PWM is known as “Pulse Width Modulation”, it is used to convert analog signals in to single digital bit with the help of microprocessors. It is widely for communication purposes and the control of several electronic devices. The main component of PWM is duty cycle and frequency of the signal.

Duty cycle: Duty cycle is that period in which signal is at highest amplitude or in on State.

Frequency: Number of vibrations per unit time.

A simple glimpse of PWM signals is shown in the figure. This is a converted digital bit signal.

The figure shows the change in behavior of digital bit signal with changing of duty cycle.

Based on modulation PWM is divided into three major types.

• When the center of pulse modulation is fixed bandwidth is changed according to the lead head and tail head.
• When tail head is fixed and lead head can be changed
• When the Lead head is fixed and the tail head can be changed.

Generation of PWM Signal:

The generation of PWM signal is shown in the figure below, as a comparator is a key factor that generates digital bit signal by mixing modulating signal and saw tooth wave the smooth signal is produced. If the frequency of the Saw smooth signal is high as compared to the modulating signal then the duty cycle of the digital bit signal is at maximum position, conversely, if it is then the modulating use show low frequency.

   

Delta modulation: in delta modulation, the output signal is compared to the reference signal and the offset in the signal is measured with the limits which are set accordingly.

Delta signal: Delta signal compared the output signal with the input one and error is measured accordingly. The integrated signal is further compared with the limits.

Space vector modulation: In this form, PWM is operated based on the on and OFF signal that is given to the device, the reference signal is compared regularly and after each sample, the data is checked with the input signal.

PWM for controlling Motor Speed:

When an electric current is applied to the terminals of the armature it starts rotating, due to the rotation of the armature magnetic field is produced around it. The current is also passed through the armature to the secondary winding and a secondary magnetic field is produced around there. The motor starts rotating because of these two magnetic fields .he rotation of the motor can be controlled with the help of PWM.

To control the speed of the motor we have to control the voltage across its terminals, for that purpose Pulse width modulation plays a lot of important roles. As in PWM voltage was controlled through on and off signals, similarly here we give “ON” and “OFF” pulsation to the motor that affects the duty cycle. When the signal is “ON” the duty cycle is at the highest point and we have maximum motor speed, conversely when we give the “OFF” signal to it than the duty cycle is decreased similarly the motor speed starts decreasing.

The motor speed can also be controlled by warring the bandwidth or timing of these signals. This can be done by varying voltage across it. If the bandwidth of the “ON “ signal is more which means the signal is on for more time than the motor speed got increased.

  

A simple implementation of PWM in circuits is shown in the figure. By using the PWM technique Power consumption of the converging transistor become very minimum. As PWM is sending either ON signal or OFF signal so it remains in the same state. Moreover, the efficiency of the motor is improved as it currents on constant voltage due to which motor always run at its maximum capacity, the rotation of motor also get smoother and shows no installation.

Power transmission:

    Power transmission mostly causes losses of electric signals and efficiency due to the losses of resistance and switches. the simple analog signal does not give maximum efficiency during operational conditions, but with the help of the PWM maximum efficiency can be achieved as PWM is either send ON signal or OFF signal which gives maximum-minimum losses, like switches and resistance show losses when an excess electric signal is given to them or highest frequency.

Modern electric dimmers and electric cookers also use the PWM technique. The electric cookers work on a device known as simmerstat, which operates on the fluctuation of the duty cycle when the signal is given to the hob it becomes Power effective, and minimum energy losses are faced as compared to an ordinary one. As temperature fluctuation is minimum it does not affect the efficiency. 

PWM Amplifiers:

    PWM amplifiers are so much effective that they are almost used in every device due to their efficiency and minimum power loss. The analog signal is first converted into the digital bit signal, that signal is further amplified through MOSFET and BJP transistors, before reaching the speakers they are again converted into the analog signal.

As PWM and MOSFET were operated at specific conditions they do power loss and heat generation, MOSFET operates above 8v signal and for BJP show losses below 5V. So with the help of the PWM signal modulation technique, the constant signal is given to these devices to a minimum these heat loss and increase power efficiency. 

Characteristics of Digital Amplifier:

• Digital Amplifiers are fewer heat dissipaters and more efficient as they are better signal amplifiers than ordinary ones.
• As they dissipate less heat son small heat sinkers are enough for them, where we need bigger heat sinkers devices for linear amplifiers.
• They can be operated at a minimum voltage as 6v would be enough to operate them.
• PWM amplifiers are cheap, cost-effective, and more result-oriented.

These are some of the fundamental aspects of PWM that set it apart from linear circuits. The installation and operation of PWM in the amplifier are depicted in the diagram below. The duty cycle and bandwidth of the PWM are controlled by the input signals.