臺灣博碩士論文加值系統

隨著可攜式產品市場蓬勃發展，將眾多功能整合至同一模組上已是主流趨勢，這也使得產品越加耗電，電池續航力降低。然而，可攜式產品大多處於待機狀態，透過改善轉換器的輕載效率能有效延長電池續航時間。為了實現於寬負載範圍內均有良好轉換效率，以及因應負載劇烈變化時，能夠迅速提供穩定輸出電壓，快速暫態響應和智能開關技術在本論文中被提出。
本論文提出一具快速暫態響應之寬負載高效率降壓轉換器，在提升轉換效率部分，將功率電晶體切割成兩組，並依據當前負載電流的條件，開啟相對應的功率電晶體數量，使切換損失最佳化。除此之外也將電流偵測電路改良，使其能夠同時偵測兩組功率電晶體，省略了額外的電壓電流轉換器，達到減少晶片面積及提升轉換效率的效果。而在暫態響應部分，藉由改變誤差放大器的輸出級，將輸出電壓變化資訊回授給內部系統迴路，在暫態發生時，可提供額外的補償電流路徑至迴路補償器上，改變降壓轉換器的工作週期，使輸出電壓快速回到穩定，達到提升暫態響應的表現，而此技術也適用於現今常見的動態電壓調整技術。
最後本篇論文使用台灣積體電路公司0.35um 2P4M CMOS 製程實現，輸入電壓範圍從2.7V到4.2V，輸出電壓為1.8V，操作頻率2MHz，晶片面積為1.46 mm^2，負載電流範圍為30mA到600mA，轉換效率皆在91%以上，最高效率在250mA時有95.49%，暫態響應回復時間從輕載(50mA)到重載(500mA)及重載(500mA)到輕載(50mA)分別為14.8us和15us。適用於可攜式電子產品之電源管理。

As the development of the portable product market flourishing quickly, modularizing multiple function has become the mainstream. And this also made the power consumption higher, and shorter the battery life. However, portable devices stay in stand-by mode most of the time, through improving light – load efficiency of the converters is efficient to extend its’ battery life. To achieve the conversion efficiency in the wide-load range well, moreover, when in respond to dramatically change, enable to provide stable voltage rapidly. Therefore, fast transient response and smart switching technique are submitted in this thesis.
This thesis presents a wide load range high efficiency buck converter with fast transient response control. In the portion of increasing conversion efficiency, we separate power transistor into two parts, and according to the condition of the load current, open the power transistor correspondingly, which can achieve the optimal switching lose. Besides, improving current sensing circuit enables to detect both power transistors at the meantime, so as to reduce additional V-to-I converting circuit, and to reach the best efficiency effect of power transformation. As for fast transient response control, by changing the output stage of the error amplifier to transfer the output voltage variation to the inner system loop, when the load current changes transiently, it can provide additional compensational current path to the compensational resistor, and change the work period of the buck converter, making output voltage quickly back to stable, and improve the performance of transient response. And this technique is suitable for dynamic voltage scaling techniques usually seen nowadays.
This thesis is implemented with TSMC 0.35um 2P4M 5V CMOS process. The input voltage range of converter is from 2.7V to 4.2V, output voltage set at 1.8V, operating frequency 2MHz, and chip area 1.465 mm^2. The range of load current is 30mA to 600mA and the conversion efficiency is all above 91%. The maximum efficiency will be 95.49% at 250mA. The recovery time of transient response, from light load (50mA) to heavy load (500mA) and heavy load (500mA) to light load (50mA) are 14.8us and 15us, respectively. For what have mentioned above are suitable for the power management of portable electronic products.

List v
List of Figures viii
List of Tables xii
Chapter 1 Introduction - 14 -
1.1 Background and Motivation - 14 -
1.2 Thesis Organization - 17 -
Chapter 2 Fundamental of DC-DC Regulators - 18 -
2.1 Linear Regulator - 18 -
2.2 Switching Capacitor Regulator - 19 -
2.3 Switching Regulator - 20 -
2.3.1 Buck Regulator - 21 -
2.3.2 Boost Regulator - 22 -
2.3.3 Buck-Boost Regulator - 24 -
2.3.4 Synchronous and Asynchronous Switching Regulator - 26 -
2.3.5 Comparison of Power Regulators - 28 -
2.4 Modulation Technique of Switching Regulator - 29 -
2.4.1 Pulse Width Modulation (PWM) - 29 -
2.4.2 Pulse Frequency Modulation (PFM) - 30 -
2.4.3 Power Loss Comparison of PWM and PFM - 32 -
2.5 Significant Specifications of Switching Regulator - 33 -
2.5.1 Conversion Efficiency - 33 -
2.5.2 Line Regulation - 34 -
2.5.3 Load Regulation - 35 -
2.5.4 Transient Response - 35 -
Chapter 3 Design Principle of Current Mode Buck Regulator - 37 -
3.1 Controlling Method of Buck Regulator - 37 -
3.1.1 Voltage Mode Control - 37 -
3.1.2 Current Mode Control - 38 -
3.2 Sub-harmonic Oscillation of Current Mode Control - 40 -
3.3 The Method of Ramp Compensation - 43 -
3.4 Stability Analysis of Current Mode Buck Regulator - 45 -
3.4.1 PWM Modulator Gain - 46 -
3.4.2 Current Sampling Gain - 47 -
3.4.3 Control to Output Gain - 49 -
3.4.4 PI Compensation Analysis - 50 -
3.5 Smart Switch Control Technique - 52 -
3.5.1 Design Method of Smart Switch Control - 53 -
3.5.2 The Problems of Smart Switch Control - 54 -
3.6 Fast Transient Technique - 56 -
3.6.1 Current Mode Buck Regulator with Fast Transient Technique- 56 -
3.6.2 Error Amplifier with Fast Transient Control Circuit - 59 -
Chapter 4 Circuit Implementation and Simulation Results - 62 -
4.1 Bias Circuit with Start-Up - 63 -
4.2 Bandgap Voltage Reference Circuit - 66 -
4.3 Error Amplifier - 69 -
4.4 Hysteresis Comparator Circuit - 71 -
4.5 Soft-Start Circuit - 74 -
4.6 Ramp and Clock Generator - 76 -
4.7 Current Sensing Circuit - 78 -
4.8 Voltage to Current Converter - 82 -
4.9 Smart Non-overlap Buffer - 85 -
4.10 Dual Switch Control Circuit - 87 -
Chapter 5 System Simulation Results, Layout and Measurement- 91 -
5.1 System Simulation Results - 91 -
5.1.1 Soft-Start Simulation - 91 -
5.1.2 Line Regulation - 92 -
5.1.3 Load Regulation - 94 -
5.1.4 Output Voltage Ripple - 96 -
5.1.5 Transient Response - 98 -
5.1.6 Conversion Efficiency - 102 -
5.2 Full Circuit Layout - 104 -
5.2.1 Layout Consideration - 106 -
5.3 Chip Measurement - 109 -
5.3.1 PCB Layout - 109 -
5.3.2 Measurement Setup - 110 -
5.4 Comparison of proposed Buck Regulator - 113 -
Chapter 6 Conclusion and Future Work - 114 -
6.1 Conclusions - 114 -
6.2 Future Work - 115 -
References - 116 -

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