Low-cost anti-interference near-infrared communication circuit for electric energy meter and terminal

Abstract

The utility model discloses a low cost anti -interference near infrared communication circuit to the electric energy meter and with the terminal, and this circuit includes transmitting circuit and receiving circuit, and wherein receiving circuit is equipped with shielding control module, and its first control input end connects the signal transmitting end of transmitting circuit, and second control input end connects receiving photosensitive diode, and control output end connects the base of receiving signal output triode, when signal transmitting end sends out signal drive infrared transmitting tube work, shielding control module closes receiving pass according to transmitting signal, and forced receiving signal output end keeps high level to the device receiving false trigger caused by mirror surface reflection or diffuse reflection is blocked. The utility model still has the advantages of low hardware cost and simple circuit when thoroughly eliminating spontaneous self -receiving phenomenon, improves the reliability of infrared communication, is applicable to various electric energy measurement and electric information acquisition terminal equipment.

Description

Technical Field

[0001] This utility model relates to the field of power metering, specifically to a low-cost, anti-interference near-infrared communication circuit for electricity meters and user terminals. Background Technology

[0002] Electricity meters and data collection terminals use near-infrared optical communication to achieve partial data exchange with other devices. For example... Figure 1 and Figure 2 According to the IEC 62056-21 standard, the infrared transmitter and receiver of the same device are set side by side, with a symmetrical center-to-center distance of 6.5mm ± 0.5mm. During communication, the two devices are set opposite each other, with the infrared transmitter of one device facing the infrared receiver of the other device, thus forming two sets of light and shadow transmission paths.

[0003] like Figure 3 In existing infrared communication circuits, the photodiode PD1 at the receiving end conducts after receiving light, directly triggering the transistor V2 to conduct, causing the signal receiver RXD to go low. However, in actual operation, such as... Figure 2 Due to specular and diffuse reflection, some of the light signal from the transmitting end can be reflected or diffusely reflected back to the receiving end of the device, causing misinterpretation at the receiving end, i.e., the "self-transmission and self-reception" phenomenon, which affects communication reliability. Although shielding covers can be placed on the receiving or transmitting tubes to block light interference between adjacent tubes, this does not solve the problem of specular and diffuse reflection. If the received message content is judged and filtered by the MCU, it can only handle regular repetitive messages and cannot cover all situations. Moreover, some devices' infrared transceiver circuits do not have MCU units or related software processing mechanisms.

[0004] To address the aforementioned issues, some existing solutions employ dedicated transceiver isolation devices or complex circuits to achieve the goal of "automatically shielding the received signal during transmission." However, this approach increases costs and circuit complexity, hindering widespread adoption. Utility Model Content

[0005] This invention proposes a low-cost, anti-interference near-infrared communication circuit for electricity meters and user terminals. Its purpose is to avoid the "self-transmission and self-reception" phenomenon caused by the close distance between the infrared transmitter and receiver, reduce receiver misjudgment, improve communication reliability, and at the same time eliminate the need for dedicated transceiver isolation devices or complex circuits, thus avoiding increased costs and circuit complexity.

[0006] The technical solution of this utility model is as follows: A low-cost, interference-resistant near-infrared communication circuit for electricity meters and data acquisition terminals includes a transmitting circuit and a receiving circuit. The receiving circuit includes a photodiode PD2, a pull-up resistor R15, an NPN transistor V12, and a signal output terminal RXD. The negative terminal of the photodiode PD2 is connected to the power supply VDD, and the positive terminal is grounded through a pull-down bias resistor R13. The collector of the NPN transistor V12 is connected to the power supply VDD through the pull-up resistor R15, the emitter is grounded, and the collector of the NPN transistor V12 is connected to the signal output terminal RXD. The receiving circuit further includes a shielding control module; the shielding control module includes a first control input terminal, a second control input terminal, and a control output terminal. The first control input terminal is connected to the signal transmitting terminal TXD of the transmitting circuit, the second control input terminal is connected to the photodiode PD2, and the control output terminal is connected to the base of the NPN transistor V12. When the signal transmitting terminal TXD emits near-infrared light through the transmitting circuit, the shielding control module shields the signal of the photodiode PD2 to keep the signal of the signal output terminal RXD unchanged.

[0007] As a further improvement to the low-cost anti-interference near-infrared communication circuit for electricity meters and user terminals, the shielding control module also includes a PNP transistor V13 and an NPN transistor V14. The PNP transistor V13 is used to control the control output terminal according to the signal of the photodiode PD2, and the NPN transistor V14 is used to control the PNP transistor V13 according to the signal transmitter TXD.

[0008] As a further improvement to the low-cost anti-interference near-infrared communication circuit for electricity meters and user terminals: the emitter of the PNP transistor V13 is connected to the positive terminal of the photodiode PD2 as the second input terminal, the collector is connected to one end of the current-limiting resistor R14, and the other end of the current-limiting resistor R14 is connected to the base of the NPN transistor V12 as the control output terminal.

[0009] As a further improvement to the low-cost anti-interference near-infrared communication circuit for electricity meters and data acquisition terminals: the base of PNP transistor V13 is connected to power supply VDD through voltage divider resistor R16, and is also connected to the collector of NPN transistor V14 through voltage divider resistor R17. The base of the NPN transistor V14 is connected to the current-limiting resistor R18. The other end of the current-limiting resistor R18 is connected to the signal transmitter TXD as the first control input terminal. The emitter of the NPN transistor V14 is grounded.

[0010] As a further improvement to the low-cost, interference-resistant near-infrared communication circuit for electricity meters and user terminals: the transmitting circuit includes a PNP transistor V11, a current-limiting resistor R11, a current-limiting resistor R12, and an infrared emitting diode D2. The signal transmitting terminal TXD of the transmitting circuit is connected to the base of PNP transistor V11 through current limiting resistor R11. The emitter of PNP transistor V11 is connected to power supply VDD. The collector is connected to the positive terminal of infrared emitting diode D2 through current limiting resistor R12. The negative terminal of infrared emitting diode D2 is grounded.

[0011] Compared with the prior art, the present invention has the following advantages: 1. This invention synchronously controls the shutdown of the receiving channel by transmitting a drive signal, forcing the receiving signal output terminal to maintain a high level while the infrared emitting tube is working. This effectively blocks false triggering of the infrared receiving circuit caused by specular reflection or diffuse reflection, fundamentally eliminating the "self-transmitting and self-receiving" phenomenon and improving communication reliability. Furthermore, this mechanism does not rely on dedicated isolation devices or complex shielding structures, making it suitable for various types of energy meters and data acquisition terminals with infrared communication capabilities.

[0012] 2. The circuit proposed in this utility model only uses common discrete components such as general-purpose transistors and resistors, without the need for dedicated chips or complex peripheral circuits, which greatly reduces material costs and manufacturing complexity, and is easy to integrate and mass-produce. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating the center-symmetric spacing requirements of the IEC 62056-21 standard. Figure 2 A schematic diagram showing the positional relationship between two sets of infrared receivers and infrared transmitters for near-infrared communication. Figure 3 This is a schematic diagram of the near-infrared communication circuit for a traditional energy meter and terminal. Figure 4 This is a schematic diagram of the low-cost anti-interference near-infrared communication circuit proposed in this utility model. Detailed Implementation

[0014] The technical solution of this utility model will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0015] This embodiment provides a low-cost, interference-resistant near-infrared communication circuit for electricity meters and data acquisition terminals. Its overall circuit structure is as follows: Figure 4 As shown. The circuit includes a transmitting circuit and a receiving circuit, wherein the receiving circuit further includes a shielding control module.

[0016] The transmitting circuit includes a PNP transistor V11, current-limiting resistors R11 and R12, and an infrared emitting diode D2 as the infrared emitting terminal. The signal transmitting terminal TXD is connected to the base of the PNP transistor V11 through the current-limiting resistor R11. The emitter of the PNP transistor V11 is connected to the power supply VDD, and its collector is connected to the positive terminal of the infrared emitting diode D2 through the current-limiting resistor R12. The negative terminal of the infrared emitting diode D2 is grounded.

[0017] The receiving circuit includes a photodiode PD2 as the infrared receiver, a pull-up resistor R15, an NPN transistor V12, and a signal output terminal RXD. The negative terminal of the photodiode PD2 is connected to the power supply VDD, and the positive terminal is grounded through a pull-down bias resistor R13. The collector of the NPN transistor V12 is connected to the power supply VDD through the pull-up resistor R15, the emitter is grounded, and its collector is connected to the signal output terminal RXD.

[0018] The shielding control module includes a first control input terminal, a second control input terminal, and a control output terminal. The first control input terminal is connected to the signal transmitting terminal TXD of the transmitting circuit, the second control input terminal is connected to the positive terminal of the photodiode PD2, and the control output terminal is connected to the base of the NPN transistor V12.

[0019] Specifically, the shielding control module also includes a PNP transistor V13 and an NPN transistor V14. The emitter of the PNP transistor V13 is connected to the positive terminal of the photodiode PD2 as the second control input terminal, and its collector is connected to one end of the current-limiting resistor R14. The other end of the current-limiting resistor R14 is connected to the base of the NPN transistor V12 as the control output terminal. The base of the PNP transistor V13 is connected to the power supply VDD through the voltage divider resistor R16, and is also connected to the collector of the NPN transistor V14 through the voltage divider resistor R17. The base of the NPN transistor V14 is connected to one end of the current-limiting resistor R1, and the other end of the current-limiting resistor R1 is connected to the signal transmitting terminal TXD as the first control input terminal. The emitter of the NPN transistor V14 is grounded.

[0020] The working principle of this utility model is as follows: First, the infrared communication circuit uses serial communication. Only after the internal infrared transmitting circuit has finished transmitting and the external infrared receiving transistors have received the correct information will the external receiver send a serial response; there is no situation where both sides transmit simultaneously. During communication intervals, the internal transmitting signal TXD remains high by default.

[0021] Scenario 1: When there is no communication, i.e., neither party is sending nor receiving, TXD is high, and infrared emitter D2 does not emit light. Simultaneously, NPN transistor V14 is turned on, and its collector is low. At this time, photodiode PD2 is cut off as it does not receive light, PNP transistor V13 is cut off, and NPN transistor V12 is also cut off. The signal output terminal RXD is kept high through pull-up resistor R15.

[0022] Scenario 2: When this device transmits but the other device does not: If the TXD of this device is high and the infrared emitter D2 does not emit light, then the circuit state is the same as in case 1, and the signal output terminal RXD remains high.

[0023] If TXD of this device is low, the infrared emitter D2 emits light. The NPN transistor V14 is cut off due to its low base, while its collector is high. This causes the base voltage of the PNP transistor V13 to rise and cut off. Therefore, the NPN transistor V12 remains cut off, and RXD remains high, effectively avoiding interference caused by self-emission and self-reception.

[0024] Scenario 3: When this device is not transmitting and the other device is transmitting, the TXD of this device is high, the infrared emitting diode D2 does not emit light, the photodiode PD2 is only affected by the near-infrared light emitted by the other device, and at the same time, the NPN transistor V14 is conducting, and the base voltage of the PNP transistor V13 is the voltage after voltage division. If the infrared light emitted by the other party illuminates the photodiode PD2, its impedance decreases. At this time, current flows through the photodiode PD2, the emitter junction of the PNP transistor V13, and resistor R17 to the NPN transistor V14, turning on the PNP transistor V13. The output voltage of the collector of the PNP transistor V13 turns on the NPN transistor V12, thereby pulling the RXD signal low and realizing normal external signal reception.

[0025] If the other device does not emit infrared light, the photodiode PD2 of this device is not exposed to light and is in the off state, the PNP transistor V13 is off, which in turn causes the NPN transistor V12 to be off, and RXD remains at a high level.

[0026] Through the above working mechanism, this invention can automatically shield the receiving path during transmission, effectively solving the problem of reflected light interference while maintaining the integrity of normal receiving function. The entire circuit is implemented using only general-purpose discrete components, resulting in low cost and applicability to various types of electricity meters and data acquisition terminal equipment.

[0027] It should be noted that, as will be apparent to those skilled in the art, this utility model is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this utility model. The scope of this utility model is defined by the claims rather than the foregoing description.

Claims

1. A low-cost, interference-resistant near-infrared communication circuit for electricity meters and data acquisition terminals, comprising a transmitting circuit and a receiving circuit, wherein the receiving circuit comprises a photodiode PD2, a pull-up resistor R15, an NPN transistor V12, and a signal output terminal RXD; the negative terminal of the photodiode PD2 is connected to the power supply VDD, and the positive terminal is grounded through a pull-down bias resistor R13; the collector of the NPN transistor V12 is connected to the power supply VDD through the pull-up resistor R15, the emitter is grounded, and the collector of the NPN transistor V12 is connected to the signal output terminal RXD; Its features are: The receiving circuit further includes a shielding control module; the shielding control module includes a first control input terminal, a second control input terminal, and a control output terminal. The first control input terminal is connected to the signal transmitting terminal TXD of the transmitting circuit, the second control input terminal is connected to the photodiode PD2, and the control output terminal is connected to the base of the NPN transistor V12. When the signal transmitting terminal TXD emits near-infrared light through the transmitting circuit, the shielding control module shields the signal of the photodiode PD2 to keep the signal of the signal output terminal RXD unchanged.

2. The low-cost, interference-resistant near-infrared communication circuit for electricity meters and user terminals as described in claim 1, characterized in that: The shielding control module also includes a PNP transistor V13 and an NPN transistor V14. The PNP transistor V13 is used to control the control output terminal according to the signal of the photodiode PD2, and the NPN transistor V14 is used to control the PNP transistor V13 according to the signal transmitter TXD.

3. The low-cost, interference-resistant near-infrared communication circuit for electricity meters and user terminals as described in claim 2, characterized in that: The emitter of the PNP transistor V13 is connected to the positive terminal of the photodiode PD2 as the second input terminal, and the collector is connected to one end of the current-limiting resistor R14. The other end of the current-limiting resistor R14 is connected to the base of the NPN transistor V12 as the control output terminal.

4. The low-cost, interference-resistant near-infrared communication circuit for electricity meters and user terminals as described in claim 3, characterized in that: The base of PNP transistor V13 is connected to power supply VDD through voltage divider resistor R16, and is also connected to the collector of NPN transistor V14 through voltage divider resistor R17. The base of NPN transistor V14 is connected to current-limiting resistor R18. The other end of current-limiting resistor R18 is connected to the signal transmitter TXD as the first control input terminal. The emitter of NPN transistor V14 is grounded.

5. The low-cost, interference-resistant near-infrared communication circuit for electricity meters and user terminals as described in any one of claims 1 to 4, characterized in that: The transmitting circuit includes a PNP transistor V11, a current-limiting resistor R11, a current-limiting resistor R12, and an infrared emitting diode D2; The signal transmitting terminal TXD of the transmitting circuit is connected to the base of PNP transistor V11 through current limiting resistor R11. The emitter of PNP transistor V11 is connected to power supply VDD. The collector is connected to the positive terminal of infrared emitting diode D2 through current limiting resistor R12. The negative terminal of infrared emitting diode D2 is grounded.

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