• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.777-780
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• 2003

In this paper, an improved full wave mode ZVT-PWM DC-DC Converter is presented to maximize the regeneration ratio of resonant energy by only putting an additional diode in series with auxiliary switch. The operation of auxiliary switch in a half wave mode makes possible the soft switching condition of all switches. Furthermore, the increase of the regeneration ratio to resonant energy results in low conduction losses and minimum voltage and current stresses. The operation principles of the proposed converters are analyzed using the PWM boost converter topology as an example. Theoretically analysis and experimental results verify the validity of the boost converter topology with the proposed full wave mode ZVT-PWM converters

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.210-213
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• 1991

The clamp mode Zero-Volatge-Switched Multi-Resonant-Converter(ZVS-MRC) is proposed. In the converter, the performance of the conventional ZVS-MRC is improved by clamping the drain-to-source voltage of the power switch using a soft switching nondissipative active clamp network. The analysis for each stage of the converter operation modes is presented and is verified by experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.188-194
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• 2020

This paper presents a high-efficiency Switch Mode Line Transformer (SMLT) composed of load-shared dual modules, which is based on the AC/AC LLC resonant converter. Given that the conventional adaptor is usually composed of two power stages, namely, the PFC and DC/DC converters, its system size can be increased according to the output power. However, given that the proposed SMLT can separate the PFC converter from the adaptor, the size reduction of the system can be achieved. Meanwhile, the SMLT with a single module has the limit of the size reduction because of a high resonant current. Thus, it can be configured with dual or multiple modules to reduce the resonant current. Then, their load sharing can be guaranteed by only the proposed transformer structure without an extra current controller. The validity of the proposed converter is proven through a 850-W prototype.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.327-332
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• 1999

In this paper, six harmonic injection PWM method for reducing total harmonic distortion in single switch three phase discontinuous conduction mode boost converter is presented. In the proposed method, periodic six harmonic voltage is injected in the control circuit to vary the duty ratio of the converter switch within a line cycle so that the fifth order harmonic of the input current is reduced. Experimental results are verified by converter operating at 400V/6kW with three phase 140V~220V input.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.221-223
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• 1997

This paper deals with the slip power recovery system using switch mode converter in the inverter DC side, which recovers slip power of induction machine to AC line with the aid of the boost converter. As a results, the motor speed can be controlled by the duty ratio of boost switch, not by inverter firing angle. This results that the reactive power produced by phase controlled inverter and diode rectifier can be greatly reduced and linear speed regulation can be obtained. Moreover, the harmonic components of line current caused by the commutation in inverter and rectifier can be considerably suppressed. Therefore, most of the problems in conventional system can be solved.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.2
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• pp.243-250
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• 2005

A new technique for improving the efficiency of single-Phase high-frequency switch-mode boost rectifiers is proposed. This rectifier includes an additional boost converter that parallels the main high-frequency switching device. The additional converter. which is controlled at lower frequencies. bypasses most of the current in the main switch and the high frequency switching loss is greatly reduced accordingly. The rectifier works cooperatively in high efficiency and as if it were a conventional rectifier with one switching device. The proposed scheme is verified by computer simulation using software PSIM.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1533-1546
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• 2015

This study presents a novel method for reducing the switching losses of an asymmetric half-bridge converter for a three-phase, 12/8 switched reluctance motor operated in low speed. In particular, this study aims to reduce the switching-off losses of chopping switches in the converter when operated in the current regulated mode (chopping mode). The proposed method uses the mixed parallel operation of IGBT (chopping switch) and MOSFET (auxiliary switch). MOSFET is precisely controlled to momentarily conduct prior to the turn-off interval of the IGBT. Consequently, the voltage across the switches is clamped to approximately zero, substantially decreasing the turn-off switching losses. The analytical expressions of power losses are extensively elaborated. Compared with the conventional asymmetric half-bridge converter, the modified converter can effectively minimize the switching losses. Therefore, the efficiency of the converter is eventually improved. Computer simulation and experimental results confirm the effectiveness of the proposed technique.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.95-98
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• 2003

A ZVT PWM Boost Converter is proposed to reduce current stresses and conduction losses of main switch in a conventional circuit. By attaching resonant inductor Lr1 in parallel with capacitor Cr, the resonant circulating current is diverted to the additional component and then the main switch is subjected to minimum current stresses same as those in their PWM counterparts. Moreover, the operation of the auxiliary switch in a half wave mode to prevent reverse resonant energy from freewheeling can be able to lessen the conduction losses. The operation principles of the proposed converters are analyzed using the PWM boost converter topology as an example. Theoretically analysis and experimental results verify the validity of the boost converter topology with the proposed circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.4
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• pp.237-243
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• 2019

A high-efficiency and small-sized switched-mode line transformer (SMLT) is proposed in this study. The conventional structure of an adapter is composed of line transformer and rectifiers. This structure has a limit in miniaturizing due to low-frequency line transformer. Another structure is composed of power factor correction (PFC) and DC/DC converter. This structure has a limit in reducing volume due to two-stage structure. As the proposed SMLT is composed of an LLC resonant converter, a high-frequency transformer can be adopted to achieve isolation standards and size reduction. This proposed structure has different operation modes in accordance with line input voltage to overcome poor line regulation. In addition, the proposed SMLT is applied to the front of a conventional PFC converter, because the SMLT output voltage is restored to rectified sinusoidal wave by using a full-bridge rectifier in the secondary side. The design of the PFC converter is easy, because the SMLT output voltage is controlled as rectified sinusoidal wave. The validity of the proposed converter is proven through a 350 W prototype.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.200-203
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• 2002

This paper presents Continuous-current mode of $S^4$-PFC(Single-Stage Single-switch Power Factor Correction) converter. Proposed converter operates in the continueous current mode(CCM) at full load and discontinuous current mode(DCM) at light load. So, characteristic of proposed converter is no bus voltage stress and Zero Voltage Switching(ZVS) using resonant auxiliary circuit. And. This paper presents characteristic of $S^4$-PFC converter and effect of circuit parameter of proposed converter through the input inductor, PFC capacitor's variation. All of these theory and characteristic verified through the experiment with a 72W(12V, 6A), $90^{kHz}$ prototype converter.