Design Of High-frequency And High Efficiency Multiple-output Power Supply

This paper gave the research and experiment on high frequency, high efficiency designthemes of low-power DC/DC converter, which intends to be conducive to the furtherdevelopment of low power DC/DC converter with high power density.Firstly, a great deal of data was consulted, after comparing of several different low powerisolated DC/DC converters, Low-side active clamp forward converter has been selected to bethe main circuit topology. And detail operation principle is presented.Secondly, for high frequency efficiency requirements in the design specifications, manynew technologies such as soft-switch, synchronous rectifier, planar transformer, and othertechnologies have been used in the converter, to improve power efficiency and power density,and show the detailed analysis and research of these technologies. Around the UCC2891PWM controller, a detailed analysis of the design step of active clamp forward converter isgiven, and various parts of component parameters of the power circuit and control loop areanalyzed and calculated to complete the UCC2891peripheral circuit design. The loss ofvarious components of the power stage is calculated, and the circuit is optimal designed.Thirdly, on the way of the synchronous rectifier, some methods of synchronous arediscussed. First capacitively coupled synchronous rectification is selected and achieved, onthe basis of further analysis of the power efficiency, external control chip NCP4303is usedfor driving. Efficient Step-Down LM2676series switching regulator is used to make quadratictransform of the output voltage. The multi-output of3.3V,5V and12V is achieved.Finally, two high-frequency switching power supply prototypes are produced based ontheoretical analysis and circuit design, with the method of capacitively coupled synchronousrectification and rectification of using driver control chip. After optimization improvements,the prototype’s performance is stable. The input voltage range between36Vdc~72Vdc; thefrequency is450~500kHZ; maximum output power is110W; the maximum efficiency canreach87.4%. Experimental data and the results show that the performance indicators of the converter is achieved the expected requirements, verifies the correctness of theoreticalanalysis and design ideas.