• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.2
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• pp.165-173
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• 2022

The electrification trend of mobility increases every year due to the development of power semiconductor and battery technology. Accordingly, the development and distribution of fast chargers for electric vehicles (EVs) are in demand. In this study, we propose a design and implementation method of an LLC converter for fast chargers. Two 15 kW LLC converters are configured in parallel to have 30 kW rated output power, and the control algorithm and driving sequence are designed accordingly and verified. In addition, the improved power conversion efficiency is confirmed through zero-voltage switching (ZVS) of the LLC converter and reduction of turn-off loss through snubber capacitors. The implemented 30 kW LLC converters show a wide output voltage range of 200-950 V. Experiments applying various load conditions verify the converter performance.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.397-398
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• 2016

This paper analyzes switching losses, efficiency and temperature depending on Si and SiC devices applied in two stage AC-DC converter. To evaluate the charge and discharge performance and stability of the battery pack, there is a need for a battery pack testing system. To do battery charge and discharge experiment used in battery pack test, A topology, two stage AC-DC converter, has been built. SiC devices more decrease switching losses than that of Si. Also, cooling system was applied in Si and SiC devices. When using SiC devices, it can be confirmed that the size of heat sink is reduced for small loss.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.385-387
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• 1996

A novel two stage soft-switching ac-to-dc convener with power factor correction is proposed. The proposed convener provides zero-voltage-switching (ZVS) condition to main switch of boost pre-regulator without auxiliary switch. Comparing to the conventional two stage approach(ZVS-PWM boost rectifier followed by off-line ZVS dc-dc step down converter), the proposed approach is simple and reducing EMI noise problem. A new simple DC-linked energy feedback circuit provides zero-voltage-switching condition to boost pre-regulator without imposing additional voltage and current stresses and loss of PWM capability. Operational principle, analysis, control of the proposed converter together with the simulation results of 1KW prototype are presented.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1136-1141
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• 1992

This paper proposes a control technique to obtain high frequency quasi sinusoidal DC-Link waveform permitting zero-voltage-switching(ZVS). This operation results in reduction of commutation stress and switching losses in the power devices because they cause no switching loss in principle. But in existing control methods, the resonant capacitor voltage is not frequently made of zero-cross oscillation. We propose an optimum control stratege which can sustain oscillation and keep the capacitor voltage at an allowable level. Some experimental results are included to confirm the validity of the analytical results.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.529-531
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• 2008

Generation system using regenerative energy like photovoltaic, fuelcell is increased, PCS technology coming into the spotlight. The efficiency of DC-DC converter as part of the PCS is very important, multi-phase boost converter has more advantage than other topology. Input current of the multi-phase boost converter is divided into two inductor current because of parallel structure of the boost converters, thus it has features of decreasing input current ripple and output voltage ripple. Also multi-phase boost converter with soft switching can decrease switching loss using ZCS and ZVS. In this paper, simulation and experiment are performed to verify operation of the proposed converter, and efficiencies of the conventional and proposed converter are compared.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.544-546
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• 2008

An improved dual-path energy recovery circuit (ERC) using a current source and a voltage source for plasma display panel (PDP) is proposed. The proposed ERC uses the voltage source to charge a panel and the current source to discharge the panel. Thus, the proposed circuit can make the panel charge to $V_S$ and discharge to 0V, fully and it is possible to achieve zero voltage switching (ZVS) of all switches in H-bridge inverter and zero current switching (ZCS) of all switches in the ERC. Moreover, it has less conduction and switching loss in ERC devices by the dual energy recovery paths for charging and discharging the panel. Furthermore, it has features of canceling the gas discharge current, high performance and the low cost ERC components. The operation principle and features of the proposed ERC are presented in detail and verified with 42-inch SD PDP.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.579-583
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• 2003

Hysteresis controllers are intrinsically robust to system parameters, exhibit very high dynamic response and are suitable for simple implementation. But the current control using a conventional hysteresis controller has the disadvantage that high switching frequency may happen due to lack of coordination among individual hysteresis controllers of three phases. This will of course increase the switching loss. In addition, the current error is not strictly limited. So, in this paper to reduce the switching frequency, a double band hysteresis current controller is proposed. The presented control system was tested with digital simulation in the Borland C++ program and demonstrate the advantage of proposed hysteresis current controller.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1954-1956
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• 1998

The three-level voltage source inverter (VSI) is good topology for high voltage and high power applications where no semiconductor devices are available. However, it has an inherent problem of switching loss and midpoint charge balance. Therefore, this paper presents two ways. The one is to adopt ZCT soft-switching method to the conventional three-level VSI. The another is to be proposed the method of the midpoint charge balance in three-level VSI. To prove the proposed topology, the paper presents a comprehensive evaluation with theoretical analysis, simulation and experimental results.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1911-1913
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• 1998

This paper has described about a SEPP Inverter for induction heating load. It is analyzed theoretically about the Inverter operation for induction heating. According to the parameters of induction heating load, it is proposed a method of circuit analysis and operation characteristics of the Inverter. In addition, the soft switching technology known as ZVS(Zero Voltage Switching) is used to reduce turn on and off loss at switching. The Proposed inverter shows it can be practically used as power source system for high frequency induction heating appliancs.

• Transactions on Electrical and Electronic Materials
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• v.15 no.1
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• pp.1-6
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• 2014

Self-exciting electronic ballast, of small size, and low cost, and high power, with no stroboscopic effect, no noise, is widely used in the general lighting market. This paper describes the cause of high switching loss of self-exciting electronic ballast, based on its operational principle; then, to reduce the switch temperature and increase the reliability of the product, the drive circuit has been improved, to achieve soft-switching. The theory analysis, simulation and experimental result prove the feasibility and compatibility of this new method in practice. Finally, the design procedure and winding method of the self-exciting current transformer are introduced.