現今發光二極體(Light-Emitting Diode, LED)照明為了避免人眼因視覺暫留而感覺到閃爍，一般會將頻率操作於100 Hz至400 Hz之間，但攝影設備比人眼對閃爍更敏感，因此針對高端攝影應用有必要進一步提高調光頻率。另一方面，傳統常用的數位PWM調光為線性調光，其並非根據LED的相對照度‐電流特性曲線進行調光，因此在光轉換效率上無法達到原特性曲線所能提供之最大效能。
本論文研製一250 W無輸出電容LED分流高頻調光驅動電路雛型，並據此實現本文所提出的變動LED順向導通電流調光方法。與傳統PWM調光相比較，所提系統在低調光命令下，驅動電路效率可達81.4 %；平均效率提升3.58 %。在光電轉換效率上，相同照度的情況下，驅動電路輸出功率平均減少14.28 %；在驅動電路輸出功率相同的情況下，照度平均提升了11.47 %。在相同調光命令下本文所提方法相較於PWM調光法，相對色溫（Correlated Color Temperature, CCT）差值為6.9 K；色彩空間(CIE1931) (X,Y)座標軸差值分別為0.0006與0.0001；色彩空間(CIE1976) (u', v')座標軸差值分別為0.0065與0.0004；光學頻譜差1.11 nm；演色性指數（Color Rendering Index, CRI）差0.3；光色表現(TM-30)之色彩逼真度指數(Color Fidelity Index–Rf)和色彩飽和度指數(Color Gamut Score–Rg)分別差0.3與0.21，以上均為全段平均差值。

Today's Light-Emitting Diode (LED) lighting fixture generally operates at a frequency between 100 Hz and 400 Hz to prevent the human eye from feeling flicker, but photographic equipment is more sensitive to flicker than the human eye. Therefore, it is necessary to further increase the dimming frequency for high-end photography applications. On the other hand, the traditional commonly used digital PWM dimming is a linear dimming technique, which does not perform dimming according to the relative illuminance-current characteristic curve of the LED, so the luminous efficiency cannot reach the maximum efficiency that the original characteristic curve can provide.
In this thesis, a prototype of a 250 W LED high-frequency shunt dimming driving circuit without an output capacitor is developed, and based on this, the variable LED forward current dimming method proposed in this study is realized. Compared with the traditional PWM dimming, the efficiency of the driving circuit of the proposed system can reach 81.4 % under the low dimming command; the average efficiency is increased by 3.58 %. In terms of photoelectric conversion efficiency, the output power of the driving circuit is reduced by 14.28% on average under the same illuminance; when the output power of the driving circuit is the same, the illuminance is increased by 11.47% on average. Compared with the PWM dimming method under the same dimming command, the correlated color temperature (CCT) difference is 6.9 K; the color space (CIE1931) (X, Y) coordinate axis difference is 0.0006 and 0.0001 respectively; color space (CIE1976) (u', v') coordinate axis difference is 0.0065 and 0.0004 respectively; optical spectrum difference is 1.11 nm; color rendering index (CRI) difference is 0.3; The difference between Color Fidelity Index (Rf) and color gamut score (Rg) is 0.3 and 0.21 respectively, and the above data all are the averaged values of the whole segment.

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