Investigation of influence of parasitic impedances on demagnetization process in DC-DC Forward converter with high transformation ratio

摘要

This paper reports on a study and analysis of parasitic impedances that affect the switching activity of the Forward converter having a high ratio of transformation. The presented Forward converter system is based on the component dimensioning for power output of 400Watts and input voltage of 12Volts. The main objective of this investigation is to determine the origin and location of parasitic impedances responsible of disturbances interfering with the switching activity of Forward converter leading to deterioration of electrical performance specifically by stalling demagnetisation effect. The study and analysis have been conducted through experimental circuits at the frequency of 62.5 KHz. The voltage conversion task is carried out for the first circuit from 12V to 25V and the second circuit from 12V to 380V. Obviously, parasitic impedances result due to the presence of parasitic capacitors and leakage inductances identified in switching elements and windings of the transformer. Effects of the parasitic impedances are highly amplified by a high switching frequency and a high duty ratio for which the consequence is to stall the demagnetization process.