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Evaluation of Frequency-Dependent On-Resistance of GaN Devices at High Frequency
Kangping Wang,Bingyang Li,Zhiyuan Qi,Laili Wang,Xu Yang,Aici Qiu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
The switching frequency of GaN-based power converters has been pushed to several MHz and even higher. At such high frequencies, this paper finds that the onresistance of GaN devices may be much higher than their DC values, especially for the devices with low on-resistance. The frequency-dependent characteristics of on-resistance are studied through electrical and thermal experiments for the first time in this paper. A simplified finite-element-simulation model is proposed to illustrate the mechanism of the frequency-dependent characteristics. The results show that the frequency-dependent characteristics of the on-resistance are closely related to the current distribution inside the GaN device and affected by the layout. In addition, two same GaNbased 10MHz DC-DC converters were designed to operate under the same conditions, and the only difference comes from the layout of GaN devices. The experimental results show that the efficiency of the converter with optimized layout is improved by 2% compared to that with conventional layout.
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Binyu Wang,Jianpeng Wang,Dingkun Ma,Laili Wang,Fengtao Yang,Xinying Li,Youbo Tan 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Due to a series of advantages compared with other existing power converters, modular multilevel converters (MMCs) have been widely used in the last decade. However, in some applications, such as the offshore wind power transmission, the MMC submodules (SMs) are subjected to harsh operating environment and adverse mission profiles which can easily lead to failures in the solder layers of IGBT modules. Therefore, the lifetime estimation is very important to predict the reliability of MMC. This paper studies the fundamental-frequency thermal cycles and proposes a lifetime estimation method of MMC SMs based on the combination of finite element analysis (FEA) and the physical lifetime model. This method provides a deeper physical description of the failure mechanism and considers the thermal coupling among the chips, which make the lifetime calculation more accurate. The simulation time of FE in this research is acceptable. The distribution of lifetime is presented in the form of a colorful cloud map, rather than a single number, from which we can know the most vulnerable part of the solder layers. This can help us find the appropriate measures to improve the reliability of MMC SMs. In this paper, the principle and reliability issues of MMC are first analyzed. Second, the loss of the SM is calculated through simulation and curve fitting. Then, a 3D finite element (FE) model of MMC SM is developed and the FE simulation is performed. Finally, the lifetime of the SM is obtained based on the FEA results and Morrow lifetime model.
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Analysis and Design of LLC Resonant Converters Operating in Reverse Mode
Angyang Zhou,Xu Yang,Mofan Tian,Naizeng Wang,Laili Wang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In this paper, the reverse operating characteristics of LLC resonant converters from fr/2 to fr are explored. The reverse voltage-gain and the conditions for zero-voltage switching (ZVS) of the reverse LLC resonant converter are summarized, and the frequency interval is obtained according to the magnitude of the turn-off current. The accuracy of the above analysis is verified by experiments. The research on the reverse operating characteristics of LLC resonant converters has practical significance in some special applications especially when require for the bidirectional operation.
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Yang Chen,Yaqi Sun,Mofan Tian,Laili Wang,Haoyuan Jin 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Dielectric elastomer (DE) is a kind of capacitive material that widely used in soft robots’ applications as actuators. To obtain notable deformation, the drive voltage is typically up to several thousand volts and the charging charges must be removed to make it recover. In this paper, a high step-up capacitive load bi-directional flyback converter with active clamp technique is proposed. For the charging process, the effects of increasing high output voltage and parasitic elements in the circuit on the operation of the active clamp circuit are discussed in detail. Wide bandgap devices are used at the secondary side to reduce the parasitic capacitance. The proposed lossless active clamp circuit can absorb the energy in leakage inductance of transformer and achieve zero-voltage-switching (ZVS) over most of the charging process. Besides, the EMI problem caused by leakage inductance of conventional flyback converter is also solved. A prototype with 12V input and 1000V output has been fabricated and compared with a quasi-resonance flyback (QR flyback) at the same working condition. The tested results verify the good performance of the proposed ACF converter.
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Zhaoshan Wu,Liya Zhou,Xuemei Ding,Xiongying Wu,Laili Wang 한국의류학회 2022 Fashion and Textiles Vol.9 No.1
Practices in the textile and apparel industry (TAI) have led to numerous environmental and social problems, which have prompted extensive research on the sustainable development of the textile and apparel industry (SDTAI). This paper presents a comprehensive and quantitative analysis of the status quo in the SDTAI domain using scientometrics. From 1987 to 2019, the Web of Science core collection databases (SCI and SSCI) included 863 journal articles related to SDTAI, and our analysis results were as follows: (1) 60 critical research keywords occur in the knowledge base; (2) four research hotspots were identifed; (3) fve themes constituted the main knowledge area; and (4) based on the knowledge base, research hotspot, and knowledge domain, the knowledge structure consisted of nine subjects and fve systems. This paper proposes a knowledge roadmap that can be helpful for practitioners and academicians to better understand the current sustainable development status and trends in the TAI.
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A Novel Synchronization Technique for High Frequency Rectifier in Wireless Power Transfer
Yongbin Jiang,Min Wu,Zexian Zeng,Yonghui Liu,Xiufang Hu,Laili Wang,Yue Wang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper presents a novel synchronization technique for high frequency rectifier in wireless power transfer (WPT). To overcome the drawbacks of traditional phase-locked method based on DSP controller in high frequency rectifier, a novel phase-locked loop combined with the chained trigger mode (PLL-CTM) is proposed. The reasons why the driver pulses lose have been disclosed in detail. Then, the problem of pulse losing can be solved based on PLL-CTM. Finally, a 500W WPT prototype is built to verify the validity of the proposed synchronization technique.
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