Thermal and Optical Characterization of White and Blue Multi-Chip LED Light Engines

Cengiz, Ceren; Azarifar, Mohammad; Arık, Mehmet

doi:10.1109/itherm51669.2021.9503203

Cited by 5 publications

(6 citation statements)

References 24 publications

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“…In their analysis, a comparison of the corrected IR measurements and FVM showed an up to 30 °C temperature difference, which reveals that surface temperature and T j are not equal to each other. Based on the forward voltage verified thermal characterizations conducted by Cengiz et al [ 96 ], a similar emissivity value of 0.9 for the phosphor-converted (pc) LED with a molded lens was found to be an accurate calibration for IR imaging of the chip. In another study, Ozluk et al [ 115 ] studied the effect of the molded lens on the T j of the green LED by examining thermal and optical properties after the successful removal of the lens from the chip.…”

Section: Optical Temperature Probing Methodssupporting

confidence: 58%

“…However, the studied surface should be exposed so that temperature probing can be utilized based on reflection, deflection, interference, fluorescence, birefringence, absorption, or thermal emission optical phenomena [ 95 ]. In the case of LEDs, the device cannot be probed with secondary optics due to its determining thermal effect on T j (refer to Figure 1 ) [ 96 ]. During the measurements, excitation, detection, or the reference light beam is generally adopted, and variations in light properties, including amplitude, phase, polarization, and frequency are recorded for the corresponding temperature evaluation.…”

Section: Optical Temperature Probing Methodsmentioning

confidence: 99%

“…At low temperatures, deviation from the constant voltage coefficient of temperature can be explained by internal series resistance [ 184 ]. However, at low pulse durations, which ensures no T j rise [ 63 ] and falls into the exponential current interval (e.g., 1 mA), numerous perfectly linear T j – V f were reported in the literature [ 64 , 82 , 94 , 96 , 115 , 129 , 164 , 182 , 195 , 196 ].…”

Section: Temperature Sensitive Electrical Parameters (Tseps)mentioning

confidence: 99%

“…Even though the isothermal condition can be more accurate at temperatures near to the room temperature, heat dissipation from the oven and air motion inside the oven increases temperature fluctuations, and thermal resistance between the calibration thermocouples and T j increases. To ensure pulse current temperature is equal to the T j , an oven arrangement as configured in the EVAtherm system can be used [ 29 , 96 , 115 , 129 , 181 , 210 ] in which LEDs are placed in the middle of a thermally-controlled oven with no direct contact between the heater-embedded walls. In this configuration, several thermocouples record the air temperature and PCB to increase the speed and accuracy of the isothermal condition.…”

Section: Temperature Sensitive Electrical Parameters (Tseps)mentioning

confidence: 99%

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A Critical Review on the Junction Temperature Measurement of Light Emitting Diodes

2022

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In the new age of illumination, light emitting diodes (LEDs) have been proven to be the most efficient alternative to conventional light sources. Yet, in comparison to other lighting systems, LEDs operate at low temperatures while junction temperature (Tj) is is among the main factors dictating their lifespan, reliability, and performance. This indicates that accurate measurement of LED temperature is of great importance to better understand the thermal effects over a system and improve performance. Over the years, various Tj measurement techniques have been developed, and existing methods have been improved in many ways with technological and scientific advancements. Correspondingly, in order to address the governing phenomena, benefits, drawbacks, possibilities, and applications, a wide range of measurement techniques and systems are covered. This paper comprises a large number of published studies on junction temperature measurement approaches for LEDs, and a summary of the experimental parameters employed in the literature are given as a reference. In addition, some of the corrections noted in non-ideal thermal calibration processes are discussed and presented. Finally, a comparison between methods will provide the readers a better insight into the topic and direction for future research.

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Section: Optical Temperature Probing Methodssupporting

confidence: 58%

Section: Optical Temperature Probing Methodsmentioning

confidence: 99%

Section: Temperature Sensitive Electrical Parameters (Tseps)mentioning

confidence: 99%

Section: Temperature Sensitive Electrical Parameters (Tseps)mentioning

confidence: 99%

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A Critical Review on the Junction Temperature Measurement of Light Emitting Diodes

2022

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“…Based on the temperature dependent response of forward voltage (V f ) of semiconductor devices, FVM is a common non-contacting T j measurement method [28,29]. In this method the temperature coefficient of voltage is known as the k factor (i.e.…”

Section: Fvm a Reconsideration Of The Conventional Experimental Methodsmentioning

confidence: 99%

Dynamic opto-electro-thermal characterization of solid state lighting devices: measuring the power conversion efficiency at high current densities

Azarifar¹,

Cengiz²,

Arık³

2022

J. Phys. D: Appl. Phys.

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Solid state lighting devices with high power densities require accurate characterization, as the rise of chip temperature impacts its optical, electrical, and lifetime characteristics. A detailed experimental study is performed in order to analyze opto-electro-thermal behavior as new high-power devices like laser diodes are becoming of interest. The outline of this article was inspired by two major issues identified in previous experimental approaches. First, there is some debate in the literature about the linearity of the temperature coefficient of the forward voltage. Second, there is a limited number of experimental reports on the temperature dependence of power conversion efficiency. We have shown that prior variations are the result of a diversity in the selection of electrical parameters during thermal calibrations, as both linear and non-linear relationships for temperature coefficient of voltage can be obtained. On the other hand, it was discovered that report scarcity for temperature-dependent studies can be related to the use of passive approaches for temperature-dependent measurements. In temperature-controlled environments, short pulses with high current densities may not ensure the thermal equilibrium of the device under test due to small thermal capacitance. This issue, as well as the lengthy process of passive measurements can be addressed by implementing a dynamic measurement method presented in this study. Finally, linear power conversion efficiency trends with junction temperature are demonstrated for both blue LEDs and LDs at high current densities.

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Effect of Phase Change Materials on the Optical Path of LEDs for Opto-Thermal Enhancement

Azarifar

Arık

Xie

et al. 2023

IEEE Trans. Electron Devices

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Thermal and Optical Characterization of White and Blue Multi-Chip LED Light Engines

Cited by 5 publications

References 24 publications

A Critical Review on the Junction Temperature Measurement of Light Emitting Diodes

A Critical Review on the Junction Temperature Measurement of Light Emitting Diodes

Dynamic opto-electro-thermal characterization of solid state lighting devices: measuring the power conversion efficiency at high current densities

Effect of Phase Change Materials on the Optical Path of LEDs for Opto-Thermal Enhancement

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