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High thermal stability of correlated color temperature using current compensation in hybrid warm white high-voltage LEDs

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Abstract

This study experimentally and numerically examines the correlated color temperature (CCT) stability issue for hybrid warm white high-voltage light-emitting diodes (HV-LEDs) by using a current compensation method. This method could efficiently maintain the CCT stability factor at approximately 1.0 and yield greater color uniformity with Δu'v' values ranging from 0.017 to 0.003 in CIE 1976 chromaticity coordinates. The simulation results show that the red chip intensity drop is the primary cause of CCT instability in the hybrid warm white system when the temperature increases. Therefore, Furthermore, results indicate that the relative lumen drop improves from 21% to 15% by using a current compensation method.

©2013 Optical Society of America

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Figures (5)

Fig. 1
Fig. 1 Temperature-dependent emission spectra of the hybrid warm white HV-LEDs. The inset shows the sample for the hybrid warm white HV-LEDs.
Fig. 2
Fig. 2 (a) The simulation spectra with different peak wavelengths of red chip. The inset shows the simulation results on CCT with different peak wavelength of red chip (b) The simulation spectrums with different red chip intensity. The inset shows the simulation result on CCT with different red chip intensity.
Fig. 3
Fig. 3 The CCT Stability Factor of with and without current compensation at different ambient temperature
Fig. 4
Fig. 4 (a) The relative lumen drop (b) luminous efficiency with and without current compensation at different ambient temperature
Fig. 5
Fig. 5 (a) CIE 1976 chromaticity indices versus various ambient temperatures with and without current compensation (b) Delta Δ u ' v ' of the two samples at various ambient temperatures.

Tables (2)

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Table 1 Peak wavelength and intensity drop at each temperature

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Table 2 The compensated current in red chip at different ambient temperatures

Equations (3)

Equations on this page are rendered with MathJax. Learn more.

u ' = 4 x / ( 2 x + 12 y + 3 )
v ' = 9 y / ( 2 x + 12 y + 3 )
Δ u ' v ' = ( Δ u ' ) 2 + ( Δ v ' ) 2
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