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。本驅動電路架構結合單級返馳式功因修正電路與電流漣波消除器。返馳式功因修正電路以準諧振模式操作，藉由波谷電壓切換以降低開關之切換損失。由於電解電容為限制發光二極體系統壽命之主要元件，故使用無電解電容之電流漣波消除器取代電解電容，藉由高頻切換降低所需電容容值，將帶有兩倍線頻率之輸出電流漣波最小化為直流，並提升系統壽命。本文分析與探討固定責任週期與脈寬調變兩種電流漣波消除器控制方法之特性，將兩倍線頻率之輸出電流漣波最小化。最後，本文實際研製一可操作於輸入電壓90~264 VAC，於24~32 VDC輸出電壓範圍內，輸出定電流700 mA / 20 W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25.76%，且於滿載到20%負載輸出皆無光閃爍現象。功率因數於全域輸入電壓範圍為皆高於0.94，並滿足IEC 61000-3-2 Class C之國際規範。

In this thesis, a non-electrolytic-capacitor AC-DC LED driver is proposed, which includes an AC-DC PFC flyback converter and an AC current ripple eliminator. The flyback converter is operated with the quasi-resonant (QR) control technique to reduce the switching loss of the switch in the flyback converter. The AC current ripple eliminator is used to replace the short lifetime electrolytic capacitors to improve the lifetime and reliability of the LED system. Film or ceramic capacitors can be used in the proposed LED driver, while the AC current ripple eliminator minimizes the double-line-frequency output current ripple. In addition, the proposed driver can supply the LEDs with a constant output current. Also, constant duty ratio control and PWM control methods for the AC current ripple eliminator are proposed and analyzed, which can achieve the minimum output current ripple without complex feedback control. Finally, the hardware prototype with an input voltage of 90~264 VRMS, output voltage of 24~32 VDC, and constant output current of 700 mA/20 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 between 25.76% and 17.04% without electrolytic capacitor, and there is no visible flicker in the LED light output from 20% load to full load conditions. The power factor of the system is higher than 0.94, and the system also meets the IEC 61000-3-2 Class C standard requirements.

1 Introduction ...................................................................1
1.1 Background and Motivation....................................1
1.2 Organization................................................................6
2 Characteristics of LED and Drivers..........................7
2.1 Characteristics and Equivalent Circuits of LED.....7
2.2 Types of LED Drivers................................................10
2.2.1 Two-stage AC-DC Converter...............................10
2.2.2 Single-stage AC-DC Converter............................11
2.2.3 QR Flyback Converter............................................13
3 Operating Principles of the Proposed LED Driver....15
3.1 Single-stage AC-DC QR Flyback Converter with
the AC Current Ripple Eliminator.....................................15
4 Steady State Analysis and Parameter Design...........26
4.1 Flyback Converter......................................................26
4.2 AC Current Ripple Eliminator..................................29
4.2.1 Constant duty ratio control..............................30
4.2.2 PWM control........................................................36
4.2.3 Discussion of constant duty ratio control and PWM control...................................................................................43
5 Experimental Results of the Hardware Prototype...45
5.1 Specification of the Hardware Prototype.............45
5.2 Experimental Waveforms and Analysis.................47
5.3 Line Regulation Analysis...........................................49
5.3.1 Line regulation under different line frequencies ................................................................................................49
5.3.2 Line regulation under various output voltages ................................................................................................51
5.4 Load Regulation under Different Input Voltages ................................................................................................54
5.5 Hardware Prototype Parameters and Standard Compliance..........................................................................57
6 Conclusions and Future Works.....................................61
6.1 Conclusions...................................................................61
6.2 Future Works................................................................63
References.............................................................................64

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