LED交流驅動之研究

Abstract

本研究目的在探討LED在交流、PWM驅動下，LED晶蕊溫度瞬間的變化是否超過其限制條件。因晶蕊溫度無法直接量測，因此欲取得精確的晶蕊溫度需藉由系統識別來建立LED燈具的模型，本研究採用脈衝驅動法來測量晶蕊溫度，測得LED燈具之接面溫度動態響應，並以Rake’s法識別LED動態模型。 在本文中分別對18W與100W LED燈具作系統識別。經由理論推導與動態實驗皆可證明LED接面溫度響應為四階系統，但簡化成分子分母同為一階系統亦可得到良好的近似。使用交流全波整流、交流半波整流、PWM、三角波等四種波形驅動LED燈具，分別模擬出晶蕊溫度瞬間的變化量。本研究將晶蕊溫度的極限值設定為80℃，由模擬結果可看出PWM驅動方式能承受較大的過電流，其次為三角波。而全波整流亦可承受 兩倍以上的變化而不會造成其晶蕊溫度過高的情況發生，半波整流則為模擬波形中最不良的驅動方式。

The purpose of this study to investigate the LED in the AC-driven, PWM driven, Triple driven, LED junction temperature changes in an instant whether over its restrictions. The method used to measure the pulse-driven junction temperature, and to identify LED dynamic model by Rake's law. Both theoretical and experimental analyses have shown that the thermal system dynamics model of the LED fixture is 4th-order with 3 zeros and can be further reduced to a first-order biproper system. The use of AC full-wave rectifier, AC half-wave rectifier, PWM, such as triangular-wave-driven were simulated LED junction temperature changes in an instant. This study will be junction temperature limit is set to 80℃. The results can be seen by the PWM-driven approach can withstand greater over-current, followed by the triangular wave. Full-wave rectifier can withstand more than twice the rms-current changes will not lead to its junction temperature is too high to happen, half-wave rectifier analog waveform is the most bad-driven approach.