Variable magnetic inductance current sensor and overcurrent detection method thereof

Abstract

In the disclosed embodiment, a variable magnetic inductor (VMI) current sensor and an overcurrent detection method thereof are provided, wherein the current sensor comprises: an overcurrent detection inductor element, which generates a first excitation current in response to an applied first excitation voltage to form a first excitation magnetic field; an overcurrent detection circuit, which is used to determine whether the current to be measured is overcurrent based on the frequency and / or amplitude of the first excitation current related to the change in inductance value; wherein the overcurrent detection inductor element is arranged so that the direction of the normal of its cross section deviates from a preset angle relative to the magnetic field direction of the magnetic field of the current to be measured, so that the maximum current to be measured that the overcurrent detection inductor element can be used to detect is greater than the rated current. Therefore, by adjusting the angle of the overcurrent detection inductor element, the current to be measured that is a multiple of the rated current can be detected, which is very suitable for short-circuit current detection caused by thermal runaway of the battery pack.

Description

Technical Field

[0001] The present disclosure relates to the technical field of measuring current using electromagnetic induction technology, and in particular to a variable magnetic inductance current sensor and an overcurrent detection method thereof. Background Art

[0002] Current sensors are used in various industries such as batteries, converters, chargers, renewable energy, industry, motor vehicles, etc. At present, the current sensors for detecting current mainly include shunts, current transformers, Hall effect sensors, magnetoresistance and fluxgate technology sensors.

[0003] The most widely used is the Hall effect sensor based on the Hall effect, mainly because it has good reliability and low power consumption, and it is also a non-contact measurement. However, according to the principle of the Hall effect, the Hall effect sensor based on the Hall effect needs to use a magnetic core to concentrate the magnetic flux generated by the current to be measured, and the magnetic field formed by the magnetic core needs to be perpendicular to the direction of the current to be measured. Therefore, the Hall effect sensor based on the Hall effect is often large in size. If used without a magnetic core, this Hall effect current sensor will be affected by EMC interference, resulting in low detection accuracy.

[0004] For example, US Patent No. US022260652A1 or US022357366A1. This patent uses a fluxgate measurement device to measure current, but this measurement device is still built around one or more magnetic cores. The main disadvantages of this technology are the need to use a large and heavy magnetic core, and the high power consumption required to excite the fluxgate secondary.

[0005] The patents published by the World Intellectual Property Office with publication number WO2020023127A1, US patent publication number US011227560A1 or China publication number CN114994386A respectively record the scheme of measuring current through xMR type current measurement equipment, but their measurement equipment are built around one or more magnetoresistive elements. The assembly of these magnetoresistive elements is complicated. In addition, these patents need to be built around the Wheatstone bridge, so this type of measurement equipment is easily affected by the skin effect, which will cause significant measurement errors in the case of large currents.

[0006] The overcurrent detection method of sensors based on the principles of fluxgate current sensors, Hall effect sensors, shunts, etc. is generally to increase the range by 20% on the basis of the rated current for overcurrent detection. The range is small, which is not conducive to the situation where the detected current may reach several times the rated current in some current sensor scenarios. For example, in the battery management system, the short-circuit current of 5 times the rated current or even higher is detected due to the short-circuit failure of the battery pack. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, the purpose of the present disclosure is to provide a variable magnetic inductor (VMI) current sensor and an overcurrent detection method thereof to solve the problems in the related art.

[0008] The first aspect of the present disclosure provides a variable magnetic inductance current sensor, comprising: an overcurrent detection inductor element, which generates a first excitation current in response to an applied first excitation voltage, and the first excitation current forms a first excitation magnetic field; an overcurrent detection circuit, which is used to determine whether a current to be measured is overcurrent based on the frequency and / or amplitude of the first excitation current related to the change in the inductance value of the overcurrent detection inductor element; wherein the overcurrent detection inductor element is arranged so that the direction of the normal line of its cross section deviates from a preset angle relative to the magnetic field direction of the magnetic field of the current to be measured generated by the current to be measured, so as to set the effective cross-sectional area of ​​the overcurrent detection inductor element to receive the magnetic flux lines of the magnetic field of the current to be measured, so that the maximum current to be measured that the overcurrent detection inductor element can be used to detect is greater than the rated current, and the multiple relationship of the maximum current to be measured relative to the rated current is determined by the preset angle.

[0009] In an embodiment of the first aspect, the variable magnetic inductance current sensor includes: at least one measuring inductance element, which generates a second excitation current in response to an applied second excitation voltage, and the second excitation current forms a second excitation magnetic field; when the second excitation magnetic field is affected by the magnetic field of the current to be measured, the inductance value of the measuring inductance element changes for calculating the current to be measured; wherein the at least one measuring inductance element is placed so that the normal direction of its cross section is parallel to the magnetic field direction of the magnetic field of the current to be measured.

[0010] In an embodiment of the first aspect, the overcurrent detection inductor element is connected to a capacitor to form an LC oscillation circuit.

[0011] In an embodiment of the first aspect, the overcurrent detection circuit is used to determine whether the current to be measured is overcurrent based on detecting whether the oscillation frequency of the LC oscillation circuit reaches a preset frequency threshold; the preset frequency threshold is determined based on a mathematical relationship between the current to be measured and the oscillation frequency, a rated value of the current to be measured, and the preset angle.

[0012] In an embodiment of the first aspect, the mathematical relationship is obtained by linking the relationship between the inductance value of the overcurrent detection inductor element and the oscillation frequency, the relationship between the magnetic flux of the measured current magnetic field generated by the measured current and the magnetic permeability of the overcurrent detection inductor element, and the relationship between the magnetic permeability and the inductance value of the overcurrent detection inductor element.

[0013] In an embodiment of the first aspect, the variable magnetic inductance current sensor includes: an overcurrent detection excitation circuit, coupled to the overcurrent detection inductor element, for applying an excitation voltage to the overcurrent detection inductor element in response to a pulse signal to generate an excitation current signal, and leading out at least one output terminal in the conductive loop where the overcurrent detection inductor element is located, for outputting at least one current amplitude change signal related to the rate of change of the excitation current over time; the at least one current amplitude change signal is used to obtain current amplitude change information; an overcurrent detection circuit, for obtaining the current amplitude change information, and comparing the current amplitude change information with the current amplitude change thresholds corresponding to the two first excitation magnetic fields with opposite magnetic field directions, so as to determine whether the current to be measured corresponding to the current amplitude change information is overcurrent; the overcurrent detection inductor element is configured to be alternately applied with voltages in opposite directions over time to alternately form the two first excitation magnetic fields with opposite magnetic field directions.

[0014] In an embodiment of the first aspect, the overcurrent detection excitation circuit outputs a pair of current amplitude change signals based on two signal points in the conductive loop where the overcurrent detection inductor element is located, and the pair of current amplitude change signals are respectively related to excitation currents that form two first excitation magnetic fields with opposite magnetic field directions; the overcurrent detection excitation circuit includes: a first conductive loop, a second conductive loop, and a switch group; the first conductive loop and the second conductive loop are configured to have a common circuit, and the overcurrent detection inductor element is arranged in the common circuit; the switch group is arranged in the first conductive loop and the second conductive loop, and the switch is set by two pulse signals of the same frequency and with a phase difference. state to alternately turn on / off the first conductive loop and the second conductive loop; wherein, when the first conductive loop and the second conductive loop are turned on, voltages of opposite polarities are applied to both ends of the common circuit to form excitation currents of opposite directions in the one overcurrent detection inductor element; a first resistor is arranged in series with the overcurrent detection inductor element in the common circuit; two signal points formed at both ends of the first resistor lead out a pair of output ends to output a pair of electrical signals as the pair of current amplitude change signals; the variable magnetic inductance current sensor also includes: a differential operation circuit, which is used to obtain current amplitude change information based on the differential calculation of the pair of current amplitude change signals.

[0015] In an embodiment of the first aspect, the overcurrent detection circuit includes: a first comparator, outputting a first comparison result of the current amplitude change information and a first current amplitude change threshold corresponding to a magnetic field direction; wherein, when the current amplitude change information is higher than the first current amplitude change threshold, the first comparison result is a signal value indicating overcurrent; a second comparator, outputting a second comparison result of the current amplitude change information and a second current amplitude change threshold corresponding to another opposite magnetic field direction; wherein, when the current amplitude change information is lower than the second current amplitude change threshold, the second comparison result is a signal value indicating overcurrent; and an OR logic operation unit, wherein two input terminals are coupled to the output terminals of the first comparator and the second comparator, and an output terminal outputs an OR logic operation result of the two inputs.

[0016] In an embodiment of the first aspect, the at least one measuring inductance element includes: a pair of measuring inductance elements configured such that the magnetic fields of the second excitation magnetic fields formed by each element are in opposite directions; or, a measuring inductance element configured to alternately form second excitation magnetic fields in opposite directions over time.

[0017] The second aspect of the present disclosure provides an overcurrent detection method, which is applied to a variable magnetic inductance current sensor as described in any one of the first aspects; the method comprises: applying an excitation voltage to the overcurrent detection inductor element to generate an excitation current; obtaining the excitation current value of the overcurrent detection inductor element at at least one acquisition moment under the action of the magnetic field of the current to be measured; and detecting whether the current to be measured is overcurrent based on the excitation current value.

[0018] As described above, a variable magnetic inductance current sensor and an overcurrent detection method thereof are provided in an embodiment of the present disclosure, wherein the current sensor comprises: an overcurrent detection inductor element, which generates a first excitation current in response to an applied first excitation voltage, wherein the first excitation current forms a first excitation magnetic field; and an overcurrent detection circuit, which is used to determine whether the current to be measured is overcurrent based on the frequency and / or amplitude of the first excitation current related to the change in the inductance value of the overcurrent detection inductor element; wherein the overcurrent detection inductor element is arranged so that the direction of the normal of its cross section deviates from a preset angle relative to the magnetic field direction of the magnetic field of the current to be measured generated by the current to be measured, so as to set the effective cross-sectional area of ​​the overcurrent detection inductor element to receive the magnetic flux lines of the magnetic field of the current to be measured, so that the maximum current to be measured that the overcurrent detection inductor element can be used to detect is greater than the rated current, and the multiple relationship of the maximum current to be measured relative to the rated current is determined by the preset angle.

[0019] Therefore, by adjusting the angle of the overcurrent detection inductor, the maximum current to be measured that is a multiple of the rated current can be detected, which is very suitable for short-circuit current detection caused by thermal runaway of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A A schematic diagram showing the structure of a solenoid coil in which the inductor element is an embodiment of the present disclosure.

[0021] Figure 1B A schematic diagram showing the structure of a planar coil in an embodiment of the present disclosure in which the inductor element is provided.

[0022] Figure 2 A schematic structural diagram of a VMI current sensor in an embodiment of the present disclosure is shown.

[0023] Figure 3 A waveform diagram of a pulse voltage signal and a corresponding excitation current signal generated by a pulse signal in an embodiment is shown.

[0024] Figure 4 A schematic structural diagram of a VMI current sensor in an embodiment of the present disclosure is shown.

[0025] Figure 5 exhibit Figure 4 Schematic diagram of the waveforms of the excitation pulse, LC oscillation signal, and current signal to be measured corresponding to the embodiment.

[0026] Figure 6 A schematic diagram showing the arrangement principle of over-current detection using an inductive element in one embodiment of the present disclosure.

[0027] Figure 7 A schematic structural diagram of a VMI current sensor in an embodiment of the present disclosure is shown.

[0028] Figure 8 A schematic diagram showing the structure of an overcurrent detection excitation circuit in one embodiment of the present disclosure is shown.

[0029] Fig. 9 A schematic diagram showing a waveform of two pulse signals of the same frequency but with a phase difference and current amplitude change information generated by the two pulse signals in one embodiment of the present disclosure.

[0030] Fig.10 exhibit Figure 8 A schematic circuit diagram of an embodiment of an overcurrent detection excitation circuit.

[0031] Fig.11 A schematic diagram showing the circuit principle of a differential operation circuit in an embodiment of the present disclosure is shown.

[0032] Fig.12 A schematic diagram showing the circuit structure of an overcurrent detection circuit in an embodiment of the present disclosure is shown.

[0033] Fig.13 exhibit Fig.12 A circuit schematic diagram of an implementation example of an overcurrent detection circuit.

[0034] Fig.14 A flow chart showing an overcurrent detection method in an embodiment of the present disclosure.

[0035] Reference numerals:

[0036] Solenoid coil 100A; Planar coil 100B;

[0037] VMI current sensor 200; inductor element 201; first excitation circuit 202; first processing unit 203; conductor to be measured 300;

[0038] Inductor element 401; second excitation circuit 402; second processing unit 403; capacitor element 404;

[0039] Inductor element 601;

[0040] Overcurrent detection inductor element 701; overcurrent detection circuit 702; overcurrent detection excitation circuit 703; measurement inductor element 704; measurement excitation circuit 705; third processing unit 706;

[0041] First conductive loop 803; second conductive loop 804; switch group 805; common line 806; first resistor 807; output terminals 808, 809;

[0042] A first comparator 1201 ; a second comparator 1202 ; or a logic operation unit 1203 . DETAILED DESCRIPTION

[0043] The following is an explanation of the embodiments of the present disclosure by specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the information disclosed by the present disclosure. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in the present disclosure can also be modified or changed in various ways according to different viewpoints and application modules without departing from the spirit of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0044] The following is a detailed description of the embodiments of the present disclosure with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. The present disclosure can be embodied in many different forms and is not limited to the embodiments described herein.

[0045] In the representations of the present disclosure, the reference terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" and the like mean that the specific features, structures, materials or characteristics represented in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. Moreover, the specific features, structures, materials or characteristics represented may be combined in any one or a group of embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples represented in the present disclosure and the features of different embodiments or examples, unless they are mutually contradictory.

[0046] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the representation of the present disclosure, "a group" means two or more, unless otherwise clearly and specifically defined.

[0047] In order to clearly describe the present disclosure, components not related to the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

[0048] Throughout the specification, when a device is said to be "coupled" to another device, this includes not only the case of "direct coupling" but also the case of "indirect coupling" by placing other elements therebetween. In addition, when a device is said to "include" a certain constituent element, unless otherwise stated, it does not exclude other constituent elements, but means that other constituent elements may be included.

[0049] Although the terms first, second, etc. are used to represent various elements in this article in some examples, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, the first interface and the second interface, etc. are represented. Moreover, as used in this article, the singular forms "one", "one" and "the" are intended to also include plural forms, unless there is an opposite indication in the context. It should be further understood that the terms "comprising" and "including" indicate that there are the described features, steps, operations, elements, modules, projects, kinds, and / or groups, but do not exclude the existence, occurrence or addition of one or a group of other features, steps, operations, elements, modules, projects, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". Only when the combination of elements, functions, steps or operations is inherently mutually exclusive in some way, will there be an exception to this definition.

[0050] The technical terms used herein are only used to refer to specific embodiments and are not intended to limit the present disclosure. The singular form used herein also includes the plural form unless the sentence clearly indicates the contrary meaning. The meaning of "including" used in the specification is to specify specific characteristics, regions, integers, steps, operations, elements and / or components, and does not exclude the existence or addition of other characteristics, regions, integers, steps, operations, elements and / or components.

[0051] Although not defined differently, all terms, including technical and scientific terms used herein, have the same meaning as those generally understood by those skilled in the art to which the present disclosure belongs. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with relevant technical literature and the message of the present disclosure, and shall not be overly interpreted as ideal or very formal meanings unless defined.

[0052] Current sensors are used in many scenarios, but traditional types of current sensors have certain problems. For example, the most widely used Hall effect sensor usually uses a large U-shaped or C-shaped iron core to concentrate the magnetic flux generated by the current to be measured, and the sensor volume is often large. In addition, fluxgate type measurement devices also need to use large and heavy magnetic cores, and fluxgate type measurement devices have high power consumption required to excite the fluxgate secondary. In addition, for example, xMR type current measurement devices are built around one or more magnetoresistive elements. On the one hand, the assembly of magnetoresistive elements is complex, and on the other hand, this type of current measurement device needs to implement a Wheatstone bridge, which is easily affected by the skin effect, and will cause significant measurement errors in the case of large currents.

[0053] In addition, the overcurrent detection method of sensors using the principles of fluxgate current sensors, Hall effect sensors, shunts, etc. is generally to increase the range by 20% on the basis of the rated current for overcurrent detection. The range is small, which is not conducive to the situation where the detected current may reach several times the rated current in some current sensor scenarios. For example, in the battery management system, the short-circuit current of 5 times the rated current or even higher is detected due to the short-circuit failure of the battery pack.

[0054] In view of the above problems, a variable magneto-inductor (VMI) current sensor is provided in an embodiment of the present disclosure to solve the above problems.

[0055] The principle of the VMI current sensor for measuring the current to be measured is briefly introduced.

[0056] The VMI current sensor includes at least one inductive element, which may include any element with inductive properties including a coil. As an example, the inductive element may be Figure 1A The spirally wound solenoid coil 100A shown may also be Figure 1B A helically wound planar coil 100B is shown.

[0057] When voltage is applied to both ends of the line, a current can flow through the inductor, and the current will form a magnetic field. Taking the coil as an example, according to Ampere's law, when the right hand holds the coil, the four fingers point to the direction of the current, and the thumb points to the direction of the magnetic field generated by the current (pointing to the N pole). Or, when the right hand holds a straight current, the thumb points to the direction of the current, and the four fingers point to the direction of the magnetic field generated by the current. Figure 1A Taking the solenoid coil as an example, the direction of its magnetic field is consistent with the direction of its axis.

[0058] Based on physical knowledge, we know that the characteristic formula of inductance is:

[0059] U=L*di / dt(1)

[0060] Among them, U is the voltage across the inductor, L is the inductance, and di / dt represents the derivative of current with respect to time, which can be understood as the rate of change of current with time.

[0061] And, the inductance of the coil is calculated as:

[0062] L=μN 2 S / l (2)

[0063] Where L is the inductance, μ is the magnetic permeability, N is the number of turns in the coil, S is the cross-sectional area of ​​the coil, and l is the length of the coil.

[0064] When the electromagnet formed by the inductor is energized and located next to the external conductor, if the external magnetic field generated by the external current I flowing through the external conductor couples with the magnetic field generated by the inductor current, the magnetic permeability μ of the electromagnet will change. The magnetic permeability μ is the ratio of the magnetic induction intensity B to the magnetic field intensity H at a certain point in the magnetic field, that is, the slope in the hysteresis (BH) curve. The magnetic permeability μ does not change monotonically with the changes in B and H, but rises and falls.

[0065] Based on formula (2), it can be seen that the change of magnetic permeability μ will cause the change of inductance L. In formula (1), if the voltage value U applied across the inductor is fixed, the change of L will cause a corresponding change in di / dt, which can be expressed by the slope of i that is approximately linear in a very short time slot in the two-dimensional coordinate system of current-time.

[0066] It can be seen that there is a correlation between di / dt and I. If the correlation can be obtained, such as a relationship function or a relationship table, the corresponding current value to be measured can be obtained by measuring di / dt. This method is called the "di / dt method".

[0067] Based on the above principles, Figure 2 A schematic structural diagram of a VMI current sensor in an embodiment of the present disclosure is shown.

[0068] The VMI current sensor 200 includes: an inductor element 201, a first excitation circuit 202, and a first processing unit 203. Each of the inductor elements 201 may include a coil, such as a solenoid coil.

[0069] The first excitation circuit 202 is coupled to the inductor element 201 , and is used for applying a pulse voltage (V) to the inductor element 201 in response to a pulse signal to generate an excitation current on the inductor element 201 .

[0070] exist Figure 2 In the embodiment, the measured current flows through the measured conductor 300, and the measured current forms a measured current magnetic field. The magnetic field direction of the inductor 201 is exemplarily set to be parallel to the magnetic field direction of the measured current magnetic field.

[0071] Regarding the relationship between the pulse voltage signal and the excitation current signal, it can be seen that Figure 3 , showing a waveform diagram of a pulse voltage signal and a corresponding excitation current signal generated by a pulse signal in an example. It should be particularly noted that although the pulse signal, the pulse voltage signal and the excitation current signal in the figure have the same frequency and consistent phase, this is only an example, and in other embodiments, they can be adjusted to be different according to needs, and are not limited to the example.

[0072] exist Figure 3In the case of a pulse signal, when the rising edge of the pulse signal arrives, the trigger excitation circuit outputs a pulse voltage applied to the inductor, and an increasing excitation current is formed on the inductor. As mentioned earlier, in a very short period of time (determined by the pulse width of the pulse voltage, such as a few microseconds from the rising edge of the pulse, such as 3 microseconds), the rate of change of the excitation current is approximately linearly rising, and when the falling edge of the pulse voltage arrives, the excitation current value changes to 0, so that the waveform of the current changing with time presents a sawtooth shape, and the "slope" of each sawtooth wave corresponds to di / dt. Under the action of the magnetic field of the current to be measured, if the decrease in magnetic permeability causes L to decrease, then di / dt increases, showing an increase in the slope of a certain sawtooth; conversely, if the increase in magnetic permeability causes L to increase, then di / dt decreases, showing a decrease in the slope of a certain sawtooth. Three sawtooth patterns A, B and C can be seen in the figure. A may be the initial state without the measured current magnetic field of the measured conductor 300, that is, it shows the initial di / dt change rate. B is the state in which di / dt increases under the action of the measured current magnetic field. C is the state in which di / dt decreases under the action of the measured current magnetic field.

[0073] It can be seen from this that the excitation current signal can be used to extract current amplitude change information, that is, information related to di / dt of the excitation current.

[0074] Back to Figure 2 , the first processing unit 203 is coupled to the first excitation circuit 202, and is used to output a pulse signal to the first excitation circuit 202, and obtain current amplitude change information, so as to determine the current value to be measured associated with the current amplitude change information according to preset association information. The preset association information is pre-obtained based on a plurality of groups of sampling values ​​through mathematical fitting, and each group of the sampling values ​​includes current amplitude change information and its associated current value of the preset current to be measured. The current amplitude change information can be directly collected by the first excitation circuit 202, or the first excitation circuit 202 can send at least one current amplitude change signal to be extracted by the first processing unit 203, or the circuit between the first processing unit 203 and the first excitation circuit 202.

[0075] In some embodiments, the first processing unit 203 may be implemented based on, for example, a microcontroller unit (MCU), a system on chip (SoC), or a field programmable gate array (FPGA). In some embodiments, the preset association information may be a relationship function or a relationship table, which is pre-marked in the first processing unit 203 .

[0076] It can be understood that the "di / dt method" uses the rate of change of the "amplitude" of the excitation current to reflect the change in the inductance of the inductor element, thereby using the change in di / dt to infer the current value of the current to be measured that causes the change in di / dt. In other embodiments, the "frequency" of the excitation current can also be used to reflect the change in the inductance of the inductor element, so as to calculate the value of the current to be measured by using the relationship between the frequency and the current to be measured. The method of calculating the value of the current to be measured by the "frequency" of the excitation current can be called the "frequency method".

[0077] In other embodiments, reference may be made to Figure 4 As shown, an inductor 401 is connected in parallel with a capacitor 404 (can also be connected in series) to form an LC oscillation circuit (so that the excitation current has a set "frequency"). The current to be measured flows through the conductor 300 to form a magnetic field of the current to be measured that acts on the inductor 401. The inductor 401 is electrically connected to a second excitation circuit 402. The second excitation circuit 402 is used to apply an excitation voltage to the inductor 401 in response to a pulse signal, so that an excitation current in the form of an oscillating wave is generated on the inductor 401. The waveforms of the pulse signal, the LC oscillation signal, and the current to be measured can be shown as follows: Figure 5 Indicates.

[0078] Schematically, the magnetic field direction of the inductor 401 may be parallel to the magnetic field direction of the current magnetic field to be measured generated by the current to be measured on the conductor to be measured. The second excitation circuit 402 may be coupled to a second processing unit 403, and the second processing unit 403 may provide a pulse signal for the excitation circuit, and obtain the excitation current of the inductor after being affected by the magnetic field of the current to be measured, so as to calculate the value of the current to be measured. In some embodiments, the second processing unit 403 may be implemented based on, for example, a microcontroller unit (MCU), a system on chip (SoC), or a field programmable gate array (FPGA).

[0079] The following is a brief explanation of the principle:

[0080] Induced electromotive force formula:

[0081] ;

[0082] Combined with Faraday's law, we can get:

[0083]

[0084] Combining the linear relationship between electromotive force and inductance and the calculation formula of LC oscillation frequency, it can be determined that:

[0085] (3)

[0086] Where L vis the inductance value of the inductor element 401 after being mutually inducted by the magnetic field of the current to be measured;

[0087] N is the number of turns of the inductor element 401;

[0088] ΔI excit is the excitation current value at the corresponding moment.

[0089] is the magnetic flux of the current magnetic field to be measured.

[0090] According to formula (3), we can get formula (4):

[0091] (4)

[0092] And by the magnetic flux formula:

[0093]

[0094] And from Ampere's law:

[0095] , we can get:

[0096] (5)

[0097] Among them, I p is the current to be measured; S corresponds to the effective cross-sectional area of ​​the inductor element 401 through which the magnetic flux lines of the magnetic field of the current to be measured pass. Since the magnetic field directions of the inductor element 401 and the magnetic field of the current to be measured are parallel, that is, the normal direction of the cross section of the solenoid coil is parallel to the magnetic field direction of the current to be measured, the entire cross-sectional area S of the inductor element 401 is used as the effective cross-sectional area.

[0098] Combining equation (5) with equation (3), we can get the oscillation frequency f and the measured current I p The mathematical relationship between .

[0099] The oscillation frequency f and the measured current I p There is a monotonic correlation between them, for example, a positive correlation. Figure 5 It can be seen that when the current to be measured I p As it increases, the oscillation frequency f will also increase accordingly, that is, the waveform tends to become narrower.

[0100] In the method of calculating the current to be measured based on the "amplitude" or "frequency" of the excitation current of the above inductor element, the inductor element is exemplarily placed so that the magnetic field direction is parallel to the magnetic field direction of the current to be measured. In the overcurrent detection scheme disclosed in the present invention, by placing the inductor element so that the magnetic field direction and the magnetic field direction of the current to be measured have a preset angle, the overcurrent to be measured that exceeds the preset multiple relationship of the rated current can be detected. The multiple relationship can be set by the preset angle.

[0101] In addition, it should be noted that the first excitation circuit 202 and the second excitation circuit 402 in the previous embodiment may include a conductive loop having a switch element (such as a MOS switch) controlled by the pulse signal, and the corresponding inductance elements 201 and 401 are connected in series in their respective conductive loops. When the pulse signal turns on the switch element, the conductive loop is turned on so that an excitation voltage is applied to both ends of the inductance elements 201 and 401, generating an excitation current. Figure 2 The difference is, Figure 4 The second inductor element in the circuit can also be connected in parallel (or in series) with a capacitor to form an LC oscillation circuit.

[0102] The principle of over-current detection using an inductor element is first explained using the embodiment of the above formula (5).

[0103] exist Figure 6 In the figure, an inductor 601 is shown. The inductor 601 is exemplified as a solenoid coil. The inductor 601 is arranged so that the direction of the normal line of its cross section deviates from the magnetic field direction of the current to be measured generated by the current to be measured by a preset angle. Figure 4 visible, Figure 6 The effective cross-sectional area S of the magnetic flux lines of the inductor element 601 that actually receives the magnetic field of the current to be measured is 有效 There has been a change, S 有效= S1*cosα, S1 is the cross-sectional area of ​​the inductor, and α is the preset angle. For the convenience of comparison with the coil cross-sectional area S in the previous example, S1=S can be set, then S 有效= S*cosα.

[0104] S 有效 =S*cosα, α is the preset angle, S is the cross-sectional area of ​​the inductor element; r can be used as the distance between the conductor to be measured of the current to be measured and the inductor element.

[0105] Therefore, compared with formula (5), Figure 6 Corresponding to formula (6):

[0106] (6)

[0107] It can be seen that S

[0108] 有效

[0109] = Scosα is reduced compared to S, so the maximum current to be measured that can be detected is expanded. When the rated current to be measured is set to In, the maximum current to be measured that the inductor can detect is I

[0110] pmax

[0111] =In / cosα. Since -1≤cosα≤1, 1 / cosα enables the maximum detectable current to be much higher than the rated current value, thereby realizing the detection of overcurrent values ​​that are multiple times the rated current value.

[0112] Taking the “di / dt method” in the previous embodiment as an example, if an excitation circuit is connected to the inductor element 601, an excitation current with a sawtooth waveform is generated.

[0113] From Ampere's circuit law we know that:

[0114] (7)

[0115] (8)

[0116] Moreover, the magnetic induction intensity of the current magnetic field to be measured in the inductor is:

[0117] (9)

[0118] Still set S 有效= S*cosα, so the magnetic flux generated by the magnetic field of the current to be measured in the inductor is:

[0119] (10)

[0120] The magnetic induction intensity generated by the excitation current magnetic field is:

[0121] (11)

[0122] The magnetic flux generated by the excitation current magnetic field is:

[0123] (12)

[0124] The total magnetic flux of the inductor element is:

[0125] (13)

[0126] The magnetic flux density can be obtained as:

[0127] (14)

[0128] According to the definition of μ=B / H, we can get:

[0129] (15)

[0130] According to the above derivation, we can get H and I pcosα; and in the μH curve, H will cause μ to change, which will cause the inductance to change, and then cause di / dt to change. Therefore, the relationship between di / dt and the preset angle α can be obtained, so that the "di / dt method" can also be used to determine whether the current value to be measured that may be greater than the rated current is overcurrent.

[0131] like Figure 7 As shown, a schematic diagram of the structure of a VMI current sensor in an embodiment of the present disclosure is shown.

[0132] The VMI current sensor includes: an overcurrent detection inductor element 701, an overcurrent detection circuit 702, etc.

[0133] The overcurrent detection inductor element 701 generates a first excitation current in response to an applied first excitation voltage, and the first excitation current forms a first excitation magnetic field. The overcurrent detection inductor element 701 is placed so that the direction of the normal line of its cross section deviates from a preset angle (represented by α) relative to the magnetic field direction of the magnetic field of the current to be measured generated by the current to be measured, so as to set the effective cross-sectional area of ​​the magnetic flux lines of the magnetic field of the current to be measured received by the overcurrent detection inductor element 701, so that the maximum current to be measured that the overcurrent detection inductor element 701 can be used to detect is greater than the rated current, and the multiple relationship of the maximum current to be measured to the rated current is determined by the preset angle. The overcurrent detection inductor element 701 can be exemplified as a solenoid coil, and its placement method can refer to Figure 6 The inductor element 601 in FIG.

[0134] Exemplarily, the overcurrent detection inductor element 701 may be coupled to an overcurrent detection excitation circuit 703. The overcurrent detection excitation circuit 703 is used to apply the first excitation voltage to the overcurrent detection inductor element 701 in response to a pulse signal to generate a first excitation current. In some embodiments, the overcurrent detection excitation circuit 703 may output a current amplitude change signal related to the amplitude of the first excitation current, such as an excitation voltage signal between two ends of the overcurrent detection inductor element 701, and the amplitude change of the first excitation current may be converted into an excitation voltage amplitude change.

[0135] The overcurrent detection circuit 702 is used to determine whether the current to be measured is overcurrent based on the frequency and / or amplitude of the first excitation current related to the change in the inductance value of the overcurrent detection inductor 701. In some embodiments, referring to the principles in the examples of the "frequency method" or the "di / dt method" in the previous embodiments, the overcurrent detection circuit can have different implementations for different current detection methods.

[0136] For example, in some embodiments, taking the “frequency method” as an example, the overcurrent detection circuit 702 can be integrated in the processing unit to implement the frequency and I in formula (6).p The monotonic relationship between them shows that when I p When there is overcurrent, there will be a corresponding f reaching the frequency threshold. Therefore, the overcurrent detection circuit 702 can determine whether there is overcurrent by determining whether f reaches the frequency threshold.

[0137] Thus, in the embodiment using the "frequency method", the overcurrent detection circuit 702 is used to determine whether the current to be measured is overcurrent based on detecting whether the oscillation frequency of the LC oscillation circuit reaches a preset frequency threshold. The preset frequency threshold is determined based on the mathematical relationship between the current to be measured and the oscillation frequency (which can be determined by equations (6) and (3)), the rated value (In) of the current to be measured, and the preset angle (α).

[0138] For another example, in some other embodiments, taking the "di / dt method" as an example, a current amplitude change threshold value related to the rate of change of the amplitude of the first excitation current over time can be set, and the current amplitude change threshold value can correspond to an overcurrent value that is a multiple (for example, from 1 / cosα) of the original rated current. By judging whether the "di / dt" related current amplitude change information (such as the excitation voltage amplitude change rate) reaches the current amplitude change threshold value, it is judged whether there is an overcurrent. The overcurrent detection circuit 702 can be located outside the processing unit, coupled between the overcurrent detection excitation circuit 703 and the processing unit (not shown), and the current amplitude change information is obtained according to the current amplitude change signal output by the overcurrent detection excitation circuit 703, and by judging whether the current amplitude change information reaches the current amplitude change threshold value, it is determined whether the current to be measured is overcurrent.

[0139] In an embodiment using the "di / dt method", the overcurrent detection excitation circuit and the overcurrent detection circuit may be configured to perform the following functions.

[0140] The overcurrent detection excitation circuit 703 is coupled to the overcurrent detection inductor element 701, and is used to apply an excitation voltage to the overcurrent detection inductor element in response to a pulse signal to generate an excitation current signal, and to lead out at least one output terminal in the conductive loop where the overcurrent detection inductor element 701 is located, and is used to output at least one current amplitude change signal related to the rate of change of the excitation current over time, such as a voltage amplitude change signal, etc. The at least one current amplitude change signal is used to obtain current amplitude change information, that is, a signal representation of di / dt.

[0141] The overcurrent detection circuit 702 is used to obtain the current amplitude change information and compare the current amplitude change information with the current amplitude change thresholds corresponding to two magnetic field directions to determine whether the current to be measured corresponding to the current amplitude change information is overcurrent.

[0142] In some embodiments, the overcurrent detection inductor element 701 is configured to alternately form an excitation current magnetic field with opposite magnetic field directions over time, for example, the overcurrent detection inductor element is periodically applied with an excitation voltage of opposite polarity to generate an excitation current in the opposite direction, and the corresponding magnetic field direction is also opposite. Accordingly, the overcurrent detection excitation circuit 703 outputs a pair of current amplitude change signals based on two signal points in the conductive loop where the overcurrent detection inductor element 701 is located, and the pair of current amplitude change signals are respectively related to the excitation currents that form the excitation current magnetic field with opposite magnetic field directions.

[0143] In the corresponding example, the variable magnetic inductance current sensor may further include a differential operation circuit for obtaining current amplitude change information based on the differential calculation of the pair of current amplitude change signals. On the one hand, the differential calculation of a pair of current amplitude change signals can eliminate the interference that a single current amplitude change signal may be subject to; on the other hand, the differential calculation of a pair of current amplitude change signals in opposite excitation current directions can obtain a signal representation of twice di / dt, which is more conducive to the accuracy of detection.

[0144] like Figure 8 As shown, a schematic diagram of the structure of an overcurrent detection excitation circuit in an embodiment of the present disclosure is shown. The overcurrent detection excitation circuit can periodically apply an excitation voltage of opposite polarity to the overcurrent detection inductor element. The overcurrent detection excitation circuit includes:

[0145] A first conductive loop 803 , a second conductive loop 804 , and a switch group 805 .

[0146] The first conductive loop 803 and the second conductive loop 804 are configured to have a common line 806 , and the over-current detection inductor element 701 is disposed in the common line 806 .

[0147] The switch group 805 can be arranged in the first conductive loop 803 and the second conductive loop 804, and the switch state is set by two pulse signals (PULSE1, PULSE2) of the same frequency and with a phase difference to alternately turn on / off the first conductive loop 803 and the second conductive loop 804; wherein, when the first conductive loop 803 and the second conductive loop 804 are turned on, voltages of opposite polarities are applied to both ends of the common line 806 to form excitation currents of opposite directions in the one overcurrent detection inductor element.

[0148] The first resistor 807 is arranged in series with the overcurrent detection inductor 801 in the common line 806; two signal points formed at both ends of the first resistor 807 lead to a pair of output terminals 808 and 809 to output a pair of electrical signals as the pair of current amplitude change signals.

[0149] The waveforms of PULSE1 and PULSE2 can be exemplarily referred to Fig. 9 As shown. When the levels of PULSE1 and PULSE2 are opposite, the first conductive loop 803 or the second conductive loop 804 can be turned on to form opposite excitation currents on the overcurrent detection inductor element 701 respectively; conversely, when the levels are the same, the first conductive loop 803 and the second conductive loop 804 are not turned on, that is, no excitation current is generated. The characteristics of the excitation currents in two directions can be captured by a pair of voltage signals at both ends of the first resistor 807, and the pair of voltage signals can be further differentiated by a differential operation circuit to obtain the voltage difference in one direction across the first resistor 807 as the current amplitude change information, Fig. 9 The signal waveform of the voltage difference obtained by subtracting the voltage value of the output terminal 809 from the voltage value of the output terminal 808 is also drawn in the figure. The sign of the voltage difference can indicate the direction of the excitation current.

[0150] More specifically, Fig.10 Shown, displayed Figure 8 A schematic circuit diagram of an embodiment of an overcurrent detection excitation circuit.

[0151] The switch group includes: a first switch Q12, a second switch Q11, a third switch Q14 and a fourth switch Q13. Q12 and Q14 are PMOS, Q11 and Q13 are NMOS, and illustratively, their first terminals are drains, their second terminals are sources, and their third terminals are gates.

[0152] The first end of the first switch Q12 is coupled to the power source VCC, the second end of the first switch Q12 is coupled to the first end of the second switch Q11 and leads to the first common terminal A, and the second end of the second switch Q11 is coupled to the ground. The third ends of the first switch Q12 and the second switch Q11 for setting the first end and the second end to be on / off receive a first pulse signal PULSE1, and the first switch Q12 and the second switch Q11 are in opposite switch states under the action of the first pulse signal PULSE1.

[0153] The first end of the third switch Q14 is coupled to the power supply VCC. Optionally, the first ends of the first switch Q12 and the third switch Q14 may also be grounded via a capacitor C16. The second end of the third switch Q14 is coupled to the first end of the fourth switch Q13 and leads to a second common terminal B, and the second end of the fourth switch Q13 is coupled to the ground. The third ends of the third switch Q14 and the fourth switch Q13, which are used to set the first end and the second end to be on / off, receive a second pulse signal PULSE2, and the third switch Q14 and the fourth switch Q13 are in opposite switching states under the action of the second pulse signal PULSE2. The first pulse signal and the second pulse signal have the same frequency and a phase difference, for example: Fig. 9shown.

[0154] Figure 6 , Figure 7 The over-current detection inductor elements 601 and 701 in Fig.10 The inductor element L5 can be implemented in the circuit. One end of L5 is coupled to the first common terminal A, and the other end is coupled to the second common terminal B through the resistor R42 to form a common line between the first common terminal A and the second common terminal B. A pair of output terminals O1 and O2 are led out from both ends of the resistor R42 to output a pair of current amplitude change signals for differential operation to obtain current amplitude change information. The first switch Q12 and the fourth switch Q13 have the same switch state, and are connected through a common line to form the first conductive loop. The second switch Q11 and the third switch Q14 have the same switch state, and are connected through a common line to form the second conductive loop.

[0155] like Fig.11 , which is a schematic diagram showing the circuit principle of a differential operation circuit in an embodiment of the present disclosure.

[0156] The differential operation circuit can be implemented based on an operational amplifier. Fig.11 The components shown include: Operational amplifier

[0157] U0, resistor R43, resistor R44, resistor R45, resistor R46, capacitor C17.

[0158] The operational amplifier U0 includes a negative input terminal, a positive input terminal, and an output terminal. The negative input terminal leads to the input terminal I1 through R44, and the positive input terminal leads to the output terminal I2 through R45. The first input terminal and the second input terminal are respectively connected to Fig.10 A pair of output terminals O1 and O2 are connected to input a pair of current amplitude change signals. U0 performs differential calculation on a pair of current amplitude change signals to obtain current amplitude change information. Optionally, the positive input terminal can also be connected to the reference setting terminal via resistor R46 for introducing the bias signal BIAS_SET. BIAS_SET adds a bias voltage (for example, +2.5V) to raise the output voltage value I_OCD of the output terminal. Both ends of R43 are respectively connected to the negative input terminal and the output terminal, serving as a reference resistor in a preset ratio with R44. In addition, the power supply terminal and the ground terminal of the operational amplifier U0 are respectively connected to the power supply (VCC) and the ground, and its power supply terminal is also exemplarily connected to the ground via capacitor C17.

[0159] like Fig.12 As shown, a circuit structure diagram of an overcurrent detection circuit in an embodiment of the present disclosure is shown.

[0160] exist Fig.12 In the embodiment, the overcurrent detection circuit comprises:

[0161] The first comparator 1201 outputs a first comparison result of the current amplitude change information and a first current amplitude change threshold corresponding to a magnetic field direction; wherein, when the current amplitude change information is higher than the first current amplitude change threshold, the first comparison result is a signal value indicating overcurrent, such as a high level 1.

[0162] The second comparator 1202 outputs a second comparison result of the current amplitude change information and a second current amplitude change threshold corresponding to another opposite magnetic field direction; wherein, when the current amplitude change information is lower than the second current amplitude change threshold, the second comparison result is a signal value indicating overcurrent.

[0163] The OR logic operation unit 1203 has two input terminals coupled to the output terminals of the first comparator 1201 and the second comparator 1202, and an output terminal outputs the OR logic operation result of the two inputs as the final result indicating whether the current to be measured is overcurrent.

[0164] like Fig.13 Shown, displayed Fig.12 A circuit schematic diagram of an implementation example of an overcurrent detection circuit.

[0165] exist Fig.13 In the embodiment, the overcurrent detection circuit includes: a comparator U1 and another comparator U2 implemented by an operational amplifier; resistors R47, R48, R49 and R50; and diodes D1 and D2.

[0166] The positive input terminal of the comparator U1 can receive current amplitude change information input, for example, coupled to Fig.11 The output end of the differential operation circuit receives the I_OCD input. One end of the resistor R47 is coupled to VCC, the other end of R47 and one end of the resistor R48 are coupled to form a first voltage dividing point, and the other end of R48 is coupled to ground to form a resistor voltage dividing circuit. The first voltage dividing point is connected to the negative input end of U1 to output the divided voltage OCDSET+. The output end of U1 outputs the comparison result OCD+ of I_OCD and OCDSET+. When I_OCD>OCDSET+, it indicates an overcurrent in one current direction, and OCD+ is a high level "1"; otherwise, a low level "0" is output.

[0167] The negative input terminal of the comparator U2 can receive current amplitude change information input, for example, coupled to Fig.11The output terminal of the middle differential operation circuit receives the I_OCD input. One end of resistor R49 is coupled to VCC, the other end of R49 and one end of resistor R50 are coupled to form a second voltage division point, and the other end of R50 is coupled to ground to form a resistor voltage division circuit. The second voltage division point is connected to the positive input terminal of U2 to output the voltage division voltage OCDSET-. The output terminal of U2 outputs the comparison result OCD- of I_OCD and OCDSET-. When I_OCD < OCDSET-, it indicates overcurrent in one current direction, and OCD- is at a high level "1"; otherwise, a low level "0" is output.

[0168] The positive electrode of diode D1 is coupled to the output terminal of U1, and the negative electrode of diode U2 is coupled to the output terminal of U2; the negative electrodes of D1 and D2 are coupled to the output terminal of the overcurrent detection circuit to output the signal OCD.

[0169] When the outputs of both U1 and U2 are 0, both D1 and D2 are cut off, and OCD is at a low level 0, indicating no overcurrent; when the output of U1 is 1 and the output of U2 is 0, D1 conducts while D2 is cut off, and OCD is at a high level indicating overcurrent; when the output of U1 is 1 and the output of U2 is 0, D2 conducts while D1 is cut off, and OCD is at a high level indicating overcurrent. It can be seen that D1 and D2 implement an OR logic operation unit.

[0170] Exemplarily, OCDSET+ is 4.5V and OCDSET- is 0.5V, that is, I_OCD > 4.5V or < 0.5V indicates overcurrent.

[0171] This result is obtained considering the elevated bias voltage of BIAS_SET. If there is no bias voltage, then OCDSET+ is 2V and OCDSET- is -2V. The signs represent opposite excitation current directions, which also correspond to opposite magnetic field directions.

[0172] In some embodiments, in addition to the overcurrent detection inductive element, the V.M.I. current sensor may further include at least one measuring inductive element for normally detecting the current to be measured. Back to Figure 7 As shown, Figure 7A measuring inductance element 704 is shown. Alternatively, in other embodiments, the number of the measuring inductance elements may be multiple (for example, a pair), but is not limited thereto. The measuring inductance element 704 generates a second excitation current in response to a second excitation voltage applied by the measured excitation circuit 705, and the second excitation current forms a second excitation magnetic field. When the second excitation magnetic field is affected by the magnetic field of the current to be measured, the inductance value of the measuring inductance element 704 changes for calculating the current to be measured. The measuring inductance element 704 is placed so that the normal direction of its cross section is parallel to the magnetic field direction of the magnetic field of the current to be measured. The measuring inductance element 704 can be connected to a capacitor to calculate the current to be measured by a frequency method, or to measure the current by a "di / dt" method. Optionally, the measurement excitation circuit 705 can be coupled to a third processing unit 706, and the third processing unit 706 is coupled to the overcurrent detection excitation circuit 703 and the measurement excitation circuit 705 to provide an excitation pulse signal to form an excitation current in the overcurrent detection inductor element 701 and the measurement inductor element 704, and is also coupled to or integrated with the overcurrent detection circuit 702 to obtain an overcurrent detection result, or calculate the overcurrent detection result based on the excitation current signal.

[0173] In some embodiments, the measuring inductance element 704 may also be implemented as a solenoid coil, and its configuration parameters (such as cross-sectional area, length, etc.) may be the same as those of the overcurrent detection inductance element 701. Alternatively, the parameters may be different. For example, the measuring inductance element 704 and the overcurrent detection inductance element 701 are solenoid coils with different cross-sectional areas. However, as long as the parameters are known in advance, corresponding calculations can be performed, such as measuring the current to be measured, determining whether there is an overcurrent, etc., so there is no need to limit whether the measuring inductance element 704 and the overcurrent detection inductance element 701 are the same. Of course, when the same solenoid coil is used, the device selection and implementation of the VMI current sensor can be facilitated.

[0174] In some embodiments, the number of the measuring inductance element 704 can be a pair or one, and one is exemplarily shown in the figure. For example, a pair of measuring inductance elements are configured so that the magnetic fields formed by the second excitation magnetic fields are opposite in direction; or a measuring inductance element is configured to alternately form second excitation magnetic fields with opposite magnetic fields in direction over time. With reference to the previous embodiments, the current to be measured can be calculated by using the "di / dt method" or "frequency method" in combination with corresponding excitation circuits, differential operation circuits, processing units, etc. The applicant has described it in detail in the patent application previously submitted, and will not elaborate on it here.

[0175] like Fig.14As shown, a flow chart of an overcurrent detection method in an embodiment of the present disclosure is shown. The overcurrent detection method can be applied to the variable magnetic inductance current sensor including an overcurrent detection inductor element and an overcurrent detection circuit in the previous embodiment. The overcurrent detection method includes:

[0176] Step S1401: applying an excitation voltage to the overcurrent detection inductor element to generate an excitation current.

[0177] Step S1402: obtaining an excitation current value of the overcurrent detection inductor element at at least one acquisition moment under the action of the magnetic field of the current to be measured; and detecting whether the current to be measured is overcurrent based on the excitation current value.

[0178] In summary, the present disclosure provides a variable magnetic inductance current sensor and an overcurrent detection method thereof, wherein the current sensor comprises: an overcurrent detection inductor element, which generates a first excitation current in response to an applied first excitation voltage, wherein the first excitation current forms a first excitation magnetic field; an overcurrent detection circuit, which is used to determine whether the current to be measured is overcurrent based on the frequency and / or amplitude of the first excitation current related to the change in the inductance value of the overcurrent detection inductor element; wherein the overcurrent detection inductor element is placed so that the direction of the normal line of its cross section deviates from a preset angle relative to the magnetic field direction of the magnetic field of the current to be measured generated by the current to be measured, so as to set the effective cross-sectional area of ​​the magnetic flux lines of the magnetic field of the current to be measured received by the overcurrent detection inductor element, so that the maximum current to be measured that the overcurrent detection inductor element can detect is greater than the rated current, and the multiple relationship of the maximum current to be measured relative to the rated current is determined by the preset angle. Thus, by adjusting the angle of the overcurrent detection inductor element, the maximum current to be measured that is a multiple of the rated current can be detected, which is very suitable for short-circuit current detection caused by thermal runaway of the battery pack.

[0179] The above embodiments are merely illustrative of the principles and effects of the present disclosure, and are not intended to limit the present disclosure. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present disclosure shall still be covered by the claims of the present disclosure.

Claims

1. A variable magnetic inductance current sensor, characterized in that: include: An overcurrent detection inductor element generates a first excitation current in response to an applied first excitation voltage, wherein the first excitation current forms a first excitation magnetic field; An overcurrent detection circuit, used to determine whether the current to be measured is overcurrent based on the frequency and / or amplitude of the first excitation current related to the change in the inductance value of the overcurrent detection inductor element; In which, the overcurrent detection inductor element is placed so that the direction of the normal line of its cross section deviates from a preset angle relative to the magnetic field direction of the magnetic field of the current to be measured generated by the current to be measured, so as to set the effective cross-sectional area of ​​the overcurrent detection inductor element to receive the magnetic flux lines of the magnetic field of the current to be measured, so that the maximum current to be measured that the overcurrent detection inductor element can be used to detect is greater than the rated current, and the multiple relationship of the maximum current to be measured relative to the rated current is determined by the preset angle.

2. The variable magnetic inductance current sensor according to claim 1, characterized in that: include: at least one measuring inductance element, generating a second excitation current in response to an applied second excitation voltage, wherein the second excitation current forms a second excitation magnetic field; When the second excitation magnetic field is affected by the magnetic field of the current to be measured, the inductance value of the measuring inductance element changes to calculate the current to be measured; wherein, the at least one measuring inductance element is placed so that the normal direction of its cross section is parallel to the magnetic field direction of the magnetic field of the current to be measured.

3. The variable magnetic inductance current sensor according to claim 1, characterized in that: The overcurrent detection inductor element is connected with a capacitor to form an LC oscillation circuit.

4. The variable magnetic inductance current sensor according to claim 3, characterized in that: The overcurrent detection circuit is used to determine whether the current to be measured is overcurrent based on detecting whether the oscillation frequency of the LC oscillation circuit reaches a preset frequency threshold; the preset frequency threshold is determined based on the mathematical relationship between the current to be measured and the oscillation frequency, the rated value of the current to be measured, and the preset angle.

5. The variable magnetic inductance current sensor according to claim 4, characterized in that: The mathematical relationship is obtained by linking the relationship between the inductance value of the overcurrent detection inductor and the oscillation frequency, the relationship between the magnetic flux of the measured current magnetic field generated by the measured current and the magnetic permeability of the overcurrent detection inductor, and the relationship between the magnetic permeability and the inductance value of the overcurrent detection inductor.

6. The variable magnetic inductance current sensor according to claim 1, characterized in that: include: An overcurrent detection excitation circuit, coupled to the overcurrent detection inductor element, for applying an excitation voltage to the overcurrent detection inductor element in response to a pulse signal to generate an excitation current signal, and leading out at least one output terminal in the conductive loop where the overcurrent detection inductor element is located, for outputting at least one current amplitude change signal related to the rate of change of the excitation current over time; the at least one current amplitude change signal is used to obtain current amplitude change information; An overcurrent detection circuit is used to obtain the current amplitude change information, and compare the current amplitude change information with the current amplitude change thresholds corresponding to the two first excitation magnetic fields with opposite magnetic field directions, so as to determine whether the current to be measured corresponding to the current amplitude change information is overcurrent; The overcurrent detection inductor element is configured to be applied with voltages in opposite directions alternately over time, so as to alternately form the two first excitation magnetic fields having opposite magnetic field directions.

7. The variable magnetic inductance current sensor according to claim 6, characterized in that: The overcurrent detection excitation circuit outputs a pair of current amplitude change signals based on two signal points in the conductive loop where the overcurrent detection inductor element is located, and the pair of current amplitude change signals are respectively related to the excitation currents that form two first excitation magnetic fields with opposite magnetic field directions; The overcurrent detection excitation circuit includes: a first conductive loop, a second conductive loop, and a switch group; The first conductive loop and the second conductive loop are configured to have a common circuit, and the overcurrent detection inductor is arranged in the common circuit; the switch group is arranged in the first conductive loop and the second conductive loop, and the switch state is set by two pulse signals of the same frequency and with a phase difference to alternately turn on / off the first conductive loop and the second conductive loop; wherein, when the first conductive loop and the second conductive loop are turned on, voltages of opposite polarities are applied to both ends of the common circuit to form excitation currents of opposite directions in the one overcurrent detection inductor; a first resistor is arranged in series with the overcurrent detection inductor in the common circuit; two signal points formed at both ends of the first resistor lead out a pair of output ends to output a pair of electrical signals as the pair of current amplitude change signals; The variable magnetic inductance current sensor further comprises: The differential operation circuit is used to obtain the current amplitude change information based on the differential calculation of the pair of current amplitude change signals.

8. The variable magnetic inductance current sensor according to claim 6, characterized in that: The overcurrent detection circuit comprises: a first comparator, outputting a first comparison result of the current amplitude change information and a first current amplitude change threshold corresponding to a magnetic field direction; wherein, when the current amplitude change information is higher than the first current amplitude change threshold, the first comparison result is a signal value indicating overcurrent; A second comparator outputs a second comparison result of the current amplitude change information and a second current amplitude change threshold corresponding to another opposite magnetic field direction; wherein, when the current amplitude change information is lower than the second current amplitude change threshold, the second comparison result is a signal value indicating overcurrent; The OR logic operation unit has two input terminals coupled to the output terminals of the first comparator and the second comparator, and an output terminal outputs the OR logic operation result of the two inputs.

9. The variable magnetic inductance current sensor according to claim 2, characterized in that: The at least one measuring inductance element comprises: a pair of measuring inductance elements configured to respectively form second excitation magnetic fields with opposite magnetic fields; or a measuring inductance element configured to alternately form second excitation magnetic fields with opposite magnetic fields in directions as time changes.

10. An overcurrent detection method, characterized in that: The variable magnetic inductance current sensor according to any one of claims 1 to 9; the method comprising: Applying an excitation voltage to the overcurrent detection inductor element to generate an excitation current; Acquire the excitation current value of the overcurrent detection inductor element at at least one acquisition moment under the action of the magnetic field of the current to be measured; Whether the current to be measured is overcurrent is detected based on the excitation current value.

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