White LEDs are voltage-sensitive devices. In practice, the upper limit of current is 20mA, but the current often increases due to various reasons in use. If no protection measures are taken, this increased current will The LED will be damaged after a certain time and amplitude.

The main reasons for LED damage are:

① Sudden rise in power supply voltage.

②The short circuit of a component or printed line or other wires in the circuit forms a partial short circuit of the LED power supply path, which increases the voltage in this place.

③A certain LED is damaged due to its own quality and thus forms a short circuit, and its original voltage drop is transferred to other LEDs.

④ The temperature in the lamp is too high, which will deteriorate the characteristics of the LED.

⑤ Water has entered the interior of the lamp, and the water is conductive.

⑥ The anti-static work was not done well during assembly, so that the interior of the LED has been damaged by static electricity. Although normal voltage and current values are applied, it is very easy to cause damage to the LED.

So, how should I protect the LED circuit?

1. Fuse (tube) is used in the protection circuit

  Since the fuse is one-time, slow in response, poor in effect, and troublesome to use, the fuse is not suitable for use in finished LED lights, because LED lights are now mainly used in urban glory projects and lighting projects. It requires the LED protection circuit to be very strict: the protection can be started immediately when the normal use current is exceeded, so that the power supply path of the LED is disconnected, so that both the LED and the power supply can be protected, and the power supply can be automatically restored after the entire lamp is normal. Does not affect the LED work. The circuit should not be too complicated, the volume should not be too large, and the cost should be lower. Therefore, it is very difficult to use the fuse method.

2. Use transient voltage suppression diodes (TVS for short)

  TVS diodes are high performance protection devices in the form of diodes. When its two poles are impacted by reverse transient high energy, it can immediately reduce the high resistance between its two poles to low resistance at a speed of 10 to the minus 12 second power in a very short time, absorbing up to several kilowatts of surge power , the voltage between the two poles is clamped to a predetermined voltage value, which effectively protects the precision components in the electronic circuit. TVS diodes have the advantages of fast response time, large transient power, low leakage current, good consistency of breakdown voltage deviation, easier control of clamping voltage, no damage limit, and small size.

However, it is not easy to find TVS devices that meet the required voltage value in actual use. The damage of the LED light beads is mainly caused by the overheating of the inside of the chip due to excessive current. TVS can only detect overvoltage but not overcurrent. To choose the appropriate voltage protection point is difficult to grasp, this kind of device cannot be produced and it is difficult to use in practice.

    The effects of led lamp beads on led display are as follows:

1. Perspective

The viewing angle of the LED display depends on the viewing angle of the LED lamp beads. At present, most outdoor display screens use elliptical LEDs with a horizontal viewing angle of 100°; and a vertical viewing angle of 50°; and indoor display screens use SMD LEDs with both horizontal and vertical angles of 120°. The display screen on the highway generally chooses 30° due to its particularity; the circular LED with the viewing angle is enough. Displays on some tall buildings require higher vertical viewing angles. The viewing angle and brightness are contradictory, and a large viewing angle will inevitably reduce the brightness. The choice of viewing angle needs to be determined according to the specific use.

2. Brightness

LED brightness is an important determinant of display brightness. The higher the brightness of the LED, the greater the margin of the current used, which is good for saving power consumption and keeping the LED stable. LEDs have different angle values. When the brightness of the chip is fixed, the smaller the angle, the brighter the LED, but the smaller the viewing angle of the display. Generally, a 100-degree LED should be selected to ensure a sufficient viewing angle of the display. For displays with different dot pitches and different viewing distances, a balance point should be found in brightness, angle and price.

3. Failure rate

Since the full-color display is composed of tens of thousands or even hundreds of thousands of pixels composed of three types 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 of LED display should not be higher than 3/10,000 (refers to the failure caused by the LED lamp bead itself) before the LED display starts to be assembled and aged for 72 hours before shipment.

4. Antistatic ability

LED is a semiconductor device, which is sensitive to static electricity and can easily lead to static electricity failure. Therefore, the anti-static ability is very important to the life of the display screen. Generally speaking, the failure voltage of LED human body electrostatic mode test should not be lower than 2000V.

5. Lifespan

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 suitable, 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 parts in a machine.

LED devices account for 70% of the price of LED displays, so LED devices can determine the quality of LED displays. my country is not only a big producer of LED devices, but also a gathering place for LED display production. The high-tech requirements of LED display are the future development trend. The high-quality requirements of LED display are not only about the trend of LED display manufacturers, but also the development of LED display device manufacturers. From the control of LED devices, to promote China's transformation from a large LED display manufacturing country to a powerful LED display manufacturing country.