Circuit for suppressing high-frequency radiation noise of HDMI (High-Definition Multimedia Interface)

Abstract

The utility model provides a circuit used for an HDMI interface to suppress high frequency radiation noise, comprising a plurality of ESD protection diodes, a plurality of common mode inductors and a plurality of grounding capacitors, an HDMI interface CN1 is electrically connected with one ends of the ESD protection diodes, one ends of the grounding capacitors and one ends of the common mode inductors, the other ends of the common mode inductors are connected with a main control chip U1 of an intelligent electronic device, and the main control chip U1 is electrically connected with the HDMI interface CN1. One end of each grounding capacitor is grounded, the other end of each grounding capacitor is grounded, the grounding capacitors are arranged close to the HDMI CN1, the plurality of grounding capacitors can form a first-stage common-mode high-frequency noise filtering circuit, and the plurality of common-mode inductors can form a second-stage common-mode high-frequency noise filtering circuit. The beneficial effects of the utility model are that the first-stage common-mode high-frequency noise filter and the second-stage common-mode high-frequency noise filter can suppress high-frequency radiation noise of the HDMI CN1 at 148.5 MHz and multiple frequency points thereof, and the structure is simple, the cost is low, and the size is small.

Description

Technical Field

[0001] This utility model relates to the field of computer circuit technology, and specifically to a circuit for suppressing high-frequency radiation noise in an HDMI interface. Background Technology

[0002] HDMI (High-Definition Multimedia Interface) is a digital video / audio interface technology that can transmit audio and video signals simultaneously. It is currently the most popular high-definition interface and is widely used in home entertainment systems, professional audio and video equipment, computer monitors and other devices to transmit high-definition audio and video signals.

[0003] In modern electronic devices, especially portable devices such as laptops, the transmission of high-frequency signals is prone to radiated emission (RE), causing these devices to fail to meet international standards (such as GB / T 9254.1-2021) in electromagnetic compatibility (EMC) testing. As a crucial interface for high-bandwidth video signal transmission, the HDMI interface's clock signal (CLK) and high-speed data signals typically operate in the high-frequency range (such as 148.5MHz and its harmonics), making it a major source of radiated interference.

[0004] The GB / T 9254.1-2021 standard imposes strict requirements on the high-frequency radiation generated by electronic devices for radiated emission testing. The reference frequency (148.5MHz) and its harmonics (such as 297MHz and 594MHz) of the HDMI interface have incomplete common-mode current return paths, leading to excessive radiated electric field strength (typical value ≥47dBμV / m), exceeding the radiated emission limits (3m method) of GB / T 9254.1-2021 (30MHz~230MHz≤40dBμV / m, 230MHz~1GHz≤47dBμV / m). In this case, the electronic device fails the radiated emission test.

[0005] In existing technologies, the only solution for high-frequency radiation emission from HDMI interfaces is a single-stage ferrite bead filter. However, this solution is insufficient in suppressing high-frequency harmonics, making it difficult for electronic devices to pass radiation emission tests. Utility Model Content

[0006] To address the problems in the prior art, this utility model provides a circuit for suppressing high-frequency radiated noise in an HDMI interface. By placing multiple ESD protection diodes, multiple common-mode inductors, and multiple grounding capacitors between the main control chip U1 of the smart electronic device and the HDMI interface CN1, the multiple grounding capacitors form a first-stage common-mode high-frequency noise filtering circuit, and the multiple common-mode inductors form a second-stage common-mode high-frequency noise filtering circuit. Both the first-stage and second-stage common-mode high-frequency noise filters can suppress the high-frequency radiated noise of the HDMI interface CN1 at 148.5MHz and its multiples, thus solving the problem that the prior art lacks a good solution for suppressing high-frequency radiated noise in HDMI interfaces.

[0007] This invention provides a circuit for suppressing high-frequency radiated noise from an HDMI interface. The circuit is positioned between the main control chip U1 of a smart electronic device and the HDMI interface CN1. It includes multiple ESD protection diodes, multiple common-mode inductors, and multiple grounding capacitors. The HDMI interface CN1 is electrically connected to one end of each ESD protection diode, one end of each grounding capacitor, and one end of each common-mode inductor. The other end of each common-mode inductor is connected to the main control chip U1 of the smart electronic device. The other end of each grounding capacitor is grounded. The multiple common-mode inductors and the multiple grounding capacitors form multiple parallel LC filters. All grounding capacitors are positioned close to the HDMI interface CN1. The multiple grounding capacitors can form a first-stage common-mode high-frequency noise filtering circuit. The common-mode inductors are positioned on the HDMI signal line connecting the HDMI interface CN1 and the main control chip U1 of the smart electronic device. The multiple common-mode inductors can form a second-stage common-mode high-frequency noise filtering circuit. The first-stage and second-stage common-mode high-frequency noise filters can suppress high-frequency radiated noise from the HDMI interface CN1 at 148.5MHz and its harmonics.

[0008] In a further improvement to this invention, the grounding capacitors are all located between the HDMI interface CN1 and the common mode inductor.

[0009] This utility model is further improved in that when the standard of the HDMI interface CN1 is HDMI 1.4, the capacitance of the grounding capacitor is ≤0.5pF, and when the standard of the HDMI interface CN1 is HDMI 2.0, the capacitance of the grounding capacitor is ≤0.4pF.

[0010] In a further improvement to this invention, the package size of the grounding capacitor is 0201 or 0402.

[0011] This invention is further improved in that the impedance range of the common mode inductor is R, 90Ω≤R≤120Ω.

[0012] In a further improvement of this invention, the common-mode inductor is positioned close to the interference source. When the HDMI interface CN1 outputs a signal, the common-mode inductor is positioned close to the main control chip U1 of the smart electronic device. When the HDMI interface CN1 inputs a signal to the main control chip U1 of the smart electronic device, the common-mode inductor is positioned close to the HDMI interface CN1.

[0013] This utility model is further improved in that each of the multiple common-mode inductors has 4 pins, and the multiple common-mode inductors are designated as common-mode inductor L1, common-mode inductor L2, common-mode inductor L3, and common-mode inductor L4. The multiple grounding capacitors are designated as grounding capacitor C1, grounding capacitor C2, grounding capacitor C3, grounding capacitor C4, grounding capacitor C5, grounding capacitor C6, grounding capacitor C7, and grounding capacitor C8. The HDMI interface CN1 has 23 pins, and the first pin of the HDMI interface CN1 is connected to the second pin of the common-mode inductor L1. One end of the grounding capacitor C8 is connected. Pin 3 of the HDMI interface CN1 is connected to pin 3 of the common-mode inductor L1 and one end of the grounding capacitor C7. Pins 1 and 4 of the common-mode inductor L1 are connected to the main control chip U1 of the intelligent electronic device. Pin 4 of the HDMI interface CN1 is connected to pin 2 of the common-mode inductor L2 and one end of the grounding capacitor C6. Pin 6 of the HDMI interface CN1 is connected to pin 3 of the common-mode inductor L2 and one end of the grounding capacitor C5. The common-mode inductor L2... Pins 1 and 4 are connected to the main control chip U1 of the intelligent electronic device. Pin 7 of the HDMI interface CN1 is connected to pin 2 of the common mode inductor L3 and one end of the grounding capacitor C4. Pin 9 of the HDMI interface CN1 is connected to pin 3 of the common mode inductor L3 and one end of the grounding capacitor C3. Pins 1 and 4 of the common mode inductor L3 are connected to the main control chip U1 of the intelligent electronic device. Pin 10 of the HDMI interface CN1 is connected to pin 2 of the common mode inductor L4 and one end of the grounding capacitor C2. Pin 12 of the HDMI interface CN1 is connected to pin 3 of the common mode inductor L4 and one end of the grounding capacitor C1. Pins 1 and 4 of the common mode inductor L4 are connected to the main control chip U1 of the intelligent electronic device. The other ends of the grounding capacitors C1, C2, C3, C4, C5, C6, C7, and C8 are grounded.

[0014] This utility model is further improved in that the plurality of ESD protection diodes are designated as ESD protection diode D1 and ESD protection diode D2. Both ESD protection diodes D1 and D2 have 10 pins. Pin 1 of ESD protection diode D1 is connected to pin 10 of ESD protection diode D1, pin 1 of HDMI interface CN1, and pin 2 of common-mode inductor L1. Pin 2 of ESD protection diode D1 is connected to pin 9 of ESD protection diode D1, pin 3 of HDMI interface CN1, and pin 3 of common-mode inductor L1. Pin 4 of ESD protection diode D1 is connected to pin 7 of ESD protection diode D1, pin 4 of HDMI interface CN1, and pin 2 of common-mode inductor L2. Pin 5 of ESD protection diode D1 is connected to... Pin 6 of D1, pin 6 of the HDMI interface CN1, and pin 3 of the common-mode inductor L2 are connected. Pin 1 of the ESD protection diode D2 is connected to pin 10 of the ESD protection diode D2, pin 7 of the HDMI interface CN1, and pin 2 of the common-mode inductor L3. Pin 2 of the ESD protection diode D2 is connected to pin 9 of the ESD protection diode D2, pin 9 of the HDMI interface CN1, and pin 3 of the common-mode inductor L3. Pin 4 of the ESD protection diode D2 is connected to pin 7 of the ESD protection diode D2, pin 10 of the HDMI interface CN1, and pin 2 of the common-mode inductor L4. Pin 5 of the ESD protection diode D2 is connected to pin 6 of the ESD protection diode D2, pin 12 of the HDMI interface CN1, and pin 3 of the common-mode inductor L4.

[0015] Compared with the prior art, the beneficial effects of this utility model are: it provides a circuit for suppressing high-frequency radiated noise in HDMI interfaces. By setting multiple ESD protection diodes, multiple common-mode inductors, and multiple grounding capacitors between the main control chip U1 of the smart electronic device and the HDMI interface CN1, the multiple grounding capacitors can form a first-stage common-mode high-frequency noise filtering circuit, and the multiple common-mode inductors can form a second-stage common-mode high-frequency noise filtering circuit. The first-stage and second-stage common-mode high-frequency noise filters can suppress the high-frequency radiated noise of the HDMI interface CN1 at 148.5MHz and its multiples. In other words, through the synergistic effect of the two-stage filtering circuits, the high-frequency radiated noise of the HDMI signal at 148.5MHz and its multiples is effectively suppressed, reducing the risk of equipment damage due to voltage fluctuations or overvoltage, and significantly improving the anti-interference capability of HDMI interface electronic devices, thereby improving the HDMI interface's performance. The overall reliability of the electronic device is improved; the common-mode inductor has a smaller impact on differential-mode signals, ensuring the integrity of the high-bandwidth HDMI signal; the grounding capacitor has a higher impedance to low-frequency signals, which will not cause significant attenuation of HDMI signal transmission; the circuit structure is simple and low-cost; the installation position is flexible and the size is small, saving space; the grounding capacitor and common-mode inductor can be flexibly installed near the HDMI interface, or even directly integrated into the PCB layout of the HDMI interface. This local installation method can more efficiently absorb high-frequency noise and prevent noise from propagating on the HDMI signal line. The common-mode inductor and grounding capacitor are small in size, suitable for devices with limited space such as laptops. This design will not significantly increase the size or weight of the device; the capacitance value of the grounding capacitor and the inductance value of the common-mode inductor can be adjusted according to actual test results to achieve the best filtering effect, solving the problem that existing technologies do not have a good solution for suppressing high-frequency radiation noise from HDMI interfaces. Attached Figure Description

[0016] To more clearly illustrate the solutions in 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 some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a circuit diagram of a circuit for suppressing high-frequency radiation noise in an HDMI interface according to the present invention. Detailed Implementation

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or accompanying drawings of this invention are used to distinguish different objects, not to describe a particular order.

[0019] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the present invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0021] like Figure 1As shown, this utility model provides a circuit for suppressing high-frequency radiated noise from an HDMI interface. It is positioned between the main control chip U1 of a smart electronic device and the HDMI interface CN1. The circuit includes multiple ESD protection diodes, multiple common-mode inductors, and multiple grounding capacitors. The HDMI interface CN1 is electrically connected to one end of each ESD protection diode, one end of each grounding capacitor, and one end of each common-mode inductor. The other end of the common-mode inductor is connected to the main control chip U1 of the smart electronic device, and the other end of each grounding capacitor is grounded. The multiple common-mode inductors and grounding capacitors form multiple parallel LC filters. The grounding capacitors are all positioned close to the HDMI interface CN1. The multiple grounding capacitors can form a first-stage common-mode high-frequency noise filtering circuit. The common-mode inductors are positioned on the HDMI signal line connecting the HDMI interface CN1 and the main control chip U1 of the smart electronic device. The multiple common-mode inductors can form a second-stage common-mode high-frequency noise filtering circuit. The grounding capacitors are all positioned between the HDMI interface CN1 and the common-mode inductors. When the standard of the HDMI interface CN1 is HDMI 1.4, the capacitance of the grounding capacitor is ≤0.5pF. When the standard of the HDMI interface CN1 is HDMI 1.4, the capacitance of the grounding capacitor is ≤0.5pF. At 2.0, the capacitance of the grounding capacitor is ≤0.4pF, and the package size of the grounding capacitor is 0201 or 0402. The impedance range of the common-mode inductor is R, 90Ω≤R≤120Ω. The common-mode inductor is placed close to the interference source. When the HDMI interface CN1 outputs a signal, the common-mode inductor is placed close to the main control chip U1 of the intelligent electronic device. When the HDMI interface CN1 inputs a signal to the main control chip U1 of the intelligent electronic device, the common-mode inductor is placed close to the HDMI interface CN1. In this embodiment, the first-stage common-mode high-frequency noise filter and the second-stage common-mode high-frequency noise filter can suppress the high-frequency radiation noise of the HDMI interface CN1 at 148.5MHz and its harmonics. That is, through the synergistic effect of the two-stage filtering circuit, the high-frequency radiation noise of the HDMI signal at 148.5MHz and its harmonics is effectively suppressed, reducing the risk of equipment damage due to voltage fluctuations or overvoltage, greatly improving the anti-interference capability of the HDMI interface electronic device, and thus improving the overall reliability of the HDMI interface electronic device. A common-mode inductor is used to suppress the propagation of common-mode noise. The common-mode inductor employs a double-wound structure, presenting high impedance to common-mode noise while having minimal impact on differential-mode signals. A capacitor to ground is added before the common-mode inductor; the capacitance value is selected based on the specific HDMI application. This capacitor filters out common-mode high-frequency transient noise by short-circuiting the high-frequency noise to ground, thereby reducing common-mode high-frequency noise on the signal line. The first-stage common-mode high-frequency noise filtering circuit, with the ground capacitor placed close to the HDMI interface, quickly filters out common-mode high-frequency noise. The second-stage common-mode high-frequency noise filtering circuit, with the common-mode inductor connected to the HDMI signal line, further suppresses the propagation of common-mode noise. The two stages of filtering circuits work together to form a highly efficient noise suppression system.In terms of layout: the ground capacitor should be installed as close as possible to the HDMI interface to reduce the area of ​​the signal loop and avoid high-frequency noise coupling to other circuits; short pin design: the pins of the filter components should be as short as possible to reduce parasitic inductance and resistance and ensure filtering effect; ground plane optimization: ensure that the ground terminal of the filter component is directly connected to the ground plane of the HDMI interface, avoiding long traces or multiple connection points.

[0022] like Figure 1As shown, multiple common-mode inductors each have 4 pins. These common-mode inductors are designated as L1, L2, L3, and L4. Multiple grounding capacitors are designated as C1, C2, C3, C4, C5, C6, C7, and C8. The HDMI interface CN1 has 23 pins. Pin 1 of HDMI interface CN1 is connected to pin 2 of common-mode inductor L1 and one end of grounding capacitor C8. Pin 3 of HDMI interface CN1 is connected to pin 3 of common-mode inductor L1 and one end of grounding capacitor C7. Pins 1 and 4 of common-mode inductor L1 are connected to the main control chip U1 of the intelligent electronic device. Pin 4 of HDMI interface CN1 is connected to pin 2 of common-mode inductor L2 and one end of grounding capacitor C6. Pin 6 of HDMI interface CN1 is connected to pin 3 of common-mode inductor L2 and one end of grounding capacitor C5. The common-mode inductor L2... Pins 1 and 4 are connected to the main control chip U1 of the intelligent electronic device. Pin 7 of HDMI interface CN1 is connected to pin 2 of common mode inductor L3 and one end of grounding capacitor C4. Pin 9 of HDMI interface CN1 is connected to pin 3 of common mode inductor L3 and one end of grounding capacitor C3. Pins 1 and 4 of common mode inductor L3 are connected to the main control chip U1 of the intelligent electronic device. Pin 10 of HDMI interface CN1 is connected to pin 2 of common mode inductor L4 and one end of grounding capacitor C2. Pin 12 of HDMI interface CN1 is connected to pin 3 of common mode inductor L4 and one end of grounding capacitor C1. Pins 1 and 4 of common mode inductor L4 are connected to the main control chip U1 of the intelligent electronic device. The other ends of grounding capacitors C1, C2, C3, C4, C5, C6, C7, and C8 are grounded.Multiple ESD protection diodes, designated as ESD protection diode D1 and ESD protection diode D2, are provided. Both ESD protection diodes D1 and D2 have 10 pins. Pin 1 of ESD protection diode D1 is connected to pin 10 of ESD protection diode D1, pin 1 of HDMI interface CN1, and pin 2 of common-mode inductor L1. Pin 2 of ESD protection diode D1 is connected to pin 9 of ESD protection diode D1, pin 3 of HDMI interface CN1, and pin 3 of common-mode inductor L1. Pin 4 of ESD protection diode D1 is connected to pin 7 of ESD protection diode D1, pin 4 of HDMI interface CN1, and pin 2 of common-mode inductor L2. Pin 5 of ESD protection diode D1 is connected to pin 6 of ESD protection diode D2. The pins of the HDMI interface CN1 and common mode inductor L2 are connected. The pin 1 of the ESD protection diode D2 is connected to the pin 10 of the ESD protection diode D2, the pin 7 of the HDMI interface CN1 and the pin 2 of the common mode inductor L3. The pin 2 of the ESD protection diode D2 is connected to the pin 9 of the ESD protection diode D2, the pin 9 of the HDMI interface CN1 and the pin 3 of the common mode inductor L3. The pin 4 of the ESD protection diode D2 is connected to the pin 7 of the ESD protection diode D2, the pin 10 of the HDMI interface CN1 and the pin 2 of the common mode inductor L4. The pin 5 of the ESD protection diode D2 is connected to the pin 6 of the ESD protection diode D2, the pin 12 of the HDMI interface CN1 and the pin 3 of the common mode inductor L4. In this embodiment, when external high-voltage electrostatic discharge and high-frequency interference signals enter the device through the HDMI interface, the ESD protection diode has a specific clamping voltage. When the input voltage exceeds this value, the diode will quickly conduct, clamping the excessive voltage within a safe range. The signal processed by the ESD protection diode enters the common-mode inductor group, where the ESD protection diode first absorbs these transient voltages to prevent damage to the internal circuitry. High-frequency noise (such as 148.5MHz and its harmonics) on the HDMI signal line can propagate to subsequent circuits or chips. The first-stage common-mode high-frequency noise filtering circuit prevents the propagation of high-frequency noise, especially common-mode noise. The second-stage common-mode high-frequency noise filtering circuit further filters out high-frequency noise, ensuring that high-frequency components on the signal line are absorbed. The capacitance value to ground needs to be strictly controlled (e.g., HDMI 1.4 ≤ 0.5pF, HDMI 2.0 ≤ 0.4pF) to avoid negatively impacting the normal transmission of the HDMI signal. Common-mode inductors not only suppress common-mode interference signals entering the device, but also reduce the device's radiated interference to the outside world. By replacing the common-mode inductor with a different model, its common-mode immunity can be further improved, thereby mitigating the high-frequency radiation problem of HDMI interface electronic devices.

[0023] As can be seen from the above, this utility model provides a circuit for suppressing high-frequency radiated noise in an HDMI interface. By setting multiple ESD protection diodes, multiple common-mode inductors, and multiple grounding capacitors between the main control chip U1 and the HDMI interface CN1 of the intelligent electronic device, the multiple grounding capacitors form a first-stage common-mode high-frequency noise filtering circuit, and the multiple common-mode inductors form a second-stage common-mode high-frequency noise filtering circuit. The first-stage and second-stage common-mode high-frequency noise filters can suppress the high-frequency radiated noise of the HDMI interface CN1 at 148.5MHz and its multiples. In other words, through the synergistic effect of the two-stage filtering circuits, the high-frequency radiated noise of the HDMI signal at 148.5MHz and its multiples is effectively suppressed, reducing the risk of damage to the device due to voltage fluctuations or overvoltage, significantly improving the anti-interference capability of the HDMI interface electronic device, and thus enhancing the overall performance of the HDMI interface electronic device. The overall reliability is excellent; the common-mode inductor has a minimal impact on differential-mode signals, ensuring the integrity of the high-bandwidth HDMI signal; the grounding capacitor has a high impedance to low-frequency signals, preventing significant attenuation of HDMI signal transmission; the circuit structure is simple and low-cost; it is flexible in installation location, small in size, and saves space; the grounding capacitor and common-mode inductor can be flexibly installed near the HDMI interface, or even directly integrated into the HDMI interface PCB layout. This local installation method can more efficiently absorb high-frequency noise and prevent noise propagation on the HDMI signal line. The small size of the common-mode inductor and grounding capacitor makes them suitable for space-constrained devices such as laptops, and this design does not significantly increase the size or weight of the device; the capacitance value of the grounding capacitor and the inductance value of the common-mode inductor can be adjusted according to actual test results to achieve the best filtering effect, solving the problem that existing technologies do not have a good solution for suppressing high-frequency radiation noise from HDMI interfaces.

[0024] The specific embodiments described above are preferred embodiments of this utility model, and are not intended to limit the specific scope of this utility model. The scope of this utility model includes but is not limited to the specific embodiments described above. All equivalent changes made in accordance with this utility model are within the protection scope of this utility model.

Claims

1. A circuit for suppressing high-frequency radiated noise in an HDMI interface, disposed between the main control chip U1 and the HDMI interface CN1 of a smart electronic device, characterized in that: The system includes multiple ESD protection diodes, multiple common-mode inductors, and multiple grounding capacitors. The HDMI interface CN1 is electrically connected to one end of each of the ESD protection diodes, one end of each grounding capacitor, and one end of each common-mode inductor. The other end of each common-mode inductor is connected to the main control chip U1 of the smart electronic device. The other end of each grounding capacitor is grounded. The multiple common-mode inductors and multiple grounding capacitors form multiple parallel LC filters. The grounding capacitors are all located close to the HDMI interface CN1. The multiple grounding capacitors can form a first-stage common-mode high-frequency noise filtering circuit. The common-mode inductors are located on the HDMI signal line connecting the HDMI interface CN1 and the main control chip U1 of the smart electronic device. The multiple common-mode inductors can form a second-stage common-mode high-frequency noise filtering circuit. The first-stage common-mode high-frequency noise filter and the second-stage common-mode high-frequency noise filter can suppress the high-frequency radiation noise of the HDMI interface CN1 at 148.5MHz and its harmonics.

2. The circuit for suppressing high-frequency radiated noise in an HDMI interface according to claim 1, characterized in that: The grounding capacitors are all located between the HDMI interface CN1 and the common mode inductor.

3. The circuit for suppressing high-frequency radiated noise in an HDMI interface according to claim 2, characterized in that: When the standard of the HDMI interface CN1 is HDMI 1.4, the capacitance of the grounding capacitor is ≤0.5pF; when the standard of the HDMI interface CN1 is HDMI 2.0, the capacitance of the grounding capacitor is ≤0.4pF.

4. The circuit for suppressing high-frequency radiated noise in an HDMI interface according to claim 3, characterized in that: The package size of the grounding capacitor is 0201 or 0402.

5. The circuit for suppressing high-frequency radiated noise in an HDMI interface according to claim 4, characterized in that: The impedance range of the common-mode inductor is R, 90Ω≤R≤120Ω.

6. The circuit for suppressing high-frequency radiated noise in an HDMI interface according to claim 5, characterized in that: The common-mode inductor is positioned close to the interference source. When the HDMI interface CN1 outputs a signal, the common-mode inductor is positioned close to the main control chip U1 of the smart electronic device. When the HDMI interface CN1 inputs a signal to the main control chip U1 of the smart electronic device, the common-mode inductor is positioned close to the HDMI interface CN1.

7. The circuit for suppressing high-frequency radiated noise in an HDMI interface according to claim 6, characterized in that: Each of the aforementioned common-mode inductors has four pins. The common-mode inductors are designated as common-mode inductor L1, common-mode inductor L2, common-mode inductor L3, and common-mode inductor L4. The aforementioned grounding capacitors are designated as grounding capacitor C1, grounding capacitor C2, grounding capacitor C3, grounding capacitor C4, grounding capacitor C5, grounding capacitor C6, grounding capacitor C7, and grounding capacitor C8. The HDMI interface CN1 has 23 pins. The first pin of the HDMI interface CN1 is connected to the second pin of the common-mode inductor L1 and one end of the grounding capacitor C8. The HDMI interface CN1 is connected to the common-mode inductor L1, pin 3, and one end of the grounding capacitor C7. The common-mode inductor L1's pins 1 and 4 are connected to the main control chip U1 of the intelligent electronic device. The HDMI interface CN1's pin 4 is connected to the common-mode inductor L2, pin 2, and one end of the grounding capacitor C6. The HDMI interface CN1's pin 6 is connected to the common-mode inductor L2, pin 3, and one end of the grounding capacitor C5. The common-mode inductor L2's pins 1 and 4 are connected to the grounding capacitor C7. The HDMI interface CN1 is connected to the main control chip U1 of the intelligent electronic device. Pin 7 of the HDMI interface CN1 is connected to pin 2 of the common mode inductor L3 and one end of the grounding capacitor C4. Pin 9 of the HDMI interface CN1 is connected to pin 3 of the common mode inductor L3 and one end of the grounding capacitor C3. Pins 1 and 4 of the common mode inductor L3 are connected to the main control chip U1 of the intelligent electronic device. Pin 10 of the HDMI interface CN1 is connected to pin 2 of the common mode inductor L4 and one end of the grounding capacitor C2. Pin 12 of the HDMI interface CN1 is connected to pin 3 of the common mode inductor L4 and one end of the grounding capacitor C1. Pins 1 and 4 of the common mode inductor L4 are connected to the main control chip U1 of the intelligent electronic device. The other ends of the grounding capacitors C1, C2, C3, C4, C5, C6, C7, and C8 are grounded.

8. The circuit for suppressing high-frequency radiated noise in an HDMI interface according to claim 7, characterized in that: The plurality of ESD protection diodes are designated as ESD protection diode D1 and ESD protection diode D2. Both ESD protection diodes D1 and D2 have 10 pins. Pin 1 of ESD protection diode D1 is connected to pin 10 of ESD protection diode D1, pin 1 of HDMI interface CN1, and pin 2 of common-mode inductor L1. Pin 2 of ESD protection diode D1 is connected to pin 9 of ESD protection diode D1, pin 3 of HDMI interface CN1, and pin 3 of common-mode inductor L1. Pin 4 of ESD protection diode D1 is connected to pin 7 of ESD protection diode D1, pin 4 of HDMI interface CN1, and pin 2 of common-mode inductor L2. Pin 5 of ESD protection diode D1 is connected to pin 6 of ESD protection diode D2. The first pin of the ESD protection diode D2 is connected to the 6th pin of the HDMI interface CN1 and the 3rd pin of the common mode inductor L2. The 1st pin of the ESD protection diode D2 is connected to the 10th pin of the ESD protection diode D2, the 7th pin of the HDMI interface CN1 and the 2nd pin of the common mode inductor L3. The 2nd pin of the ESD protection diode D2 is connected to the 9th pin of the ESD protection diode D2, the 9th pin of the HDMI interface CN1 and the 3rd pin of the common mode inductor L3. The 4th pin of the ESD protection diode D2 is connected to the 7th pin of the ESD protection diode D2, the 10th pin of the HDMI interface CN1 and the 2nd pin of the common mode inductor L4. The 5th pin of the ESD protection diode D2 is connected to the 6th pin of the ESD protection diode D2, the 12th pin of the HDMI interface CN1 and the 3rd pin of the common mode inductor L4.

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