High temperatures can cause the probability of failure of electronic components to increase rapidly, resulting in a decrease in the reliability of LED displays . In order to control the temperature of the electronic components inside the LED display so that it does not exceed the specified maximum allowable temperature under the working environment under which the LED display is placed, the heat dissipation design of the LED display is required. The heat dissipation design of the LED display, how to achieve low cost and high quality, is the content of this article.
First, the knowledge of heat dissipation design
The two basic laws of heat transfer: heat flows from the high temperature zone to the low temperature zone; the heat generated by the high temperature zone is equal to the heat absorbed by the low temperature zone.
There are three basic ways of transferring heat: heat conduction, convection, and radiation.
Thermal conduction: Gas heat conduction is the result of collisions between gas molecules when they move irregularly. The heat conduction in the metal conductor is mainly achieved by the movement of free electrons. Thermal conduction in non-conductive solids is achieved by vibration of the lattice structure. The heat conduction mechanism in the liquid mainly depends on the action of elastic waves.
Convection: refers to the heat transfer process caused by the relative displacement between various parts of the fluid. Convection only occurs in the fluid and is necessarily accompanied by thermal conduction. The heat exchange process that occurs when fluid flows over the surface of an object is called convective heat transfer. The convection caused by the difference in density of the various parts of the fluid is called natural convection. If the motion of the fluid is caused by an external force (fan, etc.), it is called forced convection.
Radiation: The process by which an object transmits its ability in the form of electromagnetic waves is called thermal radiation. Radiant energy transfers energy in a vacuum and has a conversion in the form of energy, that is, thermal energy is converted into radiant energy and radiant energy is converted into thermal energy.
When selecting the heat dissipation method, the following factors should be considered: heat flux density, volume power density, total power consumption, surface area, volume, and working environment conditions (temperature, humidity, air pressure, dust, etc.) of the LED display.
According to the heat transfer mechanism, there are natural cooling, forced air cooling, direct liquid cooling, evaporative cooling, thermoelectric cooling, heat pipe heat transfer and other heat dissipation methods.
A comparison of several common cooling methods is as follows:
Natural cooling forced air cooling direct liquid cooling evaporative cooling
Heat dissipation capacity W/cm? (When temperature rise is 40 °C) 0.040.30.61.1
It is easier and harder to achieve
Weight or volume high, medium and low
No noise or vibration
No low or low power consumption
Low cost, high and high
Maintenance is easier and more difficult
It can be seen from the above table that the heat dissipation effect of natural cooling is relatively small, and the heat dissipation effect of evaporative cooling is relatively large. The human body sweats and cools down, using the heat dissipation method of evaporative cooling.
Second, the LED display heat dissipation design method
As can be seen from practical applications, the current LED display has more internal heat, and the electronic components with more heat are: LED, driver IC, and switching power supply. Therefore, it is necessary to heat-dissipate the LED display to provide a low thermal resistance path between the heat source and the external environment to ensure the smooth transfer of heat.
When the temperature of the object is lower than 1800 °C, the meaningful thermal radiation wavelength is between 0.38 and 100 μm, and most of the energy is in the range of 0.76~20μm in the infrared band. In the visible light band, the specific gravity of the thermal radiation energy is not large. Therefore, the interior of the LED display can be freely coated with various colors. The outside of the LED display that is exposed to direct sunlight should be painted in a light color to avoid absorption of visible light.
Considering the use of the LED display screen, the rental screen and the indoor fixed installation screen mostly use the method of natural cooling and heat dissipation, and the outdoor fixed installation screen uses the method of forced air cooling to dissipate heat.
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