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Time : 2015-06-03 16:58Source :analogtechnologies Author : Analog Click :

LED is a kind of solid semiconductor lighting devices. Similar with traditional light source, during work, the solid light source will generate heat because of current flowing in the diodes. As long as the current flows continuously, the heat will continue to be produced. The node temperature of LED must be below 125℃. The high node temperature will bring many adverse effects, such as the quantum efficiency of LED reducing, the luminousefficiency declining, the peak wavelength shifting and service lifetime severely shortening. 

For LED devices with different power, the density of heat flow rate generated by chips is of all sizes. In order to control their node temperatures, LED needs a certain dissipation method to realize good thermal management. There are two ways of dissipation, thermoelectric cooler (TEC) and heat sink, which can meet the cooling requirements of LED devices with different power. Next, TEC is applied in the LED packaging will be mainly introduced.



Fig 1. Schematic diagram of thermoelectric cooler

TEC is made of semiconductor thermocouples with obvious thermoelectric effect and high cooling efficiency. As shown in the figure 1, a P-type semiconductor element and an N-type semiconductor are connected into thermocouples and after connecting a DC power supply, at the joint, there will generate the temperature and heat transfer. On the top of the joint, the current will flow from N to P and the temperature will reduce, which is called cold side; at the junction below, the current direction is from P to N, which is called hot side.

Next : Recent prospect of thermoelectric materials Last : The heat resistance theory of heat sink