Anti-interference device for PCB (printed circuit board) of liquid crystal display module

Abstract

The invention discloses a liquid crystal display module PCB anti-interference device, and relates to the technical field of liquid crystal display modules, the liquid crystal display module PCB anti-interference device comprises a PCB substrate, a display driving module, a backlight driving module and a power supply input interface are integrated on the PCB substrate, and a multi-stage power supply filtering module, a signal shielding and impedance matching module and a layout isolation module are arranged on the PCB substrate; the multi-stage power supply filtering module is connected among the power supply input interface, the display driving module and the backlight driving module, the signal shielding and impedance matching module is connected with the display driving module and an external FPC interface, and the layout isolation module is arranged between the display driving module and the backlight driving module. The multi-stage power supply filtering module comprises a common mode inductor, a first differential mode inductor, a second differential mode inductor, a ceramic capacitor bank and a tantalum capacitor bank. According to the invention, a cooperative anti-interference system is constructed from three dimensions of power supply filtering, signal transmission and layout isolation, and the problems of wide-band power supply noise, signal radiation interference and circuit coupling interference are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid crystal display module, and particularly relates to a liquid crystal display module PCB anti-interference device. BACKGROUND

[0002] LCM (Liquid Crystal Module) is the core display component of electronic equipment, and is widely used in vehicle navigation, industrial control panel, consumer electronics and other fields. With the improvement of the integration of electronic equipment, the electromagnetic environment of LCM module is increasingly complex, and electromagnetic interference from radio frequency circuit, power system, motor equipment and the like easily invades the module circuit through conduction or radiation, resulting in abnormality such as noise, horizontal lines and flicker in the display picture, which seriously affects the product reliability.

[0003] The anti-interference design of the existing LCM module mainly focuses on single link optimization, for example, wrapping conductive cloth around FPC wire to shield, or setting a simple filter capacitor at the power input end. However, these schemes have obvious defects: firstly, the power noise suppression is not complete, and the traditional single-stage filtering cannot cover the wide-band interference, resulting in chip operating voltage fluctuation; secondly, the high-speed signal transmission process is easily affected by radiation interference, and impedance mismatch of differential signal lines will cause signal reflection; thirdly, the PCB layout lacks systematic isolation, and there is a coupling path between the strong interference source such as backlight drive and the display drive circuit. Therefore, a hardware circuit design integrating multi-stage anti-interference measures is urgently needed to improve the electromagnetic compatibility of LCM module from the power, signal and layout dimensions, and the present application provides a liquid crystal display module PCB anti-interference device. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a liquid crystal display module PCB anti-interference device, which constructs a cooperative anti-interference system from the power filtering, signal transmission and layout isolation dimensions, solves the problems of wide-band power noise, signal radiation interference and circuit coupling interference, and overcomes the deficiencies of the prior art.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme: A liquid crystal display module PCB anti-interference device, comprising a PCB substrate, wherein the PCB substrate is integrated with a display drive module, a backlight drive module and a power input interface, and the PCB substrate is provided with a multi-stage power filtering module, a signal shielding and impedance matching module and a layout isolation module; the multi-stage power filtering module is connected between the power input interface and the display drive module and the backlight drive module, the signal shielding and impedance matching module is connected between the display drive module and the external FPC interface, and the layout isolation module is arranged between the display drive module and the backlight drive module.

[0006] As a further embodiment of the present invention: the multi-stage power filtering module includes a common-mode inductor, a first differential-mode inductor, a second differential-mode inductor, a ceramic capacitor bank, and a tantalum capacitor bank. The input terminal of the common-mode inductor is connected to the power input interface, and the output terminal of the common-mode inductor is connected to the first differential-mode inductor and the second differential-mode inductor respectively. The output terminal of the first differential-mode inductor is connected to the power supply terminal of the display driver module, and the output terminal of the second differential-mode inductor is connected to the power supply terminal of the backlight driver module.

[0007] As a further embodiment of the present invention: the ceramic capacitor bank is connected in parallel between the common mode inductor output terminal and ground, and the tantalum capacitor bank is connected in parallel between the first differential mode inductor output terminal and ground, and the second differential mode inductor output terminal and ground, respectively.

[0008] As a further embodiment of the present invention: the ceramic capacitor bank includes a first ceramic capacitor, a second ceramic capacitor, and a third ceramic capacitor, which are connected in parallel to form a wideband filter network.

[0009] As a further aspect of the present invention: the tantalum capacitor bank includes a first tantalum capacitor and a second tantalum capacitor.

[0010] As a further embodiment of the present invention: the signal shielding and impedance matching module includes a metal shield, a differential signal line group and a matching resistor group. The differential signal line group connects the display driver module and the external FPC interface. The metal shield is placed outside the differential signal line group and connected to the ground layer of the PCB substrate. The matching resistor group is connected in series at both ends of the differential signal line group.

[0011] As a further aspect of the present invention: the matching resistor group includes a first matching resistor and a second matching resistor, which are connected in series in the positive and negative lines of the differential signal line group, respectively.

[0012] As a further embodiment of the present invention: the metal shielding cover is made of tin-phosphor bronze, the inner wall is coated with conductive silver paste, and the bottom is provided with solder feet to connect with the grounding pad of the PCB substrate.

[0013] As a further embodiment of the present invention: the layout isolation module includes a physical isolation strip, a grounding via array and a shielding baffle. The physical isolation strip is filled with grounding copper foil. The grounding via array is evenly distributed on both sides of the physical isolation strip and communicates with the grounding layer. The shielding baffle is vertically fixed above the physical isolation strip and welded to the grounding copper foil.

[0014] As a further embodiment of the present invention: the width of the physical isolation strip is 2-3mm, the hole spacing of the grounding via array is 0.5mm, and the hole diameter is 0.3mm.

[0015] The beneficial effects of this invention are as follows: 1. The multi-stage power filtering module adopts a "common-mode inductor + dual differential-mode inductor + hybrid capacitor bank" architecture. The common-mode inductor suppresses common-mode interference, the dual differential-mode inductors target differential-mode interference of the display and backlight driving circuits respectively, the ceramic capacitor bank covers the high-frequency band (10kHz-1GHz), and the tantalum capacitor bank targets the low-frequency band (10Hz-10kHz), achieving wide-band (10Hz-1GHz) power noise suppression, reducing the voltage fluctuation amplitude from ±0.5V in the existing technology to ±0.05V; 2. The signal shielding and impedance matching module achieves radiated interference isolation through a metal shielding cover, with a shielding effectiveness of over 40dB. Combined with the matching resistor group, it achieves 50Ω impedance matching for differential signal lines, optimizing the signal reflection coefficient from -10dB in existing technologies to -25dB, and reducing the bit error rate of high-speed signal (1Gbps) transmission by 90%. 3. The layout isolation module adopts a three-dimensional isolation structure of "physical isolation strip + grounding via array + shielding baffle". The physical isolation strip blocks the surface coupling path, the grounding via array forms a three-dimensional grounding shielding wall, and the shielding baffle further suppresses spatial radiation coupling. The interference coupling attenuation between the display driving module and the backlight driving module reaches 60dB, completely solving the problem of strong interference source coupling. Attached Figure Description

[0016] Figure 1 This is a first-view three-dimensional structural diagram of an anti-interference device for a liquid crystal display module PCB board proposed in this invention.

[0017] Figure 2 This is a first-view three-dimensional structural diagram of an anti-interference device for a liquid crystal display module PCB board proposed in this invention.

[0018] Figure 3 This is a partial, first-view structural diagram of an anti-interference device for a liquid crystal display module PCB board proposed in this invention.

[0019] Figure 4 This is a partial split-view structural diagram of an anti-interference device for a liquid crystal display module PCB board proposed in this invention.

[0020] Figure 5 This invention proposes an anti-interference device for a liquid crystal display module PCB board. Figure 3 Enlarged structural diagram at point A Figure 6 This invention proposes an anti-interference device for a liquid crystal display module PCB board. Figure 3 Enlarged structural diagram at point B.

[0021] In the diagram: 1. PCB substrate; 2. Display driver module; 3. Backlight driver module; 4. Power input interface; 5. Multi-stage power filtering module; 6. Signal shielding and impedance matching module; 7. Layout isolation module; 8. Common mode inductor; 9. First differential mode inductor; 10. Second differential mode inductor; 11. Ceramic capacitor bank; 12. Tantalum capacitor bank; 13. Metal shield; 14. Differential signal line bank; 15. Matching resistor bank; 16. External FPC interface; 17. Ground layer; 18. Physical isolation strip; 19. Grounding via array; 20. Shielding baffle; 21. Grounding copper foil; 22. First ceramic capacitor; 23. Second ceramic capacitor; 24. Third ceramic capacitor; 25. First tantalum capacitor; 26. Second tantalum capacitor; 27. First matching resistor; 28. Second matching resistor. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] Example 1, referring to Figures 1-6 An anti-interference device for a liquid crystal display module PCB board includes a PCB substrate 1. The PCB substrate 1 is made of FR-4 material and has a thickness of 1.2mm. The PCB substrate 1 integrates a display driver module 2 (model: SSD1963), a backlight driver module 3 (model: AP3426), and a power input interface 4 (model: DC-005). The PCB substrate 1 is provided with a multi-stage power filtering module 5, a signal shielding and impedance matching module 6, and a layout isolation module 7. The multi-stage power filtering module 5 is connected between the power input interface 4 and the display driver module 2 and the backlight driver module 3. The signal shielding and impedance matching module 6 is connected between the display driver module 2 and the external FPC interface 16. The layout isolation module 7 is disposed between the display driver module 2 and the backlight driver module 3.

[0024] The multi-stage power filtering module 5 includes a common-mode inductor 8, a first differential-mode inductor 9, a second differential-mode inductor 10, a ceramic capacitor bank 11, and a tantalum capacitor bank 12. The input terminal of the common-mode inductor 8 is connected to the power input interface 4, and the output terminal of the common-mode inductor 8 is connected to the first differential-mode inductor 9 and the second differential-mode inductor 10 respectively. The output terminal of the first differential-mode inductor 9 is connected to the power supply terminal of the display driver module 2, and the output terminal of the second differential-mode inductor 10 is connected to the power supply terminal of the backlight driver module 3.

[0025] The specific connection relationship of the multi-stage power filter module 5 is as follows: the input terminal of the common-mode inductor 8 (model: ACM7060-102) is connected to the positive and negative terminals of the power input interface 4 through copper foil lines. The output terminal of the common-mode inductor 8 is divided into two paths: one path is connected to the first differential-mode inductor 9 (model: CD54-100), and the other path is connected to the second differential-mode inductor 10 (model: CD54-220). The output terminal of the first differential-mode inductor 9 is connected to the VDD pin of the display driver module 2, and the output terminal of the second differential-mode inductor 10 is connected to the VIN pin of the backlight driver module 3. The ceramic capacitor group 11 is composed of the first ceramic capacitor 22 (0.1μF / 0805), the second ceramic capacitor 23 (1μF / 0805), and the third ceramic capacitor 24 (10μF / 0805) connected in parallel. One end is connected to the common point of the output terminal of the common-mode inductor 8, and the other end is connected to the ground layer 17. In the tantalum capacitor group 12, the first tantalum capacitor 25 (100μF / 35V) is connected in parallel between the output terminal of the first differential mode inductor 9 and ground, and the second tantalum capacitor 26 (100μF / 35V) is connected in parallel between the output terminal of the second differential mode inductor 10 and ground.

[0026] Ceramic capacitor bank 11 is connected in parallel between the output terminal of common mode inductor 8 and ground, and tantalum capacitor bank 12 is connected in parallel between the output terminal of first differential mode inductor 9 and ground, and the output terminal of second differential mode inductor 10 and ground, respectively.

[0027] The ceramic capacitor bank 11 includes a first ceramic capacitor 22, a second ceramic capacitor 23, and a third ceramic capacitor 24. The first ceramic capacitor 22 has a capacitance of 0.1μF, the second ceramic capacitor 23 has a capacitance of 1μF, and the third ceramic capacitor 24 has a capacitance of 10μF. The three are connected in parallel to form a wideband filter network.

[0028] The tantalum capacitor group 12 includes a first tantalum capacitor 25 and a second tantalum capacitor 26, both with a capacitance of 100μF, which are used to suppress low-frequency noise in the display driver module 2 and the backlight driver module 3, respectively.

[0029] The signal shielding and impedance matching module 6 includes a metal shield 13, a differential signal line group 14, and a matching resistor group 15. The differential signal line group 14 connects the display driver module 2 to the external FPC interface 16. The metal shield 13 covers the differential signal line group 14 and is connected to the ground layer 17 of the PCB substrate 1. The matching resistor group 15 is connected in series across the two ends of the differential signal line group 14.

[0030] In the signal shielding and impedance matching module 6, the differential signal line group 14 uses two pairs of AWG30 differential lines to connect the RGB differential pins of the display driver module 2 to the external FPC interface 16. The metal shielding cover 13 has a U-shaped structure, is made of tin-phosphor bronze, is 0.2mm thick, and has a 5μm thick conductive silver paste coating on its inner wall. Four soldering feet are provided at the bottom, which are soldered to the grounding pad on the PCB substrate 1, making the metal shielding cover 13 conductive with the ground layer 17. In the matching resistor group 15, the first matching resistor 27 and the second matching resistor 28 are both 100Ω / 0402 packages, connected in series with the positive and negative lines of the differential signal line group 14 near the external FPC interface 16.

[0031] The matching resistor group 15 includes a first matching resistor 27 and a second matching resistor 28, both with a resistance of 100Ω. They are connected in series in the positive and negative lines of the differential signal line group 14 to achieve 50Ω impedance matching.

[0032] The metal shield 13 is made of tin phosphor bronze, with the inner wall coated with conductive silver paste, and the bottom is provided with solder feet to connect with the grounding pad of the PCB substrate 1.

[0033] The layout isolation module 7 includes a physical isolation strip 18, a grounding via array 19, and a shielding baffle 20. The physical isolation strip 18 is filled with grounding copper foil 21. The grounding via array 19 is evenly distributed on both sides of the physical isolation strip 18 and is connected to the grounding layer 17. The shielding baffle 20 is vertically fixed above the physical isolation strip 18 and welded to the grounding copper foil 21.

[0034] In the layout isolation module 7, a physical isolation strip 18 is disposed on the surface of the PCB substrate 1 between the display driver module 2 and the backlight driver module 3, with a width of 2.5mm. It is filled with a complete grounding copper foil 21, which is connected to the ground layer 17. The grounding via array 19 consists of two rows of 0.3mm diameter vias located on both sides of the physical isolation strip 18, with a hole spacing of 0.5mm. The inner walls of the vias are plated with copper and are conductive to the ground layer 17. The shielding baffle 20 is made of 0.1mm thick brass sheet, bent into an L-shape, with a vertical height of 3mm. Its bottom is fixed to the grounding copper foil 21 of the physical isolation strip 18 by wave soldering.

[0035] The physical isolation strip 18 is 2-3mm wide, and the grounding via array 19 has a hole spacing of 0.5mm and a hole diameter of 0.3mm.

[0036] The LCM module was tested in an environment with an electromagnetic interference field strength of 10V / m (80MHz-1GHz). The test results showed that the display screen had no noise, horizontal lines, or flickering. The power supply voltage fluctuation was ±0.04V, the differential signal reflection coefficient was -27dB, and the interference coupling attenuation between the display driver module and the backlight driver module was 65dB, which fully meets the automotive electromagnetic compatibility standard (ISO 11452-2).

[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An anti-interference device for a liquid crystal display module PCB board, comprising a PCB substrate (1), wherein a display driving module (2), a backlight driving module (3), and a power input interface (4) are integrated on the PCB substrate (1), characterized in that, The PCB substrate (1) is provided with a multi-stage power filtering module (5), a signal shielding and impedance matching module (6) and a layout isolation module (7); the multi-stage power filtering module (5) is connected between the power input interface (4) and the display driver module (2) and the backlight driver module (3); the signal shielding and impedance matching module (6) is connected between the display driver module (2) and the external FPC interface (16); and the layout isolation module (7) is located between the display driver module (2) and the backlight driver module (3).

2. The anti-interference device for a liquid crystal display module PCB board according to claim 1, characterized in that, The multi-stage power filtering module (5) includes a common-mode inductor (8), a first differential-mode inductor (9), a second differential-mode inductor (10), a ceramic capacitor bank (11), and a tantalum capacitor bank (12). The input terminal of the common-mode inductor (8) is connected to the power input interface (4), and the output terminal of the common-mode inductor (8) is connected to the first differential-mode inductor (9) and the second differential-mode inductor (10) respectively. The output terminal of the first differential-mode inductor (9) is connected to the power supply terminal of the display driver module (2), and the output terminal of the second differential-mode inductor (10) is connected to the power supply terminal of the backlight driver module (3).

3. The anti-interference device for a liquid crystal display module PCB board according to claim 2, characterized in that, The ceramic capacitor bank (11) is connected in parallel between the output terminal of the common mode inductor (8) and ground, and the tantalum capacitor bank (12) is connected in parallel between the output terminal of the first differential mode inductor (9) and ground, and between the output terminal of the second differential mode inductor (10) and ground.

4. The anti-interference device for a liquid crystal display module PCB board according to claim 3, characterized in that, The ceramic capacitor bank (11) includes a first ceramic capacitor (22), a second ceramic capacitor (23), and a third ceramic capacitor (24), which are connected in parallel to form a wideband filter network.

5. The anti-interference device for a liquid crystal display module PCB board according to claim 3, characterized in that, The tantalum capacitor bank (12) includes a first tantalum capacitor (25) and a second tantalum capacitor (26).

6. The anti-interference device for a liquid crystal display module PCB board according to claim 1, characterized in that, The signal shielding and impedance matching module (6) includes a metal shield (13), a differential signal line group (14), and a matching resistor group (15). The differential signal line group (14) connects the display driver module (2) to the external FPC interface (16). The metal shield (13) covers the differential signal line group (14) and is connected to the ground layer (17) of the PCB substrate (1). The matching resistor group (15) is connected in series at both ends of the differential signal line group (14).

7. The anti-interference device for a liquid crystal display module PCB board according to claim 6, characterized in that, The matching resistor group (15) includes a first matching resistor (27) and a second matching resistor (28), which are connected in series in the positive and negative lines of the differential signal line group (14).

8. The anti-interference device for a liquid crystal display module PCB board according to claim 6, characterized in that, The metal shield (13) is made of tin phosphor bronze, with conductive silver paste coated on the inner wall, and welding feet at the bottom connected to the grounding pad of the PCB substrate (1).

9. The anti-interference device for a liquid crystal display module PCB board according to claim 1, characterized in that, The layout isolation module (7) includes a physical isolation strip (18), a grounding via array (19), and a shielding baffle (20). The physical isolation strip (18) is filled with grounding copper foil (21). The grounding via array (19) is evenly distributed on both sides of the physical isolation strip (18) and communicates with the grounding layer (17). The shielding baffle (20) is vertically fixed above the physical isolation strip (18) and welded to the grounding copper foil (21).

10. The anti-interference device for a liquid crystal display module PCB board according to claim 9, characterized in that, The width of the physical isolation strip (18) is 2-3 mm, and the hole spacing of the grounding via array (19) is 0.5 mm and the hole diameter is 0.3 mm.

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