A new power supply circuit applied to a smart electric energy meter
By using the capacitive isolation chip U2 in the smart energy meter to provide power to the 485 chip, the problem of difficult power wiring is solved, the circuit is simplified and the safety is improved, the transformer size is reduced and the signals of the MCU and the 485 chip are isolated.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- YUBANG POWER INTELLIGENT EQUIP (JIAXING) CO LTD
- Filing Date
- 2025-06-09
- Publication Date
- 2026-06-26
AI Technical Summary
In smart energy meters, insufficient space for existing power wiring makes wiring difficult or even impossible, and the communication line between the 485 chip and the MCU chip requires optical isolation, which increases the design complexity.
A capacitive isolation chip U2 with built-in isolation DC-DC power supply is used to provide power to the 485 chip, reducing the number of transformer windings. The MCU and the 485 chip are connected through the isolation chip U2 to achieve electrical isolation.
It simplifies power wiring, reduces transformer size, improves circuit safety and reliability, and prevents 485 chip failures from affecting the MCU.
Smart Images
Figure CN224418690U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of power supply circuit technology for electricity meters, and specifically relates to a novel power supply circuit used in smart electricity meters. Background Technology
[0002] Currently, the power supply solutions used in single-phase smart meters are as follows: Figure 3 The transformer has three sets of windings. It takes in 220V AC power and outputs three sets of DC power through the three windings and rectifier circuit. The three sets of DC power are used by LDO power chips to power the MCU circuit, 485 circuit and metering circuit respectively.
[0003] In electricity meters, the 485 chip and metering chip need to communicate with the MCU chip. The communication lines between the chips are isolated by optocouplers to prevent a power supply failure in one circuit from affecting the other. In actual design, it was found that after considering interference between components during PCB layout, insufficient board space made power supply routing difficult or even impossible.
[0004] Therefore, further improvements will be made to address the aforementioned issues. Utility Model Content
[0005] The main purpose of this utility model is to provide a new power supply circuit for use in smart energy meters. The power required by the 485 chip U3 is provided by a capacitive isolation chip U2 with a built-in isolated DC-DC power chip. The input of the isolation chip U2 is the power supply of the MCU, and the output is the power supply of the 485. The transformer windings are reduced from three to two, which facilitates power wiring.
[0006] To achieve the above objectives, this utility model provides a novel power supply circuit for use in smart meters, comprising a microprocessor U1 (i.e., MCU), an isolation chip U2, and a 485 chip U3, wherein the isolation chip U2 is connected between the microprocessor U1 and the 485 chip U3, wherein:
[0007] Pins 1 and 7 of the isolation chip U2 are connected to the power supply terminal MVCC (5V power supply) of the microprocessor U1, and pins 2 and 8 of the isolation chip U2 are ground of the power supply terminal MVCC; the transmit pin (RS485RX) of the microprocessor MCU is electrically connected to pin 3 of the isolation chip U2, the control pin (RS485 RE / DE) of the microprocessor MCU is electrically connected to pin 4 of the isolation chip U2, and the receive pin (RS485 TX) of the microprocessor MCU is electrically connected to pin 6 of the isolation chip U2;
[0008] The isolation chip U2 outputs a power supply terminal V485 at pin 16, and the power supply terminal V485 is electrically connected to the power supply terminal (VCC) of the 485 chip U3. The receiver pin (RO) of the 485 chip is electrically connected to pin 14 of the isolation chip U2. The control pins ( / RE and DE) of the 485 chip are electrically connected to pin 13 of the isolation chip U2. The transmitter pin (DI) of the 485 chip is electrically connected to pin 11 of the isolation chip U2.
[0009] As a further preferred technical solution to the above technical solution, pins 9 and 15 of the isolation chip U2 are the ground of the power supply terminal V485.
[0010] As a further preferred technical solution to the above technical solution, the power supply MVCC is obtained from 220V AC power through a transformer and an LDO power chip.
[0011] As a further preferred embodiment of the above technical solution, a capacitor is connected between pins 15 and 16 of the isolation chip U2.
[0012] As a further preferred embodiment of the above technical solution, a capacitor is connected between pin 1 and pin 2 of the isolation chip U2. Attached Figure Description
[0013] Figure 1 This is the circuit diagram of this utility model.
[0014] Figure 2 This is a schematic diagram of the transformer power supply of this utility model.
[0015] Figure 3 This is a schematic diagram of an existing transformer power supply. Detailed Implementation
[0016] The following description is intended to disclose the present invention so that those skilled in the art can implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the present invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.
[0017] This utility model discloses a novel power supply circuit applied to smart energy meters. The specific embodiments of the utility model are further described below with reference to preferred embodiments.
[0018] In the embodiments of this utility model, those skilled in the art will note that the MCU, 485 chip, etc. involved in this utility model can be regarded as prior art.
[0019] Preferred embodiment.
[0020] like Figure 1-2 As shown, this utility model discloses a novel power supply circuit for use in smart meters, including a microprocessor U1 (i.e., MCU), an isolation chip U2, and a 485 chip U3. The isolation chip U2 is connected between the microprocessor U1 and the 485 chip U3, wherein:
[0021] Pins 1 and 7 of the isolation chip U2 are connected to the power supply terminal MVCC (5V power supply) of the microprocessor U1, and pins 2 and 8 of the isolation chip U2 are ground of the power supply terminal MVCC; the transmit pin (RS485RX) of the microprocessor MCU is electrically connected to pin 3 of the isolation chip U2, the control pin (RS485 RE / DE) of the microprocessor MCU is electrically connected to pin 4 of the isolation chip U2, and the receive pin (RS485 TX) of the microprocessor MCU is electrically connected to pin 6 of the isolation chip U2;
[0022] The isolation chip U2 outputs a power supply terminal V485 at pin 16, and the power supply terminal V485 is electrically connected to the power supply terminal (VCC) of the 485 chip U3. The receiver pin (RO) of the 485 chip is electrically connected to pin 14 of the isolation chip U2. The control pins ( / RE and DE) of the 485 chip are electrically connected to pin 13 of the isolation chip U2. The transmitter pin (DI) of the 485 chip is electrically connected to pin 11 of the isolation chip U2.
[0023] Specifically, pins 9 and 15 of the isolation chip U2 are the ground of the power supply V485.
[0024] More specifically, the MVCC power supply is supplied by 220V AC power through a transformer and an LDO power chip.
[0025] Furthermore, a capacitor is connected between pins 15 and 16 of the isolation chip U2.
[0026] Furthermore, a capacitor is connected between pin 1 and pin 2 of the isolation chip U2.
[0027] Regarding this utility model:
[0028] 1. Power generation
[0029] The isolation chip U2 inputs the 5V power supply MVCC of the MCU through pin 1. Through the internal DC-DC power chip, pin 16 outputs another 5V power supply V485 to provide power to the 485 chip.
[0030] 2. Electrical isolation
[0031] Since the input and output levels of the NSIP8842 chip are only related to the power supply voltage on each side, it provides electrical isolation, ensuring the safety and reliability of the circuit.
[0032] The beneficial effects of this utility model are as follows:
[0033] In practical applications, this circuit reduces the number of transformer windings, resulting in a corresponding reduction in the transformer's size. Previously, isolation required three optocoupler chips; now, only one capacitive coupler chip is needed, solving the problem of insufficient board space. Because the 485 power supply uses the isolated DC-DC power chip integrated into the isolation chip, the MCU power supply and the 485 power supply are separated, and the signals on both sides are isolated, preventing damage to the MCU from problems at the 485 chip end.
[0034] This invention uses the NSIP8842 capacitive coupling chip U2 for power conversion: one end of the chip uses the MCU's power supply, with pins on the same side connected to the required pins on the MCU. The other end of the chip outputs a 485 power supply, with pins on the same side connected to the required pins on the 485 terminal. The selected chip is itself an isolation chip, providing electrical isolation protection.
[0035] It is worth mentioning that the technical features of MCU, 485 chip and other technologies involved in this utility model patent application should be regarded as prior art. The specific structure, working principle and possible control method and spatial arrangement of these technical features can be adopted by conventional choices in the field and should not be regarded as the inventive point of this utility model patent. This utility model patent will not be further elaborated in detail.
[0036] For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.
Claims
1. A new power supply circuit applied to a smart meter, characterized in that, The system includes a microprocessor U1, an isolation chip U2, and a 485 chip U3, wherein the isolation chip U2 is connected between the microprocessor U1 and the 485 chip U3, and wherein: Pins 1 and 7 of the isolation chip U2 are connected to the power supply terminal MVCC of the microprocessor U1, and pins 2 and 8 of the isolation chip U2 are ground of the power supply terminal MVCC; the transmitting pin of the microprocessor U1 is electrically connected to pin 3 of the isolation chip U2, the control pin of the microprocessor U1 is electrically connected to pin 4 of the isolation chip U2, and the receiving pin of the microprocessor U1 is electrically connected to pin 6 of the isolation chip U2. The isolation chip U2 outputs a power supply terminal V485 at pin 16, and the power supply terminal V485 is electrically connected to the power supply terminal of the 485 chip U3. The receiving pin of the 485 chip is electrically connected to pin 14 of the isolation chip U2. The control pin of the 485 chip is electrically connected to pin 13 of the isolation chip U2. The transmitting pin of the 485 chip is electrically connected to pin 11 of the isolation chip U2.
2. The new power supply circuit applied to the smart meter of claim 1, wherein Pins 9 and 15 of the isolation chip U2 are the ground of the power supply V485.
3. A novel power supply circuit for use in a smart energy meter according to claim 1, characterized in that, The MVCC power supply is supplied by 220V AC power through a transformer and an LDO power chip.
4. A novel power supply circuit for use in a smart energy meter according to claim 2, characterized in that, A capacitor is connected between pins 15 and 16 of the isolation chip U2.
5. A novel power supply circuit for use in a smart energy meter according to claim 4, characterized in that, A capacitor is connected between pin 1 and pin 2 of the isolation chip U2.