A single-phase electric energy meter and a power supply circuit thereof
By using rectifier and step-down circuits in the power supply circuit of a single-phase energy meter, and replacing the power transformer with switching transistors and inductors, the problems of high circuit cost and large size are solved, miniaturization of the circuit is achieved, and communication speed and anti-interference ability are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGDAO TOPSCOMM COMM
- Filing Date
- 2022-02-10
- Publication Date
- 2026-07-31
AI Technical Summary
In existing single-phase electricity meter power supply circuits, the power transformer is difficult to manufacture and has a large winding volume, resulting in high cost and hindering miniaturization design.
The circuit employs rectifier and step-down circuits, using switching transistors and inductors instead of power transformers to achieve mains power conversion and step-down through rectification and step-down. The circuit design uses components such as MOSFETs, inductors, capacitors, and diodes, combined with current limiting and magnetic isolation technologies to avoid the use of windings.
This invention enables the miniaturization of the power supply circuit for single-phase energy meters, reducing costs, increasing communication speed, and enhancing anti-interference capabilities.
Smart Images
Figure CN116633168B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electricity meter technology, and in particular to a single-phase electricity meter and its power supply circuit. Background Technology
[0002] Single-phase energy meters are used to measure the electricity consumption of loads and have the advantages of accurate measurement and small size.
[0003] Figure 1 This is a circuit diagram of a common single-phase energy meter power supply circuit in current technology, such as... Figure 1 As shown, after passing through the protection circuit, the mains power is converted into a voltage suitable for the microcontroller unit (MCU), metering chip, and energy meter communication interface via a power transformer. After rectification, it powers the energy meter. The MCU also interacts with the energy meter communication interface via an optocoupler isolation circuit. However, in practice, the transformer is difficult to manufacture, and the transformer windings are large, resulting in high circuit costs and preventing miniaturization.
[0004] Therefore, how to reduce the cost of the power supply circuit for single-phase energy meters and achieve miniaturized circuit design is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] The purpose of this application is to provide a single-phase energy meter and its power supply circuit, which reduces the cost of the power supply circuit of the single-phase energy meter and realizes the miniaturization design of the circuit.
[0006] To solve the above-mentioned technical problems, this application provides a power supply circuit for a single-phase energy meter, the circuit comprising:
[0007] Rectifier circuit, step-down circuit;
[0008] The rectifier circuit is connected to the protection circuit and is connected to the mains power supply.
[0009] The step-down circuit includes: a switching transistor, an inductor, a first diode, and a first capacitor;
[0010] The first terminal of the switching transistor is connected to the first terminal of the rectifier circuit as the first terminal of the buck circuit; the second terminal of the switching transistor is connected to the first terminal of the inductor and the cathode of the first diode; the second terminal of the inductor and the first terminal of the first capacitor together serve as the second terminal of the buck circuit and are connected to the first terminal of the MCU and the metering chip; the control terminal of the switching transistor is connected to the power supply; the anode of the first diode and the second terminal of the first capacitor together serve as the third terminal of the buck circuit and are connected to the second terminal of the MCU, the second terminal of the metering chip, and the second terminal of the rectifier circuit.
[0011] Preferably, the rectifier circuit includes:
[0012] Second diode and second capacitor;
[0013] The anode of the second diode serves as the third terminal of the rectifier circuit and is connected to the first terminal of the protection circuit. The cathode of the second diode and the first terminal of the second capacitor together serve as the first terminal of the rectifier circuit and are connected to the first terminal of the step-down circuit.
[0014] The second terminal of the second capacitor serves as the second terminal of the rectifier circuit, connecting to the second terminal of the protection circuit and the second terminal of the step-down circuit.
[0015] Preferred options also include:
[0016] Current limiting circuit;
[0017] The first terminal of the current limiting circuit is connected to the first terminal of the rectifier circuit; the second terminal of the current limiting circuit is connected to the second terminal of the rectifier circuit and the second terminal of the protection circuit.
[0018] Preferably, the current limiting circuit is a first resistor;
[0019] The first end of the first resistor serves as the first end of the current limiting circuit and is connected to the first end of the rectifier circuit; the second end of the first resistor serves as the second end of the current limiting circuit and is connected to the second end of the rectifier circuit and the second end of the protection circuit.
[0020] Preferably, the isolation circuit of the communication interface between the MCU and the energy meter is an isolation transformer, and the MCU is an MCU with a built-in magnetic isolation drive circuit.
[0021] Preferably, the switching transistor is a MOSFET.
[0022] Preferably, the power source is a power IC chip;
[0023] The first terminal of the power IC chip is connected to the control terminal of the switching transistor; the second terminal of the power IC chip is connected to the second terminal of the step-down circuit.
[0024] Preferably, it also includes: a third diode;
[0025] The anode of the third diode is connected to the second terminal of the step-down circuit, and the cathode of the third diode is connected to the power IC chip.
[0026] To solve the above-mentioned technical problems, this application also provides a single-phase energy meter, which includes the above-mentioned single-phase energy meter power supply circuit.
[0027] The single-phase energy meter power supply circuit provided in this application includes a rectifier circuit and a step-down circuit. The rectifier circuit is connected to a protection circuit and is connected to the mains power. The step-down circuit includes a switching transistor, an inductor, a first diode, and a first capacitor. The first terminal of the switching transistor serves as the first terminal of the step-down circuit and is connected to the first terminal of the rectifier circuit. The second terminal of the switching transistor is connected to the first terminal of the inductor and the cathode of the first diode. The second terminal of the inductor and the first terminal of the first capacitor together serve as the second terminal of the step-down circuit, connecting to the first terminal of the MCU and the metering chip. The control terminal of the switching transistor is connected to the power supply. The anode of the first diode and the second terminal of the first capacitor together serve as the third terminal of the step-down circuit, connecting to the second terminals of the MCU, the metering chip, and the rectifier circuit. Compared to current technologies that use a power transformer to step down the mains power, which is difficult to manufacture and has large windings, hindering miniaturization, this technical solution uses a switching transistor and an inductor to step down the mains power, eliminating the need for windings in the single-phase energy meter power supply circuit and achieving miniaturization.
[0028] Furthermore, the single-phase energy meter provided in this application includes the aforementioned single-phase energy meter power supply circuit, and has the same effect as above. Attached Figure Description
[0029] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0030] Figure 1 This is a circuit diagram of a common power supply circuit for single-phase energy meters in current technology.
[0031] Figure 2 A circuit diagram of a power supply circuit for a single-phase energy meter provided in an embodiment of this application. Detailed Implementation
[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.
[0033] The core of this application is to provide a single-phase energy meter and its power supply circuit, which reduces the cost of the power supply circuit of the single-phase energy meter and realizes the miniaturization design of the circuit.
[0034] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0035] Figure 2 A circuit diagram of a single-phase energy meter power supply circuit provided in this application embodiment is shown below. Figure 2 As shown, the circuit includes:
[0036] Rectifier circuit 1, step-down circuit 2;
[0037] Rectifier circuit 1 is connected to protection circuit 3 and connected to mains power;
[0038] The step-down circuit 2 includes: a switching transistor Q, an inductor L, a first diode VD1, and a first capacitor C1;
[0039] The first terminal of the switching transistor Q is connected to the first terminal of the rectifier circuit 1 as the first terminal of the step-down circuit 2; the second terminal of the switching transistor Q is connected to the first terminal of the inductor L and the cathode of the first diode VD1; the second terminal of the inductor L and the first terminal of the first capacitor C1 together serve as the second terminal of the step-down circuit 2 and are connected to the first terminal of the MCU and the metering chip 4; the control terminal of the switching transistor Q is connected to the power supply; the anode of the first diode VD1 and the second terminal of the first capacitor C1 together serve as the third terminal of the step-down circuit 2 and are connected to the second terminal of the MCU, the metering chip 4 and the rectifier circuit 1.
[0040] In practical implementation, given the existence of some unstable factors in the power supply circuit, a protection circuit 3 will be added to prevent such unstable factors from affecting the circuit performance. For example, it can provide overcurrent protection, overvoltage protection, overheat protection, no-load protection, and short-circuit protection. It can automatically disconnect the load when the mains power is unstable to protect the electrical equipment.
[0041] To convert AC mains power into DC power, the mains power passes through protection circuit 3 and then rectifier circuit 1. Currently, commonly used rectifier circuits 1 include half-wave rectification, full-wave rectification, and bridge rectification. Half-wave rectification utilizes the unidirectional conduction characteristic of diodes. With a standard sine wave input, it outputs the positive half of the sine wave, discarding the negative half, thus converting AC to DC. It can be seen that half-wave rectification achieves rectification by discarding half of the AC, resulting in lower current utilization. Full-wave rectification and bridge rectification, on the other hand, can output the complete sine wave, achieving twice the current utilization of half-wave rectification.
[0042] In this embodiment, the mains power is rectified and stepped down to power the MCU and metering chip 4. The MCU communicates with the energy meter via its communication interface 5. The MCU also handles the LCD display, while the metering chip calculates and stores electricity consumption. In current technology, the connection between the MCU and the energy meter's communication interface 5 typically uses optocoupler isolation. Optocoupler isolation uses an optocoupler for isolation. The structure of an optocoupler is equivalent to encapsulating a light-emitting diode and a phototransistor together. The optocoupler isolation circuit prevents a direct electrical connection between the isolated circuit parts, primarily preventing interference caused by electrical connections, especially between low-voltage control circuits and external high-voltage circuits. Although optocoupler isolation has strong anti-interference capabilities, its transmission delay is relatively large, slowing down the communication rate between the MCU and the energy meter's communication interface 5. In this embodiment, the energy meter's communication interface is an RS485 communication interface.
[0043] In this embodiment, when the power output is high, the switch Q is turned on, and the first diode VD1 is reverse-biased and cut off. The rectified mains power supplies the MCU and metering chip 4 through the inductor L. At this time, the current in the inductor L gradually increases, and a self-induced electromotive force (EMF) with the first terminal positive and the second terminal negative is generated across the inductor L, hindering the current increase. The inductor L stores the electrical energy as magnetic energy. After a period of time, the power output is low, and the switch Q is turned off. However, since the current in the inductor L cannot change abruptly, a self-induced EMF with the first terminal negative and the second terminal positive is generated across the inductor L, hindering the current decrease. This causes the first diode VD1 to turn on, and the current in the inductor L re-circulates through the first diode VD1, gradually decreasing in value. The magnetic energy stored in the inductor L is converted into electrical energy and released to supply the MCU and metering chip 4. After a period of time, the power output becomes high again, and the above steps are repeated. Thus, the step-down circuit 2 achieves the step-down of the mains power. The first capacitor C1 reduces the output voltage ripple and acts as a filter.
[0044] The single-phase energy meter power supply circuit provided in this application includes a rectifier circuit and a step-down circuit. The rectifier circuit is connected to a protection circuit and is connected to mains power. The step-down circuit includes a switching transistor, an inductor, a first diode, and a first capacitor. The first terminal of the switching transistor serves as the first terminal of the step-down circuit and is connected to the first terminal of the rectifier circuit. The second terminal of the switching transistor is connected to the first terminal of the inductor and the cathode of the first diode. The second terminal of the inductor and the first terminal of the first capacitor together serve as the second terminal of the step-down circuit, connected to the first terminal of the MCU and the metering chip. The control terminal of the switching transistor is connected to the power supply. The anode of the first diode and the second terminal of the first capacitor together serve as the third terminal of the step-down circuit, connected to the second terminals of the MCU, the metering chip, and the rectifier circuit. Compared to the current technology that uses a power transformer to step down the mains power, which is difficult to manufacture and has large windings, hindering miniaturization design, this technical solution uses a switching transistor and an inductor to step down the mains power, eliminating the need for windings in the single-phase energy meter power supply circuit and achieving miniaturization.
[0045] The above embodiments provide various rectification methods. Based on the above embodiments, in this embodiment, the rectifier circuit 1 includes:
[0046] Second diode VD2 and second capacitor C2;
[0047] The anode of the second diode VD2 serves as the third terminal of the rectifier circuit 1 and is connected to the first terminal of the protection circuit 3. The cathode of the second diode VD2 and the first terminal of the second capacitor C2 together serve as the first terminal of the rectifier circuit 1 and are connected to the first terminal of the step-down circuit 2.
[0048] The second terminal of the second capacitor C2 serves as the second terminal of the rectifier circuit 1, connecting to the second terminal of the protection circuit 3 and the second terminal of the step-down circuit 2.
[0049] In this embodiment, rectifier circuit 1 selects half-wave rectification, achieving rectification based on the unidirectional conductivity of the second diode VD2. It can be understood that half-wave rectification means there is current output during half a cycle of the mains power supply, and no current during the other half. The mains power frequency is typically 50Hz, and after half-wave rectification, the output is still a 50Hz pulsating current. However, if full-wave rectification or bridge rectification is used, both the positive and negative half-cycles of the mains power supply are utilized, and the output pulsating current transforms the negative half-cycle of the mains power supply into a positive half-cycle, effectively turning the 50Hz mains current into a 100Hz pulsating current.
[0050] The single-phase power meter power supply circuit provided in this application embodiment uses diodes and capacitors to perform half-wave rectification of the mains power, which can reduce the voltage stress on subsequent inductors and other components, and also provide greater margin for front-end lightning surge protection.
[0051] In practical implementation, the current of the rectified mains power is still enormous. To avoid damage to circuit components due to excessive current, this embodiment further includes, based on the above embodiments:
[0052] Current limiting circuit;
[0053] The first terminal of the current limiting circuit is connected to the first terminal of the rectifier circuit 1; the second terminal of the current limiting circuit is connected to the second terminal of the rectifier circuit 1 and the second terminal of the protection circuit 3.
[0054] The single-phase energy meter power supply circuit provided in this application embodiment avoids damage to circuit components due to excessive current by adding a current limiting circuit.
[0055] Based on the above embodiments, this embodiment provides a specific current limiting circuit, in which the current limiting circuit is a first resistor R;
[0056] The first end of the first resistor R is connected to the first end of the rectifier circuit 1 as the first end of the current limiting circuit; the second end of the first resistor R is connected to the second end of the rectifier circuit 1 and the second end of the protection circuit 3 as the second end of the current limiting circuit.
[0057] In specific implementations, the current limiting circuit may also include devices such as Zener diodes and transistors. The single-phase energy meter power supply circuit provided in this application embodiment uses a resistor as a shunt device to limit the current.
[0058] In current technology, the connection between the communication interface 5 of the MCU and the energy meter is usually an optocoupler isolation circuit. However, the transmission delay of the optocoupler is relatively large, which slows down the communication rate between the communication interface 5 of the MCU and the energy meter.
[0059] In order to improve the communication rate of the communication interface 5 between the MCU and the energy meter, based on the above embodiments, in this embodiment, the isolation circuit of the communication interface 5 between the MCU and the energy meter is an isolation transformer 6, and the MCU is an MCU with a built-in magnetic isolation drive circuit.
[0060] like Figure 2 As shown, the MCU is connected to the bridge rectifier circuit 1 in the communication interface 5 of the energy meter through the isolation transformer 6.
[0061] Magnetic isolation communication primarily achieves energy and information transmission by altering the voltage or current of the primary or secondary coils, causing a change in the magnetic field within the core. This change induces a corresponding voltage or current change on the other side of the isolation circuit. In this embodiment, the MCU achieves physical isolation from the communication interface 5 through its built-in magnetic isolation drive circuit and isolation transformer 6, providing a communication rate up to 10 times higher than that of optocoupler isolation.
[0062] The single-phase energy meter power supply circuit provided in this application embodiment uses magnetic isolation technology to replace the optocoupler isolation technology in the current technology, realizes communication between the MCU and the energy meter communication interface, improves the communication speed, and enhances the high temperature resistance.
[0063] In the above embodiments, the switching transistor Q can be a transistor or a MOSFET.
[0064] In this embodiment, the switching transistor Q is a MOS transistor.
[0065] A transistor is a current-controlled device, controlling the output current by controlling the base current. Therefore, there is always a certain current at the base, resulting in a low input resistance for transistors. A MOSFET, on the other hand, is a voltage-controlled device. Its output current depends on the voltage between the gate and source, and the gate draws virtually no current. Therefore, a MOSFET has a very high input resistance.
[0066] In a transistor, both majority and minority carriers participate in conduction, while in a MOSFET, only majority carriers participate in conduction. Since the concentration of minority carriers is greatly affected by factors such as temperature and radiation, MOSFETs have better temperature stability, stronger radiation resistance, and lower noise figure than transistors.
[0067] The single-phase energy meter power supply circuit provided in this application embodiment selects a MOSFET as the switching transistor, making full use of the advantages of MOSFETs such as high input resistance, low noise, low power consumption, no secondary breakdown phenomenon, wide safe operating area, and low susceptibility to temperature and radiation.
[0068] Based on the above embodiments, in this embodiment, the power supply is a power IC chip;
[0069] The first terminal of the power IC chip is connected to the control terminal of the switching transistor Q; the second terminal of the power IC chip is connected to the second terminal of the step-down circuit 2.
[0070] The single-phase energy meter power supply circuit provided in this application embodiment has a power IC chip responsible for converting, distributing, detecting, and managing electrical energy. The power IC chip controls the switching transistor to turn on and off based on the voltage at the second terminal of the step-down circuit.
[0071] In order to prevent the current passing through the power IC chip from flowing directly into the MCU and metering chip 4, based on the above embodiment, this embodiment also includes: a third diode VD3;
[0072] The anode of the third diode VD3 is connected to the second terminal of the step-down circuit 2, and the cathode of the third diode VD3 is connected to the power IC chip.
[0073] The single-phase energy meter power supply circuit provided in this application embodiment utilizes the unidirectional conductivity of diodes and adds a third diode to prevent the current passing through the power IC chip from flowing back into the MCU and metering chip.
[0074] Finally, this application embodiment also provides a single-phase energy meter, which, in addition to devices such as a display screen, also includes the aforementioned single-phase energy meter power supply circuit.
[0075] The single-phase energy meter provided in this application includes the aforementioned power supply circuit, which comprises a rectifier circuit and a step-down circuit. The rectifier circuit is connected to a protection circuit and is connected to mains power. The step-down circuit includes a switching transistor, an inductor, a first diode, and a first capacitor. The first terminal of the switching transistor serves as the first terminal of the step-down circuit and is connected to the first terminal of the rectifier circuit. The second terminal of the switching transistor is connected to the first terminal of the inductor and the cathode of the first diode. The second terminal of the inductor and the first terminal of the first capacitor together serve as the second terminal of the step-down circuit, connected to the first terminal of the MCU and the metering chip. The control terminal of the switching transistor is connected to the power supply. The anode of the first diode and the second terminal of the first capacitor together serve as the third terminal of the step-down circuit, connected to the second terminal of the MCU, the second terminal of the metering chip, and the second terminal of the rectifier circuit. Compared to the current technology that uses a power transformer to step down the mains power, which is difficult to manufacture and has large windings, hindering miniaturization design, this technical solution uses a switching transistor and an inductor to step down the mains power, eliminating the need for windings in the single-phase energy meter power supply circuit and achieving miniaturization.
[0076] The single-phase energy meter and its power supply circuit provided in this application have been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.
[0077] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
Claims
1. A single-phase electric energy meter power supply circuit, characterized by comprising: include: Rectifier circuit, step-down circuit; MCU and metering chip, RS485 communication interface; The rectifier circuit is connected to the protection circuit and is connected to the mains power supply. The step-down circuit includes: a switching transistor, an inductor, a first diode, and a first capacitor; The first terminal of the switching transistor is connected to the first terminal of the buck circuit and the first terminal of the rectifier circuit; the second terminal of the switching transistor is connected to the first terminal of the inductor and the cathode of the first diode; the second terminal of the inductor and the first terminal of the first capacitor together serve as the second terminal of the buck circuit, connected to the first terminal of the MCU and the metering chip; the control terminal of the switching transistor is connected to the power supply; the anode of the first diode and the second terminal of the first capacitor together serve as the third terminal of the buck circuit, connected to the second terminal of the MCU, the second terminal of the metering chip, and the second terminal of the rectifier circuit; The rectifier circuit includes: Second diode and second capacitor; The anode of the second diode serves as the third terminal of the rectifier circuit and is connected to the first terminal of the protection circuit. The cathode of the second diode and the first terminal of the second capacitor together serve as the first terminal of the rectifier circuit and are connected to the first terminal of the step-down circuit. The second terminal of the second capacitor serves as the second terminal of the rectifier circuit, connecting to the second terminal of the protection circuit and the second terminal of the step-down circuit. The isolation circuit of the communication interface between the MCU and the energy meter is an isolation transformer, and the MCU is an MCU with a built-in magnetic isolation drive circuit. The MCU is connected to the bridge rectifier circuit in the communication interface of the energy meter through an isolation transformer; the MCU achieves physical isolation from the RS485 communication interface through a built-in magnetic isolation drive circuit and an isolation transformer.
2. The single-phase electric energy meter power supply circuit according to claim 1, characterized in that, Also includes: Current limiting circuit; The first terminal of the current limiting circuit is connected to the first terminal of the rectifier circuit; the second terminal of the current limiting circuit is connected to the second terminal of the rectifier circuit and the second terminal of the protection circuit.
3. The single-phase electric energy meter power supply circuit according to claim 2, characterized in that, The current-limiting circuit is a first resistor; The first end of the first resistor serves as the first end of the current limiting circuit and is connected to the first end of the rectifier circuit; the second end of the first resistor serves as the second end of the current limiting circuit and is connected to the second end of the rectifier circuit and the second end of the protection circuit.
4. The single-phase electric energy meter power supply circuit according to any one of claims 1 to 3, characterized in that, The switching transistor is a MOSFET.
5. The single phase electric energy meter supply circuit according to claim 1, characterized in that, The power source is a power IC chip; The first terminal of the power IC chip is connected to the control terminal of the switching transistor; the second terminal of the power IC chip is connected to the second terminal of the step-down circuit.
6. The single-phase electric energy meter power supply circuit according to claim 5, characterized in that, Also includes: Third diode; The anode of the third diode is connected to the second terminal of the step-down circuit, and the cathode of the third diode is connected to the power IC chip.
7. A single phase electricity meter, characterised in that, It includes the power supply circuit for a single-phase energy meter as described in any one of claims 1 to 6.