LED的输出光通量、输入电功率、结温以及寿命之间互相影响、紧密联系。在设计、使用LED时需要综合考虑各个参数才能使LED工作在最佳状态。针对LED提出了光电热寿命理论，该理论揭示了LED的输出光通量、输入电功率、结温以及寿命这4个参数之间的内在联系。使用该理论可以建立LED寿命预测模型，找到LED的输出光通量和寿命之间的关系式，根据该关系式可以预测LED的寿命，评估LED的可靠性。由此可以找到合适的LED工作点，兼顾LED输出光通量和LED寿命，实现LED在全生命周期内输出光通量最大，从而达到优化LED工作状态的目的。

The photometric, electrical, thermal and life features of LEDs are highly dependent on each other. All these factors should be considered together in order to optimize the operating point of LEDs. A photo-electro-thermal-life theory about LEDs is presented. This theory shows the inner links among photometric, electrical, thermal and life features of a LED. Using this theory, one can build a life prediction model and find out the relationship between output luminous flux and lifetime of LED. Based on this relationship, one can predict the lifetime of a LED and find the proper operating point, at which the LED will generate the maximum amount of luminous flux in its total life cycle.