The impact of LED lamp beads on LED display screens

LED (Light Emitting Diode) display screens have revolutionized the world of digital signage, advertising, and large-scale displays. At the heart of these screens are LED lamp beads, the tiny components responsible for producing light. Understanding the impact of LED lamp beads on the performance, quality, and durability of LED display screens is crucial for making informed decisions when selecting or designing these systems.

1. Perspective

The viewing angle of the LED display is determined by the viewing angle of the LED lamp beads.

At present, most outdoor displays use elliptical LEDs with a horizontal viewing angle of 100° and a vertical viewing angle of 50°, while indoor displays use SMD LEDs with a horizontal and vertical viewing angle of 120°. Due to the special nature of the display screen on the highway, it is usually sufficient to use circular LEDs with a viewing angle of 30°.

Some displays on high-rise buildings have higher vertical viewing angle requirements. Viewing angle and brightness are contradictory to each other, and a large viewing angle will inevitably reduce brightness. The choice of viewing angle needs to be determined based on the specific use.

2. Brightness

LED display brightness is an important determinant of display brightness. The higher the brightness of the LED screen, the greater the margin for current usage, which is beneficial to saving power consumption and keeping the LED stable.

LEDs have different angle values. When the brightness of the chip is determined, the smaller the angle, the brighter the LED, but the smaller the viewing angle of the display. Generally, 100-degree LEDs should be selected to ensure adequate viewing angles for the display. For displays with different point spacing and different viewing distances, a balance point should be found in brightness, angle and price.

3. Failure Rate

Since a full-color LED display is composed of tens of thousands or even hundreds of thousands of pixels composed of red, green, and blue LEDs, the failure of any color LED will affect the overall visual effect of the display.

Generally speaking, according to industry experience, the failure rate from the beginning of assembly to the aging of the LED display 72 hours before shipment should not be higher than 30,000 (referring to the failure caused by the LED lamp beads themselves).

4. Antistatic ability

LEDs are semiconductor devices that are sensitive to static electricity and can easily cause electrostatic failure. Therefore, the anti-static ability is crucial to the life of the display screen.

Generally speaking, the human body electrostatic mode test failure voltage of LEDs should not be lower than 2000V.

5. Service life

The theoretical life of the LED device is 100,000 hours, which is much longer than the working life of other components of the LED display. Therefore, as long as the quality of the LED device is guaranteed, the working current is appropriate, the PCB heat dissipation design is reasonable, and the display production process is rigorous, the LED device will be the entire display screen. One of the most durable components in the machine.

LED devices account for 70% of the price of LED displays, so LED devices can determine the quality of LED displays. China is not only a major producer of LED devices, but also a gathering place for LED display manufacturing. The high-tech requirements of LED displays are the future development trend. The high-quality requirements of LED displays are not only related to the direction of LED display manufacturers, but also involve the development of LED display device manufacturers. From the perspective of LED device control, we will promote China’s transformation from a major LED display manufacturing country to a powerful LED display manufacturing country.

6. Attenuation characteristics

After the LED display screen has been working for a long time, the brightness will decrease and the display color will be inconsistent, which is mainly caused by the brightness attenuation of the LED device.

The attenuation of LED Screen brightness will cause the entire screen brightness of the display to decrease. The inconsistency in the brightness attenuation amplitude of red, green and blue LEDs will cause inconsistency in the color of the LED display, which is what we often call the display screen blooming phenomenon.

High-quality LED devices can well control the brightness attenuation amplitude. According to the 20mA standard of lighting at room temperature for 1000 hours, the attenuation of red should be less than 2%, and the attenuation of blue and green should be less than 10%. Therefore, try not to use 20mA current when designing blue and green LED displays. It is best to use only 70% to 80 % of rated current.

In addition to the attenuation characteristics related to the characteristics of the red, green, and blue LEDs themselves, the current used, the heat dissipation design of the PCB board, and the ambient temperature of the display screen all have an impact on the attenuation.

7. Size

The size of the LED device affects the pixel distance of the LED display, that is, the resolution.

The 5mm oval lamp is mainly used for outdoor displays of P16 and above, the 3mm oval lamp is mainly used for outdoor displays of P12.5, P12, and P10, and the 3528 type SMD LED is mainly used for indoor displays of P6 and P8. 2020 type SMD LED is mainly used for indoor displays such as P2 and P3.

On the premise that the dot spacing remains unchanged, increasing the size of the LED device can increase the display area and reduce the graininess. However, due to the reduction in the black area area, the contrast will be reduced; on the contrary, the LED size decreases, reducing the display area and increasing the graininess. , the black area area increases, increasing the contrast.

8. Consistency

The full-color display is made up of countless pixels composed of red, green, and blue LEDs. The consistency of the brightness and wavelength of each color LED determines the consistency of the brightness, white balance, and chromaticity of the entire display. sex.

Generally speaking, display manufacturers require device suppliers to provide LEDs with a wavelength range of 5nm and a brightness range of 1:1.3. These indicators can be achieved by device suppliers through grading by spectrophotometric color separation machines. Voltage consistency is generally not required.

Since LEDs are angled, the full-color LED display also has angular directionality, that is, its brightness will increase or decrease when viewed from different angles. In this way, the angle consistency of red, green, and blue LEDs will seriously affect the consistency of white balance at different angles, directly affecting the fidelity of the display video color.

To achieve consistent matching of the brightness changes of red, green and blue LEDs at different angles, it is necessary to strictly carry out scientific design in packaging lens design and raw material selection, which depends on the technical level of the packaging supplier. No matter how good the normal white balance of the display is, if the angle consistency of the LEDs is not good, the white balance effect of the entire screen at different angles will be poor.

The angle consistency characteristics of LED lamp beads can be measured with a comprehensive LED angle tester, which is particularly important for mid- to high-end displays.

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