A current sensor and a current detection method

Abstract

The present invention discloses a current sensor and a current detection method. The current sensor includes an excitation source unit, a first fluxgate detection unit, and an expansion module. The expansion module includes a second fluxgate detection unit, a switch unit, and a coil under test. The excitation source unit is respectively connected to the first fluxgate detection unit and the second fluxgate detection unit. The current output end of the first fluxgate detection unit is connected to the input end of the switch unit. The input end of the coil under test is connected to the input end of the switch unit. The conduction state of the switch unit is determined based on the target accuracy and target range of the current sensor. The current detection method is based on this current sensor, and the current to be measured is calculated through a compensation current. This application solves the problem that the current sensor cannot maintain a high signal-to-noise ratio when the current to be measured changes in a large dynamic range, and ensures high-precision current measurement.

Description

Technical Field

[0001] The present invention relates to the field of sensors, and in particular to a current sensor and a current detection method. Background Art

[0002] The current current sensor is a single-range proportional transformation device. Since its secondary coil is solidified inside the sensor, its range is single. Due to the existence of signal-to-noise ratio, the measurement accuracy is affected. Especially according to the requirements of different application scenarios, the signal-to-noise ratio requirements of current sensors are not very consistent. Especially in the field of high-energy physics, the dynamic range of the measured signal is large, and a single-range current sensor usually cannot guarantee a high signal-to-noise ratio under a large dynamic range, that is, it cannot guarantee the accuracy under a large dynamic range.

[0003] In the prior art, the excitation source uses a periodic signal with a certain frequency to excite the magnetic core to saturation through the excitation coil. When the measured current IP = 0, the magnetic core maintains magnetic balance. If the measured current IP = x, this measured current breaks the magnetic balance, and the demodulator detects this balance and drives the servo source to generate a compensation current IS and apply it to the magnetic core to make the magnetic core restore balance; the number of turns of the measured current is denoted as WP, and the number of turns of the secondary compensation coil is denoted as WS. Then at this time, WP*IP = WS*IS; that is, the measured current IP = WS / WP *IS.

[0004] Once the current sensor is determined, WS / WP working simultaneously is a constant. The large dynamic change of the measured current IP causes a large dynamic change of the secondary current IS, but the system noise basically does not change with the measured current IP. Therefore, the signal-to-noise ratio of the secondary current IS will decrease with the decrease of the measured current, thus losing measurement accuracy.

[0005] If WP / WS = 1 / 4000, when the measured current IP = 4000A, then IS = 1A. Assuming the system noise is 10uA, the signal-to-noise ratio is 100dB;

[0006] When the measured current IP = 40A, IS = 10mA, and at this time the signal-to-noise ratio is 60dB, and the measurement accuracy is reduced.

[0007] If WP / WS = 1 / 400, since there is only one proportional coil, if IP = 4000A, at this time, due to the output capacity limitation of the servo source, it cannot output 10A current. Then the output data of the current sensor is invalid at this time, and the sensor enters an overload state, and there is a risk of saturating the magnetic core of the sensor. Summary of the Invention

[0008] The purpose of the present invention is to solve the problem that the current sensor cannot maintain a high signal-to-noise ratio when the measured current changes in a large dynamic range, and provides a current sensor.

[0009] To solve the above problems, the present invention adopts the following technical solutions.

[0010] A current sensor includes an excitation source unit, a first fluxgate detection unit, and an expansion module. Among them, the expansion module includes a second fluxgate detection unit, a switching unit, and a coil under test;

[0011] The excitation source unit is respectively connected to the first fluxgate detection unit and the second fluxgate detection unit;

[0012] The first fluxgate detection unit is used to detect a current to be measured, generate a first compensation current according to the current to be measured, and output the first compensation current from the current output end of the first fluxgate detection unit; the current output end of the first fluxgate detection unit is connected to the input end of the switching unit, and the output end of the switching unit is grounded;

[0013] The input end of the coil under test is connected to the input end of the switching unit, and the output end of the coil under test is grounded;

[0014] The second fluxgate detection unit is used to detect the current in the coil under test and output a second compensation current from the current output end of the second fluxgate detection unit. Among them, the conduction state of the switching unit is determined based on the target accuracy and target range of the current sensor.

[0015] In some of the embodiments, both the first fluxgate detection unit and the second fluxgate detection unit include: an excitation coil, an excitation magnetic core, a decoupling coil, a decoupling magnetic core, a detection coil, a detection magnetic core, a compensation coil, a demodulator, a power amplifier, a first resistor, and a second resistor; the output end of the excitation source unit is respectively connected to the input end of the decoupling coil, the input end of the excitation coil, and the input end of the demodulator. The output end of the excitation coil, the output end of the decoupling coil, and the output end of the detection coil are all connected to the input end of the demodulator. The output end of the decoupling coil is connected to one end of the first resistor, and the other end of the first resistor is grounded; the output end of the excitation coil is connected to one end of the second resistor, and the other end of the second resistor is grounded; the input end of the detection coil is grounded; the output end of the demodulator is connected to the input end of the power amplifier, the output end of the power amplifier is connected to the input end of the compensation coil, and the output end of the compensation coil is connected to the coil under test; the demodulator in the first fluxgate detection unit is connected to the switching unit.

[0016] In the above embodiments, the exciting coil, the exciting magnetic core, the decoupling coil, the decoupling magnetic core, the detection coil, the detection magnetic core, the compensation coil, the demodulator, the power amplifier, the first resistor, and the second resistor are only functional names. In the first fluxgate detection unit and multiple second fluxgate detection units, their sizes, dimensions, and specifications can all be different.

[0017] In some of the embodiments, the first fluxgate detection unit and the second fluxgate detection unit further include a third resistor and an operational amplifier; the input end of the operational amplifier is connected to the output end of the compensation coil and one end of the third resistor. The other end of the third resistor in the first fluxgate detection unit is connected to the input end of the measured coil, and the other end of the third resistor in the second fluxgate detection unit is grounded.

[0018] The third resistor is used to convert the first compensation current or the second compensation current into a voltage, and the operational amplifier is used to adjust the voltage to the standard output range; the third resistor and the operational amplifier are only functional names. In the first fluxgate detection unit and multiple second fluxgate detection units, their sizes and dimensions can be different.

[0019] In some of the embodiments, the magnetic properties of the exciting magnetic core and the decoupling magnetic core are the same, and the number of turns of the exciting coil is equal to the number of turns of the decoupling coil.

[0020] In some of the embodiments, the expansion module further includes a range status interface. The input end of the range status interface is connected to the output end of the switch unit. The range status interface is used for the staff to monitor and control the use of the expansion module; the switch unit further includes a monitoring interface, and the monitoring interface includes one or a group of LED lights.

[0021] In some of the embodiments, the excitation source unit includes an oscillation unit, a frequency distribution unit, a trigger unit, a power drive unit, and an output coupling unit;

[0022] The output end of the oscillation unit is connected to the input end of the frequency distribution unit. The oscillation unit serves as the clock source of the frequency distribution unit to provide the basic clock for the normal operation of the sensor;

[0023] The output end of the frequency distribution unit is connected to the input end of the trigger unit. The frequency distribution unit provides the excitation clock for the magnetic core and the demodulation clock for the demodulator according to the preset configuration;

[0024] The output end of the trigger unit is connected to the input end of the power drive unit. The trigger unit inverts the excitation clock to output two excitation clock signals with opposite polarities at different ports;

[0025] The output end of the power driving unit is connected to the input end of the output coupling unit, and the power driving unit enhances the load-carrying capacity of two excitation clock signals with opposite polarities to excite the magnetic core to saturation;

[0026] The output coupling unit is used to filter the DC signal output by the oscillation unit.

[0027] In some of the embodiments, the number of the expansion modules is N, and the N expansion modules are cascaded in sequence; wherein, the input end of the switching unit of the Nth expansion module is connected to the current output end of the second fluxgate detection unit of the (N - 1)th expansion module, where N is an integer greater than or equal to 2.

[0028] A circuit detection method based on the above current sensor, comprising:

[0029] Determining the conduction state of the switching unit based on the target accuracy and target range of the current sensor;

[0030] When the switching unit is conducting, determining the current to be measured based on the first compensation current;

[0031] When the switching unit is off, determining the current to be measured based on the second compensation current.

[0032] A current detection method based on the above current sensor, comprising:

[0033] Determining the conduction states of the switching units of the respective expansion modules based on the target accuracy and target range of the current sensor;

[0034] When the switching unit of the first-stage expansion module is conducting, determining the current to be measured based on the first compensation current;

[0035] When the switching unit of the Nth expansion module is conducting and the switching units of the previous N - 1 expansion modules are all off, determining the current to be measured based on the second compensation current output by the (N - 1)th expansion module;

[0036] When the switching units of the 1st to Nth expansion modules are all off, determining the current to be measured based on the second compensation current output by the Nth expansion module.

[0037] A first-stage expansion current sensor provided by the present application includes an excitation source unit, a first fluxgate detection unit, and an expansion module, and the expansion module includes a second fluxgate detection unit, a switching unit, and a coil under test;

[0038] The excitation source unit is respectively connected to the first fluxgate detection unit and the second fluxgate detection unit. The excitation source unit outputs a current signal IE to the first fluxgate detection unit and the second fluxgate detection unit, and the first fluxgate detection unit and the second fluxgate detection unit receive the current signal IE and maintain magnetic balance;

[0039] The first fluxgate detection unit is used to detect the current to be measured, generate a first compensation current IS from the current to be measured IP according to a certain ratio (WP / WS), and output the first compensation current IS from the current output terminal of the first fluxgate detection unit. The current change ratios (WP / WS) of the second fluxgate detection units in multiple expansion modules are all different; the current output terminal of the first fluxgate detection unit is connected to the input terminal of the switch unit, and the output terminal of the switch unit is grounded;

[0040] The input terminal of the coil under test is connected to the input terminal of the switch unit, and the output terminal of the coil under test is grounded;

[0041] The second fluxgate detection unit is used to detect the current in the coil under test and output a second compensation current from the current output terminal of the second fluxgate detection unit. Among them, the conduction state of the switch unit is determined based on the target accuracy and target range of the current sensor.

[0042] A multi-stage expansion current sensor provided by the present application is based on the above-mentioned first-stage expansion current sensor, where the number of expansion modules is N, and N expansion modules are cascaded in sequence; the input terminal of the switch unit of the Nth expansion module is connected to the current output terminal of the second fluxgate detection unit of the (N - 1)th expansion module, where N is an integer greater than or equal to 2.

[0043] A current detection method based on a first-stage expansion current sensor provided by the present application includes:

[0044] Determine the conduction state of the switch unit based on the target accuracy and target range of the current sensor;

[0045] When the switch unit is conducting, determine the current to be measured based on the first compensation current;

[0046] When the switch unit is off, determine the current to be measured based on the second compensation current.

[0047] A current detection method based on a multi-stage expansion current sensor provided by the present application includes:

[0048] Determine the conduction states of the switch units of each expansion module based on the target accuracy and target range of the current sensor;

[0049] When the switching unit of the first - stage expansion module is turned on, determine the current to be measured based on the first compensation current;

[0050] When the switching unit of the N - th stage of the expansion module is turned on and the switching units of the previous N - 1 stages of the expansion module are all turned off, determine the current to be measured based on the second compensation current output by the (N - 1) - th stage of the expansion module, where N is an integer greater than or equal to 2;

[0051] When the switching units of the 1st to N - th stages of the expansion module are all turned off, determine the current to be measured based on the second compensation current output by the N - th stage of the expansion module.

[0052] Therefore, the present invention has the following beneficial effects:

[0053] (1) The expansion module provides more simultaneously existing transformation ratios, is more flexible in use, can cover current changes in a large dynamic range, and ensures high - precision current measurement in a large dynamic range;

[0054] (2) By using an operational amplifier, when the measured signal is small, a larger signal output is obtained, improving the system signal - to - noise ratio and enhancing the system accuracy;

[0055] (3) Compared with the existing current sensors that perform secondary winding turn - number switching, there is basically no switching response time; in the prior - art solutions, the switching gap will cause the output to be invalid for a short period, and there is a risk of saturating the sensor magnetic core. The present invention is composed of multiple independent modules, and there is no data invalidation during switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0057] Figure 1 is the block diagram of the first - stage expansion structure of the current sensor provided by the present invention;

[0058] Figure 2 is the circuit topology diagram of the first - stage expansion of the current sensor provided by the present invention;

[0059] Figure 3 is the block diagram of the excitation source module of the current sensor provided by the present invention;

[0060] Figure 4 is the block diagram of the second - stage expansion structure of the current sensor provided by the present invention;

[0061] Figure 5 It is the topological diagram of the secondary expansion circuit of the current sensor provided by the present invention;

[0062] Figure 6 It is the schematic flow chart of the current detection method based on the primary expansion current sensor provided by the present invention;

[0063] Figure 7 It is the schematic flow chart of the current detection method based on the multi-stage expansion current sensor provided by the present invention.

[0064] Explanation of reference numerals:

[0065] 1. Excitation source unit; 11. Oscillation unit; 12. Frequency distribution unit; 13. Trigger unit; 14. Power drive unit; 15. Output coupling unit; 2. First fluxgate detection unit; 3. Expansion module; 31. Second fluxgate detection unit; 32. Switch unit. Detailed implementation manners

[0066] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. All other embodiments obtained by those of ordinary skill in the art based on the examples in the present application without creative efforts shall fall within the scope of protection of the present application.

[0067] Obviously, the accompanying drawings in the following description are only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative efforts, the present application can also be applied to other similar scenarios based on these drawings. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing or production changes based on the technical content disclosed in the present application are only conventional technical means and should not be understood as the content disclosed in the present application being insufficient.

[0068] Referring to "embodiments" in the present application means that the specific features, structures or characteristics described in combination with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0069] Unless otherwise defined, technical terms or scientific terms used in the claims and the specification shall have the ordinary meanings understood by those of ordinary skill in the technical field to which this application pertains. The words such as "a", "an", "one kind", "the" and the like used in the specification and claims of this patent application do not indicate a limitation in quantity and may represent singular or plural. Words such as "comprising" or "including" mean that the elements or items appearing before "comprising" or "including" cover the elements or items listed after "comprising" or "including" and their equivalent elements, and do not exclude other elements or items. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The term "a plurality of" used in the specification and claims of this patent application means two or more. "First", "second", "third" are only used to distinguish different objects and have no actual meaning. "And / or" describes the relationship between related objects and indicates that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0070] Embodiment 1: As Figure 1 shown, this embodiment provides a current sensor, which includes an excitation source unit 1, a first fluxgate detection unit 2, and an expansion module 3. The expansion module 3 includes a second fluxgate detection unit 31, a switch unit 32, and a coil under test. The output end of the excitation source unit 1 is respectively connected to the input end of the first fluxgate detection unit 2 and the input end of the second fluxgate detection unit 31. The output end of the first fluxgate detection unit 2 is respectively connected to the input end of the switch unit 32 and the input end of the coil under test. The first fluxgate detection unit 2 is used to detect the current to be measured, generate a first compensation current according to the current to be measured, and output the first compensation current from the current output end of the first fluxgate detection unit 2. The second fluxgate detection unit 31 is used to detect the current in the coil under test and output a second compensation current from the current output end of the second fluxgate detection unit 31. The conduction state of the switch unit 32 is determined based on the target accuracy and target range of the current sensor.

[0071] As Figure 2As shown, the excitation coil includes excitation coils W3 and W3', the excitation core includes excitation cores C3 and C3', the decoupling coil includes decoupling coils W2 and W2', the decoupling core includes decoupling cores C2 and C2', the detection coil includes detection coils W1 and W1', the detection core includes detection cores C1 and C1', the compensation coil includes compensation coils WS and WS', the demodulator includes a first demodulator and a second demodulator, and the power amplifier includes a first power amplifier and a second power amplifier; the first resistor includes first resistors R1 and R1', the second resistor includes second resistors R2 and R2', the third resistor includes third resistors RS and RS', and the operational amplifier includes operational amplifiers AS and AS'.

[0072] The first fluxgate detection unit 2 includes an excitation coil W3, an excitation core C3, a decoupling coil W2, a decoupling core C2, a detection coil W1, a detection core C1, a compensation coil WS, a first demodulator, a first power amplifier, a first resistor R1, a second resistor R2, a third resistor RS, and an operational amplifier AS; among them, the excitation core C3 and the decoupling core C2 have the same magnetic properties, and the number of turns of the excitation coil W3 is equal to the number of turns of the decoupling coil W2; the output end of the excitation source unit 1 is respectively connected to the input end of the decoupling coil W2, the input end of the excitation coil W3, and the input end of the first demodulator. The output ends of the excitation coil W3, the decoupling coil W2, and the detection coil W1 are all connected to the input end of the first demodulator. The output end of the decoupling coil W2 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is grounded; the output end of the excitation coil W3 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is grounded; the input end of the detection coil W1 is grounded; the output end of the first demodulator is connected to the input end of the first power amplifier, the output end of the first power amplifier is connected to the input end of the compensation coil WS, the output end of the compensation coil WS is connected to the input end of the operational amplifier AS and one end of the third resistor RS, the other end of the third resistor RS is connected to the input end of the coil under test, and the first demodulator is connected to the switch unit 32; the third resistor RS is used to convert the first compensation current into a voltage, and the operational amplifier AS is used to adjust the voltage to the standard output range.

[0073] The excitation source unit 1 outputs a current IE in a periodic signal with a certain frequency to excite the excitation core C3 to saturation through the excitation coil W3. The first demodulator identifies the magnetic flux change of the excitation core C3 through the voltage change on the second resistor R2 connected in series with the excitation coil W3. When the total magnetic flux is not 0 (that is, the current IP to be measured is not zero and a magnetic potential is generated), by controlling the first power amplifier to output a current IS to the compensation coil WS, a magnetic potential with the same magnitude and opposite direction as the magnetic potential generated by the current IP to be measured is generated until the total magnetic flux in the excitation core C3 is zero, completing the closed-loop control. At this time:

[0074] IP = WS / WP * IS.

[0075] The second fluxgate detection unit 31 includes an excitation coil W3', an excitation core C3', a decoupling coil W2', a decoupling core C2', a detection coil W1', a detection core C1', a compensation coil WS', a second demodulator, a second power amplifier, a first resistor R1', a second resistor R2', a third resistor RS', and an operational amplifier AS'; wherein the excitation core C3' and the decoupling core C2' have the same magnetic properties, and the number of turns of the excitation coil W3' is equal to the number of turns of the decoupling coil W2'; the output end of the excitation source unit 1 is respectively connected to the input end of the decoupling coil W2', the input end of the excitation coil W3', and the input end of the second demodulator, and the output end of the excitation coil W3', the output end of the decoupling coil W2' and the input end of the detection coil W1' The output ends are connected to the input end of the second demodulator, the output end of the decoupling coil W2' is connected to one end of the first resistor R1', and the other end of the first resistor R1' is grounded; the output end of the excitation coil W3' is connected to one end of the second resistor R2', and the other end of the second resistor R2' is grounded; the input end of the detection coil W1' is grounded; the output end of the second demodulator is connected to the input end of the second power amplifier, the output end of the second power amplifier is connected to the input end of the compensation coil WS', the output end of the compensation coil WS' is connected to the input end of the operational amplifier AS' and one end of the third resistor RS', and the other end of the third resistor RS' is grounded; the third resistor RS' is used to convert the second compensation current into a voltage, and the operational amplifier AS' is used to adjust the voltage to a standard output range.

[0076] The input end of the measured coil WP' is respectively connected to the output end of the third resistor RS and the output end of the switch unit 32, the compensation coil WS is connected in series with the measured coil WP', the current in the compensation coil WS is consistent with that in the measured coil WP', the output end of the measured coil WP' is connected to the output end of the switch unit 32 and grounded, the extension module 3 is provided with a range status interface SE1, and the range status interface SE1 is connected to the output end of the switch unit 32; the switch unit 32 is provided with a monitoring interface, and the monitoring interface is provided with a group of LED lights. The range status interface SE1 is used to monitor and control the use of the extension module 3. With the monitoring interface, the user can freely switch between the basic range and the extended range; the input end of the switch unit 32 is connected to the output end of the first demodulator, and the output end of the switch unit 32 is respectively connected to the output end of the compensation coil WS and the input end of the measured coil WP', the first demodulator outputs a signal to the switch unit 32, and the switch unit 32 controls whether the measured coil WP' of the extension module 3 is short-circuited according to the size of the first demodulator output signal.

[0077] The excitation source unit 1 outputs a current IE' to excite the excitation core C3' to saturation through the excitation coil W3' with a periodic signal of a certain frequency. The second demodulator identifies the magnetic flux change of the second excitation core C3' through the voltage change across the resistor R2' connected in series with the excitation coil W3'. When the total magnetic flux is not 0 (i.e., the measured current IS is not zero, generating a magnetomotive force), the second power amplifier is controlled to output a current IS' to the compensation coil WS', generating a magnetomotive force with the same magnitude and opposite direction as the magnetomotive force generated by the measured current IS until the total magnetic flux in the excitation core C3' is zero, completing the closed-loop control. At this time:

[0078] IS = WS' / WP' * IS';

[0079] IP = WS / WP * IS = WS / WP * WS' / WP' * IS'.

[0080] As Figure 3 shown, the excitation source unit 1 includes an oscillation unit 11, a frequency distribution unit 12, a trigger unit 13, a power drive unit 14, and an output coupling unit 15. The output end of the oscillation unit 11 is connected to the input end of the frequency distribution unit 12. The oscillation unit 11 serves as the clock source of the frequency distribution unit 12 to provide the basic clock for the normal operation of the sensor. The output end of the frequency distribution unit 12 is connected to the input end of the trigger unit 13. The frequency distribution unit 12 provides the excitation clock for the core and the demodulation clock for the demodulator according to the preset configuration. The output end of the trigger unit 13 is connected to the input end of the power drive unit 14. The trigger unit 13 inverts the excitation clock to output two excitation clock signals with opposite polarities at different ports. The output end of the power drive unit 14 is connected to the input end of the output coupling unit 15. The power drive unit 14 enhances the load-carrying capacity of the two excitation clock signals with opposite polarities to excite the core to saturation. The output coupling unit 15 is used to filter the DC signal output by the oscillation unit 11.

[0081] When the current sensor in this embodiment measures the current,

[0082] (a) If IP = 400A - 4000A, the expansion module 3 is disabled: WS = 4000, WP = 1, WS' = 100, WP' = 0, then IS = 0.1A - 1A, IS' = 0A; RS = 0.5R, the AS gain is 20, then

[0083] VS = 1V - 10V;

[0084] At this time, the system ratio is 4000A / 10V. Assuming the system noise is 10uV, the signal-to-noise ratio of this range is 100dB - 120dB.

[0085] (b) If IP = 40A to 400A, the expansion module 3 is disabled: WS = 4000, WP = 1, then IS = 0.01A to 0.1A, IS' = 0A; RS = 0.5R, the AS gain is 20, then

[0086] VS = 0.1V to 1V;

[0087] At this time, the system ratio is 400A / 1V. Assuming the system noise is 10uV, the signal-to-noise ratio of this range is 80dB to 100dB.

[0088] The expansion module 3 is enabled: WS = 4000, WP = 1, WS' = 100, WP' = 1000, then IS = 0.01A to 0.1A, IS' = 0.1A to 1A; RS' = 0.5R, the AS' gain is 20, then the output from VS'

[0089] VS' = 1V to 10V;

[0090] At this time, the system ratio is 400A / 10V. Assuming the system noise is 10uV, the signal-to-noise ratio of this range is 100dB to 120dB.

[0091] The basic range 1 / 4000 of this embodiment is always valid. When the expansion module 3 controls the switch unit 32 to enable the measured coil WP' according to the output signal of the first demodulator, the enabling point is about IP = 440A. When IP ranges from 40A (VS': 1V, VS: 0.1V) to 440A (VS': 11V, VS: 1.1V) in the extended range, the range status interface SE1 changes from low level to high level. The current sensor outputs through VS', and the switch unit 32 controls the measured coil WP' to be short-circuited, then IP' = IS, and there is no overload. When IP drops from 4000A (VS': 0V, VS: 10V) to 440A (VS': 11V, VS: 1.1V), the range status interface SE1 changes from high level to low level. The current sensor outputs through VS', and the switch unit 32 releases the short-circuit switch of the measured coil WP'.

[0092] Through the flexible configuration of the range status interface SE1 with VS' and VS, flexible switching without data loss can be achieved, and it is ensured that the signal-to-noise ratio of the measured current IP in the range of 40A to 4000A is greater than 100dB.

[0093] It can be seen that the use of the expansion module 3 improves the system signal-to-noise ratio and the low-range accuracy of the sensor.

[0094] Embodiment 2: As Figure 4As shown in the figure, this embodiment provides a current sensor, which includes an excitation source unit 1, a first fluxgate detection unit 2, and an expansion module 3. The expansion module 3 includes a first expansion module 3 and a second expansion module 3. The structures and connection relationships of the first expansion module 3 and the second expansion module 3 are the same, but the sizes, dimensions, and specifications of the components therein are different. The output end of the excitation source unit 1 is respectively connected to the input end of the first fluxgate detection unit 2, the input end of the first expansion module 3, and the input end of the second expansion module 3. The output end of the first fluxgate detection unit 2 is respectively connected to the input end of the switch unit 32 in the first expansion module 3 and the input end of the measured coil in the first expansion module 3. The output end of the second fluxgate detection unit 31 in the first expansion module 3 is respectively connected to the input end of the switch unit 32 in the second expansion module 3 and the input end of the measured coil in the second expansion module 3.

[0095] As Figure 5 shown, the excitation coils include excitation coil W3, excitation coil W3', and excitation coil W3''. The excitation cores include excitation core C3, excitation core C3', and excitation core C3''. The decoupling coils include decoupling coil W2, decoupling coil W2', and decoupling coil W2''. The decoupling cores include decoupling core C2, decoupling core C2', and decoupling core C2''. The detection coils include detection coil W1, detection coil W1', and detection coil W1''. The detection cores include detection core C1, detection core C1', and detection core C1''. The compensation coils include compensation coil WS, compensation coil WS', and compensation coil WS''. The demodulators include a first demodulator, a second demodulator, and a second demodulator. The power amplifiers include a first power amplifier, a second power amplifier, and a second power amplifier. The first resistors include first resistor R1, first resistor R1', and first resistor R1''. The second resistors include second resistor R2, second resistor R2', and second resistor R2''. The third resistors include third resistor RS, third resistor RS', and third resistor RS''. The operational amplifiers include operational amplifier AS, operational amplifier AS', and operational amplifier AS''. The range status interfaces include range status interface SE1 and range status interface SE2.

[0096] The structures of the first fluxgate detection unit 2, the first expansion module 3, and the second expansion module 3 are the same as those in Embodiment 1. The connection relationship between the first fluxgate detection unit 2 and the first expansion module 3 is the same as that in Embodiment 1. The input ends of the measured coil WP'' in the second expansion module 3 are respectively connected to the output end of the third resistor RS' in the first expansion module 3 and the output end of the switch unit 32 in the second expansion module 3. The compensation coil WS' in the first expansion module 3 is connected in series with the measured coil WP'' in the second expansion module 3. The current in the compensation coil WS' in the first expansion module 3 is the same as that in the measured coil WP'' in the second expansion module 3. The output end of the measured coil WP'' in the second expansion module 3 is connected to the output end of the switch unit 32 in the second expansion module 3 and grounded. The second expansion module 3 is provided with a range state interface SE2, and the range state interface SE2 is connected to the output end of the switch unit 32 in the second expansion module 3; the switch unit 32 is provided with a monitoring interface, and a set of LED lights is arranged on the monitoring interface. The range state interface SE2 is used to monitor and control the use of the second expansion module 3. In cooperation with the monitoring interface, the user can freely switch between the first-level expanded range and the second-level expanded range; the input end of the switch unit 32 in the second expansion module 3 is connected to the output end of the second demodulator in the first expansion module 3. The output end of the switch unit 32 in the second expansion module 3 is respectively connected to the output end of the compensation coil WS' in the first expansion module 3 and the input end of the measured coil WP'' in the second expansion module 3. The output signal of the second demodulator in the first expansion module 3 reaches the switch unit 32 in the second expansion module 3. The switch unit 32 in the second expansion module 3 controls whether the measured coil WP'' in the second expansion module 3 is short-circuited according to the magnitude of the output signal of the second demodulator in the first expansion module 3.

[0097] In this embodiment, WP*IP = WS*IS,

[0098] WP'*IS = WS'*IS',

[0099] WP''*IS' = WS''*IS'', so the current to be measured

[0100] IP = WS / WP*IS

[0101] = WS / WP*WS' / WP'*IS'

[0102] = WS / WP*WS' / WP'*WS'' / WP''*IS''.

[0103] Based on this, the present invention can continue to cascade to generate more embodiments, so as to cover the current changes in a large dynamic range and ensure the high-precision current measurement in a large dynamic range.

[0104] A current detection method based on a first-level extended current sensor provided by the present invention is as follows Figure 6 shown, and its steps include:

[0105] Determine the conduction state of the switch unit 32 based on the target accuracy and target range of the current sensor;

[0106] When the switch unit 32 is conducting, determine the current to be measured based on the first compensation current;

[0107] When the switch unit 32 is disconnected, determine the current to be measured based on the second compensation current.

[0108] Referring to Embodiment 1, when the switch unit 32 is conducting, the measured coil WP' is short-circuited. At this time, the expansion module 3 is in a non-working state, and the current to be measured can be determined through the first compensation current, that is:

[0109] IP = WS / WP * IS.

[0110] When the switch unit 32 is disconnected, the measured coil WP' works normally, and the expansion module 3 is in a working state. At this time, the first compensation current is: IS = WS' / WP' * IS';

[0111] The current to be measured can be determined through the second compensation current, that is:

[0112] IP = WS / WP * IS = WS / WP * WS' / WP' * IS'.

[0113] A current detection method based on a multi-level extended current sensor provided by the present invention is as follows Figure 7 shown, and its steps include:

[0114] Determine the conduction states of the switch units 32 of each expansion module 3 based on the target accuracy and target range of the current sensor;

[0115] When the switch unit 32 of the first-level expansion module 3 is conducting, determine the current to be measured based on the first compensation current;

[0116] When the switch unit 32 of the Nth-level expansion module 3 is conducting and the switch units 32 of the previous N-1 level expansion modules 3 are all disconnected, determine the current to be measured based on the second compensation current output by the (N-1)th-level expansion module 3;

[0117] When the switch units 32 of the 1st to Nth-level expansion modules 3 are all disconnected, determine the current to be measured based on the second compensation current output by the Nth-level expansion module 3.

[0118] Referring to Embodiment 2, when the switch unit 32 in the first expansion module 3 is turned on, the measured coil WP' in the first expansion module 3 is short-circuited. At this time, both the first expansion module 3 and the second expansion module 3 are in a non-operating state. The measured current can be determined through the first compensation current, that is:

[0119] IP = WS / WP * IS.

[0120] When the switch unit 32 in the second expansion module 3 is turned on and the switch unit 32 in the first expansion module 3 is turned off, the measured coil WP' in the first expansion module 3 operates normally, and the measured coil WP'' in the second expansion module 3 is short-circuited. At this time, the first expansion module 3 is in an operating state, and the second expansion module 3 is in a non-operating state. At this time, the first compensation current is: IS = WS' / WP' * IS'; the measured current can be determined through the second compensation current output by the first expansion module 3, that is:

[0121] IP = WS / WP * IS = WS / WP * WS' / WP' * IS'.

[0122] When the switch unit 32 in the first expansion module 3 and the switch unit 32 in the second expansion module 3 are both turned off, the measured coil WP' in the first expansion module 3 and the measured coil WP'' in the second expansion module 3 both operate normally. At this time, both the first expansion module 3 and the second expansion module 3 are in an operating state. At this time, the first compensation current is: IS = WS' / WP' * IS'; the second compensation current output by the first expansion module 3 is: IS' = WS'' / WP'' * IS''; the measured current can be determined through the second compensation current output by the second expansion module 3, that is:

[0123] IP = WS / WP * WS' / WP' * WS'' / WP'' * IS''.

[0124] Embodiment 2 is only an example rather than a limitation of the multi-stage extended current sensor. The multi-stage extended current sensor provided by the present invention is extended according to the actual application environment, and the number of its expansion stages is not limited. The current detection method based on the multi-stage extended current sensor provided by the present invention, which is described with reference to the current sensor in Embodiment 2, is only an example rather than a limitation. The current detection method based on the multi-stage extended current sensor provided by the present invention is applicable to any multi-stage extended current sensor provided by the present invention in actual applications.

[0125] The present invention is obviously not limited to the details of the above embodiments. In the case of including the basic features of the present invention, there are various specific embodiments that can implement the present invention. Therefore, this embodiment is exemplary rather than restrictive. Any changes or modifications made by those skilled in the art to the technical solution of the present invention, without departing from the scope of the claims of the present invention, are covered by the patent protection scope of the present invention.

Claims

1. A current sensor, characterized in that, It includes an excitation source unit (1), a first fluxgate detection unit (2), and an expansion module (3). Among them, the expansion module (3) includes a second fluxgate detection unit (31), a switching unit (32), and a coil under test; The excitation source unit (1) is respectively connected to the first fluxgate detection unit (2) and the second fluxgate detection unit (31); The first fluxgate detection unit (2) is used to detect the current to be measured, generate a first compensation current according to the current to be measured, and output the first compensation current from the current output end of the first fluxgate detection unit (2); the current output end of the first fluxgate detection unit (2) is connected to the input end of the switching unit (32), and the output end of the switching unit (32) is grounded; The input end of the coil under test is connected to the input end of the switching unit (32), and the output end of the coil under test is grounded; The second fluxgate detection unit (31) is used to detect the current in the coil under test and output a second compensation current from the current output end of the second fluxgate detection unit (31), where the conduction state of the switching unit (32) is determined based on the target accuracy and target range of the current sensor; When the switching unit (32) is conducting, the current to be measured is determined by the first compensation current; When the switching unit (32) is off, the current to be measured is determined by the second compensation current.

2. The current sensor according to claim 1, characterized in that, Both the first fluxgate detection unit (2) and the second fluxgate detection unit (31) include: an excitation coil, an excitation magnetic core, a decoupling coil, a decoupling magnetic core, a detection coil, a detection magnetic core, a compensation coil, a demodulator, a power amplifier, a first resistor, and a second resistor; the output end of the excitation source unit (1) is respectively connected to the input end of the decoupling coil, the input end of the excitation coil, and the input end of the demodulator. The output ends of the excitation coil, the decoupling coil, and the detection coil are all connected to the input end of the demodulator. The output end of the decoupling coil is connected to one end of the first resistor, and the other end of the first resistor is grounded; the output end of the excitation coil is connected to one end of the second resistor, and the other end of the second resistor is grounded; the input end of the detection coil is grounded; the output end of the demodulator is connected to the input end of the power amplifier, the output end of the power amplifier is connected to the input end of the compensation coil, and the output end of the compensation coil in the first fluxgate detection unit (2) is connected to the coil under test; the demodulator in the first fluxgate detection unit (2) is connected to the switching unit (32).

3. The current sensor according to claim 2, wherein The first fluxgate detection unit (2) and the second fluxgate detection unit (31) also include a third resistor and an operational amplifier; the input end of the operational amplifier is connected to the output end of the compensation coil and one end of the third resistor. The other end of the third resistor in the first fluxgate detection unit (2) is connected to the input end of the coil under test, and the other end of the third resistor in the second fluxgate detection unit (31) is grounded.

4. The current sensor according to claim 2, wherein, The excitation magnetic core and the decoupling magnetic core have the same magnetic properties, and the number of turns of the excitation coil is equal to the number of turns of the decoupling coil.

5. The current sensor according to claim 1, characterized in that, The extension module (3) further includes a range state interface. The input end of the range state interface is connected to the output end of the switch unit (32). The range state interface is used for staff to monitor and control the use of the extension module (3). The switch unit (32) further includes a monitoring interface, and the monitoring interface includes one or a group of LED lights.

6. The current sensor according to claim 2, characterized in that The excitation source unit (1) includes an oscillation unit (11), a frequency distribution unit (12), a trigger unit (13), a power drive unit (14), and an output coupling unit (15). The output of the oscillation unit (11) is connected to the input end of the frequency distribution unit (12). The oscillation unit (11) serves as the clock source of the frequency distribution unit to provide the clock for the normal operation of the sensor. The output end of the frequency distribution unit (12) is connected to the input end of the trigger unit (13). The frequency distribution unit (12) provides the excitation clock for the magnetic core and the demodulation clock for the demodulator according to the preset configuration. The output end of the trigger unit (13) is connected to the input end of the power drive unit (14). The trigger unit (13) inverts the excitation clock to output two excitation clock signals with opposite polarities at different ports. The output end of the power drive unit (14) is connected to the input end of the output coupling unit (15). The power drive unit (14) enhances the load-carrying capacity of the two excitation clock signals with opposite polarities to excite the magnetic core to saturation. The output coupling unit (15) is used to filter the DC signal output by the oscillation unit. Wherein, the output end of the output coupling unit (15) is respectively connected to the input end of the decoupling coil, the input end of the excitation coil, and the input end of the demodulator.

7. The current sensor according to any one of claims 1 to 6, characterized in that, The number of the extension modules (3) is N, and N extension modules (3) are cascaded in sequence. Wherein, the input end of the switch unit (32) of the Nth extension module (3) is connected to the current output end of the second fluxgate detection unit (31) of the (N - 1)th extension module (3), and N is an integer greater than or equal to 2.

8. A circuit detection method for the current sensor according to claim 1, characterized in that, Including: Determine the conduction state of the switch unit (32) based on the target accuracy and target range of the current sensor. When the switch unit (32) is conducting, determine the current to be measured based on the first compensation current. And When the switch unit (32) is off, determine the current to be measured based on the second compensation current.

9. A current detection method for the current sensor according to claim 7, characterized in that, Including: Determine the conduction state of the switch units (32) of each extension module (3) based on the target accuracy and target range of the current sensor. When the switch unit (32) of the first-stage extension module (3) is conducting, determine the current to be measured based on the first compensation current. When the switch unit (32) of the Nth extension module (3) is conducting and the switch units (32) of the previous N - 1 extension modules (3) are all off, determine the current to be measured based on the second compensation current output by the (N - 1)th extension module (3). When the switch units (32) of the first to Nth expansion modules (3) are all disconnected, the current to be measured is determined based on the second compensation current output by the Nth expansion module (3).

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