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RISS 인기검색어
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- 저자 : Kexu Sun (검색결과 3 건)
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A Power-compensated and Dimmable AC Direct LED Driver with High Efficiency
Donglie Gu,Shengpeng Tang,Kexu Sun,Jianxiong Xi,Lenian He 대한전자공학회 2017 Journal of semiconductor technology and science Vol.17 No.6
A dimmable and power-compensated AC direct LED driver for lighting application is presented. A Source-Coupled Pair (SCP) is adopted to realize the soft self-commutating. To maximize the power efficiency, a multi-dimensional optimization method is applied for finding the optimum number of LEDs in each string. Moreover, error analysis for efficiency is introduced to evaluate the impact of circuit mismatches on efficiency. The driver includes a Power Compensation module which enables the LEDs power approximately constant under various AC line voltages. In addition, a low frequency pulse-width modulation (LFPWM) dimming technique is designed to regulate the LED’s brightness. The LED driver IC is designed and implemented in CSMC 700 V 1 um BCD process. The post-layout simulation results show that the system can achieve a high efficiency of 90.2% under typical condition and 220 V|rms, meanwhile realize dimming with a 90% duty cycle, 10 kHz dimming signal. With the proposed compensation scheme, the output power only changes less than 5% under 20% variation in input voltage.
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Shengpeng Tang,Donglie Gu,Xianzhi Meng,Kexu Sun,Jianxiong Xi,Lenian He 대한전자공학회 2017 Journal of semiconductor technology and science Vol.17 No.6
A 3 MHz Si/ 5 MHz GaN-based 48 W boost converter with high speed and high accuracy Peak Current Control Unit (PCCU) is presented. Compared with the conventional Peak Current Mode (PCM) controllers, the boost controller IC adopts a novel PCCU consisting of a fully differential open-loop operational transconductance amplifier (OTA) and a transimpedance amplifier (TIA), which can minimize the feedforward delay and enable the converter to operate at a higher switching frequency. As a result, the dynamic response and peak current accuracy of the converter are improved. In addition, the compensated output of error amplifier in PCCU is moved forward to raise the control accuracy further. This IC is designed in CSMC 0.8 um 60 V BCD process. The post-layout simulation shows that the boost converter with the proposed PCCU can shorten the feedforward delay to 28.01 ns and behave much better than the conventional one in dynamic response as well as peak current accuracy. The proposed converter can operate at 3/5 MHz well with wide duty cycle ranging from 0.167 to 0.750. The maximum line regulation and output regulation is less than 9.6 mV/V and 6.72 mV/V, respectively.
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Ke Xu,Xiaosheng Yang,Dagao Sun,Xin Yang,Yumei Zhou,Wei Li,Qindan Yang,Xianjiong Yang,Rong Li,Jian Feng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2020 NANO Vol.15 No.02
LaFeO3/NiO modified g-C3N4 nanosheets (L-N/CNS) were synthesized by a two-step method. HRTEM results showed that an intimate contact between LaFeO3, NiO and N-CNS was successfully established. Ninety percent of phenol was degraded within 120 min, and the hydrogen evolution rate of 171.2 μmol h -1 g -1 was obtained over the L-N/CNS heterojunctions under the visible-light irradiation. It was higher than that of g-C3N4 nanosheets, NiO modified g-C3N4 and LaFeO3/g-C3N4. The ·O2 - radicals acted the crucial role in the photocatalytic degradation reaction. EIS, PL and time-resolved fluorescence spectra demonstrated that L-N/CNS possessed the highest charge separation efficiency. The intimate contact between LaFeO3, NiO and g-C3N4 nanosheets promoted the separation and transfer of photo-induced electron–hole pairs and consequently prolonged the exciton lifetime, and implied more photo-induced electrons could be probably involved in the photocatalytic reactions on the surface of photocatalysts. Thus, the visible-light driven photocatalytic performances of L-N/CNS were effective. This work provided a feasible method to design and construct heterostructures for the exploitation of solar energy.
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