Chaos Theory Is Applied Research, In The Switching Power Supply

Switching mode power supply (SMPS) is a high non-linear dynamic system, which has plenty of non-linear phenomena, such as bifurcation and chaos. When the circuit parameters change, the chaotic phenomena may appear in SMPS. Therefore, under certain condition, it is significant and helpful to analyze the irregular movement in SMPS under the guidance of chaotic theory and improve the performance of SMPS. The dissertation studies chaos phenomena and its mechanism systematically in buck converter and forward converter and how to reduce its EMI using the feature of chaos. The main work of this paper is presented as follow:1. Taking the voltage-mode controlled buck converter as an example, the discrete mapping of buck converter is proposed. When the converter is operated on the frequency of 100 KHz, bifurcation and chaos in buck converter are investigated based on the mapping with the load resistor R as bifurcation parameter. Then, the simulation circuit is estabilished in PSpice, and the discrete mapping is verified by the simulation.2. Adding the simplified model of power transformer into the discrete mapping of buck converter, the discrete mapping of forward converter is found. Then, the mapping is iterated and the bifurcation diagram is acquired with the input voltage V_I, the load resistor R, the leakage inductor L_e of power transformer as bifurcation parameters respectively. According to the bifurcation diagram, the effect of those parameters on bifurcation and chaos in forward converter is analyzed in detail.3. The experimental circuit is designed. On the one hand, the experimental circuit is simulated in PSpice to verify feasibility of the circuit design; on the other hand, bifurcation and chaos are investigated with the input voltage V_I, the load resistor R, the leakage inductor L_e of power transformer as bifurcation parameters respectively in forward converter. And thus the reasonability of the discrete mapping of forward converter is verified. And also according to the simulation results, it can be observed that EMI in the forward converter is apperantly reduced when the converter works on the chaotic state.4. The experiment is conducted with the input voltage V_I as bifurcation parameter, and bifurcation and chaos in forward converter can be observed through the oscilloscope. Therefore, the iterativing results and the simulation results are verified again. And also it can be concluded from the spectrum of output voltage that the EMI level can be reduced based on the feature of chaos when the converter operates on bifurcation and chaos.