In this article, you will learn how to determine the gain of a control system using different methods, such as open-loop transfer function, closed-loop transfer function, Bode plot, and Nyquist plot.

The Nyquist plot is a graphical technique that shows the mapping of the open-loop transfer function from the complex plane to the complex plane as the frequency varies from zero to infinity.

To perform the measurements, you inject a small AC signal into the power supply’s control-loop circuit and measure the loop’s gain and phase shift. By measuring the gain and phase, you can plot them ...

This, however, can only be done if we know the closed-loop transfer function. Usually though, the closed-loop transfer function is not known. In cases where the closed-loop transfer function is not ...

For this, the amplitude response and the phase response are determined from the transfer function of the system and plotted as a graph with the gain and the phase as a function of frequency.

Fig. 1. Bode plot of a DC/DC converter. The phase margin of this converter is indicated as a very respectable 78 degrees and the gain margin, indicates a less than stellar, but acceptable 6.7 dB.

This study suggests a method to derive an approximate but sufficient formula of an open-loop transfer function for examining the oscillation seen for power devices connected in parallel. The stability ...