v Ar −Ac v Ar −Ac vg1, vg2
SPICE for Power Electronics and Electric Power, Second Edition
t δ For switch S1 t For switch S2 δ T 2 T t
FIGURE 9.1 PWM control.
where Ar is the peak value of the reference signal vr, and Ac is the peak value of the carrier signal vc. The PWM modulator can be used as a subcircuit to generate control signals for a triangular reference voltage of one or more pulses per half cycle and a DC carrier signal. The PSpice schematic for generating PWM control signals is shown ref produces a pulse signal at a reference (or switching) frequency of fs = p × fo, where p is the number of pulses per half cycle and fo is the frequency of the output voltage. A DC carrier signal Vcr as shown in Figure 9.2(a) is compared with the reference signal Vref by an ABM2 device as in Figure 9.2(b). Vref is a triangular signal at the carrier frequency of fc. Vx is a pulse signal at an output frequency of fo at a 50% duty cycle, and..