• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.242-245
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• 2007

To improve the efficiency of PDP TV, it should minimize the power losses transpired during AC-to-DC power conversion and PDP driving process. Generally the input power supply for PDP driving employes a two-stage power factor corrected converter, and it independently consists of sustain driver, which has high power consumption. However, such a circuit configuration has a difficulty for the PDP market requires low cost. To alleviate this problem, a new circuit composition is presented. It integrates input power supply with sustain driver in a single power stack. The input power supply of the proposed circuit has a single-stage structure to minimize power conversion loss, and it directly supplies power to the sustain driver so as to reduce the system size and cost.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.1 s.307
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• pp.45-52
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• 2006

In this paper, authors propose a step-up converter of pulse width modulation (PWM) and power factor correction (PFC) by using a novel loss-less snubber. The proposed converter for a discontinuous conduction mode (DCM) eliminates the complicated circuit control requirement and reduces the size of components. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of ac input voltage under the constant duty cycle switching. Thereupon, the input power factor is nearly unity and the control method is simple. In the general DCM converters, the switching devices are fumed-on with the zero current switching (ZCS), and the switching devices must be switched-off at a maximum reactor current. To achieve a soft switching (ZCS and ZVS) of the switching turn-off, the proposed converter is constructed by using a new loss-less snubber which is operated with a partial resonant circuit. The result is that the switching loss is very low and the efficiency of converter is high. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• Journal of IKEEE
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• v.22 no.4
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• pp.985-991
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• 2018

In this paper, an equivalent circuit reflecting the internal loss of the LLC resonant half bridge converter was proposed and a steady state characteristic equation including the loss factors was derived. Using the results, the frequency characteristics of I/O voltage gain and input impedance were compared with the lossless model In order to verify the proposed model and the derived equation, the main components of the 1kW class LLC resonant half bridge converter were selected under the same conditions and the steady state characteristics such as voltage gain and input impedance were compared. In particular, to compare more closely the steady state error of the two models, we observed the change in switching frequency with respect to the load current, which is considered to be the most important in the actual circuit design stage. As a result, it is confirmed that the error of the operating frequency is significantly improved from the proposed model and the analysis result.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.2
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• pp.149-155
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• 2023

Photovoltaic power generation is the most familiar power generation facility among new and renewable energies, and its supply began to expand about 10 years ago, and at this point, interest in solutions and technologies for system maintenance management is increasing. In particular, it is necessary to take measures to maximize the overall efficiency of the solar power generation system, whether or not there is an abnormality in the solar power generation system, and when to replace parts. The PV inverter, one element of the photovoltaic power generation system, is a power conversion system that relies on power switching devices, and DC-Link capacitors are used according to the configuration of DC/DC converters and DC-AC inverters. These DC capacitors also affect system safety (Safety) through renewable energy facilities due to the decrease in power generation of PV inverters, power loss, and increase in harmonics (THD, total distortion of AC output current) due to aging and deterioration due to long-term use. factors can be analyzed. Therefore, in this paper, the PV inverter operating characteristics according to the DC capacitor capacity state currently operating in the photovoltaic power generation system were considered, and research contents were proposed to secure the safety and reliability of renewable energy facilities.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.3
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• pp.193-200
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• 2006

This paper suggests a 6-pulse-shift converter structure with PWM current-source inverter based on buck-boost configuration to improve the efficiency and to reduce the switching frequency of inverter for photovoltaic generation system, the device can be operated as interface system between solar module system and power system grid without energy storage cell. The circuit has six current-source buck-boost converter which operate chopper part and kas one full bridge inverter which make a decision the polarity of AC output. Therefore, the proposed PWM power inverter has advantages such as the reduction of witching loss and realization of unity power factor operation. The theoretical backgrounds are discussed and the input-output characteristics for the implemented prototype inverter using TMS320F2812 are verified experimentally in this paper.

• Journal of IKEEE
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• v.22 no.3
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• pp.613-618
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• 2018

In this paper, an active snubber type flyback converter was applied to a 60W class adapter and its test results are reported by producing a prototype. Especially, the prototype of the adapter was designed for both input voltage of 110V and 220V. The output voltage was designed for 60W with 19V class which is the most commonly used in laptops. The prototype was designed to a volume of about $50cm^3$ and a power density of about $1.22W/cm^3$ to minimize the size and verify portability. The maximum efficiency of the prototype was 90.88% at its maximum load of 60W against input voltage change and 91.04% was observed at 60W under input voltage of 220V. Furthermore, the stability of the output voltage against load power was observed to be within about 0.07%.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.205-212
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• 2004

In this paper the design of a 1-[KVA] fuel cell powered line-interactive UPS system employing modular (fuel cell & DC/DC converter) blocks is proposed. The proposed system employs the two fuel cell modules along with suitable DC/DC converters and these modules share the DC-Link of the DC/AC inverter. A supercapacitor module is also employed to compensate for the instantaneous power fluctuations and to overcome the slow dynamics of the fuel processor. The energy stored in the supercapacitor can also be utilized to handle the overload conditions for a short time period. Due to the absence of batteries, the system satisfies the demand for an environmentally friendly and dean source of the energy. A complete design example illustrating the amount of hydrogen storage required for 1hr power outage, and sizing of supercacpacitor for transient load demand is presented for a 1-[KVA] UPS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.306-306
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• 2007

최근, LED 구동 인버터, DC-DC 컨버터, AC-DC 컨버터 및 형광등 ballaster 등의 고전압전원장치등에 압전변압기를 적용하고자 하는 연구가 활발히 진행되고 있다. 순수한 $PbTiO_3$는 큐리온도($490^{\circ}C$)가 높고, 기계적강도가 크며, 비유전율(약 200 정도)이 작다. 또한, 두께방향 진동의 전기기계 결합계수 ($K_t$)가 윤곽진동의 전기기계 결합계수($K_p$)보다 크므로 두께방향의 진동모드를 이용한 벌크파 진동자의 경우 윤곽진동방향으로 불요신호(spurious signal)가 적고, 작은 grain size($1\;{\mu}m$정도)로 미세가공이 가능하여 고주파 재료로 이용되고 있다. 압전변압기의 출력 전력을 향상시키기 위해서는 적층으로 제작하여야 하는데 적층 압전변압기 제작시 층간의 내부 전극이 도포된 상태에서 소결하여야 한다. 이때 소걸 온도가 높으면 Pd 함랑이 높은 전극을 사용하여야 하는데 Pd 전극의 가격이 비싸 소자의 경제성이 떨어지게 된다. 따라서 순수한 Ag 전극을 내부전극으로 사용하기 위해서는 $900^{\circ}C$ 이하에서 소결이 가능하여야 한다. 따라서 본 연구에서는 $(Pb,Ca,Sr)Ti(Mn,Sb)O_3$ 조성을 이용하여 $900^{\circ}C$ 이하의 저온소결이 가능한 두께방향진동모드 적층 압전변암기를 제작하여 그에 대한 전기적 특성을 조사하였다.

• Journal of IKEEE
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• v.26 no.4
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• pp.584-589
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• 2022

For DC-AC power conversion from a high-voltage photovoltaic panel to a single-phase grid, the two-stage transformerless inverter with a buck-boost converter followed by a full-bridge inverter is widely used. To avoid an excessive leakage current due to the large parasitic capacitance of the photovoltaic panel, the full-bridge inverter can only adopt the bipolar PWM which results in much higher power loss compared to the unipolar PWM. In order to overcome such a poor efficiency, this paper proposes a new topology in which an IGBT and a diode for circuit isolation are added to the buck-boost converter. The proposed circuit isolation method allows the unipolar PWM in the full-bridge inverter without any increase in the leakage current so that the overall efficiency can be improved. The validity of the proposed solution is verified by computer simulation and power loss calculation.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.983-985
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• 2002

This paper is the machine that is able to estimate a new built power convertor in a production line. Generally, this machine test can be achieved by connecting it to a dynamometer consisting of a three-phase machine joined by a rigid shaft to a DC load machine. But the proposal system is controlled to create some specific load characteristic needed for the test without any mechanical equipment. The suggested test stand consists only of a converter to be test and a simulator converter. Both devices are connected back-to-back on the AC-side via smoothing reactors. The simulator operates in real-time as an equivalent load circuit, so that the device under test will only notice the behaviour of a three-phase machine under consideration of the load. And then, to obtain a superior characteristic for dynamic reference used the feedforward control.