漣波控制固定導通時間降壓轉換器之設計

Design of the Ripple-Based Constant On-Time Controlled Buck Converters

楊子玄(Tzu-Hsuan Yang)

指導教授 ： 林宗賢

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201804185

摘要

在一個積體電路系統中，電源管理晶片扮演了相當重要的角色，其負責提供一個穩定的電壓源，本論文實作並量測兩個直流對直流降壓轉換器。
第一個作品驗證了漣波控制固定導通時間降壓轉換器，在負載較輕時具有變頻的功能，進而提升漣波控制在輕載時的效率。本作品輸入電壓為三點三伏特，輸出電壓為一點二伏特，並使用一微米亨利的電感及四點七微米法拉的電容，操作頻率為二百五十萬赫茲，輸出電流最高可達到一點七安培，最高效率為90.4 %，與定頻控制相比，輕載效率可由70.3 %提升至76.4%。
第二個作品改善了第一個作品的輸出漣波問題，並實作一個可降電磁干擾的導通時間產生器，使得輸出的功率頻譜密度，不會透過電磁干擾影響後方電路。本作品使用了積層陶瓷電容，即使在輸出電容的寄生電阻很小的狀況下，藉由電流迴授維持系統的穩定度，且透過雙迴授路徑，進而消除漣波控制固有的輸出電壓的直流準位問題。本作品輸入電壓為三點三伏特，輸出電壓為一點二伏特，使用一微米亨利的電感及四點七微米法拉的電容。輸出電流最高可達到一點七安培，最高效率為89.13 %，在定頻模式下，輸出電壓漣波為十毫米伏特，操作頻率藉在二百五十萬赫茲到五百五十萬赫茲間，且與定頻模式相比展頻的輸出功率頻譜密度可下降二十點七三分貝。

關鍵字

漣波控制 ； 固定導通時間 ； 降壓轉換器

並列摘要

Power management IC (PMIC) is a critical building block in integrated circuits for providing stable supply voltages. Two DC-DC converters are implemented and verified in this thesis.
The first work verifies that the ripple-based constant on-time controlled buck converter under light load condition has the characteristic of pulse frequency modulation (PFM). With this merit it can improve the efficiency. This work steps down the input voltage 3.3 V to the output voltage is 1.2 V and realizes with 1 μH inductor and 4.7 μF capacitor. The switching frequency is 2.5 MHz. The maximum output current is 1.7 A. The maximum efficiency is 90.4 %. Comparing with the efficiency of the constant frequency control, our work can improve the efficiency from 70.3 % to 76.4 %.
The second work improves the problems of output voltage ripple in the first work and implements an EMI reduction on-time generator. The output power spectral density will not affect the back-end circuit through the electromagnetic interference. This work utilizes the multi-layer ceramic capacitor as the output capacitor. Even the value of parasitic resistance is small. The system can be stable by using current feedback loop. By using the voltage square feedback path, this converter eliminates the inherent dc offset voltage in the ripple-based constant on-time control. This work is realized with 1 μH inductor and 4.7 μF capacitor. The input voltage is 3.3 V and the output voltage is 1.2 V. The maximum output current is 1.7 A. The maximum efficiency is 89.13 %. The output ripple is 10 mV in constant frequency mode. The switching frequency is operated between 2.5 MHz to 5.5 MHz. Comparing with the constant frequency operation the output power spectral density of spread spectrum mode can be reduced 20.73 dB.

並列關鍵字

Ripple-based control ； Constant on-time control ； Buck converter

參考文獻

[1] R. W. Erickson, D. Maksimovic, Fundamentals of Power Electronics 2/e, Springer, 2001.

[2] K. H. Chen, Power Management Techniques for Integrated Circuit Design, Wiley, 2016.

[3] Y. K. Chen, “A Fast Response Low Jitter Constant On-Time Controlled Buck Converter,” National Taiwan University Master Thesis, Jan. 2018.

[4] J. Baek, J. H. Lee, S. U. Shin, M. Y. Jung, and G. H. Cho, “Switched Inductor Capacitor Buck Converter with > 85% Power Efficiency in 100 uA-to-300 uA Loads using a Bang-Bang Zero-Current Detector,” IEEE Custom Integrated Circuits Conference (CICC), pp. 1-4, Apr. 2018.

[5] R. Redl and J. Sun, “Ripple-Based Control of Switching Regulators—An Overview,” IEEE Transactions on Power Electronics, vol. 24, no. 12, pp. 2669-2680, Dec. 2009.