NTC熱敏電阻的LED照明系統過熱保護

　　高亮度、大功率LED（HBLED），像任何其他半導體器件產生的熱量。因為它是眾所周知的，高溫會縮短一個HBLED的壽命以及影響亮度、溫度控制要求。然而，為了控制溫度，設計師首先需要確定如何監測LED模具的溫度，這正是負溫度系數（NTC）熱敏電阻在LED照明系統中的作用。

　　不同的溫度傳感裝置，包括二極管，內置傳感器，正溫度系數（PTC）熱敏電阻，和電阻溫度檢測器（RTD），可用于LED照明應用的高亮度LED過熱保護。然而，NTC熱敏電阻是溫度的檢測和控制在這些應用中的首選，主要是因為他們的小封裝尺寸和極具吸引力的價格/性能比。

　　Comparing NTC thermistors to different temperature sensing solutions， Bruno Van Beneden， senior manager application support and design-in for Vishay Non-Linear Resistors， noted that diodes have low accuracy and limited temperature range; on-chip sensors have higher cost and limited temperature range; PTC thermistors have limited accuracy in a very limited temperature range， and RTDs are often too costly， with the possible exception of Ni thin-film RTDs.

　　The NTC thermistor‘s sensitivity to temperature changes， even in small increments， enables the device to be used in temperature sensing/control applications. These devices allow the LEDs to withstand higher current over temperature （via compensation） to enhance the LED’s lifetime. The current can be controlled according to ambient temperature by the NTC thermistor as shown in Fig. 1.