• Journal of Power Electronics
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• v.18 no.1
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• pp.300-308
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• 2018

An online estimation method for wireless power transfer (WPT) systems is presented without using any measurement of the secondary side or the load. This parameter estimation method can be applied with a controlling strategy that removes both the receiving terminal controller and the wireless communication. This improves the reliability of the system while reducing its costs and size. In a wireless power transfer system with an LCCL impedance matching circuit under a rectifier load, the actual load value, voltage/current and mutual inductance can be reflected through reflected impedance measuring at the primary side. The proposed method can calculate the phase angle tangent value of the secondary loop circuit impedance via the reflected impedance, which is unrelated to the mutual inductance. Then the load value can be determined based on the relationships between the load value and the secondary loop impedance. After that, the mutual inductance and transfer efficiency can be computed. According to the primary side voltage and current, the load voltage and current can also be detected in real-time. Experiments have verified that high estimation accuracy can be achieved with the proposed method. A single-controller based on the proposed parameter estimation method is established to achieve constant current control over a WPT system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.2
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• pp.61-68
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• 2004

Electric stimulation of teeth has been used for assessing pulp vitality. The principle is based upon the assumption that a subject feels the pain produced by electrical current stimulation of intradental nerve. Because of very high and wide range of impedance of the enamel, it is very difficult to determine stimulation levels regardless of teeth status. Most pulp testers adopt voltage stimulation method and thus, their stimulating threshold levels significantly depend on each individual. Therefore, a constant current stimulator is necessary to minimize the effect of wide variation due to different enamel thickness. And it is also necessary to test teeth vitality with a wide current range regardless of tooth impedance. In this study, we constructed a burst-wave type pulp tester to reduce the pain using a current stabilizing circuit with the maximum current of 150 uA.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.380-387
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• 2005

We report the performance of an open-frame type low-voltage high-current DC-DC converter module developed using an active clamp forward converter circuit and single ended rectifier. The converter module is designed with the specifications of an 3.3V output voltage, 30A output current, 100W output power and 36-75V input voltage. The synchronous rectifier is used to reduce the conduction loss at high current level and constant current control using precision PCB resistance is adapted to enhance the over current protection function in the system configuration. A prototype converter module is successfully implemented within 8mm height and quarter brick size (58x37mm) and recorded an $95W/in^3$ power density, 90.6$\%$ efficiency and 0.07$\%$ voltage regulation for the entire Input voltage range, thereby demonstrating its application potentials to future telecommunication electronics.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.632-634
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• 2004

First for high-qualify images and reducing process-error and driving speed, the designed 8-bit data driving circuit consists of a constant transconductance bias circuit, D-F/Fs by shift registers using static transmission gates, 1st latch and 2nd latch by tristate inverters, level shifters, current steering segmented D/A converters by 4MSB thermometer decoder and 4LSB weighted type. Second, we designed gray amp for power saving. These data driving circuits are designed with $0.35-{\mu}m$ CMOS technologies at 3.3 V and 18 V power supplies and simulated with HSPICE.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.5
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• pp.307-311
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• 2016

Although there are existing Residual Current Protective Device (RCD) including detect electric leakage and elements such as short circuit and surge, the occurrence of incidents caused by electric faults, including fire, are still constant. The purpose of this study is to analyze the causes of accidents through the electric field distribution in the interpretation of the fault contact breaker. Simulation results by the arc fault has shown the convergence of temperature and electric field to the defect. Through their simulation results, the main cause of erosion phenomena in circuit breaker bar is the electric arc by concentration of electric field not due to dissolve by temperature.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.1
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• pp.7-11
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• 2014

Induction motor is the most widely used to obtain the driving force in the industrial site. Induction motor is generally applied to the constant speed operation. Induction motor generates a high current at startup. So analysis for both steady state operation and start-up transient is required. In most cases, an equivalent circuit is used for the characteristics analysis of the induction motor. In this study, the two programs are applied to analyze for the rated speed as well as entire speed range. We confirmed that calculation results of the two programs are similar to each other.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.6 no.3
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• pp.50-56
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• 1992

The coupling coefficient K controls the characteristic behaviors of leakage transformer. The value of coupling coefficient K was obtained from th leakage flux of leakage transformer an ascertained from the variation due to the function of current. Therefore, this paper presented the equivalent circuit of leakage transformer consisting of Thevenin's constant voltage source and inductor as (1-K2)L2 which were proportional to parameter K. The proposed equivalent circuit verified the validity in designing the leakage transformer because it was in good agreements of the behaviors of ideal transformer (K is 1), leakage transformer (K is 0$\leq$K$\leq$1), inductor (K is 0).

• Journal of IKEEE
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• v.14 no.2
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• pp.9-15
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• 2010

In this study, we have been proposed the new type of a transcranial magnetic stimulation adopted a variable voltage capacitor with Cockcroft-Walton circuit and constant-frequency current resonant half-bridge inverter. This a transcranial magnetic stimulation has some merits compared with the conventional one. First, it doesn't require the high voltage transformer. And second, it has less switching losses, compact size and capability in adjusting the transcranial magnetic stimulation output energy precisely. In this paper, we have performed the output characteristics of a transcranial magnetic stimulation system which is well known as magnetic stimulation. The tested results are described as a function of pulse repetition rate and switching numbers of the half-bridge inverter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.7-10
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• 2003

ABS interface IC for automobiles was designed and their electrical properties were investigated. The voltage regulator was designed to operate in the temperature range from $-20^{\circ}\;to\;120^{\circ}C$ for automobile environment. ABS and brake signal were separated using the duty factor of same frequency or different frequencies. UVLO circuit and constant current circuit were applied for the elimination of noise.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.273-276
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• 2005

This paper presents an electronic ballast using a step down converter, a low frequency inverter for high pressure discharge lamp. The proposed ballast is composed of a full-wave rectifier, a step down converter operated as a current source with power regulation and a low frequency inverter with ignition circuit. The ignition circuit generates high voltage pulse of 1${\sim}$2[kV] peak, 130[Hz]. Moreover, it is able to reignite at regular intervals by protective circuit. As experimental results on the test, lamp voltage, current and consumption power are measured 132.5[V], 7.6[A] and 1,005[W], respectively. It was confirmed that the designed ballast operate the lamp with a constant power.