• 전력전자학회논문지
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• 제26권6호
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• pp.411-420
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• 2021

In this paper, bidirectional LLC-LC resonant DC-DC converter with notch filters in the primary side of resonant circuits is proposed. Even if resonant capacitors are used on the primary and secondary sides, the proposed converter can operate with the high gain characteristics of the LLC resonant converter without mutual coupling of resonant capacitors, regardless of the direction of power flow. In addition, by applying notch filters, the proposed converter can operate with a wider gain control range and can cope with overload and short circuit. The analysis and operating characteristics of the proposed bidirectional LLC-LC resonant converter are investigated. A 3.3 kW prototyped bidirectional LLC-LC resonant converter connected to 750 V_DC buses is designed and tested to verify the validity and applicability of this proposed converter.

• 전기학회논문지
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• 제67권3호
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• pp.398-405
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• 2018

LLC resonant converter is popular with industrial fields because it can be achieved high efficiency by zero voltage switching (ZVS). As interest grew, analysis of characteristics in LLC resonant converter have been actively studied. Generally, characteristic of LLC resonant converter is analyzed based on first harmonic approximation(FHA). The FHA analysis represents the characteristics of LLC resonant converter by obtaining the series resonant operation. FHA analysis of LLC resonant converter in load condition is correct. but it is not correct in no load condition. This paper proposed analysis of characteristics considering the parasitic components to overcome the limitation of FHA and analyze no-load characteristics. The validity of the proposed method has been investigated by simulation and experimental results.

• 전력전자학회논문지
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• 제23권3호
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• pp.161-167
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• 2018

In battery-operated systems, an isolated converter is used to interface the utility grid with the system to increase stability when charging and discharging batteries. Systems such as vehicle-to-grids (V2Gs), on-board chargers, and energy storage systems (ESSs) have recently become popular, and the roles of isolated converters have become important considerations in fabricating such devices. A fixed-frequency LLC converter, which is a type of isolated converter, presents the advantages of high efficiency and high power density by performing zero-voltage switching (ZVS) over wide frequency ranges. However, the magnetizing inductance of the LLC converter should be designed to enable ZVS in all switching devices. Therefore, in this study, the operating characteristics of the LLC circuit are analyzed, and an optimal design method for ZVS operation is established. Moreover, an 8 kW LLC high-efficiency and high-power-density resonant converter is designed and tested for ESS application. The LLC converter achieves 98% efficiency at rated power.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.511-513
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• 2008

Since conventional analysis of LLC resonant converter has a limit to explain a practical operation of LLC Resonant Converter, LLC resonant converter designed by conventional analysis can not regulate output voltage in several conditions. To solve this problem, analysis and design of LLC resonant converter including parasitic components is proposed. Experimental results are shown to confirm the feasibility of the proposed method.

• 한국인터넷방송통신학회논문지
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• 제17권1호
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• pp.129-137
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• 2017

본 논문에서는, 스위칭 손실이 적고 효율이 높은 이점을 갖고 있는 LLC 공진형 컨버터에 대하여 선형화된 수학적 모델을 정립하고 디지털 제어기 설계 과정을 제안한다. LLC 공진형 컨버터의 비선형 모델에 대하여 EDF(Extended Describing Function) 기법을 도입하여 비선형성을 선형 근사화시킨 선형 소신호 모델을 정립하고 Ziegler Nichols 방법을 이용하여 제어기 계수를 선정하였으며 연속시간 제어기를 디지털 제어기로 변환하여 적용한다. 유도된 선형 소신호 모델에 기반하여 전압 제어기를 설계하고, MATLAB 시뮬레이션을 통하여 제어기의 성능을 검증한다. 또한, 부하 변화 및 모델링 오차를 고려한 시뮬레이션을 통하여 LLC 공진형 컨버터에 대해 설계된 전압 제어기의 타당성 및 제어성능을 분석한다.

• 전력전자학회논문지
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• 제21권6호
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• pp.506-513
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• 2016

In general, LLC converters show great promise in applications that require high efficiency, especially under light load conditions. In particular, LLC converters feature wide gain capability with pulse-frequency modulation and zero voltage switching over entire load conditions. However, output voltage increases in light load conditions. In this study, Bode plot and impedance asymptotes analyses were conducted to obtain insights into the regulation characteristics of LLC converters under light load conditions. To improve the regulation characteristic of LLC converters, a new resonant tank with an additional capacitor is proposed. The design guideline for the proposed LLC converter is determined by the Bode plot and impedance asymptotes analyses. Therefore, the proposed LLC converter achieves the light load regulation while maintaining the advantages of typical LLC converters.

• 전력전자학회논문지
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• 제17권2호
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• pp.142-149
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• 2012

The independently regulated dual-output LLC resonant converter using only one power stage and one control IC is proposed in this paper. The conventional dual-output LLC resonant converter requires the extra non-isolated DC/DC converter to obtain the tightly regulated slave output voltage, which results in the low power conversion efficiency and high production costs. On the other hand, since the proposed converter controls the master and slave output voltages by pulse width modulation(PWM) and pulse frequency modulation(PFM), it can achieve tightly regulated dual output voltages without the additional non-isolated DC/DC converter. Therefore, it features a high efficiency and low cost. To confirm the validity of the proposed converter, theoretical analysis and experimental results from a 40W LED driver prototype are presented.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권8호
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• pp.423-429
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• 2006

Recently, the high frequency isolated boost DC/DC converter has been widely used for the PCS (Power Conditioning System) system because of its small size and low cost. However, the high frequency isolated boost DC/DC converters applied the conventional voltage-fed converter and current-fed converter have the problems such as the high conduction losses and the surge voltage due to the high circulating current and the leakage inductance, respectively. To overcome this problems, in this paper the secondary LLC resonant converter is proposed, and the experimental results of the secondary LLC series resonant converter for boost DC/DC converter are verified on the simulation based on the theoretical analysis and the 700W experimental prototype.

• 전기전자학회논문지
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• 제25권4호
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• pp.741-749
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• 2021

본 논문에서 제안한 전류형 LLC AC to DC 고주파 공진 컨버터는 스위치 양단에 병렬로 공진 커패시터(C₁, C₂)를 연결함으로써 ZVS(Zero Voltage Switching)동작 뿐만 아니라 2차측 Diode의 ZCS(Zero Current Switching) 동작이 가능하므로 스위칭 소자의 턴-온 및 2차측 다이오드의 턴-오프 손실을 저감시킬 수 있다. 본 논문에서 제안한 LLC AC to DC 고주파 공진 컨버터의 회로 해석은 무차원화 제어 파라메타를 도입하여 범용성 있게 기술하였다. 또한 제안한 LLC AC to DC 고주파 공진 컨버터의 운전 특성은 무파원화 제어 주파수(μ), 무차원화 저항(λ) 등의 무차원화 제어 파라메타를 이용하여 특성 평가를 수행하였다. 특성 평가를 통한 특성값을 기초한 LLC AC to DC 고주파 공진 컨버터 설계 기법의 일예를 제시하였으며, 실험 및 PSIM 시뮬레이션을 통해 이론 해석의 정당성을 입증하였다.

• 전력전자학회논문지
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• 제18권5호
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• pp.443-447
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• 2013

This paper deals with LLC resonant converter of on-board charger for electric vehicle charging. Generally, the on-board charger must have a very widely charging voltage, higher efficiency, higher power factor, lower volume and lower weight. For reducing the switching losses, voltage and current stress of the device, the on-board charger is apply the half-bridge LLC resonant converter topology. To have a wide voltage range, it is design the hardware parameters and determine the switching frequency range of the LLC resonant converter. The experimental results show a wide charge voltage.