Current transformer disconnection monitoring circuit

Abstract

The utility model relates to a disconnection monitoring circuit for a current transformer. The disconnection monitoring circuit comprises a sampling module, a digital isolation amplifier, an operational amplifier module, a temperature sensor and an optocoupler module, the input end of the sampling module is connected with the current transformer, the output end is connected with the digital isolation amplifier, the input end of the operational amplifier module is connected with the digital isolation amplifier, and the output end is connected with the single-chip microcomputer. The temperature sensor is arranged on the sampling module, the input end of the optocoupler module is connected with the temperature sensor, and the output end of the optocoupler module is connected with the single-chip microcomputer. Compared with the prior art, the device has the advantages of safety, stability, high detection precision and the like.

Description

Technical Field

[0001] This utility model relates to the field of low-voltage electrical circuits, and in particular to a current transformer open circuit monitoring circuit. Background Technology

[0002] The existing current transformer line monitoring circuit uses a resistor to step down the voltage, a diode to regulate the voltage, a capacitor to filter the voltage, connects to an LED, and then sends the signal to an optocoupler. After isolation by the optocoupler, the signal is transmitted to the MCU for processing. When the CT transformer experiences an abnormal power failure, the LED does not light up, the optocoupler does not conduct, and the output is high. The abnormal power failure of the CT transformer is determined by whether the LED lights up and the high or low level of the optocoupler output.

[0003] However, the existing method of judging abnormal power failure of current transformers by using LEDs and optocouplers can lead to overheating of the sampling resistor under high current conditions, resulting in excessively high resistor temperature and low detection accuracy. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology, such as overheating of the resistor and low detection accuracy under high current conditions, and to provide a current transformer disconnection monitoring circuit.

[0005] The objective of this utility model can be achieved through the following technical solutions:

[0006] A current transformer open circuit includes a sampling module, a digital isolation amplifier, an operational amplifier module, a temperature sensor, and an optocoupler module.

[0007] The input terminal of the sampling module is connected to a current transformer, and the output terminal is connected to a digital isolation amplifier. The input terminal of the operational amplifier module is connected to the digital isolation amplifier, and the output terminal is connected to a microcontroller. The temperature sensor is mounted on the sampling module, and the input terminal of the optocoupler module is connected to the temperature sensor, and the output terminal is connected to the microcontroller.

[0008] Preferably, the sampling module includes a sampling resistor Rs, the temperature sensor is adapted to monitor the temperature of the sampling resistor Rs, and the isolation amplifier is an AMC1200; the sampling resistor Rs is connected in parallel across the current transformer, one end of the sampling resistor Rs is connected to pin 2 of the digital isolation amplifier, and the other end is connected to pin 3 of the digital isolation amplifier.

[0009] Preferably, the sampling module further includes resistors R2 and R6, with one end of the sampling resistor Rs connected to the isolation amplifier via resistor R2 and the other end connected to the isolation amplifier via resistor R6.

[0010] Preferably, the sampling module further includes capacitors C2, C3, and C4. Capacitor C4 is connected in parallel across the sampling resistor Rs. One end of capacitor C2 is connected to pin 1 of the isolation amplifier, and the other end is grounded. One end of capacitor C3 is connected to pin 5 of the isolation amplifier, and the other end is grounded.

[0011] Preferably, the operational amplifier module includes a differential amplifier IC1, resistors R1, R3, R4, and R7;

[0012] One end of resistor R3 is connected to pin 6 of the isolation amplifier, and the other end is connected to the non-inverting input of differential amplifier IC1. One end of resistor R4 is connected to pin 7 of the isolation amplifier, and the other end is connected to the inverting input of differential amplifier IC1. One end of resistor R1 is connected to the non-inverting input of differential amplifier IC1, and the other end is grounded. One end of resistor R7 is connected to the inverting input of differential amplifier IC1, and the other end is connected to the output of differential amplifier IC1. The output of differential amplifier IC1 is connected to the microcontroller.

[0013] Preferably, the operational amplifier module further includes capacitor C1 and capacitor C5, wherein capacitor C1 is connected in parallel across resistor R1 and capacitor C5 is connected in parallel across resistor R7.

[0014] Preferably, the temperature sensor is model LM95071, and the optocoupler module includes optocoupler GO1, transistor T1, resistor R12, resistor R13, resistor R9 and resistor R11;

[0015] One end of the resistor R9 is connected to the light-emitting input terminal of the optocoupler GO1, and the other end is connected to the DC power supply VCC1. One end of the resistor R11 is connected to the emitter of the optocoupler GO1 and the microcontroller, and the other end is connected to the DC power supply VCC. The collector of the optocoupler GO1 is grounded.

[0016] Pin 1 of transistor T1 is connected to pin 2 of temperature sensor via resistor R12. Pin 3 of transistor T1 is grounded and connected to pin 2 of temperature sensor via resistor R13. Pin 2 of transistor T1 is connected to the light output terminal of optocoupler GO1.

[0017] Preferably, the temperature sensor is connected to a primary temperature reading module, which includes an optocoupler GO2, a resistor R5, and a resistor R8.

[0018] One end of the resistor R5 is connected to the DC power supply VCC1, and the other end is connected to the collector of the optocoupler GO2. The collector of the optocoupler GO2 is connected to pin 3 of the temperature sensor. The light emission output terminal and the emitter of the optocoupler GO2 are grounded respectively. The light emission input terminal of the optocoupler GO2 is connected to the microcontroller through the resistor R8.

[0019] Preferably, the temperature sensor is connected to a secondary temperature reading module, which includes an optocoupler GO3, a resistor R15, and a resistor R14.

[0020] One end of the resistor R15 is connected to the DC power supply VCC1, and the other end is connected to the collector of the optocoupler GO3. The collector of the optocoupler GO3 is connected to pin 1 of the temperature sensor. The light emission output terminal and the emitter of the optocoupler GO3 are grounded respectively. The light emission input terminal of the optocoupler GO3 is connected to the microcontroller through the resistor R14.

[0021] Preferably, the temperature sensor is also connected to a capacitor C6, one end of which is connected to pin 5 of the temperature sensor and the other end is connected to pin 4 of the temperature sensor.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) This scheme uses a digital isolation amplifier and an operational amplifier module to detect the current signal of the sampling module and transmits it to the microcontroller to detect whether the current transformer is disconnected. When current flows through the sampling module, the sampling module will generate a temperature change. At this time, the temperature sensor samples the temperature of the sampling module, and the microcontroller monitors whether the current transformer is disconnected by collecting the temperature parameters. By sampling the signal and temperature of the sampling resistor, the abnormal disconnection of the current transformer can be monitored more accurately in real time. Moreover, the use of redundant detection methods of both signal and temperature sampling can improve the stability and accuracy of the monitoring circuit. Attached Figure Description

[0024] Figure 1 A schematic diagram of the current transformer open circuit monitoring circuit provided by this utility model; Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the utility model product is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0029] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0030] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] Example 1

[0032] like Figure 1 As shown, this embodiment provides a current transformer open circuit monitoring circuit, including a sampling module, a digital isolation amplifier, an operational amplifier module, a temperature sensor, and an optocoupler module;

[0033] The input terminal of the sampling module is connected to a current transformer, and the output terminal is connected to a digital isolation amplifier. The input terminal of the operational amplifier module is connected to the digital isolation amplifier, and the output terminal is connected to a microcontroller. The temperature sensor is mounted on the sampling module, and the input terminal of the optocoupler module is connected to the temperature sensor, and the output terminal is connected to the microcontroller.

[0034] This solution uses a digital isolation amplifier and operational amplifier module to detect the current signal of the sampling module and transmits it to a microcontroller to detect whether the current transformer is disconnected. When current flows through the sampling module, the module will generate a temperature change. At this time, a temperature sensor samples the temperature of the sampling module, and the microcontroller uses the collected temperature parameters to monitor whether the current transformer is disconnected. By sampling the signal and temperature of the sampling resistor, abnormal disconnection of the current transformer can be more accurately monitored in real time. Furthermore, the use of redundant detection methods with both signal and temperature sampling can improve the stability and accuracy of the monitoring circuit.

[0035] In a preferred embodiment, the sampling module includes a sampling resistor Rs, the temperature sensor is adapted to monitor the temperature of the sampling resistor Rs, and the isolation amplifier is an AMC1200; the sampling resistor Rs is connected in parallel across the two ends of the current transformer, one end of the sampling resistor Rs is connected to pin 2 of the digital isolation amplifier, and the other end is connected to pin 3 of the digital isolation amplifier.

[0036] The sampling module also includes resistors R2 and R6. One end of the sampling resistor Rs is connected to the isolation amplifier through resistor R2, and the other end is connected to the isolation amplifier through resistor R6.

[0037] By setting a current-limiting resistor between the sampling module and the isolation amplifier, the voltage generated by the current transformer is limited to protect the safety of the subsequent circuits.

[0038] The sampling module also includes capacitors C2, C3, and C4. Capacitor C4 is connected in parallel across the sampling resistor Rs. One end of capacitor C2 is connected to pin 1 of the isolation amplifier, and the other end is grounded. One end of capacitor C3 is connected to pin 5 of the isolation amplifier, and the other end is grounded.

[0039] Specifically, the operational amplifier module includes differential amplifier IC1, resistors R1, R3, R4, and R7;

[0040] One end of resistor R3 is connected to pin 6 of the isolation amplifier, and the other end is connected to the non-inverting input of differential amplifier IC1. One end of resistor R4 is connected to pin 7 of the isolation amplifier, and the other end is connected to the inverting input of differential amplifier IC1. One end of resistor R1 is connected to the non-inverting input of differential amplifier IC1, and the other end is grounded. One end of resistor R7 is connected to the inverting input of differential amplifier IC1, and the other end is connected to the output of differential amplifier IC1. The output of differential amplifier IC1 is connected to the microcontroller.

[0041] Furthermore, the operational amplifier module also includes capacitors C1 and C5, wherein capacitor C1 is connected in parallel across resistor R1, and capacitor C5 is connected in parallel across resistor R7.

[0042] Specifically, the temperature sensor is model LM95071, and the optocoupler module includes optocoupler GO1, transistor T1, resistor R12, resistor R13, resistor R9 and resistor R11;

[0043] One end of the resistor R9 is connected to the light-emitting input terminal of the optocoupler GO1, and the other end is connected to the DC power supply VCC1. One end of the resistor R11 is connected to the emitter of the optocoupler GO1 and the microcontroller, and the other end is connected to the DC power supply VCC. The collector of the optocoupler GO1 is grounded.

[0044] Pin 1 of transistor T1 is connected to pin 2 of temperature sensor via resistor R12. Pin 3 of transistor T1 is grounded and connected to pin 2 of temperature sensor via resistor R13. Pin 2 of transistor T1 is connected to the light output terminal of optocoupler GO1.

[0045] Furthermore, the temperature sensor is connected to a primary temperature reading module, which includes an optocoupler GO2, a resistor R5, and a resistor R8.

[0046] One end of the resistor R5 is connected to the DC power supply VCC1, and the other end is connected to the collector of the optocoupler GO2. The collector of the optocoupler GO2 is connected to pin 3 of the temperature sensor. The light emission output terminal and the emitter of the optocoupler GO2 are grounded respectively. The light emission input terminal of the optocoupler GO2 is connected to the microcontroller through the resistor R8.

[0047] Furthermore, the temperature sensor is connected to a secondary temperature reading module, which includes an optocoupler GO3, a resistor R15, and a resistor R14.

[0048] One end of the resistor R15 is connected to the DC power supply VCC1, and the other end is connected to the collector of the optocoupler GO3. The collector of the optocoupler GO3 is connected to pin 1 of the temperature sensor. The light emission output terminal and the emitter of the optocoupler GO3 are grounded respectively. The light emission input terminal of the optocoupler GO3 is connected to the microcontroller through the resistor R14.

[0049] After optocoupler electrical isolation and signal transmission, the signal is connected to pin 1 (CS) and pin 3 (SC) of temperature sensor U2; this allows the temperature sensor U1 to be queried to read the temperature.

[0050] Specifically, the temperature sensor is also connected to a capacitor C6, one end of which is connected to pin 5 of the temperature sensor and the other end is connected to pin 4 of the temperature sensor.

[0051] Specifically, such as Figure 1As shown, Rs is the sampling resistor, used for signal sampling; R2 and R6 are current-limiting resistors, used to limit the high voltage generated by the CT power supply to protect the subsequent circuitry; C2, C3, and C4 are capacitors, used for input level filtering and energy storage conditioning; U1 is a digital isolation amplifier AMC1200, used to obtain the voltage difference across the sampling resistor Rs and for circuit isolation; R3 and R4 are resistors, used to limit current and isolate the preceding and following stages of the circuit; C1 and C5 are capacitors, used for frequency compensation; R1 is a resistor used for pull-down; R7 is a resistor used in operational amplifiers to adjust the amplification factor; IC1 is a differential amplifier used for subtraction and signal processing.

[0052] C6 is a capacitor, used for filtering; U2 is a temperature sensor LM95071, used for temperature detection; R5, R9, R10, and R11 are resistors, used for pull-up; R8, R12, R13, and R14 are resistors, used to isolate the circuit before and after the current stage; T1 is a transistor, used for current amplification; GO1, GO2, and GO3 are optocouplers, used for electrical isolation and signal transmission; CT+, CT-, MCU_GPIO2, and MCU_GPIO3 represent input signals; MCU_GPIO1 and MCU_GPIO4 represent output signals.

[0053] When the CT is powered, the current is limited by resistors R2 and R6 and filtered by capacitor C4 before being sent to digital isolation amplifier U1. Digital isolation amplifier U1 obtains the voltage difference across the sampling resistor Rs and transmits it to the subsequent operational amplifier circuit after isolation by digital isolation amplifier U1. The subtractor composed of operational amplifier IC1, resistors R1, R3, R4, R7 and capacitors C1 and C5 calculates the voltage difference across the sampling resistor Rs. Finally, the output terminal MCU_GPIO4 is connected to the MCU, which processes the data to detect whether the CT power supply is open and the voltage level.

[0054] Because the sampling resistor Rs has a low resistance, it generates heat and temperature changes when the CT power supply produces a high voltage. This temperature change is collected by the temperature sensor U2 and transmitted from pin 2 (SO) to pin 1 (base) of transistor T1. At this time, transistor T1 conducts, and the current starts from VCC1 and successfully drives optocoupler GO1, flowing to pin 2 (collector) of transistor T1, then to pin 3 (emitter) of transistor T1, and finally to ground GND1. After electrical isolation and signal transmission through the optocoupler, the signal is connected to the MCU via the output terminal MCU_GPIO1. The MCU processes the signal and reads the temperature parameters to achieve the purpose of CT power supply detection.

[0055] Temperature sensor U2 has an SPI interface. The MCU is connected to optocouplers GO2 and GO3 through input terminals MCU_GPIO2 and MCU_GPIO3. After electrical isolation and signal transmission through the optocouplers, the signal is connected to pin 1 (CS) and pin 3 (SC) of temperature sensor U2 to query temperature sensor U1 and read the temperature.

[0056] This process verifies the sampling data of the sampling resistor Rs signal and temperature and establishes a functional relationship between the signal and temperature, thereby achieving the goals of high efficiency, accuracy and stability in CT power supply detection.

[0057] The preferred embodiments of this utility model have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this utility model through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A current transformer open circuit for monitoring circuitry, characterized in that, It includes a sampling module, a digital isolation amplifier, an operational amplifier module, a temperature sensor, and an optocoupler module; The input terminal of the sampling module is connected to a current transformer, and the output terminal is connected to a digital isolation amplifier. The input terminal of the operational amplifier module is connected to the digital isolation amplifier, and the output terminal is connected to a microcontroller. The temperature sensor is mounted on the sampling module, and the input terminal of the optocoupler module is connected to the temperature sensor, and the output terminal is connected to the microcontroller.

2. The current transformer open circuit according to claim 1, characterized in that, The sampling module includes a sampling resistor Rs, the temperature sensor is adapted to monitor the temperature of the sampling resistor Rs, and the isolation amplifier is an AMC1200. The sampling resistor Rs is connected in parallel across the two ends of the current transformer, one end of the sampling resistor Rs is connected to pin 2 of the digital isolation amplifier, and the other end is connected to pin 3 of the digital isolation amplifier.

3. The current transformer open circuit according to claim 2, characterized in that, The sampling module also includes resistors R2 and R6. One end of the sampling resistor Rs is connected to the isolation amplifier through resistor R2, and the other end is connected to the isolation amplifier through resistor R6.

4. The current transformer open circuit monitoring circuit according to claim 2, characterized in that, The sampling module also includes capacitors C2, C3, and C4. Capacitor C4 is connected in parallel across the sampling resistor Rs. One end of capacitor C2 is connected to pin 1 of the isolation amplifier, and the other end is grounded. One end of capacitor C3 is connected to pin 5 of the isolation amplifier, and the other end is grounded.

5. A current transformer open circuit monitoring circuit according to claim 1, characterized in that, The operational amplifier module includes a differential amplifier IC1, resistors R1, R3, R4, and R7; One end of resistor R3 is connected to pin 6 of the isolation amplifier, and the other end is connected to the non-inverting input of differential amplifier IC1. One end of resistor R4 is connected to pin 7 of the isolation amplifier, and the other end is connected to the inverting input of differential amplifier IC1. One end of resistor R1 is connected to the non-inverting input of differential amplifier IC1, and the other end is grounded. One end of resistor R7 is connected to the inverting input of differential amplifier IC1, and the other end is connected to the output of differential amplifier IC1. The output of differential amplifier IC1 is connected to the microcontroller.

6. A current transformer open circuit monitoring circuit according to claim 5, characterized in that, The operational amplifier module also includes capacitors C1 and C5. Capacitor C1 is connected in parallel across resistor R1, and capacitor C5 is connected in parallel across resistor R7.

7. The current transformer open circuit according to claim 1, characterized in that, The temperature sensor is model LM95071, and the optocoupler module includes optocoupler GO1, transistor T1, resistor R12, resistor R13, resistor R9 and resistor R11. One end of the resistor R9 is connected to the light-emitting input terminal of the optocoupler GO1, and the other end is connected to the DC power supply VCC1. One end of the resistor R11 is connected to the emitter of the optocoupler GO1 and the microcontroller, and the other end is connected to the DC power supply VCC. The collector of the optocoupler GO1 is grounded. Pin 1 of transistor T1 is connected to pin 2 of temperature sensor via resistor R12. Pin 3 of transistor T1 is grounded and connected to pin 2 of temperature sensor via resistor R13. Pin 2 of transistor T1 is connected to the light output terminal of optocoupler GO1.

8. A current transformer open circuit monitoring circuit according to claim 7, characterized in that, The temperature sensor is connected to a primary temperature reading module, which includes an optocoupler GO2, a resistor R5, and a resistor R8. One end of the resistor R5 is connected to the DC power supply VCC1, and the other end is connected to the collector of the optocoupler GO2. The collector of the optocoupler GO2 is connected to pin 3 of the temperature sensor. The light emission output terminal and the emitter of the optocoupler GO2 are grounded respectively. The light emission input terminal of the optocoupler GO2 is connected to the microcontroller through the resistor R8.

9. A current transformer open circuit monitoring circuit according to claim 7, characterized in that, The temperature sensor is connected to a secondary temperature reading module, which includes an optocoupler GO3, a resistor R15, and a resistor R14. One end of the resistor R15 is connected to the DC power supply VCC1, and the other end is connected to the collector of the optocoupler GO3. The collector of the optocoupler GO3 is connected to pin 1 of the temperature sensor. The light emission output terminal and the emitter of the optocoupler GO3 are grounded respectively. The light emission input terminal of the optocoupler GO3 is connected to the microcontroller through the resistor R14.

10. A current transformer open circuit monitoring circuit according to claim 7, characterized in that, The temperature sensor is also connected to a capacitor C6, one end of which is connected to pin 5 of the temperature sensor and the other end is connected to pin 4 of the temperature sensor.

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