Power frequency interference shielding circuit

Abstract

The utility model provides a power frequency interference shielding circuit which comprises an isolation power supply module, a positive voltage conversion module, a negative voltage conversion module and a power amplifier module. The output end of the isolated power supply module is connected with the input ends of the positive voltage conversion module and the negative voltage conversion module respectively; the output end of the isolated power supply module is connected in series with a common mode inductor, and the output of the common mode inductor is connected with the input ends of the positive voltage conversion module and the negative voltage conversion module respectively; the positive voltage conversion module and the negative voltage conversion module output converted voltage; and the power amplifier module receives the small signal, amplifies the small signal and outputs the amplified small signal. The output end of the isolation power supply module is connected in series with the common-mode inductor, so that common-mode interference signals can be effectively suppressed, and particularly, a good filtering effect on power frequency interference is achieved.

Description

Technical Field

[0001] This utility model relates to the field of interference shielding, specifically to a power frequency interference shielding circuit. Background Technology

[0002] With the rapid development of the Industrial Internet of Things (IIoT), high-power signal transmission plays a crucial role in industrial control, data acquisition, and other fields. However, in practical applications, power frequency interference remains a major challenge affecting signal quality. This type of interference not only causes signal distortion but also affects the accuracy of data acquisition, thereby reducing the reliability of the entire system.

[0003] Existing technologies typically employ various filters to suppress power frequency interference. While these traditional methods can reduce interference to some extent, they suffer from the following shortcomings: Traditional filter designs struggle to precisely match the specific frequency and intensity of power frequency interference, resulting in suboptimal filtering performance. Especially in complex and variable industrial environments, filters with fixed parameters are ill-suited to various interference scenarios. Ringing effects are prone to occur during filtering, causing signal waveform distortion. This distortion directly impacts the accuracy of subsequent data processing, which is unacceptable in high-precision industrial applications. The effectiveness of traditional filtering methods decreases significantly at high signal power. This is primarily because the impact of power frequency interference is more pronounced under high-power conditions, and conventional filters cannot effectively isolate interference signals of such intensity. Furthermore, while filtering out power frequency interference, traditional filtering methods often lead to attenuation of the useful signal, reducing the signal-to-noise ratio and affecting the overall system performance.

[0004] Therefore, there is an urgent need to develop a new type of anti-power frequency interference circuit to solve the interference problem in high-power signal transmission. Utility Model Content

[0005] The purpose of this invention is to solve the technical problem that high-power signal transmission in the Industrial Internet of Things is easily affected by power frequency interference, leading to signal distortion.

[0006] This utility model provides a power frequency interference shielding circuit, including an isolation power supply module, a positive voltage conversion module, a negative voltage conversion module, and a power amplifier module;

[0007] The output terminal of the isolated power supply module is connected to the input terminals of the positive voltage conversion module and the negative voltage conversion module, respectively.

[0008] The output of the isolated power supply module is connected in series with a common-mode inductor, and the output of the common-mode inductor is connected to the input of the positive voltage conversion module and the negative voltage conversion module, respectively.

[0009] The positive voltage conversion module and the negative voltage conversion module output the converted voltage;

[0010] The power amplifier module receives a small signal, amplifies the small signal, and then outputs it.

[0011] Furthermore, the isolated power supply module includes a power chip, the second pin of which is grounded and the third pin is connected to an external power supply terminal, and a first capacitor, a second capacitor and a third capacitor are connected in parallel between the second pin and the third pin;

[0012] The fourth pin of the power chip is the voltage output terminal, the fifth pin is grounded, and the fourth, fifth, sixth, seventh and eighth capacitors are connected in parallel between the fourth and fifth pins.

[0013] Furthermore, the common-mode inductor includes a first common-mode inductor and a second common-mode inductor;

[0014] The fourth pin of the power chip is connected to the power supply terminal through the first common-mode inductor, and the fifth pin is connected to the ground terminal through the second common-mode inductor.

[0015] Furthermore, the positive voltage conversion module includes a power conversion chip. The second pin of the power conversion chip is connected to an external power supply terminal, the fourth pin is connected to a voltage divider resistor, the twelfth pin is connected to the gate of the first NMOS transistor and the gate of the second NMOS transistor, the fourteenth pin is connected to the gate of the third NMOS transistor and the gate of the fourth NMOS transistor, and the thirteenth pin is connected to the drain of the first NMOS transistor and the third NMOS transistor, and the source of the second NMOS transistor and the fourth NMOS transistor.

[0016] Furthermore, the negative voltage conversion module includes a converter chip. The second pin of the converter chip is connected to ground via a first resistor in series; the third pin is connected to ground via a ninth capacitor, and simultaneously connected to a first inductor via a second resistor in series; the fourth pin is connected to ground via a tenth capacitor; the fifth pin is connected to ground via a third resistor in series; the sixth pin is connected to both an eleventh capacitor and a fourth resistor, with the other end of the eleventh capacitor grounded, and the other end of the fourth resistor connected to ground via a twelfth capacitor in series; the seventh pin is connected to both a fifth resistor and a sixth resistor, with one end of the fifth resistor connected to a second inductor in series, the second inductor connected to the anode of a diode and the twelfth capacitor, and the other end of the sixth resistor grounded; the eighth pin is connected to ground via a seventh resistor in series; the ninth pin is connected to ground via a thirteenth capacitor; the tenth pin is connected to ground via an eighth resistor in series; and the eleventh and twelfth pins are connected between the first inductor and the twelfth capacitor.

[0017] The five resistor is connected in parallel with the fourteenth capacitor. One end of the first inductor is connected to one end of the fifteenth, sixteenth, seventeenth, eighteenth, nineteenth and twentieth capacitors respectively, and the other end is grounded.

[0018] Furthermore, the power amplifier module includes:

[0019] The first-stage gain circuit includes a first operational amplifier and its feedback network;

[0020] The second-stage gain circuit includes a second operational amplifier and its feedback network;

[0021] A connecting resistor network is provided between the first-stage gain circuit and the second-stage gain circuit;

[0022] The first-stage gain circuit and the second-stage gain circuit are electrically connected to the output terminals of the positive voltage conversion module and the negative voltage conversion module, respectively.

[0023] Furthermore, the power supply ports of the first operational amplifier and the second operational amplifier are respectively equipped with decoupling capacitors.

[0024] Furthermore, the small signal input is transmitted using shielded cables to suppress power frequency interference signals.

[0025] Compared to existing technologies, this invention offers at least the following advantages: By employing a design combining an isolated power supply module and a power conversion module, electrical isolation of the power supply system is achieved, effectively blocking the conduction of power frequency interference through the power path and improving the system's anti-interference capability from the source. Connecting a common-mode inductor in series at the output of the isolated power supply module effectively suppresses common-mode interference signals, particularly providing excellent filtering for power frequency interference. Simultaneously, differential-mode signals are almost unaffected, ensuring the integrity of useful signals. The design of the positive-to-negative voltage conversion module enables the system to have bipolar power supply capability, expanding the dynamic range of signal processing, improving the system's ability to process large signals, and enhancing the circuit's anti-interference performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained as provided without creative effort.

[0027] Figure 1 This is a schematic diagram of a power frequency interference shielding circuit in one embodiment of the present invention;

[0028] Figure 2 This is a circuit diagram of the isolation power supply module in a power frequency interference circuit according to one embodiment of the present invention;

[0029] Figure 3 This is a circuit diagram of the positive voltage conversion module in a power frequency interference circuit according to one embodiment of the present invention;

[0030] Figure 4 This is a circuit diagram of the negative voltage conversion module in a power frequency interference circuit according to one embodiment of the present invention;

[0031] Figure 5 This is a circuit diagram of the power amplifier module in a power frequency interference circuit according to one embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of the transformer terminals in a power frequency interference circuit according to one embodiment of the present invention. Detailed Implementation

[0033] The present invention will now be described in more detail with reference to the accompanying drawings, which illustrate preferred embodiments of the present invention. It should be understood that those skilled in the art can modify the present invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being broadly known to those skilled in the art and is not intended to limit the present invention.

[0034] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0035] The present invention will be described in more detail below by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become clearer as will be explained below. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0036] This embodiment provides a power frequency interference shielding circuit. Please refer to [reference needed]. Figure 1 It includes an isolated power supply module, a positive voltage conversion module, a negative voltage conversion module, and a power amplifier module;

[0037] The output terminal of the isolated power supply module is connected to the input terminals of the positive voltage conversion module and the negative voltage conversion module, respectively.

[0038] The output of the isolated power supply module is connected in series with a common-mode inductor, and the output of the common-mode inductor is connected to the input of the positive voltage conversion module and the negative voltage conversion module, respectively.

[0039] The positive voltage conversion module and the negative voltage conversion module output the converted voltage;

[0040] The power amplifier module receives a small signal, amplifies the small signal, and then outputs it.

[0041] Specifically, in this embodiment, the isolation power supply module receives an externally input DC voltage and outputs a stable 12V DC voltage after isolation and voltage regulation. The positive voltage conversion module receives the 12V DC voltage and boosts it to +30V using a boost topology to provide positive power to the power amplifier; the negative voltage conversion module receives the 12V DC voltage and converts it to -30V using a flyback or charge pump topology to provide negative power to the power amplifier, ensuring the bidirectional swing capability of the output signal. In this embodiment, the negative voltage conversion module uses a flyback topology. The power amplifier module receives a small externally input signal and, combined with the ±30V power supply, amplifies the signal to output a high-current / high-voltage drive signal.

[0042] For further details, please refer to... Figure 2 The isolated power supply module includes a power chip, the second pin of which is grounded and the third pin is connected to an external power supply terminal. A first capacitor, a second capacitor, and a third capacitor are connected in parallel between the second pin and the third pin.

[0043] The fourth pin of the power chip is the voltage output terminal, the fifth pin is grounded, and the fourth, fifth, sixth, seventh and eighth capacitors are connected in parallel between the fourth and fifth pins.

[0044] Specifically, this isolated power supply module is based on an isolated DC-DC chip (URB2412 series) with a built-in transformer. Its core is to electrically isolate the input and output circuits through a high-frequency transformer. The first to third capacitors connected in parallel on the input side (pin 3 connects to the external power supply, pin 2 is grounded) use a combination of multiple capacitance values ​​to filter out low-frequency ripple and high-frequency noise, while providing instantaneous energy storage for the chip. The fourth to eighth capacitors connected in parallel on the output side (pin 4 is the voltage output, pin 5 is grounded) further suppress output ripple through graded filtering, ensuring voltage stability. Internally, the chip uses PWM to control the transformer's energy transfer, achieving efficient isolated conversion from input to output.

[0045] Furthermore, the common-mode inductor includes a first common-mode inductor and a second common-mode inductor;

[0046] The fourth pin of the power chip is connected to the power supply terminal through the first common-mode inductor, and the fifth pin is connected to the ground terminal through the second common-mode inductor.

[0047] Specifically, the first and second common-mode inductors are connected in series on the voltage output terminal (pin 4) and ground terminal (pin 5), respectively. Through a structure of symmetrical dual-winding wound around a high-permeability magnetic core, a high-impedance path is formed for common-mode noise. When common-mode interference current flows through the two windings, the magnetic fields within the core are superimposed, effectively doubling the inductance and suppressing common-mode noise. Meanwhile, the magnetic fields generated by the normal differential-mode current cancel each other out, resulting in extremely low impedance and ensuring efficient energy transfer.

[0048] For further details, please refer to... Figure 3 The positive voltage conversion module uses a power conversion chip of model MAX25201. The second pin of the power conversion chip is connected to the external power supply terminal, the fourth pin is connected to the voltage divider resistor, the twelfth pin is connected to the gate of the first NMOS transistor and the gate of the second NMOS transistor, the fourteenth pin is connected to the gate of the third NMOS transistor and the gate of the fourth NMOS transistor, and the thirteenth pin is connected to the drain of the first NMOS transistor and the third NMOS transistor and the source of the second NMOS transistor and the fourth NMOS transistor.

[0049] Specifically, after the external power supply is input through pin 2 (SUP), the high-frequency switching circuit inside the chip, together with the external inductor and capacitor, forms a switching power supply topology. Through periodic switching, electrical energy is stored in the inductor and released to the output. The voltage divider network connected to pin 4 (FB) samples the output voltage and feeds it back to the chip's internal error amplifier. After comparing it with the reference voltage, the switching duty cycle is dynamically adjusted, thereby precisely controlling the output voltage at pin 13 (VOUT). The resistance ratio of the voltage divider resistors directly determines the final output voltage value, while the inductor and capacitor are used to smooth current ripple and suppress high-frequency noise. The operation of the NMOS transistor is controlled through pins 12 and 14, ensuring that the NMOS transistor operates and outputs 30V when receiving either a high-level or low-level signal.

[0050] For further details, please refer to... Figure 4 The negative voltage conversion module includes a converter chip. The second pin of the converter chip is connected to ground via a first resistor in series; the third pin is connected to ground via a ninth capacitor, and simultaneously connected to a first inductor via a second resistor in series; the fourth pin is connected to ground via a tenth capacitor; the fifth pin is connected to ground via a third resistor in series; the sixth pin is connected to an eleventh capacitor and a fourth resistor, with the other end of the eleventh capacitor grounded, and the other end of the fourth resistor connected to ground via a twelfth capacitor in series; the seventh pin is connected to a fifth resistor and a sixth resistor, with one end of the fifth resistor connected to a second inductor in series, the second inductor connected to the positive terminal of a diode and the twelfth capacitor, and the other end of the sixth resistor grounded; the eighth pin is connected to ground via a seventh resistor in series; the ninth pin is connected to ground via a thirteenth capacitor; the tenth pin is connected to ground via an eighth resistor in series; and the eleventh and twelfth pins are connected between the first inductor and the twelfth capacitor.

[0051] The five resistor is connected in parallel with the fourteenth capacitor. One end of the first inductor is connected to one end of the fifteenth, sixteenth, seventeenth, eighteenth, nineteenth and twentieth capacitors respectively, and the other end is grounded.

[0052] Specifically, the input positive voltage is converted to a negative voltage through the energy storage and release of the first inductor. The first resistor on the second pin sets the chip's operating parameters, such as the switching frequency or current limiting threshold. The second resistor on the third pin and the ninth capacitor form an RC network to suppress switching node ringing and adjust the dead time; the first inductor stores energy during the chip's switching cycle and releases energy to the twelfth capacitor, which, together with the diode's unidirectional conduction, forms a negative voltage at the output; the fifth resistor, the sixth resistor, and the second inductor form an output filtering and feedback network, which dynamically adjusts the PWM duty cycle through voltage divider sampling to stabilize the output voltage; the multi-capacitor parallel design covers the 10Hz-100MHz frequency band, suppressing the output ripple to below 20mVpp.

[0053] For further details, please refer to... Figure 5 The power amplifier module includes:

[0054] The first-stage gain circuit includes a first operational amplifier and its feedback network;

[0055] The second-stage gain circuit includes a second operational amplifier and its feedback network;

[0056] A connecting resistor network is provided between the first-stage gain circuit and the second-stage gain circuit;

[0057] The first-stage gain circuit and the second-stage gain circuit are electrically connected to the output terminals of the positive voltage conversion module and the negative voltage conversion module, respectively.

[0058] Specifically, this module employs a two-stage operational amplifier architecture to achieve high-precision signal amplification. The first-stage gain circuit is typically configured as a low-noise, high-input-impedance non-inverting / inverting amplifier, with the primary gain set via a feedback network to suppress high-frequency noise in the input signal. The second-stage gain circuit is designed as a high-slew-rate, high-current output buffer or gain stage, whose feedback network expands the total gain while driving low-impedance loads. Interstage resistor networks achieve impedance matching and DC bias isolation, preventing interstage coupling oscillations. Symmetrical positive / negative power supplies ensure maximum output dynamic range and eliminate crossover distortion caused by a single power supply.

[0059] Furthermore, the power supply ports of the first operational amplifier and the second operational amplifier are respectively equipped with decoupling capacitors.

[0060] In the power amplifier module, the positive and negative power supply pins (VCC+ / VCC-) of the first and second operational amplifiers are equipped with multi-stage decoupling capacitor networks. 1-10nF X7R ceramic capacitors are soldered close to the power supply pins to absorb switching noise using their low ESL characteristics and suppress transient current spikes caused by internal CMOS logic switching. MLCCs are placed to attenuate power supply ripple. Tantalum capacitors are placed at the power supply input to provide instantaneous current compensation, suppressing voltage fluctuations to within ±0.1%. The positive and negative power supply decoupling networks adopt a mirror-symmetric design to ensure common-mode rejection ratio and prevent DC offset introduced by power supply asymmetry.

[0061] Furthermore, the small signal input uses shielded cable transmission to suppress power frequency interference signals. In this embodiment, the small signal input uses a double-shielded cable harness, namely an inner copper braided mesh and an outer conductive adhesive shielding layer, with single-point grounding. The Faraday cage effect attenuates power frequency interference, reducing the amplitude of power frequency noise in the input signal. The shielding layer and signal ground are connected via a low-impedance path and grounded at a single point at the receiving end, eliminating common-mode interference caused by ground loops and improving the system's common-mode rejection ratio. Combined with the twisted-pair structure inside the cable harness, high-frequency electromagnetic coupling noise is further suppressed, ensuring reliable transmission of weak signals in complex industrial electromagnetic environments.

[0062] In this embodiment, the power frequency interference shielding circuit further includes a transformer, and the input and output terminal circuit diagram of the transformer is shown below. Figure 6 As shown in the diagram. The input terminals of the transformer are connected to the output terminals of the power amplifier. The transformer achieves a 20:1 voltage transformation ratio, converting the high input voltage to the low voltage required by the system, facilitating subsequent circuit processing and use. Simultaneously, the coordinated use of multiple transformers forms multi-level isolation protection, ensuring the reliability of signal transmission.

[0063] In summary, in the power frequency interference shielding circuit of this embodiment, the stability of the power supply is enhanced by the multi-stage capacitor filtering design of the isolation power supply module, common-mode inductors are used to effectively suppress common-mode interference, the multi-stage filtering circuit and dedicated chip design of the positive and negative voltage conversion module provide a stable and reliable power supply, the two-stage gain power amplifier module with decoupling capacitors reduces the impact of power supply noise, and the shielded wiring harness transmission method achieves effective suppression of power frequency interference in all aspects from power supply and signal transmission to power amplification. Overall, a complete anti-interference system is formed, which improves the anti-interference capability and signal quality in the process of large signal transmission.

[0064] The above-described specific examples are for illustrative purposes only and are not intended to limit the scope of this invention. Those skilled in the art to which this invention pertains can make various simple deductions, modifications, or substitutions based on the concept of this invention.

Claims

1. A power frequency interference shielding circuit, characterized in that, This includes an isolated power supply module, a positive voltage conversion module, a negative voltage conversion module, and a power amplifier module; The output terminal of the isolated power supply module is connected to the input terminals of the positive voltage conversion module and the negative voltage conversion module, respectively. The output of the isolated power supply module is connected in series with a common-mode inductor, and the output of the common-mode inductor is connected to the input of the positive voltage conversion module and the negative voltage conversion module, respectively. The positive voltage conversion module and the negative voltage conversion module output the converted voltage; The power amplifier module receives a small signal, amplifies the small signal, and then outputs it.

2. The power frequency interference shielding circuit as described in claim 1, characterized in that, The isolated power supply module includes a power chip, with the second pin of the power chip grounded and the third pin connected to an external power supply terminal. A first capacitor, a second capacitor, and a third capacitor are connected in parallel between the second pin and the third pin. The fourth pin of the power chip is the voltage output terminal, the fifth pin is grounded, and the fourth, fifth, sixth, seventh and eighth capacitors are connected in parallel between the fourth and fifth pins.

3. The power frequency interference shielding circuit as described in claim 2, characterized in that, The common-mode inductor includes a first common-mode inductor and a second common-mode inductor; The fourth pin of the power chip is connected to the power supply terminal through the first common-mode inductor, and the fifth pin is connected to the ground terminal through the second common-mode inductor.

4. The power frequency interference shielding circuit as described in claim 1, characterized in that, The positive voltage conversion module includes a power conversion chip. The second pin of the power conversion chip is connected to an external power supply terminal, the fourth pin is connected to a voltage divider resistor, the twelfth pin is connected to the gate of the first NMOS transistor and the gate of the second NMOS transistor, the fourteenth pin is connected to the gate of the third NMOS transistor and the gate of the fourth NMOS transistor, and the thirteenth pin is connected to the drain of the first NMOS transistor and the third NMOS transistor, and the source of the second NMOS transistor and the fourth NMOS transistor.

5. The power frequency interference shielding circuit as described in claim 1, characterized in that, The negative voltage conversion module includes a converter chip. The second pin of the converter chip is connected to ground after being connected in series with a first resistor; the third pin is connected to ground after being connected in series with a ninth capacitor, and is also connected to ground after being connected in series with a second resistor; the fourth pin is connected to ground after being connected to a tenth capacitor. The fifth pin is connected to the third resistor in series and then grounded; the sixth pin is connected to the eleventh capacitor and the fourth resistor respectively, the other end of the eleventh capacitor is grounded, and the other end of the fourth resistor is connected to the twelfth capacitor in series and then grounded. Pin 7 is connected to resistors 5 and 6 respectively. One end of resistor 5 is connected in series with inductor 2. Inductor 2 is connected to the anode of diode and capacitor 12 respectively. The other end of resistor 6 is grounded. Pin 8 is connected in series with resistor 7 and then grounded. Pin 9 is connected in series with capacitor 13 and then grounded. Pin 10 is connected in series with resistor 8 and then grounded. Pins 11 and 12 are connected between inductor 1 and capacitor 12. Inductor 12 is connected to inductor 2 and capacitor 22. Inductor 2 ... The other end of diode is grounded. The five resistor is also connected in parallel with the fourteenth capacitor. One end of the first inductor is connected to one end of the fifteenth, sixteenth, seventeenth, eighteenth, nineteenth and twentieth capacitors respectively, and the other end is grounded.

6. The power frequency interference shielding circuit as described in claim 1, characterized in that, The power amplifier module includes: The first-stage gain circuit includes a first operational amplifier and its feedback network; The second-stage gain circuit includes a second operational amplifier and its feedback network; A connecting resistor network is provided between the first-stage gain circuit and the second-stage gain circuit; The first-stage gain circuit and the second-stage gain circuit are electrically connected to the output terminals of the positive voltage conversion module and the negative voltage conversion module, respectively.

7. The power frequency interference shielding circuit as described in claim 6, characterized in that, The power supply ports of the first operational amplifier and the second operational amplifier are respectively equipped with decoupling capacitors.

8. The power frequency interference shielding circuit as described in claim 1, characterized in that, The small signal input is transmitted using shielded cables to suppress power frequency interference signals.

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