Browsing by Author "Uras, Umut Zeynep"

Now showing 1 - 3 of 3

Metadata only
Thermal and optical interaction of tightly packaged LEDs in automotive lighting applications
(2018-11-20) Uras, Umut Zeynep; Arık, Mehmet; Arık, Mehmet; Başol, Altuğ Melik; Demiroğlu, Cenk; Budaklı, M.; Şendur, Polat; Department of Mechanical Engineering; Uras, Umut Zeynep
This study aims to enhance the thermal management of an LED light engine for automotive exterior lighting with an advanced heat spreader. Although LEDs have many advantages, their applications require an accurate thermal management. To house driver electronics and LEDs in a typical automotive exterior lighting, conventionally FR4 based printed circuit board is usually used. Over the board, local hotspots are observed due to low thermal conductivity of FR4 based PCB and high heat flux caused by LEDs and electronics. LEDs in automotive back lighting units operated with different input power for position, stop and signal lights. Moreover, in some instances, these three lights perform simultaneously in the automobiles. Therefore, heat flux dissipation over LEDs and electronics become abundant making thermal performance of the FR4 board inadequate to diffuse this flux. Thus, in this study, an advanced heat spreader board technology was investigated and compared with the conventional FR4 based and Al metal core printed circuit boards. An experimental study was conducted via thermal imaging technique in order to inspect local hot spots. Also, an optical performance investigation for advanced heat spreader based LED light engine is conducted. Then, a numerical analysis is also performed in order to validate experimental results. According to experimental data, advanced heat spreader has performed 7.4% better thermal performance than Al metal core board and 25.8% FR4 based board. Besides, when advanced heat spreader board base used instead of FR4 board base, luminous efficacy can be improved by 25.9%. In addition, improving thermal spreading capability of PCBs is one of the alternative solution in order to distribute heat from source, efficiently. Various type of materials is investigated to improve thermal characteristics of PCBs. In this study, multilayer ceramic flex PCB is analyzed as alternative PCB solution to overcome thermal problems. To analyze thermal performance of the PCB, it is compared with that of FR4 flex PCB experimentally and computationally. While thermal performance degrades 36.5% when FR4 flex PCB is used, radiant flux and luminous flux of the LED light engine decrease by 13.3% and 14.6%, respectively. Besides, there is strong dependency between photometric, electrical and thermal properties of LEDs. Hence, while a lighting system is designed, thermal and electrical parameters of the system should be considered to achieve desired performance. Therefore, another aim of the study is to analyze dependency between photometric, electrical and thermal parameters of the FR4 LED light engine with FR4 flex PCB is analyzed. On the other hand, in recent years, paradigm of Internet of Things which will be effective in all areas of our lives is in the foreground and lighting systems with over 500 billion fixtures globally are seen as a great opportunity for a widespread application. In addition, automobiles may constitute a platform for IoT applications due to their current electronics system and mobility feature. Thus, in this study, a possible candidate automotive rear LED lighting system is evaluated in terms of thermal performance for new generation IoT added applications. Firstly, thermal performance of FR4 based LED engine is evaluated and it is modeled in a CFD program. Then, computational model is solved for different cases such as; 25%, 50% and 70% power addition to electronics to determine the adverse effects due to IOT power needs. Metal and advanced heat spreader substrate technologies are presented as solution to overcome thermal problems. While power consumption of electronic increases by 70%, maximum temperatures that is experienced on electronics increase by +38.4%. Maximum temperatures of amber LEDs increased by +12.5%, when temperature rise of +11.2% is experienced on red LEDs. As conventional FR4 substrate is not adequate for future electronic systems, advanced heat spreader board technology which consists of vapor chamber structure can be a possible substrate technology for new generation smart applications.
Metadata only
Thermal enhancement of an LED light engine for automotive exterior lighting with advanced heat spreader technology
(ASME, 2016) Uras, Umut Zeynep; Tamdoğan, Enes; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet; TAMDOĞAN, Enes; Uras, Umut Zeynep
In recent years, light emitting diodes (LEDs) have become an attractive technology for general and automotive illumination systems. LEDs have been preferable for automobile lighting due to its numerous advantages such as long life, low power consumption, optical control and light quality as well as robustness for high vibration. Thermal management is one of the main issues due to severe ambient conditions and compact volume. Conventionally, tightly packaged double sided FR4 based printed circuit boards are utilized for both driver electronics components and LEDs. In fact, this approach will be a leading trend for advanced Internet of Things (IOT) applications in near future. A series of numerical models are developed to determine the local temperature distribution on both sides of a light engine. Results showed that FR4 PCB has a temperature gradient of over 63°C while the maximum temperature is 105°C. This causes a significant degradation of lifetime and lumen extraction as many LEDs are recommended to be operated below 100°C. In addition to FR4, Aluminum metal core and vapor chamber based advanced heat spreader substrates are developed to obtain thermal impact on the substrate due to a wide range of thermal conductivity of three boards. To mimic real application, two special flex circuits are developed for LEDs and driver circuit. 10 red and 6 amber LEDs at one flex-PCB, and driver components are populated on the other flex-PCB are mounted. Both flex circuits are attached each side of the substrate. Experimental results showed that the local hotspots occurred at FR4 PCB due to low thermal conductivity. Later, a metal core printed circuit board is investigated to minimalize local hot spots. High conductivity metal core PCB showed a 19.9% improvement over FR4 based board. A further study has been performed with an advanced heat spreader based on vapor chamber technology. Results showed that a thermal enhancement of 7.4% and 25.8% over Al metal core and FR4 based boards with an advanced vapor chamber substrate.
Metadata only
Thermal performance of a light emitting diode light engine for a multipurpose automotive exterior lighting system with competing board technologies
(ASME, 2017-06-12) Uras, Umut Zeynep; Arık, Mehmet; Tamdoğan, Enes; Mechanical Engineering; ARIK, Mehmet; TAMDOĞAN, Enes; Uras, Umut Zeynep
In recent years, light emitting diodes (LEDs) have become an attractive technology for general and automotive illumination systems replacing old-fashioned incandescent and halogen systems. LEDs are preferable for automobile lighting applications due to its numerous advantages such as low power consumption and precise optical control. Although these solid state lighting (SSL) products offer unique advantages, thermal management is one of the main issues due to severe ambient conditions and compact volume. Conventionally, tightly packaged double-sided FR4-based printed circuit boards (PCBs) are utilized for both driver electronic components and LEDs. In fact, this approach will be a leading trend for advanced internet of things applications embedded LED systems in the near future. Therefore, automotive lighting systems are already facing with tight-packaging issues. To evaluate thermal issues, a hybrid study of experimental and computational models is developed to determine the local temperature distribution on both sides of a three-purpose automotive light engine for three different PCB approaches having different materials but the same geometry. Both results showed that FR4 PCB has a temperature gradient (TMaxBoard to TAmbient) of over 63 °C. Moreover, a number of local hotspots occurred over FR4 PCB due to low thermal conductivity. Later, a metal core PCB is investigated to abate local hot spots. A further study has been performed with an advanced heat spreader board based on vapor chamber technology. Results showed that a thermal enhancement of 7.4% and 25.8% over Al metal core and FR4-based boards with the advanced vapor chamber substrate is observed. In addition to superior thermal performance, a significant amount of lumen extraction in excess of 15% is measured, and a higher reliability rate is expected.