Pulse Width Modulation
[1] What Is PWM ?
- Pulse Width Modulation Is Also Known As Pulse Duration
Modulation (PDM).
- Here, As The Name Suggests, The Width Of The Pulse Is Varied
In Proportion To The Amplitude Of The Signal.
- Since The Width Is Changing, The Power Loss Can Be Reduced
When Compared To PAM Signals.
- In The PWM Technique, The Signal’s Energy Is Distributed
Through A Series Of Pulses Rather Than A Continuously Varying
(Analogue)
Signal.
[2] How To Signal Generat ?
- A Pulse Width Modulating Signal Is Generated Using A
Comparator.
- The Modulating Signal Forms One Part Of The Input To The
Comparator, While The Non-Sinusoidal Wave Or Sawtooth Wave
Forms The Other Part
Of The Input.
- The Comparator Compares Two Signals And Generates A PWM
Signal
As Its Output Waveform.
- If The Sawtooth Signal Is More Than The Modulating Signal,
Then The Output Signal Is In A “High” State.
- The Value Of The Magnitude Determines The Comparator
Output Which Defines The Width Of The Pulse Generated At The
Output.
[3] Types Of Pulse Width Modulation Technique
- There Are Three Conventional Types Of Pulse Width Modulation
Technique And They Are Named As Follows:
(A) Trail Edge Modulation – In This Technique, The Signal’s Lead
Edge Is Modulated, And The Trailing Edge Is Kept Fixed.
(B) Lead Edge Modulation – In This Technique, The Signal’s Lead
Edge Is Fixed, And The Trailing Edge Is Modulated.
(C) Pulse Center Two Edge Modulation – In This Technique, The
Pulse Centre Is Fixed And Both Edges Of The Pulse Are
Modulated.
[4] Advantages & Disadvantages Of PWM :
Advantages :
- PWM Technique Prevents Overheating Of LED While Maintaining
Its Brightness.
- PWM Technique Is Accurate And Has A Fast Response Time.
- PWM Technique Provides A High Input Power Factor.
- PWM Technique Helps Motors Generate Maximum Torque Even
When
They Run At Lower Speeds.
Disadvantages
- As The PWM Frequency Is High, Switching Losses Are
Considerably High.
- It Induces Radio Frequency Interference (RFI).
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