A Modified Gain Model and the Corresponding Design Method for an LLC Resonant Converter

Liu, Jianqiang; Zhang, Jiepin; Zheng, Trillion Q.; Yang, Jingxi

doi:10.1109/tpel.2016.2623418

Cited by 92 publications

(40 citation statements)

References 19 publications

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“…Energies 2019, 12, x FOR PEER REVIEW 2 of 17 analysis methods based on time-domain solution [16,17]. However, if the output capacitance or other parasitic components are considered, the order of the circuit will be higher, and it is difficult to get the time domain solution.…”

Section: Equivalent Circuit Of Llc Resonant Converter With Parasitic mentioning

confidence: 99%

“…Besides the fundamental harmonic approximation method, the graphical state-trajectory analysis method is clear and useful to analyze the resonant converters [15]. There are also some analysis methods based on time-domain solution [16,17]. However, if the output capacitance or other parasitic 2 of 16 components are considered, the order of the circuit will be higher, and it is difficult to get the time domain solution.…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Parasitic Components on LLC Resonant Converter

Hao

Lei

et al. 2019

Energies

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In recent years, the LLC resonant converter has been widely used in DC–DC conversion applications. However, the parasitic components of the LLC resonant converter have a significant impact in practical applications, such as influence on the conduction loss and the soft-switching of power devices, the voltage oscillation across rectifier diodes, the unregulated output voltage at light load condition and so on. It is hard to analyze the higher-order circuits by the conventional analysis methods. Focusing on the operational principle of the LLC converter with parasitic components, the differential equation model is presented and solved by the numerical method in this paper. The simulation results verify the correctness of the theoretical analysis. The causes of two different frequency oscillations and the voltage spike are clarified. The design considerations and a specific example of the LLC converter are given. The experimental results are consistent with the simulation results, and the soft-switching of primary-side switches can be achieved in the prototype.

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Section: Equivalent Circuit Of Llc Resonant Converter With Parasitic mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Influence of Parasitic Components on LLC Resonant Converter

Hao

Lei

et al. 2019

Energies

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“…Using Equations (17), (21) and (22), the maximum value for the inductance ratio of the auxiliary circuit to ensure complete ZVS for a given can be calculated as follows:…”

Section: Auxiliary Circuit Analysis and Designmentioning

confidence: 99%

“…First harmonic approximation (FHA) is an analytical method to estimate the voltage gain in resonant converters [19]. There are modifications of the FHA method in the literature, to account for higher harmonics [20,21]. However, these methods do not consider load-dependent behavior.…”

Section: Introductionmentioning

confidence: 99%

ZVS Auxiliary Circuit for a 10 kW Unregulated LLC Full-Bridge Operating at Resonant Frequency for Aircraft Application

et al. 2019

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In modern aircraft designs, following the More Electrical Aircraft (MEA) philosophy, there is a growing need for new high-power converters. In this context, innovative solutions to provide high efficiency and power density are required. This paper proposes an unregulated LLC full-bridge operating at resonant frequency to obtain a constant gain at all loads. The first harmonic approximation (FHA) model is not accurate enough to estimate the voltage gain in converters with high parasitic resistance. A modified FHA model is proposed for voltage gain analysis, and time-based models are used to calculate the instantaneous current required for the ZVS transition analysis. A method using charge instead of current is proposed and used for this ZVS analysis. Using this method, an auxiliary circuit is proposed to achieve complete ZVS within the whole load range, avoiding a gapped transformer design and increasing the efficiency and power density. A 28 Vdc output voltage prototype, with 10 kW peak output power, has been developed to validate the theoretical analysis and the proposed auxiliary circuit. The maximum efficiency (96.3%) is achieved at the nominal power of 5 kW.

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“…However, Definition of quality factor still comes from the FHA. In [ 25 ], denominator of voltage gain is divided into resonant factor and load factor. They are related to the inductance ratio and quality factor respectively.…”

Section: Introductionmentioning

confidence: 99%

An improved large signal model of full-bridge LLC converter

Yao

Liu

2018

PLoS ONE

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For the full-bridge LLC converter, it is necessary to establish a large signal model with low-complexity and high-precision when the current of filter inductor works under the continuous conduction mode (CCM) situation. In terms of low complexity, peak values of resonant state variables and average values of slow state variables are taken as the measured indexes between models and actual converter. Models based on the first harmonic approximation (FHA) are studied in depth because they have lower complexity than the existing models. From prospective of high precision, deficiencies of typical FHA model are explained in the light of harmonic generation mechanism of primary current and influence of Fourier series on the typical equivalent circuit. Therefore, transient process of each metallic oxide semiconductor field effect transistor (MOSFET) and its related fast recovery diode, transient process of Schottky rectifier diodes, piecewise equivalent circuit, appropriate selection of variables, and simplified modified dynamic equations are all considered. Furthermore, the unified proposed model is achieved according to the equivalent principle of indexes between aforementioned improved analyses and proposed model. Numerical results of typical FHA model and proposed model are given in accordance with the key indexes. Then, corresponding experimental results are also presented. Differences of indexes between the two models and the actual converter are compared respectively. Though complexity of proposed model is the same as that of typical FHA model, precision of proposed model is higher than that of typical FHA model.

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A Modified Gain Model and the Corresponding Design Method for an LLC Resonant Converter

Cited by 92 publications

References 19 publications

The Influence of Parasitic Components on LLC Resonant Converter

The Influence of Parasitic Components on LLC Resonant Converter

ZVS Auxiliary Circuit for a 10 kW Unregulated LLC Full-Bridge Operating at Resonant Frequency for Aircraft Application

An improved large signal model of full-bridge LLC converter

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