Pulse Width Modulation
In electronic power converters and motors, PWM is used extensively as a means of powering alternating current (AC) devices with an available direct current (DC) source or for advanced DC/AC conversion. Variation of duty cyclei n the PWM signal to provide a DC voltage across the load in a specific pattern will appear to the load as an AC signal, or can control the speed of motors that would otherwise run only at full speed or off. This is further explained in this section. The pattern at which the duty cycle of a PWM signal varies can be created through simple analog components, a digital microcontroller, or specific PWM integrated circuits.
Analog PWM control requires theg eneration of both reference and carrier signals that feed into a comparator which creates output signals based on the difference between the signals . The reference signal is sinusoidal and at the frequency of the desired output signal, while the carrier signal is often either a sawtooth or triangular wave at a frequency significantly greater than the reference. When the carrier signal exceeds the reference, the comparator output signal is at one state, and when the reference is at a higher voltage, the output is at its second state. This process is shown in Figure 3 with the triangular carrier wave in red, sinusoidal reference wave in blue, and modulated and unmodulated sine pulses