應用於無線通訊的高效率封包追蹤電源轉換器

Highly Efficient Envelope Tracking Modulator for Wireless Communication

簡子皓(Tzu-Hao Chien)

指導教授 ： 陳景然

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202000932

摘要

封包追蹤電源轉換器通過提供追蹤射頻功率放大器輸出封包而不是固定的電源電壓來提高射頻功率放大器的效率。在封包追蹤電源轉換器的系統中，電路架構的不同將顯著影響功率效率。線性放大器輔助開關轉換器之並聯組合通常用於封包追蹤電源轉換器的系統中，以追求更好的功率效率，而不單只是線性放大器或開關轉換器。近年來，提出了一種用於線性放大器的交流耦合技術以提高封包追蹤電源轉換器系統的效率。然而，線性放大器的交流耦合電容如置於晶片外部，可能會為整個ETSM系統帶來額外的印刷電路板的面積。
本論文根據效率分析去解釋傳統線性放大器輔助開關轉換器之並聯組合電路在追蹤高頻封包訊號所面臨的困難，而提出了一種新的電路控制架構。此論文也提出功率分頻的方法來使提升功率效率。另外，此論文所提出的電路架構為在交流耦合技術為基礎上去做改良，將上述所提到的交流耦合電容從晶片的外部移置晶片內，大量節省了印刷電路板的面積。最後，本論文也會展示模擬和實驗結果，以驗證本論文所提出的概念。
本論文所提出的封包電源轉換器採用TSMC 0.18μm技術的IC中實現。根據測量結果，提出的混合轉換器在跟踪10MHz正弦波時將峰值功率效率提高到84.32％，並且在輸出電壓和參考電壓之間實現均方根誤差16.25mV。另外，測量結果顯示出第一和第二音調差為25dB時的線性性能。

關鍵字

封包追蹤 ； 電源轉換器 ； 交流耦合技術

並列摘要

The Envelope Tracking Supply Modulator (ETSM) improves the efficiency of a radio frequency power amplifier (RFPA) by providing a supply voltage which tracks the envelope of RFPA output instead of a fixed DC voltage. In an ETSM system, different topologies of circuit architecture affect the power efficiency significantly. Conventionally, a linear amplifier (LA) assisted switching converter (SW) is combined in parallel for an ETSM system to pursue better power efficiency instead of LA or SW only. In recent years, an ac-coupled technique for LA has been proposed to improve the efficiency of ETSM system. However, the off-chip ac-coupled capacitor for LA may cause extra printed circuit board (PCB) area for the whole ETSM system.
In this thesis, the efficiency analysis of hybrid converter is proposed for ETSM. Based on the efficiency analysis, the thesis explains the difficulties faced by the parallel combination circuit of the traditional linear amplifier auxiliary switching converter in tracking high-frequency signals, and proposed a new circuit control architecture. The proposed ETSM uses power separation method for the hybrid converter to improve the power efficiency. In addition, the proposed ETSM improves the ac-coupled technique by reducing the ac-coupled capacitor from off-chip to on-chip to improve the power efficiency. Finally, the simulations and experimental verifications were conducted to verify the proposed concepts.
The proposed hybrid converter is implemented in the IC with TSMC 0.18μm technology. According to the measurement results, the proposed hybrid converter improves the peak power efficiency to 84.32% and achieves 16.25mV of RMS error between Vout and Vref voltage under tracking 10MHz sine wave.

並列關鍵字

envelope tracking ； supply modulator ； ac-coupled technique

參考文獻

[1] M. Shafi et al., "5G: A tutorial overview of standards, trials, challenges, deployment, and practice," in IEEE Journal on Selected Areas in Communications, vol. 35, no. 6, pp. 1201-1221, June 2017.

[2] X. Ruan, Y. Wang, and Q. Jin, “A review of envelope tracking power supply for mobile communication Systems”, in CPSS Transactions on Power Electronics and Applications, vol. 2, no. 4, December 2017.

[3] H. He, T. Ge and J. Chang, "A review on supply modulators for Envelope-Tracking Power Amplifiers," in 2016 International Symposium on Integrated Circuits (ISIC), Singapore, 2016, pp. 1-4.

[4] H. He, Y. Kang, T. Ge, L. Guo and J. S. Chang, "A 2.5-W 40-MHz-Bandwidth hybrid supply modulator with 91% peak efficiency, 3-V output swing, and 4-mV output ripple at 3.6-V supply," in IEEE Transactions on Power Electronics, vol. 34, no. 1, pp. 712-723, Jan. 2019.

[5] W. Chu, B. Bakkaloglu and S. Kiaei, "A 10 MHz bandwidth, 2 mV ripple PA regulator for CDMA transmitters," in IEEE Journal of Solid-State Circuits, vol. 43, no. 12, pp. 2809-2819, Dec. 2008.