Design And Implementation Of The UC3842Multiple-output Flyback Switching Power

Power has played a key role in the era of rapid development of contemporary economicand technological，The power supply is an important application field of power electronicstechnology. At present, with the rapid development of power supply technology, switchingpower supply go toward the high-frequency integrated direction. Compared to linearregulators, switching power supply design is more complex，some indicators may not be goodas linear regulator, and the noise is big,but because of its small size, light weight, highefficiency, stable performance and other prominent advantages, the high-frequency switchingpower supply is favored and used widely.In this paper, using the characteristics of the flyback transformer, a multiport flybackswitching power supply is designed based on the UC3842, which provides five output voltageand can adjust the PWM output to ensure stable output voltage as the input voltage changes.This paper introduces several commonly used switching power supply topology, theappropriate topology for this article is selected by analyzing，and a detailed parameter offlyback transform structure is carried out.At the same time, feedback control mode ofswitching power supply is compared and choosed.The dissertation briefly describs thestructure of the PWM control chip UC3842,and illustrates peripheral circuit design ofUC3842in detail, including EMI suppression circuit, the rectifier circuit, snubber circuit. Theentire block diagram of the system and a brief description of the work process are introduced.According to the basic requirements of the high-frequency transformer core material, detailedanalysis of the transformer core selection method (the AP law and KG method) is madeout,by which the parameter of high-frequency transformer is calculated and designed,including the duty cycle, the primary side and the output side turns, wire diameter.At last weuse Saber software to model and simulate the switching power supply,and explain thesimulation waveform.Also the prototype is tested and the test data is analyzed and verificated.Experimental results show that: the design of switching power supply has stable output,low ripple, good voltage regulation,nice electromagnetic compatibility, etc,it has a highapplication value.