Figure 3.2 shows the principle of pulse width modulation (PWM) control, but it does not provide any information on how we can produce the modulation within a real hardware circuitry. In order to keep the pulse frequency constant, a carrier signal is necessary. Switches change their conduction states at moments of time that are determined by the intersections between our reference voltage and a triangular high-frequency signal with a fixed magnitude equal to unity. This operation is shown in Figure 4.1.
The frequency of the pulses is kept constant while their duty cycle is modulated. This is known as