A Control Strategy and Design Method for Interleaved LLC Converters Operating at Variable Switching Frequency

Hu, Zhiyuan; Qiu, Yue; Liu, Yanfei; Sen, P.C.

doi:10.1109/tpel.2014.2300165

Cited by 143 publications

(31 citation statements)

References 35 publications

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“…By employing the switch controlled capacitor (SCC), the equivalent resonant capacitor value can be controlled so to compensate the component tolerances, and thus the voltage gain difference [8], [9]. Besides, the switches always achieve ZVS, which maintains the attractiveness at high frequency applications.…”

Section: B Interleavingmentioning

confidence: 99%

Latest Advances of LLC Converters in High Current, Fast Dynamic Response, and Wide Voltage Range Applications

Chen¹,

Liu²

2017

CPSS TPEA

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Abstract-LLC converter has been the simplest topology since long to achieve soft switching and overall the highest performance within small form factor at converter level. This paper discusses the latest advances of LLC converter from the perspective of topology and control. The technology ranges from high current, fast dynamic response to wide operational voltage range. The application mainly falls in the scope of server and data center, and may also cover telecom, PV, battery charging, etc.Index Terms-LLC, review, survey, current sharing, multiphase, interleave, phase shedding, passive impedance match, SR drive, fast dynamic, current mode control, current sensing, wide voltage range, hold up, high voltage gain.

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Section: B Interleavingmentioning

confidence: 99%

Latest Advances of LLC Converters in High Current, Fast Dynamic Response, and Wide Voltage Range Applications

Chen¹,

Liu²

2017

CPSS TPEA

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“…Conditions k < 0 and k > 1 does not exist because this means one phase absorbs the power. Accordingly, the load current sharing error σ load is defined in (9); and the resonant current sharing error σ Resonant is defined in (10). If a>1 or b>1, it means phase #2 has lower resonant frequency compared with phase #1.…”

Section: Load Sharing Characteristic Of Common Indctor Multi-phasmentioning

confidence: 99%

“…A category of active methods adjust the equivalent resonant capacitor [9], [10] or inductor [11] to compensate the resonant tank components' tolerances using additional MOSFETs. The circuit diagram for switched capacitor is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

A common capacitor multi-phase LLC resonant converter

Wang

Chen

et al. 2016

2016 IEEE Applied Power Electronics Conference and Exposition (APEC)

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In this paper, a new common capacitor current sharing method is proposed for multi-phase LLC resonant converter. Automatic current sharing is achieved by using a common resonant capacitor for all the LLC resonant stages, by connecting the resonant capacitors in each phase in parallel. The proposed method can automatically share the load current without any additional circuits and control strategy. The current sharing performance of the proposed common capacitor current sharing method is analyzed under Fundamental Harmonic Analysis (FHA) assumption. A 600W two-phase LLC converter prototype based on the proposed method is built to verify the feasibility. Excellent current sharing performance (6.5% current sharing error at a wide load range) has been achieved.

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“…Among them, the LLC resonant converter is the most attractive topology due to its excellent soft-switching performance and voltage step-up capability [3]- [6]. Fig.…”

Section: Introductionmentioning

confidence: 99%

“…However, as for the hold-up time requirement, the parameters of the LLC converter has to be designed according to the minimal input voltage resulting in bulky magnetizing components and low efficiency of the normal operation point due to large circulating current of the magnetizing inductance. Many design methods have been presented to optimize the efficiency and extend the operating range of the LLC resonant converter [6]- [8]. Unfortunately, to satisfy the voltage step-up ratio during the hold-up time，the magnetizing inductance of the LLC resonant converter has to be decreased leading to increased circulating current within the entire operation range, which will affect the efficiency of the normal operation.…”

Section: Introductionmentioning

confidence: 99%

A Secondary-Side Phase-Shift-Controlled <italic>LLC</italic> Resonant Converter With Reduced Conduction Loss at Normal Operation for Hold-Up Time Compensation Application

Gao

et al. 2015

IEEE Trans. Power Electron.

130

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A novel secondary-side phase-shift-controlled (SS-PSC) LLC resonant converter is proposed for applications requiring hold-up time operation such as distributed power systems and server power supplies. High efficiency at the normal input voltage is achieved because the proposed SS-PSC LLC converter always operates at the series-resonant frequency of the resonant tank. What's more, the magnetizing inductor of the proposed converter doesn't need to be reduced to provide desired voltage boost ratio for the hold-up time operation, which results in reduced conduction losses and improved efficiency. Sufficient voltage boost ratio for the hold-up time operation is provided by using secondary-side phase-shift control strategy. In comparison with the conventional variable-frequency-controlled LLC resonant converter, the main advantages are that the circulating current caused by the magnetizing inductor is effectively suppressed and the efficiency of normal operation is significantly improved. The operation principles, output characteristics and design considerations of the proposed converter are presented in detail. Experimental results are given to verify the effectiveness and the advantages of the proposed solutions.

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A Control Strategy and Design Method for Interleaved LLC Converters Operating at Variable Switching Frequency

Cited by 143 publications

References 35 publications

Latest Advances of LLC Converters in High Current, Fast Dynamic Response, and Wide Voltage Range Applications

Latest Advances of LLC Converters in High Current, Fast Dynamic Response, and Wide Voltage Range Applications

A common capacitor multi-phase LLC resonant converter

A Secondary-Side Phase-Shift-Controlled <italic>LLC</italic> Resonant Converter With Reduced Conduction Loss at Normal Operation for Hold-Up Time Compensation Application

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