Protection circuit of RS232 interface chip

Abstract

The utility model relates to the technical field of communication testing, in particular to a protection circuit of an RS232 interface chip. The protection circuit comprises a small PCB (printed circuit board); the two standard RS232 interfaces are respectively a J1 interface for a female head and a J2 interface for a male head; a current-limiting resistor R1 and a current-limiting resistor R2; a filtering magnetic bead FB1 and a filtering magnetic bead FB2; a bidirectional transient suppression diode TVS1 and a bidirectional transient suppression diode TVS2; and a filter capacitor C1 and a filter capacitor C2. According to the protection circuit of the RS232 interface chip, when two devices need to be connected with interface debugging signals, glitch voltage and impact current can be effectively absorbed and filtered out through combination of electronic components of the protection circuit, impact of overcurrent and overvoltage problems on the chip can be reduced to a certain extent when the interface is plugged and unplugged, and the reliability of the chip is improved. The purpose of protecting the interface chip is achieved.

Description

Technical Field

[0001] This utility model relates to the field of communication testing technology, specifically a protection circuit for an RS232 interface chip. Background Technology

[0002] RS232 interfaces are widely used as debugging interfaces in communication equipment and other electronic products, especially PC hosts, for inter-board communication and monitoring signal interfaces, with a transmission distance not exceeding 15 meters. When we want to conduct communication debugging between two devices through the RS232 interface on a device, we generally use an RS232 serial cable with one male and one female end. Pins 2 and 3 of the interface are the receive signal pin (RX) and transmit signal pin (TX), respectively, and these two pins are directly connected to the RS232 interface chip. The remaining pins 1-9 are not directly connected to the RS232 interface chip. For ease of use, frequent hot-plugging, especially multiple plugging and unplugging in a short period of time, is more likely to generate spike voltages and inrush currents. Therefore, the interface will be subjected to overvoltage and overcurrent surges. Without protection, these overvoltage and overcurrent problems can easily be conducted directly to the interface chip through the receive and transmit signal lines, and prolonged overload will damage it. Utility Model Content

[0003] This utility model addresses the technical problems existing in the prior art by providing a protection circuit for an RS232 interface chip to solve the technical problem that overvoltage and overcurrent during equipment communication debugging can easily damage the interface chip.

[0004] The technical solution of this utility model to solve the above-mentioned technical problems is as follows:

[0005] A protection circuit for an RS232 interface chip is provided, the protection circuit comprising:

[0006] A small PCB board;

[0007] Two standard RS232 interfaces, namely J1 for the female connector and J2 for the male connector;

[0008] Current-limiting resistors R1 and R2;

[0009] Filter beads FB1 and FB2;

[0010] Bidirectional transient voltage suppressor diode TVS1 and bidirectional transient voltage suppressor diode TVS2;

[0011] Filter capacitor C1 and filter capacitor C2;

[0012] The protection circuit is used to absorb and filter out the spike voltage and inrush current generated when plugging and unplugging the interface, so as to reduce the impact of overvoltage and overcurrent on the RS232 interface chip on the main device.

[0013] Furthermore, pin 1 of the J1 interface is connected to pin 1 of the J2 interface via a signal line; pin 4 of the J1 interface is connected to pin 4 of the J2 interface via a signal line; pin 6 of the J1 interface is connected to pin 6 of the J2 interface via a signal line; pin 7 of the J1 interface is connected to pin 7 of the J2 interface via a signal line; pin 8 of the J1 interface is connected to pin 8 of the J2 interface via a signal line; and pin 9 of the J1 interface is connected to pin 9 of the J2 interface via a signal line.

[0014] Furthermore, pin 2 of the J1 interface is connected to pin 2 of the J2 interface via the series connection of the current-limiting resistor R1 and the filter bead FB1; pin 3 of the J1 interface is connected to pin 3 of the J2 interface via the series connection of the current-limiting resistor R2 and the filter bead FB2.

[0015] Furthermore, one end of the bidirectional transient suppression diode TVS1 is connected to the signal line between the filter bead FB1 and pin 2 of the J2 interface, and the other end is grounded; one end of the bidirectional transient suppression diode TVS2 is connected to the signal line between the filter bead FB2 and pin 3 of the J2 interface, and the other end is grounded.

[0016] Furthermore, one end of the filter capacitor C1 is connected to the signal line between the filter bead FB1 and pin 2 of the J2 interface, and the other end is grounded; one end of the filter capacitor C2 is connected to the signal line between the filter bead FB2 and pin 3 of the J2 interface, and the other end is grounded.

[0017] Furthermore, pin 5 of the J1 interface and pin 5 of the J2 interface are directly grounded.

[0018] Furthermore, both the current-limiting resistors R1 and R2 are 100 ohms; both the filter beads FB1 and FB2 are 100 ohms; the bidirectional transient voltage suppressor diodes TVS1 and TVS2 are BS0150MS with a reverse breakdown voltage of 6V; and the filter capacitors C1 and C2 are 330pF.

[0019] The beneficial effects of this utility model are:

[0020] This invention designs a protection circuit for an RS232 interface chip. When two devices need to connect to the interface for signal debugging, the combination of electronic components in the protection circuit can effectively absorb and filter out some spike voltages and inrush currents. It can also reduce the impact of overcurrent and overvoltage on the chip to a certain extent when plugging and unplugging the interface, thus achieving the purpose of protecting the interface chip. It is applicable to any use of the RS232 interface. This invention has a simple circuit, fewer components, can be reused, and is inexpensive and cost-effective. Attached Figure Description

[0021] Figure 1 This is the circuit diagram of this utility model;

[0022] In the attached image:

[0023] A. Master device; B. PCB board; C. Slave device. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this utility model and are not intended to limit this utility model.

[0025] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0026] The following disclosure provides numerous different embodiments or examples for implementing various structures of the present invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention; however, those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0027] The present invention provides the following preferred embodiments:

[0028] To address the impact of overvoltage and overcurrent generated during RS232 interface insertion and removal on the RS232 interface chip on the host device, this embodiment further optimizes the protection circuit design. Specifically, this embodiment provides a protection circuit for the RS232 interface chip, which includes a small PCB board B, two standard RS232 interfaces, namely RS232 interface (male) J2 and RS232 interface (female) J1, current-limiting resistors R1 and R2, filter beads FB1 and FB2, bidirectional transient suppression diodes TVS1 and TVS2, and filter capacitors C1 and C2.

[0029] Furthermore, PCB board B has two standard RS2329 pin interfaces, with J2 being a male and J1 a female. Pin 1 of J1 is connected to pin 1 of J2 via a signal line; pin 4 of J1 is connected to pin 4 of J2 via a signal line; pin 6 of J1 is connected to pin 6 of J2 via a signal line; pin 7 of J1 is connected to pin 7 of J2 via a signal line; pin 8 of J1 is connected to pin 8 of J2 via a signal line; and pin 9 of J1 is connected to pin 9 of J2 via a signal line. This connection method ensures that all pins except pins 2 and 3 are directly interconnected, thus guaranteeing the integrity of data transmission.

[0030] Furthermore, pin 2 of the J1 interface is connected to pin 2 of the J2 interface via a series connection of current-limiting resistor R1 and filter bead FB1; pin 3 of the J1 interface is connected to pin 3 of the J2 interface via a series connection of current-limiting resistor R2 and filter bead FB2. This connection method effectively reduces the peak value of the inrush current and filters high-frequency interference through the filter beads FB1 and FB2. It is important to understand that the current-limiting resistors R1 and R2 limit the current magnitude to prevent excessive current from directly impacting the RS232 interface chip. The filter beads FB1 and FB2 are used to filter high-frequency noise, ensuring signal purity. The characteristic curves of the filter beads show that for the RS232 communication frequency, these beads can pass through with low impedance, while high-frequency noise is blocked. Combined with low-value capacitors C1 and C2, high-frequency interference can be effectively discharged.

[0031] Furthermore, one end of the bidirectional transient voltage suppressor diode TVS1 is connected to the signal line between pin 2 of the filter bead FB1 and the J2 interface, and the other end is grounded; one end of the bidirectional transient voltage suppressor diode TVS2 is connected to the signal line between pin 3 of the filter bead FB2 and the J2 interface, and the other end is grounded. The main function of the bidirectional transient voltage suppressor diodes TVS1 and TVS2 is to quickly conduct under overvoltage conditions, directly conducting the overvoltage to ground, thereby protecting the RS232 interface chip from damage. It is understandable that the selection of bidirectional transient voltage suppressor diodes needs to consider their reverse breakdown voltage. In this embodiment, TVS1 and TVS2 are of model BS0150MS, with a reverse breakdown voltage of 6V, slightly higher than the output level ±5.5V of the RS232 interface chip. This allows for rapid conduction under overvoltage conditions, preventing chip damage.

[0032] Furthermore, one end of filter capacitor C1 is connected to the signal line between pin 2 of the filter bead FB1 and the J2 interface, and the other end is grounded; one end of filter capacitor C2 is connected to the signal line between pin 3 of the filter bead FB2 and the J2 interface, and the other end is grounded. The function of filter capacitors C1 and C2 is to further filter out high-frequency interference in the signal and ensure signal purity. In this embodiment, the capacitance of filter capacitors C1 and C2 is 330pF, which is a suitable value that can effectively filter out high-frequency interference without affecting signal transmission.

[0033] Furthermore, pins 5 of the J1 and J2 interfaces are directly grounded. This grounding method ensures signal stability and reduces the impact of static electricity during insertion and removal. It's important to understand that grounding is a common anti-static measure; by directly grounding pin 5 of the interface, static electricity buildup can be effectively prevented, thus protecting the RS232 interface chip.

[0034] Furthermore, the current-limiting resistors R1 and R2 are both 100 ohms; the filter beads FB1 and FB2 are both 100 ohms; the bidirectional transient suppression diodes TVS1 and TVS2 are BS0150MS with a reverse breakdown voltage of 6V; and the filter capacitors C1 and C2 are 330pF. The selection of these components is based on a comprehensive consideration of their performance and cost. The 100-ohm resistance of the current-limiting resistors R1 and R2 effectively limits the peak value of the inrush current without significantly affecting signal transmission. The 100-ohm resistance of the filter beads FB1 and FB2 effectively filters out high-frequency noise, ensuring signal purity. The BS0150MS bidirectional transient suppression diodes TVS1 and TVS2 have a suitable reverse breakdown voltage, allowing them to quickly conduct under overvoltage conditions, protecting the RS232 interface chip. The 330pF capacitance of the filter capacitors C1 and C2 effectively filters out high-frequency interference, ensuring signal purity.

[0035] Furthermore, to improve the reliability and stability of the protection circuit, this embodiment can also add an indicator light to the PCB board B to display the circuit's operating status. The indicator light illuminates when the circuit is working normally; it turns off when a fault or overvoltage occurs. This allows users to easily identify and address problems promptly. The indicator light can be a small LED, installed at a key location on the PCB board B. Through the indicator light, users can intuitively understand the circuit's operating status and take appropriate measures in a timely manner.

[0036] Furthermore, to further enhance the flexibility and adaptability of the protection circuit, this embodiment can also add a programmable logic controller (PLC) to the PCB board B. The PLC enables dynamic control of the circuit, allowing the operating mode to be adjusted according to actual needs. For example, when an overvoltage is detected, the PLC can automatically switch to protection mode, cutting off the power supply and protecting the RS232 interface chip; when a normal operating state is detected, the PLC can automatically switch to normal mode, restoring the circuit to normal operation. This significantly improves the reliability and adaptability of the circuit. The PLC can be a small microcontroller installed in a critical location on the PCB board B. Through the PLC, the operating mode of the circuit can be dynamically adjusted according to actual requirements, thereby improving the circuit's flexibility and adaptability.

[0037] Furthermore, device C is connected to port J2 on the circuit board via an RS232 serial cable, while port J1 on the circuit board is directly connected to the RS232 port of the master device A. This connection method enables communication between the master device A and the slave device C, and by protecting the circuit board, it prevents overvoltage and overcurrent from impacting the RS232 chip on the master device during interface plugging and unplugging, thus extending the lifespan of the product interface. It is important to understand that this connection method not only ensures the reliability of data transmission but also effectively extends the lifespan of the RS232 interface chip.

[0038] This embodiment demonstrates that the protection circuit effectively absorbs and filters out spike voltages and inrush currents during interface plugging and unplugging, thereby reducing the impact of overvoltage and overcurrent on the RS232 interface chip on the main device. Furthermore, the addition of indicator lights and a PLC further enhances the circuit's reliability and adaptability. The advantage of this embodiment is that it not only solves the problems existing in the prior art but also provides a simple, low-cost, and efficient solution suitable for various RS232 interface application scenarios.

[0039] Implementation Principle: When a small board is added for communication between the master and slave devices, the RX signal (pin 2) and TX signal (pin 3) pass through the board. The ferrite bead and capacitor on the board filter out high-frequency interference. According to the characteristic curve of the ferrite bead, the communication frequency of the RS-232 is relatively low compared to the bead, allowing it to pass through with low impedance. High-frequency noise is blocked, and the low-capacitance capacitor further discharges high-frequency interference. The series current-limiting resistor reduces the peak value of the inrush current, providing protection. Since most RS-232 chips have an output level of ±5.5V, a bidirectional diode is used, and its withstand voltage is slightly higher than the output level. Excessive overvoltage will cause breakdown, preventing chip damage and reducing risk. The remaining pins (excluding pins 2 and 3) are directly interconnected since they are not directly connected to the RS-232 chip.

[0040] Implementation steps:

[0041] 1. Connect the J1 RS232 female connector of the small board (B) to the male connector of the main device (A).

[0042] 2. Connect the device (C) to the J2 RS232 male port of the small board (B) via an RS232 serial cable.

[0043] 3. Device (A) and device (C) can connect and communicate to read the information the user wants.

[0044] 4. When a user wants to switch devices for communication, they can directly unplug the J1 port and insert the master device to be replaced, or unplug the J2 port and insert the slave device to be replaced.

[0045] 5. Voltage spikes, inrush currents, or static electricity generated during hot-plugging will first pass through the filtering and current / voltage limiting of the small board before entering the TX and RX signals of the RS232 chip, and will not damage the chip.

[0046] The beneficial effects of this utility model are specifically reflected in the fact that the above are only preferred embodiments of this utility model and are not intended to limit this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A protection circuit for RS232 interface chip, characterized in that, The protection circuit includes: A small PCB board; Two standard RS232 interfaces, namely J1 for the female connector and J2 for the male connector; Current-limiting resistors R1 and R2; Filter beads FB1 and FB2; Bidirectional transient voltage suppressor diode TVS1 and bidirectional transient voltage suppressor diode TVS2; Filter capacitor C1 and filter capacitor C2; The protection circuit is used to absorb and filter out the spike voltage and inrush current generated when plugging and unplugging the interface, so as to reduce the impact of overvoltage and overcurrent on the RS232 interface chip on the main device.

2. The protection circuit for RS232 interface chip according to claim 1, characterized in that, Pin 1 of the J1 interface is connected to pin 1 of the J2 interface via a signal line; pin 4 of the J1 interface is connected to pin 4 of the J2 interface via a signal line; pin 6 of the J1 interface is connected to pin 6 of the J2 interface via a signal line; pin 7 of the J1 interface is connected to pin 7 of the J2 interface via a signal line; pin 8 of the J1 interface is connected to pin 8 of the J2 interface via a signal line; and pin 9 of the J1 interface is connected to pin 9 of the J2 interface via a signal line.

3. The protection circuit for RS232 interface chip according to claim 1, wherein, Pin 2 of the J1 interface is connected to pin 2 of the J2 interface via the current-limiting resistor R1 and the filter bead FB1 connected in series; pin 3 of the J1 interface is connected to pin 3 of the J2 interface via the current-limiting resistor R2 and the filter bead FB2 connected in series.

4. The protection circuit for RS232 interface chip according to claim 1, characterized in that, One end of the bidirectional transient suppression diode TVS1 is connected to the signal line between the filter bead FB1 and pin 2 of the J2 interface, and the other end is grounded; one end of the bidirectional transient suppression diode TVS2 is connected to the signal line between the filter bead FB2 and pin 3 of the J2 interface, and the other end is grounded.

5. The protection circuit for RS232 interface chip according to claim 1, wherein, One end of the filter capacitor C1 is connected to the signal line between the filter bead FB1 and pin 2 of the J2 interface, and the other end is grounded; one end of the filter capacitor C2 is connected to the signal line between the filter bead FB2 and pin 3 of the J2 interface, and the other end is grounded.

6. The protection circuit for RS232 interface chip according to claim 1, wherein, Pin 5 of the J1 interface and pin 5 of the J2 interface are directly grounded.

7. The protection circuit for RS232 interface chip according to any one of claims 1-6, characterized in that, The current-limiting resistors R1 and R2 are both 100 ohms; the filter beads FB1 and FB2 are both 100 ohms; the bidirectional transient suppression diodes TVS1 and TVS2 are BS0150MS with a reverse breakdown voltage of 6V; and the filter capacitors C1 and C2 are 330pF.

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