Pulse width modulation (PWM) components

Multisim includes the PWM, PWM Complementary, and PWM 3 Phase generators.

These components model simple PWM generators. The PWM component's model consists of a comparator and a triangular waveform generator as shown below.

The model parameters Frequency, TriangleMin, and TriangleMax are used to set up the reference triangular voltage source Vref. 

The model parameters OutputVoltage, RiseFallTime, and PwmMode are used to set up the ideal comparator U2. 

The rise/fall times force the output to change as a ramp with a duration equal to the value of the rise/fall time parameter. When selected, PwmMode detects crossings in the input signals and cuts back the simulation time step during such an event. This ensures a highly accurate PWM signal. Delays to simulation time for this algorithm are negligible in the vast majority of cases, so we recommend that you leave this parameter selected. 

Example:

Parameters used:

Frequency:  1 kHz
TriangleMin:  -1 V
TriangleMax:  1 V
OutputVoltage:  5 V
RiseFallTime:  1 ns

Result:

The PWM Complementary component contains an additional output pin for the complement of the output. 

The PWM 3 Phase component consists of three identical PWM Complementary components. They share the same reference signal.