臺灣博碩士論文加值系統

本文研製一無電解電容發光二極體驅動電路。本驅動電路架構為雙級架構，前級為一昇壓型的功率因數修正電路而後級則是一LLC諧振式轉換器。由於功率因數修正電路輸出端為一帶有120 Hz漣波的直流電壓，此電壓會造成LED上有很大的電流漣波，故通常會使用電解電容來降低輸出電流漣波。但電解電容的使用降低了整個系統的壽命。故本文提出一類比的前饋控制電路來降低輸出電流漣波。將帶有120 Hz的漣波電壓作為前饋控制訊號，用此訊號來調整LLC的操作頻率以降低輸出電流漣波。最後，本文實際研製一可操作於輸入電壓90~264 VRMS，輸出為43 V/3.5 A之無電解電容發光二極體驅動電路。本電路之輸出電流漣波低於25 %且無光閃爍現象。功率因數於全域輸入電壓範圍為皆高於0.97，效率最高可達90 %，並滿足IEC 61000-3-2 Class C之國際規範。

In this thesis, a non-electrolytic capacitor LED driver with feed-forward control is proposed. It includes an AC-DC PFC converter and a DC-DC LLC resonant converter. Typically, the output of the AC-DC converter is a DC bus voltage with 120 Hz ripple, and this ripple will cause high current ripple on the LED load. Therefore, the electrolytic capacitor (E-cap) is used to reduce the output current ripple. But the use of the E-cap will lead to the shorter lifetime of the lighting system. In this thesis, an analog feed-forward control is proposed to reduce the output current ripple. In this control, the 120 Hz ripple signal acts as feed-forward signal. This signal can be used to modulate the switching frequency of the LLC resonant converter to reduce the output current ripple. Finally, the hardware prototype with an input voltage of 90~264 VRMS, output voltage of 43 V, and constant output current of 3.5 A/150 W is implemented to verify the proposed control schemes and the feasibility of the system. Under universal input voltage range, the output current ripple is below 25 % without electrolytic capacitor, and the power factor is higher than 0.97 and the highest efficiency is 90 %, which meets the IEC 61000-3-2 Class C standard requirements. Moreover, there is no visible flicker in the LED light output.

1 Introduction 1
1.1 Background and Motivation 1
1.2 Organization 6
2 Characteristics of LED and Drivers and Methods to Replace Electrolytic Capacitor 7
2.1 Characteristics and Equivalent Model of LED 7
2.2 Types of LED Drivers 10
2.3 Methods to Eliminate Electrolytic Capacitor 12
2.3.1 Harmonic Injection Method 12
2.3.2 LED Driver with Bidirectional Converter 13
2.3.3 LED Driver with Feed-forward Control 14
3 Operating Principles of the Proposed LED Driver 15
3.1 Two-stage LED Driver with Feed-forward Control 15
3.2 Operating Principles of the LLC Ressonant Converter 16
3.3 LLC Ressonant Converter with Feed-forward Control 25
4 Parameter Design of the Proposed LED Driver 31
4.1 Specifications of the Proposed LED Driver 31
4.2 Boost PFC Converter 31
4.3 LLC Resonant Converter 35
4.4 Feedforward Control Scheme 41
5 Experimental Results of the Proposed Converter 48
5.1 Specifications of the Proposed Converter 48
5.2 Experimental Waveforms and Analysis 49
5.3 Analysis of Power factor, Efficiency, Output Current Ripple 52
5.4 IEC 61000-3-2 Standard Compliance 55
5.5 Optical Characteristics of the Proposed LED Driver 57
6 Conclusions and Future Works 59
6.1 Conclusions 59
6.2 Future Works 60
References 61

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