A method for lightning protection of an on-board communication interface

Abstract

This application provides a lightning protection method for airborne communication interfaces, belonging to the technical field of airborne measurement and control for harsh environments. Specifically, it includes the following steps: selecting a suitable breakdown voltage for the communication interface voltage requiring protection; determining the power of the transient suppression tube based on the corresponding waveform of the lightning protection level; selecting a suitable transient suppression tube; constructing a low-capacitance lightning suppression unit on the communication line; connecting a rectifier diode VD1 in series with the transient suppression tube; the junction capacitance of the rectifier diode VD1 is less than the maximum capacitance requirement of the communication line to ground; the anode of the rectifier diode VD1 is connected to the communication line; the cathode of the rectifier diode VD1 is connected to the cathode of the transient suppression tube; and the anode of the transient suppression tube is grounded. This solution reduces the capacitance of the lightning protection circuit while ensuring that the protection voltage does not increase significantly, guaranteeing sufficient protection power and protecting the normal operation of the communication line.

Description

Technical Field

[0001] This application relates to the field of airborne measurement and control in harsh environments, and in particular to a lightning protection method for airborne communication interfaces. Background Technology

[0002] Lightning poses a significant threat to airborne electronic equipment. It can directly or indirectly affect these devices, and excessive voltage and current can damage or burn out interface circuits and components, causing malfunctions and potentially serious safety incidents. Currently, airborne electronic equipment generally has specific lightning protection requirements. For example, civil aircraft electronic equipment must pass the lightning transient sensitivity tests outlined in Chapter 22 of DO-160G. These tests are categorized into five levels (1-5) based on the level of protection provided by the installation environment. Levels 4 and 5 are suitable for equipment and interconnecting wires installed in harsh electromagnetic environments.

[0003] For general interface circuits of electronic devices, lightning protection can be achieved using transient voltage suppressor (TVS) diodes. When a lightning strikes the device with hundreds or thousands of volts, the TVS diode is instantly broken down, clamping the interface voltage to its maximum clamping voltage (typically only a few to tens of volts), thus protecting the downstream interface circuitry from damage due to excessive voltage. Because different lightning protection levels require different injected lightning voltages and currents, higher lightning protection levels necessitate higher-power TVS diodes, which are also larger in size.

[0004] For communication interfaces of electronic devices, the junction capacitance of ordinary transient voltage suppressors (TVS) is very large, reaching thousands or even tens of thousands of pF. During lightning protection of communication lines, this excessive junction capacitance prevents high-speed communication interfaces such as Ethernet from functioning properly. Typically, the capacitance to ground of such high-speed communication lines is at most tens of pF. Therefore, the capacitance of the protection circuit must be reduced while ensuring sufficient protection power. For higher lightning protection levels, such as Level 4 and Level 5, larger TVS are required, but their even larger junction capacitance cannot meet the requirements. Higher power lightning protection circuits with smaller capacitance are needed to provide protection while simultaneously meeting power and communication function requirements. Due to the high integration and precision of aviation communication electronic circuits, excessive use of TVS to increase printed circuit board area and product size is often undesirable. It is necessary to consider reducing the number of TVS or reusing them. For example, differential communication electronic circuits can consider reusing TVS on differential lines to reduce the number of TVS used.

[0005] In some capacitance-sensitive circuits, such as vibration charge acquisition circuits, excessively large capacitance in the lightning protection circuit can cause charge leakage, leading to acquisition failure or decreased accuracy. Therefore, the capacitance of the protection circuit must be reduced, while ensuring that the protection voltage does not increase too much and that the protection power is sufficient. Summary of the Invention

[0006] In view of this, this application provides a lightning protection method for airborne communication interfaces, which solves the problems in the prior art, reduces the capacitance of the protection circuit, and ensures that the protection voltage does not increase too much, thus protecting the normal operation of the communication line.

[0007] The lightning protection method for airborne communication interfaces provided in this application adopts the following technical solution:

[0008] A lightning protection method for airborne communication interfaces includes the following steps:

[0009] Select an appropriate breakdown voltage based on the communication interface voltage to be protected, determine the transient suppression tube power according to the corresponding waveform of the lightning protection level, and select an appropriate transient suppression tube.

[0010] A low-capacitance lightning suppression unit is constructed on the communication line. A rectifier diode VD1 is connected in series with the transient suppression tube. The junction capacitance of the rectifier diode VD1 is smaller than the communication-to-ground capacitance. The anode of the rectifier diode VD1 is connected to the communication line, and the cathode of the rectifier diode VD1 is connected to the cathode of the transient suppression tube. The anode of the transient suppression tube is grounded.

[0011] Optionally, the process of constructing a low-capacitance lightning suppression unit on the communication line further includes: connecting a rectifier diode VD2 in parallel with the series circuit of the transient suppression tube and the rectifier diode VD1 on the communication line, wherein the cathode of the rectifier diode VD2 is connected to the communication line and the anode of the rectifier diode VD2 is grounded.

[0012] Optionally, when the lightning protection level is greater than 3, multiple low-capacitance lightning suppression units are connected in parallel on the communication line to form a low-capacitance lightning suppression unit array to meet the power requirements of high-level lightning protection. It is also ensured that the sum of the capacitances of the multiple low-capacitance lightning suppression units is less than the maximum capacitance requirement of the communication line to ground.

[0013] Optionally, when the communication line is a differential communication line, a low-capacitance lightning suppression unit is connected to both the positive and negative signal lines of the differential communication line, and the two low-capacitance lightning suppression units share a transient suppression tube to form a differential low-capacitance lightning suppression unit.

[0014] Optionally, when the lightning protection level is greater than 3, multiple differential low-capacitance lightning suppression units are connected in parallel on the differential communication line to form a differential low-capacitance lightning suppression unit array to meet the power requirements of high-level lightning protection. It is also ensured that the sum of the capacitances of the multiple differential low-capacitance lightning suppression units is less than the maximum capacitance requirement of the communication line to ground.

[0015] Optionally, depending on the protection level and circuit type, a low-capacitance lightning suppression unit or a low-capacitance lightning suppression unit array or a differential low-capacitance lightning suppression unit or a differential low-capacitance lightning suppression unit array can be connected to a capacitance-sensitive interface circuit for lightning protection of the capacitance-sensitive interface circuit, wherein the capacitance-sensitive interface circuit includes a vibration charge acquisition interface circuit.

[0016] Optionally, the power calculation formula for the transient suppression diode is as follows:

[0017] P = I P ×V C

[0018] I P =(V OC -V C ) / Z S

[0019] Z S =V OC / I SC

[0020] Among them, Z S V is the source impedance. OC I is the open-circuit voltage. SC It is the short-circuit current; I P For transient peak current, V C This is the maximum clamping voltage.

[0021] The capacitance to ground of the low-capacitance lightning suppression unit is:

[0022] C = C JTVS *C J1 / (C JTVS +C J1 )+C J2 ;

[0023] Among them, C J1 It is the forward junction capacitor of VD1, C JTVS It is the transient suppression junction capacitance, C J2 It is the VD2 reverse junction capacitance;

[0024] C is approximately equal to C J1 C J1 C JTVS The low-capacitance lightning suppression unit reduces the ground capacitance of the lightning protection circuit to one-thousandth to one-tenth of its original value, from one-hundredth to one-tenth.

[0025] In summary, this application includes the following beneficial technical effects:

[0026] The low-capacitance lightning suppression unit consists of a rectifier diode VD1 and a transient voltage suppressor. Because the selected rectifier diode has a large current carrying capacity and a very small junction capacitance (only a few pF), its series connection with the transient voltage suppressor forms a protective circuit that effectively reduces the capacitance of the communication line to ground from thousands of pF to only a few pF, thus ensuring 100 Mbps and 1 Gbps communication speeds. Furthermore, since the rectifier diode's forward voltage is less than 1V during lightning strikes, it does not significantly increase the communication protection voltage, ensuring a low protection voltage and protecting the communication line for normal operation. This lightning suppression unit can meet the lightning protection requirements for communication lines at level 3 and above.

[0027] In the low-capacitance lightning suppression unit, the rectifier diode VD2, running from ground to the communication line, conducts when a negative lightning voltage strikes the communication signal line, clamping the signal line and thus protecting it. Because the junction capacitance of the rectifier diode is very small (in the pF range), much smaller than that of the transient suppression diode, its impact on the communication line is minimal and meets communication requirements.

[0028] An array composed of low-capacitance lightning suppression units connected in parallel improves lightning protection power, thereby meeting higher lightning protection requirements. Generally, two low-capacitance lightning suppression units connected in parallel can meet the lightning protection requirements of communication lines of level 4 or above. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 Inject waveform 4 into the DO-160G lightning pins;

[0031] Figure 2 It is a low-capacitance lightning suppression unit;

[0032] Figure 3 It is a low-capacitance lightning suppression unit array;

[0033] Figure 4 It is a differential low capacitance lightning suppression unit;

[0034] Figure 5 It is a differential low capacitance lightning suppression unit array. Detailed Implementation

[0035] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0036] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0038] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0039] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0040] This application provides a lightning protection method for airborne communication interfaces.

[0041] A lightning protection method for airborne communication interfaces includes the following steps:

[0042] Select an appropriate breakdown voltage based on the communication interface voltage to be protected, determine the transient suppression tube power according to the corresponding waveform of the lightning protection level, and select an appropriate transient suppression tube (TVS tube).

[0043] A low-capacitance lightning suppression unit is constructed on the communication line. A rectifier diode VD1 is connected in series with the transient suppression tube. The junction capacitance of the rectifier diode VD1 is smaller than the communication-to-ground capacitance. The anode of the rectifier diode VD1 is connected to the communication line, and the cathode of the rectifier diode VD1 is connected to the cathode of the transient suppression tube. The anode of the transient suppression tube is grounded.

[0044] Ordinary transient voltage suppressors have very large junction capacitances, which can reach thousands or even tens of thousands of pF. When used for lightning protection of communication lines, the large junction capacitance can prevent high-speed communication lines such as Ethernet from communicating normally.

[0045] The low-capacitance lightning suppression unit, as described above Figure 2 As shown, the circuit consists of a rectifier diode VD1 and a transient voltage suppressor. Because the selected rectifier diode has a large current-carrying capacity and a very small junction capacitance (only a few pF), its series connection with the transient voltage suppressor forms a protective circuit that effectively reduces the capacitance of the communication line to ground from thousands of pF to only a few pF, thus ensuring communication speeds of hundreds of megabits and gigabits. Furthermore, since the rectifier diode's forward voltage is less than 1V during lightning strikes, it does not significantly increase the communication protection voltage, ensuring a low protection voltage and protecting the communication line for normal operation. This lightning suppression unit can meet the lightning protection requirements for communication lines of level 3 and above.

[0046] The process of constructing a low-capacitance lightning suppression unit on a communication line also includes: connecting a rectifier diode VD2 in parallel with a series circuit of a transient suppression transistor and a rectifier diode VD1 on the communication line, with the cathode of the rectifier diode VD2 connected to the communication line and the anode of the rectifier diode VD2 grounded. The rectifier diode VD2 can clamp to ground, ensuring that when lightning generates a negative voltage on the communication line, the negative voltage is clamped to below 1V, preventing damage to the communication circuit.

[0047] In the low-capacitance lightning suppression unit, the rectifier diode VD2, running from ground to the communication line, conducts when a negative lightning voltage strikes the communication signal line, clamping the signal line and thus protecting it. Because the junction capacitance of the rectifier diode is very small (in the pF range), much smaller than that of the transient suppression diode, its impact on the communication line is minimal and meets communication requirements.

[0048] When the lightning protection level is greater than 3, multiple low-capacitance lightning suppression units are connected in parallel on the communication line to form a low-capacitance lightning suppression unit array. It is ensured that the sum of the capacitances of the multiple low-capacitance lightning suppression units is less than the maximum capacitance requirement of the communication line to ground.

[0049] The low-capacitance lightning suppression unit array, as described above Figure 3 As shown, an array composed of low-capacitance lightning suppression units connected in parallel improves lightning protection power, thereby meeting higher lightning protection requirements. Generally, two low-capacitance lightning suppression units connected in parallel can meet the lightning protection requirements of communication lines of level 4 or above.

[0050] Because the low-capacitance lightning suppression units are connected in parallel, the lightning protection power is doubled while the clamping protection voltage remains unchanged, thus improving the lightning protection level. Although connecting two low-capacitance lightning suppression units in parallel doubles the capacitance to ground of the communication line, the capacitance to ground of the low-capacitance lightning suppression unit is very small, much smaller than the junction capacitance of the transient suppression tube, so the impact on the communication line is minimal, and it can meet the Level 4 lightning protection requirements for communication networks with speeds of 100 Mbps and above. While meeting communication speed requirements, the number of low-capacitance lightning suppression units connected in parallel can be increased to further improve the lightning protection level, such as the highest Level 5 lightning protection for airborne equipment.

[0051] When the communication line is a differential communication line, a low-capacitance lightning suppression unit is connected to both the positive and negative signal lines of the differential communication line. The two low-capacitance lightning suppression units share a transient suppression tube to form a differential low-capacitance lightning suppression unit. Rectifier diodes VD1 and VD2 are connected to the positive signal line, and rectifier diodes VD3 and VD4 are connected to the negative signal line. The anode of rectifier diode VD1 and the anode of rectifier diode VD3 are both connected to the positive signal line. The cathodes of rectifier diodes VD1 and VD3 are connected to the cathode of the same transient voltage suppressor (VT) diode, and the anode of the VT is grounded. The cathode of rectifier diode VD2 is connected to the positive signal line, and the cathode of rectifier diode VD4 is connected to the negative signal line. The anodes of rectifier diodes VD2 and VD4 are grounded. Rectifier diode VD2 is connected in parallel with the series circuit of positive diode VD1 and VT on the positive signal line, and rectifier diode VD4 is connected in parallel with the series circuit of positive diode VD3 and VT on the negative signal line.

[0052] The differential low capacitance, such as Figure 4As shown, the circuit consists of four low-junction-capacitance rectifier diodes and one transient voltage suppressor (VT) diode. The specific series and parallel connections are shown. Since the VT, especially the high-power VT, is relatively large, this circuit can save on the number of VT diodes and reduce the board area. Because the selected rectifier diodes have high current carrying capacity and very small junction capacitance (only a few pF), their series connection with the VT effectively reduces the capacitance of the communication line to ground, decreasing it from thousands of pF to only a few pF, thus ensuring 100 Mbps and 1 Gbps communication speeds. Furthermore, since the rectifier diodes have a forward voltage of less than 1V during lightning strikes, they do not significantly increase the communication protection voltage, ensuring a low protection voltage and protecting the communication line for normal operation. The rectifier diodes in the low-capacitance lightning suppression unit, running from ground to the communication line, conduct when there is a negative lightning voltage on the communication signal line, clamping the communication signal line and thus protecting it.

[0053] The differential low-capacitance lightning suppression unit has the same capacitance to ground for each communication signal line as the non-differential low-capacitance lightning suppression unit, thus ensuring communication speed while reducing transient suppression tubes. However, when lightning strikes two communication cables simultaneously, the protection effect is lower than using separate low-capacitance lightning suppression units.

[0054] When the lightning protection level is greater than 3, multiple differential low-capacitance lightning suppression units are connected in parallel on the differential communication line to form a differential low-capacitance lightning suppression unit array. The sum of the capacitances of the multiple differential low-capacitance lightning suppression units must be less than the maximum capacitance requirement of the communication line to ground.

[0055] The differential low capacitance lightning suppression unit array, as described above Figure 5 As shown, it is composed of differential low capacitance lightning suppression units connected in parallel, which improves the lightning protection power and thus meets the requirements of higher lightning levels. Generally, two differential low capacitance lightning suppression units connected in parallel can meet the lightning protection requirements of differential communication lines of level 4 or above.

[0056] Because the differential low-capacitance lightning suppression units are connected in parallel, the lightning protection power is doubled while the clamping protection voltage remains unchanged, thus improving the lightning protection level. Although the parallel connection of two differential low-capacitance lightning suppression units doubles the capacitance to ground of the communication line, the capacitance to ground of the differential low-capacitance lightning suppression unit is very small, much smaller than the junction capacitance of the transient suppression tube, and the impact on the communication line is minimal. This can meet the Level 4 lightning protection requirements for communication networks with speeds of 100 Mbps and above. While meeting communication speed requirements, the number of differential low-capacitance lightning suppression units connected in parallel can be increased to further improve the lightning protection level, such as to the highest Level 5 lightning protection for airborne equipment.

[0057] In one embodiment, a lightning protection method for an airborne communication interface includes the following steps: selecting an appropriate breakdown voltage based on the communication interface voltage to be protected, determining the TVS diode power according to the corresponding waveform of the lightning protection level, and selecting an appropriate TVS diode.

[0058] The power rating of the TVS diode can be calculated based on waveform 4 injected into the DO-160G lightning pin. The voltage and current of waveform 4 are shown in Table 1. Figure 1 As shown.

[0059]

[0060] The formula for calculating the power of a transient suppression diode is: P = I P ×V C

[0061] I P =(V OC -V C ) / Z S

[0062] Z S =V OC / I SC

[0063] Among them, Z S V is the source impedance. OC I is the open-circuit voltage. SC It is the short-circuit current; I P For transient peak current, V C This is the maximum clamping voltage.

[0064] For level 3 lightning, V OC =300V, I SC =60A, Z S =5Ω, if the protection voltage of the communication circuit is V C =20V, then I P =56A, P=1120W. Based on waveform 4, a TVS diode with a peak power of 6.4µs that can reach 1120W and a peak power of 69µs that can reach 560W needs to be selected.

[0065] Next, select a rectifier diode with a junction capacitance smaller than the required capacitance to ground for communication. For example, if Ethernet requires a capacitance to ground of no more than 50pF, then select a rectifier diode with a junction capacitance of less than 20pF. The diode should be selected such that the peak current at 6.4µs in waveform 4 can reach I... P The peak current of 69µs can reach I P 1 / 2 of the rectifier tube.

[0066] After selecting the TVS diode and rectifier diode, the structure is as follows: Figure 2 Low-capacitance lightning suppression unit.

[0067] The capacitance to ground of the low-capacitance suppression unit is:

[0068] C = C JTVS *C J1 / (C JTVS +C J1 )+C J2

[0069] Where C JTVS C is the junction capacitance of the TVS diode. J1 The capacitor that enables forward conduction of the rectifier diodes connected in series is typically the diffusion capacitor of the rectifier diode, C. J2 It is the VD2 reverse junction capacitance; C J1 and C J2 Very small (approximately a few pf to tens of pf), much smaller than C. JTVS With thousands of pf, therefore C JTVS *C J1 / (C JTVS +C J1 Since the value is very small, C ≈ C J1 +C J2 Therefore, the ground capacitance of the lightning protection circuit can be significantly reduced, so that the ground capacitance of the communication line can meet the communication requirements. Figure 2 In the low-junction capacitance lightning suppression unit, the rectifier diode VD2, running from ground to the communication line, conducts when a negative lightning voltage strikes the communication signal line, clamping the signal line and thus protecting it. This is equivalent to C in the formula. J2 The capacitance depends on the barrier capacitance of the rectifier diode. Since the voltage on communication lines is generally very low, only 1-3V, therefore C... J2 Very small, generally much smaller than C J1 Therefore, C = C J1 C J1 C JTVS The low-capacitance lightning suppression unit reduces the ground capacitance of the lightning protection circuit to one-thousandth to one-tenth of its original value, from one-hundredth to one-tenth.

[0070] The above steps complete the device selection and circuit construction of the low-capacitance lightning suppression unit, which can be used to protect communication signal lines. It can significantly reduce the ground capacitance of the lightning suppression circuit without increasing the protection voltage, thus ensuring the communication function and speed of the communication line.

[0071] When encountering higher lightning protection levels, such as levels 4 and 5, where the protection power is insufficient, a low-capacitance lightning suppression unit array is used to protect the communication interface.

[0072] The low-capacitance lightning suppression unit array, as described above Figure 3As shown, an array composed of low-capacitance lightning suppression units connected in parallel improves lightning protection power, thereby meeting higher lightning protection requirements. Generally, two low-capacitance lightning suppression units connected in parallel can meet the lightning protection requirements of communication lines at level 4 or above. It is necessary to ensure that the sum of the capacitances of the parallel low-capacitance lightning suppression units is less than the maximum capacitance to ground required by the communication line.

[0073] like Figure 3 The protection power of a low-capacitance lightning suppression unit array is n times that of a single low-capacitance lightning suppression unit. Generally, two low-capacitance lightning suppression units are sufficient to achieve level 4 lightning protection. When two low-capacitance lightning suppression units are used, the lightning protection power is twice that of a TVS diode.

[0074] For a level 4 lightning strike, according to the formula in step 1, V OC =750V, I SC =150A, Z S =5Ω, if the protection voltage of the communication circuit is V C =20V, then I P =146A, P=2920W. According to waveform 4, a TVS diode with a peak power of 2920W at 6.4µs and a peak power of 1460W at 69µs needs to be selected. Generally, TVS diodes capable of this level have large packages, and the rectifier diodes connected in series with them also have large packages to handle 150A current, resulting in large junction capacitances. Therefore, two low-capacitance lightning suppression units can be connected in parallel in an array for protection. Only TVS diodes with a peak power of 1460W at 6.4µs and a peak power of 730W at 69µs need to be selected, and the rectifier diodes only need to handle 75A current at 6.4µs. This ensures that the circuit design can be completed with smaller packaged components, and that the capacitance of the protection circuit remains low, only twice that of a single low-capacitance lightning suppression unit. From step 1, this capacitance is 2*C. J1 It is much smaller than the junction capacitance of a TVS diode, which can ensure the normal operation of the communication line.

[0075] For differential communication interfaces, since TVS diodes are generally large in package size, in order to save board space, the following can be used: Figure 4 The differential low-capacitance lightning suppression unit shown provides lightning protection. Compared to ordinary low-capacitance lightning suppression units, this circuit structure only requires one TVS diode to achieve lightning protection for two communication lines.

[0076] The selection of the TVS diode and rectifier diode is the same as in step 1, and the capacitance of the two differential communication lines to ground is also C. JTVS *C J1 / (C JTVS +C J1 )+C J2The analysis in step 1 shows that the capacitance is approximately C. J2 This refers to the junction capacitance of the rectifier diode, which is much smaller than that of the TVS diode, thus ensuring normal high-speed communication functionality. Simultaneously, the lightning protection power of each differential line in this circuit is the same as that of the low-capacitance lightning suppression unit, thereby guaranteeing lightning protection performance.

[0077] For differential communication interfaces requiring higher lightning protection levels, differential low-capacitance lightning suppression unit arrays can be used for protection.

[0078] like Figure 5 The protection power of a differential low-capacitance lightning suppression unit array is n times that of a single differential low-capacitance lightning suppression unit. Generally, two differential low-capacitance lightning suppression units are sufficient to achieve level 4 lightning protection. When two differential low-capacitance lightning suppression units are used, the lightning protection power is twice that of a TVS diode.

[0079] The selection of TVS and rectifier diodes can be determined based on the methods described above. When two differential low-capacitance lightning suppression units are used to form an array, the capacitance to ground of each communication line is twice that of a single differential low-capacitance lightning suppression unit. The capacitance to ground of a single differential low-capacitance lightning suppression unit can be determined from the analysis in step 1 to be approximately C. J1 The differential low-capacitance lightning suppression unit array has a capacitance of approximately 2*C. J1 The junction capacitance of the rectifier diode is twice that of the junction capacitance of the TVS diode, which is much smaller than that of the junction capacitance of the TVS diode, thus meeting the communication speed requirements.

[0080] Lightning protection methods for capacitor-sensitive interface circuits:

[0081] The aforementioned capacitance-sensitive interface circuits include vibration charge conditioning and acquisition interface circuits and other capacitance-sensitive circuits. When the line capacitance to ground is large, it will cause charge leakage, resulting in interface function failure or reduced signal conditioning and acquisition accuracy.

[0082] Step 1, the lightning protection method for the capacitor-sensitive interface circuit described above uses a low-capacitance lightning suppression unit to protect the capacitor-sensitive interface circuit. This significantly reduces the ground capacitance of the lightning suppression circuit without increasing the protection voltage, ensuring interface functionality and accuracy. See [link to low-capacitance lightning suppression unit] for details. Figure 2 For the selection of its TVS diode and transient suppression diode, please refer to a lightning protection method for airborne communication interfaces.

[0083] Step 2, the lightning protection method for capacitor-sensitive interface circuits described above uses an array of low-capacitance lightning suppression units to protect the capacitor-sensitive interface circuits, ensuring the functionality and accuracy of the interface circuits under high lightning protection levels (levels 4 and 5). The array of capacitor-sensitive lightning suppression units is shown below. Figure 3For the selection of its TVS diode and transient suppression diode, please refer to a lightning protection method for airborne communication interfaces.

[0084] Step 3, the lightning protection method for the capacitor-sensitive interface circuit described above uses a differential low-capacitance lightning suppression unit to protect the differential capacitor-sensitive interface circuit. This significantly reduces the ground capacitance of the lightning suppression circuit without increasing the protection voltage, ensuring interface functionality and accuracy. See [link to differential low-capacitance lightning suppression unit] for details. Figure 4 For the selection of its TVS diode and transient suppression diode, please refer to a lightning protection method for airborne communication interfaces.

[0085] Step 4: The lightning protection method for capacitor-sensitive interface circuits employs an array of differential low-capacitance lightning suppression units to protect the differential capacitor-sensitive interface circuits, ensuring the functionality and accuracy of the differential interface circuits under high lightning protection levels (levels 4 and 5). See the diagram for the differential low-capacitance lightning suppression unit array. Figure 5 For the selection of its TVS diode and transient suppression diode, please refer to a lightning protection method for airborne communication interfaces.

[0086] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An airborne communication interface lightning protection method, characterized in that, Includes the following steps: Select an appropriate breakdown voltage based on the communication interface voltage to be protected, determine the transient suppression tube power according to the corresponding waveform of the lightning protection level, and select an appropriate transient suppression tube. A low-capacitance lightning suppression unit is constructed on the communication line. A rectifier diode VD1 is connected in series with the transient suppression tube. The junction capacitance of the rectifier diode VD1 is less than the maximum capacitance requirement of the communication line to ground. The anode of the rectifier diode VD1 is connected to the communication line, the cathode of the rectifier diode VD1 is connected to the cathode of the transient suppression tube, and the anode of the transient suppression tube is grounded. The process of constructing a low-capacitance lightning suppression unit on a communication line also includes: connecting a rectifier diode VD2 in parallel with a series circuit of a transient suppression tube and a rectifier diode VD1 on the communication line, wherein the cathode of the rectifier diode VD2 is connected to the communication line and the anode of the rectifier diode VD2 is grounded. According to the protection level and circuit type, a low-capacitance lightning suppression unit or a low-capacitance lightning suppression unit array or a differential low-capacitance lightning suppression unit or a differential low-capacitance lightning suppression unit array is connected to the capacitor-sensitive interface circuit for lightning protection of the capacitor-sensitive interface circuit. The capacitor-sensitive interface circuit includes a vibration charge acquisition interface circuit. When the lightning protection level is greater than 3, multiple low-capacitance lightning suppression units are connected in parallel on the communication line to form a low-capacitance lightning suppression unit array to meet the power required for high-level lightning protection. When the communication line is a differential communication line, a low-capacitance lightning suppression unit is connected to both the positive and negative signal lines of the differential communication line. The two low-capacitance lightning suppression units share a transient suppression tube to form a differential low-capacitance lightning suppression unit.

2. The airborne communication interface lightning protection method of claim 1, wherein, When the lightning protection level is greater than 3, multiple differential low-capacitance lightning suppression units are connected in parallel on the differential communication line to form a differential low-capacitance lightning suppression unit array to meet the power required for high-level lightning protection.

3. The airborne communication interface lightning protection method of claim 1, wherein, The formula for calculating the power of a transient suppression diode is: P=I P xV C I P = (V OC -V C ) / Z S Z S =V OC / I SC Among them, Z S V is the source impedance. OC I is the open-circuit voltage. SC It is the short-circuit current; I P For transient peak current, V C This is the maximum clamping voltage.

4. The lightning protection method for airborne communication interfaces according to claim 1, characterized in that, The capacitance to ground of the low-capacitance lightning suppression unit is: C = C JTVS C J1 / (C JTVS +C J1 )+C J2 ; Among them, C J1 It is the forward junction capacitor of VD1, C JTVS It is the transient suppression junction capacitance, C J2 It is the VD2 reverse junction capacitor; C is approximately equal to C J1 , C J1 is one to ten percent of C JTVS , the low-capacitance lightning suppression unit reduces the ground capacitance of the lightning protection circuit to one to ten percent of the original value.

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