• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.164-166
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• 2002

HVT(High Voltage Transformer) has been used to drive a magnetron in a microwave oven. This has some problems which are heavy weight, low efficiency and limit of output. To overcome these problems, this paper proposes a boost input type active clamp AC-DC converter for magnetron driving featuring the high efficiency and improved EMI characteristics. To verify the validity of the proposed converter operation, the prototype converter of 700W was built and tested.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.27-33
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• 2016

A pulse-width modulation (PWM) method for common mode noise reduction in a PWM inverter connected to a single-phase grid is proposed in this study. The extensively used conventional switching method may experience common mode voltage problems, which generate current leakage and electromagnetic induction problems. In the proposed switching method, the neutral point of the output voltage is always fixed at both ends of the input voltage to reduce common mode noise. The validity of the proposed method is proven through simulation and experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1947-1953
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• 2009

Metal halide (MH) lamps have been largely used due to high luminous efficiency, good color rendering, and long life. Since the metal halide lamps have problems of high ignition voltage and acoustic resonance. Thus, the design of ballast is very difficult for engineers. This paper proposes prototype of electric ballast in order to solve above two problems. The proposed electric ballast is consisted of EMI filter, full wave rectifier circuit, active PFC, DBI(Dual Buck Inverter), dimming circuit and ignitor circuit. The DBI supplies both rectangular voltage and current to the lamp. As the result of the experiment, the acoustic resonance was eliminated and the ignitor circuit was designed to generate high ignition voltage than 5kV. It makes the dimming circuit possible to control the lamp power in range between 230W and 350W.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.10-18
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• 2008

This paper presents the design and imelementation of an electronic ballast with a passive PFC structure from which acoustic resonance of the metal halide lamp was removed by introducing the frequency modulation(FM) method. The proposed ballast consists of an EMI filter, passive PFC circuit full-bridge inverter, LC resonance type igniter and a circuit for removing acoustic resonance. The FM method solved two problems associated with single frequency driving: variation of the acoustic resonance range according to lamp aging and the acoustic resonance range discrepancy caused by different materials sealed inside the arc tube and their pressures for arc tubes of identical sizes from different manufacturers. Performance of the prototype developed for this study of the electronic ballast for 1[kW] metal halide lamp was verified by evaluating its optical conversion efficiency, input PF, input current THD and power conversion efficiency.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.4
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• pp.346-352
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• 2002

A novel Zero Current Switching(ZCS) Pulse Width Modulation(PWM) boost converter with dual mode for reducing two rectifiers reverse recovery related losses is proposed. The switches of the proposed converter are operating to work alternatively turn-on and turn-off with soft switching condition In the every cycle and the proposed converter reduces the reverse recovery current, which is related switching losses and EMI problems, of the free-wheeling diode$(D_1, D_2)$ by adding the resonant inductor Lr, in series with the switch $S_1$. The switching components$(S_1, S_2, D, D_1)$ in the proposed boost converter are subjected to minimum voltage and current stresses same as those in their PWM counterparts because there are no additional active switches and resonant elements compared with the conventional ZVT PWM $converters^{[2]}$. The operation of the proposed converter, in this paper, is analyzed and to verify the feasibility of the characteristics is built and tested.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.50-56
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• 2015

An efficient fast response hysteretic buck converter suitable for mobile application is propoesed. The problems of large output ripple and difficulty in using of small power inductor that conventional hysteretic converter has are improved by adding ramp generator. and the changeable switching frequency with load current is fixed by adding a delay time control circuit composed of PLL structure resulting in decrease of EMI noise. The circuits are implemented by using BCDMOS 0.35um 2-polt 4-metal process. Measurement results show that the converter operates with a switching frequency of 1.85MHz when drives 80mA load current. As the converter drives over 170mA load current, the switching frequency is fixed on 2MHz. The converter has output ripple voltage of less 20mV and more than efficiency 85% with 50~500mA laod current condition.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1065-1073
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• 1999

This paper analyzed the ground bounce caused by the power plane resonance in the multilayered printed circuit board(PCB) using the Haar-wavelet-based Multiresolution Time-Domain (MRTD). In conventional Finite-Difference Time-Domain(FDTD), the highly fine vertical cell is needed to represent the distance between $V_{cc}$ plane and ground plane since the two planes are very close. Therefore the time step $\Deltat$ must be very small to satisfy the stability condition. As a result, a large number of iterations are needed to obtain the response in wanted time. For this problem, this paper showed that the computation time can be reduced by application of the MRTD method. The results obtained by the MRTD agree very well with those by FDTD method and analytic solutions. In conclusion, this paper proved the efficiency and accuracy of MRTD method for analyzing the EMI/EMC problems in PCB.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.46-53
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• 2009

A new zero-current switching LLC resonant post-regulator for multi-output power system is proposed in this paper. A conventional LLC resonant converter employs extra non-isolated DC/DC converters to obtain tight-regulated multi-slave output voltages. Therefore, it has several serious problems such as a poor efficiency and high cost of production. The proposed post-regulator features low voltage and current stress across the output rectifier diodes and power switches. Moreover, the proposed post-regulator requires only one power switch instead of the bulky and expensive non-isolated DC/DC converter. Therefore, it features a simple structure and lower cost. Especially, since the proposed post-regulator can ensure the ZCS of all power switches, it has very desirable advantages such as more improved EMI characteristics and reduced switching losses. Finally, to confirm the operation, validity, and features of the proposed circuit, experimental results from a proposed zero-current LLC resonant post-regulator are presented.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.2
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• pp.143-148
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• 2014

Conventional wireless power transfer methods based on coupled magnetic fields need a complex winding structure on the surface of the energy transfer and shows poor efficiency near metal objects due to the eddy current effect. In this study, to mitigate these problems, we investigate an electric field-coupled power transmission system, which is less prone to metal object problems and EMI. Because of the fundamental physical limit in the size of link capacitances, a half-bridge converter with an impedance matching transformer is proposed and the design procedure is derived to provide a soft-switching scheme. Hardware implementation shows that the proposed scheme with a pair of 10cm by 10cm copper plate can power a 1.4W USB FAN in a separation of 0.2mm by using insulating paper when driven by 227 kHz gate pulse.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.6
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• pp.813-821
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• 2017

This paper presents the study result on a realization of wireless umbilical device for missile systems. In general, a missile system is connected to a fire control equipment via an umbilical connector to get the electrical power for its internal equipment and communicate with each other. And these connectors inherently have many problems of mis-contact between pin and socket, and mis-separation during missile firing, etc. A wireless umbilical device using LC resonance is devised to solve these problems of the current technology. For hundreds of watts power transmission under the missile system environment of restricted space, we designed and made a prototype of wireless umbilical device. And we tested this wireless umbilical device with an aluminum cylinder having cutout windows which simulate missiles. We realized that the wireless technology can be used as a substitute for the conventional umbilical connectors, and EMI and environment tests should be followed further.