Short circuit protection circuit for Type-C interface

Abstract

The utility model provides a short-circuit protection circuit for a Type-C interface, and belongs to the technical field of short-circuit protection circuits. Comprising an interface module, an overvoltage and electromagnetic protection circuit and a switching circuit, the interface module, the overvoltage and electromagnetic protection circuit and the switching circuit are connected in series on the same power line and grounding line, and a common circuit and a standby circuit are arranged in the switching circuit and are both connected with the power line. According to the utility model, through the cooperation of the resettable fuse, the double-pole double-throw relay and other elements, the circuit can be rapidly switched so as to ensure that the interface can continue to work normally without maintenance when a short-circuit fault occurs, and through the synergistic effect of the gas discharge tube, the first transient suppression diode, the second transient suppression diode, the electrolytic capacitor and other elements, the short-circuit fault of the interface can be effectively prevented. The problems of overvoltage and electromagnetic interference during short circuit can be effectively relieved.

Description

Technical Field

[0001] This utility model relates to the field of short-circuit protection circuit technology, and in particular to a short-circuit protection circuit for a Type-C interface. Background Technology

[0002] With the continuous development and popularization of electronic devices, the Type-C interface has been widely used in various electronic devices due to its many advantages such as high-speed data transmission and fast charging. From smartphones and tablets to laptops, the Type-C interface is gradually becoming the mainstream connection interface standard. It not only brings users a convenient connection method and an efficient data transmission experience, but also promotes the technological progress of the electronic device industry.

[0003] However, in actual use, short-circuit faults are a common and significant problem. For example, in complex environments such as factory workshops and construction sites, Type-C interfaces may short-circuit due to cables being squeezed or worn by heavy objects or accidentally coming into contact with metal debris. Furthermore, frequent plugging and unplugging of Type-C cables during daily use can loosen the pins inside the interface, increasing the risk of short circuits. Currently available short-circuit protection circuits often require repair before continued use can resume, severely impacting normal equipment operation and wasting time and money. Additionally, some protection circuits lack reliability and may fail after repeated short circuits, failing to provide continuous and effective protection for the equipment. Utility Model Content

[0004] This utility model aims to at least partially solve one of the problems existing in the prior art. To this end, it provides a short-circuit protection circuit for Type-C interfaces, which solves the technical problems that existing Type-C interface short-circuit protection circuits require maintenance before continued use when a short circuit occurs, and that overvoltage and electromagnetic interference are prone to occur inside the circuit when a short circuit occurs, affecting the normal operation of the equipment.

[0005] Technical Solution: To achieve the above objectives, this utility model provides the following technical solution: A short-circuit protection circuit for a Type-C interface, comprising: an interface module, an overvoltage and electromagnetic protection circuit, and a switching circuit. The interface module, overvoltage and electromagnetic protection circuit, and switching circuit are connected in series on the same power supply line and grounding line. The switching circuit includes a normal operating circuit and a backup circuit, both of which are connected to the power supply line. A double-pole double-throw relay is installed within the switching circuit, and its two output pins are connected in series with the normal operating circuit and the backup circuit, respectively. The double-pole double-throw relay is used for communication between the normal operating circuit and the backup circuit. The switching circuit includes two resettable fuses, both integrated within the switching circuit. These fuses are connected in series with the two input pins of the double-pole double-throw relay. The resettable fuses limit current increase during overcurrent events. Connections between modules should utilize high-quality wires and reliable connection methods to ensure signal transmission stability and low impedance. For example, 0.5 mm tinned copper wire can be used as the connecting wire, and the connection method should be soldering. Solder joints should be full and firm, avoiding cold solder joints. Furthermore, the layout requirements of each module on the circuit board should be clearly defined to reduce electromagnetic interference and signal crosstalk.

[0006] In another embodiment, two current sensing resistors are provided, and the two current sensing resistors are connected in series in the main circuit and the backup circuit, respectively. The current sensing resistors are used to detect the magnitude of the current in the main circuit and the backup circuit. Two comparators are provided, and the two comparators are connected in series in the main circuit and the backup circuit, respectively. The input terminals of the comparators are connected in parallel across the current sensing resistors. The comparators are used to compare the detected current with a preset value and output a corresponding signal. Two light-emitting diodes are provided, and the two light-emitting diodes are connected in series in the main circuit and the backup circuit, respectively. The light-emitting diodes are connected in series with the output terminals of the comparators. The light-emitting diodes are used to output a corresponding signal from the comparators. The LED illuminates to indicate the circuit status. The current sensing resistor can be a surface-mount resistor with an accuracy of ±1% and a resistance of 0.1 ohms. The comparator's response time should be less than 1 microsecond; for example, an LM393 comparator can be used. The brightness of the LED can be selected to be above 5000 mcd, and the color can be red or green to indicate fault and normal states, respectively. When the current in the circuit exceeds 1 ampere, the comparator outputs a high level, causing the red LED to light up, indicating that the circuit is in an overcurrent state. When the current is less than or equal to 1 ampere, the comparator outputs a low level, causing the green LED to light up, indicating that the circuit is working normally.

[0007] In a further embodiment, a Type-C module is provided, with multiple GND pins connected in parallel and connected to a ground line, and multiple VBUS pins connected in parallel and connected to a power line. Multiple first transient suppression diodes are provided, and these diodes are respectively connected to pins CC1, CC2, DP1, DP2, DN1, and DN2 on the Type-C module. The first transient suppression diodes are connected in parallel with the GND pins. These first transient suppression diodes are used to reverse break down when a transient high voltage occurs on a relevant pin of the Type-C interface, clamping the voltage to a safe value. The parameters of the first transient suppression diodes should be reasonably selected based on the operating voltage of the Type-C interface and the possible transient voltages. For example, assuming the operating voltage of the Type-C interface is 5 volts and the transient voltage may be as high as 20 volts, a transient suppression diode with a withstand voltage of 24 volts and a response time of 1 nanosecond can be selected.

[0008] In a further embodiment, a second transient suppression diode is connected in parallel between the power supply line and the ground line. This diode is used to rapidly reverse break down when a transient high voltage occurs in the power supply line, clamping the voltage to a safe value. A ceramic capacitor is connected in parallel between the power supply line and the ground line, used to filter out high-frequency noise in the power supply line. A gas discharge tube is connected in parallel between the power supply line and the ground line, used to rapidly conduct when an overvoltage occurs, guiding the excessive voltage to ground. An electrolytic capacitor is connected in parallel between the power supply line and the ground line, used to store and release charge, smoothing the power supply voltage to reduce ripple and noise in the power supply. The second transient suppression diode... The transient suppression diode can be selected with a withstand voltage of 30 volts and a response time of 0.5 nanoseconds; the ceramic capacitor can be selected with a capacitance of 0.1 microfarads and a withstand voltage of 50 volts; the gas discharge tube can be set to a conduction voltage of 250 volts; the electrolytic capacitor can be selected with a capacitance of 100 microfarads and a withstand voltage of 16 volts; when the voltage on the power line instantaneously rises to above 25 volts, the second transient suppression diode quickly reverse-biases and breaks down, clamping the voltage below 20 volts; when high-frequency noise appears on the power line, the ceramic capacitor can reduce the noise amplitude to below 10% of the original value; when the voltage on the power line exceeds 250 volts, the gas discharge tube quickly conducts, guiding the excessive voltage to ground; the electrolytic capacitor can reduce the power supply ripple to below 50mV.

[0009] In a further embodiment, under normal circumstances, the commonly used circuits are always connected to the interface module.

[0010] In a further embodiment, the first transient suppression diode is directly connected to the corresponding pin of the Type-C module, and the parallel line with the GND pin is short. The connection method should employ reliable soldering or plug-in techniques to ensure a secure connection. For example, the diameter of the solder joint should be no less than 0.5 mm. Simultaneously, the impact of the circuit layout on electromagnetic compatibility should be considered; the line length between the first transient suppression diode and the Type-C module pin should be controlled within 5 mm.

[0011] In a further embodiment, the second transient suppression diode, ceramic capacitor, gas discharge tube, and electrolytic capacitor in the overvoltage and electromagnetic protection circuit are connected in parallel and arranged close to the interface module and switching circuit. The layout should take heat dissipation into account to avoid overheating of the components. For example, heat sinks can be placed around the components, and the area of ​​the heat sinks should not be less than 1 square centimeter. At the same time, the distance between the components should be appropriate to prevent mutual interference. The distance between the components should be maintained at more than 2 millimeters. The components should be installed as close as possible to the interface module and switching circuit, and the distance from the interface module and switching circuit should not exceed 5 millimeters.

[0012] Beneficial effects: 1. Through the cooperation of components such as self-resetting fuses and double-pole double-throw relays, when a short circuit occurs at the Type-C interface, the self-resetting fuse will heat up rapidly, and the resistance will increase sharply, limiting the current from further increasing and preventing equipment damage; at the same time, the double-pole double-throw relay can quickly switch the circuit, ensuring that the interface can continue to work normally without maintenance when a short circuit fault occurs; improving the availability and reliability of the equipment, avoiding the time and economic costs caused by maintenance, reducing equipment downtime, and enabling users to use the equipment more smoothly.

[0013] 2. By utilizing the synergistic effect of components such as the gas discharge tube, the first transient suppression diode, the second transient suppression diode, and the electrolytic capacitor, when an overvoltage occurs, the gas discharge tube quickly conducts, guiding the excessive voltage to ground, providing the first line of defense for other components in the circuit; the first and second transient suppression diodes quickly reverse-break down when a transient high voltage occurs, clamping the voltage to a safe value and preventing high voltage from damaging circuit components; while the electrolytic capacitor can store and release charge, smoothing the power supply voltage, reducing ripple and noise in the power supply, and improving the system's stability and anti-interference capability; through the cooperation of these components, the overvoltage and electromagnetic interference problems during short circuits are effectively mitigated, ensuring that the equipment can operate normally in complex electromagnetic environments. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the overall circuit of this utility model.

[0016] Figure 2 This is a schematic diagram of the interface module.

[0017] Figure 3 This is a schematic diagram of an overvoltage and electromagnetic protection circuit.

[0018] Figure 4 This is a schematic diagram of the switching circuit.

[0019] The reference numerals in the figure are as follows: 1. Interface module; 101. Type-C module; 102. First transient suppression diode; 2. Overvoltage and electromagnetic protection circuit; 201. Second transient suppression diode; 202. Ceramic capacitor; 203. Gas discharge tube; 204. Electrolytic capacitor; 3. Switching circuit; 301. Self-resetting fuse; 302. Double-pole double-throw relay; 303. Current sensing resistor; 304. Comparator; 305. Light-emitting diode. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions in this utility model are described clearly and completely. Obviously, the described embodiments are only some, not all, of the embodiments in this utility model. All other embodiments obtained by those skilled in the art based on the embodiments in this utility model without creative effort are within the scope of protection of this utility model.

[0021] This application provides a short-circuit protection circuit for Type-C interfaces, solving the technical problems of existing Type-C interface short-circuit protection circuits requiring repair before continued use after a short circuit, and the potential for overvoltage and electromagnetic interference within the circuit during a short circuit, affecting normal equipment operation. In practical use, it solves the problem of existing circuits requiring repair before continued use after a short circuit, and mitigates overvoltage and electromagnetic interference during short circuits.

[0022] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0023] Reference Figure 1-4A short-circuit protection circuit for a Type-C interface includes: an interface module 1, an overvoltage and electromagnetic protection circuit, and a switching circuit 3. The interface module 1, the overvoltage and electromagnetic protection circuit, and the switching circuit 3 are connected in series on the same power supply line and ground line. The switching circuit 3 includes a normal operating circuit and a backup circuit, both of which are connected to the power supply line. A double-pole double-throw relay 302 is disposed within the switching circuit 3, and its two output pins are connected in series with the normal operating circuit and the backup circuit, respectively. The double-pole double-throw relay 302 is used for switching between the normal operating circuit and the backup circuit. Two resettable fuses 301 are provided, and both resettable fuses 301 are disposed within the switching circuit 3. The two resettable fuses 301 are connected in series with the two input pins of the double-pole double-throw relay 302, respectively. The resettable fuses 301 are used to limit the increase of current when the circuit is overcurrent.

[0024] The switching circuit 3 is equipped with a main circuit and a backup circuit to provide redundancy protection for the circuit. When the main circuit fails, the double-pole double-throw relay 302 can realize the rapid switching between the main circuit and the backup circuit, reduce equipment downtime, and ensure continuous operation of the equipment. At the same time, the self-resetting fuse 301 limits the increase of current when the circuit is overcurrent, protecting the circuit components from overcurrent damage.

[0025] Two current sensing resistors 303 are provided, and the two current sensing resistors 303 are connected in series in the normal circuit and the backup circuit, respectively. The current sensing resistors 303 are used to detect the current in the normal circuit and the backup circuit. Two comparators 304 are provided, and the two comparators 304 are connected in series in the normal circuit and the backup circuit, respectively. The input terminals of the comparators 304 are connected in parallel across the current sensing resistors 303. The comparators 304 are used to compare the detected current with a preset value and output a corresponding signal. Two light-emitting diodes 305 are provided, and the two light-emitting diodes 305 are connected in series in the normal circuit and the backup circuit, respectively. The light-emitting diodes 305 are connected in series with the output terminals of the comparators 304. The light-emitting diodes 305 are used to light up when the comparators 304 output a corresponding signal, thereby indicating the circuit status.

[0026] Two comparators 304 are connected in series in the main circuit and the backup circuit, respectively. Their inputs are connected in parallel across the current sensing resistor 303, enabling them to compare the detected current with a preset value and output a corresponding signal. In addition, two LEDs 305 are connected in series in the main circuit and the backup circuit, respectively, and are also connected in series with the outputs of the comparators 304. When the comparators 304 output a corresponding signal, the LEDs 305 illuminate, indicating the circuit status.

[0027] Type-C module 101, wherein multiple GND pins on Type-C module 101 are connected in parallel and connected to the ground line, and multiple VBUS pins on Type-C module 101 are connected in parallel and connected to the power line; multiple first transient suppression diodes 102 are provided, and the multiple first transient suppression diodes 102 are respectively connected to the CC1, CC2, DP1, DP2, DN1, and DN2 pins on Type-C module 101, and the first transient suppression diodes 102 are connected in parallel with the GND pins. The first transient suppression diodes 102 are used to reverse break down when a transient high voltage occurs on the relevant pins of the Type-C interface, clamping the voltage to a safe value.

[0028] The Type-C module 101 in interface module 1 improves grounding reliability and power stability by connecting multiple GND pins in parallel to the ground line and multiple VBUS pins in parallel to the power line. At the same time, the first transient suppression diode 102 reverse breaks down when a transient high voltage occurs on the relevant pins of the Type-C interface, clamping the voltage to a safe value and protecting the internal circuit components of the module.

[0029] A second transient voltage suppressor diode 201, connected in parallel between the power supply line and the ground line, is used to quickly reverse break down when a transient high voltage occurs in the power supply line, clamping the voltage to a safe value; a ceramic capacitor 202, also connected in parallel between the power supply line and the ground line, is used to filter out high-frequency noise in the power supply line; a gas discharge tube 203, connected in parallel between the power supply line and the ground line, is used to quickly conduct when an overvoltage occurs, guiding the excessively high voltage to ground; and an electrolytic capacitor 204, connected in parallel between the power supply line and the ground line, is used to store and release charge, smoothing the power supply voltage to reduce ripple and noise in the power supply.

[0030] The second transient suppression diode 201 in the overvoltage electromagnetic protection circuit 2 quickly reverse-breaks down to protect subsequent circuit components when a transient high voltage occurs in the power line. The ceramic capacitor 202 filters out high-frequency noise in the power line to improve the circuit's anti-interference capability. The gas discharge tube 203 quickly conducts to guide the excessive voltage to ground when an overvoltage occurs. The electrolytic capacitor 204 stores and releases charge to smooth the power supply voltage and reduce ripple and noise, thus jointly ensuring the stable operation of the circuit under different environments.

[0031] Under normal circumstances, the commonly used circuit is always connected to the interface module 1.

[0032] Under normal circumstances, the commonly used circuit is always connected to the interface module 1 to ensure the stable operation of the equipment under normal conditions, reduce the number of switching circuit 3 operations, and improve the overall stability and reliability of the circuit.

[0033] The first transient suppression diode 102 is directly connected to the corresponding pin of the Type-C module 101, and the parallel line with the GND pin is relatively short.

[0034] The first transient suppression diode 102 is directly connected to the corresponding pin of the Type-C module 101 and has a short parallel line with the GND pin, which enables it to respond quickly when a transient high voltage occurs, thus better protecting the circuit components.

[0035] The second transient suppression diode 201, ceramic capacitor 202, gas discharge tube 203 and electrolytic capacitor 204 in the overvoltage and electromagnetic protection circuit are connected in parallel and arranged close to the interface module 1 and the switching circuit 3.

[0036] The second transient suppression diode 201, ceramic capacitor 202, gas discharge tube 203 and electrolytic capacitor 204 in the overvoltage electromagnetic protection circuit 2 are connected in parallel and arranged close to the interface module 1 and the switching circuit 3, so as to better play the protective role and reduce the impact of electromagnetic interference and overvoltage on the critical circuit parts.

[0037] During use, the Type-C module 101 in interface module 1 is connected to the ground line via multiple GND pins in parallel and to the power line via multiple VBUS pins in parallel, improving grounding reliability and power stability. Simultaneously, the first transient suppression diode 102 is connected to the CC1, CC2, DP1, DP2, DN1, and DN2 pins of the Type-C module 101 and is connected in parallel with the GND pins. When a transient high voltage occurs on the relevant pins of the Type-C interface, it quickly reverse-breaks down to clamp the voltage to a safe value, protecting the internal circuit components of the module. The second transient suppression diode 201 in the overvoltage electromagnetic protection circuit 2 quickly reverse-breaks down when a transient high voltage occurs on the power line, protecting subsequent circuit components. The ceramic capacitor 202 filters out high-frequency noise in the power line, improving the circuit's anti-interference capability. The gas discharge tube 203 quickly conducts when overvoltage occurs, guiding the excessive voltage to ground. The electrolytic capacitor 204 stores and releases charge, smoothing the power supply voltage and reducing ripple and noise, collectively ensuring stable operation of the circuit under different environments. Furthermore, these components are connected in parallel and arranged close to the interface module 1 and the switching circuit 3 to better perform their protective function and reduce the impact of electromagnetic interference and overvoltage on critical circuit parts. The switching circuit 3 is equipped with a normal operating circuit and a backup circuit to provide redundancy protection for the circuit. When the equipment is running normally, the normal operating circuit is always connected to the interface module 1 to ensure stable operation of the equipment and reduce the number of times the switching circuit 3 operates. The double-pole double-throw relay 302 is used to realize rapid switching between the normal operating circuit and the backup circuit when needed. For example, when the normal operating circuit fails, the relay acts quickly to reduce equipment downtime and ensure continuous operation of the equipment. At the same time, the self-resetting fuse 301 limits the increase of current when the circuit is overcurrent, protecting circuit components from overcurrent damage. The current sensing resistor 303 in the switching circuit 3 monitors the current in the normal operating circuit and the backup circuit in real time. The comparator 304 compares the detected current with the preset value to determine the circuit status. The light-emitting diode 305 illuminates according to the output signal of the comparator 304 to indicate the circuit status, allowing users to intuitively understand the working status of the circuit.

[0038] The figures shown in the accompanying drawings are illustrative and are intended only to more intuitively demonstrate the key structure and connection relationships of a short-circuit protection circuit for a Type-C interface according to this invention. In practical applications, adjustments and optimizations can be made according to specific needs. Furthermore, the data provided in the specification are illustrative and do not fully represent the specific values ​​in actual applications. In actual production and use, these data can be adjusted and optimized according to different Type-C interface specifications, usage environments, and specific performance requirements.

[0039] This utility model encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this utility model. To provide the public with a thorough understanding of this utility model, specific details have been described in detail in the above preferred embodiments; however, those skilled in the art can fully understand this utility model even without these detailed descriptions. Furthermore, to avoid unnecessary confusion regarding the essence of this utility model, well-known methods, processes, procedures, components, and circuits have not been described in detail.

[0040] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A short-circuit protection circuit for a Type-C interface, comprising an interface module (1), an overvoltage and electromagnetic protection circuit, and a switching circuit (3), characterized in that: The interface module (1), overvoltage and electromagnetic protection circuit and switching circuit (3) are connected in series on the same power line and grounding line. The switching circuit (3) is provided with a common circuit and a backup circuit. Both the common circuit and the backup circuit are connected to the power line. A double-pole double-throw relay (302) is set in the switching circuit (3), and the two output pins of the double-pole double-throw relay (302) are connected in series with the normal circuit and the backup circuit respectively. The double-pole double-throw relay (302) is used for switching between the normal circuit and the backup circuit. There are two resettable fuses (301), and both resettable fuses (301) are set in the switching circuit (3). The two resettable fuses (301) are connected in series on the two input pins of the double-pole double-throw relay (302). The resettable fuses (301) are used to limit the increase of current when the circuit is overcurrent.

2. A short-circuit protection circuit for a Type-C interface according to claim 1, characterized in that, The switching circuit (3) includes: Two current sensing resistors (303) are provided, and the two current sensing resistors (303) are connected in series in the main circuit and the backup circuit respectively. The current sensing resistors (303) are used to detect the current in the main circuit and the backup circuit. Two comparators (304) are provided, and the two comparators (304) are connected in series in the common circuit and the backup circuit respectively. The input terminal of the comparator (304) is connected in parallel across the current sensing resistor (303). The comparator (304) is used to compare the detected current with a preset value and output a corresponding signal. Two light-emitting diodes (305) are provided, and the two light-emitting diodes (305) are connected in series in the normal circuit and the backup circuit respectively. The light-emitting diodes (305) are connected in series with the output terminal of the comparator (304). The light-emitting diodes (305) are used to emit light when the comparator (304) outputs a corresponding signal, so as to indicate the circuit status.

3. A short-circuit protection circuit for a Type-C interface according to claim 1, characterized in that, Interface module (1) includes: A Type-C module (101) wherein multiple GND pins on the Type-C module (101) are connected in parallel and connected to a ground line, and multiple VBUS pins on the Type-C module (101) are connected in parallel and connected to a power line; Multiple first transient suppression diodes (102) are provided, and the multiple first transient suppression diodes (102) are respectively connected to the CC1, CC2, DP1, DP2, DN1, and DN2 pins on the Type-C module (101). The first transient suppression diodes (102) are connected in parallel with the GND pin. The first transient suppression diodes (102) are used to reverse break down when a transient high voltage occurs on the relevant pins of the Type-C interface, clamping the voltage to a safe value.

4. A short-circuit protection circuit for a Type-C interface according to claim 1, characterized in that, Overvoltage and electromagnetic protection circuits include: The second transient suppression diode (201) is connected in parallel between the power supply line and the ground line. The second transient suppression diode (201) is used to quickly reverse break down when a transient high voltage occurs in the power supply line, clamping the voltage to a safe value. A ceramic capacitor (202) is connected in parallel between the power supply line and the ground line. The ceramic capacitor (202) is used to filter out high-frequency noise in the power supply line. A gas discharge tube (203) is connected in parallel between the power supply line and the grounding line. The gas discharge tube (203) is used to quickly conduct when an overvoltage occurs, guiding the excessive voltage to the ground. An electrolytic capacitor (204) is connected in parallel between the power supply line and the ground line. The electrolytic capacitor (204) is used to store and release charge, smooth the power supply voltage, and reduce ripple and noise in the power supply.

5. A short-circuit protection circuit for a Type-C interface according to claim 1, characterized in that: Under normal circumstances, the commonly used circuit is always connected to the interface module (1).

6. A short-circuit protection circuit for a Type-C interface according to claim 3, characterized in that: The first transient suppression diode (102) is directly connected to the corresponding pin of the Type-C module (101), and the parallel line with the GND pin is relatively short.

7. A short-circuit protection circuit for a Type-C interface according to claim 4, characterized in that: The second transient suppression diode (201), ceramic capacitor (202), gas discharge tube (203) and electrolytic capacitor (204) in the overvoltage and electromagnetic protection circuit are connected in parallel and arranged close to the interface module (1) and the switching circuit (3).

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