Composite shielding anti-interference filter circuit for cross-board sampling

Abstract

The utility model provides a composite shielding anti-interference filter circuit aiming at cross-board sampling, which solves the problems that the signal acquisition of the traditional isolation sampling scheme is easily interfered, the sampling accuracy is easily reduced, the anti-EMC performance level of the product is reduced and the like, and the scheme comprises at least two circuit boards, the plurality of circuit boards are electrically connected through the connectors in sequence; the head end circuit board is provided with a sampling circuit and an RC filter circuit which are electrically connected in sequence, the tail end circuit board is provided with a magnetic bead filter circuit, an operation buffer circuit and a chip which are electrically connected in sequence, and the multiple circuit boards between the head end and the tail end are respectively provided with a magnetic bead filter circuit so as to be electrically connected with corresponding connectors at the two ends of the magnetic bead filter circuits. When a sampling signal enters a rear-end circuit through the terminal, the sampling signal is filtered by the RC filter circuit, and after RC filter output, the sampling signal passes through the inter-board connector, reaches a second board, then immediately passes through the magnetic bead until being transmitted to the magnetic bead of a tail-end circuit board, and finally is transmitted to a chip after being buffered by the operational amplifier.

Description

Technical Field

[0001] This utility model relates to communication sampling circuits, and more particularly to a composite shielded anti-interference filtering circuit for cross-board sampling. Background Technology

[0002] Currently, sampling circuits in the communications industry are broadly classified into two sampling schemes: basic voltage divider sampling and isolated sampling. The basic voltage divider sampling scheme primarily uses a voltage divider resistor network + operational amplifier buffer + low-precision ADC. The circuit flow is: Vin → (R1 / / C1)-(R2 / / C2) voltage divider → voltage follower → ADC / MCU. The isolated sampling scheme mainly uses magnetic isolation or optocoupler isolation devices (such as ADI and ADuM series), adding digital isolators to block ground potential differences and configuring instrumentation amplifiers to suppress common-mode interference.

[0003] Both of these schemes require the sampling path to be as short as possible, separating analog and digital data to ensure sampling accuracy. Therefore, they have the following limitations:

[0004] 1. When the sampling signal crosses boards, the above two schemes are susceptible to interference, which reduces the sampling accuracy and leads to a decrease in the product's own EMC resistance level;

[0005] 2. The basic voltage divider sampling scheme has poor common-mode interference immunity, and the lack of isolation design makes the grounding loop susceptible to interference;

[0006] 3. Isolated sampling schemes introduce additional nonlinear errors (typically ±0.1% gain error), increase circuit complexity (requires isolated power supply), and raise costs (compared to basic schemes). Utility Model Content

[0007] The technical problem to be solved by this utility model is to overcome the defects of the existing technology. This utility model proposes a composite shielded anti-interference filter circuit for cross-board sampling, which improves accuracy and anti-interference ability compared with the basic solution. At the same time, it can perform high anti-interference processing on cross-board sampling signals and has a lower cost.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a composite shielded anti-interference filter circuit for cross-board sampling, comprising:

[0009] At least two circuit boards, and the multiple circuit boards are electrically connected in sequence via connectors;

[0010] The first circuit board has a sampling circuit and an RC filter circuit connected in sequence. The last circuit board has a ferrite bead filter circuit, an operational buffer circuit, and a chip connected in sequence. Ferrite bead filter circuits are provided on multiple circuit boards between the first and last ends and are electrically connected to their corresponding connectors at both ends. When the sampling signal enters the back-end circuit through the terminal, it is filtered by the RC filter circuit. After the RC filter output, it passes through the inter-board connector to the second board and immediately passes through the ferrite bead until it is transmitted to the ferrite bead on the last circuit board. Finally, it is buffered by the operational amplifier and transmitted to the chip.

[0011] Furthermore, an isolation device may be provided on the circuit board at the first end between the sampling circuit and the RC filter circuit, with the RC filter circuit located after the isolation device.

[0012] Furthermore, on the circuit board at the end, the sampling signal can undergo an additional RC filter before entering the chip.

[0013] Furthermore, in the sampling circuit, one end of the inductor is connected to the RC filter circuit, and the other end is connected to an external common port.

[0014] Furthermore, the RC filter circuit includes a first resistor, a second resistor, a first capacitor, and a second capacitor. One end of the first resistor is connected to the corresponding pin of the inductor, and the other end is connected in series with the second resistor. The first capacitor and the second capacitor are connected in parallel on the RC filter circuit and grounded synchronously. The second resistor is not soldered.

[0015] Furthermore, in the ferrite bead filter circuit, the distance between the ferrite bead and the corresponding connector is set to be less than 5mm.

[0016] Furthermore, the operational buffer circuit includes an operational amplifier and a diode. One end of the operational amplifier is connected to the chip, and the other end is electrically connected to the ferrite bead. The same end is grounded through the diode.

[0017] Compared with the prior art, the beneficial effects of this utility model include: the sampling signal can be filtered once by the RC filter circuit on the first board, and then multiple cross-board signal transmissions are realized by ferrite beads and connectors. The ferrite beads can suppress high-frequency noise and spike interference on signal lines and power lines, and also have the ability to absorb electrostatic pulses. Simultaneously on the last board, the output sampling signal is also buffered by an operational amplifier, and then undergoes another RC filter before entering the MCU / AD chip. This can provide high immunity to interference for cross-board sampling signals. Compared with the traditional isolated sampling scheme, the circuit design is simpler and the cost is lower. Attached Figure Description

[0018] The disclosure of this utility model is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this utility model. In the drawings, the same reference numerals are used to refer to the same parts. Wherein:

[0019] Figure 1 The schematic diagram illustrates the principle of a two-board cross-board circuit according to one embodiment of the present invention.

[0020] Figure 2 The schematic diagram illustrates the principle of a three-board cross-board circuit according to one embodiment of the present invention.

[0021] Figure 3 The schematic diagram illustrates the principle of a three- or more board-to-board circuit according to one embodiment of the present invention.

[0022] Figure 4 The schematic diagram shows a sampling circuit schematic according to one embodiment of the present invention;

[0023] Figure 5 The diagram schematically illustrates an RC filter circuit according to one embodiment of the present invention.

[0024] Figure 6 The schematic diagram shows a magnetic bead filter circuit diagram according to one embodiment of the present invention;

[0025] Figure 7 The diagram schematically illustrates an operational buffer circuit according to one embodiment of the present invention. Detailed Implementation

[0026] It is readily understood that, based on the technical solution of this utility model, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of this utility model. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative descriptions of the technical solution of this utility model and should not be considered as the entirety of this utility model or as limitations or restrictions on the technical solution of this utility model.

[0027] According to one embodiment of the present invention, in conjunction with Figures 1-7 As shown.

[0028] like Figures 1-3 As shown, in this embodiment, a composite shielded anti-interference filter circuit for cross-board sampling includes the following components for the overall circuit structure:

[0029] At least two circuit boards, and the multiple circuit boards are electrically connected in sequence via connectors;

[0030] The first circuit board has a sampling circuit and an RC filter circuit connected in sequence. The last circuit board has a ferrite bead filter circuit, an operational buffer circuit, and a chip connected in sequence. Ferrite bead filter circuits are provided on multiple circuit boards between the first and last ends and are electrically connected to their corresponding connectors at both ends. When the sampling signal enters the back-end circuit through the terminal, it is filtered by the RC filter circuit. After the RC filter output, it passes through the inter-board connector to the second board and immediately passes through the ferrite bead until it is transmitted to the ferrite bead on the last circuit board. Finally, it is buffered by the operational amplifier and transmitted to the chip.

[0031] This filter sampling circuit design mainly includes a sampling circuit, an RC filter circuit, a ferrite bead filter circuit, and an operational buffer circuit. For different cross-board solutions, such as... Figures 1-3 As shown, they can be roughly divided into two types: sampling cross-board scheme between two boards and sampling cross-board scheme between three or more boards.

[0032] Two-board sampling scheme: The sampling signal input and the MCU / AD chip are on different boards. In this case, when the sampling signal enters the back-end circuit through the terminals, it immediately passes through a first-stage RC filter. If an isolation device is present, the RC filter is placed after the isolation device. After RC filtering, the output signal passes through the inter-board connector to the second board and immediately passes through a ferrite bead. The output sampling signal is then buffered by an operational amplifier and passes through another stage of RC filtering before entering the MCU / AD chip. The sampling signal flow must ensure a complete ground plane and consistent impedance.

[0033] Sampling schemes with three or more boards: The positions of the RC filter, operational amplifier, and MCU are the same as in the two-board sampling scheme. The only difference is that the position and number of ferrite beads must correspond to the number of boards. If there are N boards, add N-1 more ferrite beads, passing through the ferrite beads from the second sampling board to the connector position of the Nth sampling board. The sampling signal flow must ensure a complete ground plane and consistent impedance.

[0034] Regarding the specific circuit structure involved, such as Figures 4-7 As shown:

[0035] For the sampling circuit, Figure 4 In the sampling circuit described above, one end of the inductor is connected to the RC filter circuit, and the other end is connected to an external common port.

[0036] Figure 5 The RC filter circuit in the figure includes a first resistor, a second resistor, a first capacitor, and a second capacitor. One end of the first resistor is connected to the corresponding pin of the inductor, and the other end is connected in series with the second resistor. The first capacitor and the second capacitor are connected in parallel on the RC filter circuit and grounded synchronously. The second resistor is not soldered.

[0037] Figure 6In the ferrite bead filter circuit described above, the distance between the ferrite bead and the corresponding connector is set to be less than 5mm.

[0038] Figure 7 The operational buffer circuit in the circuit includes an operational amplifier and a diode. One end of the operational amplifier is connected to the chip, and the other end is electrically connected to the ferrite bead. The same end is grounded through the diode.

[0039] The sampling signal can be filtered once by the RC filter circuit on the first board. Then, multiple cross-board signal transmissions are achieved by ferrite beads and connectors. Ferrite beads can suppress high-frequency noise and spike interference on signal lines and power lines, and also have the ability to absorb electrostatic pulses. Synchronously on the last board, the output sampling signal is buffered by an operational amplifier and then undergoes another RC filter before entering the MCU / AD chip. This can provide high immunity to cross-board sampling signals. Compared with traditional isolated sampling schemes, the circuit design is simpler and the cost is lower.

[0040] The technical scope of this utility model is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this utility model, and all such modifications and variations should fall within the protection scope of this utility model.

Claims

1. A composite shielded anti-jam filter circuit for across-board sampling, characterized by, The application relates to a circuit board assembly. The first circuit board is provided with a sampling circuit and an RC filter circuit connected in sequence, the last circuit board is provided with a magnetic bead filter circuit, an operation buffer circuit and a chip connected in sequence, and the magnetic bead filter circuit is arranged on each of the circuit boards between the first circuit board and the last circuit board and is connected with the corresponding connectors at both ends. An isolating device can be arranged between the sampling circuit and the RC filter circuit on the first circuit board.

2. The composite shielded anti-jam filter circuit for cross-board sampling of claim 1, wherein: The sampling signal can pass through a one-stage RC filter before entering the chip on the last circuit board.

3. The composite shielded anti-jam filter circuit for cross-board sampling of claim 1, wherein: One end of the inductor in the sampling circuit is connected with the RC filter circuit, and the other end is connected with an external common port.

4. The composite shielded anti-jam filter circuit for cross-board sampling of claim 1, wherein: The RC filter circuit comprises a first resistor, a second resistor, a first capacitor and a second capacitor, one end of the first resistor is connected with the corresponding pin of the inductor, the other end is connected with the second resistor in series, the first capacitor and the second capacitor are connected in parallel on the RC filter circuit and are grounded synchronously, and the second resistor is not welded.

5. The composite shielded anti-jam filter circuit for cross-board sampling of claim 4, wherein: In the magnetic bead filter circuit, the distance between the magnetic bead and the corresponding connector is less than 5mm.

6. The composite shielded anti-jam filter circuit for cross-board sampling of claim 1, wherein: The operation buffer circuit comprises an operational amplifier and a diode, one end of the operational amplifier is connected with the chip, the other end is connected with the magnetic bead, and the same end is grounded through the diode.

7. The composite shielded anti-jam filter circuit for cross-board sampling of claim 6, wherein: ​

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