實用led熱設計

　　添加一個簡單的熱反饋保護電路將給設計師安心，并保證在所有操作條件和溫度下LED壽命長。

　　在過去的幾年中，高亮度發光二極管（LED）已從一個利基產品，作為一個昂貴的設計師聚光燈到一個有用的通用燈，系統效率超過100流明/瓦特和壽命超過50000小時，極大地發展。

　　然而，大功率LED技術的引入推動了熱管理問題回到照明設計的前沿。像所有的半導體一樣，LED也不能太熱，否則它們的長壽將受到不利影響。在50000℃時，連接溫度為25°C的LED僅能存活175秒，連接溫度為125°C的一半，LED僅能存活100小時。

　　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：