New hybrid control technique to improve light load efficiency while meeting the hold-up time requirement for two-stage server power

Lai, Yen-Shin; Su, Zih-Jie; Chen, Wen-Shyue

doi:10.1109/ecce.2013.6647257

Cited by 9 publications

(10 citation statements)

References 20 publications

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“…In the distributed power systems and server power supplies for computing and Internet devices, the hold-up time is a special requirement, which requires output voltage regulation for certain time after AC grid dropout [1][2][3]. A typical hold-up time is the time a power supply takes to reduce from 100 to 90% of its rated output when a power outage or a supply fluctuation occurs.…”

Section: Introductionmentioning

confidence: 99%

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Family of half‐bridge LLC resonant converters with auxiliary switches for hold‐up operation

Tang

Zhao

et al. 2019

IET Power Electronics

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For applications with holdup time requirement, the magnetising inductance of the conventional LLC converter must be designed small enough to provide required peak voltage gain. However, the efficiency in normal operation will be decreased when considering the gain requirement. Here, a family of half-bridge (HB) LLC resonant converters is proposed for low-voltage and high-current applications. In order to provide the required voltage gain, auxiliary switches are introduced into parts of the secondary-side rectifiers. In the normal state, the auxiliary switches keep off and high efficiency can be achieved since the proposed converter always operates around the resonant frequency. Without considering the voltage gain requirement, softswitching is the only consideration for the design of the magnetising inductance. Therefore, circulating current and conduction losses induced by the magnetising inductance can be reduced significantly. During the holdup time, the auxiliary switches operate with pulse-width modulation (PWM) control to provide sufficient voltage gain. Furthermore, matrix transformers are engaged to simplify the winding structure and increase the output current capability. Operation principles, characteristics, and design considerations of the proposed LLC resonant converter are analysed in detail. Experimental results are given to verify the effectiveness and the advantages of the proposed converter.

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Section: Introductionmentioning

confidence: 99%

“…A typical hold-up time is the time a power supply takes to reduce from 100 to 90% of its rated output when a power outage or a supply fluctuation occurs. The hold-up time is usually specified by the manufacturer and ranges from 10 ms to dozens of milliseconds [3,4]. Fig.…”

Section: Introductionmentioning

confidence: 99%

Family of half‐bridge LLC resonant converters with auxiliary switches for hold‐up operation

Tang

Zhao

et al. 2019

IET Power Electronics

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“…The fullbridge switching converter topology is the most widely used one, for applications with medium-to-high power consumptions, in the industry. Achieving higher efficiency for load variations over different and/or wider load sub-ranges is the subject of many recent researches [9][10][11][12][13][14][15][16][17][18][19][20]. Still, improving the efficiency for wider load variations, from no-load to full-load, is important and desired for many applications, including server computer systems, electric vehicles, battery chargers and so on, and is one of the aims here.…”

Section: Introductionmentioning

confidence: 99%

General multi‐mode control method for optimising the efficiency of full bridge converter based on prominent control modes and transition points calculation

Ghanbari¹,

Raie²

2019

IET Power Electronics

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The theme of this article is to propose a general multi-mode control method to optimise the efficiency of the full-bridge converter based on prominent control modes for the whole range of load variations. This method selects the most efficient prominent control mode in each load sub-range, including variable delay phase shift, fixed delay phase shift, pulse width modulation (PWM) and burst control while the load current varies in its entire range from full down to no load. In this regard, for the first time, three transition points between control modes are analytically determined based on full-bridge converter power losses analysis. Determining transition points and load current sub-ranges, being functions of converter parameters, is in fact the process of optimising the proposed method for the entire range of the load current in terms of four control modes. The accuracy of the analytically determined transition points and the optimal control mode selection over the load variations are justified by experimental results on digitally implemented proposed control method and full-bridge converter.

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“…Furthermore, this kind of DC-DC converter can be effectively improved and designed. Small signal model can be the transfer functions of duty cycle to filter current, filter current to output voltage, duty cycle to output voltage, and input voltage to output voltage respectively [ 9 – 10 ]. All the transfer functions are formulated according to respective small signal equivalent circuit which decides characteristics of DC operating points and their neighborhood operating points.…”

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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New hybrid control technique to improve light load efficiency while meeting the hold-up time requirement for two-stage server power

Cited by 9 publications

References 20 publications

Family of half‐bridge LLC resonant converters with auxiliary switches for hold‐up operation

Family of half‐bridge LLC resonant converters with auxiliary switches for hold‐up operation

General multi‐mode control method for optimising the efficiency of full bridge converter based on prominent control modes and transition points calculation

An improved large signal model of full-bridge LLC converter

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