Study On Nonlinear Phenomena In Flyback Converter And Its Application

Switching converters are hearts of electronic systems, such as communicationsystems and control systems, their stability, efficiency, and reliability will influencethe performance of the whole electronic systems. However, switching convertersexhibit a wealth of nonlinear phenomena, including bifurcations, coexisting attractors,and chaos. The prime source of nonlinearity presented in the circuits is the nonlinearcomponents and control method. Therefore, the study on the nonlinearity of DC/DCswitching converter is not only benefical to the engineering application, but alsoadvantageous to promote the improvement of the efficiency transform properties, andnonlinear science theory and practice also has a certain role.As the flyback has simple circuit topology, wide input voltage range, input andoutput electrical isolation, small size and light weight, low cost, good performance,high reliability, and many other advantage, it is widely used in switching powersupply design. Therefore, the paper studies flyback converter in-depth, first, analyzingcoexisting attractors penomena in voltage mode controlled flyback converter, thenanalyzing border collision bifurcations penomena in current mode controlled flybackconverter, finally using the above analysis parameter to design a LED power whichmakes use of flyback converter.The main fruits are included:(1) voltage mode controlled flyback converter is taken as example, coexistingattractor phenomena is found by digital simulation, then, using the discrete forms ofnonlinear dynamic to analyze the bifurcation action of the coexisting attractor andthe basin attraction, in the process of analysis, it is found that the coexisting attractorsphenomena which is caused by saddle node bifurcation, the reference voltage ofdifferent kinds of interference signal is add in the flyback converter to further explainthe existence of coexisting attractors, such as sine wave, triangle wave, rectanglewave. (2)current mode controlled flyback converter is taken for example, it is found thatwhen parameters changes, the system appears the border collision, PISM simulationillustrates the correctness of border collision phenomenon.(3) A LED fluorescent lamp driver is designed using IC SA7527and nonlinearanalysis experience, each part of circuit is analyzed, the topology structure of thecircuit is Flyback Converter, and the circuit adopts adjustable precision shuntregulators TL431, which matches up dual operational amplifiers LM358andphotocoupler EL817to build up the close-loop feedback, it carries out constantcurrent and constant voltage output.