臺灣博碩士論文加值系統

　本論文提出一具無損失緩振電路之泛用輸入電壓單級功因修正返馳式發光二極體驅動器。為提供高功率因數與低總諧波失真率，單級功因修正返馳式轉換器被運用。此外，為降低功率開關之電壓應力、提昇功率轉換之效率、調節輸出電壓，無損失緩振網路與隔離式輸出電壓感測網路的觀念被採用。無損失緩振網路與隔離式輸出電壓感測網路的兩個繞組被整合成一共同繞組以降低元件數。
最後，實做一24W具無損失緩振電路之泛用輸入電壓單級功因修正返馳式發光二極體驅動器以驗證其功能，如功率開關之電壓應力、功率轉換之效率、功率因數、總諧波失真率、輸入電流諧波。

This thesis presents a proposed universal-input single-stage PFC flyback LED driver with the lossless snubber circuit. In order to provide high power factor and low total harmonic distortion, the single-stage PFC flyback converter is employed. Moreover, in order to reduce the voltage stress on the power switch, increase the power-conversion efficiency, regulate the output voltage, the concepts of the lossless-snubber network and the isolated output-voltage-sensing network are adopted. The two windings of the lossless-snubber network and the output-voltage-sensing network are integrated as one common winding to reduce the component count
Finally, a prototype circuit of the 24W universal-input single-stage PFC flyback LED driver with the lossless snubber circuit is built to verify the performances, such as voltage stress on the power switch, power conversion efficiency, power factor, total harmonic distortion, and input current harmonics.

TABLE OF CONTENTS
CHAPTER 1. INTRODUCTION……………..........…..............………….…………………….. 1
1.1. BACKGROUND………………...……………...………………………………………….. 1
1.1.1. Two-Stage AC-DC PFC Flyback Converter……..………...……………….…… 2
1.1.2. Single-Stage AC-DC PFC Flyback Converter…...…………...…………….…… 3
1.2. MOTIVATION…………………...…………...……………..…………………………….. 4
1.3. THESIS OUTLINE……………...…….……………………..…………………………….. 5
CHAPTER 2. PROPOSED UNIVERSAL-INPUT SINGLE-STAGE PFC FLYBACK CONVERTER WITH LOSSLESS SNUBBER CIRCUIT…………….....…………………………. 6
2.1. INTRODUCTION……………………..…………………………………………………… 6
2.2. REVIEW OF SINGLE-STAGE PFC FLYBACK CONVERTER………..………………..………. 7
2.3. PROPOSED UNIVERSAL-INPUT SINGLE-STAGE PFC FLYBACK CONVERTER WITH
LOSSLESS SNUBBER CIRCUIT..………...…………………..…..………...………………. 9
2.4. SUMMARY…………...………………………………………..…………………….….. 14
CHAPTER 3. DESIGN OF PROPOSED UNIVERSAL-INPUT SINGLE-STAGE PFC FLYBACK
CONVERTER WITH LOSSLESS SNUBBER CIRCUIT...............……….………… 15
3.1. INTRODUCTION…………………………………………………..……….……………. 15
3.2. PRINCIPLES OF OPERATION……………...………………………...……………………. 15
3.3. DESIGN GUIDELINES FOR PROPOSED CIRCUIT TOPOLOGY………..……………..……… 23
3.3.1. Universal-Input Single-Stage PFC Flyback Converter…..……………………. 25
3.3.2. Lossless Snubber Circuit…………….………….....……..……………………. 33
3.3.3. Low-Dropout Constant-Current White LED Bias Supply...………………...…. 36
3.3.4. Positive Temperature Coefficient Thermistor for Temperature Protection.....… 37
3.4. SUMMARY…………………………………………………………..………………….. 38

CHAPTER 4. EXPERIMENTAL RESULTS…………………………...……..………………… 39
4.1. INTRODUCTION………………………………………………………..……………….. 39
4.2. IMPLEMENTATION OF PROTOTYPE CIRCUIT…………………………..………………… 39
4.3. EXPERIMENTAL RESULTS…………………...………………………………………..… 42
4.3.1. Measured Waveforms…………………………………….....…………………. 42
4.3.2. Measured Voltage Stress on the Switch…………………….......………..……. 47
4.3.3. Measured Power Conversion Efficiency……………………..…………......…. 50
4.3.4. Measured Power Factor………………………………………..………………. 52
4.3.5. Measured Total Harmonic Distortion…………………….................…………. 53
4.3.6. Measured Input Current Harmonics…………………………..…..………...…. 54
4.3.7. PTC Thermistor for Temperature Protection…………...……..…..………...…. 58
4.4. SUMMARY……………………………………………………………..……………….. 61
CHAPTER 5. CONCLUSIONS AND FUTURE WORKS…………..……...…..…………...……. 62
REFERENCES………………………………………………………..…..………...……… 64
APPENDIX A. CALCULATION OF MAGNETIZING INDUCTOR AND LEAKAGE INDUCTOR…. 66
APPENDIX B. DESIGN PROGRAM FOR TRANSFORMER…………………..………...……… 68
APPENDIX C. DESIGN PROGRAM FOR SWITCHING FREQUENCY AND OUTPUT
CAPACITOR………….……………………………………………………… 75
APPENDIX D. COMPARISON OF LED BRIGHTNESS……...…………...….………...……… 77
APPENDIX E. PHOTOGRAPH OF PROTOTYPE CIRCUIT………………….………...……… 78
VITA..................................................................................................................................... 79

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