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1、南京航空航天大学 硕士学位论文 无电解电容的发光二极管照明AC/DC电源的研究 姓名：顾琳琳 申请学位级别：硕士 专业：电力电子与电力传动 指导教师：阮新波 20090301 南京航空航天大学硕士学位论文 I 摘 要 LED 照明电源是一个 PFC 变换器，将输入交流电压变换为稳定的直流电压，供给 LED 驱 动器。由于 LED 照明电源的输入功率是脉动的，而输出功率是平直的，因此需要一个储能电容 来平衡脉动的输入功率和恒定的输出功率。一般储能电容容量较大，通常选用电解电容，但是 电解电容的寿命只有几千小时，远远短于 LED 的寿命（50,000 小时），这使得 LED 照明电源 与 LED
2、的长寿命不匹配。本文的研究目的是在满足输入功率因数不低于 0.9 的前提下，提出减 小储能电容容量的方法，用薄膜电容来替代电解电容，以延长 LED 照明电源的使用寿命。 本文提出增大储能电容电压纹波的方法来大幅度减小储能电容容量，这样可以采用薄膜电 容替代电解电容。为了保证 Boost PFC 变换器的正常工作，本文推导了储能电容电压最大值、 最小值和平均值与储能电容容量大小的关系，并给出储能电容容量的选取原则。为了进一步减 小储能电容，本文分析 PFC 变换器的输入功率脉动与输入功率因数之间的关系，提出在输入电 流中注入适量三次谐波的方法。根据照明电源的标准，输入功率因数不能低于 0.9，因
3、此注入三 次谐波的幅值不得超过基波的 48.4%，此时储能电容容量可以减小到输入功率因数为 1 时的 65.6%。论文还给出三次谐波注入的具体实现方法。 基于上述减小储能电容容量的方法，本文提出一种无电解电容的两级式 LED 照明电源方 案，其前级为 Boost PFC 变换器，后级为 Flyback 变换器，它们均工作在电流临界连续模式。 论文讨论该方案的主电路参数设计，给出 Boost PFC 变换器和 Flyback 变换器的小信号模型， 并进行闭环设计。 本文完成一台 60W 原理样机进行实验验证。实验结果表明本文所提出的方法是可行的。 关键词：关键词： LED 照明，电源，功率因数校
4、正，谐波注入，电压纹波 无电解电容的发光二极管照明 AC/DC 电源的研究 II ABSTRACT The power supply for LED lighting, which converts a commercial ac voltage to a steady dc voltage, should have the function of power factor correction (PFC) to comply the requirements of the regulations such as Energy Star. In a PFC converter, the inp
5、ut power is pulsating while the output power is constant, therefore a storage capacitor with large value is required to balance the instantaneous power difference, and electrolytic capacitor is usually used as the storage capacitor. However, it is remarkable that the lifetime of electrolytic capacit
6、or is only several thousand hours, which is much lower than the lifetime of LED (longer than 50,000 hours), so electrolytic capacitor is the obstacle for the match of lifetime of the power supply and LED. The objective of this thesis is to propose methods to reduce the storage capacitor significantl
7、y at the precondition that the input power factor is higher than 0.9, thus film capacitor can be adopted instead of electrolytic capacitor to prolong the lifetime of the power supply for LED lighting. In this thesis, the voltage ripple of the storage capacitor is purposely increased to significantly
8、 reduce the value of the storage capacitor, so film capacitor can be adopted to replace electrolytic capacitor, and a long lifetime of the power supply is achieved. The maximum voltage, minimum voltage and average voltage of the storage capacitor as a function of the value of the storage capacitor a
9、re derived so as to ensure Boost PFC converter operates normally in the whole input voltage range. The determination of the value of the storage capacitor is also discussed. In order to further reduce the value of the storage capacitor, the relationship between the pulsation of the input power and t
10、he input power factor is analyzed, and injecting the 3rd harmonic current to the input current is proposed to reduce the pulsation of the input power. While ensuring the input power factor be higher than 0.9, the amplitude of the injected 3rd harmonic current is 0.484 of the fundamental wave current
11、, and the storage capacitor can be reduced to 65.6% of that with input power factor of 1.0. The control method of 3rd harmonic injection is also presented in this thesis. A two-stage power supply for LED lighting without electrolytic capacitor is proposed, including a Boost PFC converter and a Flyba
12、ck converter. Both of the converters operate in discontinuous current mode-boundary to achieve high power factor and avoid the reverse recovery of the rectifier diodes. The parameter design of the power stage of the two converters is discussed. The small signal models of the two converters are deriv
13、ed, and based on which, the closed loops are designed. A 60W prototype has been built and tested in the lab, and the experimental results verify the 南京航空航天大学硕士学位论文 III proposed methods can significantly reduce storage capacitor. Key Words: LED lighting; power supply; power factor correction; harmonic current injection; voltage ripple. 无电解电容的发光二极管照明 AC/DC 电源的研究 VIII 图表清单 图 1.1 飞利浦公司生产的大功率白光 LED.2 图 1.2 LED 的一些应用实例.2 图 1.3 LED 的特性曲线.3 图 1.4 单级结构的 LED 照明驱动电源.4 图 1.5 National Semiconductor 生产的 LED 驱动芯片 LM3402.4 图 1.6 两级式结构的 LED 照明驱动电源.5 图 1.7 两级式 PFC 变换器.5 图 1.8 单级式 PFC 变换器.
