LED照明系统高可靠运行关键技术的研究

With the advantages of high efficiency and long lifetime, the Light-Emitting Diode (LED) lighting is profitable to save the energy consumption and mitigate the environmental pollution. However, the customer experiences may be different and some of the LED lamps can fail in a considerable time ahead of the claimed life, which increases the running and maintenance costs. To solve it, this project will firstly analyze the key parameters which may degrade LED chips, capacitors and switching components and so on. Then the component-level models of lifetime and reliability will be proposed to predict the lifetime and reliability of those key components. The multi-physics field based analysis is proposed to predict the LED junction temperature accurately. Due to the effect of the thermal coupling to temperature distribution, an improved thermal model will be analyzed to facilitate the topology-level models for lifetime and reliability. Because the lifetime of the whole LED lighting system is affected by many parameters with different time scales, the multiple time scale models for the LED lighting system are proposed to estimate the system-level lifetime and reliability. The LED lighting systems usually work in the different locations and variable environmental conditions, and an accurate lifetime prediction method will be proposed to estimate the real lifetime and reliability information of the LED lighting system in field operation. With these models and information, the current driving schemes and thermal control solutions will be proposed to improve the lifetime and reliability of the whole LED lighting system. All above technologies will make the whole LED lighting system more efficient, durable and reliable and guarantee the energy saving of LED lighting system.

LED照明系统具有效率高、寿命长等优点，对实现节能减排和缓解环境污染有重要意义。但目前LED照明产品的寿命和可靠性不尽满意，LED照明产品经常在标称寿命前失效，无法高可靠运行，增加能源损耗和运行成本。本项目将针对此问题，系统研究影响LED芯片、驱动器电容和功率开关等关键器件寿命和可靠性的因素，建立器件级寿命和可靠性模型，提出多物理场耦合的LED结温预测方法；研究热耦合对LED光源、驱动器寿命和可靠性的影响，提出基于热耦合作用的改进型热网络模型，从而建立拓扑级寿命和可靠性模型；研究不同时间尺度下的系统光-电-热模型，建立不同时间尺度的系统级寿命和可靠性模型；提出变化工况下寿命和可靠性预测方法。通过以上研究准确预测出不同应用场合、不同运行工况下的LED照明系统真实的寿命和可靠性，并提出有效的电流控制方案和热管理方案来提高其寿命和可靠性，从而真正实现高效率、长寿命、高可靠运行的LED照明系统。

推广高效、耐久、节能的LED照明工程对实现节能减排有重要意义。根据《中国逐步淘汰白炽灯路线图》，在十三五期间我国已基本实现LED灯全面取代能耗高的白炽灯。但在实际应用中，大部分LED照明产品并未真正实现标称的高发光效率，以及长达十万小时的工作时间。因此通过本项目的研究，得到以下成果：.① 提出基于联合仿真和测量的LED宽禁带半导体器件寿命和可靠性建模方法。揭示了影响LED光源寿命和可靠性的关键因素为LED芯片内部PN结温度，且结温受芯片材料、封装工艺、环境温度、工作电流、散热条件等影响，涉及光-电-热多物理场、多学科交叉、多时间尺度等能量转换，难以直接测量和准确预估。候选人所提出的基于联合仿真和测量的寿命和可靠性建模方法，可解决LED在不同运行条件下的寿命和可靠性难以预测的技术难题，填补理论研究的空白，指导LED优化驱动和散热设计。对SiC、GaN等新一代宽禁带半导体器件的可靠性研究，亦可提供重要参考。.② 首次提出以无线供电方式为LED提供恒流源驱动。基于无线传能中最基本的串串结构，首次提出可利用其与负载无关的恒流工作点特性，实现LED所需的恒流驱动，从而解决了驱动器和光源热耦合的技术难题，降低了LED结温，提高了寿命和可靠性。该研究亦适用于其他恒流源驱动型负载的无线供电技术，从而带动电动汽车、轨道交通、手机等领域无线充电的相关研究。.③ 提出高效的LED驱动架构和无电解电容方案。LED为低压直流源型器件，提出非整数级联型驱动构架，大部分功率通过单级直接供电给LED，解决了从交流电网供电带来的多级变换器效率低、体积大、成本高的技术难题。针对LED需要滤除二倍工频功率纹波的要求，提出了功率解耦电路，避免使用寿命短的大电解电容，提高驱动和整个系统的寿命和可靠性。解决了LED照明系统由电解电容失效而提前熄灭的技术难题。以上技术可全面提升LED驱动器的效率和可靠性。.