Oscillators Circuit DiagramsProteus Simulation Based Projects

Schematic Circuit Diagram PWM-Pulse Width Modulation proteus simulation

Combination of astable multi vibrator, Integrator, Comparator gives the PWM circuit. But if the frequency of operation is to be variable, then it becomes difficult, as it is necessary to change the knobs of frequency adjustment and resistors of the integrator to be adjusted to match with input frequency in addition to the duty cycle knob.

Op-Amp as Duty Cycle Controller

Op-Amp as Duty Cycle Controller

To simplify this requirement, Voltage Controlled Oscillator is used as above. This is provided by the manufacturer in the data sheet of LM 324 IC. By making some modifications and adding a few components, we can design a PWM circuit for motor speed control or Light brightness control etc.

Simulation of Op-Amp as Duty Cycle Controller

Schematic Circuit Diagram PWM-Pulse Width Modulation proteus simulation

The square wave whose frequency can be adjusted with the frequency knob, is converted to a triangular wave. The Duty cycle adjusting knob is used to vary the duty cycle (which is Red line on the triangular wave form in the above image).

When the instantaneous triangular wave voltage is lesser than the dc voltage of duty cycle knob, the output is in High state and vice versa. This can be reversed by reversing the V+ and V- inputs of the output stage Op-Amp.

Simulation – PWM

Pulse-width modulation, or pulse-duration modulation, is a method of reducing the average power delivered by an electrical signal, by effectively chopping it up into discrete parts. The average value of voltage fed to the load is controlled by turning the switch between supply and load on and off at a fast rate.
PWM is used in many applications, ranging from communications to power control and conversion. For example, the PWM is commonly used to control the speed of electric motors, the brightness of lights, in ultrasonic cleaning applications, and many more.
Pulse Width Modulation (PWM) is a technique to generate low-frequency output signals from high-frequency pulses. Rapidly switching the output voltage of an inverter leg between the upper and lower DC rail voltages, the low-frequency output can be thought of as the average voltage over a switching period.

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