LED Heat Sink Temperature Calculator

by / Monday, 12 May 2014 / Published in Company Blog
A hotspot LED is defined as a transition between – p and n-type semiconductor , which form the diode . This article uses an example to illustrate the application of lighting, how to calculate the junction temperature of the diode and determine whether it is likely to exceed the specified limit.
Calculation of the LED junction temperature
An LED converts electrical energy into light by recombination of charge carriers (electrons and holes ) in or near the LED junction ( Figure 1 ) . Unfortunately, even if the diodes are relatively effective , about 65 to 75 percent of the electrical energy not consumed heat generated in the light, the temperature of the chip.
LED Heat Sink Temperature Calculator
Figure 1: charge carriers combine at the junction of an LED to produce something light and lots of heat.
But how hot can achieve high brightness LED ? Tell us how you determine the junction temperature with a simple calculation.
Room temperature, the thermal resistance between the LED junction and the environment , and energy from the chip [ ¹ ]: The maximum junction temperature (Tj) with an input power reaches is determined by three factors .
To simplify the calculation , an ambient temperature ( Ta) of 23 degrees Celsius ( ° C ) is assumed . ( They note that the complete design calculation should be the worst case the maximum ambient temperature the indicator to consider the experience in normal operation. ) Lower ambient temperature , the junction temperature to decrease and the life of the LED . This makes LED lighting is a good choice for some applications, such as the windows of refrigerated foods .
Thermal resistance ( Rth ) is, as the increase in temperature of a component per unit power dissipation defined (° C / W). It is the inverse of thermal conductivity. Metals generally have low heat resistance and provide efficient heat sink while the air , plastic and wood are to be effective thermal conductors and insulators poor.
A simplified model of an LED lighting device may comprise two elements in series with the sum of each element Gesamtwärmewiderstandals . The first element is the LED assembly of the junction ( J ) to the point ( SP ) on the solder substrate ( Rth j -SP ) . The second element is the combination of the heat resistance between the solder joint and the outer side of the lighting assembly (that is, at room temperature ( a) ) ( Rth SP- A) . Figure 2 shows a schematic drawing of this device .
Figure 2 : Model of thermal resistance for a single LED light set . (Courtesy : Cris )
The thermal resistance between the LED junction and ambient ( Rth ja ) is the sum of the resistances :
Rth j – a = Rth j – sp + Rth sp -a
LED (Pd) is determined by multiplying the LED forward voltage discharged (Vf) by direct current ( If ) .
We can now write a formula for the junction temperature of LED include:
Tj = Ta + ( x -a Rth j Pd ) ( 1 )
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