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Multispectral mixing scheme for LED clusters with extended operational temperature window

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Abstract

LEDs have changed the concept of illumination not only in an expectation of the highest electroluminance efficiency but also in tremendous chances for smart lighting applications. With a cluster mixing, many studies were addressed to strategically manipulate the chromaticity point, system efficiency and color rendering performance according to different operational purposes. In this paper, we add an additional thermal function to extend the operational thermal window of a pentachromatic R/G/B/A/CW light engine over a chromaticity from 2800K to 8000K. The proposed model is experimentally validated to offer a full operable range in ambient temperature (Ta = 10° to 100°C) associated with high color quality scale (above 85 points) as well as high luminous efficiency (above 100 lm/watt).

©2012 Optical Society of America

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Figures (5)

Fig. 1
Fig. 1 The illustration of double Gaussian model for green and phosphor LED spectra at Tj = 25°C and IDC = 350mA respectively. For the phosphor-converted LEDs, the blue and fluorescence components should be individually considered, thus decomposed into two double Gaussian functions GB + GB’ and GF + GF’, respectively. The numerical model Eqs. (3)(7) ensure a good approximation at arbitrary junction temperature Tj and drive current IDC.
Fig. 2
Fig. 2 The power spectra of red (λR: 625nm, ΔλR: 20nm), green (λG: 523nm, ΔλG: 33nm), blue (λB: 465nm, ΔλB: 25nm), amber (λA: 587nm, ΔλA: 18nm) and cool-white LEDs at Ta of 10°C with IDC of 350mA. The upper right figure shows a real-field test designed for CT = 5000K and the lower right one shows the utilized LEDs attached on the temperature controllable fixture respectively.
Fig. 3
Fig. 3 The temperature dependence of spectra designed for CT = 3200K, 4600K, 6200K, and 7400K at Ta = 50°C. The chromaticity point shifts toward higher color temperature with the raise of Ta owing to the dramatic deterioration in LEs of the red and amber LEDs.
Fig. 4
Fig. 4 The temperature dependence of LE for pentachromatic LEDs. When Ta is varied from 10 °C to 100 °C, LEs of amber and red AlInGaP LEDs decrease to 23% and 46% of that at 10 °C while LEs of InGaP LEDs are insensitive to temperature variation.
Fig. 5
Fig. 5 The LE contour of the pentachromatic LEDs cluster is performed under the predefined requirements (CQS > 85 points, lighting level = 100 lm and Δxy < 0.01). When the LE = 100 lm/W is selected as the minimum efficiency boundary, a full operation range for ambient temperature can be obtained for CT > 5200K.

Tables (1)

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Table 1 The Comparison of CQS, LE, Output Spectral Power P, Correlated Color Temperature CCT, Color Temperature CT and the Input Power Ratio Pin under Ta = 10°C, 50°C and 100°C

Equations (11)

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T j T 2 T 1 V f ( T 2 ) V f ( T 1 ) [ V f V f ( T 1 )]+ T 1
R t = T j T a P e Φ
S ˜ =G+G'
g mn = p m exp{ [ λ n ( λ 0 ) m ] 2 /Δ λ m 2 }
argmin[ | s m s ˜ m | 2 , { p m , ( λ 0 ) m , Δ λ m , p ' m , ( λ 0 ') m , Δλ ' m }]
ln(p)= M p c p , λ 0 = M λ c λ , and ln(Δλ)= M Δλ c Δλ
S ˜ (λ)=G+G' =exp[ m p c p (λ m λ c λ ) 2 /exp ( m Δλ c Δλ ) 2 ] +exp[ m p c p ' (λ m λ c λ ') 2 /exp ( m Δλ c Δλ ') 2 ]
S ˜ W (λ)={ G B + G B ', for λ < λ BF G F + G F ', for λ> λ BF
ε ˜ =A S ˜ T l
ε ˜ = C T i DC
f=w×CQS+(1w)×LE, subject to w[0,1]
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