PWM.

Advantages and Disadvantages of Pulse Width Modulation

Before we get into the downfalls of the pulse width modulation method, let’s first discuss its benefits:

The PWM technique maintains the LED’s brightness while preventing overheating.
The PWM method is precise and responds quickly.
The PWM method has a high input power factor.
The PWM technique enables motors to produce maximum torque even at lower speeds.
The Pulse width modulation technique has a number of benefits, some of which are listed above. Now let’s look at some of its drawbacks:

Switching losses are very high because the PWM frequency is high.
It causes interference at radio frequencies (RFI).

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