Technology | What is the effect of LED display under high temperature working condition

818 views admin 2020-06-19

In today's increasingly widespread application of LED display screens, in order to maximize the use of display screens, application companies should have basic knowledge of LED display maintenance. Whether it is an indoor LED display or an outdoor LED display, heat will be generated during operation, and the generated heat will cause the temperature of the LED display to increase. But what effect does the display have under high-temperature working conditions, do you know? The following editor will analyze and analyze it with you. Under normal circumstances, indoor LED display screens generate less heat due to low brightness, and can dissipate heat naturally; however, outdoor LED display screens require high heat due to high brightness and need to be dissipated through air conditioning or axial fans. Since the LED display is an electronic product, the increase in temperature will affect the light decay of the LED display lamp beads, the working efficiency of the driver IC, and the service life of the LED display.

Luminous efficiency decreases rapidly

If the operating temperature of the LED display exceeds the load temperature of the chip, the luminous efficiency of the LED display will rapidly decrease, resulting in significant light decay and damage; the LED display is mostly encapsulated with transparent epoxy resin, if the junction temperature exceeds the solid phase transition At a temperature (usually 125°C), the encapsulation material will change to a rubbery shape and the coefficient of thermal expansion will suddenly increase, resulting in an open circuit and failure of the LED display screen.

Excessive temperature will affect the light attenuation of the LED display

The life of the LED display is shown by its light decay, that is, the brightness is getting lower and lower until it finally goes out. It is usually defined that the time for the luminous flux of the led display to decay by 30 is its lifetime. High temperature is the main source of LED display light decay and shorten the life of LED display. The light decay of different brands of LED display is different, usually led display manufacturers will give a standard set of light decay curve. The luminous flux attenuation of the LED display screen caused by high temperature is unrecoverable. The luminous flux of the LED display screen before the unrecoverable light attenuation does not occur is called the "initial luminous flux" of the LED display screen.

Increased temperature will reduce the luminous efficiency of LED display

As the temperature increases, the concentration of electrons and holes will increase, the width of the forbidden band will decrease, and the electron mobility will decrease; as the temperature increases, the probability of radiative recombination of electrons and holes in the potential well decreases, resulting in non-radiative recombination (generation Heat), thereby reducing the internal quantum efficiency of the LED display; the increase in temperature causes the blue peak of the chip to shift to the long wave direction, which makes the emission wavelength of the chip and the excitation wavelength of the phosphor mismatch, and also causes white light outside the LED display The extraction efficiency decreases; as the temperature rises, the phosphor quantum efficiency decreases, the light output decreases, and the external light extraction efficiency of the LED display decreases; the performance of the silica gel is greatly affected by the ambient temperature. As the temperature increases, the thermal stress inside the silica gel increases, causing the refractive index of the silica gel to decrease, thereby affecting the light efficiency of the LED display screen.

The influence of temperature on the luminous wavelength (light color) of LED display

The emission wavelength of the LED display screen can generally be divided into a peak wavelength and a dominant wavelength. The peak wavelength is the wavelength with the largest light intensity, and the dominant wavelength can be determined by the X and Y chromaticity coordinates, reflecting the colors perceived by the human eye. Obviously, the change in the luminous wavelength of the LED display screen caused by the junction temperature will directly cause different perceptions of the human eye to the luminous color of the LED display screen. For a led display device, the forbidden band width of the light-emitting area material directly determines the wavelength or color of the device. As the temperature increases, the forbidden band width of the material will decrease, resulting in a longer emission wavelength of the device and a red-shifted color.

Excessive temperature will limit the maximum injection current of LED display

When choosing LED display, you should pay attention to choose LED display chip brand, packaging manufacturer, driver IC brand, switching power supply brand, the quality of the brand will affect the product quality of the LED display itself, and the brand is high The product itself generates less heat and can better control the temperature of the LED display, thereby extending the life of the LED display.

LED display screen has great development prospects due to its advantages of energy saving, environmental protection and long life. LED display is relatively sensitive to temperature: it will affect the life, light effect, color, etc. of the LED display. So the right temperature is very important for LED display.