Development Of 2.5kW Phase-Shifted Full-bridge Converter

Aviation static inverters(ASI)are important equipment on airplanes.Based on design requirements of high power density and integrated design,two-stage high-frequency link inverters have been widely used.According to the needs of the project,this paper develops a 2.5k W DC / DC converter with a switching frequency of 100 k Hz as the front part of the aviation static inverter.According to the operating characteristics,the structure and control loop of the converter were optimized to meet the requirements of the index.This article first introduces the operating conditions and structural types of ASI.Although a single-stage aerostatic converter has the advantage of simple structure and fewer components,it has a poor response to the input voltage and load.Two-stage high-frequency link inverters increase the complexity of the topology,but it can adapt to a wider input voltage range and meet the development trend of modularization and integration.Therefore,the two-stage high-frequency link inverter has become the mainstream of the application.Secondly,the types of soft switching circuits and the main control methods of switching power supplies are introduced.The phase-shifted full-bridge soft-switching circuit was selected as the front-stage topology according to the operating conditions of the wide-voltage input.Phase-shifted full-bridge converters have the problems such as difficulty in ZVS of lagging leg,secondary-side voltage oscillation,and loss of duty cycle.However,in the application of the low-voltage and high-current condition,the realization of ZVS is much easier and the loss of duty cycle is more serious.Therefore,this design focuses on the use of a CDD absorption circuit to suppress the secondary side voltage oscillation,and to compensate for the loss of duty cycle through reasonable parameter design.In addition,this article also solves the problems of high current sampling at high frequencies and loss of slope compensation near full duty cycle.Finally,according to the internal circuit of the control chip UCC2895,a closed-loop simulation model was established to verify the rationality of the control loop and main circuit parameters.A prototype was assembled to verify the design of this paper.The applicability of the phase-shifted full bridge to low voltage and large current and wide input voltage range was proved,and the design requirements were completed.