Method for determining the junction temperature of alternating current light-emitting diodes

Hwu, Farn-Shiun; Sheu, Gwo Jiun; Lin, Ming Chang; Chen, Jyh-Cheng

doi:10.1049/iet-smt:20080096

Cited by 9 publications

(7 citation statements)

References 4 publications

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“…[1] Hwu et al developed a method based on potential drop across the pn-junction and estimated junction temperature by measuring the board temperature. [2] In this study, we developed an alternate method based on potential drop to measure the junction temperature and the thermal resistance of the AC LED package. In this method, a low reference current, 0.1 mA, having a pulse width of less than several milliseconds was applied at the zero-crossing point of the AC LED current waveform, and the corresponding voltage across the device was measured.…”

Section: Introductionmentioning

confidence: 99%

Estimating the junction temperature of AC LEDs

et al. 2010

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Light-emitting diodes operating on alternating current are gaining popularity in the LED industry, especially for lighting applications. Because junction temperature is a good predictor of LED performance, the availability of a method to accurately estimate the junction temperature of AC LEDs would be very useful. This study investigated a method in which a low reference current having a pulse width of less than several milliseconds was applied and the corresponding voltage across the device was measured and correlated to the junction temperature. Laboratory experiment data showed that the proposed method is a promising candidate for estimating AC LED junction temperature.

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Section: Introductionmentioning

confidence: 99%

Estimating the junction temperature of AC LEDs

et al. 2010

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“…Nowadays, LEDs driven by alternating current (ac) are receiving much attention due to their characteristics of high voltage (HV) and low current [38], [39], [43], [44]. They are also convenient to operate in an ac utility system.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Model for Studying Multimicrochip and Single-Chip LEDs With an Interdigitated Mesa Geometry

Hwu¹,

Sung

Chen

et al. 2013

IEEE Photonics J.

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A 3-D numerical model has been developed to investigate the transient thermal, electrical, and optical output performance of a single-chip light-emitting diode (LED) with an interdigitated mesa geometry under dc operation and a multimicrochip LED under either dc or full-wave operation. These two LED chips are fabricated on the same sapphire wafer. The junction temperature, the light output power, and the electroluminescence intensity of both LEDs are measured under dc to prove the results of the numerical simulations. The numerical simulation results are in good agreement with the experimental ones. The numerical results indicate that the multimicrochip LED under dc operation will demonstrate the best thermal and light output performance. Utilizing the input power considered in the present computation, the light output power for the multimicrochip LED, under either dc or full-wave operation, is raised continuously. On the other hand, the saturation of the light output is observed for the single-chip LED with interdigitated mesa geometry.

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“…The working principles of an ac LED are simple. Two sets of integrated LEDs are operated alternately at the positive and negative ac sine voltage to activate a periodic LED light [5,6]. The first ac micro-LEDs, consisting of several GaN LED chips, were fabricated on a single device by Ao et al [7].…”

Section: Introductionmentioning

confidence: 99%

“…Yen et al [8] invented a new ac LED structure that used a Wheatstone bridge circuit design to increase the optical power and improve device efficiency. The inclusion of a chip in a single ac LED device can eliminate the need for an ac-dc power converter, which leads to significant cost savings [5]. In addition, there are many other advantages to ac LEDs which can be integrated on a single chip, for example, increasing the energy utilization efficiency and reliability, and greater compactness [6].…”

Section: Introductionmentioning

confidence: 99%

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Method for measuring the mean junction temperature of alternating current light-emitting diodes

Hwu¹,

Yang

Chen

2011

Meas. Sci. Technol.

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A new technique is developed to measure the mean junction temperature during ac operation of alternating current light-emitting diodes (ac LEDs). In general, the ac electrical system supplies power at a fixed root-mean-square voltage (Vrms) but the current may vary during operation. The ac LED begins to function after the instantaneous voltage rises above a certain threshold. Both the theoretical and experimental results show that the threshold current under the threshold voltage input increases linearly with temperature. The mean temperature of the ac LED increases from the ambient temperature to a quasi-steady state under ac operation. The mean junction temperature at the quasi-steady state can be determined by using the linear temperature dependence of the threshold current and measuring the threshold currents at both the initial and quasi-steady states. After the junction temperature of an ac LED is determined, the thermal resistance from the junction to the lead frame can also be calculated by definition of the thermal resistance. The thermal resistance of an ac LED under ac operation, calculated by the present method, is very close to that measured under dc operation by the conventional forward voltage method.

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Method for determining the junction temperature of alternating current light-emitting diodes

Cited by 9 publications

References 4 publications

Estimating the junction temperature of AC LEDs

Estimating the junction temperature of AC LEDs

A Numerical Model for Studying Multimicrochip and Single-Chip LEDs With an Interdigitated Mesa Geometry

Method for measuring the mean junction temperature of alternating current light-emitting diodes

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