Current-limiting protection circuit with optocoupler isolation based on intelligent electric meter

Abstract

The utility model relates to a current-limiting protection circuit with optocoupler isolation based on an intelligent electric meter. The current-limiting protection circuit comprises an integrated circuit UQ1 and divider resistors RQ1 and RQ2, in the integrated circuit UQ1, a pin 5 is connected with an input voltage VMAIN +; an EN pin 4 is connected to an input voltage VMAIN + through a divider resistor RQ1; the pin 2 is grounded; a pin 3 is divided into two paths, one path is grounded through a divider resistor RQ4, and the other path is connected with SPM + 12V through series divider resistors RQ5 and RQ7; a bootstrap capacitor CQ5 is connected between the pin 1 and the pin 6; a pin 6 is connected with SPM + 12V through an inductor LQ1, and an EN pin 4 is grounded through a divider resistor RQ2 and a filter capacitor CQ4 which are connected in parallel.

Description

Technical Field

[0001] The utility model belongs to the field of smart electric meters, and in particular relates to a current limiting protection circuit with optical coupling isolation based on smart electric meters. Background Art

[0002] In smart meter technology, the main function of the current limiting protection circuit is to protect the subsequent circuit, limit the current output of the back-end load, and prevent the subsequent load demand from increasing sharply and exceeding the previous power supply capacity, thereby causing the electric energy meter or other related equipment to appear overload, overheating or even damage and other abnormal conditions.

[0003] In the field of smart meters, optimizing the design and performance of current limiting protection circuits is extremely important for ensuring the accuracy of electricity metering, extending the service life of equipment, and reducing operation and maintenance costs. At present, the current limiting protection circuit is mainly: 1. Use the current sampling unit for receiving, and the output end is connected to the fast response unit. This method can quickly control the current flowing through. However, this method has the disadvantages of poor reliability and difficulty in maintenance; 2. The negative bias signal obtained after the initial signal is amplified and processed is loaded to the anode of the photoelectric sensor to achieve the purpose of reducing the current. However, this method has problems such as high power consumption and susceptibility to interference.

[0004] A current limiting protection circuit with optocoupler isolation control is proposed here, which has the advantages of simple control, high control accuracy and low cost. Utility Model Content

[0005] The technical problem to be solved by the utility model is generally to provide a current limiting protection circuit with optical coupling isolation based on a smart electric meter.

[0006] In order to solve the above problems, the technical solution adopted by the utility model is:

[0007] A current limiting protection circuit with optocoupler isolation based on a smart meter, comprising an integrated circuit UQ1, and voltage dividing resistors RQ1 and RQ2;

[0008] In the integrated circuit UQ1, pin 5 is connected to the input voltage VMAIN+; EN pin 4 is connected to the input voltage VMAIN+ through the voltage divider resistor RQ1; pin 2 is grounded; pin 3 is divided into two paths, one is grounded through the voltage divider resistor RQ4, and the other is connected to SPM+12V through the series voltage divider resistors RQ5 and RQ7; bootstrap capacitor CQ5 is connected between pins 1 and 6; pin 6 is connected to SPM+12V after passing through the inductor LQ1,

[0009] EN pin 4 is grounded through a parallel voltage divider resistor RQ2 and a filter capacitor CQ4.

[0010] As a further improvement of the above technical solution:

[0011] A filter unit is provided between the input voltage VMAIN+ and the pin 5 of the integrated circuit UQ1;

[0012] The filter unit includes filter capacitors CQ1, CQ2, and CQ3 connected in parallel between the pin 5 and the ground terminal;

[0013] Filter capacitors CQ4, CQ6, CQ7, and CQ8 are connected in parallel between the inductor LQ1 and the SPM+12V terminal.

[0014] The SPM+12V terminal is divided into three paths, the first path is grounded through capacitor CN25, the second path is electrically connected to pin 5 of integrated circuit UN2, and the third path is connected to pin 1 of integrated circuit UN2 through voltage divider resistor RN39;

[0015] Pin 4 of IC UN2 is grounded through resistor RN34;

[0016] Pin 3 is grounded, pin 6 is grounded through capacitor CN24, pin 2 is grounded through parallel capacitor CN22 and voltage zener diode EN7, pin 2 is connected to M+12V; M+12V is connected to the load;

[0017] Pin 1 is connected to the optocoupler DN1 through the voltage divider resistor RN41; the input end of the optocoupler DN1 is connected to the MCU through the network Meter-Module_SET.

[0018] The circuit also includes an integrated circuit UQ2;

[0019] Pin 2 of integrated circuit UQ2 is grounded, pin 3 is connected to voltage 5V0 through parallel filter capacitors CQ9 and CQ10, and pin 1 is connected to DVDD through parallel filter capacitors CQ11 and CQ12.

[0020] Specifically, it involves a current limiting protection circuit with optocoupler isolation. Its essence is that the current limiting protection circuit is a key circuit design specially used to prevent current overload. A specific resistance value is configured between the 4th pin of the integrated circuit UN2 and the ground to set a maximum allowable current threshold. When the load demand of the subsequent circuit increases, when the current exceeds the preset threshold, the current limiting protection circuit will respond immediately, by cutting off the current flow path, effectively preventing the current from further increasing, thereby protecting the subsequent circuit from overcurrent damage. Ensure the safety of the system, extend the life of the equipment, and also maintain the stability of the overall circuit operation.

[0021] The utility model has the following advantages:

[0022] 1. High flexibility: The current limit point is adjustable and can be flexibly set according to different load requirements to ensure that the meter can work normally under various working conditions without affecting the metering accuracy.

[0023] 2 Optocoupler DN1 can electrically isolate the MCU from the current limiting chip through the photoelectric transmission characteristics of the optocoupler, effectively preventing interference that may be caused by high voltage, surge or ground loop, and ensuring the stability and safety of the MCU and its control system.

[0024] 3. Through precise current limiting control, it can effectively prevent current overload caused by abnormal downstream load, thereby protecting the power supply system and microprocessor (MCU) and other key components inside the meter from damage.

[0025] 4 Enhanced system stability: Optocoupler isolation combined with current limiting protection function can respond quickly to various abnormal situations, maintain stable system operation, and reduce maintenance frequency and cost.

[0026] The utility model has the advantages of reasonable design, low cost, firmness and durability, safety and reliability, simple operation, time-saving, labor-saving, money-saving, compact structure and convenient use. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a circuit diagram of the utility model.

[0028] Figure 2 It is a circuit diagram of the integrated circuit UQ2 part of the utility model.

[0029] Figure 3 It is a circuit diagram of the integrated circuit UN2 part of the utility model. DETAILED DESCRIPTION

[0030] like Figure 1-3As shown, the current limiting protection circuit with optocoupler isolation based on the smart meter of this embodiment includes filter capacitors CQ1, CQ2, CQ3, CQ4, voltage divider resistors RQ1, RQ2, integrated circuit UQ1, CQ5 is a bootstrap capacitor, which increases the voltage at the negative end of the capacitor, and the positive end voltage remains at the original voltage difference at the negative end. The output voltage is determined by the ratio of resistors RQ4, RQ5, and RQ7. Inductor LQ1 plays multiple important roles such as filtering, energy storage, and voltage reduction. CQ6, CQ7, and CQ8 are output filter capacitors. The input voltage VMAIN+ enters the integrated circuit UQ1 after filtering through CQ1, CQ2, and CQ3. VMAIN+ is input to the EN pin of the integrated circuit UQ1 after voltage division through RQ1 and RQ2. It is greater than the EN pin start-up voltage threshold, and the integrated circuit UQ1 starts to start. The SPM+12V power supply is output through filter capacitors CQ6, CQ7, and CQ8. The voltage 5V0 enters UQ2 after filtering through CQ9 and CQ10, and is stored and filtered through CQ11 and CQ12, and can output the voltage DVDD smoothly. The current limiting chip is configured through the external programming of resistor RN34 to limit the current size. When the subsequent load reaches or exceeds the set value, the pin connected to the MCU through the network Meter-Module_SET is set low, the optocoupler DN1 is turned on, and the voltage SPM+12V enters UN2 after being divided by resistors RN39 and RN41, and the current path is cut off in time and effectively to achieve the purpose of protecting the subsequent circuit. The soft start time of the current limiting chip is set by configuring the size of the CN24 capacitor, CN22 is used for filtering the chip output, and EN7 is used for energy storage in the subsequent circuit. Decoupling can also reduce ripple. The MCU controls the current limiting chip through the optocoupler DN1, and the isolation effect of the optocoupler DN1 realizes the function of protecting the MCU in the meter. Resistor RN28 can limit the current passing through the optocoupler.

[0031] This circuit limits the current output of the subsequent circuit to ensure that the current does not exceed the preset safety threshold. When the subsequent load increases, the circuit will immediately act to limit the current output to prevent the energy meter from abnormalities. In the energy meter, if the power system is overloaded, it may lead to reduced measurement accuracy, incorrect readings, or even complete failure. The current limiting protection circuit can ensure that the power output is always within a safe and stable range, thereby preventing the energy meter from entering an abnormal working state due to current overload, ensuring the accuracy of energy measurement and the durability of the equipment.

[0032] Optocoupler DN1 is used in the circuit to convert the control signal of the current limiting chip into photoelectric signals, realize electrical isolation and transmit the signal to the MCU, so as to accurately control the current limiting function and enhance the stability and safety of the system. The current limiting protection circuit prevents the overload of the subsequent circuit from causing a surge in current and damaging the previous power supply, thereby ensuring the stable and safe operation of the system. The current limiting protection circuit can accurately set the current limiting point by adjusting the resistance value of resistor RN34.

[0033] The present invention is fully described for a clearer disclosure, and the prior art will not be listed one by one.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it; although the utility model is described in detail with reference to the above embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features therein with equivalents; it is obvious for those skilled in the art to combine multiple technical solutions of the utility model. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the utility model.

Claims

1. A current limiting protection circuit with optocoupler isolation based on a smart meter, characterized in that: It includes integrated circuit UQ1, voltage dividing resistors RQ1 and RQ2; In the integrated circuit UQ1, pin 5 is connected to the input voltage VMAIN+; EN pin 4 is connected to the input voltage VMAIN+ through the voltage divider resistor RQ1; pin 2 is grounded; pin 3 is divided into two paths, One path is connected to ground through the voltage divider resistor RQ4, and the other path is connected to SPM+12V through the series voltage divider resistors RQ5 and RQ7; the bootstrap capacitor CQ5 is connected between pin 1 and pin 6; pin 6 is connected to SPM+12V through the inductor LQ1. EN pin 4 is grounded through a parallel voltage divider resistor RQ2 and a filter capacitor CQ4.

2. The current limiting protection circuit with optocoupler isolation based on a smart meter according to claim 1 is characterized in that: A filter unit is provided between the input voltage VMAIN+ and the pin 5 of the integrated circuit UQ1; The filter unit includes filter capacitors CQ1, CQ2, and CQ3 connected in parallel between the pin 5 and the ground terminal; Filter capacitors CQ4, CQ6, CQ7, and CQ8 are connected in parallel between the inductor LQ1 and the SPM+12V terminal.

3. The current limiting protection circuit with optocoupler isolation based on a smart meter according to claim 1 is characterized in that: The SPM+12V terminal is divided into three paths, the first path is grounded through capacitor CN25, the second path is electrically connected to pin 5 of integrated circuit UN2, and the third path is connected to pin 1 of integrated circuit UN2 through voltage divider resistor RN39; Pin 4 of IC UN2 is grounded through resistor RN34; Pin 3 is grounded, pin 6 is grounded through capacitor CN24, pin 2 is grounded through parallel capacitor CN22 and voltage zener diode EN7, pin 2 is connected to M+12V; M+12V is connected to the load; Pin 1 is connected to the optocoupler DN1 through the voltage divider resistor RN41; the input end of the optocoupler DN1 is connected to the MCU through the network Meter-Module_SET.

4. The current limiting protection circuit with optocoupler isolation based on a smart meter according to claim 3 is characterized in that: The circuit also includes an integrated circuit UQ2; Pin 2 of integrated circuit UQ2 is grounded, pin 3 is connected to voltage 5V0 through parallel filter capacitors CQ9 and CQ10, and pin 1 is connected to DVDD through parallel filter capacitors CQ11 and CQ12.

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