Current sensing circuit

Abstract

The invention relates to a current sensing circuit. The current sensing circuit comprises a magnetic ring module, a primary winding, a current detection module, a ripple suppression module and a compensation module. The primary winding is wound on the magnetic ring module and is connected with a current to be measured; the current detection module comprises a current detection winding and a current detection circuit, and the current detection winding is wound on the magnetic ring module; the current detection circuit is driven by the power supply voltage to generate square wave excitation voltage; the ripple suppression module comprises a suppression winding and a ripple suppression circuit; the suppression winding is wound on the magnetic ring module; the suppression circuit excites the magnetic ring module to generate target magnetic flux through the suppression winding under the action of the square wave excitation voltage so as to suppress ripple current in the current to be detected; the compensation module comprises a compensation winding and a compensation circuit; the compensation winding is wound on the magnetic ring module; the compensation circuit is connected with the current detection circuit and the ripple suppression circuit and outputs feedback current to the compensation winding, so that the compensation winding generates compensation magnetic flux in the magnetic ring module, and the magnetic ring module is in a target magnetic flux state.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current detection, in particular to a current sensing circuit. BACKGROUND

[0002] The precise measurement of current sensors has always been an important research direction in industrial production and manufacturing. With the vigorous development of the new energy industry in recent years, the requirements for current sensing technology are more stringent when new energy is connected to the power grid, and it needs to meet the requirements of high precision, wide range, and simultaneous detection of AC and DC current components.

[0003] In order to simultaneously obtain DC and AC information, the existing technical routes mainly include "Hall-magnetic flux gate composite type", "shunt + isolated operational amplifier type", "optical fiber Faraday effect type", and "magnetic modulation type zero magnetic flux type" and the like.

[0004] However, the current detection sensors currently have the problem of low detection precision. SUMMARY

[0005] Therefore, it is necessary to provide a current sensing circuit capable of improving the current detection precision in view of the above problems.

[0006] The present application provides a current sensing circuit, comprising:

[0007] A magnetic ring module;

[0008] A primary winding wound on the magnetic ring module for connecting a to-be-measured current;

[0009] A current detection module comprising a current detection winding wound on the magnetic ring module and a current detection circuit connected to the current detection winding; the current detection circuit is used for connecting a power supply voltage and generating a square wave excitation voltage under the driving of the power supply voltage; the duty cycle of the square wave excitation voltage is associated with the to-be-measured current;

[0010] A ripple suppression module comprising a suppression winding wound on the magnetic ring module and a ripple suppression circuit connected to the suppression winding; the suppression circuit is connected to the current detection module and is used for exciting the magnetic ring module to generate a target magnetic flux through the suppression winding under the action of the square wave excitation voltage, so as to suppress the ripple current in the to-be-measured current;

[0011] A compensation module comprising a compensation winding wound on the magnetic ring module and a compensation circuit connected to the compensation winding; the compensation circuit is connected to the current detection circuit and the ripple suppression circuit and is used for outputting a feedback current to the compensation winding, so that the compensation winding generates a compensation magnetic flux in the magnetic ring module, so that the magnetic ring module is in a target magnetic flux state.

[0012] In one of the embodiments, the magnetic ring module comprises a first magnetic ring and a second magnetic ring; the current detection winding comprises a direct current detection winding and an alternating current detection winding, the direct current detection winding is wound on the first magnetic ring, and the alternating current detection winding is wound on the first magnetic ring and the second magnetic ring; the current detection circuit comprises:

[0013] a self-oscillation circuit connected to both ends of the direct current detection winding and connected to the ripple suppression circuit, used for accessing the power supply voltage, generating the square wave excitation voltage at a self-oscillation point under the driving of the power supply voltage, and detecting the direct current component of the to-be-measured current;

[0014] an alternating current detection circuit connected to both ends of the alternating current detection winding and connected to the ripple suppression circuit, used for detecting the alternating current component of the to-be-measured current.

[0015] In one of the embodiments, the suppression winding is wound on the second magnetic ring; the ripple suppression circuit comprises:

[0016] an inverter, an input end of the inverter being connected to the self-oscillation point, and an output end of the inverter being connected to a first end of the suppression winding, so that the suppression winding excites the second magnetic ring to generate a magnetic field opposite to the first magnetic ring under the action of the square wave excitation voltage;

[0017] a first sampling resistor connected to a second end and an equivalent ground of the suppression winding, respectively;

[0018] a high-pass filter connected to the second end of the suppression winding, used for outputting a high-frequency ripple signal;

[0019] a first adder, two input ends of the first adder being connected to the self-oscillation point and the high-pass filter, respectively, so as to filter out the high-frequency ripple signal in the to-be-measured current;

[0020] a first low-pass filter connected to an output end of the first adder, used for outputting the direct current component of the to-be-measured current detected by the self-oscillation circuit.

[0021] In one of the embodiments, the direct current detection winding comprises:

[0022] a first detection winding and a second detection winding, a first end of the first detection winding being connected to the self-oscillation circuit, a second end of the first detection winding and a first end of the second detection winding being connected to the self-oscillation circuit, and a second end of the second detection winding being connected to the self-oscillation circuit;

[0023] The first detection winding and the second detection winding have the same number of turns, and the first detection winding and the second detection winding are opposite in winding direction of the first magnetic ring.

[0024] In one of the embodiments, the power supply voltage includes a first voltage and a second voltage; the first voltage and the second voltage have opposite polarities and the same magnitude; the self-oscillation circuit includes:

[0025] A self-oscillation resistor, a first end of the self-oscillation resistor is connected to a first end of the first detection winding and a second end of the second detection winding;

[0026] A push-pull sub-circuit, connected to a second end of the self-oscillation resistor, and a connection node as the self-oscillation point, the push-pull sub-circuit is used to access the first voltage and the second voltage;

[0027] A push-pull resistor, a first end of the push-pull resistor is connected to the push-pull sub-circuit;

[0028] A first reference voltage resistor and a second reference voltage resistor, a first end of the first reference voltage resistor is connected to the self-oscillation point, a second end of the first reference voltage resistor is connected to a first end of the second reference voltage resistor, and a second end of the second reference voltage resistor is connected to an equivalent ground;

[0029] A second sampling resistor and a third sampling resistor, a first end of the second sampling resistor is connected to a second end of the first detection winding and a first end of the second detection winding respectively, a second end of the second sampling resistor is connected to a first end of the third sampling resistor, and a second end of the third sampling resistor is connected to an equivalent ground;

[0030] A comparator, a non-inverting input end of the comparator is connected to a second end of the first reference voltage resistor, an inverting input end of the comparator is connected to a first end of the third sampling resistor, and an output end of the comparator is connected to a second end of the push-pull resistor.

[0031] In one of the embodiments, the AC detection circuit includes:

[0032] A differential resistor, two ends of the differential resistor are connected to a first end and a second end of the AC detection winding respectively;

[0033] A second low-pass filter, an input end of the second low-pass filter is connected to the first end of the AC detection winding;

[0034] A third low-pass filter, an input end of the third low-pass filter is connected to the second end of the AC detection winding;

[0035] A differential amplifier, a non-inverted input terminal of the differential amplifier is connected with an output terminal of the third low-pass filter, an inverted input terminal of the differential amplifier is connected with an output terminal of the second low-pass filter, and an output terminal of the differential amplifier is connected with the compensation circuit, for filtering out a DC component in the to-be-detected current to output an AC component of the to-be-detected current.

[0036] In one of the embodiments, the compensation winding is wound around the first magnetic ring and the second magnetic ring; and the compensation circuit comprises:

[0037] A third adder, two input terminals of the third adder are respectively connected with the ripple suppression circuit and the AC detection circuit, for performing an addition operation on the AC component and the DC component of the to-be-detected current;

[0038] An operational amplifier, an input terminal of the operational amplifier is connected with an output terminal of the third adder, and an output terminal of the operational amplifier is connected with a first terminal of the compensation winding, for outputting the feedback current to the compensation winding, so that the magnetic ring module generates the compensation magnetic flux;

[0039] An output resistor, two terminals of the output resistor are respectively connected with a second terminal of the compensation winding and an equivalent terminal.

[0040] In one of the embodiments, the compensation circuit further comprises:

[0041] A feedback controller, an input terminal of the feedback controller is connected with an output terminal of the third adder, and an output terminal of the feedback controller is connected with an input terminal of the operational amplifier.

[0042] In one of the embodiments, the feedback controller comprises a proportional-integral control circuit.

[0043] In one of the embodiments, the to-be-detected current detected by the current sensing circuit is calculated by the following formula:

[0044] ;

[0045] Wherein, i i is the to-be-detected current detected by the current sensing circuit, N i is the number of turns of the primary winding, N0 is the number of turns of the compensation winding, R9 is the resistance value of the output resistor, and U0 is the voltage of one terminal of the output resistor connected with the second terminal of the compensation winding.

[0046] The current sensing circuit comprises a ripple suppression module, which can suppress or reduce the electromagnetic induction ripple generated in the primary winding and the secondary winding thereof when the current sensing circuit is magnetically modulated, thereby improving the current detection precision. In addition, the compensation module provides compensation magnetic flux, so that the magnetic ring module is in a target magnetic flux state, and closed-loop zero magnetic flux detection of the current detection is realized. Since the magnetic core module is prone to entering a saturation state due to the strong magnetic flux generated by the measured large current, the range is limited, and in the present application, the zero magnetic flux state is realized through the compensation module, and the main magnetic flux is dynamically offset through the compensation winding. Even if the measured current increases, the total magnetic flux in the magnetic core module still maintains at a very low level and cannot trigger saturation, thereby breaking through the range limit and widening the current detection range. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the drawings needed to be used in the description of the embodiments of the present application or the related art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other related drawings can be obtained by those skilled in the art without creative labor.

[0048] Figure 1 FIG. 1 is a structural schematic diagram of a current sensing circuit in an embodiment of the present application;

[0049] Figure 2 FIG. 2 is a structural schematic diagram of a current detection circuit in an embodiment of the present application;

[0050] Figure 3 FIG. 3 is a structural schematic diagram of a direct current detection module in an embodiment of the present application;

[0051] Figure 4 FIG. 4 is a structural schematic diagram of an alternating current detection circuit in an embodiment of the present application;

[0052] Figure 5 FIG. 5 is a structural schematic diagram of a ripple suppression circuit in an embodiment of the present application;

[0053] Figure 6 FIG. 6 is a structural schematic diagram of a compensation module in an embodiment of the present application;

[0054] Figure 7 FIG. 7 is another structural schematic diagram of a compensation module in an embodiment of the present application;

[0055] Figure 8 FIG. 8 is a structural schematic diagram of a current sensing circuit in an embodiment of the present application.

[0056] BRIEF DESCRIPTION OF DRAWINGS

[0057] 110: magnetic ring module; 111: first magnetic ring; 112: second magnetic ring; 120: primary winding; 121: current detection winding; 1211: direct current detection winding; 2111: first detection winding; 2112: second detection winding; 1212: alternating current detection winding; 122: current detection circuit; 1221: self-oscillation circuit; 2211: push-pull sub-circuit; 131: suppression winding; 132: ripple suppression circuit; 141: compensation winding; 142: compensation circuit. DETAILED DESCRIPTION

[0058] In order to make the above objectives, features and advantages of the present application more clear and easily understood, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a number of different ways from those described herein without departing from the scope of the present application, and it is understood that similar improvements can be made by those skilled in the art without departing from the spirit of the present application, and therefore the present application is not limited to the specific embodiments disclosed below.

[0059] In the description of the present application, it should be understood that if these terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0060] In addition, if these terms "first", "second" appear, these terms are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features referred to. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, if the term "a plurality of" appears, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0061] In the present application, unless specifically defined otherwise, if there is any appearance of the terms "mount", "connect", "connection", "fix", and the like, these terms should be understood in a broad sense. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically defined. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0062] In the present application, unless specifically defined otherwise, if there is any appearance of the terms "mount", "connect", "connection", "fix", and the like, these terms should be understood in a broad sense. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically defined. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0063] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there can be a mediating element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there can be a mediating element. If present, the terms "vertical", "horizontal", "up", "down", "left", "right", and similar expressions used in the present application are for illustrative purposes only and do not represent the only implementation.

[0064] There are two kinds of sensors that can measure AC and DC currents simultaneously. One uses the traditional magnetic modulation method. This method has a relatively complex circuit, and the mixed measurement of AC and DC currents will cause mutual interference between AC and DC currents during measurement, resulting in inaccurate measurement results. The other is a self-excited magnetic modulation current sensor, which has a relatively simple modulation and demodulation circuit. The high-frequency excitation drives the magnetic core to be symmetrically saturated (without measured current) → the DC magnetic field of the measured current breaks the symmetric saturation, generating a DC offset of the modulation signal → the offset is extracted and the size of the measured current is back calculated → the self-excited closed loop maintains stable measurement. By using the nonlinear saturation characteristics of soft magnetic materials, the "difficult to directly measure DC / low frequency current" is converted into "easy to detect high frequency modulation signal", and finally high precision current measurement is realized. However, the self-excited magnetic modulation current sensor will generate electromagnetic induction ripple in the primary winding and its secondary winding during magnetic modulation, affecting the precision detection of current.

[0065] In combination with the drawings Figure 1, attached Figure 1 A structure diagram of a current sensing circuit in an embodiment of the present application is shown. In some embodiments, the current sensing circuit can include a magnetic ring module 110, a primary winding 120, a current detection module, a ripple suppression module, and a compensation module.

[0066] The primary winding 120 is wound around the magnetic ring module 110 and is used to access the current to be measured i i The current detection module includes a current detection winding 121 wound around the magnetic ring module 110 and a current detection circuit 122 connected to the current detection winding 121. The current detection circuit 122 is used to access a supply voltage and generates a square wave excitation voltage under the drive of the supply voltage. The duty cycle of the square wave excitation voltage is associated with the current to be measured i i The ripple suppression module includes a suppression winding 131 wound around the magnetic ring module 110 and a ripple suppression circuit connected to the suppression winding 131. The suppression circuit is connected to the current detection module and is used to generate a target magnetic flux through the magnetic ring module 110 under the action of the square wave excitation voltage through the suppression winding 131, so as to suppress the ripple current in the current to be measured i i The compensation module includes a compensation winding 141 wound around the magnetic ring module 110 and a compensation circuit 142 connected to the compensation winding 141. The compensation circuit 142 is connected to the current detection circuit 122 and the ripple suppression circuit 132 and is used to output a feedback current to the compensation winding 141, so that the compensation winding 141 generates a compensation magnetic flux in the magnetic ring module 110, so that the magnetic ring module 110 is in a target magnetic flux state.

[0067] The magnetic ring can be made of a soft magnetic material (such as permalloy, ferrite) that is easily saturated, and its permeability changes nonlinearly with the magnetic field strength.

[0068] The primary winding 120 is wound around or passes through the magnetic ring module 110. In the case of accessing the current to be measured i i , according to the Ampere loop law (current generates magnetic field, magnetic field strength is proportional to current size), a ring magnetic field will be excited inside the magnetic ring. The magnetic field generated by the primary current is not directly measured as an intermediate signal for the current detection module, the ripple suppression module, and the compensation module to further perceive and achieve high-precision detection of the current to be measured i i .

[0069] The primary winding 120 accesses the current to be measured i i , so as to convert the current to be measured i i into a measurable magnetic field signal. This magnetic field signal breaks the symmetrical saturated magnetic field generated by the current detection module under the drive of the supply voltage, so that the current detection module generates a square wave excitation voltage, and the duty cycle of the square wave excitation voltage is associated with the current to be measured i iCorrelation, for example, the current to be measured i i The current detection module can include a direct current circuit with a direct current component and an alternating current circuit with an alternating current component. When the direct current detection module detects the direct current component, if the direct current in the current to be measured i i is 0 and the duty cycle of the square wave excitation voltage is 50%, the direct current in the current to be measured i i can be detected. When the alternating current detection module detects the alternating current component, the magnitude and direction of the alternating current in the current to be measured i i change over time, and in each excitation period, its instantaneous value can be regarded as a static direct current. By high-frequency self-oscillation (the detection frequency is equal to the self-oscillation frequency of the current detection module), the alternating current in the current to be measured i i is discretized into several instantaneous direct currents, and each instantaneous direct current is detected by a flux gate, so that the alternating current in the current to be measured i i can be detected.

[0070] The target magnetic flux can refer to the magnetic flux that offsets the induced ripple magnetic flux in the primary winding 120. The ripple suppression module can suppress the electromagnetic induction ripple current generated in the primary winding 120 and the secondary winding by the self-oscillation of the current detection module.

[0071] The compensation circuit 142 is used to realize a closed-loop zero magnetic flux state. The target magnetic flux state can refer to a closed-loop zero magnetic flux state. Due to the nonlinearity of the magnetization characteristics of the magnetic core module (such as saturation characteristics and hysteresis loss), if there is residual magnetic flux in the magnetic core, it may cause the linear relationship between the detection signal and the measured current to deviate. By realizing a closed-loop zero magnetic flux state through the compensation circuit 142, the compensation magnetic flux provided by the compensation circuit 142 offsets the main magnetic flux, and the magnetic core is always in a linear operating interval with low magnetic flux density, avoiding the interference of core saturation or hysteresis on detection, which can eliminate the non-linear effects of the magnetic core and improve the detection accuracy. In addition, the square wave excitation voltage provided by the current detection module is a key reference signal for current detection. If there is residual magnetic flux in the magnetic core module, it may cause the duty cycle of the square wave excitation voltage to deviate, introducing detection errors. By realizing a closed-loop zero magnetic flux state through the compensation circuit 142, the influence of noise on detection accuracy can be reduced, the self-oscillation state of the current detection module can be stabilized, and signal interference can be reduced.

[0072] The current sensing circuit in the embodiment includes a ripple suppression module, which can suppress or reduce the electromagnetic induction ripple generated in the primary winding 120 and its secondary winding when the magnetic modulation is performed, and improve the current detection accuracy. In addition, the compensation module provides compensation magnetic flux, so that the magnetic ring module 110 is in a target magnetic flux state, and a closed-loop zero magnetic flux detection of the current detection is realized. Since the magnetic core module is easy to enter a saturation state due to the strong magnetic flux generated by the measured large current, the range is limited. In the embodiment, the zero magnetic flux state is realized through the compensation module, and the main magnetic flux is dynamically offset through the compensation winding 141. Even if the measured current i i increases, the total magnetic flux in the magnetic core module still maintains at a very low level, and saturation is not triggered, thereby breaking through the range limitation and widening the current detection range.

[0073] The structure of the current detection circuit 122 in the embodiment of the application is shown in combination with the accompanying Figure 1 and the accompanying Figure 2 , the accompanying Figure 2 structure diagram of the current detection circuit 122 in the embodiment of the application is shown, in some embodiments, the magnetic ring module 110 includes a first magnetic ring 111 and a second magnetic ring 112; the current detection winding 121 includes a direct current detection winding 1211 and an alternating current detection winding 1212, the direct current detection winding 1211 is wound on the first magnetic ring 111, and the alternating current detection winding 1212 is wound on the first magnetic ring 111 and the second magnetic ring 112; the current detection circuit 122 includes a self-oscillation circuit 1221 and an alternating current detection circuit 1222.

[0074] The self-oscillation circuit 1221 is connected to both ends of the direct current detection winding 1211 and connected to the ripple suppression circuit, is used for connecting the power supply voltage, generates a square wave excitation voltage at the self-oscillation point P under the driving of the power supply voltage, and detects the direct current component of the measured current i i .

[0075] The alternating current detection circuit 1222 is connected to both ends of the alternating current detection winding 1212 and connected to the ripple suppression circuit, and is used for detecting the alternating current component of the measured current i i .

[0076] The square wave excitation voltage of the self-oscillation circuit 1221 makes the magnetic ring have a forward-reverse alternating magnetic field, for example, under the forward excitation of the forward excitation voltage, the direct current detection winding 1211 generates a forward magnetic field, and drives the first magnetic ring 111 to be magnetized in a forward saturation direction. Under the reverse excitation of the reverse excitation voltage, the direct current detection winding 1211 generates a reverse magnetic field, and drives the first magnetic ring 111 to be magnetized in a reverse saturation direction. Therefore, the self-oscillation circuit 1221 can provide the first magnetic ring 111 with a square wave excitation voltage with stable frequency and symmetrical positive and negative amplitudes, so that the first magnetic ring 111 periodically enters a forward saturation-reverse saturation state.

[0077] The AC detection winding 1212 can realize AC signal sensing in the current to be measured i i The AC current in the current to be measured i i generates an alternating magnetic field through the primary winding 120. The alternating magnetic field is superimposed with the self-oscillating alternating excitation magnetic flux generated by the self-oscillating circuit 1221, so that the saturation time of the first magnetic ring 111 and the second magnetic ring 112 changes in each excitation period. The change rule is consistent with the size and direction of the AC instantaneous value in the period. Therefore, the magnetic flux gate detection of each instantaneous DC is realized through the AC detection circuit 1222, so that the detection of the AC current in the current to be measured i i is realized.

[0078] In some embodiments, the primary winding 120 can be wound on the first magnetic ring 111 and the second magnetic ring 112.

[0079] The structure of the DC detection module in the embodiment of the present application is shown in combination with the accompanying Figure 1 and the accompanying Figure 3 , the structure of the DC detection module in the embodiment of the present application is shown in combination with the accompanying Figure 3 In some embodiments, the DC detection winding 1211 includes a first detection winding 2111 and a second detection winding 2112. The first end of the first detection winding 2111 is connected with the self-oscillating circuit 1221, the second end of the first detection winding 2111 and the first end of the second detection winding 2112 are connected with the self-oscillating circuit 1221, and the second end of the second detection winding 2112 is connected with the self-oscillating circuit 1221; wherein the number of turns of the first detection winding 2111 and the second detection winding 2112 is the same, and the winding directions of the first detection winding 2111 and the second detection winding 2112 on the first magnetic ring 111 are opposite.

[0080] In the embodiment, the number of turns of the first detection winding 2111 and the second detection winding 2112 is the same and they are wound in opposite directions on the first magnetic ring 111. When the current to be measured i i contains an AC signal (current), the magnetic flux generated by the first detection winding 2111 and the second detection winding 2112 is the same in size and opposite in direction, and the superposition can cancel each other out, so that the interference of the AC signal (current) in the DC current detection can be eliminated, and the accuracy of the DC detection can be improved.

[0081] The structure of the DC detection module in the embodiment of the present application is shown in combination with the accompanying Figure 1 and the accompanying Figure 3In some embodiments, the supply voltage includes a first voltage and a second voltage; the first voltage and the second voltage have opposite polarities but the same magnitude; the self-excited oscillation circuit 1221 includes a self-excited oscillation resistor R1, a push-pull circuit 2211, a push-pull resistor R2, a first reference voltage resistor R3, a second reference voltage resistor R4, a second sampling resistor R5, a third sampling resistor R6, and a comparator A1. The first end of the self-excited oscillation resistor R1 is connected to the first end of the first detection winding 2111 and the second end of the second detection winding 2112; the push-pull circuit 2211 is connected to the second end of the self-excited oscillation resistor R1, and the connection node serves as the self-excited oscillation point P. The push-pull circuit 2211 is used to connect the first voltage and the second voltage; the first end of the push-pull resistor R2 is connected to the push-pull circuit 2211. 1. Connections: The first end of the first reference voltage resistor R3 is connected to the self-excited oscillation point P; the second end of the first reference voltage resistor R3 is connected to the first end of the second reference voltage resistor R4; the second end of the second reference voltage resistor R4 is connected to the equivalent ground terminal; the first end of the second sampling resistor R5 is connected to the second end of the first detection winding 2111 and the first end of the second detection winding 2112 respectively; the second end of the second sampling resistor R5 is connected to the first end of the third sampling resistor R6; the second end of the third sampling resistor R6 is connected to the equivalent ground terminal; the non-inverting input terminal of comparator A1 is connected to the second end of the first reference voltage resistor R3; the inverting input terminal of comparator A1 is connected to the first end of the third sampling resistor R6; the output terminal of comparator A1 is connected to the second end of the push-pull resistor R2.

[0082] For example, the first voltage and the second voltage can be +15V and -15V, respectively.

[0083] The push-pull circuit 2211 may include a first transistor T1 and a second transistor T2. The first transistor T1 and the second transistor T2 alternately conduct, causing the voltage level provided by the self-excited oscillation circuit 1221 to alternately flip, thus enabling the DC current detection circuit 122 to operate in a magnetic modulation state. This results in the voltage level at the self-excited oscillation point P exhibiting a square wave with duty cycle characteristics. When the measured current i... i When the DC component is 0, the duty cycle of the square wave excitation voltage is 50%. The duty cycle of the square wave excitation voltage is related to the measured current i. i The magnitude of the DC component in the current is related to the detection of the DC current.

[0084] In this embodiment, the self-oscillating circuit 1221 operates in two modes after power is supplied to comparator A1 and push-pull circuit 2211: Mode 1: The output of comparator A1 is positive, and the first transistor is turned on through the push-pull resistor R2. The voltage at the self-oscillation point P is the first voltage, for example, +15V. At this time, the voltage value at the non-inverting input terminal of comparator A1 is: U += 15R4 / (R4+R3)V, the voltage value of the inverting input terminal of the comparator A1 is: U - = 0V, the coil current gradually increases so that U - is also increasing. Mode 2: when the voltage value U - of the inverting input terminal of the comparator A1 exceeds the voltage value U + of the non-inverting input terminal, the output voltage of the output terminal of the comparator A1 is negative, the second transistor T2 in the push-pull sub-circuit 2211 is turned on, the voltage of the self-oscillation point P is -15V, the voltage value of the non-inverting input terminal of the comparator A1 is: U + = -15R4 / (R4+R3)V, the current of the first detection winding 2111 and the second detection winding 2112 first decreases and then increases so that U + is greater than U - .

[0085] In combination with the accompanying Figure 1 and the accompanying Figure 4 , the accompanying Figure 4 shows the structural schematic diagram of the AC detection circuit 1222 in an embodiment of the present application, in some embodiments, the AC detection circuit 1222 comprises a differential resistor R8, a second low-pass filter B2, a third low-pass filter B3 and a differentiator A7.

[0086] The two ends of the differential resistor are respectively connected with the first end and the second end of the AC detection winding 1212; the input terminal of the second low-pass filter B2 is connected with the first end of the AC detection winding 1212; the input terminal of the third low-pass filter B3 is connected with the second end of the AC detection winding 1212; the non-inverting input terminal of the differentiator A7 is connected with the output terminal of the third low-pass filter B3, the inverting input terminal of the differentiator A7 is connected with the output terminal of the second low-pass filter B2, and the output terminal of the differentiator A7 is connected with the compensation circuit 142, for filtering out the direct current component in the to-be-measured current i i to output the alternating current component of the to-be-measured current i i .

[0087] Among them, the second low-pass filter B2 and the third low-pass filter B3 can all be first-order passive RC (resistor-capacitor) low-pass filters.

[0088] In the present embodiment, the AC detection circuit 1222 also works in a magnetic modulation state according to the square wave excitation voltage generated by the self-oscillation circuit 1221, wherein the magnetic modulation state refers to controlling the magnetization process of the magnetic core through a high-frequency alternating excitation signal, using the nonlinear saturation characteristics of the magnetic core to modulate the to-be-measured current i i into a high-frequency alternating signal, and finally extracting the to-be-measured current i iCore working state. The current of the AC detection winding 1212 is converted into an AC voltage through the differential resistor R8, and the noise is filtered out through the first low-pass filter B4 and the second low-pass filter B2, and then the DC component of the current to be detected i i is filtered out through the differentiator A7 to prevent the DC component from interfering with the AC current detection, and finally the AC component of the current to be detected i i is output.

[0089] In combination with the accompanying Figure 1 and the accompanying Figure 5 , the accompanying Figure 5 illustrates the structure of the ripple suppression circuit in an embodiment of the present application, and in some embodiments, the suppression winding 131 is wound around the second magnetic ring 112; the ripple suppression circuit includes an inverter A2, a first sampling resistor R7, a high-pass filter B1, a first adder A3 and a first low-pass filter B4.

[0090] Among them, the high-pass filter B1 can be a first-order passive RC (resistor-capacitor) filter, and the first low-pass filter B4 can be a first-order passive RC (resistor-capacitor) low-pass filter.

[0091] The input end of the inverter A2 is connected with the self-oscillation point P, and the output end of the inverter A2 is connected with the first end of the suppression winding 131, so that the suppression winding 131 is excited under the action of the square wave excitation voltage to generate a magnetic field opposite to the first magnetic ring 111. The first sampling resistor R7 is connected with the second end and the equivalent ground of the suppression winding 131 respectively. The high-pass filter B1 is connected with the second end of the suppression winding 131 for outputting a high-frequency ripple signal; the two input ends of the first adder A3 are connected with the self-oscillation point P and the high-pass filter B1 respectively, so as to filter out the high-frequency ripple signal in the current to be detected i i . The output end of the first low-pass filter B4 is connected with the output end of the first adder A3 for outputting the DC component of the current to be detected i i detected by the self-oscillation circuit 1221.

[0092] In this embodiment, the suppression winding 131 is wound on the second magnetic ring 112, and the second magnetic ring 112 is excited by the inverter A2. The input end of the inverter A2 is connected with the self-oscillation point P, so that the excitation states of the first magnetic ring 111 and the second magnetic ring 112 are completely opposite. The voltage signal of the excitation current of the suppression winding 131 on the first sampling resistor R7 obtains a high-frequency ripple signal through the high-pass filter B1. The high-frequency ripple signal and the signal output by the self-oscillation circuit 1221 are combined through the first adder A3 to obtain a direct current, and then the signal demodulation is completed through the first low-pass filter B4 to output the current to be detected i iThe DC component. The ripple suppression circuit 132 in this embodiment can cancel the high-frequency electromagnetic induced ripple current generated by self-excited oscillation in the primary winding 120 and the secondary winding (including DC detection winding 1211, AC detection winding 1212, suppression winding 131 and compensation winding 141).

[0093] Combined with appendix Figure 6 , attached Figure 6 This illustration shows one of the structural schematic diagrams of a compensation module according to an embodiment of the present application. In some embodiments, the compensation winding 141 is wound around a first magnetic ring 111 and a second magnetic ring 112; the compensation circuit 142 includes a third adder A4, an operational amplifier A6, and an output resistor.

[0094] The two input terminals of the third adder A4 are connected to the ripple suppression circuit 132 and the AC detection circuit 1222, respectively, for testing the current i. i The AC and DC components are added together; the input of operational amplifier A6 is connected to the output of the third adder A4, and the output of operational amplifier A6 is connected to the first end of compensation winding 141 to output feedback current to compensation winding 141 so that magnetic ring module 110 generates compensation flux; the two ends of the output resistor are connected to the second end of compensation winding 141 and the equivalent ground end, respectively.

[0095] In this embodiment, the third adder A4 will convert the current to be measured i i The DC and AC components are added together and input to operational amplifier A6. After amplification, operational amplifier A6 generates a feedback current in compensation winding 141, causing compensation winding 141 to generate a feedback current magnetomotive force (i.e., compensation flux) in the first magnetic ring 111 and the second magnetic ring 112. When the magnetomotive force is unbalanced, the duty cycle of the voltage level at the self-excited oscillation point P is not 50%, thereby generating an error current signal. This error current signal is generated by operational amplifier A6 and flows through compensation winding 141, keeping the magnetic cores in the first magnetic ring 111 and the second magnetic ring 112 (magnetic ring module 110) in a zero flux state. Thus, the duty cycle of the self-excited oscillation point P is maintained at 50%, thereby improving detection accuracy and range.

[0096] Combined with appendix Figure 7 , attached Figure 7 A second schematic diagram of the compensation module in one embodiment of this application is shown. The compensation circuit 142 may further include a feedback controller. The input terminal of the feedback controller A5 is connected to the output terminal of the third adder A4, and the output terminal of the feedback controller A5 is connected to the input terminal of the operational amplifier A6.

[0097] In this embodiment, the compensation circuit 142 is improved by adding a feedback controller based on the compensation circuit 142 in the previous embodiment. The third adder A4 converts the measured current i iThe DC and AC components are added together and then input to the third adder A4 of the feedback controller to measure the current i. i The DC and AC components are added together and input to operational amplifier A6. After amplification, operational amplifier A6 generates a feedback current in compensation winding 141, causing compensation winding 141 to generate feedback current magnetomotive force (i.e., compensation flux) in the first magnetic ring 111 and the second magnetic ring 112. When the magnetomotive force is unbalanced, the duty cycle of the voltage level at the self-excited oscillation point P is not 50%, thus generating an error current signal. The feedback controller continuously integrates the error current signal to improve the compensation speed. The feedback current generated by operational amplifier A6 flows through compensation winding 141, so that the magnetic core in the first magnetic ring 111 and the second magnetic ring 112 (magnetic ring module 110) maintains a zero flux state. Thus, the duty cycle of the self-excited oscillation point P is maintained at 50%, thereby improving the detection accuracy and range.

[0098] In some embodiments, the feedback controller includes a proportional-integral control circuit.

[0099] In some embodiments, the current to be measured i detected by the current sensing circuit i Calculated using the following formula:

[0100] ;

[0101] Where i i N is the current to be measured detected by the current sensing circuit. i R9 is the number of turns in the primary winding 120, N0 is the number of turns in the compensation winding 141, R9 is the resistance value of the output resistor, and U0 is the voltage across one end of the output resistor connected to the second terminal of the compensation winding 141 (i.e., the voltage across the output resistor). Figure 8 (Voltage at the closed-loop signal output point in the circuit).

[0102] Combined with appendix Figure 1 and 8 , attached Figure 8 A second schematic diagram of a current sensing circuit according to one embodiment of this application is shown. In some embodiments, the current sensing circuit can realize low-ripple AC / DC current detection. The current sensor in this embodiment may include a first magnetic ring 111, a second magnetic ring 112, a primary winding 120, a DC detection winding 1211, an AC detection winding 1212, a self-excited oscillation circuit 1221, an AC detection circuit 1222, a suppression winding 131, a ripple suppression circuit 132, a compensation winding 141, and a compensation circuit 142.

[0103] The DC detection winding 1211 includes a first detection winding 2111 and a second detection winding 2112, and the first detection winding 2111 and the second detection winding 2112 are both wound on the first magnetic ring 111. The primary winding 120 is wound on the first magnetic ring 111 and the second magnetic ring 112. The AC detection winding 1212 is wound on the first magnetic ring 111 and the second magnetic ring 112. The self-oscillation circuit 1221 includes a self-oscillation resistor R1, a push-pull sub-circuit 2211, a push-pull resistor R2, a first reference voltage resistor R3, a second reference voltage resistor R4, a second sampling resistor R5, a third sampling resistor R6, and a comparator A1. The AC detection circuit 1222 includes a differential resistor R8, a second low-pass filter B2, a third low-pass filter B3, and a differentiator A7. The suppression winding 131 is wound on the second magnetic ring 112. The ripple suppression circuit 132 includes an inverter A2, a first sampling resistor R7, a high-pass filter B1, a first adder A3, and a first low-pass filter B4. The compensation winding 141 is wound on the first magnetic ring 111 and the second magnetic ring 112. The compensation circuit 142 includes a third adder A4, an operational amplifier A6, and an output resistor R9.

[0104] The DC detection winding and the self-oscillation circuit can be used to detect the DC part of the magnetic flux of the current to be measured; the ripple suppression circuit can be used to suppress the electromagnetic induction ripple current generated in the primary winding and the secondary winding by the self-oscillation; the AC detection winding and the AC detection circuit can be used to detect the AC part of the magnetic flux of the current to be measured; and the compensation winding and the compensation circuit can be used to realize the closed-loop zero-magnetic-flux state. The working principles of the circuits and the windings can be referred to the foregoing description, which will not be described here.

[0105] In some embodiments, any combination of the technical features of the above-described embodiments can be made, and for the sake of brevity, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combination of the technical features does not exist, it should be considered as the scope of the description.

[0106] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be noted that for ordinary skilled persons in the art, several modifications 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 patent protection scope of the present application should be subject to the appended claims.

Claims

1. A current sensing circuit, characterized by, The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device.

2. The current sensing circuit of claim 1, wherein, The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device.

3. The current sensing circuit of claim 2, wherein, The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device.

4. The current sensing circuit of claim 2, wherein, The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. The application relates to a current detection device. 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The application relates to a a first detection winding and a second detection winding, a first end of the first detection winding being connected with the self-oscillation circuit, a second end of the first detection winding being connected with the second end of the first detection winding and the second end of the second detection winding; wherein the first detection winding and the second detection winding have the same number of turns, and the first detection winding and the second detection winding are wound in opposite directions on the first magnetic ring.

5. The current sensing circuit of claim 4, wherein, the supply voltage comprises a first voltage and a second voltage; the first voltage and the second voltage have opposite polarities and the same magnitude; the self-oscillation circuit comprises: a self-oscillation resistor, a first end of the self-oscillation resistor being connected with the first end of the first detection winding and the second end of the second detection winding; a push-pull sub-circuit, connected with a second end of the self-oscillation resistor, and a connection node serving as the self-oscillation point, the push-pull sub-circuit being configured to access the first voltage and the second voltage; a push-pull resistor, a first end of the push-pull resistor being connected with the push-pull sub-circuit; a first reference voltage resistor and a second reference voltage resistor, a first end of the first reference voltage resistor being connected with the self-oscillation point, a second end of the first reference voltage resistor being connected with a first end of the second reference voltage resistor, and a second end of the second reference voltage resistor being connected with a ground terminal; a second sampling resistor and a third sampling resistor, a first end of the second sampling resistor being connected with the second end of the first detection winding and the first end of the second detection winding respectively, a second end of the second sampling resistor being connected with a first end of the third sampling resistor, and a second end of the third sampling resistor being connected with the ground terminal; a comparator, a non-inverting input terminal of the comparator being connected with the second end of the first reference voltage resistor, an inverting input terminal of the comparator being connected with the first end of the third sampling resistor, and an output terminal of the comparator being connected with a second end of the push-pull resistor.

6. The current sense circuit of claim 2, wherein, the AC detection circuit comprises: a differential resistor, two ends of the differential resistor being connected with a first end and a second end of the AC detection winding respectively; a second low-pass filter, an input terminal of the second low-pass filter being connected with the first end of the AC detection winding; a third low-pass filter, an input terminal of the third low-pass filter being connected with the second end of the AC detection winding; a differentiator, a non-inverting input terminal of the differentiator being connected with an output terminal of the third low-pass filter, an inverting input terminal of the differentiator being connected with an output terminal of the second low-pass filter, and an output terminal of the differentiator being connected with the compensation circuit, configured to filter out a direct current component in the to-be-measured current to output an alternating current component of the to-be-measured current.

7. The current sense circuit of claim 2, wherein, the compensation winding is wound on the first magnetic ring and the second magnetic ring; and the compensation circuit comprises: a third adder, two input terminals of the third adder being connected with the ripple suppression circuit and the AC detection circuit respectively, configured to perform an addition operation on the alternating current component and the direct current component of the to-be-measured current. an operational amplifier, an input terminal of the operational amplifier is connected with an output terminal of the third adder, and an output terminal of the operational amplifier is connected with a first terminal of the compensation winding to output the feedback current to the compensation winding so that the magnetic ring module generates the compensation magnetic flux; an output resistor, two terminals of the output resistor are respectively connected with a second terminal and an equivalent terminal of the compensation winding.

8. The current sense circuit of claim 7, wherein, The compensation circuit further comprises: a feedback controller, an input terminal of the feedback controller is connected with an output terminal of the third adder, and an output terminal of the feedback controller is connected with an input terminal of the operational amplifier.

9. The current sensing circuit of claim 8, wherein, The feedback controller comprises a proportional-integral control circuit.

10. The current sensing circuit of claim 7, wherein, The to-be-measured current detected by the current sensing circuit is calculated by the following formula: ； Wherein, i i The current to be measured detected by the current sensing circuit, N i The number of turns of the primary winding, N0 is the number of turns of the compensation winding, R9 is the resistance value of the output resistor, U0 is the voltage of one end of the second end of the output resistor connected to the compensation winding.

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