1. Principle Introduction
LCD driver board is usually referred to as A / D (Analog / Digital) board, which shows the main function of driver board in a sense. To display an image, LCD screen needs to be digitized through video signal. It is completed LCD driver board from an analog signal to a digital signal (or from a digital signal to another digital signal) conversion function module, and at the same time it drives LCD screen to display an image under the image control unit.
LCD display driver board shown in Figure 1, Figure 2.
Figure 1 Driver Board for Brand LCD Screen
Figure 2 Universal Driver Board for Partial LCD Screen
As figure 3 shows, typically driver board includes the main chip, MCU microcontroller, ROM memory, power supply module, power connector, VGA video signal input interface, OSD keypad interface, converter board interface, LVDS / TTL signal interface etc.
Principle of LCD driver board shown in Figure 4, video signal that from the computer display card gets access to driver board’s master chip through the VGA video signal interface on the driver board. The master chip controls LCD screen to present image based on information of LCD screen in the MCU Microcontroller.
Meanwhile, MCU microcontroller controls the machine's power supply and function operation. Therefore, the LCD driver board is also known as the motherboard of LCD screen.
Figure 3 Chip and Interface of Driver Board
If LCD driver board is damaged, it may cause some problems such as computer fails to start, or shows black, white and blurred screen after starting; or wave interference and the keypad loses control etc, which is the main reason that makes LCD display malfunction.
LCD driver board widely used lots of integrated circuits and chip device. The compact layout of circuit components causes great difficulties in checking out specific components or wire jumper. In the non-factory conditions, it’s hard to repair it. If the driver board malfunctions due to the power supply, damaged VGA video input interface circuit, we can easily solve it as long as we have knowledge of the circuit. However if the driver board does not work due to internal data corruption of MCU microcontroller, with a data file (driver), we can use LCD display programmer to write programming data for MCU microcontroller, which can repair damage caused by the firmware. For early controller board, MCU microcontroller needs to be disassembled. . However, the current driver board has generally started using MCU support ISP (in-circuit programming) microcontroller, so that we can program for internal data of MCU microcontroller via ISP online. For example, the latest LCD
Figure 4 Principle of LCD Driver Board.
For the maintenance of LCD display, when the driver board fails and the LCD display uses universal driver board, you can find the appropriate motherboard to replace it. Of course, corresponding driver for the LCD screen still needs to be written in its MCU; if the driver board is brand board, generally we will use the "universal driver board" to replace.
"Universal driver board" is also known as "all-purpose driver board." At present, there is known brands like ROWA, Dingke, Triumph, Yuekang etc. as shown in Figure 5, Although components of this "universal driver board" is inconsistent with "original driver board", as long as writing the corresponding LCD driver (will randomly send LCD driver CD when buying PG) into "universal driver board," , and then simply change the cable, you can drive different LCD screens. It’s very versatile, and the cost is not high, which can be accepted easily by the users.
ROWA 68167/NA91B Universal Driver Board
ROWA RM3331B Universal Driver Board
ROWA MA4B Universal Driver Board
Dingke 2013B Universal Driver Board
Figure 5 Common Universal Driver Board
Since the LCD screen has a variety of signal interfaces, the signal (TTL / LVDS signal) between universal driver board and LCD screen is also various.
For replacement of universal driver board, there are three parts: light up the LCD screen, change the cable and installment.
1. Tool and Technique of Lighting up the LCD Screen
Lighting up the LCD Screen needs to take out the original LCD screen (Other parts of LCD Display is not required), and according to LCD models, program the universal driver board with LCD driver that is compatible with LCD screen through a programmer. Then find the relevant accessories (Inverter, keypad and LVDS cable). When the LCD screen is lit, it can display an image. If there is no corresponding driver program, it needs to keep programming for the driver board until find the compatible one to light up the LCD screen. This driver board that can light up the LCD screen will replace the damaged mother board of the original LCD display.
Tool kits shown in Figure 6, including: programmer, USB cable, parallel cable, programming software, LCD driver; universal driver board, LVDS cable, VGA cable, keypad with cable, inverter with cable, voltage cable.
Figure 6 Tool Kits
Programmer will take 5V voltage from the computer’s USB as power supply, for universal driver board we generally use adjustable DC 12V power supply. Using the above tool kits, select the appropriate inverter according to the lamps number and interface size of LCD screen, and choose the appropriate LVDS cable and driver board based on the type of LCD signal interface (TTL / LVDS) and interface pin number, and program the driver board with program that is compatible with LCD screen, then you can light up the LCD screen.
Step 1: The programmer is connected to the computer's USB port and parallel port, as shown in Figure. 7
Figure 7 The connection between the Computer and Programmer
Step 2: Make sure the computer's parallel port is ok, turn on the computer, enter the CMOS;
set the computer parallel port number as 378, as shown in Figure 8.
Step 3: enter the XP system, install the LCD programmer integrated program attached in the CD, as shown in Figure 9.
Figure 9 LCD Programmer integrated Program
Step 4: After installation, an icon will appear on the desktop as shown in Figure 10,
Figure 10 LCD Programmer Integrated Program Desktop Icon
Click to change the icon, enter the programmer interface, at the bottom of the software interface there is tips about burning software installation list, as shown in Figure 11, install all burning software.
Figure 11 Burning Software Installation List
After installing the above burning software, click on the left buttons as shown in Figure 12 to use the relevant burning software.
Figure 12 LCD Programmer Integrated Program interface
Based on the chosen driver board, click on the left button as shown in Figure 12 to choose corresponding burning software, shown in Figure 13
Figure 13 The Chosen Burning Software after Clicking Leroy RTD2120 / Leroy RTD2660 Button
Step 5: Register programming software, Only Leroy burning software (ROVA Isp Tools) need to be registered, as shown in Figure 13, click on Leroy RTD2120 / Leroy RTD2660 button to choose the burning software ROVA Isp Tools that needs to be registered. Registration tool of the software is in the collection installation directory, shown in Figure 14, using ROVA burning software tool to register.
Figure 14 ROVA Burning Software Registration
Step 6: After installing burning tool, you can program universal driver board with the driver program. Here we take Leroy RM3331B universal driver board as example, introduce the burning process.
As shown in Figure 15, Connect the driver board with keypad, power connector and VGA cable. The VGA cable is connected to the programmer VGA interface, and the power is connected to the 12V DC power supply.
Figure 15 Connect the Universal Board with the Programmer and the DC Power Supply
To support the programming of Leroy universal board, set the jumpers on the Programming as Mode 1 based on the programmer instructions; Open the LCD programming software, operate Leroy burning software, shown in Figure 13.
Based on MCU models on the universal driver board, choose corresponding model after MCU
Type and Parallel Isp Board after Isp board on the burning software. As shown in Figure
Figure 16 Setting Burning Software, Select the Corresponding MCU Type Model
Click Load File (F3) as shown in Figure 16, load the driver, shown in Figure 17.
Figure 17 Loading the Driver
Click to open as shown in figure 17, back to the interface as shown in Figure 16,
and then click Isp (F9) , start the burning process, as shown in Figure 18.
When the word ”Success” appears, it means that the program is successful.
As shown in Figure 19.
（3）Process of Lighting up the LCD Screen
After tuning the programmer, you can start to light up the LCD screen, firstly check the screen models, interfaces, dimensions, then according to these three parameters, select universal driver board (although called all-purpose controller board, it still needs to match the interfaces; some universal boards support LVDS interface, some support TTL interface, and some support both interfaces; some universal boards support the small size screen, while others support the large size, some boards support both LCD screen interfaces and size, but there is no corresponding driver, therefore, choosing the universal driver board needs to depend on the situations), lastly, based on LCD screen’s signal interfaces and signal interface on the universal board, select appropriate LVDS cable. Now Let s’ explain the process with specific LCD screen.
Take out the LCD screen from the LCD display, there is tube connector, LVDS interface and LCD screen parameters on the LCD screen, as shown in Figure 20, we can see that the LCD model No. is CLAA150XA03, it is 15 inch, signal interface is 30 + 45-pin TTL mode, for the LCD screen we can choose universal driver board Leroy, because it supports TTL interfaces, and has extensive driver in library, in the program library we can find compatible driver, and then choose the TTL signal FFC flat cable.
As shown in Figure 21 connect the universal driver board with keypad, converter board, LCD screen and DC 12V power, meanwhile remember to set the power jumper on the driver board, (laptop LCD screen is 3.3 V power supply, LCD display screen is 5V power supply, if the voltage is low, the image may move, if the voltage is high, and the LCD screen lifetime will be affected). Open the DC power supply, press the ”on” button on the keypad, LCD screen is lit, because the driver board hasn’t been programmed with corresponding drive, no OSD menu is shown on the screen, the LCD screen is black.
We connect VGA cable to the programmer’s VGA interface, as shown in Figure 22, we choose the universal driver board Leroy RM3331, as program method we’ve talked before, programs for this universal Board. (Process is abbreviated)
After programming, , unplug the VGA cable from the programmer's VGA port, press the power button, you can see "NOSIGNAL" on the screen, connect the VGA cable to the VGA port on the computer, images will show on the screen.
3、Change the cable
Now universal driver board and convertor board can light up the fault LCD, if only motherboard is damaged, while other parts, such as power supply, convertor board works, and in order to make original keypad control the universal driver board, it would need to change the cable.
The mother board of original fault LCD includes the following interfaces: TTL (30 + 45pin) signal interface, converter board connector, power connector, the keypad interface, VGA cable connector.
The universal driver board also includes these interfaces, but the pin definitions of some interface is different, we need to analyze pin definitions of interface on these two mother boards
TTL interface: both two boards are 30 + 45PIN, and we also need to replace LVDS cable, the LVDS cable is also corresponding to the LCD, so there is no need to change the cable, if signal interface of LCD screen is other mode, the LVDS cable should be corresponding as well when choose the driver board
Converter board Connector: as shown in the figure, the original converter board connector, we can see that the interface has five cable, diode that uses multi-meter, Firstly check ground cable and the 12V power supply (Converter board usually use DC 12V voltage), To make converter board work, the conditions (voltage and control signals) is needed: power, ground, enabling brightness adjustment. In other words, it needs four cables to connect the control board with the converter board. At least power, ground and enabling these three cables are needed. It is exactly what w e need when we connect the mother board with convertor board
As shown. With this knowledge, we can judge the definition of five cables: Power (black) and ground (red), unknown (white), ground (yellow), unknown (blue), then the unknown white cable and the blue cable may be enabled or brightness adjustment.
Converter board connector on the universal driver board, the interface definition as shown, which is marked at the back of circuit board. In the figure we can see: GEN, ADJ, BL, 12V. ADJ is the brightness adjustment; BL is enabled (sometimes labeled as EN).
Weld the ground cable and power of original converter board to the corresponding position on the universal driver board, now the question is how to connect enabled cable and brightness adjustment cable, in fact, just connect it simply, when it doesn’t display, exchange two cables, it won’t cause damage. If you want to judge accurately, please reference the replacement of converter board we’ve discussed.
Power Interface: The original power connector has five cables: yellow, black, black, red, red. With a multi-meter we can judge whether power supply from the yellow cable and converter board connector is the same voltage, so if the yellow cable is 12V, then the red one should be 5V, because, generally for LCD display there is only two output voltage, 12V and 5V. Universal driver board only requires voltage 12V, You just weld the ground cable and 12V to the corresponding position on the universal driver board.
VGA interface: for original mother board, connect VGA cable directly, which is the same as universal driver board, there is no need to change the cable, just replace the VGA cable.
Keypad interface: Only the original keypad match the LCD display, it is necessary to keep the original keypad, as shown, original keypad with cable. With multi-meter, diode can analyze: black cable --POWER, brown cable –red light, red cable – green light, orange cable --GND, yellow cable --MENU, green cable - +, blue cable - - purple cable --ENTER. If there is component on the keypad, we need to remove all the components, and then connect with the wire directly.
After figuring out the definition of connection on the keypad, then analyze definition of interface on the universal driver board’s keypad, as shown, mark at the back of generic driver board’s connectors. K0, RED, GRN, GND, K1, K2, K3, K4, K5, K6. With the keypad of General Board we can analyze: K0 (POWER), RED (red light), GRN (green light), GND, K1 (-), K2 (+), K3 (ENTER), K4 (MENU), K5 (unused), K6 (unused). Finally, weld the original keypad to the corresponding interface on the universal driver board, as the picture shown.
For maintenance of damaged mother board, replace a new one as the above method.
Of course, for the effect of image display, there may be a little different.