Study of Measurement Approach of Loop Gain of Converter

In this paper, an approach by using the Agilent 4395A to measure the loop gain of the power supply has been deeply developed. The main issues have been investigated as the following: (1). Measurement techniques about the parasitic parameters of the filtering components will be studied. One is how to test of the electrolyte capacitor by Agilent 4395A; another is how to test dynamic inductance of filter inductor by Tektronix TDS5052 with TDSPWR3 software; (2). A measurement approach for loop gain has been put forward; (3). A prototype has been made up and its loop gain has been tested to verify the proposed approaches; (4). The experimental result has first revealed that the biggest analytic error of the loop gain occurs nearby about the resonance frequency of low pass filter. It can be explained that the error results from the equivalent resistor of the power diode and MOSFET; (5). Based on considering the equivalent resistor, a novel accurate small-signal model of buck converter has been proposed to reduce the theoretic error. The proposed approaches, model and other results have provided a powerful tool to analyze and design a power supply