Weak current signal detection excitation circuit

Abstract

The utility model discloses a weak current signal detection excitation circuit, which comprises a self-excited oscillator, a voltage follower and a mutual inductor H1, the mutual inductor H1 comprises a cross-core current detection area for a line to be detected to pass through, the front end of the mutual inductor H1 is connected with the input end of the self-excited oscillator, and the front end of the mutual inductor H1 is connected with the output end of the self-excited oscillator. The rear end of the mutual inductor H1 is connected to the output end of the self-excited oscillator, the output end of the self-excited oscillator is connected to the input end of the voltage follower, and the output end of the voltage follower is used for outputting a detection result signal. The magnetic modulation oscillator circuit structure based on operational amplifier control is adopted, the magnetic modulation oscillator circuit can be used for detection excitation of low-frequency induction weak current signals, signal detection of weak current can be achieved, signal detection precision can be improved by matching with filtering, compensation and correction, and meanwhile the magnetic modulation oscillator circuit has the advantages of being simple in circuit structure, easy to achieve and the like.

Description

Technical Field

[0001] The utility model relates to a current signal induction circuit, in particular to a weak current signal detection excitation circuit. Background Art

[0002] There are weak current characteristic signals in the current power grid system. Such signals have the characteristics of more interference signals and are difficult to identify. In order to deal with this problem, some auxiliary circuits for weak current detection have appeared in the prior art. For the relevant circuit structure, please refer to the Chinese patent publication with publication number CN216144868U and the name "A weak current signal frequency locking detection device", which records:

[0003] "A weak current signal frequency locking detection device, comprising: a magnetic field detection unit, a signal source processing unit, a signal extraction unit and a DC signal extraction unit connected in sequence; the magnetic field detection unit is used to detect the magnetic field generated by the weak current signal, and output a signal containing weak current frequency information; the signal source processing unit is used to amplify and filter the signal output by the magnetic field detection unit; the signal extraction locking unit is used to lock the frequency of the weak current signal so that the signal output by the signal extraction locking unit changes with the frequency of the weak current signal; the DC signal extraction unit separates the signal output by the signal extraction locking unit from AC to DC, and finally outputs DC signal information";

[0004] This type of circuit uses a weak current frequency-locked detection method to improve the detection sensitivity of weak signals, but its circuit structure is complex and lacks filtering, compensation, and correction functions for weak current signals, making it difficult to implement reliable detection. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a weak current signal detection excitation circuit which helps to improve the accuracy of weak current signal detection and has a simple circuit structure and is easy to implement in view of the deficiencies of the prior art.

[0006] In order to solve the above technical problems, the utility model adopts the following technical solutions.

[0007] A weak current signal detection excitation circuit includes a self-excited oscillator, a voltage follower and a mutual inductor H1, wherein the mutual inductor H1 includes a through-current detection area for a line to be detected to pass through, a front end of the mutual inductor H1 is connected to an input end of the self-excited oscillator, a rear end of the mutual inductor H1 is connected to an output end of the self-excited oscillator, an output end of the self-excited oscillator is connected to an input end of the voltage follower, and an output end of the voltage follower is used to output a detection result signal.

[0008] Preferably, the self-excited oscillator includes an operational amplifier U1A, the front end of the mutual inductor H1 is connected to the inverting end of the operational amplifier U1A, the rear end of the mutual inductor H1 is connected to the output end of the operational amplifier U1A, the inverting end of the operational amplifier U1A is grounded through a resistor R7, the in-phase end of the operational amplifier U1A is grounded through a resistor R19, a resistor R1 is connected between the in-phase end and the output end of the operational amplifier U1A, and the output end of the operational amplifier U1A is connected to the input end of the voltage follower.

[0009] Preferably, the output terminal of the operational amplifier U1A is grounded via a capacitor C7.

[0010] Preferably, the voltage follower includes an operational amplifier U1B, the in-phase terminal of the operational amplifier U1B is connected to the output terminal of the operational amplifier U1A through a resistor R8, a resistor R1 is connected between the inverting terminal and the output terminal of the operational amplifier U1B, and the output terminal of the operational amplifier U1B serves as the output terminal of the voltage follower.

[0011] Preferably, the mutual inductor H1 includes a compensating winding.

[0012] The weak current signal detection and excitation circuit disclosed by the utility model adopts a magnetic modulation oscillator circuit structure based on operational amplifier control, which can be used for detection and excitation of low-frequency induced weak current signals. It can not only realize weak current signal detection, but also improve signal detection accuracy by cooperating with filtering, compensation and correction. At the same time, the utility model has the characteristics of simple circuit structure and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the schematic diagram of the weak current signal detection excitation circuit of the utility model. DETAILED DESCRIPTION

[0014] The present invention will be described in more detail below with reference to the accompanying drawings and embodiments.

[0015] The utility model discloses a weak current signal detection excitation circuit, see Figure 1 , which includes a self-excited oscillator 1, a voltage follower 2 and a mutual inductor H1, wherein the mutual inductor H1 includes a through-current detection area for the line to be detected to pass through, the front end of the mutual inductor H1 is connected to the input end of the self-excited oscillator 1, the rear end of the mutual inductor H1 is connected to the output end of the self-excited oscillator 1, the output end of the self-excited oscillator 1 is connected to the input end of the voltage follower 2, and the output end of the voltage follower 2 is used to output a detection result signal.

[0016] In the above circuit, a magnetic modulation oscillator circuit structure based on operational amplifier control is adopted, which can be used for detection and excitation of low-frequency induced weak current signals. It can not only realize weak current signal detection, but also improve signal detection accuracy by cooperating with filtering, compensation and correction. At the same time, the utility model has the characteristics of simple circuit structure and easy implementation.

[0017] Regarding the preferred circuit structure of the self-excited oscillator 1, in the present embodiment, the self-excited oscillator 1 includes an operational amplifier U1A, the front end of the mutual inductor H1 is connected to the inverting end of the operational amplifier U1A, the rear end of the mutual inductor H1 is connected to the output end of the operational amplifier U1A, the inverting end of the operational amplifier U1A is grounded through a resistor R7, the in-phase end of the operational amplifier U1A is grounded through a resistor R19, a resistor R1 is connected between the in-phase end and the output end of the operational amplifier U1A, and the output end of the operational amplifier U1A is connected to the input end of the voltage follower 2.

[0018] The above circuit structure forms a magnetic modulation oscillator circuit, wherein the mutual inductor H1 includes an oscillation coil, and the through-current detection area is the internal space of the oscillation coil. When there is no through-current in the mutual inductor H1, the oscillation frequency of the circuit is stable, and the output signal of the operational amplifier U1A presents a square wave with a duty cycle of 50%. When there is a through-current in the mutual inductor H1, the current signal passes through the magnetic core of the mutual inductor, causing the positive and negative duty cycles of the oscillation circuit to change, and the characteristic detection of the current signal is achieved by detecting the duty cycle change.

[0019] Furthermore, the output terminal of the operational amplifier U1A is grounded via a capacitor C7, wherein the capacitor C7 is a filter capacitor for stabilizing the circuit operation.

[0020] See also Figure 1 The voltage follower 2 includes an operational amplifier U1B, the in-phase terminal of the operational amplifier U1B is connected to the output terminal of the operational amplifier U1A through a resistor R8, a resistor R1 is connected between the inverting terminal and the output terminal of the operational amplifier U1B, and the output terminal of the operational amplifier U1B serves as the output terminal of the voltage follower 2.

[0021] In the above circuit, the operational amplifier U1B and the resistors R1 and R8 form a voltage follower circuit to isolate the distributed parameters of the oscillation circuit and make the oscillator work stably.

[0022] As a preferred embodiment, the mutual inductor H1 includes a compensation winding. In the circuit measurement process of this embodiment, when the current passes through the mutual inductor core, the positive and negative duty ratios of the oscillation circuit change. This change is relatively weak, resulting in a limited measurement range, and it is easy to cause the magnetic core to be biased, thereby causing the circuit to enter an abnormal state. At this time, compensation is required. The compensation current is an equal current with a phase opposite to that of the measured current. It can be accumulated through multiple turns of the compensation winding. This current completely offsets the measured current to make the magnetic core work in an approximately non-biased state. This application method not only broadens the measurement range, but also makes the circuit work stable, thereby improving the circuit performance of the utility model.

[0023] During operation of the circuit of the utility model, when the mutual inductor H1 has a through-current, in the quadrant in the same direction as the through-current in its oscillation cycle, the sum of the coil excitation current and the through-current increases, thereby shortening the saturation time of the magnetic core. Conversely, in the quadrant opposite to the through-current, the sum of the coil excitation current and the through-current decreases, thereby extending the saturation time of the magnetic core, thereby forming a change in the duty cycle of the output waveform of the oscillator. The change includes information about the through-current. In conjunction with subsequent circuits and software, the through-current can be analyzed, and the compensation winding can be controlled to prevent magnetic core bias, thereby effectively improving the detection accuracy of weak current signals.

[0024] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the technical scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. A weak current signal detection excitation circuit, characterized in that: The invention comprises a self-excited oscillator (1), a voltage follower (2) and a mutual inductor H1, wherein the mutual inductor H1 comprises a through-current detection area for a line to be detected to pass through, a front end of the mutual inductor H1 is connected to an input end of the self-excited oscillator (1), a rear end of the mutual inductor H1 is connected to an output end of the self-excited oscillator (1), the output end of the self-excited oscillator (1) is connected to an input end of the voltage follower (2), and the output end of the voltage follower (2) is used to output a detection result signal.

2. The weak current signal detection excitation circuit according to claim 1, characterized in that: The self-excited oscillator (1) comprises an operational amplifier U1A, the front end of the mutual inductor H1 is connected to the inverting end of the operational amplifier U1A, the rear end of the mutual inductor H1 is connected to the output end of the operational amplifier U1A, the inverting end of the operational amplifier U1A is grounded via a resistor R7, the in-phase end of the operational amplifier U1A is grounded via a resistor R19, a resistor R1 is connected between the in-phase end and the output end of the operational amplifier U1A, and the output end of the operational amplifier U1A is connected to the input end of the voltage follower (2).

3. The weak current signal detection excitation circuit according to claim 2, characterized in that: The output terminal of the operational amplifier U1A is grounded via a capacitor C7.

4. The weak current signal detection excitation circuit according to claim 2, characterized in that: The voltage follower (2) comprises an operational amplifier U1B, the in-phase terminal of the operational amplifier U1B is connected to the output terminal of the operational amplifier U1A via a resistor R8, a resistor R1 is connected between the inverting terminal and the output terminal of the operational amplifier U1B, and the output terminal of the operational amplifier U1B serves as the output terminal of the voltage follower (2).

5. The weak current signal detection excitation circuit according to claim 1, characterized in that: The mutual inductor H1 includes a compensating winding.

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