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High power LEDs are commonly known as energy saving lights that come with power ratings in the range of 500 mW to 10 Watts. They are based on technology intention to increase the luminescent efficiency and therefore can be used in almost every part of headlights with high-powered lights. They can be characterized on the basis of some parameters, such as forward voltage, intensity, wavelength, light and type.
The wavelength is measured in nanometers and is different for the three basic colors - red, blue and green. In setting these colors to different wavelengths we can obtain a wide range of exciting colors, too called colors of the rainbow. This is one of the electro-optical characteristics of an LED. Another important variation is the peak wavelength which suffers the least loss due to heat.
Each LED has two types of stresses - progress and regress. A light emitting diode can act as a resistor or a variable capacitor for reverse exchange and tensions on. Usually the reverse inclusion is the one with the higher voltage - up to 5V.
Some other vital parameters High power LEDs are the axial intensity and luminous flux. The light output is also known as light energy and is a measure of the power of light perception. The power is different at different wavelengths and luminous flux is calculated by adding the power values at all wavelengths. This is not the real power measurement, but is the measure of "useful energy" of an LED. Power dissipation is the amount of energy consumed by the LED. It is also known as the energy loss as heat. Another important feature is the color it emits. This color is what we see when the LED is lit. May be red, yellow, green, blue or white.
One of the major concerns about the design of high power LED is the amount of heat produced due to greater efficiency. High temperatures are not adequate for the proper functioning of the LED. They help lower your life and make it less effective. Thermal management in these LEDs is therefore a major concern, to make them more productive and more enduring. There is a critical temperature defined for each LED beyond which is permanently destroyed. The temperature of an LED is still changing over time and therefore it is important to keep a chart to record different temperature ratings against time.
There are three ways that heat can be discharged: conduction, convection and radiation. Traditional incandescent tungsten bulbs radiate energy as heat. LEDs, on the other hand, to conduct heat from one place to another, it takes a long time to be released into the atmosphere. The heat sink should by the use of a material that has high thermal conductivity. Aluminum and copper are two of the most used materials heat sink.
Radiation has less time than driving and therefore tungsten bulbs do not heat up very quickly. In the design of high power LED, adequate heat conduction is a main issue to address.
The temperature of an LED is directly related to its color. The white light produced by the combination of basic colors at their highest values and therefore the temperature is also higher in the case of white light. Some mechanism is needed to maintain constant color when changes temperature due to driving. A color sensor can be used for this purpose.
Wavelength voltage and brightness are also affected by temperature the junction of the diode and therefore must also be optimal for LED performance.
Positive feedback or "thermal runaway" is another problem related to the high temperature of the LED. This is a condition in which increased temperature causes the above parameters to change unexpectedly resulting in a further increase in temperature. This can be critical to the operation of an LED and should be avoided. This occurs when the LED is directed to consume more energy to produce the desired color. As a result, more heat is produced which increases the temperature and therefore the effect.
Thermal runaway is more pronounced when decreasing the junction temperature increase of light intensity and as a result of the color sensor reports there is insufficient light. This negative cycle goes on and on until the critical temperature is reached and the LED is destroyed. Thermal sensors can be used to correct this problem, constantly measuring the junction temperature and make that the system shuts down if there is an alarming condition.
However, in general, this mechanism is not advisable in these LEDs, because it makes them useless and clears its purpose. Other methods such as using natural graphite to spread the heat are more practical and useful. This material performs much of the heat dissipated by the LED and as a result of emissions into the atmosphere faster.
In conclusion, the most important thing to consider in a high power LED design is the selection of suitable materials that are not affected by the unexpected rise in temperature. This is to ensure that the works of LED at all times without having to close due the absence of one of its components. Efficient thermal management can increase the critical temperature of an LED as a result of its reliability and longevity has also been improved. These design decisions for the manufacturer to help the client save money and make the most of these powerful and efficient LEDs high power.
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Article Source: ArticlesBase.com - Thermal Characteristics of High Power Leds
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