Contact type IC card optocoupler isolation communication circuit of intelligent electric meter

Abstract

The utility model discloses a contact type IC card optocoupler isolation communication circuit of an intelligent electric meter. The contact type IC card optocoupler isolation communication circuit comprises a main control module, a contact type IC card circuit and an optocoupler isolation circuit, the optical coupler isolation circuit is electrically connected with the master control module and the contact type IC card circuit. The contact type IC card circuit comprises a contact type IC card holder, a protection circuit and a clock circuit; the contact type IC card seat is electrically connected with the protection circuit, and the protection circuit is electrically connected with the clock circuit and the optical coupler isolation circuit. According to the utility model, the technical problems that the existing optocoupler isolation circuit cannot be suitable for different IC cards and is poor in compatibility are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of smart electric meters, in particular to a contact IC card optical coupling isolation communication circuit for a smart electric meter. Background Art

[0002] In smart meter applications, there is a need for contact IC cards, which are divided into CPU cards (smart cards) and logic encryption cards. Since contact IC cards may touch the circuit, this part of the circuit is required to be isolated from the main control unit circuit to prevent the risk of electric shock.

[0003] The key signals of the IC card include the reset signal RST, the clock signal CLK, the data signal DIO, the card in place signal SW, the power supply VCPU, and the ground CGND. Among them, the data signal DIO is a serial data input and output, and there is a problem in the implementation of single-line bidirectional signal isolation. At present, there are dedicated single-line bidirectional isolation communication chips, such as the IIC communication interface circuit, and SDA is a single-line bidirectional communication, but such dedicated chips have the disadvantages of high price and a relatively small selection range. At the same time, its isolation voltage level is difficult to meet industrial-grade requirements. At present, there are also related designs that use optocouplers and triodes to build single-line bidirectional optocoupler isolation circuits, but they do not consider the specific application scenarios and circuit function realization, use more separators, and have high requirements for PCB space. In addition, consider the differences in communication timing of different IC cards. For example, the CPU card tends to be UART asynchronous serial timing, and when using a logic encryption card, its communication timing is more inclined to IIC timing. Compatibility design issues need to be considered here. At present, the mainstream implementation method is to isolate the data signal of the contact IC card through a single-line bidirectional isolation device or functional circuit, and connect the isolated signal to the main control module, which realizes the serial input and output timing. This method will increase the difficulty of software development. At the same time, there are difficulties in debugging the asynchronous timing UART timing simulated by the software. At the same time, due to the differences in the internal resistance design of the IC card signal interface of different manufacturers, there is a risk of communication abnormality due to the difference in signal edge change. Therefore, it is urgent to propose a smart meter contact IC card optical coupler isolation communication circuit to solve the technical problems that the existing optical coupler isolation circuit cannot be applied to different IC cards and has poor compatibility. Utility Model Content

[0004] The main purpose of the utility model is to provide a smart meter contact IC card optical coupler isolation communication circuit, aiming to solve the technical problems that the existing optical coupler isolation circuit cannot be applied to different IC cards and has poor compatibility.

[0005] To achieve the above object, the utility model provides a smart meter contact IC card optical coupler isolation communication circuit, wherein the smart meter contact IC card optical coupler isolation communication circuit comprises:

[0006] Main control module, contact IC card circuit and optocoupler isolation circuit;

[0007] The optical coupling isolation circuit is electrically connected to the main control module and the contact IC card circuit respectively;

[0008] The contact IC card circuit comprises a contact IC card holder, a protection circuit and a clock circuit; the contact IC card holder is electrically connected to the protection circuit, and the protection circuit is electrically connected to the clock circuit and the optical coupling isolation circuit respectively.

[0009] In one of the preferred solutions, the optical coupler isolation circuit includes a first optical coupler isolation circuit;

[0010] The first optocoupler isolation circuit includes an isolation optocoupler N1; pin 1 of the isolation optocoupler N1 is respectively connected to the power supply end and the protection circuit through resistor R6; pin 2 of the isolation optocoupler N1 is connected to the protection circuit; pin 3 of the isolation optocoupler N1 is respectively connected to resistor R1 and the card-in-place pin of the main control module, and the other end of the resistor R1 is grounded; pin 4 of the isolation optocoupler N1 is respectively connected to the power supply end and resistor R4.

[0011] In one of the preferred solutions, the optical coupler isolation circuit includes a second optical coupler isolation circuit;

[0012] The second optocoupler isolation circuit includes an isolation optocoupler N2; pin 1 of the isolation optocoupler N2 is connected to the power supply end through a resistor R2; pin 2 of the isolation optocoupler N2 is connected to the reset pin of the main control module; pin 3 of the isolation optocoupler N2 is respectively connected to a resistor R10 and a protection circuit, and the other end of the resistor R10 is grounded; pin 4 of the isolation optocoupler N2 is connected to the power supply end.

[0013] In one of the preferred solutions, the optical coupler isolation circuit includes a third optical coupler isolation circuit;

[0014] The third optocoupler isolation circuit includes an isolation optocoupler N3 and an isolation optocoupler N4; pin 1 of the isolation optocoupler N3 is connected to the power supply end through a resistor R3; pin 2 of the isolation optocoupler N3 is connected to the signal sending pin of the main control module; pin 3 of the isolation optocoupler N3 is grounded; pin 4 of the isolation optocoupler N3 is respectively connected to a resistor R7 and a protection circuit; the other end of the resistor R7 is connected to the power supply end; pin 1 of the isolation optocoupler N4 is connected to the power supply end through a resistor R8; pin 2 of the isolation optocoupler N4 is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the protection circuit through a resistor R11, and the collector of the transistor Q1 is grounded; pin 3 of the isolation optocoupler N4 is grounded; pin 4 of the isolation optocoupler N4 is respectively connected to the resistor R4 and the signal receiving pin of the main control module.

[0015] In one of the preferred solutions, the optical coupler isolation circuit includes a fourth optical coupler isolation circuit;

[0016] The fourth optocoupler isolation circuit includes an isolation optocoupler N5; pin 1 of the isolation optocoupler N5 is connected to the power supply end through a resistor R5; pin 2 of the isolation optocoupler N5 is connected to the clock pin of the main control module; pin 3 of the isolation optocoupler N5 is grounded; pin 4 of the isolation optocoupler N5 is respectively connected to resistor R9 and resistor R15, the other end of the resistor R9 is connected to the power supply end, and the other end of the resistor R15 is respectively connected to the clock circuit and the protection circuit.

[0017] One of the preferred schemes, the clock circuit includes an inverter U1A, an inverter U1B, an inverter U1C, a resistor R12, a resistor R13, a resistor R14, a resistor R16, a crystal oscillator Y1, a capacitor C1, a capacitor C2 and a capacitor C3; one end of the resistor R16 is connected to the protection circuit; the other end of the resistor R16 is connected to the 10th pin of the inverter U1C, the 8th and 9th pins of the inverter U1C are connected to the resistor R14 and the capacitor C3, the other end of the resistor R14 is respectively connected to the resistor R13, the capacitor C2, the crystal oscillator Y1 and the 4th pin of the inverter U1B, the 5th and 6th pins of the inverter U1B are connected to the 1st pin of the inverter U1A, the resistor R12 and the other end of the resistor R13, the 2nd and 3rd pins of the inverter U1A are respectively connected to the other end of the resistor R12, the capacitor C1 and the other end of the crystal oscillator Y1; the other ends of the capacitors C1, C2 and C3 are grounded.

[0018] In one of the preferred solutions, the protection circuit includes a thermistor and a voltage-stabilizing diode; the voltage-stabilizing diode and the thermistor are arranged in parallel.

[0019] In the above technical solution of the utility model, the smart meter contact IC card optical coupling isolation communication circuit includes: a main control module, a contact IC card circuit and an optical coupling isolation circuit; the optical coupling isolation circuit is electrically connected to the main control module and the contact IC card circuit respectively; the contact IC card circuit includes a contact IC card holder, a protection circuit and a clock circuit; the contact IC card holder is electrically connected to the protection circuit, and the protection circuit is electrically connected to the clock circuit and the optical coupling isolation circuit respectively. The utility model solves the technical problems that the existing optical coupling isolation circuit cannot be applied to different IC cards and has poor compatibility.

[0020] In the utility model, the smart meter contact IC card optocoupler isolation communication circuit is suitable for CPU card and logic encryption card, has a simple circuit structure, is easy to use, and occupies little device space. At the same time, according to the characteristics of CPU card and logic encryption card, compatibility design is implemented, which improves the circuit's ability to use different IC cards and the communication success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 This is a schematic diagram of a smart meter contacting an IC card optical coupling isolation communication circuit according to an embodiment of the utility model;

[0023] Figure 2 The figure is a schematic diagram of a contact IC card circuit according to an embodiment of the present utility model.

[0024] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0026] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0027] Furthermore, the technical solutions between the various implementation modes of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0028] See also Figure 1-Figure 2 According to one aspect of the utility model, the utility model provides a smart meter contact IC card optical coupling isolation communication circuit, wherein the smart meter contact IC card optical coupling isolation communication circuit comprises: a main control module, a contact IC card circuit and an optical coupling isolation circuit;

[0029] The optical coupling isolation circuit is electrically connected to the main control module and the contact IC card circuit respectively;

[0030] The contact IC card circuit comprises a contact IC card holder, a protection circuit and a clock circuit; the contact IC card holder is electrically connected to the protection circuit, and the protection circuit is electrically connected to the clock circuit and the optical coupling isolation circuit respectively.

[0031] Specifically, in this embodiment, when the contact IC card is inserted into the contact IC card holder J1, the generated contact IC card communication signal is transmitted to the optocoupler isolation circuit through the protection circuit, and the clock circuit for providing a clock signal to the CPU card is connected to the IC card clock signal port through the protection circuit; the contact IC card holder J1 is a universal holder, and the internal in-place spring SW and CGND are in a normally open state. When a card is in place, SW and CGND are short-circuited, SW is pulled down to the first level, and the first optocoupler isolation circuit is in a working state.

[0032] Specifically, in this embodiment, the protection circuit includes a thermistor and a zener diode; the zener diode and the thermistor are arranged in parallel; the protection circuit is used to prevent abnormal overvoltage and overcurrent signals from damaging internal components of the functional circuit.

[0033] Specifically, in this embodiment, the optical coupling isolation circuit includes a first optical coupling isolation circuit;

[0034] The first optocoupler isolation circuit includes an isolation optocoupler N1; pin 1 of the isolation optocoupler N1 is respectively connected to the power supply end and the protection circuit through a resistor R6; pin 2 of the isolation optocoupler N1 is connected to the protection circuit; pin 3 of the isolation optocoupler N1 is respectively connected to the resistor R1 and the card-in-place pin of the main control module, and the other end of the resistor R1 is grounded; pin 4 of the isolation optocoupler N1 is respectively connected to the power supply end and the resistor R4; the first optocoupler isolation circuit is used to isolate the card-in-place signal. When the contact IC card is in place, SW becomes a low level and IC_SW becomes a high level, thereby notifying the main control module that the contact IC card is in place.

[0035] Specifically, in this embodiment, the optocoupler isolation circuit includes a second optocoupler isolation circuit;

[0036] The second optocoupler isolation circuit includes an isolation optocoupler N2; pin 1 of the isolation optocoupler N2 is connected to the power supply end through a resistor R2; pin 2 of the isolation optocoupler N2 is connected to the reset pin of the main control module; pin 3 of the isolation optocoupler N2 is respectively connected to a resistor R10 and a protection circuit, and the other end of the resistor R10 is grounded; pin 4 of the isolation optocoupler N2 is connected to the power supply end; the second optocoupler isolation circuit is used to isolate the reset signal. When the main control module sets the reset signal IC_RST to a low level, the RST of the contact IC card circuit becomes a high level. At this time, the contact IC card can communicate normally, and the RST of the contact IC card circuit defaults to a low level, that is, after the contact IC card is inserted, the RST pin is not set high, and the contact IC card cannot operate normally.

[0037] Specifically, in this embodiment, the optical coupling isolation circuit includes a third optical coupling isolation circuit;

[0038] The third optocoupler isolation circuit includes an isolation optocoupler N3 and an isolation optocoupler N4; pin 1 of the isolation optocoupler N3 is connected to the power supply end through a resistor R3; pin 2 of the isolation optocoupler N3 is connected to the signal sending pin of the main control module; pin 3 of the isolation optocoupler N3 is grounded; pin 4 of the isolation optocoupler N3 is respectively connected to a resistor R7 and a protection circuit; the other end of the resistor R7 is connected to the power supply end; pin 1 of the isolation optocoupler N4 is connected to the power supply end through a resistor R8; pin 2 of the isolation optocoupler N4 is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the protection circuit through a resistor R11, and the collector of the transistor Q1 is grounded; the isolation optocoupler N4 Pin 3 is grounded; Pin 4 of the isolation optocoupler N4 is respectively connected to the resistor R4 and the signal receiving pin of the main control module; the third optocoupler isolation circuit is used for isolating serial communication signals IC_TXD and IC_RXD. When the main control module sends data through the IC_TXD signal, the data signal DIO of the contact IC card circuit will become the same level. When the level of the contact IC card data signal DIO changes, the isolation optocoupler N4 is driven by the transistor Q1 signal to send the diode current, and the main control module IC_RXD will become the same level. Therefore, when the main control module is required to send serial data, the serial data receiving function is turned off, and when the data is sent, the serial data receiving function is turned on.

[0039] Specifically, in this embodiment, the optical coupling isolation circuit includes a fourth optical coupling isolation circuit;

[0040] The fourth optocoupler isolation circuit includes an isolation optocoupler N5; pin 1 of the isolation optocoupler N5 is connected to the power supply end through a resistor R5; pin 2 of the isolation optocoupler N5 is connected to the clock pin of the main control module; pin 3 of the isolation optocoupler N5 is grounded; pin 4 of the isolation optocoupler N5 is respectively connected to resistor R9 and resistor R15, the other end of the resistor R9 is connected to the power supply end, and the other end of the resistor R15 is respectively connected to the clock circuit and the protection circuit; the fourth optocoupler isolation circuit is used to isolate the logic encryption card clock signal IC_CLK. When the main control module sends a clock signal through IC_CLK, the contact IC card circuit clock signal CLK becomes the same level.

[0041] Specifically, in this embodiment, the clock circuit includes an inverter U1A, an inverter U1B, an inverter U1C, a resistor R12, a resistor R13, a resistor R14, a resistor R16, a crystal oscillator Y1, a capacitor C1, a capacitor C2 and a capacitor C3; one end of the resistor R16 is connected to the protection circuit; the other end of the resistor R16 is connected to pin 10 of the inverter U1C, pins 8 and 9 of the inverter U1C are connected to the resistor R14 and the capacitor C3, the other end of the resistor R14 is respectively connected to the resistor R13, the capacitor C2, the crystal oscillator Y1 and the pin 4 of the inverter U1B, the pins 5 and 6 of the inverter U1B are connected to pin 1 of the inverter U1A, the resistor R12 and the other end of the resistor R13, the pins 2 and 3 of the inverter U1A are respectively connected to the other end of the resistor R12, the capacitor C1 and the other end of the crystal oscillator Y1; the other ends of the capacitors C1, C2 and C3 are grounded.

[0042] Specifically, in this embodiment, the main control module has the characteristics of a common port of a universal serial transceiver pin and a common IO pin; when the contact IC card is a CPU card, the signal receiving pin and the signal sending pin of the main control module can be combined with software to simulate the 7816 protocol framing. The utility model does not make specific limitations, and specifically uses conventional software to simulate the 7816 protocol framing; for the protection time required in the 7816 protocol, the stop bit in the serial transceiver can be used to simulate. Generally, the protection time is two time units, so two stop bits can be used to simulate, with the AD in the 7816 protocol Take the PU instruction as an example, that is, the main control module sends a command to the CPU card, the command consists of a command header and a command body; the command header includes the instruction category CLA, the instruction code INS, the parameter P1 and the parameter P2; the command body includes the data length Lc, the data field DATA and the number of data bytes Le that are expected to be answered when responding; the command format can be divided into the following four cases: format 1 is: CLA+INS+P1+P2; format 2 is: CLA+INS+P1+P2+Le; format 3 is: CLA+INS+P1+P2+Lc+DATA; format 3 is: CLA+INS+P1 +P2+Lc+DATA+Le; In general, for the command frame with data field DATA, it is required that after sending five bytes of CLA+INS+P1+P2+Lc, it is necessary to wait for the CPU card to return INS before the main control module sends the data field DATA; In addition, the clock CLK of the hardware part is provided by the clock circuit of the CPU card end, the clock signal sent by the main control module is disconnected, and the reset signal is realized by the main control module through optical coupling isolation control; When the contact IC card is a logic encryption card, the signal sending pin and signal receiving pin of the universal serial transceiver of the main control module are configured as ordinary IO The logic encryption card is actually an EEPROM with a logic encryption circuit. The signal sending pin is configured as an output port in the main control module, and the signal receiving pin is configured as an input port. The main control module can simulate a dual-port IIC communication timing. The timing of IIC is not specifically described in this utility model, and conventional timing can be used; its key implementation includes start signal, end signal, response signal, read timing, write timing, etc.; in addition, the hardware part clock CLK is provided by the main control module, the clock circuit of the contact IC card circuit is disconnected, and the reset signal is controlled by the main control module through an optical coupler isolation circuit.

[0043] Specifically, in this embodiment, when the contact IC card is a CPU card, the small series resistor R15 is not attached, the contact IC card clock is provided by the clock circuit, the crystal oscillator Y1 frequency is generally selected to be 3.5795MHz, and the duration occupied by each bit in the 7816 protocol, that is, the time unit calculation formula is: 1etu=(F / D)*(1 / f), the default value of F is 372, f=3.5795MHz, and D can be set to 1 / 2 / 4 respectively, so the communication rate supported by the CPU card can be 9600 / 19200 / 38400bps respectively, and the default value of D is 1, that is, etu is 10.39ms, and the communication baud rate is 9600bps, where etu is the time unit; the CPU card has a built-in central processing unit CPU, a programmable read-only memory EEPROM, a random access memory RAM, and a solidified card operating system COS (Chip Operating System System) and read-only memory ROM, etc., which are not specifically limited in the present invention and can be set according to needs; when the CPU card is inserted into the card slot, the SW of the contact IC card circuit becomes low level, and the IC_SW on the main control module side becomes low level at the same time. After multiple level judgments, the main control module determines that a card insertion event has occurred; when a card insertion event occurs, the CPU card is in an activated state (RST is low level, VCPU is high level, and the clock signal is stable and normal). The main control module first controls IC_RST to be set to a low level, and the RST on the contact IC card side changes from a low level to a high level, that is, a cold reset is generated for the CPU card. Under normal circumstances, the CPU card will have a reset response to tell the main control module the communication parameters related to the IC card, such as the F and D values ​​calculated by etu, and the subsequent main control module The block and the CPU card can communicate through a single-line bidirectional isolated optocoupler signal channel according to the normal 7816 protocol process; the specific data link layer and physical layer implementation process is that the asynchronous transceiver of the main control module (signal receiving pin, signal sending pin) works in asynchronous half-duplex mode. When the asynchronous transceiver is in the sending state, its serial receiving function is set to off. At this time, the contact IC card circuit DIO level is consistent with the main control module side IC_TXD; when the main control module finishes sending data, the asynchronous transceiver serial receiving function is set to on, and the serial sending function is set to off. The contact IC card circuit side signal DIO is controlled by the CPU card, and its level drives the PNP transistor Q1 to work. At this time, the IC_RXD on the main control module side is consistent with the contact IC card circuit side signal DIO level characteristics.

[0044] Specifically, in this embodiment, when the contact IC card is a logic encryption card, the series small resistor R16 is not attached, and the IC card clock is provided by the main control module through the isolation optocoupler circuit. The data transmission rate is related to the clock signal of the main control module and is generally set within 50kHz; the logic encryption card has a built-in encryption logic circuit and a programmable read-only memory EEPROM. The encryption logic circuit protects the security of the card and the data in the card to a certain extent, but cannot prevent malicious attacks; when the logic encryption card is inserted into the card slot, the SW on the contact IC card circuit side becomes a low level, and the IC_SW on the main control module side becomes a low level at the same time. After multiple level judgments, the main control module determines that a card insertion event has occurred; when a card insertion event occurs, the main control module first controls IC_RST to be set to a low level and then to a high level. The RST on the contact IC card circuit side changes from the default low level to a high level and then to a high level. At this time, the logic encryption card receives a reset instruction. Under normal circumstances, the logic encryption card will return a reset response with a 32-bit address; after the reset response, The logic encryption card acts as a slave waiting for the host's command. The host command format is generally composed of "start + (control word + address word + data word) + additional pulse + stop bit"; at this time, the two sides of the optocoupler isolation circuit are equivalent to the IIC bus communication system with a master-slave relationship composed of the main control module and the logic encryption card; the specific data link layer and physical layer implementation process is that the main control module uses two IOs, one as output DO (shared port with TXD) and the other as input DI (shared port with RXD) to simulate the IIC timing and interact with the logic encryption card on the contact IC card side; when the main control module side sends data through DO and CLK, after the data is sent, the DIO on the contact IC card side is in a high-impedance state, and the subsequent bus is controlled by the logic encryption card. The main control module controls IC_CLK to continuously output, and the data signal line DIO drives the PNP transistor Q1 to work. At this time, the DI on the main control module side is consistent with the level characteristics of the signal DIO on the contact IC card side, and the main control module receives the IIC data returned by the logic encryption card.

[0045] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A smart meter contact IC card optical coupler isolation communication circuit, characterized in that: include: Main control module, contact IC card circuit and optocoupler isolation circuit; The optical coupling isolation circuit is electrically connected to the main control module and the contact IC card circuit respectively; The contact IC card circuit comprises a contact IC card holder, a protection circuit and a clock circuit; the contact IC card holder is electrically connected to the protection circuit, and the protection circuit is electrically connected to the clock circuit and the optical coupling isolation circuit respectively.

2. A smart meter contact IC card optical coupling isolation communication circuit according to claim 1, characterized in that: The optocoupler isolation circuit includes a first optocoupler isolation circuit; The first optocoupler isolation circuit includes an isolation optocoupler N1; pin 1 of the isolation optocoupler N1 is respectively connected to the power supply end and the protection circuit through resistor R6; pin 2 of the isolation optocoupler N1 is connected to the protection circuit; pin 3 of the isolation optocoupler N1 is respectively connected to resistor R1 and the card-in-place pin of the main control module, and the other end of the resistor R1 is grounded; pin 4 of the isolation optocoupler N1 is respectively connected to the power supply end and resistor R4.

3. A smart meter contact IC card optical coupling isolation communication circuit according to any one of claims 1-2, characterized in that: The optocoupler isolation circuit includes a second optocoupler isolation circuit; The second optocoupler isolation circuit includes an isolation optocoupler N2; pin 1 of the isolation optocoupler N2 is connected to the power supply end through a resistor R2; pin 2 of the isolation optocoupler N2 is connected to the reset pin of the main control module; pin 3 of the isolation optocoupler N2 is respectively connected to a resistor R10 and a protection circuit, and the other end of the resistor R10 is grounded; pin 4 of the isolation optocoupler N2 is connected to the power supply end.

4. A smart meter contact IC card optical coupling isolation communication circuit according to any one of claims 1-2, characterized in that: The optocoupler isolation circuit includes a third optocoupler isolation circuit; The third optocoupler isolation circuit includes an isolation optocoupler N3 and an isolation optocoupler N4; pin 1 of the isolation optocoupler N3 is connected to the power supply end through a resistor R3; pin 2 of the isolation optocoupler N3 is connected to the signal sending pin of the main control module; pin 3 of the isolation optocoupler N3 is grounded; pin 4 of the isolation optocoupler N3 is respectively connected to a resistor R7 and a protection circuit; the other end of the resistor R7 is connected to the power supply end; pin 1 of the isolation optocoupler N4 is connected to the power supply end through a resistor R8; pin 2 of the isolation optocoupler N4 is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the protection circuit through a resistor R11, and the collector of the transistor Q1 is grounded; pin 3 of the isolation optocoupler N4 is grounded; pin 4 of the isolation optocoupler N4 is respectively connected to the resistor R4 and the signal receiving pin of the main control module.

5. A smart meter contact IC card optical coupling isolation communication circuit according to any one of claims 1-2, characterized in that: The optocoupler isolation circuit includes a fourth optocoupler isolation circuit; The fourth optocoupler isolation circuit includes an isolation optocoupler N5; pin 1 of the isolation optocoupler N5 is connected to the power supply end through a resistor R5; pin 2 of the isolation optocoupler N5 is connected to the clock pin of the main control module; pin 3 of the isolation optocoupler N5 is grounded; pin 4 of the isolation optocoupler N5 is respectively connected to resistor R9 and resistor R15, the other end of the resistor R9 is connected to the power supply end, and the other end of the resistor R15 is respectively connected to the clock circuit and the protection circuit.

6. A smart meter contact IC card optical coupling isolation communication circuit according to any one of claims 1-2, characterized in that: The clock circuit includes an inverter U1A, an inverter U1B, an inverter U1C, a resistor R12, a resistor R13, a resistor R14, a resistor R16, a crystal oscillator Y1, a capacitor C1, a capacitor C2 and a capacitor C3; one end of the resistor R16 is connected to the protection circuit; the other end of the resistor R16 is connected to the 10th pin of the inverter U1C, the 8th and 9th pins of the inverter U1C are connected to the resistor R14 and the capacitor C3, the other end of the resistor R14 is respectively connected to the resistor R13, the capacitor C2, the crystal oscillator Y1 and the 4th pin of the inverter U1B, the 5th and 6th pins of the inverter U1B are connected to the 1st pin of the inverter U1A, the resistor R12 and the other end of the resistor R13, the 2nd and 3rd pins of the inverter U1A are respectively connected to the other end of the resistor R12, the capacitor C1 and the other end of the crystal oscillator Y1; the other ends of the capacitors C1, C2 and C3 are grounded.

7. A smart meter contact IC card optical coupling isolation communication circuit according to any one of claims 1-2, characterized in that: The protection circuit comprises a thermistor and a voltage-stabilizing diode; the voltage-stabilizing diode is arranged in parallel with the thermistor.

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