实用led热设计

　　实用led热设计

　　添加一个简单的热反馈保护电路将给设计师安心，并保证在所有操作条件和温度下LED寿命长。

　　在过去的几年中，高亮度发光二极管（LED）已从一个利基产品，作为一个昂贵的设计师聚光灯到一个有用的通用灯，系统效率超过100流明/瓦特和寿命超过50000小时，极大地发展。

　　然而，大功率LED技术的引入推动了热管理问题回到照明设计的前沿。像所有的半导体一样，LED也不能太热，否则它们的长寿将受到不利影响。在50000℃时，连接温度为25°C的LED仅能存活175秒，连接温度为125°C的一半，LED仅能存活100小时。

　　Although the efficiency of a high-power LED is around six times better than a standard incandescent light bulb， a significant amount of the electrical energy flowing through the device is still converted into heat. Whereas the waste heat from an Edison bulb is mostly radiated away as infrared energy， the waste heat from an LED must be conducted away through a heat sink. Thermal management and the consideration of the effects of high environmental temperatures must thus be addressed right at the start of the design phase of a solid state lighting source.

　　The factors affecting the effectiveness of a heat sink are the temperature difference between the heat source and ambient， the amount of heat generated （LED power）， and the thermal resistance. The relationship of the factors can be expressed as an equation：