LED電源驅動與保護控制技術之研究

Abstract

本研究主要探討高亮度LED照明燈具保護電路之設計，當LED瞬間損壞或環境溫度改變時可以透過控制器來調整電源供應器的輸出功率，避免LED發生功率過載現象或LED晶蕊溫度過高而導致LED的永久損壞。 此控制架構的受控廠為100W的LED照明燈具，由PIC微處理器設計控制器，採取定功率的驅動技術。首先對100W的LED照明燈具作系統識別，並經由實驗分析得到系統的動態響應模型後，以PI控制器設計，根據系統不同的敏感度及響應規格，求得最佳的控制參數使系統達到穩定。 電路保護方面，即時偵測負載端電壓的變化可判斷LED是否有損壞情形，並以系統診斷的概念防止誤判的狀況發生；也利用負載端電壓反推晶蕊溫度，若晶蕊溫度超過所設定之限定溫度，可調降輸出功率，防止晶蕊溫度過高而導致永久損壞。 實驗結果顯示，在環境溫度變化時，控制系統仍可維持固定的輸出功率，範圍在100W±2W；而保護電路設計方面，當瞬間損壞一排LED時經由系統診斷後可即時調整功率值，當環境溫度過高使晶蕊溫度超過85℃，可有效調整輸出功率進而降低晶蕊溫度，達到保護LED之目的。

The main purpose of this research is to investigate the protective circuit of the high power LED in order to prevent LED from being permanently damaged. During the abrupt breakdown of LED or the ambient temperature change, the controller will adjust the output power from the power supply to avoid the rise of the junction temperature of LED. High junction temperature may cause the permanent breakdown of LED easily. This plant of the control system is a 100W LED street light. The controller designed by PIC microprocessor maintains the output power stable. At first, the system dynamics model for a LED luminaire is constructed. The feedback control system using PI control is designed and analyzed according to stability criterion and simulating. At last, optimal parameters in the controller can be determined, and successfully stabilized the system. As for the protective circuit, the controller can detect the sudden breakdown and the junction temperature of LED through output voltage and then adjust the power output accordingly. The controller with system diagnosis can prevent the probability of misjudgments. Experimental results show that the control system can maintain the output power stably at 100W±2W in normal conditions even with the variation of surrounding temperature. Moreover, when one column of LED is damaged or when the junction temperature is too high, the controller can detect the situation and turn down the output power. This will avoid the overload of LED and light decay.