Chuan-Kuei Huang

Optimal Design of DC-DC Converter with LC Snubber by Hybrid Method

In this paper, it is first proposed that genetic algorithm and Taguchi method can be employed in the optimal design of DC-DC converter with LC snubber. The purpose of this optimal design is to lower the spike voltage Vdsp of power switch and hence reduce the cost in manufacturing circuit. It is great educational value for students and engineers. For the first step, we investigate the circuit parameters which will affect Vd and subsequently converge the range of circuit parameter value by means of genetic algorithm, and conduct the optimal design of prototype converter with Taguchi method. Compared with spike voltage Vdsp of non-optimal design circuit, the effect of optimal design is revealed. In suppressing spike voltage, the Vdsp measured from optimal design circuit is 115 V, and is actually 28.1% reduced. Therefore, using genetic algorithm and Taguchi method in the optimal design of converter with LC snubber is a more economic, practical and efficient of circuit design, which meanwhile can be easily applied to other electronic circuits and accomplish the optimal design of various quality characteristics.

Implementation of low loss Mn-Zn ferrite cores for power electronics applications

Simultaneous introduction of CaO, Co2O3 and MoO3 dopants into low loss manganese-zinc soft ferrites remarkably improves the power loss characteristic of the ferrite cores. Since the driving frequency of switching power supplies has been raised from several kHz to more than 1 MHz, the power loss of the magnetic devices must be reduced. The eddy current loss of soft ferrite will take a major proportion of iron loss in these high-frequency switching power supplies. An attempt was made to develop low loss Mn-Zn polycrystalline ferrites by increasing resistivity to decrease eddy current loss. Doped Mn-Zn ferrites were prepared by conventional ceramic technique and sintered at the temperature of 1320degC for 1-8 hours respectively in air. The DC resistivity was measured by using four-probe methods on sintered disks whose sides were polished and coated with a thin layer of silver paste as a good contact material. The magnetic permeability at room temperature was measured by using an impedance analyzer (Hewlett-Packard, Model HP4294A) with HP-16047 test fixture. The core loss of Mn0.58Zn0.37Co0.01Fe2.04 O4 ferrite doped with 0.08 wt% MoO3 is 370 mW/c.c at 500 kHz/70 mT

Design of the Chaotic Secure Communication Time-delay System by LMIs Method

In this paper, we utilize a proper Lyapunov function and Lyapunov theorem, combined with LMIs method, in order to design a controller L, which ensures the synchronization between the transmission and the reception ends of the chaotic secure communication system with time-delay of output state. Meanwhile, for the purpose of increasing communication security, we encrypt and decrypt the original to- be-transmitted message with the techniques of n-shift cipher and public key. The result of simulation shows that the proposed method is able to synchronize the transmission and the reception ends of the system, and moreover, to recover the original message at the reception end. Therefore, the method proposed in this paper is effective and feasible to apply in the chaotic secure communication system.

Optimal Design of Lossless Passive Snubber for DC/DC Converters

This paper presents an optimal design of lossless passive snubber for DC/DC converters, which offers an efficient and best design method. The proposed method can not only reduce the spike voltage Vdsp of a power switch in the circuit, but also raise the conversion efficiency of the converter. In this paper, we have used Taguchi method to create the optimal design of LC lossless snubber. It can overcome the chaotic drawback of trial-and-error method, the bias of one-factor-at-a-time experiments, and the disadvantage of too many trials for full-factorial experiments. In Taguchi method, the voltage V ds of power switch and source side current Iin are the quality characteristics of the circuit, and the snubber inductor L c, snubber capacitor CL, transformer leakage inductor Le, and switching frequency f are control factors which influence the circuit quality characteristics. According to the control factors and levels, this paper used an orthogonal array L9 (34) to implement experiments, and made a factor response table and graph. Eventually, the optimal values of the control factors Lc, CL, Le and f were decided and then increased ratio of S/N to 16.8%. The simulation results demonstrated that the proposed method applying to optimal design of LC lossless snubber circuit was feasible and efficient