CN116131796A - Anti-interference protection circuit of metal shell device and electronic equipment - Google Patents
Anti-interference protection circuit of metal shell device and electronic equipment Download PDFInfo
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- CN116131796A CN116131796A CN202310240507.3A CN202310240507A CN116131796A CN 116131796 A CN116131796 A CN 116131796A CN 202310240507 A CN202310240507 A CN 202310240507A CN 116131796 A CN116131796 A CN 116131796A
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0007—Casings
- H05K9/0049—Casings being metallic containers
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/0115—Frequency selective two-port networks comprising only inductors and capacitors
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0067—Devices for protecting against damage from electrostatic discharge
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The application discloses an anti-interference protection circuit of a metal shell device and electronic equipment, wherein the anti-interference protection circuit comprises a public ground wire and a filter circuit connected between the public ground wire and the metal shell, and the filter circuit at least comprises a capacitor, wherein the capacitor is coupled to the metal shell; at least one line of the anti-interference protection circuit system is connected with the inductor in series. When encountering interference, the method and the device are beneficial to reducing the influence of the interference on the shell device and improving the anti-interference capability of the device.
Description
Technical Field
The application belongs to the technical field of anti-interference protection circuits, and particularly relates to an anti-interference protection circuit of a metal shell device and electronic equipment.
Background
Electromagnetic interference is still a problem facing the whole electronic industry, and at present, the anti-interference prevention and control mode of a factory is not to purchase simple articles such as anti-static work clothes and wrist bands, and when many enterprises meet field inspection, the enterprises often make careful preparation, but the interference problem is refused. In view of the above-mentioned current situation, it is urgent for those skilled in the art to find an anti-interference protection circuit for a metal-clad device, which is packaged with a metal-clad device that has many devices in the existing electronics industry.
The anti-interference protection circuit aiming at the metal shell device at present ensures that the metal shell device can only pass certain low-intensity interference tests and cannot pass certain high-intensity tests such as a high-current injection immunity (BCI) test and the like, and the anti-interference capability needs to be improved.
Disclosure of Invention
In order to solve the technical problems, embodiments disclosed herein provide an anti-interference protection circuit of a metal-case device and an electronic apparatus, so as to improve the anti-interference capability of the anti-interference protection circuit of the metal-case device.
In a first aspect, the present application provides an anti-interference protection circuit for a metal-case device, the anti-interference protection circuit comprising a common ground and a filter circuit connected between the common ground and a metal-case, the filter circuit comprising at least a capacitor coupled to the metal-case;
at least one line of the anti-interference protection circuit system is connected with an inductor in series.
Further, the filter circuit includes a pi-type filter circuit including:
a first capacitor coupled to the metal housing;
a second capacitor coupled to the metal housing;
the first inductor is coupled to the first capacitor and the second capacitor respectively.
Further, the first inductor is a magnetic bead.
Further, the common ground wire is connected in series with the first inductor.
Further, the anti-interference protection circuit further comprises a power line, the power line is connected in series with the second inductor, and the power line is coupled to the metal shell through a fourth capacitor.
Further, the anti-interference protection circuit further comprises a signal wire, and the signal wire is connected in series with the third inductor.
Further, the anti-interference protection circuit further includes:
a third capacitor coupled to the metal housing;
a fourth capacitance coupled to the metal housing;
a second inductor coupled to the third capacitor and the fourth capacitor, respectively;
the anti-interference protection circuit further comprises a power line, and the second inductor is connected in series with the power line.
Further, the second inductor is a magnetic bead.
Further, the anti-interference protection circuit further comprises a signal wire, and the signal wire is connected in series with the third inductor.
Further, the anti-interference protection circuit further includes:
a fifth capacitor coupled to the common ground;
a sixth capacitance coupled to the common ground;
a third inductor coupled to the fifth capacitor and the sixth capacitor, respectively;
the anti-interference protection circuit further comprises a signal wire, and the third inductor is connected in series with the signal wire.
Further, the third inductor is a magnetic bead.
Further, the anti-interference protection circuit further comprises a power line and a signal line, wherein the power line and/or the signal line is/are connected with a common ground line through a bidirectional TVS tube.
Further, the anti-interference protection circuit further comprises a power line and a signal line, and the power line and/or the signal line is/are connected with the metal shell through a capacitor.
In a second aspect, the present application provides an electronic device, comprising:
the metal shell is internally provided with a protected internal module, and the internal module is provided with a public ground wire;
and the protection circuit adopts the anti-interference protection circuit of the metal shell device.
Compared with the prior art, the beneficial technical effects that this application obtained:
the anti-interference protection circuit of the metal shell device provided by the application at least comprises a capacitor, wherein the filter circuit between the public ground wire and the metal shell comprises a capacitor; at least one line of the anti-interference protection circuit system is connected with an inductor in series; the capacitor provides a discharge passage for the electrostatic charge of the metal shell, so that the anti-interference capability of the metal shell device is improved; the influence of the high-frequency interference signal taking the ground level as a reference on the circuit can be reduced through the filter circuit, and the transient common mode voltage difference between the circuit and the interference source can be restrained; the high-frequency interference is filtered by using the inductor, and the noise can be restrained by absorption and reflection.
The filter circuit comprises a pi-type filter circuit, the interference current is converted into point voltage through the first capacitor, and then the high-resistance anti-magnetic beads and the second capacitor can greatly reduce the flowing interference current signals, so that the intensity of high-frequency and high-current interference signals in the wire harness is reduced.
The electronic equipment provided by the application is provided with the anti-interference protection circuit of the metal shell device, so that when the electronic equipment encounters electrostatic discharge, large circuit injection interference or electromagnetic wave interference and the like, the influence of external interference signals on the inside of the device is reduced, and the anti-interference capability and the service life of the internal module device are improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an anti-interference protection circuit according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of an anti-interference protection circuit according to another embodiment of the present disclosure;
FIG. 3 is a schematic diagram of an anti-interference protection circuit according to another embodiment of the present disclosure;
FIG. 4 is a schematic diagram of an anti-interference protection circuit according to another embodiment of the present disclosure;
fig. 5 is a schematic structural diagram of an electronic device according to another embodiment of the present application;
reference numerals: 1-first capacitor, 2-second capacitor, 3-third capacitor, 4-fourth capacitor, 5-fifth capacitor, 6-sixth capacitor, 7-power line Vcc, 8-signal line Out, 9-metal shell, 10-common ground GND, 11-first inductor, 12-second inductor, 13-third inductor, 14-first bidirectional TVS tube, 15-second bidirectional TVS tube, 16-electronic device, 17-internal module and 18-protection circuit.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
In the description of the present application, it should be understood that the directions or positional relationships indicated by the terms "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of description of the present application and to simplify the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more features. In the description of the present application, the meaning of "a plurality" is two or more, and at least one means may be one, two or more, unless explicitly defined otherwise.
All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure. The following embodiments and features of the embodiments may be combined with each other without conflict.
The anti-interference protection circuit of the existing metal shell device enables the metal shell device to pass certain low-intensity interference tests only, and the anti-interference capability needs to be improved; or fails some high-intensity interference tests and cannot cope with more interference test environments.
In order to solve the technical problems, embodiments disclosed herein provide an anti-interference protection circuit of a metal-case device and an electronic device.
An anti-interference protection circuit of a metal shell device comprises a common ground GND10 and a filter circuit connected between the common ground GND10 and a metal shell 9, wherein the filter circuit at least comprises a capacitor, and the capacitor is coupled to the metal shell 9; at least one line of the anti-interference protection circuit system is connected with the inductor in series.
It should be noted that, the wire system is a connection mode of signal transmission, and common includes two-wire system, three-wire system and four-wire system. Two-wire system, i.e. the power supply and the signal share two wires; the three-wire system refers to a common line with one wire as a positive power line, one wire as a positive signal line and one wire as a negative power line and a negative signal line; four-wire refers to two wires of a power supply, two wires of a signal, the power supply and the signal being operated separately.
Optionally, the inductor comprises a magnetic bead or a wire wound inductor.
The capacitor provides a discharge path for the electrostatic charge of the metal shell 9, so that the anti-interference capability of the metal shell device is improved; the influence of the high-frequency interference signal taking the ground level as a reference on the circuit can be reduced through the filter circuit, and the transient common mode voltage difference between the circuit and the interference source can be restrained; the high-frequency interference is filtered by using the inductor, and the noise can be restrained by absorption and reflection.
The present application also provides an electronic device 16 comprising: a metal shell 9, wherein a protected inner module 17 is arranged in the metal shell 9, and the inner module 17 is provided with a common ground wire GND10; the protection circuit 18. The protection circuit 18 adopts the anti-interference protection circuit of the metal shell device.
The electronic equipment 16 provided by the application is provided with the anti-interference protection circuit of the metal shell device, when the electronic equipment encounters electrostatic discharge, large circuit injection interference or electromagnetic wave interference and the like, the influence of external interference signals on the inside of the device is reduced, and the anti-interference capability and the service life of the internal module 17 are improved.
Embodiments of the present application are described below with reference to the accompanying drawings.
Referring to fig. 1, in a first embodiment of the present application, an anti-interference protection circuit of a metal-shell device includes a common ground GND10 and a filter circuit connected between the common ground GND10 and a metal shell 9, the filter circuit includes a pi-type filter circuit;
the pi-type filter circuit includes:
a first capacitor 1, the first capacitor 1 being coupled to the metal housing 9;
a second capacitor 2, the second capacitor 2 being coupled to the metal housing 9;
a first inductor 11, the first inductor 11 being coupled to the first capacitor 1 and the second capacitor 2; the first inductor 11 is connected in series to the common ground GND10.
In some embodiments, the first inductor 11 is a magnetic bead.
In this embodiment, pi-type filtering composed of capacitance-magnetic bead-capacitance is connected to the common ground GND10, a first inductor 11 (which may be a magnetic bead) is connected in series to the common ground GND10, two ends of the magnetic bead are respectively coupled to the first capacitor 1 and the second capacitor 2, and the first capacitor 1 and the second capacitor 2 are coupled to the metal housing 9 to provide a bleed path for the electrostatic charges of the metal housing 9.
Optionally, in some embodiments, the tamper protection circuit further comprises: a third capacitor 3, a fourth capacitor 4 and a second inductor 12, the third capacitor 3 being coupled to the metal housing 9; the fourth capacitor 4 is coupled to the metal housing 9; the second inductor 12 is coupled to the third capacitor 3 and the fourth capacitor 4, respectively; the anti-interference protection circuit comprises a power line Vcc7, and the second inductor 12 is connected in series with the power line Vcc7.
Further, the anti-interference protection circuit further includes a signal line Out8, and the signal line Out8 is connected in series with the third inductor 13. In some embodiments, the second inductor 12 and/or the third inductor 13 are magnetic beads.
In some embodiments, pi-type filtering consisting of capacitance-magnetic bead-capacitance is connected to the power line Vcc7, so that the interference signal intensity can be effectively reduced, the wire harness interference signal loop can be changed, and the normal operation of a subsequent circuit can be ensured.
In some embodiments, the pi-type filtering adopted can cope with more test environments, and the anti-interference capability and the safety performance of the product are better ensured; the high protection performance of pi-type filtering can be realized through the device combination, and a certain protection effect can still be achieved if only a certain capacitor is damaged.
When the anti-interference protection circuit of the existing metal shell device is subjected to radiation emission immunity (RS) test, the ISO 1145-2:2004 test standard is adopted. The output voltage fluctuation of the existing anti-interference protection circuit at 400MHz-3GHz exceeds +/-40 mv, and the EMC protection requirement of class A is not met. Class a refers to an output voltage range of 500mv±40mv.
Radiation immunity is mainly achieved by interfering with the DUT (Device Under Test ) by means of spatial radiation, and there are two paths: the interference energy is coupled to the wiring harness and the spatial disturbance (i.e. spatial disturbance) is coupled to the PCB (PRSnted Circuit Board, printed circuit board) through the slots. The positioning test shows that the interference is mainly coupled to the wire harness and then injected into the internal chip, so that the anti-interference protection circuit provided in the specific embodiment (shown in fig. 1) adjusts the filtering on the power line Vcc7 and the common ground line GND10 to pi-type filtering; optionally, the first capacitor 1, the second capacitor 2, the third capacitor 3 and the fourth capacitor 4 adopt 1nF, the first inductor 11 and the second inductor 12 adopt hundred mega-impedance 2000 Ω magnetic beads, and the signal line Out8 is connected with the hundred mega-impedance 2000 Ω magnetic beads in series. The anti-interference protection circuit shown in fig. 1 meets the protection requirement of the grade A after being tested.
Referring to fig. 2, the second embodiment of the present application is different from the embodiment shown in fig. 1 in that, in the embodiment shown in fig. 2, the signal line Out8 is not a serial magnetic bead, but is connected with pi-type filtering consisting of capacitance-magnetic bead-capacitance.
Alternatively, the power supply line Vcc7 and the signal line Out8 are connected to the common ground GND10 through a bidirectional TVS pipe.
Referring to fig. 2, the anti-interference protection circuit of the metal-case device includes a common ground GND10 and a filter circuit connected between the common ground GND10 and the metal case 9, the filter circuit including a pi-type filter circuit; the pi-type filter circuit includes:
a first capacitor 1, the first capacitor 1 being coupled to the metal housing 9;
a second capacitor 2, the second capacitor 2 being coupled to the metal housing 9;
the first inductor 11, the first inductor 11 is coupled to the first capacitor 1 and the second capacitor 2, respectively.
The first inductor 11 is connected in series to the common ground GND10. Optionally, the first inductor 11 is a magnetic bead.
In the embodiment shown in fig. 2, the tamper protection circuit further comprises:
a third capacitor 3, the third capacitor 3 being coupled to the metal housing 9;
a fourth capacitor 4, the fourth capacitor 4 being coupled to the metal housing 9;
a second inductor 12, the second inductor 12 being coupled to the third capacitor 3 and the fourth capacitor 4, respectively; the anti-interference protection circuit further comprises a power line Vcc7, and the second inductor 12 is connected in series with the power line Vcc7.
The anti-interference protection circuit further comprises:
a fifth capacitor 5, the fifth capacitor 5 being coupled to the common ground GND10;
a sixth capacitor 6, the sixth capacitor 6 being coupled to the common ground GND10;
the third inductor 13, the third inductor 13 is coupled to the fifth capacitor 5 and the sixth capacitor 6 respectively;
the anti-interference protection circuit further comprises a signal line Out8, and the third inductor 13 is connected in series with the signal line Out8.
In some embodiments, the third inductance 13 is a magnetic bead.
In some embodiments, power line Vcc7 and/or signal line Out8 are connected to common ground GND10 through a bi-directional TVS tube.
TVS (Transient Voltage Suppressor) the TVS tube is also called a transient suppression diode, and is used for absorbing surge power, and can bear reverse voltage impact in a very short time, so that a voltage clamp between two electrodes is positioned at a specific voltage, and the impact on a following circuit is avoided.
In the present embodiment, the power supply line Vcc7 is connected to the common ground GND10 through the first bidirectional TVS pipe 14, and the signal line Out8 is connected to the common ground GND10 through the second bidirectional TVS pipe 15.
And carrying out electrostatic discharge immunity (ESD) test on the anti-interference protection circuit of the existing metal shell device, and adopting ISO 10605:2008 test standard. When the existing anti-interference protection circuit is in power-on test, the fluctuation of output voltage exceeds +/-40 mv when air discharge is +/-15 kV and contact discharge is +/-8 kV, and the EMC protection requirement of class A is not met.
The electrostatic discharge test is used for testing the anti-interference capability of the product on simulating the electrostatic discharge condition of a human body, and the interference energy is simulated by an electrostatic discharger and a discharge gun and is directly applied to the parts such as gaps, screws, metal surfaces and the like on the surface of the sample. For a product on the metal surface, a contact discharge mode is adopted, and the highest voltage level is applied to +/-8 kV; for nonmetallic surface products, an air discharge mode is adopted, and the voltage level is applied to +/-15 kV.
From test positioning analysis, it is known that the interference is directly injected into the interior through the wire harness, and a space coupling form exists, and by changing the interference path while the port filtering, as in the embodiment shown in fig. 2, a pi-type filtering circuit is added to the ports of the power line Vcc7, the common ground line GND10 and the signal line Out8, wherein optionally, the first capacitor 1, the second capacitor 2, the third capacitor 3, the fourth capacitor 4, the fifth capacitor 5 and the sixth capacitor 6 adopt 1nF, the first inductor 11, the second inductor 12 and the third inductor 13 adopt hundred mega-impedance 2000 Ω magnetic beads, and the first bidirectional TVS tube 14 and the second bidirectional TVS tube 15 adopt 150W TVS. The anti-interference protection circuit shown in fig. 2 meets the protection requirement of the class a through testing.
In some embodiments, pi-type filtering circuits are used on the power line Vcc7, the common ground line GND10 and the signal line Out8, wherein the capacitance value selected in pi-type filtering is usually between 1nF and 0.1uF, in order to have better filtering effect on high-frequency interference signals, in particular embodiments, a 1nF capacitor is used, and in combination with a high-current injection test with the frequency of 1MHz-400MH and the intensity of 100mA, hundred mega-impedance 2000 Ω magnetic beads are used to form pi-type filtering to reduce the interference current intensity and improve the anti-interference capability of the metal shell device.
In some embodiments, in operation, such as under high current injection, pi-type filtering used on the power line Vcc7, the signal line Out8 and the common ground GND10 converts the interference current into a dot voltage through the first capacitor, and then the high-resistance anti-magnetic bead and the second capacitor can greatly reduce the interference current signal flowing in, thereby reducing the high-frequency high-current interference signal intensity in the wire harness.
In electrostatic discharge and electromagnetic interference tests, pi-type filtering can change the path of an interference loop through contact of the capacitor and the metal shell 9, so that disturbance current flows back to the grounding plate before interference with an internal circuit.
In the circuit, peak voltage caused by power switch action or unstable interference source is carried out under high-intensity interference, and the peak voltage can be absorbed and filtered by the TVS diode, so that the stability of the internal circuit is ensured.
At present, most of anti-interference protection of products only adopts a capacitor or a TVS diode as a protection device, which completely depends on the type and the characteristics of the capacitor or the TVS diode, and once the devices are damaged, the anti-interference protection characteristics of the products cannot be guaranteed. In actual anti-interference test or production and life, products often need to face more complex test or use environments, and thus anti-interference protection of the products needs to have better and more complete protection characteristics. The protection performance of pi-type filtering can be realized through device combination, and especially, a more complete protection effect can be realized on the treatment of contacting the metal shell 9, if only a certain capacitor is damaged, a certain protection effect can still be achieved, and peak voltage and the like generated by power on-off, unstable interference sources and the like under high-intensity interference can be further effectively absorbed and filtered by matching with the TVS diode.
In sum, compared with a common single-filtering capacitor or TVS diode, the embodiment of the application can cope with more anti-interference test conditions and production and living use environments, and the anti-interference capability and the safety performance of the product are better ensured. The application enables the type of products to pass through related A-level EMC tests, including electrostatic 8kV contact discharge and 15kV air discharge tests under the power-on or power-off modes of the products, high-current injection tests with the frequency of 1MHz-400MH and the intensity of 100mA, electromagnetic interference tests with the frequency band of 400MHz-3GHz and the field intensity of 100V/m, and the like.
In a specific embodiment, the capacitor may be connected to the metal housing 9 by an flying wing, such as by drawing two symmetrical copper sheets from the PCB panel and contacting the metal housing 9 by a rivet connection. Preferably, the copper sheet may be rectangular in size with a length of 9mm and a width of 2.54 mm. The size of the specific copper sheet can be selected according to actual needs.
It should be noted that the pi-type filtering positions of the metal casing 9 connected to the power line Vcc7, the signal line Out8 and the common ground GND10 may be freely movable, and in other embodiments, may be located at the lower end of the bidirectional TVS tube.
In some embodiments, the overall tamper protection circuitry is smaller in view of improving space utilization, alternatively, the capacitors and inductors (or magnetic beads) may be in a patch package configuration.
The anti-interference protection circuit of the metal shell device provided by the embodiment can be used for an EMC anti-interference test of projects such as static discharge test comprising 8kV contact discharge and 15kV air discharge, 100mA high-current injection with the frequency of 1MHz-400MHz and the like, and meanwhile, the device damage phenomenon caused by static electricity can be effectively reduced in actual production.
Referring to fig. 3, the difference between the third embodiment of the present application and the embodiment shown in fig. 1 and 2 includes that, in the embodiment shown in fig. 3, the filter circuit includes a capacitor. The anti-interference protection circuit of the metal shell device provided in fig. 3 is characterized in that a filter circuit is connected between a common ground GND10 and a metal shell 9, the filter circuit comprises a first capacitor 1, and two ends of the first capacitor 1 are respectively connected with the common ground GND10 and the metal shell 9.
In some embodiments, at least one line of the anti-interference protection circuit system is connected in series with an inductor in order to filter out high frequency interference and suppress noise.
The anti-interference protection circuit provided by the application can be applied to a three-wire metal shell device, wherein the three-wire metal shell device is separated from the positive end of a power supply and the positive end of a signal output, but the three-wire metal shell device shares one COM end (namely a common ground wire GND 10), namely the three-wire metal shell device comprises a power supply wire, a signal wire and the common ground wire GND10; the inductor may be connected in series with any one of the common ground GND10, the power supply line Vcc7, or the signal line Out8.
Optionally, the inductor comprises a magnetic bead or a wire wound inductor.
In some embodiments, as shown in fig. 3, the tamper resistant protection circuit of the metal-case device includes a third capacitor 3, a fourth capacitor 4, a fifth capacitor 5, a sixth capacitor 6, and a first capacitor 1, and a second inductor 12 and a third inductor 13.
The first capacitor 1 can reduce the influence of a high-frequency interference signal taking the ground level as a reference on a circuit, and can suppress the transient common mode voltage difference between the circuit and an interference source. A high frequency path is formed by the first capacitor 1 so that the interference generated by the inner module 17 flows via the capacitor into the metal housing 9 into the ground, avoiding the antenna radiation formed by the high frequency interference.
The pi-type filter composed of a capacitor, magnetic beads and a capacitor is connected to a power line Vcc7, specifically, a second inductor 12 (magnetic beads are adopted in the embodiment) is connected to the power line Vcc7 in series, two ends of each magnetic bead are respectively connected with a third capacitor 3 and a fourth capacitor 4, the third capacitor 3 and the fourth capacitor 4 are connected with a metal shell 9, the first capacitor 1 is connected with the metal shell 9 in parallel on a common ground GND10, and a discharging passage is provided for electrostatic charges of the metal shell 9.
In some embodiments, the third capacitor 3, the fourth capacitor 4 and the first capacitor 1 all use patch capacitors. The magnetic beads can also adopt a patch structure.
In some embodiments, the first and second bi-directional TVS pipes 14 and 15 are connected to the common ground GND10 on the power line Vcc7 and the signal line Out8, respectively, to provide overvoltage protection.
The signal line Out8 is connected with pi-type filtering consisting of capacitance, magnetic beads and capacitance, and the specific connection method is that a third inductor 13 (magnetic beads are adopted in the specific embodiment) is connected in series on the signal line Out8, two ends of the magnetic beads are respectively connected with a fifth capacitance 5 and a sixth capacitance 6, the fifth capacitance 5 and the sixth capacitance 6 are connected with a common ground wire GND10, and the anti-interference capability of the circuit is enhanced. Optionally, the fifth capacitor 5 and the sixth capacitor 6 use patch capacitors. The fifth capacitor 5 and the sixth capacitor 6 may be connected to the metal casing 9 by means of flying wings. The fifth capacitor 5 and the sixth capacitor 6 can filter out high-frequency noise of the signal, and avoid the pi-type filter circuit from being disabled because the noise is strung back to the signal line.
In some embodiments, such as large current injection, pi-type filtering used on the power line Vcc7 and the signal line Out8 converts the interference current into a dot voltage through the first capacitor, and then the high-resistance anti-magnetic bead and the second capacitor can greatly reduce the interference current signal flowing in, thereby reducing the high-frequency large-current interference signal intensity in the wire harness. In the electrostatic discharge and electromagnetic interference test, pi-type filtering at the power line Vcc7 and the first capacitor 1 at the common ground GND10 can change the path of the disturbance loop by the contact of the capacitor with the metal shell 9, so that the disturbance current flows back to the ground plate before the disturbance of the internal circuit. In the circuit, peak voltage caused by power switch action and the like or unstable interference sources is carried out under high-intensity interference, and the peak voltage can be absorbed and filtered by the TVS diode, so that the stability of an internal circuit is ensured.
In some embodiments, a bleed path may be provided to the first capacitor 1 and the megaohm resistor, such as a resistor of 1m to 2 m.
It should be noted that the pi-type filtering positions used on the power line Vcc7 and the signal line Out8 may be freely movable, and in other embodiments, may be located at the lower end of the bidirectional TVS diode.
It should be noted that, the position of the first capacitor 1 connected to the metal shell 9 on the common ground GND10 may be freely moved, and in other embodiments, may be located at the lower end of the bidirectional TVS tube.
The components in the anti-interference protection circuit, especially the components used for processing the common ground GND10, should be located as close to the external connection point as possible.
In some embodiments, the filter circuit includes a first capacitor 1, the first capacitor 1 is coupled to the metal housing 9, and a first inductor 11 is connected in series to the common ground GND10.
In some embodiments, only the capacitive connection to the metal housing 9 is used on the external power supply line Vcc7 and the signal line Out8, providing a bleed path for the electrostatic charge of the metal housing 9. The locations of the capacitors on power line Vcc7 and signal line Out8 may be freely movable, and in other embodiments may be located at the lower end of the bi-directional TVS tube.
Referring to fig. 4, the fourth embodiment of the present application is different from the embodiment shown in fig. 3 in that, in the embodiment shown in fig. 4, a signal line Out8 is connected in series with a third inductor 13, and a common ground GND10 is connected in series with a first inductor 11.
As shown in fig. 4, the anti-interference protection circuit includes a common ground GND10 and a filter circuit connected between the common ground GND10 and the metal shell 9, the filter circuit includes a first capacitor 1 and a first inductor 11, the first capacitor 1 is coupled to the metal shell 9, and the first inductor 11 is connected in series with the common ground GND10.
In some embodiments, the anti-interference protection circuit further includes a power line Vcc7, the power line Vcc7 is connected in series with the second inductor 12, and the power line Vcc7 is coupled to the metal casing 9 through the fourth capacitor 4.
The anti-interference protection circuit further comprises a signal line Out8, and the signal line Out8 is connected in series with a third inductor 13.
In some embodiments, the first and second bi-directional TVS pipes 14 and 15 are connected to the common ground GND10 on the power line Vcc7 and the signal line Out8, respectively, to provide overvoltage protection.
When the anti-interference protection circuit of the existing metal shell device is subjected to a high-current injection immunity (BCI) test, ISO 11452-4:2011 is adopted, and the output voltage of the existing anti-interference protection circuit exceeds +/-40 mv at 150nm 370MHz CW, so that the requirement of class A is not met.
High current injection immunity (BCI) is one method of using a current injection probe to directly couple nuisance signals to wiring harnesses for immunity testing. The injection probe is a current transformer through which a wire harness of a Device Under Test (DUT) passes.
In some examples, using the embodiment shown in fig. 4, hundred mega-impedance 2000 Ω magnetic beads are connected in series on the power supply line Vcc7, the signal line Out8, and the common ground line GND10. Meanwhile, the capacitor with 1nF is added on the power line Vcc7 and the signal line Out8 to filter the metal shell 9, so that the path of an interference loop is changed, and the disturbance current can flow back to the grounding plate before interfering with the IC.
Aiming at the severe test requirement in the A-level EMC test and the working condition actually existing in daily production, the application can enable the product to pass certain related A-level EMC tests and effectively reduce the damage of the product caused by electromagnetic incompatibility in actual production.
In some embodiments, an electronic device 16 is provided, and a schematic structural diagram of the electronic device 16 is shown in fig. 5, including:
a metal housing 9, wherein a protected inner module 17 is arranged in the metal housing 9;
The metal casing 9 may be in direct contact with the outside, and may be used to wrap the inner module 17 and the anti-interference protection circuit by riveting or the like.
The internal module 17 is a working device that can work normally under normal power supply, including but not limited to a sensor module and a PCB circuit board.
The metal shell 9 can be in direct contact with the inner module 17.
In some embodiments, a certain separation distance may be provided between the inner module 17 and the metal casing 9. In a specific embodiment, optionally, a space distance of more than 0.2mm is kept between the metal shell 9 and the inner module 17; or is not limited to the use of insulating materials such as insulating tape, insulating glue or plastic blocks to ensure that the shortest path for static electricity propagation cannot be formed. The spatial distance here refers to the vertical distance between the plane of the inner module 17 and the plane of the metal casing 9, which may be, for example, 0.3mm or the like, and in a specific embodiment may be set as desired. The internal space is limited, and the design of the protection circuit needs to consider the space allowance.
In some embodiments, the metal shell 9 is further provided with a common terminal for grounding the common ground GND10, a power terminal for grounding a power line, and a signal terminal for grounding a signal line; the internal module 17 is connected to the common terminal, the power terminal and the signal terminal, that is, the internal module 17 is a three-wire device, three wires of the internal module 17 are led out to an external connection point through a connection wire, and the protection circuit 18 is connected to the led out connection point. Components in the protection circuit 18, particularly components used on the common ground GND10 line, should be located as close to external connection points as possible, so as to minimize the propagation path of static electricity.
The electronic equipment 16 can realize anti-interference protection of a three-wire metal shell device.
It should be noted that, as shown in fig. 5, the electronic device 16, the protection circuit 18, and the internal module 17 are separate structures; in other embodiments, the protection circuit 18 and the internal module 17 may be designed as one module.
The anti-interference protection circuit of the metal shell device provided by the application comprises a capacitor, wherein the filter circuit between the common ground GND10 and the metal shell 9; at least one line of the anti-interference protection circuit system is connected with an inductor in series; the capacitor provides a discharge passage for the electrostatic charge of the metal shell, so that the anti-interference capability of the metal shell device is improved; the influence of the high-frequency interference signal taking the ground level as a reference on the circuit can be reduced through the filter circuit, and the transient common mode voltage difference between the circuit and the interference source can be restrained; the high-frequency interference is filtered by using the inductor, and the noise can be restrained by absorption and reflection.
When the filter circuit comprises a pi-type filter circuit, the flowing interference current signal can be greatly reduced, so that the intensity of the high-frequency high-current interference signal in the wire harness is reduced.
The electronic equipment 16 provided by the application is provided with the anti-interference protection circuit of the metal shell device, so that when the electronic equipment encounters electrostatic discharge, large circuit injection interference or electromagnetic wave interference and the like, the influence of external interference signals on the inside of the device is reduced, and the anti-interference capability and the service life of the internal module device are improved.
The anti-interference protection circuit and the electronic equipment of the metal shell device provided by the embodiment of the application are described in detail, and specific examples are applied to illustrate the principle and the implementation of the application, and the description of the above embodiment is only used for helping to understand the technical scheme and the core idea of the application; those of ordinary skill in the art will appreciate that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.
Claims (11)
1. An anti-interference protection circuit of a metal shell device, which is characterized by comprising a public ground wire and a filter circuit connected between the public ground wire and the metal shell, wherein the filter circuit at least comprises a capacitor, and the capacitor is coupled to the metal shell;
at least one line of the anti-interference protection circuit system is connected with an inductor in series.
2. The tamper resistant protection circuit of a metal-case device of claim 1, wherein the filter circuit comprises a pi-type filter circuit; the pi-type filter circuit includes:
a first capacitor coupled to the metal housing;
a second capacitor coupled to the metal housing;
the first inductor is coupled to the first capacitor and the second capacitor respectively.
3. The tamper resistant protection circuit of a metal case device of claim 1, wherein the common ground is connected in series with a first inductor.
4. The tamper resistant protection circuit of a metal shell device according to claim 3 further comprising a power cord connected in series with a second inductor, the power cord coupled to the metal shell through a fourth capacitor.
5. The tamper resistant protection circuit of a metal shell device according to claim 4 further comprising a signal line, the signal line being connected in series with a third inductor.
6. The tamper resistant protection circuit of a metal case device of claim 1, wherein the tamper resistant protection circuit further comprises:
a third capacitor coupled to the metal housing;
a fourth capacitance coupled to the metal housing;
a second inductor coupled to the third capacitor and the fourth capacitor, respectively;
the anti-interference protection circuit further comprises a power line, and the second inductor is connected in series with the power line.
7. The tamper resistant protection circuit of a metal shell device according to claim 6 further comprising a signal line, the signal line being connected in series with a third inductor.
8. The tamper resistant protection circuit of a metal-case device of claim 1, wherein the tamper resistant protection circuit further comprises:
a fifth capacitor coupled to the common ground;
a sixth capacitance coupled to the common ground;
a third inductor coupled to the fifth capacitor and the sixth capacitor, respectively;
the anti-interference protection circuit further comprises a signal wire, and the third inductor is connected in series with the signal wire.
9. The tamper resistant protection circuit of a metal shell device according to claim 1 further comprising a power line and a signal line, the power line and/or the signal line being connected to the common ground through a bi-directional TVS tube.
10. The tamper resistant protection circuit of a metal shell device according to claim 1, further comprising a power line and a signal line, wherein the power line and/or the signal line is connected to the metal shell by a capacitor.
11. An electronic device, comprising:
the metal shell is internally provided with a protected internal module, and the internal module is provided with a public ground wire;
the protection circuit adopts the anti-interference protection circuit of the metal shell device according to any one of claims 1-10.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310240507.3A CN116131796B (en) | 2023-03-14 | 2023-03-14 | Anti-interference protection circuit of metal shell device and electronic equipment |
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| CN202310240507.3A CN116131796B (en) | 2023-03-14 | 2023-03-14 | Anti-interference protection circuit of metal shell device and electronic equipment |
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| CN104734491A (en) * | 2013-12-18 | 2015-06-24 | Ls产电株式会社 | Low voltage electromagnetic interference filter of electric vehicle |
| CN104135148A (en) * | 2014-07-17 | 2014-11-05 | 青岛歌尔声学科技有限公司 | USB (Universal Serial Bus) interface circuit |
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| CN116131796B (en) | 2023-06-30 |
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