Analysis on Synchronous Rectifier Control to Improve Regulation Capability of High-Frequency <i>LLC </i> Resonant Converter

Summary As for the traditional LLC converter, there is a problem in efficiency at light load. In order to keep the output voltage of this converter constant at a given value at light load, the switching frequency will be increased, and hence, the efficiency would be degraded. Consequently, based on the inherent frequency modulation and from the point of view of blanking time tuning, the efficiency at light load will be further improved due to circular current reduction, and at the same time, the efficiencies under other operating conditions are also enhanced. In this paper, the strategy for automatically adjusting the blanking time is described and analyzed. Afterwards, the digital signal processor (DSP) is used as a circuit control kernel, and an experimental setup, with input voltage of 400 ± 10 V, rated output voltage of 12 V, and rated output current of 20 A, is provided to demonstrate the effectiveness of the proposed strategy.

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“…According to (16), (17), and Figure 7, in order to make the switch have ZVS turn-on, the blanking time needs to satisfy the following equation:…”

Section: Deduction Of Minimum Blanking Timementioning

confidence: 99%

“…The literature proposes a synchronous rectifier (SR) control strategy to enhance the light‐load regulation capability by the extended SR turn‐on time. By doing so, the negative current can flow through the SR, so the light‐load regulation can be realized.…”

Section: Introductionmentioning

confidence: 99%

Efficiency improvement for LLC converter based on automatic tuning of blanking time

Hwu

Guo

2019

Circuit Theory & Apps

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“…In addition, realistic ramp variation in resonant frequency is also reflected in the model. In [ 15 ], synchronous rectifier turn-on time is extended to improve control capability under light load condition. Investigated model cannot live without equivalent circuit which is made fully use of so that proposed Fourier series analysis can be developed.…”

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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“…Although SiC MOSFET already has good efficiency performance, to further reduce switching losses, several switching techniques have been proposed to achieve soft switching in the DC-DC converter [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. In these techniques, the semiconductor devices turn ON or OFF when the voltage is zero, presenting zero voltage switching (ZVS), or when the current is zero, presenting zero current switching (ZCS) [11][12][13].…”

mentioning

confidence: 99%

“…However, the parasitic capacitance will be larger and it results in complex designs of the resonant tank and a severe regulation problem of the LLC DC-DC converter. Thus, a new digital synchronous rectification (DSR) strategy is defined in Reference [25], which controls the SR switches by digital logic without any additional component. The new strategy achieves the output voltage regulation and high efficiency in the light-load condition.…”

mentioning

confidence: 99%

Research on Digital Synchronous Rectification for a High-Efficiency DC-DC Converter in an Auxiliary Power Supply System of Magnetic Levitation

Zhao

2019

Energies

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In this paper, a new auxiliary power supply system of magnetic levitation based on the LLC DC-DC converter is proposed. The switches of the DC-DC converter are SiC MOSFET, which enables high frequency, high temperature, and high power density. For further improving the efficiency of the system and realizing the stability of the output voltage under different load conditions, the digital synchronous rectification (DSR) based on the phase shift control strategy is proposed. The prototype of the LLC DC-DC converter based on SiC MOSFET is implemented, which can realize zero voltage switching (ZVS) and zero current switching (ZCS). Then, the thermal image of DSR is presented, which proves that the power loss of SiC MOSFET with DSR is relatively low. Additionally, the system efficiency among the Si IGBT, SiC MOSFET, and SiC MOSFET with DSR is analyzed and the prototype demonstrates 98% peak efficiency. Finally, simulations, experiments, and data analysis prove the superiority of the proposed DSR strategy for the new auxiliary power supply system of magnetic levitation.

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Analysis on Synchronous Rectifier Control to Improve Regulation Capability of High-Frequency LLC Resonant Converter

Cited by 37 publications

References 28 publications

Efficiency improvement for LLC converter based on automatic tuning of blanking time

Efficiency improvement for LLC converter based on automatic tuning of blanking time

An improved large signal model of full-bridge LLC converter

Research on Digital Synchronous Rectification for a High-Efficiency DC-DC Converter in an Auxiliary Power Supply System of Magnetic Levitation

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