Double-magnetic-core zero-flux micro-current sensing circuit and micro-current sensor

Abstract

The invention relates to a double-magnetic-core zero-flux micro-current sensing circuit and a micro-current sensor. The double-magnetic-core zero-flux micro-current sensing circuit comprises a main magnetic core circuit, an auxiliary magnetic core circuit, a compensating circuit and a signal processing circuit, the auxiliary magnetic core circuit can detect the induced voltage generated by the primary side current; the compensation circuit can perform compensation processing on the induced voltage to obtain compensation current; the main magnetic core circuit can superpose a compensation current and an induction current generated by a secondary side to obtain a secondary side current, and the secondary side current can enable the double-magnetic-core zero-flux micro-current sensing circuit to reach an approximate zero-flux state; the signal processing circuit can perform signal detection processing on the current output by the secondary side to obtain a detection signal. Based on the zero magnetic flux principle, the compensation circuit is arranged to generate the compensation current in the secondary side, so that the magnetic core reaches a state approximate to zero magnetic flux, the influence of the excitation current on the micro-current measurement error is reduced, the measurement error of the sensor in a strong electromagnetic field environment is effectively reduced, and the measurement precision is improved.

Description

Technical Field

[0001] The present application relates to the field of current sensing detection, and in particular to a dual-core zero-flux micro-current sensing circuit and a micro-current sensor. Background Art

[0002] With the continuous development and upgrading of the power system, the requirements for the safe operation of power equipment are getting higher and higher, and it is becoming more and more important to ensure the reliable operation of electrical equipment. A large amount of data shows that the cause of most power equipment failures is related to insulation failures, and the traditional regular offline maintenance based on prevention has limitations such as large-scale power outages during the detection process and high detection costs. In this case, the online monitoring technology of the insulation status of electrical equipment has gradually developed, among which microcurrent sensors play a vital role.

[0003] Microcurrent sensors are responsible for collecting weak current signals in the power system to monitor the insulation status of the equipment in real time, thereby ensuring the safe and stable operation of the power system. When facing strong electromagnetic field interference, the current small current sensors lack sensitivity and stability when measuring microampere leakage current, which limits their application in complex power environments. Summary of the invention

[0004] Based on this, it is necessary to provide a dual-core zero-flux micro-current sensing circuit and a micro-current sensor that can solve the above-mentioned technical problems.

[0005] In a first aspect, the present application provides a dual-core zero-flux micro-current sensing circuit, which includes a main core circuit, an auxiliary core circuit, a compensation circuit and a signal processing circuit; the main core circuit is connected to the auxiliary core circuit through the compensation circuit and the signal processing circuit respectively;

[0006] Auxiliary magnetic core circuit, used to detect the induced voltage generated by the primary side current;

[0007] A compensation circuit is used to compensate the induced voltage to obtain a compensation current;

[0008] A main magnetic core circuit is used to superimpose the compensation current with the induced current generated on the secondary side to obtain a secondary side current, and the secondary side current is used to make the double magnetic core type zero flux micro-current sensing circuit reach a state of approximately zero flux;

[0009] The signal processing circuit is used to perform signal detection processing on the current outputted from the secondary side to obtain a detection signal.

[0010] In one embodiment, the auxiliary magnetic core circuit includes a detection winding, a first secondary winding and an auxiliary magnetic core; the main magnetic core circuit includes a compensation winding, a second secondary winding and a main magnetic core; the detection winding and the first secondary winding are wound on the auxiliary magnetic core; the compensation winding and the second secondary winding are wound on the main magnetic core; the compensation winding is connected to the detection winding through the compensation circuit; the first secondary winding is connected to the second secondary winding through the signal processing circuit;

[0011] The first secondary winding is used to induce magnetic field changes to generate primary current;

[0012] Detection winding, used to detect the micro-induced voltage generated by the primary current;

[0013] The second secondary winding is used to sense the change of magnetic field and generate induced current;

[0014] The compensation winding is used for receiving the compensation current and superimposing the compensation current with the induced current to achieve an approximately zero flux state.

[0015] In one embodiment, the compensation circuit includes an active compensation circuit and a passive compensation circuit; the active compensation circuit is connected to the detection winding and the compensation winding respectively; the passive compensation circuit is connected to the active compensation circuit and the compensation winding respectively;

[0016] An active compensation circuit is used to sequentially perform signal amplification processing, filtering processing and signal conversion processing on the micro-induced voltage;

[0017] The passive compensation circuit is used to perform phase compensation processing on the current obtained by active compensation to obtain a compensation current.

[0018] In one embodiment, the active compensation circuit comprises a common-phase amplifier circuit, a first Butterworth filter circuit and a voltage-current conversion circuit connected in sequence; the common-phase amplifier circuit is connected to the detection winding; the voltage-current conversion circuit is connected to the compensation winding;

[0019] The same-phase amplifier circuit is used to amplify the signal of the micro-induced voltage;

[0020] A first Butterworth filter circuit is used to filter the voltage signal after the signal is amplified;

[0021] The voltage-current conversion circuit is used to perform voltage-current conversion processing on the voltage after filtering to obtain an active current.

[0022] In one embodiment, the first Butterworth filter circuit comprises a plurality of filter circuits; the filter circuits are connected to each other;

[0023] The filtering circuit includes a first filtering resistor, a second filtering resistor, a first feedback resistor, a second feedback resistor, and a first operational amplifier; one end of the first filtering resistor is connected to the in-phase amplifier circuit, and the other end of the first filtering resistor is respectively connected to one end of the second feedback resistor and one end of the second filtering resistor; the other end of the second filtering resistor is connected to the in-phase input terminal of the first operational amplifier; one end of the first feedback resistor is respectively connected to the inverting input terminal of the first operational amplifier and the other end of the second feedback resistor, and the other end of the first feedback resistor is grounded; the output terminal of the first operational amplifier is connected to the voltage-current conversion circuit.

[0024] In one embodiment, the voltage-to-current conversion circuit includes a first balancing resistor, a third feedback resistor, a fourth feedback resistor, a fifth feedback resistor, and a second operational amplifier;

[0025] One end of the first balancing resistor is connected to the first Butterworth filter circuit, and the other end of the first balancing resistor is respectively connected to one end of the fifth feedback resistor and the non-inverting input end of the second operational amplifier; one end of the third feedback resistor is respectively connected to the inverting input end of the second operational amplifier and one end of the fourth feedback resistor, and the other end of the third feedback resistor is grounded; the other end of the fourth feedback resistor is respectively connected to the output end of the second operational amplifier and the other end of the fifth feedback resistor.

[0026] In one embodiment, the passive compensation circuit comprises a capacitor; the capacitor is connected in parallel with the compensation winding;

[0027] The capacitor is used to perform phase compensation processing on the active current to obtain a compensation current.

[0028] In one embodiment, the signal processing circuit includes a differential amplifier circuit, a second Butterworth filter circuit, and a post-amplifier circuit connected in sequence; the differential amplifier circuit is connected to the auxiliary magnetic core circuit; the post-amplifier circuit is connected to the main magnetic core circuit;

[0029] A differential amplifier circuit is used to sample the detected current to obtain a micro-voltage signal, and perform differential amplification processing on the micro-voltage signal;

[0030] The second Butterworth filter circuit is used for filtering the micro voltage signal after the differential amplification process;

[0031] The post-amplifier circuit is used to perform phase reversal processing on the micro-voltage signal after filtering to obtain a detection signal.

[0032] In one embodiment, the differential amplifier circuit includes a sampling resistor, a first protection resistor, a second balancing resistor, a second protection resistor, a third balancing resistor and a third operational amplifier;

[0033] One end of the sampling resistor is respectively connected to the auxiliary magnetic core circuit and one end of the first protection resistor, and the other end of the sampling resistor is respectively connected to one end of the second balancing resistor and the main magnetic core circuit; the other end of the first protection resistor is respectively connected to one end of the second protection resistor and the in-phase input end of the third operational amplifier; the other end of the second balancing resistor is respectively connected to one end of the third balancing resistor and the inverting input end of the third operational amplifier; the other end of the second protection resistor is connected to the output end of the third operational amplifier; the other end of the third balancing resistor is grounded; and the output end of the third operational amplifier is connected to the second Butterworth filter circuit.

[0034] In a second aspect, the present application also provides a microcurrent sensor, which includes a dual-core zero-flux microcurrent sensing circuit as described in the first aspect above.

[0035] The above-mentioned dual-core zero-flux microcurrent sensing circuit and microcurrent sensor, the dual-core zero-flux microcurrent sensing circuit includes a main core circuit, an auxiliary core circuit, a compensation circuit and a signal processing circuit; the auxiliary core circuit can detect the induced voltage generated by the primary current; the compensation circuit can compensate the induced voltage to obtain a compensation current; the main core circuit can superimpose the compensation current with the induced current generated by the secondary side to obtain the secondary side current, and the secondary side current can make the dual-core zero-flux microcurrent sensing circuit reach an approximate zero-flux state; the signal processing circuit can perform signal detection processing on the current output by the secondary side to obtain a detection signal. This application is based on the zero-flux principle. By setting a compensation circuit to generate a compensation current in the secondary side, the magnetic core reaches a state close to zero flux, reducing the influence of the excitation current on the microcurrent measurement error, effectively reducing the measurement error of the sensor in a strong electromagnetic field environment, and improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of a dual-core zero-flux micro-current sensing circuit in one embodiment;

[0037] Figure 2 is a circuit diagram of an auxiliary magnetic core circuit and a main magnetic core circuit in one embodiment;

[0038] Figure 3 is a circuit diagram of an active compensation circuit and a passive compensation circuit in one embodiment;

[0039] Figure 4 is a circuit diagram of an active compensation circuit in one embodiment;

[0040] Figure 5 is a circuit diagram of a first Butterworth filter circuit in an embodiment;

[0041] Figure 6is a circuit diagram of a voltage-to-current conversion circuit in one embodiment;

[0042] Figure 7 is a circuit diagram of a signal processing circuit in one embodiment;

[0043] Figure 8 Schematic diagram of a dual-core zero-flux micro-current sensing circuit in one embodiment. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0045] First of all, before specifically introducing the technical solution of the embodiments of the present application, the technical background based on the embodiments of the present application is introduced.

[0046] With the continuous development and upgrading of the power system, the requirements for the safe operation of power equipment are getting higher and higher, so it is more and more important to ensure the reliable operation of electrical equipment. A large amount of data shows that the cause of most power equipment failures is related to insulation failures, and the traditional regular offline maintenance based on prevention has limitations such as large-scale power outages during the detection process and high detection costs. In this case, the online monitoring technology of the insulation status of electrical equipment has gradually developed, among which microcurrent sensors play a vital role.

[0047] Microcurrent sensors are responsible for collecting weak current signals in the power system to monitor the insulation status of the equipment in real time, thereby ensuring the safe and stable operation of the power system. When using current sensors to monitor the insulation status of electrical equipment, accuracy is the key to accurate measurement. However, when facing strong electromagnetic field interference, the measurement accuracy of existing small current sensors is often seriously affected, making it difficult to meet the needs of high-precision monitoring. In particular, when measuring microampere leakage current, the sensitivity and stability of microcurrent sensors are lacking, which limits their application in complex power environments.

[0048] Based on this, the present application provides a dual-core zero-flux micro-current sensing circuit and a micro-current sensor, aiming to solve the above technical problems.

[0049] In an exemplary embodiment, Figure 1 As shown, the present application provides a dual-core zero-flux micro-current sensing circuit: the dual-core zero-flux micro-current sensing circuit includes a main magnetic core circuit 1, an auxiliary magnetic core circuit 2, a compensation circuit 3 and a signal processing circuit 4; the main magnetic core circuit 1 is connected to the auxiliary magnetic core circuit 2 through the compensation circuit 3 and the signal processing circuit 4 respectively.

[0050] The auxiliary magnetic core circuit 2 is used to detect the induced voltage generated by the primary side current.

[0051] In the embodiment of the present application, the auxiliary magnetic core circuit 2 may be composed of a detection winding, a first secondary winding and an auxiliary magnetic core. The detection winding and the first secondary winding are wound on the auxiliary magnetic core. When the primary side current flows through, a magnetic field change is generated in the auxiliary magnetic core, and the detection winding detects the magnetic field change and generates an induced voltage.

[0052] In another embodiment of the present application, the auxiliary magnetic core circuit 2 can adopt a detection method based on a magnetoresistive sensor. The magnetoresistive sensor is very sensitive to changes in the magnetic field and can directly detect the magnetic field generated by the primary current, thereby generating an induced voltage.

[0053] The compensation circuit 3 is used to compensate the induced voltage to obtain a compensation current.

[0054] In the embodiment of the present application, the compensation circuit 3 may include an amplifier circuit, a filter circuit and a current conversion circuit. The induced voltage first enters the amplifier circuit for signal amplification, then passes through the filter circuit to remove noise, and finally the voltage signal is converted into a compensation current through the current conversion circuit.

[0055] In another embodiment of the present application, the compensation circuit 3 may also adopt a digital compensation method. The induced voltage is converted into a digital signal by an analog-to-digital converter, and then a compensation calculation is performed using a digital signal processor to obtain a digital compensation current. Finally, the digital compensation current is converted into an analog current output by a digital-to-analog converter.

[0056] The main magnetic core circuit 1 is used to superimpose the compensation current with the induced current generated on the secondary side to obtain the secondary side current, and the secondary side current is used to make the double magnetic core type zero flux micro-current sensing circuit reach an approximately zero flux state.

[0057] In the embodiment of the present application, the main magnetic core circuit 1 may be composed of a compensation winding, a second secondary winding and a main magnetic core. A weak induction current flows through the secondary winding N2. The active compensation circuit and the passive compensation circuit process the induced voltage sensed by the detection winding to generate a compensation current. , forming an induced current in the secondary winding , and the original inductive current of the secondary winding Superposition , so that the secondary current after compensation The magnitude of the primary current is inversely proportional to the number of turns and in the opposite direction, that is, Achieve a state of nearly zero magnetic flux.

[0058] The signal processing circuit 4 is used to perform signal detection processing on the current outputted from the secondary side to obtain a detection signal.

[0059] In the embodiment of the present application, the signal processing circuit 4 may include a signal conditioning circuit and a detection circuit. The current output from the secondary side is amplified, filtered, and processed by the signal conditioning circuit, and then enters the detection circuit for signal detection to obtain a detection signal.

[0060] Another embodiment of the present application can adopt a detection method based on a lock-in amplifier. The lock-in amplifier can amplify and detect signals of a specific frequency, effectively improving the signal-to-noise ratio of the signal.

[0061] The above-mentioned dual-core zero-flux micro-current sensing circuit includes a main core circuit, an auxiliary core circuit, a compensation circuit and a signal processing circuit; the auxiliary core circuit can detect the induced voltage generated by the primary current; the compensation circuit can compensate the induced voltage to obtain a compensation current; the main core circuit can superimpose the compensation current with the induced current generated by the secondary side to obtain the secondary side current, and the secondary side current can make the dual-core zero-flux micro-current sensing circuit reach a state of approximate zero flux; the signal processing circuit can perform signal detection processing on the current output by the secondary side to obtain a detection signal. This application is based on the zero flux principle. By setting a compensation circuit to generate a compensation current in the secondary side, the magnetic core reaches a state of approximate zero flux, reducing the influence of the excitation current on the micro-current measurement error, effectively reducing the measurement error of the sensor in a strong electromagnetic field environment, and improving the measurement accuracy.

[0062] In an exemplary embodiment, based on the above embodiment, see Figure 2 , the auxiliary magnetic core circuit 2 of the embodiment of the present application includes a detection winding N0, a first secondary winding N2 and an auxiliary magnetic core T2; the main magnetic core circuit 1 includes a compensation winding N3, a second secondary winding N2 and a main magnetic core T2; the detection winding N0 and the first secondary winding N2 are wound on the auxiliary magnetic core T2; the compensation winding N3 and the second secondary winding N2 are wound on the main magnetic core T2; the compensation winding N3 is connected to the detection winding N0 through the compensation circuit 3; the second secondary winding N2 is connected to the second secondary winding N2 through the signal processing circuit 4;

[0063] In the embodiment of the present application, the first secondary winding N2 is used to sense the change of magnetic field to generate the primary current. The detection winding N0 is used to detect the micro-induced voltage generated by the primary current; the second secondary winding N2 is used to sense the change of magnetic field to generate the induced current; the compensation winding N3 is used to receive the compensation current and superimpose the compensation current with the induced current to achieve an approximately zero magnetic flux state.

[0064] Specifically, the auxiliary magnetic core circuit 2 is composed of a detection winding N0, a first secondary winding N2 and an auxiliary magnetic core T2. The detection winding N0 and the first secondary winding N2 are wound around the auxiliary magnetic core T2. When the primary current flows through, a magnetic field change will be generated around the auxiliary magnetic core T2. The first secondary winding N2 can sense the magnetic field change generated by the primary current and generate a corresponding induced electromotive force, which serves to provide information about the magnetic field change of the primary current for subsequent signal processing. The detection winding N0 is specifically used to detect the micro-induced voltage generated by the primary current, and this micro-induced voltage is an important basis for subsequent compensation processing.

[0065] The main magnetic core circuit 1 is composed of a compensation winding N3, a second secondary winding N2 and a main magnetic core T2. The compensation winding N3 and the second secondary winding N2 are wound on the main magnetic core T2. The compensation winding N3 is connected to the detection winding N0 through the compensation circuit 3 to receive the compensation current. The function of the compensation current is to adjust the magnetic field in the main magnetic core T2 so that it approaches a zero flux state. The second secondary winding N2 is used to induce magnetic field changes to generate an induced current, and provide feedback information for the compensation circuit to ensure the accuracy of compensation.

[0066] The compensation circuit 3 processes the micro-induced voltage detected by the detection winding N0, generates a compensation current, and outputs it to the compensation winding N3. The compensation circuit continuously adjusts the magnitude and direction of the compensation current, and works together with the detection winding N0 to make the entire circuit reach a state of approximately zero magnetic flux.

[0067] The signal processing circuit 4 is connected to the second secondary winding N2 to process the sensed signal to obtain a detection signal for subsequent analysis and use. The signal processing circuit generally includes functional modules such as amplification, filtering, analog-to-digital conversion, etc. to improve the quality and availability of the signal.

[0068] Detection process: When the primary current flows through, a magnetic field change is generated in the auxiliary magnetic core T2, and the first secondary winding N2 senses this magnetic field change. At the same time, the detection winding N0 detects the micro-induced voltage generated by the primary current. The micro-induced voltage is transmitted to the compensation circuit 3, and the compensation circuit 3 generates a compensation current and outputs it to the compensation winding N3 of the main magnetic core circuit 1. After receiving the compensation current, the compensation winding N3 adjusts the compensation current together with the detection winding N0 to make the main magnetic core T2 approach an approximate zero flux state. At this time, the second secondary winding N2 senses the magnetic field change to generate an induced current, and the signal processing circuit 4 processes the signal output by the second secondary winding N2 to obtain a detection signal.

[0069] The embodiment of the present application can effectively reduce the influence of the excitation current on the error and improve the measurement accuracy and stability through the coordinated work of the auxiliary magnetic core circuit and the main magnetic core circuit, as well as the cooperation of the compensation circuit and the signal processing circuit. At the same time, the circuit structure is relatively simple and easy to implement and maintain.

[0070] In an exemplary embodiment, based on the above embodiment, see Figure 3 , the compensation circuit 3 of the embodiment of the present application includes an active compensation circuit 31 and a passive compensation circuit 32; the active compensation circuit 31 is connected to the detection winding N0 and the compensation winding N3 respectively; the passive compensation circuit 32 is connected to the active compensation circuit 21 and the compensation winding N3 respectively;

[0071] In the embodiment of the present application, the active compensation circuit 31 is used to perform signal amplification processing, filtering processing and signal conversion processing on the micro-induction voltage in sequence; the passive compensation circuit 32 is used to perform phase compensation processing on the current obtained by active compensation to obtain a compensation current.

[0072] Specifically, compensation circuit 3: The compensation circuit 3 is composed of an active compensation circuit 31 and a passive compensation circuit 32. The active compensation circuit 31 is connected to the detection winding N0 and the compensation winding N3 respectively, and the passive compensation circuit 32 is connected to the active compensation circuit 31 and the compensation winding N3 respectively.

[0073] The active compensation circuit 31 performs signal amplification, filtering and signal conversion on the micro-induction voltage detected by the detection winding N0 in sequence. The signal amplification process can increase the amplitude of the micro-induction voltage for subsequent processing. The filtering process can remove noise and interference signals in the micro-induction voltage and improve the quality of the signal. The signal conversion process converts the amplified and filtered voltage signal into a current signal to provide a suitable signal form for subsequent compensation.

[0074] The passive compensation circuit 32 performs phase compensation processing on the current obtained by active compensation to obtain a compensation current. The phase compensation processing can adjust the phase of the current to better match the magnetic field generated by the primary side current, thereby improving the compensation effect.

[0075] Detection process: The detection winding N0 detects the micro-induced voltage generated by the primary current and transmits it to the active compensation circuit 31. The active compensation circuit 31 performs signal amplification, filtering and signal conversion on the micro-induced voltage to obtain an intermediate current signal. This intermediate current signal enters the passive compensation circuit 32, which performs phase compensation on it to obtain a compensation current. The compensation current is output to the compensation winding N3, which adjusts the magnetic field state of the main magnetic core circuit together with the detection winding N0, so that the circuit reaches an approximately zero flux state.

[0076] The present application can effectively process the micro-induced voltage and obtain accurate compensation current through the synergistic effect of active compensation circuit and passive compensation circuit. This compensation method can improve the measurement accuracy and stability of the circuit and reduce the influence of the excitation current on the error. At the same time, the combination of active compensation and passive compensation can give full play to their respective advantages and improve the effect and reliability of compensation.

[0077] In an exemplary embodiment, based on the above embodiment, see Figure 4 The active compensation circuit 31 of the embodiment of the present application includes a common-phase amplifier circuit 311, a first Butterworth filter circuit 312 and a voltage-current conversion circuit 313 connected in sequence; the common-phase amplifier circuit 311 is connected to the detection winding N0; the voltage-current conversion circuit 313 is connected to the compensation winding N3;

[0078] In the embodiment of the present application, the in-phase amplifier circuit 311 is used to amplify the micro-induced voltage; the first Butterworth filter circuit 312 is used to filter the voltage signal after the signal is amplified; the voltage-current conversion circuit 313 is used to perform voltage-current conversion on the voltage after the filtering process to obtain an active current.

[0079] Specifically, the active compensation circuit 31 is composed of a common-phase amplifier circuit 311, a first Butterworth filter circuit 312 and a voltage-current conversion circuit 313 connected in sequence. The common-phase amplifier circuit 311 is connected to the detection winding N0, and the voltage-current conversion circuit 313 is connected to the compensation winding N3.

[0080] The in-phase amplifier circuit 311 performs signal amplification processing on the micro-induced voltage detected by the detection winding N0 to increase the amplitude of the voltage signal for subsequent processing.

[0081] The first Butterworth filter circuit 312 performs filtering processing on the voltage signal after the signal is amplified to remove noise and interference signals and improve the quality of the signal.

[0082] The voltage-to-current conversion circuit 313 may be a Howland V-I conversion circuit, which performs voltage-to-current conversion on the filtered voltage to obtain an active current, thereby providing a suitable signal form for subsequent compensation.

[0083] In-phase amplifier circuit 311: The in-phase amplifier circuit 311 may be composed of components such as an operational amplifier and a resistor. The in-phase input terminal of the operational amplifier receives a micro-induced voltage, and the voltage signal can be amplified by properly selecting the resistor value.

[0084] The first Butterworth filter circuit 312: The first Butterworth filter circuit 312 may be composed of components such as resistors, capacitors, and operational amplifiers. By properly selecting component parameters, it is possible to filter signals within a specific frequency range and remove noise and interference signals.

[0085] Voltage-to-current conversion circuit 313: The voltage-to-current conversion circuit 313 may be composed of components such as operational amplifiers, resistors, and transistors. By properly selecting component parameters, the voltage signal may be converted into a current signal.

[0086] Detection process: When the primary side flows through the microampere-level power frequency current, the induced voltage detected by the detection winding N0 is at the microvolt level. The signal is enhanced by the amplifier circuit, and the amplification factor is R3 / R2. The Butterworth filter circuit is a fourth-order active Butterworth low-pass filter circuit, which is composed of two second-order active Butterworth low-pass filter circuits, including filter resistor R4, filter resistor R5, feedback resistor R6, feedback resistor R7, operational amplifier A2, filter resistor R8, filter resistor R9, feedback resistor R 10 , feedback resistor R 11 , operational amplifier A3 and several filter capacitors. When the voltage signal amplified by the in-phase amplifier circuit passes through the filter circuit, the high-frequency noise will be filtered out, and the voltage amplification factor in the passband is (1+R7 / R6)(1+R 11 / R 10 The Howland V-I conversion circuit includes a balancing resistor R 12 , feedback resistor R 13 , feedback resistor R 14 , feedback resistor R 15 , operational amplifier A4 is used to convert the voltage signal into current form and output it to the compensation winding to achieve compensation of the secondary side current, so that the compensation winding generates a compensation current magnetic potential, maintains the zero flux state of the magnetic core, and reduces the influence of the excitation current on the error.

[0087] The embodiment of the present application can effectively process the micro-induced voltage through the synergistic effect of the in-phase amplifier circuit of the active compensation circuit, the first Butterworth filter circuit and the voltage-current conversion circuit to obtain an accurate active current. This processing method can improve the measurement accuracy and stability of the circuit and reduce the influence of the excitation current on the error. At the same time, the reasonable design of each circuit module and the parameter selection can improve the effect and reliability of signal processing.

[0088] In an exemplary embodiment, based on the above embodiment, see Figure 5 , the first Butterworth filter circuit 312 of the embodiment of the present application includes a plurality of filter circuits; each filter circuit is connected to each other;

[0089] The filter circuit of the embodiment of the present application includes a first filter resistor (R4 or R8), a second filter resistor (R5 or R9), a first feedback resistor (R6 or R 10 )、The second feedback resistor (R7 or R 11 ), a first operational amplifier (A2 or A3); one end of the first filter resistor (R4 or R8) is connected to the in-phase amplifier circuit 311, and the other end of the first filter resistor (R4 or R8) is connected to the second feedback resistor (R7 or R 11) is connected to one end of the second filter resistor (R5 or R9); the other end of the second filter resistor (R5 or R9) is connected to the non-inverting input end of the first operational amplifier (A2 or A3); the first feedback resistor (R6 or R 10 ) are connected to the inverting input of the first operational amplifier (A2 or A3) and the second feedback resistor (R7 or R 11 ) is connected to the other end of the first feedback resistor (R6 or R 10 ) is grounded; the output end of the first operational amplifier (A2 or A3) is connected to the voltage-current conversion circuit 313.

[0090] Circuit working process: The voltage signal output by the common-mode amplifier circuit enters the filter circuit through the first filter resistor. In the filter circuit, the voltage signal is input to the common-mode input terminal of the first operational amplifier through the second filter resistor. The first feedback resistor and the second feedback resistor work together with the first operational amplifier to realize the function of Butterworth filtering. The filtered voltage signal is output from the output terminal of the first operational amplifier and enters the voltage-current conversion circuit.

[0091] The embodiment of the present application can effectively remove noise and interference in the signal and improve the quality of the signal through multiple filter circuits of the first Butterworth filter circuit. This filtering method can improve the measurement accuracy and stability of the circuit and reduce errors. At the same time, by reasonably selecting the resistance value and the parameters of the operational amplifier, specific filtering characteristics can be achieved to meet different application requirements.

[0092] In an exemplary embodiment, based on the above embodiment, see Figure 6 The voltage-to-current conversion circuit 313 of the present embodiment includes a first balancing resistor R 12 , the third feedback resistor R 13 , the fourth feedback resistor R 14 , the fifth feedback resistor R 15 and a second operational amplifier A4;

[0093] In the embodiment of the present application, the first balancing resistor R 12 One end of the first balancing resistor R 12 The other end is connected to the fifth feedback resistor R 15 One end of the third feedback resistor R is connected to the non-inverting input terminal of the second operational amplifier A4; 13 One end is connected to the inverting input end of the second operational amplifier A4 and the fourth feedback resistor R 14 One end of the third feedback resistor R 13 The other end of the fourth feedback resistor R 14 The other end is connected to the output end of the second operational amplifier A4 and the fifth feedback resistor R15 The other end of the connection.

[0094] Circuit working process: The filtered voltage signal output by the first Butterworth filter circuit 312 passes through the first balancing resistor R 12 The inverting input terminal of the second operational amplifier A4 is connected to the non-inverting input terminal of the second operational amplifier A4 through the third feedback resistor R 13 and the fourth feedback resistor R 14 Connected to the output terminal to form negative feedback. At the same time, the fourth feedback resistor R 14 and the fifth feedback resistor R 15 It also participates in feedback regulation. Through this feedback structure, the second operational amplifier A4 converts the input voltage signal into a current signal output.

[0095] The embodiment of the present application can accurately convert the filtered voltage signal into a current signal through the voltage-current conversion circuit 313. This conversion method can provide a suitable input signal for the passive compensation circuit, thereby improving the effect and accuracy of the compensation. At the same time, by reasonably selecting the parameters of the resistor and the operational amplifier, a stable and reliable voltage-current conversion can be achieved.

[0096] In an exemplary embodiment, based on the above embodiment, please continue to refer to Figure 6 The passive compensation circuit 32 of the embodiment of the present application includes a capacitor C1; the capacitor C1 is connected in parallel with the compensation winding N3; the capacitor C1 is used to perform phase compensation processing on the active current to obtain a compensation current.

[0097] In the embodiment of the present application, after the active current is output from the active compensation circuit 31, it enters the compensation winding N3. At the same time, the capacitor C1 is connected in parallel with the compensation winding N3. The capacitor C1 performs phase compensation processing on the active current according to its own characteristics. After the compensation effect of the capacitor C1, the phase of the active current is adjusted to obtain the compensation current. The compensation current generates a magnetic field in the compensation winding N3, which works together with the detection winding N0 to make the main core circuit approach an approximately zero flux state.

[0098] In an exemplary embodiment, based on the above embodiment, see Figure 7 The signal processing circuit 4 of the embodiment of the present application includes a differential amplifier circuit 41, a second Butterworth filter circuit 42, and a post-stage amplifier circuit 43 connected in sequence; the differential amplifier circuit 41 is connected to the auxiliary magnetic core circuit 2; the post-stage amplifier circuit 43 is connected to the main magnetic core circuit 1;

[0099] In an embodiment of the present application, a differential amplifier circuit 41 is used to sample the detected current to obtain a microvoltage signal, and to perform differential amplification processing on the microvoltage signal; a second Butterworth filter circuit 42 is used to filter the microvoltage signal after differential amplification processing; and a post-stage amplifier circuit 43 is used to perform phase flip processing on the microvoltage signal after filtering processing to obtain a detection signal.

[0100] Specifically, the signal processing circuit 4: The signal processing circuit 4 is composed of a differential amplifier circuit 41, a second Butterworth filter circuit 42 and a post-stage amplifier circuit 43 connected in sequence. The differential amplifier circuit 41 is connected to the auxiliary magnetic core circuit 2, and the post-stage amplifier circuit 43 is connected to the main magnetic core circuit 1. The differential amplifier circuit 41 samples the detected current to obtain a micro-voltage signal, and performs differential amplification on the micro-voltage signal. Differential amplification can effectively suppress common-mode interference and improve the quality of the signal. The second Butterworth filter circuit 42 filters the micro-voltage signal after differential amplification, removes noise and interference signals, and further improves the quality of the signal. The post-stage amplifier circuit 43 performs phase reversal processing on the micro-voltage signal after filtering to obtain a detection signal. Phase reversal can make the signal more suitable for subsequent processing and analysis.

[0101] The signal processing circuit is used to collect the weak voltage signal generated when the weak current in the secondary winding N2 flows through the sampling resistor R, filter out the common mode signal interference that may appear in the secondary winding N2, and preliminarily amplify the collected weak voltage signal. 16 With the balancing resistor R 17 Equal, protection resistor R 18 With the balancing resistor R 19 When the magnification is equal, the magnification is R 18 / R 16 .

[0102] The differential amplifier circuit 41 may be composed of components such as an operational amplifier and resistors, etc. By properly selecting component parameters, differential amplification of micro voltage signals may be achieved.

[0103] The second Butterworth filter circuit 42 may be composed of components such as resistors, capacitors, and operational amplifiers, etc. By properly selecting component parameters, it is possible to filter signals within a specific frequency range and remove noise and interference signals.

[0104] The second Butterworth filter circuit can use a second-order Butterworth filter circuit. The amplitude-frequency characteristic of the second-order Butterworth filter circuit is relatively smooth, and high-frequency noise above the cutoff frequency can be well suppressed. The voltage magnification factor in the passband is 1+R 23 / R 22 .

[0105] The post-amplification circuit 43 may be composed of components such as an operational amplifier and a resistor, etc. By properly selecting the component parameters, the phase inversion and amplification processing of the micro-voltage signal after filtering can be realized.

[0106] The post-amplification circuit in the signal processing circuit is an inverting amplifier circuit, which is used to further amplify the signal and invert the signal whose phase is inverted by the differential amplifier circuit again. The amplification factor is R 26 / R 24 .

[0107] The current detected by the embodiment of the present application generates a micro-voltage signal through the auxiliary magnetic core circuit 2, and the micro-voltage signal is input to the differential amplifier circuit 41. The differential amplifier circuit 41 performs differential amplification processing on the micro-voltage signal to suppress common-mode interference. The micro-voltage signal after differential amplification enters the second Butterworth filter circuit 42 for filtering to remove noise and interference signals. The micro-voltage signal after filtering enters the post-stage amplifier circuit 43 for phase flipping and amplification processing to obtain a detection signal. The detection signal can be used for subsequent analysis and processing to determine the size and characteristics of the primary current.

[0108] The embodiment of the present application can effectively improve the quality and accuracy of the detection signal through differential amplification, filtering and phase flipping processing of the signal processing circuit. This signal processing method can reduce the influence of noise and interference and improve the measurement accuracy and stability of the circuit. At the same time, the reasonable design and parameter selection of each circuit module can improve the effect and reliability of signal processing.

[0109] In an exemplary embodiment, based on the above embodiment, see Figure 8 The differential amplifier circuit 41 of the embodiment of the present application includes a sampling resistor R, a first protection resistor R 16 , the second balancing resistor R 17 , the second protection resistor R 18 , the third balancing resistor R 19 and a third operational amplifier A5;

[0110] In the embodiment of the present application, one end of the sampling resistor R is connected to the auxiliary magnetic core circuit 2 and the first protection resistor R 16 The other end of the sampling resistor R is connected to the second balancing resistor R 17 One end of the first protective resistor R is connected to the main magnetic core circuit 1; 16 The other end is connected to the second protection resistor R 18 One end of the second balancing resistor R is connected to the non-inverting input terminal of the third operational amplifier A5; 17 Respectively with the third balancing resistor R 19 One end of the second protection resistor R is connected to the inverting input terminal of the third operational amplifier A5; 18The other end of the third balancing resistor R 19 The other end of the third operational amplifier A5 is connected to the second Butterworth filter circuit 42.

[0111] In the embodiment of the present application, the detected current generates a micro voltage signal on the sampling resistor R through the auxiliary magnetic core circuit 2. This micro voltage signal is input to the in-phase input terminal and the inverting input terminal of the third operational amplifier A5 respectively. 16 , the second protection resistor R 18 , the second balancing resistor R 17 and the third balancing resistor R 19 The third operational amplifier A5 performs differential amplification processing on the micro-voltage signal. The amplified micro-voltage signal is output from the output end of the third operational amplifier A5 and enters the second Butterworth filter circuit 42.

[0112] In the embodiment of the present application, the detected current can be effectively sampled and differentially amplified by the differential amplifier circuit. This processing method can improve the quality and stability of the signal and reduce the influence of noise and interference. At the same time, the parameters of the circuit elements can be reasonably selected to achieve accurate differential amplification and improve the measurement accuracy of the circuit.

[0113] In one embodiment, the present application also provides a micro-current sensor, which includes the dual-core zero-flux micro-current sensing circuit as described above.

[0114] In the embodiment of the present application, the current sensor includes the above-mentioned dual-core zero-flux micro-current sensing circuit. The sensing circuit is composed of a main core circuit, an auxiliary core circuit, a compensation circuit and a signal processing circuit. Through the synergistic effect of these circuits, high-precision detection of micro-current can be achieved.

[0115] The circuit includes a main magnetic core circuit, an auxiliary magnetic core circuit, a compensation circuit and a signal processing circuit. The functions and working principles of each circuit part will not be described in detail.

[0116] In the embodiment of the present application, when a microcurrent passes through the microcurrent sensor, an induced voltage is first generated in the auxiliary magnetic core circuit. The detection winding in the auxiliary magnetic core circuit detects the micro-induced voltage generated by the primary side current, and the first secondary winding is used to induce the magnetic field change to generate the primary side current. The compensation circuit compensates the induced voltage to obtain a compensation current. The main magnetic core circuit superimposes the compensation current with the induced current generated on the secondary side to make the circuit reach an approximate zero flux state. The signal processing circuit performs signal detection processing on the current output from the secondary side to obtain a detection signal. Finally, the size and characteristics of the microcurrent can be determined by analyzing and processing the detection signal.

[0117] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0118] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A dual-core zero-flux micro-current sensing circuit, characterized in that: The dual-core zero-flux micro-current sensing circuit comprises a main core circuit, an auxiliary core circuit, a compensation circuit and a signal processing circuit; the main core circuit is connected to the auxiliary core circuit through the compensation circuit and the signal processing circuit respectively; The auxiliary magnetic core circuit is used to detect the induced voltage generated by the primary side current; The compensation circuit is used to perform compensation processing on the induced voltage to obtain a compensation current; The main magnetic core circuit is used to superimpose the compensation current with the induced current generated on the secondary side to obtain a secondary side current, and the secondary side current is used to make the dual-core zero-flux micro-current sensor circuit reach an approximate zero-flux state; The signal processing circuit is used to perform signal detection processing on the current outputted from the secondary side to obtain a detection signal.

2. The dual-core zero-flux micro-current sensing circuit according to claim 1 is characterized in that: The auxiliary magnetic core circuit includes a detection winding, a first secondary winding and an auxiliary magnetic core; the main magnetic core circuit includes a compensation winding, a second secondary winding and a main magnetic core; the detection winding and the first secondary winding are wound on the auxiliary magnetic core; the compensation winding and the second secondary winding are wound on the main magnetic core; the compensation winding is connected to the detection winding through the compensation circuit; the first secondary winding is connected to the second secondary winding through the signal processing circuit; The first secondary winding is used to induce magnetic field changes to generate primary-side current; The detection winding is used to detect the micro-induced voltage generated by the primary side current; The second secondary winding is used to induce magnetic field changes to generate induced current; The compensation winding is used to receive the compensation current and superimpose the compensation current with the induced current to achieve the approximate zero magnetic flux state.

3. The dual-core zero-flux micro-current sensing circuit according to claim 2 is characterized in that: The compensation circuit includes an active compensation circuit and a passive compensation circuit; the active compensation circuit is connected to the detection winding and the compensation winding respectively; the passive compensation circuit is connected to the active compensation circuit and the compensation winding respectively; The active compensation circuit is used to sequentially perform signal amplification processing, filtering processing and signal conversion processing on the micro-induced voltage; The passive compensation circuit is used to perform phase compensation processing on the current obtained by the active compensation circuit to obtain the compensation current.

4. The dual-core zero-flux micro-current sensing circuit according to claim 3 is characterized in that: The active compensation circuit comprises a common-phase amplifier circuit, a first Butterworth filter circuit and a voltage-current conversion circuit connected in sequence; the common-phase amplifier circuit is connected to the detection winding; the voltage-current conversion circuit is connected to the compensation winding; The in-phase amplifier circuit is used to perform signal amplification processing on the micro-induced voltage; The first Butterworth filter circuit is used to filter the voltage signal after the signal is amplified; The voltage-current conversion circuit is used to perform voltage-current conversion processing on the voltage signal after filtering to obtain an active current.

5. The dual-core zero-flux micro-current sensing circuit according to claim 4 is characterized in that: The first Butterworth filter circuit includes a plurality of filter circuits; each of the filter circuits is connected to each other; The filter circuit includes a first filter resistor, a second filter resistor, a first feedback resistor, a second feedback resistor, and a first operational amplifier; One end of the first filter resistor is connected to the in-phase amplifier circuit, and the other end of the first filter resistor is connected to one end of the second feedback resistor and one end of the second filter resistor respectively; The other end of the second filter resistor is connected to the non-inverting input end of the first operational amplifier; One end of the first feedback resistor is connected to the inverting input terminal of the first operational amplifier and the other end of the second feedback resistor respectively, and the other end of the first feedback resistor is grounded; The output terminal of the first operational amplifier is connected to the voltage-to-current conversion circuit.

6. The dual-core zero-flux micro-current sensing circuit according to claim 4 is characterized in that: The voltage-current conversion circuit includes a first balancing resistor, a third feedback resistor, a fourth feedback resistor, a fifth feedback resistor and a second operational amplifier; One end of the first balancing resistor is connected to the first Butterworth filter circuit, and the other end of the first balancing resistor is connected to one end of the fifth feedback resistor and the non-inverting input end of the second operational amplifier respectively; One end of the third feedback resistor is connected to the inverting input end of the second operational amplifier and one end of the fourth feedback resistor respectively, and the other end of the third feedback resistor is grounded; The other end of the fourth feedback resistor is connected to the output end of the second operational amplifier and the other end of the fifth feedback resistor respectively.

7. The dual-core zero-flux micro-current sensing circuit according to claim 4 is characterized in that: The passive compensation circuit includes a capacitor; the capacitor is connected in parallel with the compensation winding; The capacitor is used to perform phase compensation processing on the current obtained by the active compensation circuit to obtain the compensation current.

8. The dual-core zero-flux micro-current sensing circuit according to claim 1, characterized in that: The signal processing circuit includes a differential amplifier circuit, a second Butterworth filter circuit, and a post-stage amplifier circuit which are connected in sequence; the differential amplifier circuit is connected to the auxiliary magnetic core circuit; the post-stage amplifier circuit is connected to the main magnetic core circuit; The differential amplifier circuit is used to sample the detected current to obtain a micro-voltage signal, and perform differential amplification processing on the micro-voltage signal; The second Butterworth filter circuit is used to filter the micro-voltage signal after the differential amplification process; The post-amplification circuit is used to perform phase reversal processing on the micro-voltage signal after filtering to obtain the detection signal.

9. The dual-core zero-flux micro-current sensing circuit according to claim 8, characterized in that: The differential amplifier circuit includes a sampling resistor, a first protection resistor, a second balancing resistor, a second protection resistor, a third balancing resistor and a third operational amplifier; One end of the sampling resistor is connected to the auxiliary magnetic core circuit and one end of the first protection resistor respectively, and the other end of the sampling resistor is connected to one end of the second balancing resistor and the main magnetic core circuit respectively; The other end of the first protection resistor is connected to one end of the second protection resistor and the non-inverting input end of the third operational amplifier respectively; The other end of the second balancing resistor is connected to one end of the third balancing resistor and the inverting input end of the third operational amplifier respectively; The other end of the second protection resistor is connected to the output end of the third operational amplifier; The other end of the third balancing resistor is grounded; The output end of the third operational amplifier is connected to the second Butterworth filter circuit.

10. A microcurrent sensor, characterized in that: The micro-current sensor comprises a dual-core zero-flux micro-current sensing circuit as described in any one of claims 1-9.

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