數位式自動光功率控制系統設計及生醫應用

Digital Photo-Power Control System Design for Biomedical Applications

李家豪(Jia-Hao Li)

指導教授 ： 孫台平

國立暨南國際大學/科技學院/生物醫學科技研究所/碩士(2011年)

摘要

本研究以自動電流控制電路為基礎進行數位式自動功率控制系統之研究，其優點在於其電路中無需光偵測二極體感測發光亮來修正輸出電流大小，且當二極體發光元件電壓隨溫度變化時，我們可自動調整流經二極體發光元件之電流量，使發光功率量受溫度的影響減少，達成溫度補償之目的，在本研究中的數位式自動功率控制系統架構包含:儀表放大器、微控制器、數位類比轉換器、電壓電流轉換電路。
儀表放大器將位於發光二極體上之電壓變化取出，其輸出接至微控制器之一輸入端，微控制器用於量測發光二極體之導通電流與電壓並計算出直流消耗功率，因此當發光二極體輸出電壓隨溫度改變時可由微控制器得知其變化量；數位類比轉換器將微控制器運算結果轉換為類比電壓值輸出以控制溫度變化範圍。
電壓電流轉換電路由一運算放大器與金氧半場效電晶體所組成，使用負迴授之形式使輸入阻抗大、輸出阻抗也大之組態，電路輸入端為電壓形式－接至儀表放大器的輸出，輸出為電流形式，與二極體發光元件耦接，如此當二極體發光元件電壓隨溫度變化時，我們可自動調整流經二極體發光元件之電流量，使發光功率量受溫度的影響減少，達成溫度補償的目的。

關鍵字

發光二極體LED（light-emitting diode） ； 微控制器Microprocessor ； 自動功率控制電路（automatic electrical power control circuit）

並列摘要

In this research, design the digital photo-power control system based on automatic current control circuit (ACC) because of automatic current control circuit have advantage of that doesn’t require photodiode to sense light intensity and correct output current, and we can adjust the current flowing through the light-emitting diode when the voltages of light-emitting diode vary with temperature. It is reducing the dependence of light power of LED to the temperature that makes our purpose to compensate temperature is achieved. The digital photo-power control system in this research includes： an instrumentation amplifier, a microprocessor, a digital to analog convertor and the circuit for voltage to current.
A instrumentation amplifier which purpose is to obtain the changes in voltage across light-emitting diode. Then it connects to a port of microprocessor. A microprocessor is used for measuring the current flowing and voltage across light-emitting diode and calculating its power dissipation in DC. Thus, the amount of change, when the output voltages across light-emitting diode vary with the temperature, can be obtained using the microprocessor. A digital to analog convertor which its output terminal connects to input of voltage-to-current converter circuit and the input terminal connect to the microprocessor output terminals. So that the temperature range can be controlled by convert the signal from microprocessor output terminals.
A voltage-to-current converter circuit, which composes of op-amp and MOSFET transistor, uses a negative feedback mode which causes high input and output impedance configuration. The voltage-mode input terminal and current-mode output terminal are connected to the output of instrumentation amplifier and the light-emitting diode, respectively. In this way, we can adjust the current flowing through the light-emitting diode when the voltages of light-emitting diode vary with temperature. It is reducing the dependence of light power of LED to the temperature that makes our purpose to compensate temperature is achieved.

並列關鍵字

LED(light-emitting diode) ； microprocessor ； AEC(automatic electrical power control circuit)

參考文獻

[1] 鄭為修，“具溫度補償自動光功率迴授控制積體電路之設計”，國立暨南國際大學碩士論文，July 2007。

[2] 工商服務電子報, 經濟部工業局, http://www.moeaidb.gov.tw/external/ctlr?PRO=epaper.EpaperView&id=1919

[3] T10 LED Tube Lamp, Welland, http://www.welland.com.tw/LED/T5%20LED%20Tube%20Lamp/T5_9w_2ft.html

[4] R. Greenburg, “Consumer applications of power semiconductors,” Proceedings of the IEEE, Vol.55, 1426-1434, 1967.

[5] J. Mroczka, “Temperature stabilization of light-emitting diode radiation,” J. Phys. E, Sci. Instrum., vol.21, 306-309, 1988.