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Spectral optimization of the color temperature tunable white light-emitting diode (LED) cluster consisting of direct-emission blue and red LEDs and a diphosphor conversion LED

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Abstract

The correlated color temperature (CCT) tunable white-light LED cluster, which consists of direct-emission blue and red LEDs as well as phosphor-conversion (PC) LEDs packaged by combining green and orange phosphors with a blue LED die, has been obtained by nonlinear program for maximizing luminous efficacy (LE) of radiation (LER) under conditions of both color rendering index (CRI) and special CRI of R9 for strong red above 90 at CCTs of 2700 K to 6500 K. The optimal peak wavelengths of blue LED, red LED, blue LED die, green and orange phosphors are 465 nm, 628 nm, 452 nm, 530 nm and 586 nm, respectively. The real CCT tunable PC/red/blue LED cluster with CRIs of 90~96, R9s of 90~96, CQSs of 89~94, LERs of 303~358 lm/W, and LEs of 105~119 lm/W has been realized at CCTs of 2722 K to 6464 K. The deviation of the peak wavelength should be less than ± 5 nm for blue LED die, ± 1 nm for red LED, and ± 2 nm for blue LED to achieve the PC/R/B LED cluster with high optical performance.

©2012 Optical Society of America

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Figures (12)

Fig. 1
Fig. 1 Optimal and real relative SPDs of PC, red and blue LEDs
Fig. 2
Fig. 2 The PC/R/B LED cluster provides a triangular color gamut that encompasses the Planckian locus from 2222 K to 100000 K, so it is possible to achieve CCT tunability. Also showing the chromaticities of real PC/R/B LED cluster at CCTs of 2722 K, 3040 K, 3514 K, 4024 K, 4574 K, 4968 K, 5719 K and 6464 K.
Fig. 3
Fig. 3 Measured SPDs of the real PC/R/B LED cluster at different CCTs
Fig. 4
Fig. 4 Changes in CRI of the PC/R/B LED cluster caused by the peak wavelength shift of blue LED die
Fig. 5
Fig. 5 Changes in R9 of the PC/R/B LED cluster caused by the peak wavelength shift of blue LED die
Fig. 6
Fig. 6 Changes in CCT of the PC/R/B LED cluster caused by the peak wavelength shift of blue LED die
Fig. 7
Fig. 7 Changes in CRI of the PC/R/B LED cluster caused by the peak wavelength shift of red LED
Fig. 8
Fig. 8 Changes in R9 of the PC/R/B LED cluster caused by the peak wavelength shift of red LED
Fig. 9
Fig. 9 Changes in CCT of the PC/R/B LED cluster caused by the peak wavelength shift of red LED
Fig. 10
Fig. 10 Changes in CRI of the PC/R/B LED cluster caused by the peak wavelength shift of blue LED
Fig. 11
Fig. 11 Changes in R9 of PC/R/B LED cluster caused by the peak wavelength shift of blue LED
Fig. 12
Fig. 12 Changes in CCT of the PC/R/B LED cluster caused by the peak wavelength shift of blue LED

Tables (2)

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Table 1 CRI, R9, CQS and LER of the optimal PC/R/B LED cluster at CCTs of 2700 K to 6500 K.

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Table 2 Color rendering property and luminous efficacy of the real PC/R/B LED cluster at Ta = 25°C according to the predicted drive current (IF) of each LED at different CCTs.

Equations (3)

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S PC/R/B (λ)= k PC S PC (λ, λ b , λ g , λ or )+ k R S R (λ, λ R )+ k B S(λ, λ B )
S PC (λ, λ b , λ g , λ or )= q b S b (λ, λ b )+ q g S g (λ, λ g )+ q or S or (λ, λ or )
F( λ b , λ g , λ or , λ R , λ B , q b , q g , q or )= i=1 8 LE R i (i=1,2,3 ,8) (under conditions of CRI i 90 and R9 i 90 with dC0.0054)
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