Shielding protection structure of low-noise DC amplifier

Abstract

The utility model discloses a shielding protection structure of low noise direct current amplifier, including core amplification module circuit board, signal conditioning module circuit board, guard ring and double -deck high magnetic permeability shielding casing. The most peripheral of signal conditioning module circuit board is provided with guard ring, and is separately encapsulated in first layer high magnetic permeability shielding casing, and is welded after fixed with core amplification module circuit board and is connected. The most peripheral of core amplification module circuit board also is provided with guard ring, and the second layer high magnetic permeability shielding casing is again established to the whole module periphery. The guard ring plays electric field protection and leakage current shunt effect, and the double -deck high magnetic permeability shielding casing plays low -frequency magnetic field absorption effect. The cooperation of both, can improve the low noise performance and electromagnetic compatibility performance of amplifier in the wide frequency band range. The utility model discloses the cooperative protection design of guard ring and double -deck high magnetic permeability shielding, has improved the anti -interference ability of low noise direct current amplifier under the complex electromagnetic environment, especially is suitable for precision low electric signal measurement.

Description

Technical Field

[0001] This utility model relates to the field of electromagnetic protection and low-noise circuit structure design, specifically to a shielding protection structure for a low-noise DC amplifier. Background Technology

[0002] Low-noise amplifiers are widely used in precision measurement, standard transmission, and weak signal detection. Amplifier circuits, especially the input stage, are typically in a high-impedance state, making them highly susceptible to interference from leakage current on the circuit board surface, electric field coupling, and external magnetic fields. These interferences not only affect the input signal path but also impact overall performance through mutual coupling on the circuit board surface or between modules, thus reducing measurement accuracy.

[0003] Existing technologies typically reduce electromagnetic interference by using metal shielding shells, but have limited effect on suppressing leakage current on the circuit board surface; circuit board retaining rings can significantly reduce leakage current and parasitic coupling at the input end, but their electromagnetic shielding effect on the overall circuit is insufficient; while high permeability materials mainly suppress electromagnetic interference by absorbing losses in the low-frequency range, but their permeability decreases in the high-frequency range, and their shielding effect is significantly reduced. Utility Model Content

[0004] The purpose of this invention is to provide a shielding protection structure for a low-noise amplifier to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This utility model includes a signal conditioning module circuit board, a core amplification module circuit board, an inner shielding shell, and an outer shielding shell. The signal conditioning module circuit board has a first guard ring around its periphery, and the core amplification module circuit board has a second guard ring around its periphery. Both the first and second guard rings are continuously closed conductive rings and are grounded at a single point. The signal conditioning module circuit board is encapsulated within an inner shielding shell made of a high-permeability material. The inner and outer shielding shells are electrically isolated from each other by an insulating mounting component. The outer shielding shell is also made of a high-permeability material, forming a double-layer shielding structure. The signal conditioning module circuit board and the core amplification module circuit board are electrically connected through a connector penetrating the inner shielding shell, maintaining the electromagnetic continuity of the inner shielding shell.

[0007] Furthermore, the width of both the first guard ring and the second guard ring is more than twice the width of the thinnest signal trace on the circuit board, in order to increase the shunting capability of leakage current.

[0008] Furthermore, the first and second retaining rings are formed by one or more combinations of annular copper foil, metal foil, or conductive plating on the PCB surface / inner layer.

[0009] Furthermore, the wall thickness of both the inner and outer shielding shells is ≥1 mm to ensure sufficient absorption and loss of low-frequency magnetic fields.

[0010] Furthermore, the high magnetic permeability material is a nickel-iron permalloy or silicon steel sheet with a relative magnetic permeability μr ≥ 2000.

[0011] Furthermore, the signal conditioning module circuit board is fixed to the bottom plate of the inner shielding housing by insulating pillars, and input terminals are also soldered on the signal conditioning module circuit board.

[0012] Furthermore, the input terminal extends through the side wall of the inner shielding housing to the outside of the housing in order to connect to an external signal line. A first insulating sleeve is provided at the contact position between the input terminal and the perforation of the inner shielding housing.

[0013] Furthermore, the outer shielding housing cover plate is provided with zero adjustment holes and functional holes, and the inner wall of each hole is embedded with a second insulating sleeve to electrically isolate the zero adjustment potentiometer, output terminal, feedback terminal and power supply terminal protruding from the housing from the housing.

[0014] Furthermore, a conductive rubber ring is also installed between the outer shielding shell cover plate and the bottom plate to form a continuous electromagnetic seal.

[0015] Furthermore, the first grounding point of the first retaining ring and the second grounding point of the second retaining ring are connected at a single point in the star grounding point to avoid ground loop coupling noise.

[0016] The beneficial effects of this invention are as follows: Through the synergistic effect of the retaining ring and the multi-layer shielding shell, this invention achieves comprehensive protection against leakage current, parasitic coupling, and wide-band electromagnetic interference on the circuit board surface at both the circuit board level and the structural level, thereby improving the stability and anti-interference performance of the low-noise amplifier. Compared with the prior art, this structure not only effectively covers the input stage circuit but also provides additional protection for the overall circuit, significantly improving the noise performance of the amplifier. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall assembly of this utility model;

[0018] Figure 2 This is a circuit board view of the present invention.

[0019] Figure 3 This is a schematic diagram of the assembly of the inner shielding shell of this utility model;

[0020] Figure 4 This is a schematic diagram of the assembly of the outer shielding shell of this utility model;

[0021] In the diagram, 1. Signal conditioning module circuit board; 2. Input terminal; 3. First guard ring; 4. Grounding point; 5. Inner shielding shell; 6. First insulating sleeve; 7. Insulating support; 8. Core amplifier module circuit board; 9. Output terminal; 10. Feedback terminal; 11. Zero adjustment potentiometer; 12. Power terminal; 13. Second guard ring; 14. Grounding point; 15. Fixing hole; 16. Insulating mounting component; 17. Connector; 18. Outer shielding shell base plate; 19. Cover plate; 20. Zero adjustment hole; 21. Functional hole; 22. Second insulating sleeve. Detailed Implementation

[0022] The shielding protection structure of the low-noise DC amplifier of this utility model will be further described in detail below with reference to the accompanying drawings. This embodiment is only used to explain this utility model and is not intended to limit the scope of protection of this utility model.

[0023] The overall concept of this application is to simultaneously suppress surface leakage current, parasitic coupling, and broadband electromagnetic interference by incorporating a guard ring and a double-layer shielding structure at both the overall circuit and the input stage. The guard ring is a conductive ring surrounding the circuit board, forming a continuous closed loop around the sensitive circuit area to suppress leakage current and parasitic coupling of the electric field on the circuit board surface. The guard ring is grounded at a predetermined location using a single-point method to prevent circulating current from forming inside it. The double-layer shielding structure includes an inner shielding shell and an outer shielding shell. The inner shielding shell covers the signal conditioning circuit board, and the outer shielding shell covers the entire amplifier.

[0024] See Figures 1 to 4 As shown, the shielding protection structure of a low-noise DC amplifier in this embodiment mainly includes a signal conditioning module circuit board 1, an inner shielding shell 5, a core amplification module circuit board 8, an outer shielding shell base plate 18, and an outer shielding shell cover plate 19.

[0025] like Figure 2 As shown, input terminals 2 are soldered onto the signal conditioning module circuit board 1. A first guard ring 3 is formed around the outermost edge of the circuit board 1 using PCB trace technology. This first guard ring forms a continuous closed rectangular loop to collect and shunt leakage current from the circuit board surface. The first guard ring 3 is connected to the system's common ground terminal at a predetermined first grounding point 4 via PCB traces to avoid ground loop interference.

[0026] The signal conditioning module circuit board is entirely encapsulated within an inner shielding housing 5 made of a high-permeability material. The input terminal 2 extends through the side wall of the inner shielding housing 5 to the outside of the housing for connection to external signal lines. A first insulating sleeve 6 is provided at the contact position between the input terminal 2 and the perforation in the inner shielding housing 5, see... Figure 3This ensures electrical isolation between the input terminal 2 and the inner shielding housing 5. The signal conditioning module circuit board 1 is fixed to the base plate of the inner shielding housing 5 by insulating supports 7.

[0027] The core amplifier module circuit board 8 is equipped with output terminals 9, feedback terminals 10, a zero-adjustment potentiometer 11, and power supply terminals 12. Similarly, a second guard ring 13 is formed around the outermost edge of the core amplifier module circuit board 8 using PCB traces. This second guard ring 13 also forms a closed loop and is connected to the system common ground terminal at another predetermined grounding point 14 via a single trace.

[0028] Furthermore, the width of the first and second guard rings is more than twice the width of the trace, in order to more effectively disperse the leakage current.

[0029] Furthermore, the retaining ring can be made of, but is not limited to, annular copper foil, metal foil, conductive plating, or other forms of annular conductors on the PCB surface / inner layer. Different forms of retaining rings can achieve the same technical effect, namely, suppressing leakage current and parasitic coupling at the circuit board level.

[0030] The core amplification module circuit board 8 has mounting holes 15 at its four corners. An insulating mounting piece 16 is installed in each mounting hole 15.

[0031] like Figure 1 As shown, the signal conditioning module circuit board 1 and the core amplification module circuit board 8 are electrically connected via a connector 17. This connector 17 passes through a reserved hole in the inner shielding shell 5, enabling signal transmission between the inner and outer modules while maintaining the electromagnetic continuity of the inner shielding shell 5.

[0032] Finally, the assembled core amplification module circuit board 8 and the signal conditioning module circuit board 1 encapsulated within the inner shielding shell 5 are assembled as a whole and installed into a larger outer shielding shell. The outer shielding shell consists of an outer shielding shell base plate 18 and an outer shielding shell cover plate 19, both made of high-permeability material. The outer shielding shell base plate 18 has holes corresponding to the fixing holes 15 on the core amplification module circuit board 8. Through the insulating mounting component 16, the core amplification module circuit board 8 and the outer shielding shell base plate 18 are electrically isolated and fixed, ensuring both mechanical strength and electrical insulation between the circuit board and the shielding shell.

[0033] Furthermore, the shielding shell made of high-permeability ferromagnetic material can weaken the interference of external magnetic and electric fields on the internal circuit. The high-permeability material is a nickel-iron permalloy or silicon steel sheet with a relative permeability μr ≥ 2000.

[0034] like Figure 4As shown, the outer shielding shell bottom plate 18 and the outer shielding shell cover plate 19 are tightened and fixed by insulating mounting parts 16 to form a complete second shielding cavity.

[0035] To facilitate debugging and external connections, several holes are provided on the outer shielding shell cover plate 19:

[0036] Zero adjustment hole 20: corresponds to the zero adjustment potentiometer 11 on the core amplification module circuit board 8, allowing the operation of the command by inserting a small screwdriver without opening the shielding shell.

[0037] Functional holes 21: corresponding to output terminal 9, feedback terminal 10 and power terminal 12. These holes are provided with second insulating sleeves 21, allowing the corresponding terminals to extend or wires to pass through, and maintaining insulation from the housing at the passage points.

[0038] In the low-frequency band, ferromagnetic materials can enhance the absorption loss of electromagnetic interference and reduce the intensity of external magnetic fields entering the internal circuit. In the high-frequency band, multi-layer shielding structures utilize interlayer isolation and multiple reflection losses to further suppress electromagnetic interference. By combining inner and outer double-layer shielding, both the absorption loss of low-frequency interference and the reflection loss of high-frequency interference can be taken into account, thereby achieving comprehensive protection against broadband electromagnetic interference.

[0039] Furthermore, the thickness of the shielding shell is selected to be no less than 1 mm to ensure sufficient absorption loss and shielding effect. The thickness of the shielding layer has a significant impact on the shielding effect. The thicker the shielding layer, the greater its absorption loss of electromagnetic energy, especially in the low-frequency band, where a thicker shielding shell can significantly improve its absorption loss of magnetic fields. In one embodiment, the thickness of the shielding shell is selected to be no less than 1 mm to ensure sufficient absorption loss and shielding effect.

[0040] In this embodiment, leakage current and electric field interference on the circuit board surface are collected and shunted to ground through the first guard ring 3 and the second guard ring 13, preventing them from entering the amplifier circuit and causing noise. This protective design in this embodiment greatly improves the signal-to-noise ratio and stability of the low-noise DC amplifier in complex electromagnetic environments.

[0041] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model.

Claims

1. A shielding protection structure for a low-noise DC amplifier, characterized in that: The system includes a signal conditioning module circuit board (1), a core amplification module circuit board (8), an inner shielding shell (5), and an outer shielding shell. The signal conditioning module circuit board (1) is provided with a first guard ring (3) on its periphery, and the core amplification module circuit board (8) is provided with a second guard ring (13) on its periphery. The first guard ring (3) and the second guard ring (13) are both continuous closed conductive rings and are grounded at a single point. The signal conditioning module circuit board (1) is encapsulated in an inner shielding shell (5) made of high magnetic permeability material. The inner shielding shell (5) and the outer shielding shell are electrically isolated by an insulating mounting component (16). The outer shielding shell is also made of high magnetic permeability material, forming a double-layer shielding structure. The signal conditioning module circuit board (1) and the core amplification module circuit board (8) are electrically connected by a connector (17) that penetrates the inner shielding shell (5) and maintains the electromagnetic continuity of the inner shielding shell (5).

2. The shielding protection structure according to claim 1, characterized in that: The width of the first guard ring (3) and the second guard ring (13) is more than twice the width of the thinnest signal trace on the circuit board, so as to increase the shunting capability of leakage current.

3. The shielding protection structure according to claim 1 or 2, characterized in that: The first retaining ring (3) and the second retaining ring (13) are formed by one or more combinations of annular copper foil, metal foil or conductive plating layer of PCB surface / inner layer.

4. The shielding protection structure according to claim 1, characterized in that: The inner shielding shell (5) and the outer shielding shell both have a wall thickness of ≥1 mm to ensure sufficient absorption loss of low-frequency magnetic fields.

5. The shielding protection structure according to claim 1 or 4, characterized in that: The high permeability material is a nickel-iron permalloy or silicon steel sheet with a relative permeability μr ≥ 2000.

6. The shielding protection structure according to claim 1, characterized in that: The signal conditioning module circuit board (1) is fixed to the bottom plate of the inner shielding shell (5) by an insulating support (7), and an input terminal (2) is also soldered on the signal conditioning module circuit board (1).

7. The shielding protection structure according to claim 6, characterized in that: The input terminal (2) extends through the side wall of the inner shield housing (5) to the outside of the housing so as to connect to the external signal line. A first insulating sleeve (6) is provided at the contact position between the input terminal (2) and the perforation of the inner shield housing (5).

8. The shielding protection structure according to claim 1, characterized in that: The outer shielding shell cover plate (19) of the outer shielding shell is provided with a zero adjustment hole (20) and a functional hole (21). The inner wall of each hole is embedded with a second insulating sleeve (22) so that the zero adjustment potentiometer (11), output terminal (9), feedback terminal (10) and power supply terminal (12) extending out of the shell are electrically isolated from the shell.

9. The shielding protection structure according to claim 1 or 8, characterized in that: A conductive rubber ring is also installed between the outer shielding shell cover plate (19) and the outer shielding shell bottom plate (18) to form a continuous electromagnetic seal.

10. The shielding protection structure according to claim 1, characterized in that: The first grounding point (4) of the first guard ring (3) and the second grounding point (14) of the second guard ring (13) are connected at a single point in the star grounding point to avoid ground loop coupling noise.

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