Frequently Asked Questions
The working characteristic of high power LED products
With the continuous development of LED technology. The white LED Lighting industry have started green lighting era. Low thermal energy, high luminous efficiency,LED is a kind of energy saving, environmental protection, economy, safety of new lighting devices. Accelerating technology research and improve the efficiency in primary problem. High power LED lighting industry become to the subject. One safe and efficient driver research is the key of high power LED application.
High power LED work characteristics
LED is a new kind of semiconductor solid cold light, it is a kind of energy can be transformed into visible photoelectric device. Generally speaking, the power of the high power LED for 1 W at least, more common as 1W, 3w, 5w, 8w and 10W are Called the “green light”.It was LED current (300 mA ~ 1.4 A), high efficiency (60 ~ 120 lm/W), brightness adjustable direction.
(1) the volt-ampere characteristics
High power LED is low voltage, large current driving devices. When LED voltage change very hour, current changes greatly.
(2) optical properties
According to the principle of light, the luminous intensity of LED have the basic change with LED current .The essense of controling output flux is to control power LED luminous intensity.
The size of the LED positive current also changes with the temperature. Once environmental temperaturemore is heigher than one value , the allows current of white LED would greatly reduce positive. It’s easy to case the white LED aging if we still exert great current.
LED Display Screen FAQ and solution
1. Whole screen does not work (black screen)
(1) Check power supply
(2) Check signal connection (cat5, DVI cable) (synchronous screen)
(3) If synchronous screen, check the green led of sending card and receiving card whether it is twinkling or not.
(4) Check the monitor of PC whether it is protected as black, or screen display area is black or pure blue. (Synchronous screen)
2. Whole LED module does not work (black module)
(1) Successive modules in horizontal do not work, please check the ribbon cable between the normal unit module and unnormal unit module whether it is connected or not, or replace the first module from right side when facing the screen.
(2) Successive modules in vertical row does not work, please check the power supply of all the modules.
3. One row lamps of module does not work.
(1) Check this row whether connecting to output pin of 4953.
(2) Check 138encoder.
(3) Check 4953.
(4) Check Vcc and GND of 4953.
(5) Check output of 74HC138 and 4953’s controlling pin whether connected or not.
4. Unit module doesn’t work.
(1) Check 595 normal or not.
(2) Checking the up and down module corresponded common pin connect or not.
(3) Check 595 output pin to module pin connect or not.
5. One color lacked in half or whole LED panel.
(1) Check 245 R, G, B data output.
(2) Check normal 595 output pin and unnormal 595 inputs pin whether it is connected well or not.
FAQ and solutions of LED display
|Whole screen no display||a. No AC power supply.||Check main power cable and reconnect it.|
|b. The computer isn’t working||Check the computer|
|c. Main data cable is broken.||Reconnect the main data cable correctly or change a new one.|
|d. Control system is broken.||Check indicators on sending card and receiving card, if red one keep lighting while green one blinking when the system is ok, otherwise use spare parts to replace.|
|e. Receiving card is no power.||Check power cable between receiving card and power supply|
|f. Software setting is wrong.||Correct the software setting to suit the control system.|
|Whole screen blinking.||a. Ground wire is broken.||Connect the ground wire between the computer and screen.|
|b. Control system is broken down.||Change the control system.|
|c. Some signal of the data cable is lost.||Examine the data cable, reconnect it correctly or change a new one.|
|d. Refresh rate setting is wrong||Correct the Refresh rate setting|
|Module not work||a. Unit module has no power supply||Voltage for unit module is 5V.|
|b. Flat cable between two modules is cut off.||Change the flat cable.|
|c. 245 IC is broke down.||Change new 245 IC|
|part of module works abnormally||Signal of the part is wrong.||Check the resistance near the 5026 IC which control that area.|
|Rows of module are not lighting||Corresponding 4953 or 245 IC is not working.||Examine the corresponding 4953 or 245 IC|
|Columns of module are not lighting||Corresponding 5026 IC is not working||Examine 5026IC or change a new one.|
|Dots out of control||Pins or 5026 IC short connected||Re-soldering the 5026IC or change a new one.|
|The display texts have shadows.||Data cable or DVI cable connected incorrectly||Reconnect main data cable or DVI cable between graphic card and sending card|
What factors determine the full color LED display advantages
A full color LED display is good or bad can be identified from the following aspects:
LED display screen surface flatness to within ± 1mm to ensure that the displayed image is not distorted, partial raised or recessed will lead to the display viewing angle of dead ends. The quality of flatness is determined mainly by the production process.
Second,Brightness and viewing angle
Indoor full color display brightness in 800cd/m2 above, outdoor full color display brightness to 1500cd/m2 above in order to ensure the normal work of the screen, otherwise it will not see the displayed image brightness is too low. Size of the brightness of the LED die is good or bad decision.
Directly determine the size of the viewing angle display the number of audience, and therefore the bigger the better. The size of the viewing angle is mainly determined by the die package.
Third, White balance effect
The white balance effect is one of the most important indicator in the display. School taken in the proportion of red, green and blue colors will show 1:4.6:0.16 pure white, if the actual proportion of the deviation of the white balance of a little deviation occurs, and generally pay attention to whether the white bluish, partial yellow-green phenomenon. The white balance is good or bad by the display control system, the die also have an impact on the reduction of color.
Fourth, Reduction of color
The reduction of color refers to the display of color reduction, which indicates not only the screen display color to be highly consistent with the color of the source, so as to ensure realism of the image.
Fifth, Whether the phenomenon Mosaic dead spots
Mosaic is to point to to appear on screen ChangLiang or often black small four square, already module necrosis phenomenon, the main reason for the screen to answer the plug-in quality not pass.
The dead appear on the LED display lit or normally black single point, how much of the dead die is good or bad.
What is virtual pixel, real pixel
Real and virtual-pixel screen is the corresponding.
Simply, real pixel is each LED of three red-green-blue LED which constitute a screen display is only involved in the use of an imaging pixel, in order to obtain sufficient brightness
Virtual screen is to use software algorithms to control the LED of each color to participate in the final number of adjacent pixels of the image, making the lamp with less LED to achieve greater resolution, it can increase about four times resolution.
As we all know, the largest cost is Led chip for Led display, one of our target is that we can save the cost but do not less the brightness. The virtual technology is a development direction. The virtual technology is not a simple tube to participate in imaging, it impact much for the brightness, gray. It requires the control system coordinate with the driver chips, to use the software algorithms and driver chips to combine response time, to save the Led cost but do not less the brightness.
What is dynamic display, what is static state display
Static screen is corresponding to the scan screen, static screen is the LED display in the display text, images, video, LED lights on display is lighted at the same time; it is not like the scan screen to use the person eye’s temporary characteristics,Scan screen instead of using the human eye as the visual characteristics of temporary stay, to light each line of Led screen separately. As we all know, led display is drived by room ratio, the brightness is related to the light time. So, if the same brightness of Led, the brightness of static screen is more than scan screen. Therefore, a static screen is used for high-brightness and outdoor display, and scan screen commonly use for scanning screen which do not need the high brightness to save the driver cost.
However, with the LED materials technology is developed continuesly, brightness of LED is improved continuously. In order to save the cost, outdoor display also use scan driver. Of course, the high request for the control and driver when use scan driver for outdoor led display, also request the very high performance chips.