Output Low-ripple Cuk Converter Research

ABSTRACT:Comparing with the linear power supply, switching power supply has the advantages of high efficiency, smaller volume and light weight. For these advantages, switch power supply gradually replace the linear power supply. However, switching power supply has the disadvantages just like bigger output ripple. Some special applications such as measuring instrument, military industry and need to use low ripple power supply which switching power supply is unable to demand. So low ripple power supply technology get attentioned. Adding simple passive filter can reduce the output ripple but also increase the power of the volume, weight and cost. Besides that Cuk converter combine the advantages of other basic converter, with coupled inductor technique that can achieve zero ripple power supply.In this paper, first the topology of Cuk converter is studied. By coupling input and output inductors, Cuk converter can achieve output zero-ripple theoretically. Based on the analysis and model of Cuk converter, the output zero-ripple condition is solved. The leakage inductance of the transformer and the non-ideal coupling of the inductors will lead to bigger output ripple. Then the influences of the non-ideal componens to the output ripple of Cuk converter are given. Moreover, the close-loop design of isolated Cuk converter is analysed. Adding damp network can reduce the resonance peak of Gvd(s) function. Using the inner average current loop can improve the respone speed of the isolated Cuk converter. These two methods both improve the performance of Cuk converter.Finally a prototype is built to verify the analysis. The specification is:Vin=27V, Po=50W,f=100kHz. Cuk converter can operate stably without low frequency oscillation when the output voltage is5V, and the ripple of it is only20mV. The experimental results show that Cuk converter can realize low-ripple output and verify the analysis and close loop design method.