高輕載轉換效率之切換式直流降壓轉換器

A Switching Buck Converter with Improved Light-load Efficiency

廖建貳(Chien-Erh Liao)

指導教授 ： 黃崇勛

國立中正大學/工學院/電機工程學系/碩士(2016年)

摘要

本論文針對本實驗室最大轉換效率追蹤改善轉換效率的技術，研究其優缺點，並以提高輕載轉換效率，寬操作範圍轉換效率即時偵測為主軸來設計。目前本實驗室團隊降壓型轉換器的改善電源轉換效率的技術有依照需求切換調節器(SOM)與最大轉換效率追蹤(MPET)兩大方向。前者著重改善中輕載轉換效率，後者著重於輕載與極輕載狀況，然而在SOM的基礎下，初版MPET對於何時該截止不需運作之電路區塊，其作法是固定計數所遮罩之CLK數來決定，此做法會隨著整體電路設計不同而不適用，而無法在適合的時間點來啟動截止機制，進而導致轉換效率的降低。
綜合以上的討論，本論文提出一最大轉換效率即時追蹤機制(Real-Time Maximum Power Efficiency Tracking Technique)，可以即時偵測電源轉換效率，進而找到適合的截止點，並且適用於不同設計者的電路當中，此機制解決了初版MPET僅適用單一電路的缺點，並有效提高輕載轉換效率，其原理是設計一電路去計算輸出入功率，並且對應出一條隨負載而改變的轉換效率曲線，即時監測控制系統電路區塊所佔的消耗功率比例，當轉換效率低於一個臨界值時，表示靜態功率為主要消耗功率，此時即讓不需要運作的電路進入截止狀態，此外本論文設計一Energy Self-supply 電路，於極輕載開迴路狀況，關閉佔功率消耗比重很高的誤差放大器時，可以自動的補充能量到負載端，達到穩壓且降低靜態功率消耗的目的，讓極輕載時的轉換效率更佳，結合SOM與RT-MPET電路能使降壓型轉換器在寬負載操作範圍下依然維持高電源轉換效率。
本論文使用台積電TSMC 0.18μm 1P6M 3.3V Mixed Signal製程製作，使用改良版之最大轉換效率追蹤機制，可在一個寬廣的負載操作範圍下，即時偵測截止點，以達高輕載轉換效率。本論文極輕載時的轉換效率可達72%，負載操作範圍可從1mA到500mA的區間。

關鍵字

最大轉換效率追蹤技術 ； 寬操作範圍 ； 高輕載轉換效率 ； 直流降壓轉換器 ； 最大轉換效率即時追蹤機制

並列摘要

In this thesis, existing MPET(Maximum Power Efficiency Tracking Technique) to improve power conversion efficiency in CCU LPIC lab. is investigated to design power efficiency tracking fuction for wide load operative range and high light-load efficiency. There are two major directions to improve power conversion efficiency for existing technology of buck converter in CCU LPIC lab, SOM(Switch-On-Demand Modulator), and MPET. The former focuses on improving medium or light-load efficiency, and the latter focuses on light or ultra light-load status. In the first edition MPET which based on SOM , it was concerned when is the appropriate time to shut down the circuit block which without work. The method depends on counting the numbers of CLK which had been masked. It is unsuitable that it will change as the whole circuit system change, and it’s hard to start the mechanical cut-off at the appropriate time. In this condition, it will cause the power consumption to diminish its efficiency.
Regarding the above discussion, this thesis proposes the second edition MPET which is called Real-Time Maximum Power Efficiency Tracking Technique. It can track power efficiency for wide load operative range on accuracy time. It can not only find the right time to shut down circuit, but also suit with circuits made of different designers. The technique solves the flaw that is the first edition MPET just suitable for unique circuit, and improves light-load efficiency effectively. The principle is design a circuit to compute the input and output power, and maps to one power conversion efficiency line which vary from load status. Furthermore, it can monitor power consumption in control stage circuit blocks. Once the efficiency line is below a threshold voltage, it will mean static loss is dominated in whole power loss. At the moment we shut down the circuit blocks which without work. Further, this thesis design a Energy Self-supply circuit, it can supply energy to load automatically in ultra light-load and open loop status if the power hungry ampilier is shut down. We couled achieve the purpose that output voltage is stable and static loss can be decreased, it makes the Light-load Efficiency better, the buck converter combinated with SOM and RT-MPET operates in the wide load range and maintains high power conversion efficiency.
Finally, this buck converter chip is designed and fabricated with TSMC 0.18μm 1P6M 3.3V Mixed Signal process technology. The chip use the improved version for maximum power efficiency tracking technique. This technology can operate in the wide load range, and track power efficiency for high light-load efficiency. In this thesis, light-load efficiency is over 72%, and operate from 1mA to 500mA load current.

並列關鍵字

Maximum power efficiency tracking technique ； Wide load range ； High light-load efficiency ； Switching buck converter ； Real-time maximum power efficiency tracking technique

參考文獻

[2]陳柏毅，“具備最大轉換效率追蹤技術之寬操作範圍降壓轉換器”，國立中正大學電機工程研究所，2013。

[6]Cheung Fai Lee and Philip K. T. Mok, “A Monolithic Current-Mode CMOS DC-DC Converter with On-Chip Current-Sensing Technique,” IEEE J. Solid-State Circuits, vol. 39, no. 1, pp. 3-14, Jan. 2004.

[8]B. Sahu, and Gabriel A. Rincon-Mora, “An accurate, low-voltage, CMOS switching power supply with adaptive on-time pulse-frequency modulation (PFM) control,” IEEE Transactions on Circuits System I, vol. 54, no. 2, pp. 312-321, Feb. 2007.

[9]Hong-Wei Huang, Chieh-Ching Chien, Ke-Horng Chen, and Sy-Yen Kuo, “Highly Efficient Tri-Mode Control of Buck Converters with Load Sensing Technique,” in Proceedings of 37th IEEE 2006 Power Electronics Specialists

[11]Feng Su, Wing-Hung Ki, and Chi-Ying Tsui,“Ultra Fast Fixed-Frequency Hysteretic Buck Converter With Maximum Charging Current Control and Adaptive Delay Compensation for DVS Applications,” IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 43, NO. 4, APRIL 2008.