Views: 83 Author: Site Editor Publish Time: 2020-03-03 Origin: Site
Since 1962, the United States General Electric Company has developed the world's first practical application of red LEDs. So far, LED has entered the era of full color. The LED are a PN diode composed of a P-type semiconductor containing a hole and an N-type semiconductor containing electrons. A forward bias is applied across the PN diode. When the current passes, the electron and the hole are passed. When the flow reaches the joint, it emits energy and emits light. The LED itself is a monochromatic light source. Nowadays, with the improvement of light efficiency and the appearance of blue LED, its application is gradually diversified. LED is known as the new light source for lighting in the 21st century.
Due to the development of high-power LED technology, LED lamps face the severe challenges of thermal management and heat dissipation design, because the temperature rise will not only cause the brightness to drop, but also accelerate the deterioration of the lamp body and packaging materials when the temperature exceeds 100 ℃. Therefore, in addition to the heat dissipation technology of the LED package component itself, the heat design of the LED lamp is the biggest key to maintaining the life of the lamp.
The LED chips are linked by soldering and the system board, and the thermal energy generated by the chips is also conducted from the chip substrate to the system board. For system boards with heavy responsibility for transferring heat, the back end of the system board is combined with the heat dissipation system for heat dissipation. The heat dissipation system can be divided into active heat dissipation and passive heat dissipation. Active heat dissipation includes fan forced cooling and electromagnetic jet heat dissipation. Passive heat dissipation includes natural convection cooling and loop heat pipe cooling.
As the name implies, forced cooling of fan is to generate air convection by fan, which leads hot air out of the lamp body for cooling. Forced cooling of fan can effectively discharge heat . This technology is used in computers, air conditioners and automobiles.
Electromagnetic jet heat dissipation does not use fan blades to generate airflow. The structure is a hollow body with a film that oscillates the film at a frequency of 100 to 200 times per second using an electromagnetic to cause the film to oscillate up and down. As the film moves up and down, the air will flow into the hollow cavity and then ejected. The airflow after the jet will drive the surrounding air to generate eddy current and enhance the air convection capability.
The natural convection heat dissipation works through the direct contact of heatsink and air. The air around the heatsink becomes hot air due to heat absorption. Then the hot air rises and the cold air drops, which will naturally drive the air to produce convection and achieve the effect of heat dissipation. With the introduction of high-power lamps, the heatsink requires a large surface area, such as zipper fin heatsink, cast heatsink, VC heatsink and so on.
The heat dissipation method is to dissipate heat through a circulating heat pipe, and the two ends of the circuit pipe are a system circuit board and a heat sink. The inside of the loop tube is filled with working fluid and is equipped with an evaporator. The working principle is that when the heat is transmitted from the system board, the working fluid at the heat source absorbs heat, and then is converted into gas by the evaporator. With the rapid movement of the gas, the heat at the heat source can be quickly transmitted to the lamp housing or the radiator. Therefore, the heat dissipation of the loop heat pipe only solves the heat conduction problem and cannot effectively achieve the heat dissipation function.
With the maturity of LED lighting technology, the popularity of LED lighting applications, the resolution of heat dissipation issues is crucial. Although there are many heat dissipation methods, there are still limitations. Therefore, there is still a need for deep research and development in LED lighting and heat dissipation technology, in order to lay a foundation for the mature development of LED related technologies and the wide application of LEDs.
