• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.174-176
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• 2003

The power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. This paper proposes a skillful and a concise PWM DC-DC converter employing both zero voltage and zero current high frequency switching(ZVCS) operation. The Proposal ZVCS circuit is composed with resonant circuit using active resonant condenser. And this circuit provides switches with ZVS and ZCS by quasi resonant only that switching transients appear. This operation results in reduction of stress and losses in the power devices and resonant components. Some simulation results are included to confirm the validity of the analytical results.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.409-411
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• 1999

Usually, in many applications. high frequency resonant inverters are used and the ZVS(Zero Voltage Switching) or ZCS(Zero Current Switching) techniques are used to improve the efficiency of resonant inverters. In this paper, a new switching scheme is proposed to improve the efficiency of resonant inverters which is based on the plan to keep the unity output displacement factor under the variable resonant frequency. The detail algorithm of the proposed switching sheme and the simulation results are presented.

• Journal of Power Electronics
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• v.4 no.1
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• pp.39-45
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• 2004

A novel current-fed energy-recovery sustaining driver (CFERSD) for a PDP is proposed in this paper. Its main idea is to recover the energy stored in the PDP or to inject the input source energy to the PDP by using the current source built-up in the energy recovery inductor. This method provides zero-voltage-switching (ZVS) of all main power switches, the reduction of EMI, and more improved operational voltage margins with the aid of the discharge current compensation. In addition, since the current flowing through the energy recovery inductor can compensate the plasma discharge current flowing through the conducting power switches, the current stress through all main power switches can be considerably reduced. Furthermore, it features a low conduction loss and fast transient time. Operations, features and design considerations are presented and verified experimentally on a 1020${\times}$l06mm sized PDP, 50kHz-switching frequency, and sustaining voltage 140V based prototype.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.264-269
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• 1998

A proposed soft-switching buck-boost PWM converter has a lot of advantages, Viz., electric isolation, a high power factor, low switching losses, low EMI noise, reduction of the voltage and current stresses, etc. In a new PFC converter, the switching device is replaced by the loss-less snubber circuit to achieve the zero voltage switching (ZVS) at the maximum current. However, the charging current of the capacitor in the loss-less snubber circuit distorts the input current waveforms. To improve the input current waveform, a new duty factor control method is proposed in this paper.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.270-275
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• 1998

A new single phase power factor correction rectifier/regulator with dc linked energy feedback circuit is proposed, which is capable of achieving the zero voltage switching (ZVS) of a boost rectifier stage without any auxiliary switch. The performance of the proposed rectifier/regulator is demonstrated through a 200W, 90 KHz prototype. This proposed rectifier/regulator with dc linked energy feedback circuit is particularly suited for distributed power system applications

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.636-641
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• 1998

In this paper, operation characteristics of the Zero-voltage-Switching(ZVS) mode and Non-Zero-Voltage-Switching (NZVS) mode of the active clamp (ACL) forward converter are compared through the loss analysis. The losses of semiconductor devices, transformer and passive elements of the converter are analyzed and compared for each type of operation mode. In order to verify the validity of the analysis, we have built a 50W ACL forward converter and measured the losses of the converter. From the experiment it is known that the ACL forward converter shows nearly same loss distribution for both of operation modes

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1037-1038
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• 2006

CFL(Compact Fluorescent Lamp)는 기존에 사용되던 백열 램프를 바로 대치할 수 있고, 백열 전구에 비하여 광 효율이 우수하다는 장점으로 인해서 사용처가 점점 증가되고 있는 추세이다. 하지만 등기구가 가지는 공간적인 제약으로 인해서 EMI 필터와 PFC 회로를 내장할 수 없으며, 램프에서 발생한 열이 직접적으로 안정기 회로에 영향을 주어 안정기 내부 온도가 매우 높게 상승한다는 점으로 인해서 다양한 기능을 갖는 전용 ballast control IC를 사용할 수 없었다. 이러한 이유로 인해서 toroidal core를 이용한 자려식(self-excited) 동작 방법이 주로 이용되어왔다. 이러한 자려식 발진 방법은 설계하기가 까다롭기 때문에 램프 점등 전에 램프 필라멘트를 예열한 이후에 점등을 하는 rapid start 방법을 구현하기 어려웠다. 본 논문은 fairchild 반도체에서 만든 CFL 전용 ballast IC가 가지는 특성에 대해서 다루었다. IC 내부에 안정기 동작을 제어하기 위한 제어 부분과 두 개의 MOSFET를 내장하고 있어 안정기 구성에 필요한 공간을 최소화할 수 있고, 부하 상태를 검출하여 항상 Active ZVS 동작을 하도록 하는 기능을 내장하고 있어서 스위칭 손실을 최소화할 수 있다는 장점을 가지고 있다.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.551-555
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• 2004

The two-transformer full bridge (TTFB) PWM converter has two transformers which act as the output inductor as well as the main transformer, i.e. as the forward and the flyback transformer. Although the doubled leakage inductor of the TTFB makes it easier to achieve the zero-voltage switching (ZVS) of the lagging leg switch along the wide load range, it instigates a serious voltage ringing in the secondary rectifier diodes, which would require the dissipative snubber circuit, cause the serious power dissipation, and increase the voltage stress across those diodes. To overcome these problems, a, new lossless diode-clamp rectifier (LDCR) is employed as the output rectifier, which helps the voltage across rectifier diodes to be clamped on a half the output voltage $(V_o/2)$ or the output voltage $(V_o)$. Therefore, no dissipative snubber for rectifier diodes is needed and a high efficiency as well as low noise output voltage can be realized. The operations, analysis and design consideration of proposed converter are presented in this paper. To verify the validity of the proposed converter, experimental results from a 425W, 385-170Vdc prototype for the plasma display panel (PDP) sustaining power module (PSPM) are presented.

• Journal of Power Electronics
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• v.15 no.1
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• pp.86-95
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• 2015

An active clamp high step-up boost converter with a coupled inductor is proposed in this paper. In the proposed strategy, a coupled inductor is adopted to achieve a high voltage gain. The clamp circuit is included to achieve the zero-voltage-switching (ZVS) condition for both the main and clamp switches. A rectifier composed of a capacitor and a diode is added to reduce the voltage stress of the output rectifier diode. As a result, diodes with a low reverse-recovery time and forward voltage-drop can be utilized. Since the voltage stresses of the main and clamp switches are far below the output voltage, low-voltage-rated MOSFETs can be adopted to reduce conduction losses. Moreover, the reverse-recovery losses of the diodes are reduced due to the inherent leakage inductance of the coupled inductor. Therefore, high efficiency can be expected. Firstly, the derivation of the proposed converter is given and the operation analysis is described. Then, a steady-state performance analysis of the proposed converter is analyzed in detail. Finally, a 250 W prototype is built to verify the analysis. The measured maximum efficiency of the prototype is 95%.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.3
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• pp.133-139
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• 2003

In this paper, a new control scheme of Class-E inverter for Induction Heating (IH) Jar applications with clamped voltage characteristics using Pulse-Frequency-Modulation (PFM) is introduced. To reduce the voltage stress of switch, the proposed PFM control scheme doesn't need any auxiliary circuit in comparison to a family of Active Clamped Class-E (ACCE) inverter. It can decrease voltage stress of switch through modulation of switching frequency. The Class-E inverter using the proposed control scheme has the advantage of not only the same output power when it is compared with a Hybrid-Active Clamped Class-E (Hybrid-ACCE) inverter but also Zero-Voltage-Switching (ZVS), which are characteristics of conventional Class-E and ACCE inverter. The control principles and analysis of proposed method are explained in detail and its validity is verified through simulation and experimental results.