Pulse width modulation (PWM) is a method of changing the duration of a pulse with respect to the analog input. The duty cycle of a square wave is modulated to encode a specific analog signal level. This pulse width modulation tutorial gives you the basic principle of generation of a PWM signal. The PWM signal is digital because at any given instant of time, the full DC supply is either ON or OFF completely.
PWM method is commonly used for speed controlling of fans, motors, lights in varying intensities, pulse width modulation controller etc. These signals may also be used for approximate time-varying of analogue signals. Below you can see the pulse width modulation generator circuit diagram (pulse width modulator) using op amp. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. Pulse width modulation dc motor control is one of the popular circuits in Robotics.
PWM method is commonly used for speed controlling of fans, motors, lights in varying intensities, pulse width modulation controller etc. These signals may also be used for approximate time-varying of analogue signals. Below you can see the pulse width modulation generator circuit diagram (pulse width modulator) using op amp. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion. Pulse width modulation dc motor control is one of the popular circuits in Robotics.
Circuit diagram
Components required
- Dual power supply (+Vcc and -Vcc)
- 741 op amp IC
- Signal generator
Working of Pulse width modulator
- In this circuit op amp acts as a comparator.
- It compares both the input voltages, i.e. the sawtooth waveform and the message signal (sine wave).
- The duration for which the instantaneous value of sine wave is above that of sawtooth, op amp switches to +Vcc since the sine wave input is connected to the non inverting input of the op amp.
- Also when the value of sine wave is less than the instantaneous value of sawtooth, op amp switches to -Vcc.
- Thus we get a pulse waveform that swings between +Vcc and –Vcc.
- That is the pulse width changes according to the message signal (Width of the pulse is modulated)
Output wave form
Important terms associated with PWM:
Period (T)
How long each complete pulse cycle takes.
Frequency (F)
How often the pulses are generated. This value is typically specified in Hz (cycles per second).
Duty Cycle (D)
Refers to the amount of time in the period that the pulse is active or high. Duty Cycle is typically specified as a percentage of the full period.
How long each complete pulse cycle takes.
Frequency (F)
How often the pulses are generated. This value is typically specified in Hz (cycles per second).
Refers to the amount of time in the period that the pulse is active or high. Duty Cycle is typically specified as a percentage of the full period.
Simulation
Components pin out
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