習知的LED 驅動電路系統有多種架構，本論文以交換式轉換器中的馳返式轉換器為研究主題，原因在於其具有穩定的輸出電流並可符合一般之商業安全規範。因此針對馳返式轉換器進行晶片設計，目的是為了達到準諧振邊界導通和輸出電流調整。本論文提出之方案具有負載輸出電流估算、二極體導通時間偵測，以及脈波寬度調變控制電路，以產生開關訊號。另外，本論文亦討論電路的穩定性問題，並提出了補償電路，以濾除不必要的雜訊，降低輸出漣波振幅。

為了達到準諧振模式，波谷電壓偵側器的準確性非常重要，當返馳式轉換器內部二次側電感電流不能再提供給負載時，一次側電感和功率電晶體之寄生電容發生振盪。因此可利用波谷偵測器來偵測波谷，並將此訊號送往脈寬調變電路來決定功率電晶體的導通時間。波谷訊號非常容易誤判且不準確，若是在交流電經由橋式整流完之M 型波零點時，因能量過低導致振盪的振幅太小，使波谷電壓偵測電路無法偵測訊號，功率電晶體再也無法開啟。為了避免上述情況發生，本論文提出了防護電路以避免，並且提出第二種波谷電壓偵測電路來增加精準度，使之能更準確的偵測到波谷，並達到谷值切換，具有更高的效率。另外考量到晶片製程漂移導致控制晶片失效之可能，本論文亦提出了製程偵測電路，利用偵測結果補償運算放大器之相位邊際(phase margin)，以提高系統之穩定程度。

本論文之LED 驅動電路輸出電壓範圍在6~60 V，並以0.7 A 之固定電流驅動LED，並且使用單極的功率因子修正器(power factor corrector, PFC)。另外，在4顆LED 負載的情況下，可達到最大效率92.61%。

Although conventional LED drivers might be realized with different structures, we select Flyback converter design as the research topic in this thesis, The reason is that not only it provides the stability of the output current, but also meets certain safety requirement.The purpose of the proposed Flyback control chip is to achieve quasi-resonant boundary conduction and provide stable current regulation. Thus, the proposed design
comprises load output current estimation circuit, diode conduction time detection circuit,and pulse width modulation control circuit to generate a switch signal. Besides, the stability is analyzed and a compensation circuit is proposed to filter out unnecessary noise and reduce the ripple coupled in the output.


In order to achieve the quasi-resonant mode control, the accuracy of Valley Detector is very important. When the secondary side inductor current can no longer be supplied to the load, it will cause oscillation between parasitic capacitance of the primary inductor and the power transistor. As soon as the valid valley is detected, an enable signal is delivered to PWM circuit to determine the turn-on time of the power transistor. However, the valley signal is hard to be detected accurately. The worst scenario is that the wrong detection will cause that the power transistor can no longer be turned on. Therefore, a protection circuit is proposed to prevent the case and improve the accuracy such that the efficiency is enhanced. Regarding the chip process variation, a detection circuit is added, which output is used to compensate the phase margin of the operational amplifier.

The output voltage range of the LED driver based on the proposed design is 6 to 60 V, where LEDs are driven by a fixed 0.7 A with a single stage power factor corrector. As a result, it can achieve the maximum efficiency 92.61% given four LED loads.

論文審定書. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
論文摘要. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
圖目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
表目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii
1 研究背景與動機. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 前言. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 相關文獻與研究探討. . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.1 柔性切換. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.2 屏蔽時間. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3 研究動機. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.4 論文大綱. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2 返馳式LED 驅動器與輸出電流回授控制電路. . . . . . . . . . . . . . . . . 14
2.1 簡介. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2 LED 驅動系統架構. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 返馳式轉換器開關頻率設計. . . . . . . . . . . . . . . . . . . . . . . 15
2.3.1 返馳式轉換器之運作. . . . . . . . . . . . . . . . . . . . . . . 20
2.4 晶片電路架構. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.4.1 二極體導通時間偵測電路設計. . . . . . . . . . . . . . . . . . 25
2.4.2 負載輸出電流估算電路設計. . . . . . . . . . . . . . . . . . . 27
2.4.3 製程偵測電路. . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.4.4 回授補償電路設計. . . . . . . . . . . . . . . . . . . . . . . . 34
2.4.5 波谷偵測電路. . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.4.6 PWM 控制電路設計. . . . . . . . . . . . . . . . . . . . . . . . 45
2.5 晶片模擬與規格. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.5.1 二極體導通時間電路模擬. . . . . . . . . . . . . . . . . . . . 49
2.5.2 製程偵測電路模擬. . . . . . . . . . . . . . . . . . . . . . . . 51
2.5.3 誤差放大器相位邊際補償模擬與統計. . . . . . . . . . . . . . 55
2.5.4 高壓緩衝器模擬. . . . . . . . . . . . . . . . . . . . . . . . . . 55
2.5.5 波谷偵測電路模擬. . . . . . . . . . . . . . . . . . . . . . . . 56
2.5.6 脈波寬度調變控制電路模擬. . . . . . . . . . . . . . . . . . . 56
2.5.7 系統模擬整理. . . . . . . . . . . . . . . . . . . . . . . . . . . 58
2.6 晶片實作與量測結果. . . . . . . . . . . . . . . . . . . . . . . . . . . 58
2.6.1 晶片照相. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2.6.2 晶片與系統量測結果. . . . . . . . . . . . . . . . . . . . . . . 59
2.7 結果與討論. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3 改良型波谷偵測器. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.1 簡介. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.2 振盪頻率推導. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.3 改良型波谷偵測器架構. . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.3.1 屏蔽時間推導. . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.4 改良型波谷偵測晶片模擬. . . . . . . . . . . . . . . . . . . . . . . . . 68
3.5 結果與討論. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4 結論與未來研究方向. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.1 研究成果與結論. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.2 未來研究方向. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
參考文獻. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

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