Alternating-current voltage zero-crossing communication circuit

Abstract

The invention relates to an alternating-current voltage zero-crossing communication circuit, belongs to the field of power signal communication, and is particularly suitable for alternating-current power supply communication application of a low-communication-flow internet-of-things terminal. The circuit comprises an alternating-current voltage zero-cross detection circuit and a pulse signal transceiving circuit. The alternating-current voltage zero-crossing detection circuit is used for detecting zero-crossing points of positive and negative half cycles of an alternating-current power supply and outputting zero-crossing signals; the pulse signal receiving and transmitting circuit comprises a pulse signal receiving module and a pulse signal transmitting module and is used for receiving or injecting short-time pulses at a zero crossing point to realize a communication function. The sending module controls a direct-current power supply to excite a coupling coil through an MOS tube, triggers a silicon controlled rectifier to discharge at a zero crossing point, and loads a pulse signal to a power line; the receiving module extracts pulse signals in a power grid in a direct current blocking amplitude limiting and voltage dividing coupling mode and sends the pulse signals to a control system for recognition. The system is simple in structure and low in cost, has good anti-interference capability and communication stability, and is suitable for low-power-consumption embedded communication in scenes of street lamp control, smart home, fire fighting systems and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of power signal communication, and in particular to an AC voltage zero-crossing communication circuit. Background Art

[0002] With the rapid development of the Internet of Things (IoT), intelligent control systems, and automation technologies, more and more terminal devices require communication capabilities to receive control commands or upload status information. However, in real-world application scenarios such as streetlight control, smart homes, and fire alarms, a large number of terminals are widely distributed, with strict power consumption constraints. Communication requirements are simple but reliability is critical. Therefore, achieving basic communication at low cost and low power consumption has become a key technical bottleneck.

[0003] Traditional communication solutions typically rely on wireless modules (such as Zigbee, LoRa, and Wi-Fi) or the installation of dedicated communication cables. However, these solutions have numerous drawbacks, including susceptibility to interference, numerous coverage blind spots, and high power consumption. Wiring increases installation complexity and costs, making it particularly unsuitable for retrofitting existing power grids. To address these needs, a zero-crossing communication method, which requires no additional communication media and directly utilizes AC power for signal transmission, is gaining increasing attention.

[0004] AC voltage zero-crossing communication involves injecting a pulse signal into the power line near the AC voltage's zero-crossing point, leveraging its near-zero voltage. This pulse signal is then received and demodulated by a matching circuit to achieve data transmission. This method does not rely on the wireless spectrum or require additional wiring, offering advantages such as low cost, minimal interference, and a simple structure. It is particularly suitable for low-rate control communications.

[0005] Although the existing zero-crossing communication circuit is feasible in principle, it still has the following problems: Low zero-crossing detection accuracy: Under strong interference or mains power fluctuations, traditional circuits are prone to misjudgment, affecting communication timing; Sending signals to disturb the power grid: Some solutions directly inject high current pulses, which may cause power interference and affect other equipment; Insufficient receiving sensitivity or easy false triggering: The receiving circuit lacks effective limiting protection and anti-interference capabilities, resulting in false operation or signal loss; Complex structure or high cost: Using a large number of analog amplifiers, isolation transformers or high-frequency filters takes up space and is not conducive to integration.

[0006] Therefore, there is an urgent need for an AC voltage zero-crossing communication circuit with a simple structure, strong anti-interference ability, controllable cost, and high adaptability to achieve reliable and low-cost embedded communication functions, which is suitable for large-scale deployment of industrial or civilian equipment control systems.

[0007] It is based on the above background that the present invention is proposed, and aims to provide a new AC voltage zero-crossing communication circuit that can achieve accurate communication at the zero-crossing point of the AC power supply. It has the advantages of high recognition, strong anti-interference, low power consumption and easy deployment, and is particularly suitable for scenarios such as the Internet of Things, smart lighting and emergency control. Summary of the Invention

[0008] The object of the present invention is to provide an AC voltage zero-crossing communication circuit to solve the problems raised by the above background technology.

[0009] To achieve the above object, the present invention provides the following technical solution: an AC voltage zero-crossing communication circuit, comprising: AC voltage zero-crossing detection circuit, comprising: Resistor R1, one end of which is connected to the live wire L of the AC power supply, and the other end is connected to the negative electrode of the voltage regulator tube D1; The positive pole of the voltage regulator D1 is connected to the neutral line N of the AC power supply; A resistor R2, one end of which is connected to the common point of R1 and D1, and the other end of which is connected to the positive electrode of the light-emitting diode of the optocoupler U1, and the negative electrode of the light-emitting diode is connected to the neutral line N of the AC power supply; The emitter of the photoelectric receiving tube of the optical coupler U1 is grounded, the collector is connected to the capacitor C1 and one end of the resistor R3, the other end of the capacitor C1 is grounded, and the other end of the resistor R3 is connected to the DC power supply VCC; The collector of the photoelectric receiving tube outputs an AC zero-crossing signal ZERO; The pulse signal transceiver circuit includes: Pulse receiving path: one end of capacitor C2 is connected to the live wire L, and the other end is connected to resistor R4. The other end of R4 is connected to the cathode of limiting diode D2, the anode of limiting diode D3 and one end of resistor R5 in sequence; the anode of D2 and the cathode of D3 are connected to the neutral line N; the other end of R5 is connected to the third pin of coupling coil T1. The fourth pin of T1 is respectively connected to the cathode of transient suppressor D6, the cathode of protection diode D7, the anode of diode D8 and one end of resistor R10. The anodes of transient suppressor D6 and diode D7 are both grounded, and the cathode of diode D8 is connected to power supply VH. The other end of resistor R10 is connected to one end of capacitor C6, and the other end of capacitor C6 is connected to the pulse receiving signal ZB_IN; Pulse sending path: The 4th pin of T1 is connected to the 3rd pin of MOS tube U2, and the 6th pin of T1 is grounded; The second pin of the MOS transistor U2 is connected to one end of the resistor R11, the cathode of the diode D9, and the DC power supply VH respectively. The first pin of the MOS transistor U2 is connected to the other end of the resistor R11, the anode of the diode D9, and one end of the capacitor C7. The capacitor C7 is connected in series with the resistor R12. The other end of the resistor R12 is connected to the input pulse control signal PULSE. The third pin of T1 is further connected to one end of resistor R9, the other end of which is connected to one end of capacitor C5, one end of resistor R8, and the anode of diode D5. The cathode of diode D5 is connected to one end of resistor R7 and the third pin of thyristor Q1. One end of the capacitor C3 is connected to the live wire L, and the other end is respectively connected to one end of the capacitor C4, the cathode of the diode D4 and the second pin of the one-way thyristor Q1. The other end of C4 is connected to one end of the resistor R6. The other end of the resistor R6, the cathode of the diode D4, the first pin of the one-way thyristor Q1, the other end of the resistor R7, the other end of the resistor R8, the other end of the capacitor C5 and the first pin of the coupling coil T1 are connected to the neutral line N of the AC power supply. The DC power supply VH is turned on through U2 to drive T1 to sense the signal, and the signal is injected through Q1 at the AC zero point.

[0010] As a preferred technical solution of the present invention, when the optical coupler U1 detects that the AC voltage crosses the zero point, its photoelectric receiving tube is turned on, causing the ZERO signal to jump from a high level to a low level.

[0011] As a preferred technical solution of the present invention, the MOS tube U2 is turned on when receiving the low-level control signal PULSE, so that a DC current passes through pins 4 to 6 of the coupling coil T1 to form an excitation pulse.

[0012] As a preferred technical solution of the present invention, after receiving the AC pulse signal from capacitor C2 after limiting, the third pin of T1 senses the output at its fourth pin and leads to the pulse receiving identifier ZB_IN through R10 and C6.

[0013] As a preferred technical solution of the present invention, the limiting diodes D2 and D3 are used to limit the amplitude of the pulse voltage transmitted by C2 to prevent damage to the connected circuits.

[0014] As a preferred technical solution of the present invention, the unidirectional thyristor Q1 is used to be triggered to turn on after T1 senses and outputs a pulse, thereby releasing the energy stored in the capacitor C3 and injecting the pulse signal into the AC power grid.

[0015] As a preferred technical solution of the present invention, it also includes a voltage limiting and voltage dividing and anti-interference network composed of capacitor C5, resistors R7, R8, and R9, which is used to ensure that the pulse signal at the receiving end does not trigger Q1 by mistake.

[0016] As a preferred technical solution of the present invention, capacitor C4 and resistor R6 form a resistance-capacitance protection circuit to suppress damage to Q1 caused by high-voltage pulses.

[0017] As a preferred technical solution of the present invention, the unidirectional thyristor Q1 can be replaced by a bidirectional thyristor, and D4 can be removed to achieve the injection of a pulse communication signal at each AC zero-crossing point.

[0018] Compared with the prior art, the present invention has the following beneficial effects: By designing a precise AC voltage zero-crossing detection circuit and optimizing the pulse transceiver structure, this invention achieves the ability to accurately output and identify pulse signals at the AC power zero-crossing point. This communication mechanism offers excellent timing stability and signal integrity, effectively avoiding the false triggering and signal loss issues associated with traditional zero-crossing detection, significantly improving the system's communication reliability and real-time responsiveness.

[0019] The communication circuit of this invention boasts a compact structure, requiring no additional wiring and communicating directly over existing AC power lines. It is suitable for various low-speed control scenarios in mains power environments, such as smart lighting, fire alarms, and IoT terminals. The circuit incorporates amplitude limiting, voltage division, anti-interference, and surge protection modules, effectively enhancing its resistance to electromagnetic interference and overvoltage shocks, ensuring excellent grid adaptability and long-term operational stability.

[0020] This invention utilizes universal components to achieve all functions, resulting in low overall circuit cost and simple wiring, making it suitable for mass integration into existing power equipment. Compared to traditional wireless communication or dedicated wiring methods, this solution significantly reduces system deployment difficulty and communication costs, and has promising prospects for industrial application and market promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces and describes the drawings required for use in the embodiments of the present invention or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0022] Figure 1 The figure is a schematic diagram of the overall structure of an AC voltage zero-crossing communication circuit. DETAILED DESCRIPTION

[0023] In order to further illustrate an AC voltage zero-crossing communication circuit of the present invention, the specific implementation method is described in detail below. These embodiments are only used to illustrate the technical solution of the present invention and do not limit the scope of protection. Equivalent substitutions or improvements made by those skilled in the art without departing from the technical solution of the present invention all fall within the scope of protection of the present invention.

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to the following contents.

[0025] The present invention relates to an AC voltage zero-crossing communication circuit suitable for low-cost short-distance signal transmission in an AC power supply environment. The circuit primarily comprises two modules: an AC voltage zero-crossing detection circuit and a pulse signal transceiver circuit. The zero-crossing detection module detects the critical point at which the AC voltage transitions from positive to negative or negative to positive, while the transceiver module injects and receives pulse signals near the zero-crossing point, thereby establishing a power grid-based communication channel.

[0026] In this embodiment, the AC voltage zero-crossing detection circuit is specifically structured as follows: one end of resistor R1 is connected to the AC power line (L), and the other end is connected to the cathode of a voltage regulator diode D1, the anode of which is connected to the AC power neutral line (N). One end of resistor R2 is connected to the common node of R1 and D1, and the other end is connected to the anode of the light-emitting diode (LED) of optocoupler U1, with its cathode connected to the neutral line (N). During the positive half-cycle of the AC voltage, D1 enters a breakdown state, clamping the voltage. R2 limits the current, turning on U1's LED. The photodiode at the optocoupler output simultaneously turns on, causing its collector voltage to jump from a high level to a low level. After being pulled up and filtered by resistor R3 and capacitor C1, a zero-crossing signal (ZERO) is output. During the negative half-cycle, D1 short-circuits, turning off the LED, and the ZERO signal automatically returns to a high level, thus achieving zero-crossing detection.

[0027] The pulse signal transmission and reception routing consists of two parts: the receiving path and the transmitting path.

[0028] In terms of the receiving path: the AC live wire L is connected to the current-limiting resistor R4 through the capacitor C2. The other end of R4 is simultaneously connected to the cathode of the limiting diode D2, the anode of D3, and one end of the resistor R5. Among them, the anode of D2 and the cathode of D3 are both connected to the neutral line N to limit the AC pulse amplitude and protect the subsequent circuit. The other end of R5 is connected to the third pin of the coupling coil T1. After the output signal is sensed by the fourth pin of T1, it is filtered by the resistor R10 and the capacitor C6 in sequence and output to the signal receiving terminal ZB_IN for acquisition and demodulation by the main control CPU. The sixth pin of T1 is grounded, and the first pin of T1 is grounded together with the power supply neutral line N to form a stable magnetic coupling path. In addition, the fourth pin is also connected to the transient suppressor D6, the cathode of the protection diode D7, and the positive pole of D8 to suppress large-amplitude pulse interference. The positive poles of D6 and D7 are grounded, and the negative pole of D8 is connected to the DC power supply VH to achieve bidirectional overvoltage protection.

[0029] In terms of the transmission path: when the main control CPU needs to send a pulse signal, the output PULSE signal is low level. After the signal is stepped down by the series capacitor C7 and the resistor R12, it controls the 1st pin of the MOS tube U2. The 2nd pin of U2 is connected to the resistor R11, the cathode of the diode D9 and the DC power supply VH, and the anode of D9 is connected to the 1st pin of U2; when U2 is turned on, the VH current is output through the 3rd pin of U2 to the 4th pin of T1, and the 3rd pin of T1 senses a high level pulse and enters the subsequent trigger circuit.

[0030] Pin 3 of T1 is connected to resistor R9, which is connected to the anode of diode D5 and the junction of capacitor C5 and resistor R8. The cathode of D5 is further connected to resistor R7, triggering pin 3 of thyristor Q1. This path is the trigger channel, ensuring that the induction pulse can accurately trigger Q1 to turn on.

[0031] Capacitor C3 is pre-charged in the negative half cycle through diode D4, with one end connected to the live wire L and the other end connected in parallel to capacitor C4, pin 2 of Q1, and the negative electrode of D4. C4 and R6 are connected in series and then to the neutral line N, forming a resistance-capacitance absorption branch to suppress the spike generated by the instantaneous high-voltage discharge of capacitor C3. Pin 1 of Q1, resistors R7, R8, the other end of C5, and pin 1 of T1 are all connected to the neutral line N, forming a complete current discharge path.

[0032] When Q1 is triggered to conduct by D5, C3 releases its charge, forming a short pulse that discharges to the neutral line through Q1's pin 2 to pin 1, thereby injecting the pulse into the grid. The entire process is accomplished through the coordinated efforts of T1 magnetic coupling excitation, MOS drive control, and thyristor energy release, precisely controlling the timing and amplitude of the pulse injection.

[0033] To enhance stability and safety, the circuit also incorporates multiple anti-interference and voltage-limiting modules. R7, R8, R9, and C5 form a voltage-limiting divider network for the received signal, effectively reducing the induced voltage and preventing Q1 from falsely triggering due to excessive voltage. D6, D7, and D8 clamp the sensing side of T1, preventing external overvoltage from damaging critical components. The combination of D9 and R11 controls the bias of MOS transistor U2, enabling it to quickly shut down after the pulse ends, preventing interference caused by continuous conduction.

[0034] In another alternative configuration, D4 can be removed and the unidirectional thyristor Q1 replaced with a bidirectional thyristor. In this case, the system can inject a pulse signal at each positive and negative AC voltage zero crossing. The master controller outputs the pulse signal twice, triggering the bidirectional thyristor to conduct separately, achieving dual-cycle communication and further improving data transmission efficiency.

[0035] The circuit solution of the present invention has been successfully applied to scenarios such as street light control systems, smart home modules, and fire safety reminder devices. It has high communication reliability, easy installation, and no need for additional wiring. It has good practicality and industrial promotion prospects.

[0036] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An AC voltage zero-crossing communication circuit, characterized in that: include: AC voltage zero-crossing detection circuit, comprising: Resistor R1, one end of which is connected to the live wire L of the AC power supply, and the other end is connected to the negative electrode of the voltage regulator tube D1; The positive pole of the voltage regulator D1 is connected to the neutral line N of the AC power supply; A resistor R2, one end of which is connected to the common point of R1 and D1, and the other end of which is connected to the positive electrode of the light-emitting diode of the optocoupler U1, and the negative electrode of the light-emitting diode is connected to the neutral line N of the AC power supply; The emitter of the photoelectric receiving tube of the optical coupler U1 is grounded, the collector is connected to the capacitor C1 and one end of the resistor R3, the other end of the capacitor C1 is grounded, and the other end of the resistor R3 is connected to the DC power supply VCC; The collector of the photoelectric receiving tube outputs an AC zero-crossing signal ZERO; The pulse signal transceiver circuit includes: Pulse receiving path: one end of capacitor C2 is connected to the live wire L, and the other end is connected to resistor R4. The other end of R4 is connected to the cathode of limiting diode D2, the anode of limiting diode D3 and one end of resistor R5 in sequence; the anode of D2 and the cathode of D3 are connected to the neutral line N; the other end of R5 is connected to the third pin of coupling coil T1. The fourth pin of T1 is connected to transient suppressor D6, the cathode of protection diode D7, the anode of diode D8 and one end of resistor R10 respectively. The anodes of transient suppressor D6 and diode D7 are both grounded, and the cathode of diode D8 is connected to power supply VH. The other end of resistor R10 is connected to one end of capacitor C6, and the other end of capacitor C6 is connected to pulse receiving signal ZB_IN; Pulse sending path: The 4th pin of T1 is connected to the 3rd pin of MOS tube U2, and the 6th pin of T1 is grounded; The second pin of the MOS transistor U2 is connected to one end of the resistor R11, the cathode of the diode D9, and the DC power supply VH respectively. The first pin of the MOS transistor U2 is connected to the other end of the resistor R11, the anode of the diode D9, and one end of the capacitor C7. The capacitor C7 is connected in series with the resistor R12. The other end of the resistor R12 is connected to the input pulse control signal PULSE. The third pin of T1 is further connected to one end of resistor R9, the other end of which is connected to one end of capacitor C5, one end of resistor R8, and the anode of diode D5. The cathode of diode D5 is connected to one end of resistor R7 and the third pin of thyristor Q1. One end of the capacitor C3 is connected to the live wire L, and the other end is respectively connected to one end of the capacitor C4, the cathode of the diode D4 and the second pin of the one-way thyristor Q1. The other end of C4 is connected to one end of the resistor R6. The other end of the resistor R6, the cathode of the diode D4, the first pin of the one-way thyristor Q1, the other end of the resistor R7, the other end of the resistor R8, the other end of the capacitor C5 and the first pin of the coupling coil T1 are connected to the neutral line N of the AC power supply. The DC power supply VH is turned on through U2 to drive T1 to sense the signal, and the signal is injected through Q1 at the AC zero point.

2. The communication circuit according to claim 1, wherein: When the optocoupler U1 detects that the AC voltage passes through zero, the photoelectric receiving tube thereof is turned on, causing the ZERO signal to jump from a high level to a low level.

3. The communication circuit according to claim 1, wherein: The MOS tube U2 is turned on when receiving the low-level control signal PULSE, so that a DC current passes through pin 4 to pin 6 of the coupling coil T1 to form an excitation pulse.

4. The communication circuit according to claim 1, wherein: After receiving the limited AC pulse signal from capacitor C2, the third pin of T1 senses the output at its fourth pin and leads to the pulse receiving indicator ZB_IN through R10 and C6.

5. The communication circuit according to claim 1, wherein: The limiting diodes D2 and D3 are used to limit the amplitude of the pulse voltage transmitted by C2 to prevent damage to the connected circuits. The communication circuit according to claim 1 , wherein: The unidirectional thyristor Q1 is used to be triggered to conduct after T1 senses and outputs a pulse, thereby releasing the energy stored in the capacitor C3 and injecting the pulse signal into the AC power grid.

7. The communication circuit according to claim 1, wherein: It also includes a voltage limiting and anti-interference network composed of capacitor C5 and resistors R7, R8, and R9, which is used to ensure that the pulse signal at the receiving end does not trigger Q1 by mistake.

8. The communication circuit according to claim 1, wherein: Capacitor C4 and resistor R6 form a resistance-capacitance protection circuit to suppress damage to Q1 caused by high-voltage pulses.

9. The communication circuit according to claim 1, wherein: The unidirectional thyristor Q1 can be replaced by a bidirectional thyristor, and D4 can be removed to achieve the injection of a pulse communication signal at each AC zero crossing point.

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