Lightning protection circuit applied to serial communication

Abstract

The utility model belongs to the technical field of lightning protection, and particularly relates to a lightning protection circuit applied to serial communication. Comprising a communication transformer circuit, two clamping protection circuits, two steady state matching circuits and a drive transceiver circuit, two ends of a secondary side of the communication transformer circuit are respectively connected with clamped points of the two clamping protection circuits; clamped points of the two clamping protection circuits are respectively connected with the input ends of the corresponding steady state matching circuits; the output ends of the two steady state matching circuits are respectively connected with the two input ends of the driving transceiver; and the output end of the driving transceiver is connected with the serial port transceiving module of the MCU processor to realize normal communication.

Description

Technical Field

[0001] This utility model belongs to the field of lightning protection technology, specifically relating to a lightning protection circuit for serial communication, which can be applied to the field of lightning protection for vehicle-mounted and airborne exposed equipment. Background Technology

[0002] Meteorological disasters account for over 50% of all aircraft accidents, with lightning disasters making up about 60% of these meteorological disasters, and this percentage has been increasing in recent years. Therefore, lightning protection has become a primary consideration in the design of interfaces for civil aircraft flight control electronic equipment. Traditional flight control electronic equipment installed in the cabin only needs to meet A3 level lightning protection requirements. However, advanced civil aircraft flight control electronic products, due to their distributed architecture design, have electronic equipment that is constantly exposed to the outside of the aircraft, requiring B5 level lightning protection. The open-circuit voltage of B5 level tests is 10 times that of A3 level, and the short-circuit current exceeds A3 level by 25 times. Furthermore, the miniaturization of electronic equipment further complicates lightning protection design.

[0003] Currently, lightning protection technologies for serial communication are mostly multi-level protection, which uses a combination of gas discharge tubes, high-voltage resistors, transient suppression diodes, etc., in series to achieve the B5 level test for airborne equipment. This design method has several drawbacks. Firstly, the combination of multiple protection devices, many of which are low-reliability devices with a high failure rate, greatly reduces the safety level of the protection circuit. Secondly, the multi-level protection design method cannot achieve miniaturization and occupies a lot of space in electronic devices.

[0004] High-level miniaturized lightning protection circuits have become an urgent problem to be solved in advanced civil aircraft flight control electronic products. Utility Model Content

[0005] Purpose of the utility model: To propose a lightning protection circuit for serial communication, solving the technical challenge of high-level miniaturization.

[0006] Technical solution:

[0007] A lightning protection circuit for serial communication includes a communication transformer circuit, two clamping protection circuits, two steady-state matching circuits, and a transceiver drive circuit, wherein:

[0008] The primary side of the communication transformer circuit serves as the pin interface for external communication, used for normal differential signal transmission and reception. The two ends of the secondary side of the communication transformer circuit are respectively connected to the clamped points of two clamping protection circuits.

[0009] The clamped points of the two clamping protection circuits are respectively connected to the input terminals of the corresponding steady-state matching circuits;

[0010] The outputs of the two steady-state matching circuits are respectively connected to the two inputs of the driver transceiver;

[0011] The output of the driver transceiver is connected to the serial transceiver module of the MCU processor to achieve normal communication.

[0012] Preferably, the communication transformer circuit includes a transformer T1, a resistor R1, and a capacitor C1. The primary side of the communication transformer T1 is connected in parallel with the resistor R1. The primary side of the communication transformer T1 serves as the pin interface for external communication, used for normal differential signal transmission and reception. The two ends of the secondary side of the communication transformer circuit T1 are respectively connected to the clamped points of two clamping protection circuits. One end of the capacitor C1 is connected to the center of the secondary side of the communication transformer T1, and the other end of the capacitor C1 is grounded.

[0013] Preferably, the first clamping protection circuit includes: a first diode VD1 and a second diode VD2, wherein the anode of the first diode VD1 is connected to -15V, the cathode of the first diode VD1 is connected to the anode of the second diode VD2 as the clamping point, and the cathode of the second diode VD2 is connected to +15V.

[0014] The second clamping protection circuit includes a third diode VD3 and a fourth diode VD4. The positive terminal of the third diode VD3 is connected to -15V, and the negative terminal of the third diode VD3 is connected to the positive terminal of the fourth diode VD4 as the clamping point. The negative terminal of the fourth diode VD4 is connected to +15V.

[0015] Preferably, the first steady-state matching circuit includes a resistor R2 and a capacitor C2, wherein one end of the resistor R2 is connected to the clamped point of the first clamping protection circuit, the other end of the resistor R2 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded.

[0016] The second steady-state matching circuit includes a resistor R3 and a capacitor C3. One end of the resistor R3 is connected to the clamped point of the second clamping protection circuit, and the other end of the resistor R3 is connected to one end of the capacitor C3. The other end of the capacitor C3 is grounded.

[0017] Preferably, the driver transceiver is a driver chip D1, and the differential input level of the driver chip D1 is within the range of ±15V.

[0018] Preferably, the PCB trace width between the communication transformer and the input connector is greater than 50 mil.

[0019] Beneficial effects:

[0020] This application utilizes a combination of discrete components such as communication transformers, resistors, and capacitors to implement lightning protection technology for serial communication pins. It is primarily used in advanced civil aircraft flight control electronic equipment, achieving high-level, miniaturized lightning protection. The lightning protection level reaches the highest pin injection level, B5, and the size is one-fifth that of a conventional transient voltage suppressor diode. Furthermore, this design offers additional advantages:

[0021] 1. Electrical isolation: Provides electrical isolation between the transmitting and receiving ends, reducing interference between different circuits and enhancing the stability and reliability of the system;

[0022] 2. Impedance matching: Ensure that the impedance of the signal matches that of the transmission line during signal transmission to reduce signal reflection and distortion, thereby optimizing signal transmission quality;

[0023] 3. Signal enhancement: The signal is amplified and shaped to a certain extent so that it can maintain good quality after long-distance transmission. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a lightning protection circuit for serial communication according to an embodiment of the present invention. Detailed Implementation

[0025] like Figure 1 A high-level miniaturized lightning protection interface circuit for serial communication is disclosed, comprising: a communication transformer circuit 1, a clamping protection circuit 2, a steady-state matching circuit 3, and a driver transceiver 4. The primary side of the communication transformer circuit 1 serves as the external pin, and the clamping protection circuit 2 is connected to both ends of the secondary side of the communication transformer 1. The signal after passing through the clamping circuit passes through the steady-state matching circuit 3, and the output of the steady-state matching circuit 3 is connected to the driver transceiver 4. This circuit achieves high-level miniaturized lightning protection by adding a lightning protection interface circuit design, while also optimizing the transmitted signal and providing a certain degree of signal enhancement, ensuring good signal quality during long-distance transmission.

[0026] The lightning protection circuit for serial communication described in this application features high protection level, small size, and high reliability.

[0027] like Figure 1 As shown, a high-level miniaturized lightning protection interface circuit for serial communication includes a communication transformer circuit 1, a clamping protection circuit 2, a steady-state matching circuit 3, and a driver transceiver 4. The primary side of the communication transformer circuit 1 serves as the external pin, and the two ends of the secondary side of the communication transformer 1 are connected to the clamping protection circuit 2. The signal after passing through the clamping circuit passes through the steady-state matching circuit 3, and the output of the steady-state matching circuit 3 is connected to the driver transceiver 4 to realize the function of the lightning protection circuit.

[0028] For the high-level miniaturized lightning protection interface circuit of serial communication, the communication transformer 1 can withstand overvoltage. At the same time, the communication transformer circuit has inductive load characteristics. During the high-level lightning test, the transient impulse voltage and current are in the microsecond range. The communication transformer can effectively withstand overvoltage, and the short-circuit current is suppressed by the transformer on the primary side.

[0029] For the high-level miniaturized lightning protection interface circuit of serial communication, the clamping protection circuit 2 is mainly used to restrict the current generated by the stray capacitance of the secondary winding of the communication transformer 1, effectively protecting the subsequent circuits. The anode of the fast recovery diode VD1 of the clamping protection circuit is connected to a -15V level, and the cathode of VD1 is connected to the transformer circuit 1.

[0030] For high-level miniaturized lightning protection interface circuits for serial communication, the steady-state matching circuit 3 mainly includes resistors and capacitors, which can realize the functions of signal matching and stabilization.

[0031] The design of lightning protection circuits must consider both the rationality of the design and the adherence to design principles during layout and wiring. The main design steps are as follows to ensure the protection capability of the interface circuits:

[0032] Step 1: Lightning transient signals are characterized by high voltage, high current, and high rate of change. Therefore, in the PCB design of the protection circuit, it is necessary to avoid the influence of lead inductance on the TVS suppression effect.

[0033] Step 2: During the layout design process, make the communication transformer circuit 1 as close as possible to the interface, and the distance between the communication transformer circuit 1 and the interface should be less than 3 cm.

[0034] Step 3: Based on the test results, ensure that the PCB trace width between the communication transformer and the input connector is greater than 50mil if possible.

Claims

1. A lightning protection circuit for serial communication, characterized in that, It includes a communication transformer circuit, two clamping protection circuits, two steady-state matching circuits, and a transceiver drive circuit, wherein: The primary side of the communication transformer circuit serves as the pin interface for external communication, used for normal differential signal transmission and reception. The two ends of the secondary side of the communication transformer circuit are respectively connected to the clamped points of two clamping protection circuits. The clamped points of the two clamping protection circuits are respectively connected to the input terminals of the corresponding steady-state matching circuits; The outputs of the two steady-state matching circuits are respectively connected to the two inputs of the driver transceiver; The output of the driver transceiver is connected to the serial transceiver module of the MCU processor to achieve normal communication.

2. The circuit according to claim 1, characterized in that, The communication transformer circuit includes a transformer T1, a resistor R1, and a capacitor C1. The primary side of the communication transformer T1 is connected in parallel with the resistor R1. The primary side of the communication transformer T1 serves as the pin interface for external communication, used for normal differential signal transmission and reception. The two ends of the secondary side of the communication transformer T1 are connected to the clamped points of two clamping protection circuits, respectively. One end of the capacitor C1 is connected to the center of the secondary side of the communication transformer T1, and the other end of the capacitor C1 is grounded.

3. The circuit according to claim 2, characterized in that, The first clamping protection circuit includes: a first diode VD1 and a second diode VD2, wherein the positive terminal of the first diode VD1 is connected to -15V, the negative terminal of the first diode VD1 is connected to the positive terminal of the second diode VD2 as the clamping point, and the negative terminal of the second diode VD2 is connected to +15V. The second clamping protection circuit includes a third diode VD3 and a fourth diode VD4. The positive terminal of the third diode VD3 is connected to -15V, and the negative terminal of the third diode VD3 is connected to the positive terminal of the fourth diode VD4 as the clamping point. The negative terminal of the fourth diode VD4 is connected to +15V.

4. The circuit according to claim 3, characterized in that, The first steady-state matching circuit includes: resistor R2 and capacitor C2, wherein one end of resistor R2 is connected to the clamped point of the first clamping protection circuit, the other end of resistor R2 is connected to one end of capacitor C2, and the other end of capacitor C2 is grounded. The second steady-state matching circuit includes a resistor R3 and a capacitor C3. One end of the resistor R3 is connected to the clamped point of the second clamping protection circuit, and the other end of the resistor R3 is connected to one end of the capacitor C3. The other end of the capacitor C3 is grounded.

5. The circuit according to claim 1, characterized in that, The drive transceiver circuit is a drive chip D1, and the differential input level of the drive chip D1 is within the range of ±15V.

6. The circuit according to claim 1, characterized in that, The PCB trace width between the communication transformer circuit and the input connector is greater than 50 mil.

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