CN114414878B - Double-excitation automatic desaturation closed loop fluxgate current sensor circuit - Google Patents
Double-excitation automatic desaturation closed loop fluxgate current sensor circuit Download PDFInfo
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- CN114414878B CN114414878B CN202210090002.9A CN202210090002A CN114414878B CN 114414878 B CN114414878 B CN 114414878B CN 202210090002 A CN202210090002 A CN 202210090002A CN 114414878 B CN114414878 B CN 114414878B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a double-excitation automatic desaturation closed loop fluxgate current sensor circuit, which comprises a direct current magnetic flux detection circuit, an alternating current magnetic flux detection circuit, an automatic demagnetization saturation conduction circuit and a magnetic flux compensation circuit, wherein the circuit magnetic flux compensation circuit is respectively connected with the direct current magnetic flux detection circuit, the alternating current magnetic flux detection circuit and the automatic demagnetization saturation conduction circuit; the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the demagnetization signal so as to enable the primary coil magnetic core to exit a magnetic flux saturation state. Therefore, the magnetic core of the primary coil of the current sensor works in a zero-magnetic-flux state and has an automatic desaturation function. The high-precision detection of direct current and alternating current can be realized, the whole circuit structure is simple and practical, the production cost is low, and the performance is good.
Description
Technical Field
The invention relates to the technical field of current sensors, in particular to a double-excitation automatic desaturation closed-loop fluxgate current sensor circuit.
Background
The fluxgate current sensor has a high response time (less than 1us), good temperature characteristics (less than 100PPM), high sensitivity (uA level), wide measurement range (mA level to several kA level), and can simultaneously measure direct current and alternating current, and has an important position in the field of high-performance current measurement.
The fluxgate current sensor inevitably has energy loss during the operation, and the error of the fluxgate current sensor is mainly caused by the existence of the excitation current. The method of reducing the error of the current sensor mainly reduces/or equivalently reduces the excitation current. Therefore, reducing the exciting current by reasonably designing the flux compensation output is an important means for improving the accuracy of the current inductor.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the invention aims to provide a double-excitation automatic desaturation closed-loop fluxgate current sensor circuit.
In order to achieve the above object, an embodiment of the present invention provides a dual-excitation automatic desaturation closed-loop fluxgate current sensor circuit, where the dual-excitation automatic desaturation closed-loop fluxgate current sensor circuit includes:
the direct current magnetic flux detection circuit comprises a self-excited oscillation circuit, the self-excited oscillation circuit comprises a first exciting coil W1, and the self-excited oscillation circuit detects direct current of a primary coil through the first exciting coil W1;
an alternating current flux detection circuit including a winding coil W3 for detecting an alternating current of the primary coil by the winding coil (W3);
the automatic demagnetization flux saturation circuit is connected with the direct current magnetic flux detection circuit and is used for detecting the magnetic flux state of the primary coil magnetic core through the direct current magnetic flux detection circuit and outputting a demagnetization signal when a full magnetic flux state is detected;
the magnetic flux compensation circuit is respectively connected with the direct current magnetic flux detection circuit, the alternating current magnetic flux detection circuit and the automatic demagnetization flux saturation circuit, and comprises a compensation coil W4 used for outputting a reverse magnetic flux signal according to a detection signal of the direct current magnetic flux detection circuit so that a magnetic core of a primary coil is in a zero magnetic flux state; the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the detection signal of the alternating current magnetic flux detection circuit so as to enable the magnetic core of the primary coil to be in a zero magnetic flux state; and the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the demagnetization signal so as to enable the primary coil magnetic core to exit a magnetic flux saturation state.
Further, according to an embodiment of the present invention, the dc magnetic flux detection circuit further includes:
the balance demagnetizing circuit is connected with the self-oscillation circuit and comprises a second exciting coil W2, the second exciting coil W2 is connected with the first exciting coil W1 in parallel, the magnetic fluxes are opposite, and the balance demagnetizing circuit is used for offsetting the exciting magnetic fluxes of the first exciting coil W1 through the second exciting coil W2.
Further, according to an embodiment of the present invention, the first excitation coil W1 is wound on the first core, the second excitation coil W2 is wound on the second core, the winding coil W3 is wound on the third core, and the compensation coil W4 is wound on the surface of the whole body of the first excitation coil W1, the second excitation coil W2, and the winding coil W3.
Further, according to an embodiment of the present invention, the self-oscillation circuit further includes:
a first operational amplifier U1;
a first resistor R1, one end of the first resistor R1 is connected with the non-inverting input end of the first operational amplifier U1, and the other end of the first resistor R1 is connected with a reference power supply VO;
a second resistor R2, one end of the second resistor R2 is connected to the non-inverting input terminal of the first operational amplifier U1, the other end of the second resistor R2 is connected to the output terminal of the first operational amplifier U1 through a third resistor R4, and the other end of the second resistor R2 is further connected to one end of the first exciting coil W1;
a fourth resistor R3, one end of the fourth resistor R3 being connected to the other end of the first exciting coil W1, the other end of the fourth resistor R3 being connected to the inverting input terminal of the first operational amplifier U1;
a first capacitor C1, one end of the first capacitor C1 being connected to the other end of the fourth resistor R3, the other end of the first capacitor C1 being connected to a reference power supply;
and a fifth resistor R5, one end of the fifth resistor R5 being connected to the other end of the first exciting coil W1, and the other end of the fifth resistor R5 being connected to the reference power VO.
Further, according to an embodiment of the present invention, the balanced degaussing circuit further includes a balanced resistor R6, one end of the balanced resistor R6 is connected to one end of the second exciting coil W2, the other end of the second exciting coil W2 is connected to the one end of the first exciting coil W1, and the other end of the balanced resistor R6 is connected to the reference power VO.
Further, according to an embodiment of the present invention, the alternating-current magnetic flux detection circuit includes:
a sixth resistor R11, one end of the sixth resistor R11 being connected to one end of the winding coil W3, the other end of the winding coil W3 being connected to the reference power VO;
a second operational amplifier U3, a non-inverting input terminal of the second operational amplifier U3 being connected to the reference power VO, an inverting input terminal of the second operational amplifier U3 being connected to the other terminal of the sixth resistor R11, and/or an inverting input terminal of the second operational amplifier U3 being connected to the other terminal of the sixth resistor R11 via a seventh resistor R12;
and an eighth resistor R13, wherein one end of the eighth resistor R13 is connected to the inverting input terminal of the second operational amplifier U3, and the other end of the eighth resistor R13 is connected to the output terminal of the second operational amplifier U3.
Further, according to an embodiment of the present invention, the automatic demagnetization saturation-on circuit includes:
the demagnetization signal generation circuit is used for generating a magnetic saturation demagnetization signal;
the signal input end of the frequency detection circuit is connected with the self-oscillation circuit and is used for outputting a demagnetization conduction control signal when detecting that the frequency of the self-oscillation circuit is greater than a set value;
and the electronic switch circuit is respectively connected with the demagnetization signal generation circuit and the frequency detection circuit, so that the demagnetization switch-on control signal controls and outputs the magnetically saturated demagnetization signal.
Further, according to an embodiment of the present invention, the demagnetization signal generation circuit includes:
the square wave generating circuit is used for generating a square wave signal;
the filter circuit is connected with the square wave generating circuit and is used for filtering the square wave signals into the magnetic saturation demagnetization signals with sawtooth waveform; the filter circuit comprises a ninth resistor R14 and a second capacitor C6, one end of the ninth resistor R14 is connected with the square wave generating circuit, the other end of the ninth resistor R14 is connected with one end of the second capacitor C6, and the other end of the second capacitor C6 is connected with the reference power supply VO.
Further, according to an embodiment of the present invention, the electronic switching circuit includes:
the source electrode of the first MOS tube Q1 is connected with the output end of the magnetic saturation demagnetization signal of the demagnetization signal generating circuit;
a second MOS transistor Q2, a drain of the second MOS transistor Q2 being connected to a drain of the first MOS transistor Q1, a source of the second MOS transistor Q2 being connected to the ac magnetic flux detection circuit, gates of the second MOS transistor Q2 and the first MOS transistor Q1 being connected to a power supply VCC through a tenth resistor R15, respectively;
third MOS pipe Q3, third MOS pipe Q3's drain electrode respectively with second MOS pipe Q2's grid, first MOS pipe Q1's grid are connected, third MOS pipe Q3's grid still is connected with power supply VCC through tenth resistance R15, third MOS pipe Q3's source is connected with reference ground, third MOS pipe Q3's grid is connected with reference ground through eleventh resistance R16, third MOS pipe Q3's grid with frequency detection circuit's demagnetization switches on control signal output and connects.
Further, according to an embodiment of the present invention, the dual-excitation auto-desaturation closed-loop fluxgate current sensor circuit further includes: integration and power amplifier circuit, direct current magnetic flux detection circuitry, alternating current magnetic flux detection circuitry and automatic demagnetization lead to saturation circuit respectively through integration and power amplifier circuit with the magnetic flux compensation circuit is connected to through right direct current magnetic flux detection circuitry, alternating current magnetic flux detection circuitry and automatic demagnetization lead to saturation circuit's output signal carry out the integration operation and power amplification after, export extremely compensation coil W4.
The double-excitation automatic desaturation closed loop fluxgate current sensor circuit provided by the embodiment of the invention is respectively connected with the direct current magnetic flux detection circuit, the alternating current magnetic flux detection circuit and the automatic demagnetization desaturation circuit through the magnetic flux compensation circuit, wherein the magnetic flux compensation circuit comprises a compensation coil (W4) which is used for outputting a reverse magnetic flux signal according to a detection signal of the direct current magnetic flux detection circuit so as to enable a magnetic core of a primary coil to be in a zero magnetic flux state; the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the detection signal of the direct current magnetic flux detection circuit so as to enable the magnetic core of the primary coil to be in a zero magnetic flux state; and the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the demagnetization signal so as to enable the primary side coil magnetic core to exit a magnetic flux saturation state. Thus, the current sensor works in a zero-flux state and has an automatic desaturation function. The high-precision detection of direct current and alternating current can be realized, the whole circuit structure is simple and practical, the production cost is low, and the performance is good.
Drawings
Fig. 1 is a block diagram of a dual-excitation auto-desaturation closed-loop fluxgate current sensor circuit according to an embodiment of the present invention.
Reference numerals:
a direct current magnetic flux detection circuit 10;
a self-oscillation circuit 101;
a balanced degaussing circuit 102;
an alternating-current magnetic flux detection circuit 20;
an automatic demagnetization turn-on saturation circuit 30;
an electronic switching circuit 301;
and a proportional integral and power amplifier circuit 40.
The objects, features and advantages of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein may be combined with other embodiments.
Referring to fig. 1, an embodiment of the present invention provides a dual-excitation auto-desaturation closed-loop fluxgate current sensor circuit, including: the direct current magnetic flux detection circuit 10 comprises a self-excited oscillation circuit 101, the self-excited oscillation circuit 101 comprises a first exciting coil W1, and the self-excited oscillation circuit 101 detects direct current of a primary coil through the first exciting coil W1; as shown in fig. 1, the first excitation coil W1 is used to detect a primary dc magnetic flux, the first excitation coil W1 operates in a magnetic field saturation state (referred to as a fluxgate), the fluxgate is normally symmetric, and the average value of the operating current is zero without the influence of an external magnetic field, that is, the average value of the currents output by the first excitation coil W1 is zero. When an external magnetic field is influenced (a current sensor is usually a magnetic field of primary current), the positive and negative symmetry of the fluxgate is broken, the average value of the working current of the first excitation coil W1 is not zero at the moment, and the current reflects the current value of the primary coil and is converted and output through a subsequent circuit, so that the direct current of the primary coil can be detected.
The alternating current magnetic flux detection circuit 20 comprises a winding coil W3, and alternating current of a primary coil is detected through the winding coil (W3); the winding coil W3 is an alternating-current magnetic flux detection coil. When the primary current of the sensor is alternating current or sudden change occurs, the primary current is detected by the winding coil W3, and a corresponding current signal is output. The current is converted and output through a subsequent circuit, and then the alternating current of the primary coil can be detected.
The automatic demagnetization saturation circuit 30 is connected with the direct current magnetic flux detection circuit 10, and is used for detecting the magnetic flux state of the primary coil magnetic core through the direct current magnetic flux detection circuit 10 and outputting a demagnetization signal when detecting a full magnetic flux state; under a certain condition, the magnetic flux of the primary coil may enter a saturation state, and the self-excited oscillation circuit 101 inside the dc magnetic flux detection circuit 10 outputs a higher oscillation frequency, and when the oscillation frequency reaches a set value, the automatic demagnetization saturation circuit 30 outputs a demagnetization signal.
The magnetic flux compensation circuit is respectively connected with the direct current magnetic flux detection circuit 10, the alternating current magnetic flux detection circuit 20 and the automatic demagnetization flux saturation circuit 30, and comprises a compensation coil W4 used for outputting a reverse magnetic flux signal according to a detection signal of the direct current magnetic flux detection circuit 10 so as to enable a magnetic core of a primary coil to be in a zero magnetic flux state; the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to a detection signal of the alternating current magnetic flux detection circuit 20 so that the magnetic core of the primary coil is in a zero magnetic flux state; and the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the demagnetization signal so as to enable the primary side coil magnetic core to exit a magnetic flux saturation state. Specifically, on the one hand, the detection output currents of the dc magnetic flux detection circuit 10 and the ac magnetic flux detection circuit 20 can be output to the outside through the compensation coil W4 for reading by the device. On the other hand, the detection output currents of the dc magnetic flux detection circuit 10 and the ac magnetic flux detection circuit 20 can be output by the compensation coil W4 to perform magnetic flux compensation on the primary coil magnetic core, so that the primary coil magnetic core operates in a zero magnetic flux state, thereby improving the detection accuracy of the current inductor. The demagnetization signal output by the automatic demagnetization flux-saturation circuit 30 can be output by the compensation coil W4 to reverse the magnetic flux, so as to force the magnetic flux to exit the saturation state, thereby improving the detection accuracy of the current inductor.
The double-excitation automatic desaturation closed loop fluxgate current sensor circuit provided by the embodiment of the invention is respectively connected with the direct current magnetic flux detection circuit 10, the alternating current magnetic flux detection circuit 20 and the automatic desaturation flux saturation circuit 30 through a magnetic flux compensation circuit, wherein the magnetic flux compensation circuit comprises a compensation coil W4 for outputting a reverse magnetic flux signal according to a detection signal of the direct current magnetic flux detection circuit 10 to enable a magnetic core of a primary coil to be in a zero magnetic flux state; the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to a detection signal of the alternating current magnetic flux detection circuit 10 so as to enable the magnetic core of the primary coil to be in a zero magnetic flux state; and the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the demagnetization signal so as to enable the primary coil magnetic core to exit a magnetic flux saturation state. Therefore, the magnetic core of the primary coil of the current sensor works in a zero-magnetic-flux state and has an automatic desaturation function. The high-precision detection of direct current and alternating current can be realized, the whole circuit structure is simple and practical, the production cost is low, and the performance is good.
In some embodiments of the present invention, the dc magnetic flux detection circuit 10 further includes: the balance demagnetizing circuit 102 is connected to the self-oscillation circuit 101, the balance demagnetizing circuit 102 includes a second exciting coil W2, the second exciting coil W2 is connected in parallel to the first exciting coil W1, and the magnetic fluxes are opposite in direction, so that the exciting magnetic flux of the first exciting coil W1 is cancelled by the second exciting coil W2. The excitation flux by the first excitation coil W1 (first excitation winding) may affect the winding coil W3 and the compensation coil W4, resulting in a decrease in detection accuracy. The second excitation coil W2 is an excitation flux balance winding (second excitation winding), and the influence of the excitation flux of the first excitation coil W1 on the winding coil W3 and the compensation coil W4 can be counteracted through the anti-parallel connection relationship between the second excitation coil W2 and the first excitation coil W1, so that the detection precision is improved.
Optionally, the first excitation coil W1 is wound on the first core, the second excitation coil W2 is wound on the second core, the winding coil W3 is wound on the third core, and the compensation coil W4 is wound on the surface of the whole body formed by the first excitation coil W1, the second excitation coil W2 and the winding coil W3. Specifically, the winding method of the first excitation coil W1, the second excitation coil W2, the winding coil W3 and the compensation coil W4 is as follows: w1 is wound on the first iron core, W2 is wound on the second iron core, W3 is wound on the third iron core, then the first iron core, the second iron core and the third iron core are overlapped, W4 is wound on the first iron core, the second iron core and the third iron core, and meanwhile, the excitation fluxes of the first excitation coil W1 and the second excitation coil W2 are in a reverse relation, so that the coupling flux of the compensation coil W4 is reduced as much as possible, and the detection accuracy is improved.
Optionally, the self-oscillation circuit 101 further includes: the circuit comprises a first operational amplifier U1, a first resistor R1, a second resistor R2, a fourth resistor R3, a first capacitor C1 and a fifth resistor R5, wherein one end of the first resistor R1 is connected with the non-inverting input end of the first operational amplifier U1, and the other end of the first resistor R1 is connected with a reference power supply VO; one end of the second resistor R2 is connected to the non-inverting input terminal of the first operational amplifier U1, the other end of the second resistor R2 is connected to the output terminal of the first operational amplifier U1 through a third resistor R4, and the other end of the second resistor R2 is further connected to one end of the first exciting coil W1; one end of the fourth resistor R3 is connected with the other end of the first excitation coil W1, and the other end of the fourth resistor R3 is connected with the inverting input end of the first operational amplifier U1; one end of the first capacitor C1 is connected to the other end of the fourth resistor R3, and the other end of the first capacitor C1 is connected to a reference power supply VO; one end of the fifth resistor R5 is connected to the other end of the first exciting coil W1, and the other end of the fifth resistor R5 is connected to the reference power VO. The first operational amplifier U1, the first operational amplifier U1, the first resistor R1, the second resistor R2, the fourth resistor R3, the first capacitor C1, the first exciting coil W1 and the fifth resistor R5 form a self-oscillation circuit 101. The third resistor R4 is a current limiting resistor of the self-oscillation circuit, R5 is a dc magnetic flux current detection resistor, and the first exciting coil W1 is a dc magnetic flux detection coil (exciting winding 1). By designing appropriate parameters, the first excitation coil W1 and the second excitation coil W2 work in a positive and negative magnetic field saturation state (called as a fluxgate), under the influence of no external magnetic field, positive and negative currents of the fluxgate are symmetrical, the average value of the working currents is zero, that is, the average value of the voltage of the fifth resistor R5 is zero. When an external magnetic field is influenced (the current sensor is usually the magnetic field of the primary current), the symmetry of the positive current and the negative current of the fluxgate is broken. At this time, the average value of the working current of the first exciting coil W1 is not zero, that is, the average value of the voltage of the fifth resistor R5 is not zero, and the voltage is output to the compensating coil W4 by the subsequent proportional-integral and power-amplifying circuit 40, and is compensated for the reverse magnetic flux by the compensating coil W4 and is output to the outside.
The balanced degaussing circuit 102 further includes a balanced resistor R6, one end of the balanced resistor R6 is connected to one end of the second exciting coil W2, the other end of the second exciting coil W2 is connected to the one end of the first exciting coil W1, and the other end of the balanced resistor R6 is connected to the reference power supply VO. The balance resistor R6 is a balance resistor of the fifth resistor R5, and the magnetic fluxes of the second exciting coil W2 and the first exciting coil W1 are guaranteed to be mutually offset.
The ac magnetic flux detection circuit 20 includes: a sixth resistor R11, a second operational amplifier U3, and an eighth resistor R13, wherein one end of the sixth resistor R11 is connected to one end of the winding coil W3, and the other end of the winding coil W3 is connected to the reference power supply VO; a non-inverting input terminal of the second operational amplifier U3 is connected to the reference power VO, an inverting input terminal of the second operational amplifier U3 is connected to the other terminal of the sixth resistor R11, and/or an inverting input terminal of the second operational amplifier U3 is connected to the other terminal of the sixth resistor R11 through a seventh resistor R12; one end of the eighth resistor R13 is connected to the inverting input terminal of the second operational amplifier U3, and the other end of the eighth resistor R13 is connected to the output terminal of the second operational amplifier U3. The second operational amplifier U3, the sixth resistor R11, the seventh resistor R12 and the fourth resistor R3 constitute an ac magnetic flux amplifying circuit, and the winding coil W3 is an ac magnetic flux detecting coil. The primary side alternating current of the current sensor is detected by the winding coil W3, when the primary side current of the current sensor is alternating current or has sudden change, the primary side alternating current is detected by the winding coil W3, amplified by the second operational amplifier U3 and output to the coupling capacitor C3. The magnetic flux is coupled to a proportional-integral ratio and power amplifier circuit through a capacitor C3, and finally reverse magnetic flux is output by a W4 for compensation, so that zero magnetic flux is achieved.
The automatic demagnetization turn-on saturation circuit 30 includes: the demagnetization control circuit comprises a demagnetization signal generating circuit, a frequency detection circuit and an electronic switch circuit 301, wherein the demagnetization signal generating circuit is used for generating a magnetic saturation demagnetization signal; the signal input end of the frequency detection circuit is connected with the self-oscillation circuit 101 and is used for outputting a demagnetization conduction control signal when detecting that the frequency of the self-oscillation circuit 101 is greater than a set value; the electronic switch circuit 301 is connected to the demagnetization signal generation circuit and the frequency detection circuit, respectively, so that the demagnetization switch-on control signal controls the output of the magnetically saturated demagnetization signal.
The frequency detection circuit is a frequency selection circuit to select and output the frequency of the input signal. The output of the second operational amplifier U3 is connected via the FX signal terminal. When the frequency detection circuit detects that the frequency of the FX signal end is higher than a set value, a high level signal is output.
The demagnetization signal generation circuit includes: the square wave generating circuit is used for generating square wave signals; the filter circuit is connected with the square wave generating circuit and is used for filtering the square wave signal into the magnetic saturation demagnetization signal with sawtooth signal waveform; the filter circuit comprises a ninth resistor R14 and a second capacitor C6, one end of the ninth resistor R14 is connected with the square wave generating circuit, the other end of the ninth resistor R14 is connected with one end of the second capacitor C6, and the other end of the second capacitor C6 is connected with the reference power supply VO. The square wave generated by the square wave generator is filtered by a ninth resistor R14 and a second capacitor C6 to generate a sawtooth wave.
The electronic switching circuit 301 includes: the demagnetization circuit comprises a first MOS tube Q1, a second MOS tube Q2 and a third MOS tube Q3, wherein the source electrode of the first MOS tube Q1 is connected with the output end of a magnetic saturation demagnetization signal of the demagnetization signal generating circuit; the drain of the second MOS transistor Q2 is connected to the drain of the first MOS transistor Q1, and the source of the second MOS transistor Q2 is connected to the ac magnetic flux detection circuit 20, so that the ac magnetic flux detection circuit 20 amplifies and outputs the magnetic saturation demagnetization signal; optionally, the first MOS transistor Q1 and the second MOS transistor Q2 may be P-type MOS transistors, respectively. The first MOS transistor Q1 and the second MOS transistor Q2 are connected in anti-series (the gate is connected to the gate, and the drain is connected to the drain in two pairs). The first MOS tube Q1 and the second MOS tube Q2 can be used for controlling the output of the magnetic saturation demagnetization signal.
The drain electrode of third MOS pipe Q3 respectively with second MOS pipe Q2, first MOS pipe Q1's grid are connected, third MOS pipe Q3's grid still is connected with power supply VCC through tenth resistance R15, third MOS pipe Q3's source is connected with reference ground, third MOS pipe Q3's grid is connected with reference ground through eleventh resistance R16, third MOS pipe Q3's grid with frequency detection circuit's demagnetization switches on the control signal output and connects. The third MOS transistor Q3 may be an N-type MOS transistor or a triode. So as to control the on/off driving of the first and second MOS transistors Q1, Q2. The tenth resistor R15 is a pull-up resistor, and provides bias voltage for the first MOS transistor Q1, the second MOS transistor Q2 and the third MOS transistor Q3.
Under the normal working state that the magnetism of the primary coil does not have magnetic saturation, the frequency monitoring circuit filters the output signal of the self-oscillation circuit 101, and no high level output exists. The third MOS transistor Q3 is not turned on, so that the first MOS transistor Q1 and the second MOS transistor Q2 are also not turned on (the cut-off resistance is large), and the square wave in the square wave generating circuit cannot enter the alternating current magnetic energy detection circuit. When the primary coil is magnetically in a magnetically saturated operating state. At this time, the self-oscillation circuit 101 in the dc magnetic flux detection circuit 10 outputs a high oscillation frequency, and outputs a high level after passing through the frequency monitoring circuit (the FX frequency is greater than a certain set value), so that the third MOS transistor Q3 is turned on, the MOS transistors Q1 and Q2 in the electronic switch circuit 301 are also turned on, and at this time, the square wave generated by the square wave generator is filtered by R14 and C6 to generate a sawtooth wave, which is then applied to the ac magnetic flux detection circuit 20 through the MOS transistors Q1 and Q2, amplified inside the ac magnetic flux detection circuit 20, coupled and output by the capacitor C3, and finally, the W4 outputs a reverse magnetic flux output, so that the primary coil core is out of the magnetic flux saturation state.
The double-excitation automatic desaturation closed loop fluxgate current sensor circuit further comprises: and the direct current magnetic flux detection circuit 10, the alternating current magnetic flux detection circuit 20 and the automatic demagnetization saturation circuit 30 are respectively connected with the magnetic flux compensation circuit through the integration and power amplification circuit, so that the output signals of the direct current magnetic flux detection circuit 10, the alternating current magnetic flux detection circuit 20 and the automatic demagnetization saturation circuit 30 are subjected to integration operation and power amplification and then output to the compensation coil W4.
Optionally, the integrating and power amplifying circuit includes: the proportional-integral circuit comprises an operational amplifier U2, a resistor R8, a resistor R9 and a capacitor C2, wherein the reverse phase input end of the operational amplifier U2 is connected with one end of the resistor R8, the other end of the resistor R8 is connected with the direct current magnetic flux detection circuit 10 through a resistor R7, the other end of the resistor R8 is further connected with the alternating current magnetic flux detection circuit 20 through a resistor C3, the reverse phase input end of the operational amplifier U2 is further connected with one end of the capacitor C2 through a resistor R9, the other end of the capacitor C2 is connected with the output end of the operational amplifier U2, and the positive phase input end of the operational amplifier U2 is further connected with the reference power supply VO through a first resistor R10. The proportional-integral circuit integrates and outputs the output signals of the dc magnetic flux detection circuit 10 and the ac magnetic flux detection circuit 20.
Optionally, the power amplifying circuit includes a transistor Q4 and a transistor Q5, a base of the transistor Q4 is connected to the output terminal of the operational amplifier U2, a collector of the transistor Q4 is connected to a power supply VCC, an emitter of the transistor Q4 is connected to an emitter of the transistor Q5, a collector of the transistor Q5 is connected to a second power supply VEE or a first reference ground terminal, and the transistor Q5 is connected to the output terminal of the operational amplifier U2. Transistor Q4 and transistor Q5 are current amplifying transistors. After the signals output by the dc magnetic flux detection circuit 10 and the ac magnetic flux detection circuit 20 are processed by the proportional-integral circuit, the power amplification circuit outputs a compensation current to the compensation coil W4 to balance the primary current magnetic flux, so that the magnetic core of the sensor processes a zero magnetic flux state.
The following describes the operation of the circuit in the embodiment of the present invention with reference to fig. 1:
as shown in fig. 1, after the circuit is powered on, the voltage UR1> UC1, a high level signal at the output end of the first operational amplifier U1 is sent to the first excitation coil W1, the first excitation coil W1 generates a current, the current is gradually increased and detected by the fifth resistor R5, the voltage of the fifth resistor R5 is filtered by the fourth resistor R3 and the first capacitor C1 and then is added to the inverting input end of the first operational amplifier U1, when UC1> UR1, the output signal of the first operational amplifier U1 is inverted and is output to the first excitation coil W1 with a low level, and when UC1< UR1, the output signal of the first operational amplifier U1 is inverted again, and this is repeated, so that automatic oscillation is realized. The second exciting coil W2 is an exciting magnetic flux balance winding, and is in a parallel connection relationship with the first exciting coil W1 for reverse magnetic flux, and the resistor R6 is a balance resistor of the resistor R5, so that the influence of the exciting magnetic flux of the first exciting coil W1 on the winding coil W3 and the compensating coil W4 is counteracted, and the detection precision is improved. By designing appropriate parameters, the first excitation coil W1 and the second excitation coil W2 work in a positive and negative magnetic field saturation state, and under the influence of no external magnetic field, the fluxgate current of the first excitation coil W1 is positive and negative symmetric, and the average value of the working current is zero, that is, the average value of the voltage of the fifth resistor R5 is zero. When an external magnetic field influences, the positive and negative symmetry of the fluxgate is broken, the average value of the working current of the fluxgate is not zero at the moment, that is, the average value of the voltage of R5 is not zero, and the voltage is output to the compensation coil W4 after being processed by the subsequent proportional integral and power amplifier circuit 40. The magnetic flux compensation is carried out on the primary coil magnetic core through the compensation coil W4, so that the magnetic core of the sensor is in a zero magnetic flux state. The detection current IS also externally output through the IS of the compensation coil W4. The ac magnetic flux detection circuit 20 includes an ac magnetic flux amplification circuit including a second operational amplifier U3, a sixth resistor R11, a seventh resistor R12, and a fourth resistor R3, and the winding coil W3 is an ac magnetic flux detection coil. When the primary current of the sensor is alternating current or sudden change occurs, the winding coil is detected by W3, amplified by a second operational amplifier U3 and output to a coupling capacitor C3. The flux compensation of the primary coil core is performed through the compensation coil W4, so that the magnetic core of the sensor is in a zero flux state. Under a certain working condition, the magnetic flux of the magnetic core of the sensor enters a saturation state, then the self-excited oscillation circuit 101 in the direct current magnetic flux detection circuit 10 outputs a higher oscillation frequency signal, the frequency-selective filtering output is carried out through the frequency monitoring circuit, when the oscillation frequency is higher than a set value at the FX signal end detected by the frequency detection circuit, a high-level signal is output, a third MOS tube Q3 in the electronic switch circuit 301 is conducted, a first MOS tube Q1 and a second MOS tube Q2 are conducted, a sawtooth wave generated after a square wave generated by the square wave generator is filtered by a ninth resistor R14 and a second capacitor C6 is added to the alternating current magnetic flux detection circuit 20 through a first MOS tube Q1 and a second MOS tube Q2, the sawtooth wave is amplified by the alternating current magnetic flux detection circuit 20 and then is coupled to the proportional integral and power amplification circuit 40 through a capacitor C3, and the proportional integral and power amplification circuit carries out integral operation on the signal, after power amplification, the reverse flux is finally output from W4, forcing the flux out of saturation.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing detailed description, or equivalent changes may be made in some of the features of the embodiments. All equivalent structures made by using the contents of the specification and the attached drawings of the invention can be directly or indirectly applied to other related technical fields, and are also within the protection scope of the patent of the invention.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (9)
1. A dual excitation auto-desaturation closed loop fluxgate current sensor circuit comprising:
the direct current magnetic flux detection circuit comprises a self-excited oscillation circuit, the self-excited oscillation circuit comprises a first exciting coil (W1), and the self-excited oscillation circuit detects direct current of a primary coil through the first exciting coil (W1);
an alternating current flux detection circuit including a winding coil (W3) for detecting an alternating current of the primary coil by the winding coil (W3);
the automatic demagnetization flux saturation circuit is connected with the direct current magnetic flux detection circuit and is used for detecting the magnetic flux state of the primary coil magnetic core through the direct current magnetic flux detection circuit and outputting a demagnetization signal when a full magnetic flux state is detected;
the magnetic flux compensation circuit is respectively connected with the direct current magnetic flux detection circuit, the alternating current magnetic flux detection circuit and the automatic demagnetization flux saturation circuit, and comprises a compensation coil (W4) which is used for outputting a reverse magnetic flux signal according to a detection signal of the direct current magnetic flux detection circuit so that a magnetic core of the primary coil is in a zero magnetic flux state; the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the detection signal of the alternating current magnetic flux detection circuit so as to enable the magnetic core of the primary coil to be in a zero magnetic flux state; the magnetic flux compensation circuit is also used for outputting a reverse magnetic flux signal according to the demagnetization signal so as to enable the primary side coil magnetic core to exit a magnetic flux saturation state;
wherein the content of the first and second substances,
the self-oscillation circuit further includes:
a first operational amplifier (U1);
a first resistor (R1), one end of the first resistor (R1) is connected with the non-inverting input end of the first operational amplifier (U1), and the other end of the first resistor (R1) is connected with a reference power supply;
a second resistor (R2), one end of the second resistor (R2) being connected to the non-inverting input terminal of the first operational amplifier (U1), the other end of the second resistor (R2) being connected to the output terminal of the first operational amplifier (U1) through a third resistor (R4), the other end of the second resistor (R2) being further connected to one end of the first exciting coil (W1);
a fourth resistor (R3), one end of the fourth resistor (R3) being connected to the other end of the first exciting coil (W1), the other end of the fourth resistor (R3) being connected to the inverting input terminal of the first operational amplifier (U1);
a first capacitor (C1), one end of the first capacitor (C1) being connected to the other end of the fourth resistor (R3), the other end of the first capacitor (C1) being connected to a reference power supply;
a fifth resistor (R5), one end of the fifth resistor (R5) being connected to the other end of the first exciting coil (W1), the other end of the fifth resistor (R5) being connected to the reference power source.
2. The dual-excitation auto-desaturation closed loop fluxgate current sensor circuit of claim 1, wherein said dc flux detection circuit further comprises:
the balance demagnetizing circuit is connected with the self-oscillation circuit and comprises a second exciting coil (W2), the second exciting coil (W2) is connected with the first exciting coil (W1) in parallel, the magnetic fluxes are opposite, and the second exciting coil (W2) is used for offsetting the exciting magnetic fluxes of the first exciting coil (W1).
3. The dual excitation auto-desaturation closed loop fluxgate current sensor circuit of claim 2, wherein said first excitation coil (W1) is wound on a first core, said second excitation coil (W2) is wound on a second core, said winding coil (W3) is wound on a third core, said compensation coil (W4) is wound on the surface of the whole body of said first excitation coil (W1), said second excitation coil (W2) and said winding coil (W3).
4. The dual-excitation auto-desaturation closed loop fluxgate current sensor circuit according to claim 2, wherein said balanced degaussing circuit further comprises a balancing resistor (R6), one end of said balancing resistor (R6) is connected to one end of said second excitation coil (W2), the other end of said second excitation coil (W2) is connected to said one end of said first excitation coil (W1), and the other end of said balancing resistor (R6) is connected to said reference power supply.
5. The dual-excitation auto-desaturation closed loop fluxgate current sensor circuit of claim 1, wherein said ac flux sense circuit comprises:
a sixth resistor (R11), one end of the sixth resistor (R11) being connected to one end of the winding coil (W3), the other end of the winding coil (W3) being connected to the reference power supply;
a second operational amplifier (U3), a non-inverting input terminal of the second operational amplifier (U3) being connected to the reference power supply, an inverting input terminal of the second operational amplifier (U3) being connected to the other terminal of the sixth resistor (R11), and/or an inverting input terminal of the second operational amplifier (U3) being connected to the other terminal of the sixth resistor (R11) through a seventh resistor (R12);
an eighth resistor (R13), one end of the eighth resistor (R13) is connected with the inverting input end of the second operational amplifier (U3), and the other end of the eighth resistor (R13) is connected with the output end of the second operational amplifier (U3).
6. The dual-excitation automatic desaturation closed loop fluxgate current sensor circuit according to any one of claims 1 to 5, wherein said automatic desaturation and saturation circuit comprises:
the demagnetization signal generation circuit is used for generating a magnetic saturation demagnetization signal;
the signal input end of the frequency detection circuit is connected with the self-oscillation circuit and is used for outputting a demagnetization conduction control signal when detecting that the frequency of the self-oscillation circuit is greater than a set value;
and the electronic switch circuit is respectively connected with the demagnetization signal generation circuit and the frequency detection circuit, so that the demagnetization switch-on control signal controls and outputs the magnetically saturated demagnetization signal.
7. The dual-excitation automatic desaturation closed loop fluxgate current sensor circuit of claim 6, wherein said demagnetization signal generation circuit comprises:
the square wave generating circuit is used for generating a square wave signal;
the filter circuit is connected with the square wave generating circuit and is used for filtering the square wave signal into the magnetic saturation demagnetization signal with sawtooth signal waveform; the filter circuit comprises a ninth resistor (R14) and a second capacitor (C6), one end of the ninth resistor (R14) is connected with the square wave generating circuit, the other end of the ninth resistor (R14) is connected with one end of the second capacitor (C6), and the other end of the second capacitor (C6) is connected with a reference power supply.
8. The dual-excitation auto-desaturation closed loop fluxgate current sensor circuit of claim 6, wherein said electronic switching circuit comprises:
the source electrode of the first MOS tube (Q1) is connected with the output end of the magnetically saturated demagnetization signal of the demagnetization signal generating circuit;
a second MOS tube (Q2), wherein the drain electrode of the second MOS tube (Q2) is connected with the drain electrode of the first MOS tube (Q1), the source electrode of the second MOS tube (Q2) is connected with the alternating current magnetic flux detection circuit, and the grid electrodes of the second MOS tube (Q2) and the first MOS tube (Q1) are respectively connected with a power supply through a tenth resistor (R15);
third MOS pipe (Q3), the drain electrode of third MOS pipe (Q3) respectively with the grid of second MOS pipe (Q2), the grid of first MOS pipe (Q1) are connected, the grid of third MOS pipe (Q3) still is connected with power supply through tenth resistance (R15), the source electrode of third MOS pipe (Q3) is connected with ground reference, the grid of third MOS pipe (Q3) is connected with ground reference through eleventh resistance (R16), the grid of third MOS pipe (Q3) with the demagnetization of frequency detection circuit switches on the control signal output and connects.
9. The dual-excitation auto-desaturation closed loop fluxgate current sensor circuit of claim 1 or 2, further comprising: integration and power amplifier circuit, direct current magnetic flux detection circuitry, alternating current magnetic flux detection circuitry and automatic demagnetization lead to saturation circuit respectively through integration and power amplifier circuit with the magnetic flux compensation circuit is connected to through right direct current magnetic flux detection circuitry, alternating current magnetic flux detection circuitry and automatic demagnetization lead to saturation circuit's output signal carry out the integration operation and power amplification after, export to compensation coil (W4).
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