A single-phase intelligent electric energy meter fire zero line reverse connection detection circuit

Abstract

The utility model relates to the technical field of electric energy meter, concretely relates to a single -phase intelligent electric energy meter fire zero line reverse connection detection circuit, including copper foil board, triode Q1, triode Q7, resistance R1, resistance R2, resistance R4, inductive capacitor C1 and inductive capacitor C2, wherein, one end of copper foil board connects zero line N through inductive capacitor C2, and other end connects triode Q7's base and connects fire line L through resistance R2, the collector of triode Q7 connects high level through resistance R4, and the emitter of triode Q7 connects triode Q1's base, the collector of triode Q1 connects the MCU of single -phase intelligent electric energy meter, and connects high level through resistance R1, and the emitter of triode Q1 connects fire line L, and connects zero line N through inductive capacitor C1. Through adding pull -down resistance in copper foil inductive current position, the strength of triode amplification signal is improved by modifying two resistance resistance value shunt, and two triodes carry out two -stage amplification to signal synchronously, and the sensitivity of amplification signal is improved.

Description

Technical Field

[0001] This utility model relates to the field of electricity meter technology, specifically to a single-phase smart electricity meter live and neutral wire reverse connection detection circuit. Background Technology

[0002] With the continuous advancement of smart grid construction, the application of single-phase smart meters is becoming increasingly widespread. However, during the installation of these meters, the live and neutral wires are frequently reversed, posing a serious safety hazard. Currently, most electrical appliances on the market are designed to disconnect the live wire. If the live and neutral wires of the meter are reversed, the disconnected wire will become the neutral wire, causing the live wire to remain continuously connected to the appliance. In situations such as humid weather, aging or damaged appliances, or electrical leaks, contact with these appliances can easily lead to electric shock, seriously threatening the user's life and potentially causing secondary disasters such as electrical fires.

[0003] Currently, a common solution for detecting reverse connection of the live and neutral wires in existing technology involves adding a copper foil plate inside the meter and connecting it to the gate of a MOSFET. A voltage level signal is then output to a microcontroller via a transistor for detection and judgment. Specifically, when the microcontroller detects a low voltage level, it determines that the live and neutral wires are reversed; if it detects a 50Hz or 60Hz high / low voltage signal, it considers the live and neutral wires to be connected correctly. Although this solution can achieve basic live / neutral wire reverse connection detection, it still reveals many shortcomings in practical applications.

[0004] From the perspective of detection accuracy, this solution is insufficient to meet the high-precision detection requirements in low-current scenarios. Because the induced signal generated by a low current is weak, high-precision devices are required to ensure consistent detection under the same conditions. However, high-precision devices are often expensive, increasing product manufacturing costs, and their stability is also challenged in complex electromagnetic environments.

[0005] Regarding environmental adaptability, the actual installation environments of electricity meters vary greatly, resulting in significant differences in the magnitude of the induced signal under different conditions. Existing solutions lack effective signal conditioning mechanisms and cannot flexibly adjust the input signal magnitude according to the actual environment. This leads to inaccurate detection results or even misjudgments in some environments, severely limiting the application scope of the solution.

[0006] In the signal processing stage, the existing solution's signal amplification design has shortcomings. The input induced signal is only amplified by a MOSFET in one stage, while the second stage of amplification requires a pull-up power supply. This design not only increases the complexity of the circuit but also reduces the sensitivity of the input signal, making it difficult to effectively capture and amplify weak signals, thus affecting the timeliness and accuracy of live / neutral reverse connection detection. Utility Model Content

[0007] To overcome the shortcomings of the prior art, this application provides a single-phase smart energy meter live and neutral wire reverse connection detection circuit, which aims to detect whether the live and neutral wires are reversed in a more efficient, accurate and stable manner.

[0008] The technical means adopted by this utility model to solve its technical problem is: a single-phase intelligent energy meter live and neutral wire reverse connection detection circuit, the improvement of which is that it includes a copper foil plate, transistor Q1, transistor Q7, resistor R1, resistor R2, resistor R4, sensing capacitor C1, and sensing capacitor C2, wherein,

[0009] One end of the copper foil plate is connected to the neutral line N through the inductive capacitor C2, and the other end is connected to the base of the transistor Q7 and connected to the live line L through the resistor R2.

[0010] The collector of transistor Q7 is connected to a high level through resistor R4, and the emitter of transistor Q7 is connected to the base of transistor Q1.

[0011] The collector of transistor Q1 is connected to the MCU of the single-phase smart energy meter and connected to a high level through resistor R1. The emitter of transistor Q1 is connected to the live wire L and connected to the neutral wire N through sensing capacitor C1.

[0012] In the above technical solution, transistors Q1 and Q7 are both NPN type high-precision DC current gain transistors with a β value range of 20-450.

[0013] In the above technical solution, the MCU determines whether the live and neutral wires are reversed by detecting the voltage level change at the collector of transistor Q1.

[0014] If the voltage level is consistently high, it indicates that the live and neutral wires are reversed.

[0015] If it is a high or low level pulse signal, then the live and neutral wires are connected correctly.

[0016] The copper foil plate described in the above technical solution has a rectangular structure with a length of 10–15 mm, a width of 2–3 mm, and a thickness of 35 μm, and is used to sense the AC potential difference between the live wire L and the neutral wire N.

[0017] The frequency of the high and low level pulse signals in the above technical solution is 50Hz or 60Hz, the high level threshold is ≥0.7Vcc, the low level threshold is ≤0.3Vcc, and Vcc is the MCU power supply voltage.

[0018] The high-level signal in the above technical solution is provided by the internal DC power supply of the electricity meter, with a voltage range of 3.3V or 5V.

[0019] The beneficial effects of this utility model are:

[0020] This application adds a pull-down resistor at the copper foil induced current position and modifies the resistance values ​​of the two resistors to shunt the current, thereby improving the strength of the transistor amplified signal. The input signal passes through two transistors, and the two transistors synchronously amplify the signal in two stages, improving the sensitivity of the amplified signal. Attached Figure Description

[0021] Figure 1 This is a connection diagram of a single-phase smart energy meter live and neutral wire reverse connection detection circuit shown in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] The following will clearly and completely describe the concept, specific structure, and technical effects of this utility model in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are all within the scope of protection of this utility model. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this utility model can be combined interactively without contradicting each other.

[0024] As mentioned earlier, if the live and neutral wires of a single-phase smart meter are reversed during installation, it poses a safety hazard to the user. Most electrical appliance switches disconnect the live wire. If the live and neutral wires are reversed, the switch disconnects the appliance, leaving the live wire connected to the appliance. In humid weather, if the appliance is old, damaged, or has a leakage, there is a risk of electric shock if someone comes into contact with it. Therefore, a function that can detect reversed live and neutral wire connections in a smart meter is crucial.

[0025] like Figure 1 As shown, this application provides a single-phase smart energy meter live / neutral wire reverse connection detection circuit, including a copper foil plate, transistors Q1 and Q7, resistors R1, R2, and R4, sensing capacitors C1 and C2, wherein...

[0026] One end of the copper foil plate is connected to the neutral line N through the inductive capacitor C2, and the other end is connected to the base of the transistor Q7 and connected to the live line L through the resistor R2.

[0027] The collector of transistor Q7 is connected to a high level through resistor R4, and the emitter of transistor Q7 is connected to the base of transistor Q1; the high level is provided by the internal DC power supply of the energy meter, with a voltage range of 3.3V or 5V.

[0028] The collector of transistor Q1 is connected to the MCU of the single-phase smart energy meter and connected to a high level through resistor R1. The emitter of transistor Q1 is connected to the live wire L and connected to the neutral wire N through sensing capacitor C1.

[0029] In one possible implementation, the copper foil plate is a rectangular structure with a length of 10–15 mm, a width of 2–3 mm, and a thickness of 35 μm, used to sense the alternating potential difference between the live wire L and the neutral wire N.

[0030] When copper foil is used as a sensing element, its area is proportional to the induced potential. Therefore, a reasonable length and width design can maximize the sensing area in a limited space, thereby improving the detection accuracy of the weak AC potential difference between the live wire and the neutral wire. A rectangular structure can balance the sensing area and the compactness of the layout in a limited space.

[0031] like Figure 1 As shown, there is a voltage difference between the copper foil plate and the neutral line N, which is stored in the induced capacitor C2. During the 50Hz or 60Hz half-cycle of the State Grid, if the voltage of the neutral line N is higher than that of the live line L, an induced current will be generated in the copper foil plate.

[0032] In an exemplary embodiment, the sensing capacitor C2 of this application is selected as a parallel plate capacitor, which consists of two parallel conductor plates and an intermediate dielectric.

[0033] Since the medium between the copper foil and the ground is air, the capacitance C2 is C = (Σ·S) / d. Where Σ is the dielectric constant of air, d is the distance between the two parallel conductor plates, and S is the common area formed by the two parallel conductor plates; for the meter, S is the area of ​​the copper foil corresponding to the ground. The corresponding impedance between the copper foil and the ground... Where f is the operating frequency of the power grid, and the induced current in the copper foil is... U is the input voltage of the power grid on a single-phase meter.

[0034] Through the above embodiments, the induced current between the copper foil and the ground is divided into two paths. The first path of current flows to the live wire ground through the base and emitter of the two transistors Q1 and Q7, and the second path of current flows directly to the live wire ground through resistor R2.

[0035] Since the first path of current flowing to the live wire ground has multiple paths back to the ground, including entering from the PCB via the neutral wire and returning to the live wire ground via the space coupling capacitor C1, the first path of induced current I is amplified by transistor Q7 (Q7 operates in the amplification region), then amplified by transistor Q1 (Q1 operates in the saturation region). Finally, the MCU inside the energy meter detects the level signal at the collector of transistor Q1 to determine whether the live and neutral wires are reversed.

[0036] Specifically, if the level signal detected by the MCU is always high, it is determined that the live and neutral wires are reversed;

[0037] If the MCU detects a high or low level pulse signal, then the live and neutral wires are connected correctly.

[0038] In one possible implementation, the frequency of the high and low level pulse signals is 50Hz or 60Hz, corresponding to the output frequency of the State Grid, wherein the high level threshold is ≥0.7Vcc, the low level threshold is ≤0.3Vcc, and Vcc is the MCU power supply voltage.

[0039] In this embodiment, the threshold is defined proportionally rather than as a fixed voltage value, which can adapt to the logic level standards of different MCU models. For example:

[0040] When the MCU supply voltage Vcc = 3.3V, the high level threshold is ≥2.31V and the low level threshold is ≤0.99V, which is compatible with 3.3V logic levels (typically high level ≥2V and low level ≤0.8V).

[0041] When Vcc = 5V, the threshold is automatically adjusted to ≥3.5V and ≤1.5V to adapt to the 5V logic level standard and avoid logic misjudgment caused by voltage differences.

[0042] By synchronizing the frequency with the national power grid and using adaptive logic thresholds, the system achieves high efficiency, anti-interference capabilities, and cross-platform compatibility in signal processing, making it particularly suitable for power electronic equipment, smart sensors, and control systems that rely on the power grid frequency. The proportional level threshold design further enhances the circuit's adaptability to different supply voltages, reduces hardware design and debugging costs, and ensures the stability and reliability of the system.

[0043] In one possible implementation, both transistors Q1 and Q7 are NPN high-precision DC current gain transistors with a β value ranging from 20 to 450, where β is the ratio of collector current (Ic) to base current (Ib).

[0044] In common-emitter configuration, NPN transistors can achieve both voltage and current amplification. Stable amplification can be achieved by precisely setting the static operating point through a resistor network. By selecting transistors with different β values ​​or dynamically adjusting the bias, the design requirements of different energy meters can be met.

[0045] The above is a detailed description of the preferred embodiments of the present utility model. However, the present utility model is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present utility model. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A single-phase smart energy meter live / neutral wire reverse connection detection circuit, characterized in that, The components include a copper foil plate, transistors Q1 and Q7, resistors R1, R2, and R4, as well as sensing capacitors C1 and C2. One end of the copper foil plate is connected to the neutral line N through the inductive capacitor C2, and the other end is connected to the base of the transistor Q7 and connected to the live line L through the resistor R2. The collector of transistor Q7 is connected to a high level through resistor R4, and the emitter of transistor Q7 is connected to the base of transistor Q1. The collector of transistor Q1 is connected to the MCU of the single-phase smart energy meter and connected to a high level through resistor R1. The emitter of transistor Q1 is connected to the live wire L and connected to the neutral wire N through sensing capacitor C1.

2. The single-phase smart energy meter live / neutral wire reverse connection detection circuit according to claim 1, characterized in that, Both transistors Q1 and Q7 are NPN type high-precision DC current gain transistors with a β value range of 20-450.

3. The single-phase smart energy meter live / neutral wire reverse connection detection circuit according to claim 1, characterized in that, The MCU determines whether the live and neutral wires are reversed by detecting the voltage level change at the collector of transistor Q1. If the voltage level is consistently high, it indicates that the live and neutral wires are reversed. If it is a high or low level pulse signal, then the live and neutral wires are connected correctly.

4. The detection circuit according to claim 1, characterized in that, The copper foil plate has a rectangular structure with a length of 10–15 mm, a width of 2–3 mm, and a thickness of 35 μm. It is used to sense the AC potential difference between the live wire L and the neutral wire N.

5. The detection circuit according to claim 3, characterized in that, The frequency of the high and low level pulse signals is 50Hz or 60Hz, the high level threshold is ≥0.7Vcc, the low level threshold is ≤0.3Vcc, and Vcc is the MCU power supply voltage.

6. The detection circuit according to claim 1, characterized in that, The high level is provided by the internal DC power supply of the electricity meter, with a voltage range of 3.3V or 5V.

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