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RISS 인기검색어
- 검색키워드
- 저자 : He Xueru (검색결과 3 건)
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Efficiency optimization of variable‑frequency controlled power factor correction converters
Yufei Zhou,Xueru He,Shuai Liu,Feng Hong,Jiaqi Ren,Dongdong Li 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.6
More attention is being paid to energy effi ciency and harmonic reduction. Thus, power factor correction (PFC) is widely used in power supplies. However, under the condition of light load, the single-stage LLC PFC converter has the problems of low effi ciency and output voltage misaligned, such as other PFC topologies. Aiming at the problems that occur under light load conditions, this paper proposes a least-pulse delta (Δ)–sigma (Σ) modulation (LPΔ–Σ modulation). Under diff erent loads, the system can automatically select the appropriate pulse density and reduce the energy transfer to the secondary side by uniformly turning off the driving signals, which stabilizes the output voltage and improves the system effi ciency. Meanwhile, LPΔ–Σ modulation is more benefi cial for improving the PF value when compared with the burst mode under light load conditions. Experimental results show that LPΔ–Σ modulation based on the traditional dual-loop control can eff ectively stabilize the output voltage and improve effi ciency. When compared with the existing burst control scheme, it reduces the output voltage ripple and eff ectively improves the PF.
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Flicker‑free single‑stage LED drivers based on load current feedback strategy
Yuefei Zhou,Qiongya Lou,Xueru He,Runzhi Yuan 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.11
The traditional AC/DC light-emitting diode (LED) driver with high power factor causes LED flicker because of the imbalance between the fluctuating instantaneous AC input power and the DC output power. Large electrolytic capacitors are commonly connected in parallel as an energy storage element on the load side to absorb the output ripple and restrain LED flicker. However, the electrolytic capacitor’s short lifespan and high temperature instability reduce the reliability of LED drivers. To realize a new flicker-free LED driver with low cost and high reliability, a series second harmonic current compensation circuit (series SHCC) powered by double vice-side windings is adopted based on single-stage resonant LLC converter in this study, and a new control strategy based on load current feedback is proposed. The proposed load current feedback strategy (LCFS) is analyzed and optimized from the perspective of closed-loop output impedance to minimize the output current ripple and suppress LED flicker. The proposed LCFS is applicable to LED load, and the main-stage PFC based on LLC and the SHCC based on Buck can share the same current sampling circuit, which can evidently simplify the control circuit to achieve a low-cost design. Finally, a 240W experimental LED driver prototype with a wide input and output range is established. The experimental results demonstrate that under rated power, the output current fluctuation depth ( Mod_I(%) ) of the LED driver can be reduced to 3.93%, and the storage capacitance can be decreased by 89.7% under the same fluctuation depth.
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Zhou Yufei,Li Dongdong,Wang Yingying,Hong Feng,He Xueru,Liu Shuai,Sun Xiangfeng 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.4
The low coupling coeffi cient (CC) of loosely coupled transformer (LCT) can greatly aff ect the effi ciency of inductive power transfer (IPT) system. In order to improve the coupling coeffi cient and misaligned tolerance of LCT, this paper proposes a transformer structure with multiple independent small receiving coils. Respectively in ideal alignment and misalignment mode, the distribution of magnetic force lines and the variation law of CC of independent small receiving coils are analyzed. According to the relationship between the coupling coeffi cient matrix and the mutual inductance, the eff ective coupling coeffi cient (ECC) is deduced, and its variation with the misalignment distance is also analyzed. The ECC of the LCT with multi-receiver (MR) structure is almost unchanged. For the multiple loads' characteristics of receivers, by adopting S/P compensated topology, a 500 W outputs prototype of IPT system is established. The experimental results show that the ECC is improved and tolerance performance to lateral and rotational misalignment of proposed MR structure has good characteristics.
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