Abstract
Because it is magnet-free and can achieve a high integration level, the switched-capacitor (SC) converter acting as a direct current transformer has many promising applications in modern electronics. However, designing an SC converter with large current capability and high power efficiency is still challenging. This paper proposes a dual-branch SC voltage divider and presents its integrated circuit (IC) implementation. The designed SC converter is capable of driving large current load, thus widening the use of SC converters to high-power applications. This SC converter has a constant conversion ratio of 1/2 and its dual-branch interleaved operation ensures a continuous input current. An effective on-chip gate-driving method using a capacitively coupled floating-voltage level shifter is proposed to drive the all-NMOS power train. Due to the self-powered structure, the flying capacitor itself is also a bootstrap capacitor for gate driving and thus reduces the number of needed components. A digital frequency modulation method is adopted and the switching frequency decreases automatically at light load to improve light load efficiency. The converter IC is implemented using a 180 nm triple-well BCD process. Experimental results verify the effectiveness of the dual-branch interleaved operation and the self-powered gate-driving method. The proposed SC divider can drive up to 4 A load current with 5–12 V input voltage and its power efficiency is as high as 96.5%. At light load, using the proposed optimization method, the power efficiency is improved by 30%.
摘要
由于无磁且容易实现高集成度, 开关电容 (SC) 变换器作为一种直流变压器在现代电子领域具有广泛应用前景. 然而, 设计具有大电流和高功率的SC变换器仍面临挑战. 本文提出一种双支路SC分压器拓扑, 并通过集成电路 (IC) 得以实现. 所设计SC变换器能驱动大电流负载, 将其使用范围扩展至大功率应用场合. 该SC变换器具有1/2的恒定变换比, 其双支路交错操作方式可确保输入电流的连续性. 此外, 提出一种使用电容耦合型浮动电压电平转换器的片上栅极驱动方法有效驱动全NMOS功率链. 通过自供电结构, 飞电容器本身也是用于栅极驱动的自举电容器, 从而减少所需元器件数量. 采用数字调制方式, 在轻载时自动降低开关频率以提高效率. 所设计SC变换器IC使用180 nm三阱BCD工艺制造. 实验结果证明了所提双支路交错操作方式和自供电栅极驱动方法的有效性. 所设计SC变换器可在5至12 V的输入电压下驱动高达4 A的负载电流, 功率效率高达96.5%. 在轻负载条件下, 使用所提优化方法, 电源效率提高了30%.
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Acknowledgements
The authors would like to thank the help and support from the Rockchip Electronics’ R&D Center in Shanghai, China.
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Sheng LIU, Zhao YANG, and Haonan WU designed the converter and performed the test. Menglian ZHAO supervised the research work. Sheng LIU drafted the paper. Xiaobo WU helped organize the paper. Sheng LIU and Menglian ZHAO revised and finalized the paper.
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Sheng LIU, Menglian ZHAO, Zhao YANG, Haonan WU, and Xiaobo WU declare that they have no conflict of interest.
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Project supported by the Zhejiang Provincial Natural Science Foundation of China (No. LY18F040001)
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Liu, S., Zhao, M., Yang, Z. et al. A large-current, highly integrated switched-capacitor divider with a dual-branch interleaved topology and light load efficiency improvement. Front Inform Technol Electron Eng 23, 317–327 (2022). https://doi.org/10.1631/FITEE.2000404
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DOI: https://doi.org/10.1631/FITEE.2000404