What is the impact of high temperature operation of LED electronic screen?
In today's increasingly widespread application of LED electronic screens, in order to maximize the use benefits of the display, application companies should have the basic knowledge of LED electronic screen maintenance. Whether it is an indoor LED electronic screen or an outdoor LED electronic screen, heat will be generated during operation, and the generated heat will cause the temperature of the LED electronic screen to rise. But what about the display effect under high temperature working conditions?
Large LED screen
Under normal circumstances, the indoor LED electronic screen can naturally dissipate heat due to its low brightness and low heat generation; however, the outdoor LED electronic screen has high brightness and high heat generation, requiring air conditioners or axial fans to dissipate heat. Since the LED electronic screen is an electronic product, the increase in temperature will affect the light decay of the LED electronic screen lamp beads, the working efficiency of the driver IC and the service life of the LED display.
1. LED electronic screen circuit breaker and failure
The operating temperature of the LED electronic screen exceeds the load temperature of the chip, which will rapidly reduce the luminous efficiency of the LED screen, resulting in obvious light decay and damage; most large LED screens are encapsulated with transparent epoxy resin. If the junction temperature exceeds the solid phase transition temperature ( Usually 125°C), the encapsulation material will turn rubbery, and the thermal expansion coefficient will rise sharply, causing the LED electronic screen to open and fail. Excessive temperature will affect the light decay of the LED electronic screen.
The life of the LED electronic screen is manifested in its light decay, that is, the brightness becomes lower and lower over time until it goes out. It is usually defined as the life of the LED electronic screen when the luminous flux is attenuated by 30 times. High temperature is the main source of light decay of LED display and shortened life of LED electronic screen. The light decay of different brands of LED electronic screens is different. Usually, LED electronic screen manufacturers will give a set of standard light decay curves. The attenuation of the luminous flux of the LED electronic screen caused by high temperature is irreversible. The luminous flux of the LED electronic screen before irreversible light attenuation does not occur, which is called the "initial luminous flux" of the LED electronic screen.
2. The increase in temperature will reduce the luminous efficiency of the LED electronic screen
As the temperature increases, the concentration of electrons and holes increases, the band gap decreases, and the electron mobility decreases; as the temperature increases, the probability of radiative recombination of electrons and holes in the potential well decreases, resulting in nonradiative recombination. heat), thereby reducing the internal quantum efficiency of the LED electronic screen; the increase in temperature causes the blue peak of the chip to move to the long-wave direction, which makes the emission wavelength of the chip do not match the excitation wavelength of the phosphor, and also causes the external optoelectronic screen of the white LED. Decrease extraction efficiency.
As the temperature increases, the quantum efficiency of the phosphor decreases, the luminous amount decreases, and the external light extraction efficiency of the LED electronic screen 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, resulting in a decrease in the refractive index of the silica gel, thus affecting the light efficiency of the LED electronic screen.
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Q: What is the brightness, viewing angle and wavelength of the LED? |
A: Luminous Intensity is equal to the amount of luminous flux emitted into a very small solid angle at a defined angular orientation from the light source. The measurement for luminous intensity is the candela. Symbol is Iv.Viewing Angle is the total cone angle in degrees encompassing the central, high luminous intensity portion of the LED beam from the on-axis peak to the off-axis point where the LED intensity is 50% of the on-axis intensity. This off-axis point is known as theta one-half ( 1/2). Two times 1/2 is the LEDs' full viewing angle; however, light is visible beyond the1/2 point.Wavelength is the distance between two points of corresponding phase and is equal to waveform velocity divided by frequency. It defines what color human eyes could recognize |
Q: What is dominant wavelength? Please specify the ranges of wavelength in red, green and blue color respectively. |
A: Dominant wavelength is defined as the best range of wavelength showing the most natural color recognized by human eyes. Researches indicate that fixed colors with wavelength of 620-630nm (red), 520-530nm (green) and 460-470nm (blue), in fact mixed in a particular proportion, can get the pure white. That is, in display field, people use luminous materials with above wavelength to make "compounded" white more natural.In order to get a good balance white led display, we specify the led colors with wavelength within 4nm for each color |
Q: Which chip vendors are you buying from? |
A: It depends on the Customer's requirement. We can purchase from Japan, Korea, Europe, USA. We are using chips mainly from Taiwan |
Q: What is the chip size you're using for outdoor display? How about indoor display? |
A: For outdoor display, we're using 12mil chip for red, 14mil for both green and blue. Regarding indoor display, 9mil for red, 12mil for green and blue are currently adopted |
Q: How much will the brightness of LED drop down after 1000hrs? |
A: Based on the result of aging test, the brightness decay of green LED is around 5%-8%, while blue is around 10%-14% and red is around 5%-8% |