485 communication interface circuit and protection device thereof

Abstract

The invention discloses a protection device of a 485 communication interface circuit, the 485 communication interface circuit and a voltage detection method of the 485 communication interface circuit, and the device comprises an over-current and over-voltage protection unit which enables the over-current and over-voltage protection unit to be disconnected under the condition that an abnormal signal occurs in the 485 communication interface circuit, so as to enable the 485 communication interface circuit to be disconnected; after the abnormal signal disappears, the overcurrent and overvoltage protection unit is recovered to be switched on, so that the 485 communication interface circuit is recovered to be switched on; the surge lightning stroke protection unit is used for discharging surge current generated by lightning stroke into the ground when the 485 communication interface circuit encounters lightning stroke; and the first filtering unit is used for filtering interference signals in the 485 communication interface circuit. According to the scheme, the over-current and over-voltage protection unit, the surge and lightning protection unit and the first filtering unit are arranged, so that the operation condition in a severe and complex environment is improved, the safety is ensured, and effective communication is realized.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and particularly relates to a protection device for a 485 communication interface circuit, a 485 communication interface circuit, and more particularly to a filtering protection circuit for a 485 communication interface circuit and a 485 communication interface circuit having the filtering protection circuit. Background Art

[0002] With the wide application of 485 communication technology, 485 communication interface circuits can be seen in many fields. However, in some relatively harsh and complex environmental conditions, a simple 485 communication interface circuit is difficult to withstand the harsh and complex environmental conditions and may be damaged.

[0003] The above content is only used to assist in understanding the technical solution of the present invention, and does not represent an admission that the above content is prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a protection device for a 485 communication interface circuit, a 485 communication interface circuit, and a voltage detection method thereof, so as to solve the problem that a 485 communication interface circuit is difficult to withstand harsh and complex environmental conditions and may be damaged, and achieve the effect of improving the normal and stable operation of the 485 communication interface circuit in harsh and complex environments, ensuring the safety of the 485 communication interface circuit board and operators, and realizing effective communication by setting an overcurrent and overvoltage protection circuit, a surge and lightning protection circuit, and a filtering circuit between the host computer and the RS485 communication chip.

[0005] The present invention provides a protection device for a 485 communication interface circuit. The 485 communication interface circuit has an RS485 communication chip. The protection device for the 485 communication interface circuit includes: an overcurrent and overvoltage protection unit, a surge and lightning protection unit, and a first filtering unit. The overcurrent and overvoltage protection unit, the surge and lightning protection unit, and the first filtering unit are all arranged between the host computer of the 485 communication interface circuit and the RS485 communication chip. Among them, the overcurrent and overvoltage protection unit is used to disconnect itself when an abnormal signal appears in the 485 communication interface circuit, so as to disconnect the 485 communication interface circuit; and restore itself to be connected after the abnormal signal disappears, so as to restore the 485 communication interface circuit to be connected. Among them, the abnormal signal includes: a signal when the 485 communication interface circuit has a short circuit, or a signal when the 485 communication interface circuit has a voltage input exceeding a preset voltage threshold. The surge and lightning protection unit is used to discharge the surge current generated by lightning into the ground when the 485 communication interface circuit encounters lightning. The first filtering unit is used to filter out interference signals in the 485 communication interface circuit.

[0006] In some embodiments, the overcurrent and overvoltage protection unit includes: a first self - resetting fuse module and a second self - resetting fuse module; wherein, a first connection end of the host computer is connected to a first connection end of the first self - resetting fuse module; a second connection end of the first self - resetting fuse module serves as a first output end of the overcurrent and overvoltage protection unit and is connected to the surge and lightning protection unit; a second connection end of the host computer is connected to a first connection end of the second self - resetting fuse module; a second connection end of the second self - resetting fuse module serves as a second output end of the overcurrent and overvoltage protection unit and is connected to the surge and lightning protection unit.

[0007] In some embodiments, the surge and lightning protection unit includes: a first clamping diode module, a second clamping diode module, and a third clamping diode module; wherein, a first output end of the overcurrent and overvoltage protection unit is connected to a first connection end of the second clamping diode module; a first connection end of the second clamping diode module serves as a first output end of the surge and lightning protection unit and is grounded via the first clamping diode module; a second output end of the overcurrent and overvoltage protection unit is connected to a second connection end of the second clamping diode module; a second connection end of the second clamping diode module serves as a second output end of the surge and lightning protection unit and is grounded via the third clamping diode module.

[0008] In some embodiments, the first filtering unit includes: a common - mode inductor module; the common - mode inductor module has a first winding and a second winding; the RS485 communication chip has an A pin and a B pin; wherein, a first output end of the surge and lightning protection unit is connected to a first connection end of the first winding; a second connection end of the first winding serves as a first output end of the first filtering unit and can be connected to the B pin of the RS485 chip; a second output end of the surge and lightning protection unit is connected to a first connection end of the second winding; a second connection end of the second winding serves as a first output end of the first filtering unit and can be connected to the A pin of the RS485 chip.

[0009] In some embodiments, it further includes: a second filtering unit; wherein, a preset DC power supply is grounded via the second filtering unit; a common terminal of the preset DC power supply and the second filtering unit is connected to a power supply terminal of the RS485 communication chip.

[0010] In some embodiments, the second filtering unit includes: a filtering capacitor module.

[0011] In some embodiments, it further includes: a pull-up resistor unit; wherein, a preset DC power supply is connected to the A pin of the RS485 communication chip after passing through the pull-up resistor unit.

[0012] In some embodiments, it further includes: a current limiting unit; wherein, the current limiting unit is arranged between the first filtering unit and the RS485 communication chip, and is used for limiting the current in the RS485 communication interface circuit to achieve overcurrent protection for the RS485 communication interface circuit.

[0013] In some embodiments, the current limiting unit includes: a first current limiting resistor module and a second current limiting resistor module; wherein, the first current limiting resistor module is arranged between the first output end of the first filtering unit and the B pin of the RS485 communication chip; the second current limiting resistor module is arranged between the second output end of the first filtering unit and the A pin of the RS485 communication chip; wherein, when the first filtering unit includes a common mode inductance module, the first current limiting resistor module is arranged between the second connection end of the first winding of the common mode inductance module and the B pin of the RS485 communication chip; the second current limiting resistor module is arranged between the second connection end of the second winding of the common mode inductance module and the A pin of the RS485 communication chip.

[0014] Matched with the above device, on the other hand, the present invention provides a 485 communication interface circuit, including: the protection device of the above-mentioned 485 communication interface circuit.

[0015] Thus, the solution of the present invention, by setting an overcurrent and overvoltage protection circuit, a surge and lightning protection circuit, and a filtering circuit between the host computer and the RS485 communication chip for the 485 communication interface circuit, the overcurrent and overvoltage protection circuit is used to fuse and disconnect when the 485 communication interface circuit is short-circuited or high voltage is input and self-recover after the abnormal signal disappears to make the circuit return to normal, the surge and lightning protection circuit is used to discharge the surge current into the ground during lightning strikes, and the filtering circuit is used to effectively filter out external interference and self-generated interference; thereby, by setting an overcurrent and overvoltage protection circuit, a surge and lightning protection circuit, and a filtering circuit between the host computer and the RS485 communication chip, the normal and stable operation of the 485 communication interface circuit in a harsh and complex environment is improved, the safety of the 485 communication interface circuit board and the operator is ensured, and effective communication is achieved.

[0016] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention.

[0017] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0018] Figure 1 FIG. 1 is a schematic structural diagram of an embodiment of a protection device for a 485 communication interface circuit of the present invention;

[0019] Figure 2 FIG. 2 is a schematic structural diagram of a filter protection circuit for a 485 communication interface circuit of the present invention;

[0020] Figure 3 FIG. 3 is a schematic diagram of a voltage waveform when a clamping diode is subjected to an ESD impact of +8 kV;

[0021] Figure 4 FIG. 4 is a schematic diagram of a voltage waveform when a clamping diode is subjected to a surge impact with a peak current of 62 A. Detailed Embodiment

[0022] In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Considering some relatively harsh and complex environmental conditions, such as: environmental conditions with interference from other power lines and communication lines around, environmental conditions with an excessive length of the communication line, etc., it is very easy to have clutter interference. Under some relatively harsh and complex environmental conditions, the 485 communication interface circuit is very difficult to withstand the harsh and complex environmental conditions and is damaged. For example: if the 485 communication interface circuit is misconnected to a high-voltage DC power supply, the 485 communication interface circuit will be damaged without a protection device. Another example: in an area with a complex environment, the communication line may be twisted with the power line, and for long-distance communication, a large amount of clutter interference will be generated, and normal communication will not be possible without a filtering device.

[0024] Therefore, the solution of the present invention proposes a protection device for a 485 communication interface circuit, specifically a filter protection circuit for a 485 communication interface circuit, which is provided with an overcurrent and overvoltage protection circuit, a filtering circuit, and a surge and lightning protection circuit, significantly improving the normal and stable operation of the 485 communication interface circuit under harsh and complex environments, ensuring the safety of the 485 communication interface circuit board and operators, and achieving effective communication.

[0025] According to an embodiment of the present invention, a protection device for a 485 communication interface circuit is provided. Refer to Figure 1Schematic structural diagram of an embodiment of the device of the present invention. The 485 communication interface circuit has an RS485 communication chip; in the solution of the present invention, as Figure 1 shown, the protection device of the 485 communication interface circuit includes: an overcurrent and overvoltage protection unit (such as an overcurrent and overvoltage protection circuit), a surge and lightning protection unit (such as a surge and lightning protection circuit), and a first filtering unit (such as a filtering circuit); the overcurrent and overvoltage protection unit, the surge and lightning protection unit, and the first filtering unit are all arranged between the host computer of the 485 communication interface circuit and the RS485 communication chip; preferably, the overcurrent and overvoltage protection unit, the surge and lightning protection unit, and the first filtering unit are arranged in sequence between the host computer of the 485 communication interface circuit and the RS485 communication chip.

[0026] Among them, the overcurrent and overvoltage protection unit is used to disconnect itself when an abnormal signal appears in the 485 communication interface circuit, so as to disconnect the 485 communication interface circuit to realize the protection of the 485 communication interface circuit; and after the abnormal signal disappears, the overcurrent and overvoltage protection unit restores itself to be connected, so that the 485 communication interface circuit is restored to be connected, and the 485 communication interface circuit resumes normal operation after the abnormal signal disappears; among them, the abnormal signal includes: the signal when the 485 communication interface circuit is short-circuited, or the signal with a voltage input exceeding the preset voltage threshold in the 485 communication interface circuit.

[0027] The surge and lightning protection unit is used to discharge the surge current generated by lightning into the ground when the 485 communication interface circuit encounters lightning, so as to realize the protection of the 485 communication interface circuit.

[0028] The first filtering unit is used to filter out the interference signals in the 485 communication interface circuit, so as to realize the protection of the 485 communication interface circuit.

[0029] Figure 2 Schematic structural diagram of the filtering and protection circuit of the 485 communication interface circuit of the present invention. As Figure 2 shown, the 485 communication interface circuit has an RS485 communication chip, and the filtering and protection circuit of the 485 communication interface circuit is arranged between the RS485 communication chip and the host computer, and the host computer is such as a DSP main control unit, an MCU main control unit, etc. The filtering and protection circuit of the 485 communication interface circuit includes: an overcurrent and overvoltage protection circuit, a filtering circuit, and a surge and lightning protection circuit. Among them, the overcurrent and overvoltage protection circuit, the surge and lightning protection circuit, and the filtering circuit are arranged in sequence between the host computer and the RS485 communication chip.

[0030] A filtering and protection circuit for a 485 communication interface circuit proposed by the solution of the present invention is provided with an over-current and over-voltage protection circuit, a filtering circuit, and a surge and lightning protection circuit. The over-current and over-voltage protection circuit will fuse and disconnect when the 485 communication interface circuit is short-circuited or high voltage is input, and will self-recover after the abnormal signal disappears, enabling the circuit to return to normal. The filtering circuit can effectively filter out external interference and interference generated by itself to ensure stable communication under harsh working conditions. The surge and lightning protection circuit discharges the surge current into the ground during lightning strikes. It has been verified that it can significantly improve the normal and stable operation of the 485 communication interface circuit in a harsh and complex environment, ensure the safety of the 485 communication interface circuit board and operators, and achieve effective communication.

[0031] In some embodiments, the over-current and over-voltage protection unit includes: a first self-recovery fuse module (such as a self-recovery mini fuse F1), and a second self-recovery fuse module (such as a self-recovery mini fuse F2).

[0032] Wherein, the first connection end of the host computer is connected to the first connection end of the first self-recovery fuse module; the second connection end of the first self-recovery fuse module serves as the first output end of the over-current and over-voltage protection unit and is connected to the surge and lightning protection unit.

[0033] The second connection end of the host computer is connected to the first connection end of the second self-recovery fuse module; the second connection end of the second self-recovery fuse module serves as the second output end of the over-current and over-voltage protection unit and is connected to the surge and lightning protection unit.

[0034] In Figure 2 In the filtering and protection circuit of the 485 communication interface circuit as shown, the over-current and over-voltage protection circuit includes: a self-recovery mini fuse F1 and a self-recovery mini fuse F2. The first connection end of the host computer is connected to the first connection end of the self-recovery mini fuse F1, and the second connection end of the self-recovery mini fuse F1 is connected to the corresponding connection end of the surge and lightning protection circuit. The second connection end of the host computer is connected to the first connection end of the self-recovery mini fuse F2, and the second connection end of the self-recovery mini fuse F2 is connected to the corresponding connection end of the surge and lightning protection circuit.

[0035] In the solution of the present invention, the over-current and over-voltage protection circuit is composed of a self-recovery mini fuse F1 and a self-recovery mini fuse F2. When the 485 communication interface circuit is short-circuited or high voltage is input, it will fuse and disconnect and self-recover after the abnormal signal disappears, enabling the circuit to return to normal.

[0036] Among them, the self - reset fuses F1 and F2 are composed of a polymer resin matrix and conductive particles incorporated therein. Under normal circumstances, they exhibit low impedance (only a few tenths to a few ohms). At this time, the heat generated by the current flowing through the circuit on them is very small and will not change the crystalline structure of the polymer resin, thus keeping the 485 communication interface circuit in a conductive state. When an over - current occurs in the 485 communication interface circuit, the heat generated by the large current flowing through the self - reset fuses F1 and F2 causes the temperature in the resin matrix to rise. When the temperature is higher than the switching temperature T of the self - reset fuses F1 and F2, the volume of the polymer resin matrix expands, and its impedance rapidly increases, thereby effectively reducing the current in the 485 communication interface circuit and playing a role in over - current protection for the 485 communication interface circuit. After troubleshooting, the resin cools and recrystallizes again, and the self - reset fuses F1 and F2 return to the low - impedance state. Due to this characteristic, the self - reset fuses F1 and F2 can be reused without replacement, greatly reducing the maintenance cost of the equipment.

[0037] In the solution of the present invention, the over - current and over - voltage protection circuit is composed of a self - reset mini - fuse F1 and a self - reset mini - fuse F2. Different protection devices are selected, which are easy to distinguish, and the protection characteristics of the protection devices are different. When the 485 communication interface circuit is short - circuited or a high - voltage is input, it will fuse and disconnect and self - recover after the abnormal signal disappears, making the circuit return to normal. Among them, the protection device refers to the component adopted in the solution of the present invention, which is a self - reset fuse, while a single resistor or non - self - reset component is generally used in general circuits; the protection characteristic of the protection device refers to that the component adopted in the solution of the present invention fuses when it works and can self - recover after fusing.

[0038] In some embodiments, the surge and lightning strike protection unit includes: a first clamping diode module (such as clamping diode D1), a second clamping diode module (such as clamping diode D2), and a third clamping diode module (such as clamping diode D3).

[0039] Among them, the first output terminal of the over - current and over - voltage protection unit is connected to the first connection terminal of the second clamping diode module; the first connection terminal of the second clamping diode module, as the first output terminal of the surge and lightning strike protection unit, is grounded through the first clamping diode module.

[0040] The second output terminal of the over - current and over - voltage protection unit is connected to the second connection terminal of the second clamping diode module; the second connection terminal of the second clamping diode module, as the second output terminal of the surge and lightning strike protection unit, is grounded through the third clamping diode module.

[0041] In such as Figure 2In the filtering and protection circuit of the 485 communication interface circuit shown, the surge and lightning protection circuit includes: clamping diode D1, clamping diode D2, and clamping diode D3. The first connection end of clamping diode D2 is grounded via clamping diode D1; the second connection end of clamping diode D2 is grounded via clamping diode D3.

[0042] The second connection end of the self - resetting miniature fuse F1 is connected to the first connection end of clamping diode D2. The second connection end of the self - resetting miniature fuse F2 is connected to the second connection end of clamping diode D2. The first connection end of clamping diode D2 is also connected to the corresponding connection end of the filtering circuit; the second connection end of clamping diode D2 is also connected to the corresponding connection end of the filtering circuit.

[0043] In the solution of the present invention, the surge and lightning protection circuit is composed of clamping diode D1, clamping diode D2, and clamping diode D3 with the function of absorbing large energy, and discharges the surge current into the ground during lightning strikes.

[0044] Among them, clamping diode D1, clamping diode D2, and clamping diode D3 have a large - area PN junction. Its reverse characteristic is a typical avalanche type, with a low dynamic impedance and a low clamping voltage during avalanche. When its two poles are subjected to a reverse transient surge voltage impact, it can change the high impedance between its two poles into a low impedance at the speed of picoseconds (i.e., ps), quickly absorb a surge power of up to several kilowatts, clamp the voltage between the two poles to a predetermined value, and effectively protect the electronic circuit components from various forms of surge pulses. Under the action of the transient peak surge current, the current flowing through clamping diode D1, clamping diode D2, and clamping diode D3 sharply rises from the original reverse leakage current IR to the breakdown voltage value VBR, and its reverse voltage VR rises to the breakdown voltage value VBR. Clamping diode D1, clamping diode D2, and clamping diode D3 are broken down. The minimum breakdown voltage BR is the starting voltage for it to become a low impedance, that is, the breakdown voltage for clamping diode D1, clamping diode D2, and clamping diode D3 to enter avalanche. With the appearance and increase of the peak pulse voltage, the flowing current reaches the maximum reverse peak pulse current IP, and its reverse voltage rises to the clamping voltage value VC and remains at this stable level. Subsequently, as the pulse current decays exponentially, the voltage between the two poles of clamping diode D1, clamping diode D2, and clamping diode D3 also continuously decreases and finally returns to the starting state. When the 485 communication interface circuit works in a lightning - prone environment, the surge voltage will be discharged through clamping diode D1, clamping diode D2, and clamping diode D3, protecting the components in the 485 communication interface circuit and ensuring that the 485 communication interface circuit can work normally under complex weather conditions.

[0045] In the solution of the present invention, the surge lightning protection circuit is composed of clamping diodes D1, D2 and D3 with the function of absorbing large energy. Selecting clamping diodes D1, D2 and D3 with the function of absorbing large energy can effectively prevent lightning strikes and discharge the surge current into the ground during lightning strikes.

[0046] In some embodiments, the first filtering unit includes: a common-mode inductance module, such as common-mode inductor L; the common-mode inductance module has a first winding and a second winding; the RS485 communication chip has a pin A and a pin B.

[0047] Wherein, the first output end of the surge lightning protection unit is connected to the first connection end of the first winding; the second connection end of the first winding serves as the first output end of the first filtering unit and can be connected to the pin B of the RS485 chip.

[0048] The second output end of the surge lightning protection unit is connected to the first connection end of the second winding; the second connection end of the second winding serves as the first output end of the first filtering unit and can be connected to the pin A of the RS485 chip.

[0049] In Figure 2 In the filtering and protection circuit of the 485 communication interface circuit as shown, the filtering circuit includes: a common-mode inductor L. The first connection end of the clamping diode D2 is connected to the first connection end of the first coil of the common-mode inductor L; the second connection end of the clamping diode D2 is connected to the first connection end of the second coil of the common-mode inductor L. The second connection end of the first coil of the common-mode inductor L can be connected to the pin B (i.e., the negative terminal pin of the differential signal) of the RS485 communication chip. The second connection end of the second coil of the common-mode inductor L can be connected to the pin A (i.e., the positive terminal pin of the differential signal) of the RS485 communication chip. The 485 interface circuit has two pins, namely pin A and pin B, and pin A and pin B work simultaneously to achieve the 485 communication function.

[0050] In the solution of the present invention, the filtering circuit is composed of a common-mode inductor L, which can effectively filter out external interference and self-generated interference, so as to ensure stable communication under harsh working conditions.

[0051] Among them, the common-mode inductor L is a common-mode interference suppression device with a ferrite core. It consists of two coils with the same size and the same number of turns, symmetrically wound on the same ferrite toroidal core to form a four-terminal device. It has an inhibitory effect on the common-mode signal by presenting a large inductance, while presenting a very small leakage inductance to the differential-mode signal and having almost no effect. The filtering principle of the common-mode inductor L is as follows: when the common-mode current flows through, the magnetic fluxes in the magnetic ring are superimposed on each other, thus having a relatively large inductance and playing an inhibitory role on the common-mode current; when the differential-mode current flows through the two coils, the magnetic fluxes in the magnetic ring cancel each other out, and there is almost no inductance, so the differential-mode current can pass through without attenuation. Therefore, the common-mode inductor L can effectively suppress the common-mode interference signal in the balanced line without affecting the differential-mode signal normally transmitted in the line (that is, it does not affect the passing of the differential signal of the 485 communication interface circuit).

[0052] In the solution of the present invention, the filtering circuit is composed of the common-mode inductor L. The selected common-mode inductor L has good filtering effect and stability, can effectively filter out external interference and self-generated interference, and ensure stable communication under harsh working conditions.

[0053] In some embodiments, the protection device of the 485 communication interface circuit further includes: a second filtering unit, such as a non-polarized filtering capacitor C1.

[0054] Among them, the preset DC power supply is grounded after passing through the second filtering unit; the common terminal of the preset DC power supply and the second filtering unit is connected to the power supply terminal of the RS485 communication chip.

[0055] In the solution of the present invention, the high-frequency interference of the power supply voltage provided by the preset DC power supply to the RS485 communication chip is filtered out through the second filtering unit, which can ensure that the RS485 communication chip obtains a stable power supply voltage.

[0056] In some embodiments, the second filtering unit includes: a filtering capacitor module, such as a non-polarized filtering capacitor C1.

[0057] In as Figure 2 In the filtering and protection circuit of the 485 communication interface circuit shown, the filtering and protection circuit of the 485 communication interface circuit further includes: a non-polarized filtering capacitor C1. The 5V DC power supply is grounded after passing through the non-polarized filtering capacitor C1. The common terminal of the 5V DC power supply and the non-polarized filtering capacitor C1 is connected to the VCC pin (i.e., the power supply pin) of the RS485 communication chip.

[0058] In the solution of the present invention, the non-polarized filtering capacitor C1 can filter out the high-frequency interference of the 5V power supply voltage provided by the 5V DC power supply and ensure that the RS485 communication chip obtains a stable power supply voltage.

[0059] In some embodiments, the protection device of the 485 communication interface circuit further includes: a pull-up resistor unit, such as pull-up resistor R1.

[0060] Wherein, a preset DC power supply is connected to the A pin of the RS485 communication chip after passing through the pull-up resistor unit.

[0061] In the Figure 2 In the filtering and protection circuit of the 485 communication interface circuit as shown, the filtering and protection circuit of the 485 communication interface circuit further includes: a pull-up resistor R1. The 5V DC power supply is connected to the A pin of the RS485 communication chip after passing through the pull-up resistor R1.

[0062] In the solution of the present invention, through the pull-up resistor R1, the level of the A pin of the RS485 communication chip is defaulted to the high level state, preventing the communication function from being accidentally triggered when communication is not required.

[0063] In some embodiments, the protection device of the 485 communication interface circuit further includes: a current limiting unit.

[0064] Wherein, the current limiting unit is arranged between the first filtering unit and the RS485 communication chip, and is used for limiting the current in the RS485 communication interface circuit to achieve overcurrent protection for the RS485 communication interface circuit.

[0065] In the solution of the present invention, through the current limiting unit, the current in the filtering and protection circuit of the 485 communication interface circuit is limited to prevent the components in the filtering and protection circuit of the 485 communication interface circuit from being damaged due to excessive current.

[0066] In some embodiments, the current limiting unit includes: a first current limiting resistor module (such as current limiting resistor R2), and a second current limiting resistor module (such as current limiting resistor R3). Wherein, the first current limiting resistor module is arranged between the first output end of the first filtering unit and the B pin of the RS485 communication chip; the second current limiting resistor module is arranged between the second output end of the first filtering unit and the A pin of the RS485 communication chip.

[0067] Wherein, in the case that the first filtering unit includes a common mode inductance module, the first current limiting resistor module is arranged between the second connection end of the first winding of the common mode inductance module and the B pin of the RS485 communication chip; the second current limiting resistor module is arranged between the second connection end of the second winding of the common mode inductance module and the A pin of the RS485 communication chip.

[0068] In the Figure 2In the filtering and protection circuit of the 485 communication interface circuit shown, the filtering and protection circuit of the 485 communication interface circuit further includes a current-limiting resistor R2 and a current-limiting resistor R3. The second connection end of the first coil of the common-mode inductor L is connected to the B pin of the RS485 communication chip after passing through the current-limiting resistor R2. The second connection end of the second coil of the common-mode inductor L is connected to the A pin of the RS485 communication chip after passing through the current-limiting resistor R3.

[0069] In the solution of the present invention, the current-limiting resistor R2 and the current-limiting resistor R3 are used to limit the current in the filtering and protection circuit of the 485 communication interface circuit, preventing excessive current from damaging the components in the filtering and protection circuit of the 485 communication interface circuit.

[0070] Figure 3 It is a schematic diagram of the voltage waveform when the clamping diode is subjected to an ESD impact of +8 kV. Figure 4 It is a schematic diagram of the voltage waveform when the clamping diode is subjected to a surge impact with a peak current of 62 A. Figure 3 In, the abscissa is the action time, and the ordinate is the voltage across its two ends. From Figure 3 and Figure 4 It can be seen that the clamping diode selected in the solution of the present invention has the ability to resist large-voltage and large-current surge impacts, ensuring that the 485 circuit is not damaged when subjected to large-voltage and large-current surge impacts. In the solution of the present invention, an over-current and over-voltage protection circuit is adopted to solve the problem of damage to the 485 communication interface circuit when a large current flows into or a large voltage is applied to the 485 communication interface circuit. Therefore, even if the operator misconnects the 485 communication interface circuit to a 24V power supply circuit, the 485 communication interface circuit will not be damaged and can still work normally after disconnecting the 24V power supply circuit. A filtering circuit is adopted to solve the problem of extremely large communication interference caused by external harsh environmental factors, so that even when the 485 communication cable is long and there are many communication branches, the 485 communication interface circuit can still maintain stable communication and will not be affected by external interference. A surge and lightning protection circuit is adopted to solve the problem of burning out of the 485 communication interface circuit during lightning surges, so that it can be ensured that the 485 communication interface circuit will not be broken down by strong surge voltage during lightning strikes and can still work normally.

[0071] Adopting the technical solution of the present invention, by setting an overcurrent and overvoltage protection circuit, a surge and lightning protection circuit, and a filtering circuit between the host computer and the RS485 communication chip for the 485 communication interface circuit, the overcurrent and overvoltage protection circuit is used to fuse and disconnect when the 485 communication interface circuit is short-circuited or has a high-voltage input and self-recover after the abnormal signal disappears to make the circuit return to normal. The surge and lightning protection circuit is used to discharge the surge current into the ground during lightning strikes, and the filtering circuit is used to effectively filter out external interference and interference generated by itself. Thus, by setting an overcurrent and overvoltage protection circuit, a surge and lightning protection circuit, and a filtering circuit between the host computer and the RS485 communication chip, the normal and stable operation of the 485 communication interface circuit in a harsh and complex environment is improved, the safety of the 485 communication interface circuit board and the operator is ensured, and effective communication is achieved.

[0072] According to an embodiment of the present invention, there is also provided a 485 communication interface circuit corresponding to the protection device of the 485 communication interface circuit. The 485 communication interface circuit may include: the protection device of the 485 communication interface circuit described above.

[0073] In the solution of the present invention, the protection device of the 485 communication interface circuit includes: an overcurrent and overvoltage protection unit (such as an overcurrent and overvoltage protection circuit), a surge and lightning protection unit (such as a surge and lightning protection circuit), and a first filtering unit (such as a filtering circuit); the overcurrent and overvoltage protection unit, the surge and lightning protection unit, and the first filtering unit are all arranged between the host computer of the 485 communication interface circuit and the RS485 communication chip; preferably, the overcurrent and overvoltage protection unit, the surge and lightning protection unit, and the first filtering unit are arranged in sequence between the host computer of the 485 communication interface circuit and the RS485 communication chip.

[0074] Among them, the overcurrent and overvoltage protection unit is used to disconnect itself when an abnormal signal appears in the 485 communication interface circuit, so that the 485 communication interface circuit is disconnected to realize the protection of the 485 communication interface circuit; and after the abnormal signal disappears, the overcurrent and overvoltage protection unit itself is restored to be connected, so that the 485 communication interface circuit is restored to be connected, and the 485 communication interface circuit resumes normal operation after the abnormal signal disappears; among them, the abnormal signal includes: the signal when the 485 communication interface circuit is short-circuited, or the signal when the 485 communication interface circuit has a voltage input exceeding a preset voltage threshold.

[0075] The surge and lightning protection unit is used to discharge the surge current generated by lightning into the ground when the 485 communication interface circuit encounters lightning strikes to realize the protection of the 485 communication interface circuit.

[0076] The first filtering unit is used to filter out the interference signals in the 485 communication interface circuit to protect the 485 communication interface circuit.

[0077] As Figure 2 shown, the 485 communication interface circuit has an RS485 communication chip. The filtering and protection circuit of the 485 communication interface circuit is arranged between the RS485 communication chip and the host computer, and the host computer is such as a DSP main control unit, an MCU main control unit, etc. The filtering and protection circuit of the 485 communication interface circuit includes: an overcurrent and overvoltage protection circuit, a filtering circuit, and a surge and lightning protection circuit. Among them, the overcurrent and overvoltage protection circuit, the surge and lightning protection circuit, and the filtering circuit are arranged in sequence between the host computer and the RS485 communication chip.

[0078] In the solution of the present invention, an overcurrent and overvoltage protection circuit, a filtering circuit, and a surge and lightning protection circuit are provided. The overcurrent and overvoltage protection circuit will fuse and disconnect when the 485 communication interface circuit is short-circuited or high voltage is input, and will self-recover after the abnormal signal disappears, so that the circuit returns to normal. The filtering circuit can effectively filter out external interference and self-generated interference to ensure stable communication under harsh working conditions. The surge and lightning protection circuit discharges the surge current into the ground during lightning strikes. It has been verified that it can significantly improve the normal and stable operation of the 485 communication interface circuit in a harsh and complex environment, ensure the safety of the 485 communication interface circuit board and operators, and achieve effective communication.

[0079] In some embodiments, the overcurrent and overvoltage protection unit includes: a first self-recovery fuse module (such as a self-recovery small fuse F1), a second self-recovery fuse module (such as a self-recovery small fuse F2). Among them, the first connection end of the host computer is connected to the first connection end of the first self-recovery fuse module; the second connection end of the first self-recovery fuse module serves as the first output end of the overcurrent and overvoltage protection unit and is connected to the surge and lightning protection unit. The second connection end of the host computer is connected to the first connection end of the second self-recovery fuse module; the second connection end of the second self-recovery fuse module serves as the second output end of the overcurrent and overvoltage protection unit and is connected to the surge and lightning protection unit.

[0080] In such as Figure 2In the filtering and protection circuit of the 485 communication interface circuit shown, the over-current and over-voltage protection circuit includes: a self-resetting miniature fuse F1 and a self-resetting miniature fuse F2. The first connection terminal of the host computer is connected to the first connection terminal of the self-resetting miniature fuse F1, and the second connection terminal of the self-resetting miniature fuse F1 is connected to the corresponding connection terminal of the surge and lightning protection circuit. The second connection terminal of the host computer is connected to the first connection terminal of the self-resetting miniature fuse F2, and the second connection terminal of the self-resetting miniature fuse F2 is connected to the corresponding connection terminal of the surge and lightning protection circuit.

[0081] In the solution of the present invention, the over-current and over-voltage protection circuit is composed of a self-resetting miniature fuse F1 and a self-resetting miniature fuse F2. When the 485 communication interface circuit is short-circuited or high voltage is input, it will fuse and disconnect and self-recover after the abnormal signal disappears, making the circuit return to normal.

[0082] In some embodiments, the surge and lightning protection unit includes: a first clamping diode module (such as clamping diode D1), a second clamping diode module (such as clamping diode D2), and a third clamping diode module (such as clamping diode D3).

[0083] Among them, the first output terminal of the over-current and over-voltage protection unit is connected to the first connection terminal of the second clamping diode module; the first connection terminal of the second clamping diode module, as the first output terminal of the surge and lightning protection unit, is grounded through the first clamping diode module. The second output terminal of the over-current and over-voltage protection unit is connected to the second connection terminal of the second clamping diode module; the second connection terminal of the second clamping diode module, as the second output terminal of the surge and lightning protection unit, is grounded through the third clamping diode module.

[0084] In Figure 2 In the filtering and protection circuit of the 485 communication interface circuit shown, the surge and lightning protection circuit includes: clamping diode D1, clamping diode D2, and clamping diode D3. The first connection terminal of clamping diode D2 is grounded through clamping diode D1; the second connection terminal of clamping diode D2 is grounded through clamping diode D3. The second connection terminal of self-resetting miniature fuse F1 is connected to the first connection terminal of clamping diode D2. The second connection terminal of self-resetting miniature fuse F2 is connected to the second connection terminal of clamping diode D2. The first connection terminal of clamping diode D2 is also connected to the corresponding connection terminal of the filtering circuit; the second connection terminal of clamping diode D2 is also connected to the corresponding connection terminal of the filtering circuit.

[0085] In the solution of the present invention, the surge and lightning protection circuit is composed of clamping diode D1, clamping diode D2, and clamping diode D3 with the function of absorbing large energy, and discharges the surge current into the ground during lightning strikes.

[0086] In some embodiments, the first filtering unit includes: a common-mode inductor module, such as common-mode inductor L; the common-mode inductor module has a first winding and a second winding; the RS485 communication chip has an A pin and a B pin.

[0087] Wherein, the first output terminal of the surge and lightning protection unit is connected to the first connection terminal of the first winding; the second connection terminal of the first winding serves as the first output terminal of the first filtering unit and can be connected to the B pin of the RS485 chip. The second output terminal of the surge and lightning protection unit is connected to the first connection terminal of the second winding; the second connection terminal of the second winding serves as the first output terminal of the first filtering unit and can be connected to the A pin of the RS485 chip.

[0088] In Figure 2 In the filtering and protection circuit of the 485 communication interface circuit as shown, the filtering circuit includes: a common-mode inductor L. The first connection terminal of the clamping diode D2 is connected to the first connection terminal of the first coil of the common-mode inductor L; the second connection terminal of the clamping diode D2 is connected to the first connection terminal of the second coil of the common-mode inductor L. The second connection terminal of the first coil of the common-mode inductor L can be connected to the B pin (i.e., the negative terminal pin of the differential signal) of the RS485 communication chip. The second connection terminal of the second coil of the common-mode inductor L can be connected to the A pin (i.e., the positive terminal pin of the differential signal) of the RS485 communication chip.

[0089] In the solution of the present invention, the filtering circuit is composed of a common-mode inductor L, which can effectively filter out external interference and self-generated interference, so as to ensure stable communication under harsh working conditions.

[0090] In some embodiments, the protection device of the 485 communication interface circuit further includes: a second filtering unit, such as a non-polar filtering capacitor C1. Wherein, a preset DC power supply is grounded after passing through the second filtering unit; the common terminal of the preset DC power supply and the second filtering unit is connected to the power supply terminal of the RS485 communication chip.

[0091] In the solution of the present invention, by filtering out the high-frequency interference of the power supply voltage provided by the preset DC power supply to the RS485 communication chip through the second filtering unit, it can ensure that the RS485 communication chip obtains a stable power supply voltage.

[0092] In some embodiments, the second filtering unit includes: a filtering capacitor module, such as a non-polar filtering capacitor C1. In Figure 2In the filtering and protection circuit of the 485 communication interface circuit shown, the filtering and protection circuit of the 485 communication interface circuit further includes: a non-polarized filtering capacitor C1. The 5V DC power supply is grounded after passing through the non-polarized filtering capacitor C1. The common terminal of the 5V DC power supply and the non-polarized filtering capacitor C1 is connected to the VCC pin (i.e., the power supply pin) of the RS485 communication chip.

[0093] In the solution of the present invention, the non-polarized filtering capacitor C1 can filter out the high-frequency interference of the 5V power supply voltage provided by the 5V DC power supply, ensuring that the RS485 communication chip obtains a stable power supply voltage.

[0094] In some embodiments, the protection device of the 485 communication interface circuit further includes: a pull-up resistor unit, such as a pull-up resistor R1. Among them, the preset DC power supply is connected to the A pin of the RS485 communication chip after passing through the pull-up resistor unit.

[0095] In Figure 2 In the filtering and protection circuit of the 485 communication interface circuit shown, the filtering and protection circuit of the 485 communication interface circuit further includes: a pull-up resistor R1. The 5V DC power supply is connected to the A pin of the RS485 communication chip after passing through the pull-up resistor R1.

[0096] In the solution of the present invention, through the pull-up resistor R1, the level of the A pin of the RS485 communication chip is defaulted to the high-level state.

[0097] In some embodiments, the protection device of the 485 communication interface circuit further includes: a current limiting unit. Among them, the current limiting unit is arranged between the first filtering unit and the RS485 communication chip, and is used for limiting the current in the 485 communication interface circuit to achieve over-current protection of the 485 communication interface circuit.

[0098] In the solution of the present invention, through the current limiting unit, the current in the filtering and protection circuit of the 485 communication interface circuit is limited to prevent the components in the filtering and protection circuit of the 485 communication interface circuit from being damaged due to excessive current.

[0099] In some embodiments, the current limiting unit includes: a first current limiting resistor module (such as a current limiting resistor R2) and a second current limiting resistor module (such as a current limiting resistor R3). Among them, the first current limiting resistor module is arranged between the first output terminal of the first filtering unit and the B pin of the RS485 communication chip; the second current limiting resistor module is arranged between the second output terminal of the first filtering unit and the A pin of the RS485 communication chip.

[0100] Wherein, when the first filtering unit includes a common-mode inductor module, the first current-limiting resistor module is disposed between the second connection end of the first winding of the common-mode inductor module and the B pin of the RS485 communication chip; the second current-limiting resistor module is disposed between the second connection end of the second winding of the common-mode inductor module and the A pin of the RS485 communication chip.

[0101] In the Figure 2 filter protection circuit of the 485 communication interface circuit as shown, the filter protection circuit of the 485 communication interface circuit further includes: a current-limiting resistor R2 and a current-limiting resistor R3. The second connection end of the first coil of the common-mode inductor L is connected to the B pin of the RS485 communication chip after passing through the current-limiting resistor R2. The second connection end of the second coil of the common-mode inductor L is connected to the A pin of the RS485 communication chip after passing through the current-limiting resistor R3.

[0102] In the solution of the present invention, the current in the filter protection circuit of the 485 communication interface circuit is limited by the current-limiting resistor R2 and the current-limiting resistor R3, so as to prevent the components in the filter protection circuit of the 485 communication interface circuit from being damaged due to excessive current.

[0103] Since the processing and functions implemented by the 485 communication interface circuit in this embodiment are basically corresponding to the embodiments, principles and examples of the device, for the details not described in the description of this embodiment, reference can be made to the relevant descriptions in the foregoing embodiments, and details will not be repeated here.

[0104] In summary, it is easy for those skilled in the art to understand that, on the premise of no conflict, the above-mentioned advantageous ways can be freely combined and superimposed.

[0105] The above are only the embodiments of the present invention, and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A protection device for a 485 communication interface circuit, characterized in that: The 485 communication interface circuit has an RS485 communication chip; The protection device of the 485 communication interface circuit includes: an overcurrent and overvoltage protection unit, a surge and lightning protection unit, and a first filtering unit; the overcurrent and overvoltage protection unit, the surge and lightning protection unit and the first filtering unit are all arranged between the host computer of the 485 communication interface circuit and the RS485 communication chip; wherein, The overcurrent and overvoltage protection unit is used to disconnect the overcurrent and overvoltage protection unit itself when an abnormal signal appears in the 485 communication interface circuit, so as to disconnect the 485 communication interface circuit; and restore the overcurrent and overvoltage protection unit itself after the abnormal signal disappears, so as to restore the 485 communication interface circuit; wherein the abnormal signal includes: a signal when a short circuit occurs in the 485 communication interface circuit, or a signal when a voltage input to the 485 communication interface circuit exceeds a preset voltage threshold; The surge lightning protection unit is used to discharge the surge current generated by lightning into the ground when the 485 communication interface circuit encounters lightning; The first filtering unit is used to filter out interference signals in the 485 communication interface circuit.

2. The protection device for the 485 communication interface circuit according to claim 1, characterized in that: The overcurrent and overvoltage protection unit comprises: a first self-recovery fuse module and a second self-recovery fuse module; wherein: The first connection end of the host computer is connected to the first connection end of the first self-resetting fuse module; the second connection end of the first self-resetting fuse module, as the first output end of the overcurrent and overvoltage protection unit, is connected to the surge and lightning protection unit; The second connection end of the host computer is connected to the first connection end of the second self-resetting fuse module; the second connection end of the second self-resetting fuse module, as the second output end of the overcurrent and overvoltage protection unit, is connected to the surge and lightning protection unit.

3. The protection device for the 485 communication interface circuit according to claim 1 or 2, characterized in that: The surge and lightning protection unit comprises: a first clamping diode module, a second clamping diode module, and a third clamping diode module; wherein, The first output end of the overcurrent and overvoltage protection unit is connected to the first connection end of the second clamping diode module; the first connection end of the second clamping diode module serves as the first output end of the surge and lightning protection unit and is grounded after passing through the first clamping diode module; The second output end of the overcurrent and overvoltage protection unit is connected to the second connection end of the second clamping diode module; the second connection end of the second clamping diode module serves as the second output end of the surge and lightning protection unit and is grounded after passing through the third clamping diode module.

4. The protection device of the 485 communication interface circuit according to any one of claims 1 to 3, characterized in that: The first filtering unit includes: a common mode inductor module; the common mode inductor module has a first winding and a second winding; the RS485 communication chip has an A pin and a B pin; wherein, The first output end of the surge and lightning protection unit is connected to the first connection end of the first winding; the second connection end of the first winding, as the first output end of the first filtering unit, can be connected to the B pin of the RS485 chip; The second output end of the surge and lightning protection unit is connected to the first connection end of the second winding; the second connection end of the second winding, as the first output end of the first filtering unit, can be connected to the A pin of the RS485 chip.

5. The protection device of the 485 communication interface circuit according to any one of claims 1 to 4, characterized in that: Also includes: The second filtering unit; wherein, A preset DC power supply is grounded after passing through the second filtering unit; The preset DC power supply and the common end of the second filtering unit are connected to the power supply end of the RS485 communication chip.

6. The protection device for the 485 communication interface circuit according to claim 5, characterized in that: The second filtering unit includes: a filtering capacitor module.

7. The protection device for the 485 communication interface circuit according to any one of claims 1 to 6, characterized in that: Also includes: A pull-up resistor unit; wherein, The preset DC power supply is connected to the A pin of the RS485 communication chip after passing through the pull-up resistor unit.

8. The protection device for the 485 communication interface circuit according to any one of claims 1 to 7, characterized in that: Also includes: Current limiting unit; wherein, The current limiting unit is arranged between the first filtering unit and the RS485 communication chip, and is used to limit the current in the RS485 communication interface circuit to achieve overcurrent protection for the RS485 communication interface circuit.

9. The protection device for the 485 communication interface circuit according to claim 8, characterized in that: The current limiting unit includes: a first current limiting resistor module and a second current limiting resistor module; wherein, The first current limiting resistor module is arranged between the first output end of the first filtering unit and the B pin of the RS485 communication chip; the second current limiting resistor module is arranged between the second output end of the first filtering unit and the A pin of the RS485 communication chip; Among them, when the first filtering unit includes a common-mode inductor module, the first current limiting resistor module is arranged between the second connection end of the first winding of the common-mode inductor module and the B pin of the RS485 communication chip; the second current limiting resistor module is arranged between the second connection end of the second winding of the common-mode inductor module and the A pin of the RS485 communication chip.

10. A 485 communication interface circuit, characterized in that: include: A protection device for a 485 communication interface circuit as claimed in any one of claims 1 to 9.

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