A communication interface protection circuit for industrial access control systems

Abstract

The invention discloses a communication interface protection circuit of an industry access control system, comprising a main control CPU module, and the CPU module is bidirectionally connected to an external device via a bidirectional RS485 communication interface protection circuit; the CPU module is also connected to an anti-reverse connection power interface protection circuit; the bidirectional RS485 communication interface protection circuit comprises an RS485 control chip U501, resistors R514, R516, R517, R518, R519, R520, R521 and R522, capacitors C506 and C507, bidirectional diodes T508 and T509, a diode D501 and a triode Q503. The invention automatically disconnects in case of mis-insertion, wrong insertion and reverse insertion, thereby protecting the machine and the equipment. If the wrong connection does not work, the fault is eliminated, and the machine automatically resumes the working state. Whether indoors or outdoors, in a strong magnetic field or in a strong interference environment, the normal operation of the machine will not be affected.

Description

Technical Field

[0001] The present invention relates to the technical field related to access control communication interface protection circuits, and in particular to an industry access control system communication interface protection circuit. Background Art

[0002] Industrial access control machines have many interfaces for data transmission with external devices to control external devices, switches, electric locks, central control, elevators and other equipment. These interfaces are all industrial sockets, which are very compact and quick-connect design, which is convenient for customers to quickly connect and improve work efficiency. The interfaces of industrial access control machines include power interface, short-circuit input, short-circuit output, alarm IO, Wiegand, RS485, etc. If there is a power supply interface nearby, the wiring master accidentally fails to see the wrong connection or connects the wrong position, and the main control CPU of the access control machine will burn out directly, because the external adapter is generally DC: DC 12V, DC 24V, DC 36V, etc., and the level voltage of the CPUIO communication interface is generally 3.3V. Therefore, as long as the power cord is mistakenly connected to the signal port, the main control will be burned out; or the power supply voltage of the power interface is higher than the nominal voltage, the power module will also burn out. The newly purchased machine broke down before it was used. In addition, these wires and communication lines will be laid indoors and outdoors; there are many magnetic fields and interference occasions with elevators, transformers, and motors. Summary of the invention

[0003] In order to solve the defects of the prior art, the present invention provides a communication interface protection circuit for an industry access control system.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] The present invention discloses a communication interface protection circuit for an industry access control system, comprising a main control CPU module, wherein the CPU module is bidirectionally connected to an external device via a bidirectional RS485 communication interface protection circuit; the CPU module is also connected to an anti-reverse power interface protection circuit;

[0006] The bidirectional RS485 communication interface protection circuit includes an RS485 control chip U501, resistors R514, R516, R517, R518, R519, R520, R521 and R522,

[0007] Capacitors C506 and C507, bidirectional diodes T508 and T509, diode D501 and transistor Q503;

[0008] The RO pin of the RS485 control chip U501 is connected to the RS485_RO pin on the CPU module, and one end of the resistor R519 is connected to one end of the resistor R521, and is also connected to the RS485_DI pin of the CPU module, and the other end of the resistor R521 is connected to 3V3_DC, and is also connected to one end of the resistor R516, the other end of the resistor R519 is connected to the b pole of the transistor Q503, and the e pole of the transistor Q503 is grounded, the c pole of the transistor Q503 is connected to the DE and RE pins of the RS485 control chip U501, and is also connected to the other end of the resistor R516;

[0009] One end of the resistor R520 is connected to the B pin of the RS485 control chip U501, and is also connected to one end of the resistor R522, and the other end of the resistor R522 is grounded;

[0010] The A pin of the RS485 control chip U501 is connected to one end of the resistor R517 and one end of the resistor R514, the other end of the resistor R517 is connected to RS485_A, the other end of the resistor R520 is connected to RS485_B and one end of the resistor R518, and the other end of the resistor R518 is connected to the other end of R517;

[0011] The other end of the resistor R514 is connected to one end of the capacitors C506 and C507, and is also connected to the cathode of the diode D501, and the anode of the diode D501 is connected to D5V. The other end of the resistor R514 is also connected to the VCC pin of the RS485 control chip U501, and the other ends of the capacitors C506 and C507 are grounded;

[0012] One end of the bidirectional diode T508 is connected to the other end of the resistor R517 , one end of the bidirectional diode T509 is connected to the other end of the resistor R520 , and the other ends of the bidirectional diodes T508 and T509 are grounded.

[0013] As a preferred technical solution of the present invention, a recoverable fuse F502 is connected in series between the resistor R517 and RS485_A, and a recoverable fuse F501 is connected in series between the resistor R520 and RS485_B.

[0014] As a preferred technical solution of the present invention, it also includes an electrostatic protection diode T510 connected to RS485_A and RS485_B, and the model of the electrostatic protection diode T510 is SM712.

[0015] As a preferred technical solution of the present invention, it also includes an anti-reverse power interface protection circuit for powering the CPU module; the anti-reverse power interface protection circuit includes a three-stage tube Q701, diodes D701 and D702, a PMOS tube Q702, a bidirectional TVS tube T701, resistors R701, R702, R703, R704, R705, and R706; capacitors C701, C702, C703, C704, C705, C706, C707, C708, and C709, a common mode inductor L701, an inductor L702, magnetic beads FB701 and FB702,

[0016] The anode of the diode D701 is connected to the positive electrode, the cathode of the diode D701 is connected to one end of the resistor R703, the other end of the resistor R703 is connected to the cathode of the diode D702, and is also connected to the B pole of the transistor Q701, the anode of the diode D702 is connected to one end of the resistors R701, R704, and R705, and the other ends of the resistors R701, R704, and R705 are connected, and are also connected to the negative electrode, and the anode of the bidirectional TVS tube T701 is connected to one end of the resistors R701, R704, and R705. The cathode of the bidirectional TVS tube T701 is connected to the anode, and the cathode of the bidirectional TVS tube T701 is connected to the anode, one end of the resistor R706 is connected to the cathode, and the other end of the resistor R706 is connected to the C electrode of the triode Q701, one end of the resistor R702, one end of the capacitor C701 and the G electrode of the PMOS tube Q702, and the S electrode of the PMOS tube Q702 is connected to the other end of the capacitor C701, the other end of the resistor R702, the E electrode of the triode and the cathode of the diode D701;

[0017] The D pole of the PMOS tube Q702 is connected to the 3rd pin of the common mode inductor L701, and the cathode is connected to the 4th pin of the common mode inductor, and the capacitors C702 and C703 are connected in parallel between the 3rd pin and the 4th pin of the common mode inductor L701;

[0018] The magnetic bead FB701 is connected in parallel between the 3rd and 2nd pins of the common mode inductor L701, and the magnetic bead FB702 is connected in parallel between the 4th and 1st pins of the common mode inductor L701;

[0019] Pin 1 of the common-mode inductor L701 is connected to one end of capacitors C704, C705, C706, C707, C708 and C709, and the other ends of the capacitors C704 and C708 are connected to pin 2 of the common-mode inductor L701, and pin 2 of the common-mode inductor L701 is connected to one end of the inductor L702, and the other end of the inductor L702 is connected to the other ends of C705, C706, C707 and C709, and the other end of C709 is connected to the power output.

[0020] As a preferred technical solution of the present invention, it also includes a capacitor EC701, one end of the capacitor EC701 is connected to the other end of the inductor L702, and the other end of the capacitor EC701 is connected to pin 1 of the common mode inductor L701.

[0021] As a preferred technical solution of the present invention, the model of the bidirectional TVS tube T701 is BV-5SMDJ48CA.

[0022] As a preferred technical solution of the present invention, the model of the bidirectional diodes T508 and T509 is BV-SMCJ5CA.

[0023] As a preferred technical solution of the present invention, the model of the diode D701 is ZMM13.

[0024] The beneficial effects of the present invention are:

[0025] 1. The communication interface protection circuit of this industry access control system will automatically disconnect in case of mis-insertion, wrong insertion, or reverse insertion to protect the machine and equipment. If the wrong connection does not work, the machine will automatically resume working after the fault is eliminated. Whether indoors or outdoors, in strong magnetic fields, or in strong interference environments, the normal operation of the machine will not be affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 It is a structural schematic diagram of a communication interface protection circuit of an industry access control system of the present invention;

[0028] Figure 2 It is a structural schematic diagram of an anti-reverse connection power interface protection circuit of a communication interface protection circuit of an industry access control system of the present invention;

[0029] Figure 3 The invention discloses a bidirectional RS485 communication interface protection circuit of a communication interface protection circuit of an industry access control system.

[0030] In the figure: 1. CPU module; 2. Bidirectional RS485 communication interface protection circuit; 3. Anti-reverse power interface protection circuit. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0032] Example: Figure 1 , Figure 2 and Figure 3 As shown, the present invention is a communication interface protection circuit of an industry access control system, comprising a main control CPU module 1, and the CPU module 1 is bidirectionally connected to an external device via a bidirectional RS485 communication interface protection circuit 2; the CPU module 1 is also connected to an anti-reverse power interface protection circuit 3;

[0033] The bidirectional RS485 communication interface protection circuit includes an RS485 control chip U501, resistors R514, R516, R517, R518, R519, R520, R521 and R522, capacitors C506 and C507, bidirectional diodes T508 and T509, a diode D501 and a transistor Q503;

[0034] The RO pin of the RS485 control chip U501 is connected to the RS485_RO pin on the CPU module, and one end of the resistor R519 is connected to one end of the resistor R521, and is also connected to the RS485_DI pin of the CPU module, and the other end of the resistor R521 is connected to 3V3_DC, and is also connected to one end of the resistor R516, the other end of the resistor R519 is connected to the b pole of the transistor Q503, and the e pole of the transistor Q503 is grounded, the c pole of the transistor Q503 is connected to the DE and RE pins of the RS485 control chip U501, and is also connected to the other end of the resistor R516; one end of the resistor R520 is connected to the B pole of the RS485 control chip U501 The A pin of the RS485 control chip U501 is connected to one end of the resistor R517 and to one end of the resistor R514, the other end of the resistor R517 is connected to RS485_A, the other end of the resistor R520 is connected to RS485_B, and is connected to one end of the resistor R518, and the other end of the resistor R518 is connected to the other end of R517;

[0035] The other end of the resistor R514 is connected to one end of the capacitors C506 and C507, and is also connected to the cathode of the diode D501, and the anode of the diode D501 is connected to D5V. The other end of the resistor R514 is also connected to the VCC pin of the RS485 control chip U501, and the other ends of the capacitors C506 and C507 are grounded; one end of the bidirectional diode T508 is connected to the other end of the resistor R517, one end of the bidirectional diode T509 is connected to the other end of the resistor R520, and the other ends of the bidirectional diodes T508 and T509 are grounded. The first pin of the U501 RS485 control chip is directly connected to the CPU, and the 2nd and 3rd pins are connected to the main control CPU after being level-isolated by Q503. The U501 chip realizes two-way communication with external RS485 protocol devices through pins 6 and 7. The wiring of the RS485 wiring port may be laid outdoors, or passed under strong magnetism or strong transformers. T508 and T509 bidirectional diodes can provide lightning protection, surge protection, and EFT protection. The model of T508 and T509 is BV-SMCJ5CA, and the RS485 communication interface level is 5V. The bidirectional TVS tube clamping voltage selected by the present invention is also 5V. When the wiring is normal, the TVS is not turned on and presents a high-resistance state. When the master makes a wrong connection or misoperation, once the working voltage of the high-voltage T508 and T509 bidirectional TVS tube exceeds 5V, the TVS tube conducts the current, and the protection is immediately provided to protect U501 and the main control CPU, and stop RS485 communication. The electrician found that RS485 was not working. After removing the wrong wire, RS485 communication automatically returned to normal. Assuming that any one of the RS485_A and RS485_B communication lines is short-circuited to the ground, F501 and F502 can restore the fuse. It is detected that the current of RS485_A and RS485_B communication lines exceeds the set value, and the PPTC impedance also increases and heats up, causing the PPTC fuse to disconnect. The entire circuit is protected.

[0036] A recoverable fuse F502 is connected in series between the resistor R517 and RS485_A, and a recoverable fuse F501 is connected in series between the resistor R520 and RS485_B. An electrostatic protection diode T510 connected to RS485_A and RS485_B is also included, and the model of the electrostatic protection diode T510 is SM712.

[0037] The anti-reverse connection power interface protection circuit (3) comprises a transistor Q701, diodes D701 and D702, a PMOS transistor Q702, a bidirectional TVS transistor T701, resistors R701, R702, R703, R704, R705, R706; capacitors C701, C702, C703, C704, C705, C706, C707, C708 and C709, a common mode inductor L701, an inductor L702, magnetic beads FB701 and FB702,

[0038] The anode of the diode D701 is connected to the positive electrode, the cathode of the diode D701 is connected to one end of the resistor R703, the other end of the resistor R703 is connected to the cathode of the diode D702, and is also connected to the B pole of the transistor Q701, the anode of the diode D702 is connected to one end of the resistors R701, R704, and R705, and the other ends of the resistors R701, R704, and R705 are connected, and are also connected to the negative electrode, and the anode of the bidirectional TVS tube T701 is connected to one end of the resistors R701, R704, and R705. The cathode of the bidirectional TVS tube T701 is connected to the anode, and the cathode of the bidirectional TVS tube T701 is connected to the anode, one end of the resistor R706 is connected to the cathode, and the other end of the resistor R706 is connected to the C electrode of the triode Q701, one end of the resistor R702, one end of the capacitor C701 and the G electrode of the PMOS tube Q702, and the S electrode of the PMOS tube Q702 is connected to the other end of the capacitor C701, the other end of the resistor R702, the E electrode of the triode and the cathode of the diode D701;

[0039] The D pole of the PMOS tube Q702 is connected to the 3rd pin of the common mode inductor L701, and the cathode is connected to the 4th pin of the common mode inductor, and the capacitors C702 and C703 are connected in parallel between the 3rd pin and the 4th pin of the common mode inductor L701;

[0040] The magnetic bead FB701 is connected in parallel between the 3rd and 2nd pins of the common mode inductor L701, and the magnetic bead FB702 is connected in parallel between the 4th and 1st pins of the common mode inductor L701;

[0041] Pin 1 of the common mode inductor L701 is connected to one end of capacitors C704, C705, C706, C707, C708 and C709, and the other ends of the capacitors C704 and C708 are connected to pin 2 of the common mode inductor L701, and pin 2 of the common mode inductor L701 is connected to one end of the inductor L702, and the other end of the inductor L702 is connected to the other ends of C705, C706, C707 and C709, and the other end of C709 is connected to the power output. If the positive and negative polarities of the power supply are reversed, under the action of the D701 diode, using the forward conduction principle of the diode, assuming that the polarity of the power port is reversed, D701 can only conduct unidirectionally. Therefore, the circuit does not work. This circuit also has redundant protection. Since the polarity of the power supply voltage of the Q702 PMOS tube is opposite, the G-pole gate voltage of the MOS tube is incorrect, and the MOS tube is in a closed state, which protects the subsequent circuit. T701 is a bidirectional TVS tube, model BV-5SMDJ48CA, with a maximum operating voltage of 48V. When the power supply voltage of the external wiring port exceeds 48V, T701 uses the characteristics of the TVS tube to instantly avalanche and protect the circuit; when the power supply voltage is lower than 48V, the TVS tube quickly returns to normal; this bidirectional TVS tube is SMC packaged, with a power of 1500W, anti-air electrostatic discharge + / -15KV, contact electrostatic discharge + / -8KV, anti-surge + / -2KV or more, and anti-pulse wave level up to IEC61000-4-4 (IEC801-4). All incoming interference signals are filtered out without affecting the operation of the subsequent circuits. The correct power supply voltage of this device is DC 12V. Assuming that the master picked up a power adapter and plugged it into the machine, the voltage of these adapters may be 24V, 36V, 48V, etc. But the voltage of these power adapters is higher than the normal working voltage of the machine. In order to prevent the machine from burning out due to the wrong voltage, the D702 voltage regulator can provide good overvoltage protection. The model of the D702 voltage regulator diode is ZMM13. When the voltage across the voltage regulator diode exceeds 14.1V, the voltage regulator diode works to protect the subsequent circuit. When the positive power supply voltage returns to below 14.1V, the voltage regulator diode stops working. The entire power supply returns to normal. Because the power line may be installed in a complex environment, these strong interference signals are coupled in through the power line, causing common-mode noise interference. If the common-mode interference signals are transmitted through the power line, these interference signals will make the CPU and digital signals unstable, and the machine will be sometimes good and sometimes bad. Therefore, the L701 common-mode inductor is added to the power management circuit. The common-mode inductor can effectively suppress interference signals and protect the back-end digital circuits and more sensitive analog circuits.

[0042] The device further includes a capacitor EC701 , one end of which is connected to the other end of the inductor L702 , and the other end of the capacitor EC701 is connected to pin 1 of the common mode inductor L701 .

[0043] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A communication interface protection circuit for an industry access control system, characterized in that: The device comprises a main control CPU module (1), wherein the CPU module (1) is bidirectionally connected to an external device via a bidirectional RS485 communication interface protection circuit (2); the CPU module (1) is also connected to an anti-reverse power interface protection circuit (3); The bidirectional RS485 communication interface protection circuit includes an RS485 control chip U501, resistors R514, R516, R517, R518, R519, R520, R521 and R522, Capacitors C506 and C507, bidirectional diodes T508 and T509, diode D501 and transistor Q503; The RO pin of the RS485 control chip U501 is connected to the RS485_RO pin on the CPU module, and one end of the resistor R519 is connected to one end of the resistor R521, and is also connected to the RS485_DI pin of the CPU module, and the other end of the resistor R521 is connected to 3V3_DC, and is also connected to one end of the resistor R516, the other end of the resistor R519 is connected to the b pole of the transistor Q503, and the e pole of the transistor Q503 is grounded, the c pole of the transistor Q503 is connected to the DE and RE pins of the RS485 control chip U501, and is also connected to the other end of the resistor R516; One end of the resistor R520 is connected to the B pin of the RS485 control chip U501, and is also connected to one end of the resistor R522, and the other end of the resistor R522 is grounded; The A pin of the RS485 control chip U501 is connected to one end of the resistor R517 and one end of the resistor R514, the other end of the resistor R517 is connected to RS485_A, the other end of the resistor R520 is connected to RS485_B and one end of the resistor R518, and the other end of the resistor R518 is connected to the other end of R517; The other end of the resistor R514 is connected to one end of the capacitors C506 and C507, and is also connected to the cathode of the diode D501, and the anode of the diode D501 is connected to D5V. The other end of the resistor R514 is also connected to the VCC pin of the RS485 control chip U501, and the other ends of the capacitors C506 and C507 are grounded; One end of the bidirectional diode T508 is connected to the other end of the resistor R517, one end of the bidirectional diode T509 is connected to the other end of the resistor R520, and the other ends of the bidirectional diodes T508 and T509 are grounded; The anti-reverse connection power interface protection circuit (3) comprises a transistor Q701, diodes D701 and D702, a PMOS transistor Q702, a bidirectional TVS transistor T701, resistors R701, R702, R703, R704, R705, R706; capacitors C701, C702, C703, C704, C705, C706, C707, C708 and C709, a common mode inductor L701, an inductor L702, magnetic beads FB701 and FB702, The anode of the diode D701 is connected to the positive electrode, the cathode of the diode D701 is connected to one end of the resistor R703, the other end of the resistor R703 is connected to the cathode of the diode D702, and is also connected to the B pole of the transistor Q701, the anode of the diode D702 is connected to one end of the resistors R701, R704, and R705, and the other ends of the resistors R701, R704, and R705 are connected, and are also connected to the negative electrode, and the anode of the bidirectional TVS tube T701 is connected to one end of the resistors R701, R704, and R705. The cathode of the bidirectional TVS tube T701 is connected to the anode, and the cathode of the bidirectional TVS tube T701 is connected to the anode, one end of the resistor R706 is connected to the cathode, and the other end of the resistor R706 is connected to the C electrode of the triode Q701, one end of the resistor R702, one end of the capacitor C701 and the G electrode of the PMOS tube Q702, and the S electrode of the PMOS tube Q702 is connected to the other end of the capacitor C701, the other end of the resistor R702, the E electrode of the triode and the cathode of the diode D701; The D pole of the PMOS tube Q702 is connected to the 3rd pin of the common mode inductor L701, and the cathode is connected to the 4th pin of the common mode inductor, and the capacitors C702 and C703 are connected in parallel between the 3rd pin and the 4th pin of the common mode inductor L701; The magnetic bead FB701 is connected in parallel between the 3rd and 2nd pins of the common mode inductor L701, and the magnetic bead FB702 is connected in parallel between the 4th and 1st pins of the common mode inductor L701; Pin 1 of the common-mode inductor L701 is connected to one end of capacitors C704, C705, C706, C707, C708 and C709, and the other ends of the capacitors C704 and C708 are connected to pin 2 of the common-mode inductor L701, and pin 2 of the common-mode inductor L701 is connected to one end of the inductor L702, and the other end of the inductor L702 is connected to the other ends of C705, C706, C707 and C709, and the other end of C709 is connected to the power output.

2. The communication interface protection circuit of an industry access control system according to claim 1 is characterized in that: A resettable fuse F502 is connected in series between the resistor R517 and RS485_A, and a resettable fuse F501 is connected in series between the resistor R520 and RS485_B.

3. The communication interface protection circuit of an industry access control system according to claim 2 is characterized in that: It also includes an electrostatic protection diode T510 connected to RS485_A and RS485_B, and the model of the electrostatic protection diode T510 is SM712.

4. The communication interface protection circuit of an industrial access control system according to claim 1, characterized in that: The device further includes a capacitor EC701 , one end of which is connected to the other end of the inductor L702 , and the other end of the capacitor EC701 is connected to pin 1 of the common mode inductor L701 .

5. The communication interface protection circuit of an industrial access control system according to claim 1, characterized in that: The model of the bidirectional TVS tube T701 is BV-5SMDJ48CA.

6. The communication interface protection circuit of an industrial access control system according to claim 1, characterized in that: The model of the bidirectional diodes T508 and T509 is BV-SMCJ5CA.

7. The communication interface protection circuit of an industrial access control system according to claim 1, characterized in that: The model of the diode D701 is ZMM13.

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