臺灣博碩士論文加值系統

本篇論文提出具有冷起動電路之升壓轉換器來達到熱電能量擷取的功能，以及降壓-升壓轉換器來完成能量重複利用的電源管理單元。採用了峰值電流控制的技巧來達到最大功率提取(maximum power extraction)。使用零電流切換的技術來避免逆向的電感電流以確保高轉換效率。 再者，非同步控制技巧不僅節省了系統時脈產生器的功率消耗，而且因為使用了控制信號交換(handshaking)的技巧使系統更為穩定。此外，採用多輸出的架構來最小化後級低壓降線性穩壓器(low-drop-out linear regulator)的壓降，如此一來可以減少消耗在低壓降線性穩壓器的功率消耗。然而，多輸出架構會具有很多不同的電壓準位，所以提出了贏者全拿的高電壓選擇器在這些多種的電壓準位中選擇出目前系統內部的最高電壓，如此一來，所有的功率開關都能夠被良好的控制以避免漏電流。此外，為了達到最大功率點追蹤(maximum power point tracking)而採用開路電壓偵測(fractional open-circuit voltage)的方法。使用二進位搜尋(binary search)及爬山(hill-climbing)的演算法以達到快速的追蹤速度及較小的輸入電壓漣波。此晶片採用 0.35微米的互補式金氧半製程來實現。量測結果顯示:冷起動電路可在400mV的輸入電壓將系統啟動且冷起動時間約為65毫秒。

The power management unit (PMU) with cold-start-up circuit and main boost converter (MBC) for thermoelectric energy harvesting and buck-boost converter (BBC) for energy reuse is presented. The peak current control scheme is adopted to achieve maximum power extraction (MPE). Additionally, the zero-current switching (ZCS) control skill is utilized to prevent reverse inductor current so that the high conversion efficiency can be ensured. Moreover, the asynchronous control method not only saves the power consumption of system clock generator, but also makes the system more robust since handshaking skill is used. Besides, multiple-output structure is used to minimize the voltage drop on the low-drop-out regulators (LDOs), which reduces the power lost in LDOs. However, the multiple-output structure possesses different voltage domains. Therefore, the winner-take-all high voltage selector is proposed to choose the highest voltage among different voltage domains so that the power switches can be well controlled to prevent leakage current. Furthermore, the method of fractional open-circuit voltage (FOCV) is adopted for the purpose of maximum power point tracking (MPPT). The binary search and hill-climbing algorithms are utilized for MPPT to possess fast tracking speed and lower ripple of input voltage. The chip is fabricated in 0.35um CMOS process. The measurement results shows that the cold-start-up circuit can start-up the system when input voltage equals to 400mV and the start-up time is about 65 milliseconds.

Contents
Abstract in Chinese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Abstract in English . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Design Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Floating-gate Transistor and Reliability . . . . . . . . . . . . . . . . . . 5
2 Background Knowledge of DC-DC Converters . . . . . . . . . . . . . . . . . . 9
2.1 DC-DC Converter for Voltage Scaling . . . . . . . . . . . . . . . . . . . 9
2.1.1 Linear Regulators . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.2 Switching Capacitor DC-DC Converters . . . . . . . . . . . . . . 9
2.1.3 Inductor-based Switching DC-DC Converters . . . . . . . . . . . 11
2.2 Fundamentals of DC-DC Boost Converters . . . . . . . . . . . . . . . . 11
2.2.1 The Principle of Inductor Volt-second Balance . . . . . . . . . . 11
2.2.2 The Principle of Capacitor Charge Balance . . . . . . . . . . . . 12
2.2.3 The Principle of Small Ripple Approximation . . . . . . . . . . . 13
2.3 Introduction of Operation Principle . . . . . . . . . . . . . . . . . . . . . 14
2.3.1 Discontinuous Conduction Mode (DCM) . . . . . . . . . . . . . 14
2.3.2 Continuous Conduction Mode (CCM) . . . . . . . . . . . . . . . 15
2.3.3 Boundary Conduction Mode (BCM) . . . . . . . . . . . . . . . . 15
2.4 The Mechanisms of Closed-loop Control . . . . . . . . . . . . . . . . . . 17
2.4.1 Pulse-width Modulation (PWM) . . . . . . . . . . . . . . . . . . 17
2.4.2 Pulse-frequency Modulation (PFM) . . . . . . . . . . . . . . . . 18
2.5 Analysis of Power Loss and Conversion Efficiency . . . . . . . . . . . . 19
3 Proposed Thermoelectric Energy Harvesting Unit . . . . . . . . . . . . . . . . 20
3.1 System Architecture and Operation . . . . . . . . . . . . . . . . . . . . . 20
3.1.1 Cold-start-up Circuit . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1.2 Main Boost Converter . . . . . . . . . . . . . . . . . . . . . . . 26
3.1.3 Buck-boost Converter . . . . . . . . . . . . . . . . . . . . . . . 32
3.2 Design Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2.1 Maximum Power Point Tracking . . . . . . . . . . . . . . . . . . 35
3.2.2 Power Loss Analysis . . . . . . . . . . . . . . . . . . . . . . . . 37
3.3 Circuit Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.3.1 Maximum Power Point Tracking Control Block . . . . . . . . . . 41
3.3.2 Peak Current Control Block . . . . . . . . . . . . . . . . . . . . 46
3.3.3 Floating-gate switched-capacitor Comparator . . . . . . . . . . . 48
3.3.4 Floating-gate-soft-start Voltage Detector . . . . . . . . . . . . . . 50
3.3.5 Zero-current-switching Comparator . . . . . . . . . . . . . . . . 52
3.3.6 Winner-take-all High Voltage Selector . . . . . . . . . . . . . . . 55
3.3.7 Constant or Adaptive On-time Control for Buck-boost Converter . 59
4 Measurement Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.1 Comparison and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . 68
5.2 Future Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Letter of Authority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

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