Improvement And Realization Of Cross Regulation Of Multiple Output Flyback Converter

With the rapid development of electronic technology,electronic equipment needs more different levels of voltage source for its power supply,and sometimes even needs a negative voltage.If a module circuit's power is supplied by only one power source,the entire system requires multiple modules of power supply,and it will lead shortages such as increasing weight of device,enlarging volume,increasing costing,etc.The Flyback converters are widely used in small and medium switching mode power supply(SMPS)because of its advantages of simple topology,electrical isolation of input and output,a wide range of boost and buck,so by increasing the transformer winding numbers of Flyback converters to output different levels of voltage can meet the requirements of power of the equipment.Therefore,this article design a prototype which is a +15V/1A,-15V/1A,5V/1.5A three-ways output Flyback switching mode power supply.This article firstly makes a comprehensive analysis on topology structure and working principle of Flyback converter,and makes a detailed analysis of the transmission process of power of the Flyback converter under two different operating modes,summarizes the advantages and disadvantages of Flyback converter when working in these two different working modes,and determine the model used by prototype.On this basis,this paper leads the concept of cross regulations of multiple output switching mode power supply,analyzes influencing factors of cross regulations of Multiple Output Flyback Converter and improving methods which are widely used so far,makes a comprehensive improvement of cross regulations by using methods of Voltage weighting method,RCD clamp circuit,and optimizing parameters and structure of transformer,increasing the false load etc.The article uses UC3845 as the main control chip,designs schematic circuit diagram of prototype and makes the Flyback transformer based on theoretical analysis,and makes the simulation experiment of schematic diagrams under the Saber software environment,verifies its feasibility.The paper draws the PCB board of prototype circuit,makes the physical prototype,and uses voltage weighting feedback control method and traditional single-loop feedback control method to test it,the result shows that the method of comprehensive improvement in this article has improved cross regulation well,meets the requirements of design.