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Thermal Considerations
Thermal Considerations
Thermal Considerations
Temperature
To maximise the reliability and performance of LEDs, proper thermal management is essential. If the LED's maximum operating temperature is exceeded, light output and lumen maintenance decreases and as such the useful lamp life is shortened. Therefore it is essential that validation of an LED's temperature is undertaken by means of temperature measurements to ensure optimum performance.
In general, manufacturers define an LED's maximum operating temperature at the semiconductor level (Tj = T junction). To ensure this limit is not exceeded, temperature measurements are necessary. Although the critical temperature to measure is the junction temperature Tj, the inaccessibility of this point has led to the creation of an additional measurement – the Tc temperature.
This separate Tc temperature measurement point is chosen as such that it has a direct relation to the Tj junction temperature and must not exceed the speciied limit. If the measurement of this Tc temperature is below or equal to the speciied limit then the stated life and luminous lux of an LED will be achieved. Exceeding the limits set for Tc will negatively impact the initial product performance as well as its useful product life. All measurements must be performed by means of thermocouples that are correctly fixed to the Tc points.
Thermal management
Temperature and its control have a significant impact on the quality and lifespan of an LED. To ensure LEDs operate at their optimum capabilities, effective thermal management is essential.
The principal role of thermal management is to extract the heat from the LED module and dissipate it into the surrounding air. This can be done through conduction, convection and radiation and different approaches are being taken to this issue across the industry, with varying degrees of success.
Optimum thermal management is achieved when the number of thermal conductive interfaces between the LED and its heat sink are reduced and the thermal resistance between these interfaces is minimised. In addition, careful consideration needs to be given to the heat sink material, its surface area, geometry and roughness as well as the management of airlow around the LED as a whole.
Diagram 1 and 2: Heat from Halogen Lamp Verses LED in relation to Heat Sensitive Products and in realtion to distance from lit product
MEGAMAN®’s LED choice
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All MEGAMAN® LED light sources are based on multiple chip arrays on ceramic substrate. This choice has multiple benefits in terms of performance, size and thermal management of the product. Compared to Power LED solutions the LED array can be mounted directly, without the need for an additional PCB and the ceramic substrate has a very low thermal resistance. Both of these allow less thermal resistance between LED and heat sink and as such allows better heat conduction away from the LED. |
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MEGAMAN®’s unique geometry
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The majority of LED lamps on the market today incorporate exterior lenses with which to direct light output. However these tend to trap heat, meaning a larger heat sink is required. Thanks to innovative product development from MEGAMAN®, the company’s LED directional light sources do not use lenses but reflectors to direct the light output. The open style of MEGAMAN®’s LED reflectors allows more heat to escape from the lamp, enabling smaller heat sinks to be fitted and giving the lamp a smaller profile. |
 Diagram 3: Illustrates MEGAMAN®'s unique reflector technology |
Thermal Conductive Highway™
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MEGAMAN®’s patented Thermal Conductive Highway™ technology uses a unique design of ‘heat drain’ across the reflector to dissipate heat efficiently and prevent deterioration of the LED and other components. The technology also gives the lamps a longer life with lumen maintenance, resulting in 90% of initial lumens being available even at the end of the lamp life. Thanks to careful thermal management, MEGAMAN®'s LED Reflector Series combines the higher efficiency, lifetime, and reliability benefits of LEDs, with the light output levels of many conventional light sources. |
 Diagram 4: MEGAMAN®'s unique geometry allowing optimum thermal control with MEGAMAN® TCH Technology |
New display Opportunities
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Thanks to MEGAMAN®’s advanced thermal management technology, all of its LEDs can be positioned in areas not traditionally possible with hotter halogen equivalents. MEGAMAN® lamps can be placed close to the objects they are lighting, with no risk of heat, UV or IR degradation. This makes them ideal for sensitive display areas, such as food halls, museums or galleries. MEGAMAN® light sources can also be located in access areas close to the general public, due to their heat dissipation capabilities. |
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