在現今LED調光方法中，絕大多數採用的是PWM調光，即線性調光，透過其導通時間的長短來改變平均電流大小，然而大多數LED的照度‐電流曲線並非線性，在順向導通電流越小時，照度對電流的比值會越大，隨著電流上升逐漸減小。因此，在此調光方法下，無法達到實際的照度。
　　本論文提出了兩種調光方法分別是變動電流檢測電阻值及變動調光訊號電壓準位，用以改善LED光轉換效率，並提供了計算最佳控制點電流值之方式。製作了一個115 W的LED驅動電路並透過數位訊號控制器來實現所提出之調光方法，實驗結果涵蓋了照度‐功率曲線以及CIE1976和CIE1931色彩空間圖的量測。將這兩種調光方法與PWM調光做比較，在照度相同的情況下，驅動電路輸出功率分別減少了17.08%和13.17%；在驅動電路輸出功率相同的情況下，照度分別提升了13.66%和11.17%，以上的數據皆為平均值。

PWM dimming method has been widely used for driving LEDs, and the average current through LEDs can be linearly controlled by adjusting the duty cycle of the dimming signal. However, most illuminance-current characteristic curve of LEDs is nonlinear. The smaller the current is, the larger the ratio of illuminance to current is, and will gradually decrease as the current increases. Hence, optimal overall electrical-to-light conversion efficiency cannot be fully achieved using PWM dimming method.
In order to improve the luminous efficacy of LEDs, two dimming methods are proposed which are varied current sensing resistance method and varied dimming voltage method. The determination of the optimal transition points is first investigated in this thesis. Next, an 115W LED driver is constructed and the proposed dimming methods are realized using dsPIC33FJ16GS502 digital signal controller (DSC). Finally, illuminance-power curves, CIE1976 and CIE1931 chromaticity diagrams are presented and discussed with the aid of experimental results. Compared with PWM dimming, the average output power reduction of the LED driver under the same illuminance are 17.08% and 13.17%, respectively; the average illuminance improvement under the same output power are 13.66% and 11.17%, respectively.

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