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PWM (Pulse Width Modulation)

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Last updated date: 23rd May 2024
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An Overview of PWM

Pulse Width Modulation or PWM method is one of the most frequently used methods to control semiconductor devices. In the PWM technique, analog signals are created with the use of several types of digital devices. The created signals carry the impulse in the square wave form. Thus, it is dependent on time, which means it can be high or low at any given time. PWM reduced the power range gained by the electrical signal. It can be executed by turning the PWM signals into various parts. This technique is mostly used in communication systems.


What is Pulse Width Modulation?

The answer to the question what is pwm technique or pulse width modulatin technique is that it is a type of modulation technique used to modulate the signals. It is used to lower the average power conveyed by an electrical sign by changing over the signal into discrete parts. In the PWM technique, the sign's energy is circulated through a progression of pulses as opposed to a consistently fluctuating (analog) signal.


How is a Pulse Width Modulation Signal Generated?

A pwm signal can be generated by a monostable multivibrator. Monostable multivibrator has only one stable state and give single output pulse when external trigger is given. A monostable multivibrator circuit can be constructed using an operational amplifier comparator. The modulating signal structures one piece of the input to the comparator, while the non-sinusoidal waveforms the other piece of the information. The comparator looks at two signals and produces a PWM signal as its result waveform. In the event that the sawtooth signal or non sinusoidal signal is more than the modulating signal, the output is in a "High" state. The worth of the size decides the comparator yield which characterizes the width of the pulse created at the output.

PWm Signal


PMW Signal


Comparator generating pulse width modulation.


Duty Cycle of PWM

At the point when the signal is high, we refer to this as "on time". To portray how much "on time", we utilize the idea of duty cycle. Duty cycle is estimated in percentage. The percentage of duty cycle explicitly depicts the percentage of time a digital signal is on over an interval or timeframe. This period is the opposite of the frequency of the waveform.


On the off chance that a digital signal invests half of the time in and the other half off, we would agree that the digital signal has a duty cycle of 50% and looks like an optimal square wave. On the off chance that the percentage is higher than 50%, the digital signal invests more time in the high state than the low state as well as the other way around on the off chance that the duty cycle is under 50%. Here is a diagram that shows these three situations:

Duty Cycle


Duty Cycle

Ignition voltage variation with duty cycle.


Frequency of PWM

A frequency or period is well defined for controlling a specific servo. Regularly, a servo engine expects an update each 20 ms with a pulse between 1 ms and 2 ms. This compares to an obligation pattern of 5% to 10% at 50 Hz. Presently, assuming the pulse is at 1.5 ms, the servo engine will be at 90-degrees, at 1 ms, 0-degrees, and at 2 ms, 180 degrees. In outline, by refreshing the servo with a value between 1 ms and 2ms, we can get a full scope of motion.


PWM is additionally at present in an unambiguous communication system, and its duty cycle is being used to pass data on over communication channels. So, PWM is a technique to create low-frequency output signals from high-frequency pulses.


$\text{Frequency} =\frac{1}{\text{Time period}}$

Frequency of PWM


Frequency of PWM


Applications of PWM

PWM is used in many applications as given below.

  • In electronic gadgets, modulation is the utilization of a controlling or changing impact on something. We likewise refer to it as a variety in the pitch, strength, or tone of a frequency, as in the human voice.

  • We regularly experience modulation procedures being used for the control of gadgets like DC motors or LEDs.

  • PWM matched with maximum power point tracking (MPPT) is one of the important strategies for lowering a solar panel's output to work with its utilization by a battery.

  • You have some control over the brightness of a LED by changing the duty cycle. With a RGB (red green blue) LED, you have some control over the amount of every one of the three colors you need in the blend of variety by diminishing them with different sums.

  • The PWM procedure controls the fan inside a CPU of the PC, subsequently effectively disseminating the heat.

Summary

In this article, we learnt about the pulse width modulation (PWM) method which is used to modulate the signals. The utilization of pulse width modulation in different applications including complex control circuits has been discussed. We learnt that monostable multivibrator circuit constructed using comparator can be used to generate pwm signals along with the glimpse of applications and examples.

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FAQs on PWM (Pulse Width Modulation)

1. What function does the UVLO circuit perform?

The undervoltage lockout (UVLO) circuit sets the functional dc input voltage scope of the PWM regulator. There are two UVLO limits. At the point when the UVLO turn-on limit is surpassed, the PWM regulator turns ON. Assuming dc input voltage falls beneath the UVLO's turnoff threshold, the PWM regulator switches off.

2. What happens if the duty cycle multiplies with a high voltage level?

If you take a multiply duty cycle with high voltage level (which is a digital "on" or "1" state, all things the MCU is considered), you will get the average voltage level that the motor is seeing at that point.

3. Write the different types of pulse width modulation?

The three types of pwm are 

a) Trail Edge Modulation, 

b) Lead Edge Modulation, and 

c) Pulse Center Two Edge Modulation.