Structural co-forming TMR sensor and sensitivity coefficient calibration method thereof

Abstract

The application discloses a structure coform TMR sensor and a sensitivity coefficient calibration method thereof, wherein the TMR sensor comprises a TMR electronic mutual inductor and a sensitivity coefficient calibration device; the sensitivity coefficient calibration device is arranged on a PCB board of the TMR electronic mutual inductor in a structure coform mode and comprises a calibration coil, a calibration power supply, a current detection resistor, a current detection signal amplifier, a current detection voltage collector and a processor; the calibration coil is arranged around a TMR chip and is used for generating a uniform magnetic field in a magnetic sensitive direction of the TMR chip; the processor of the sensitivity coefficient calibration device calibrates the sensitivity coefficient of the TMR electronic mutual inductor according to the output voltage of the TMR electronic mutual inductor before and during calibration, the voltage of the current detection resistor and the relative position relationship between the calibration coil and the TMR chip. The application generates a high-uniformity magnetic field, realizes high-precision online self-calibration and improves the accuracy of current measurement of a power system.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a structurally conformal TMR sensor and its sensitivity coefficient calibration method. Background Technology

[0002] Tunnel magnetoresistive (TMR) sensors have attracted much attention due to their high sensitivity, low power consumption, and low temperature drift. Researchers have conducted studies on their miniaturization applications, weak current measurement, and broadband wireless measurement. Driven by the demand for intelligent sensing in new power systems, a large number of electronic sensors are deployed in power systems. Since power equipment can have a lifespan of over ten years, the long-term stability of measurement devices is crucial. The direct input physical quantity of TMR sensors is magnetic flux density. Currently, there is no long-term stable, controllable, and integrable direct reference source; therefore, calibration is required using an electromagnetic coil to generate a controllable magnetic field. Current calibration methods for TMR sensors mainly involve mounting the TMR chip or the entire sensor onto a dedicated test platform and using a Helmholtz coil to generate a controllable, uniform magnetic field for calibration.

[0003] Tunnel magnetoresistive (TMR) sensors require periodic calibration during grid-connected operation. Currently, the calibration method for TMR sensors mainly involves mounting the TMR chip or sensor as a whole onto a dedicated test platform and calibrating it by generating a uniform magnetic field of controllable magnitude using a Helmholtz coil. However, the Helmholtz coil is large, expensive, and has a complex manufacturing process, which can no longer meet the requirements of digitalization and intelligence for miniature intelligent sensors. Summary of the Invention

[0004] This invention provides a structurally conformal TMR sensor and its sensitivity coefficient calibration method. By generating a highly uniform magnetic field, it achieves high-precision online self-calibration, thereby improving the accuracy of current measurement in power systems.

[0005] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0006] A conventional TMR sensor includes: a TMR electronic current transformer and a sensitivity coefficient calibration device; the sensitivity coefficient calibration device includes a calibration coil, a calibration power supply, a current sensing resistor, a current sensing voltage acquisition unit, and a processor; the calibration power supply, calibration coil, and current sensing resistor are connected in series to form a current loop;

[0007] The calibration power supply is used to discharge to the calibration coil to generate a calibration current;

[0008] The calibration coil adopts a common structural design and is placed around the TMR chip of the TMR electronic current transformer to generate a uniform magnetic field domain in the magnetically sensitive direction of the TMR chip.

[0009] The current sensing voltage acquisition device is used to acquire the voltage of the current sensing resistor;

[0010] The processor is used to calibrate the sensitivity coefficient of the TMR electronic instrument transformer based on the output voltage of the TMR electronic instrument transformer before and during calibration, the voltage of the current sensing resistor, and the relative positional relationship between the calibration coil and the TMR chip.

[0011] Furthermore, let the direction of the primary circuit to be measured by the TMR sensor be the y-axis, and the magnetic sensitivity direction of the TMR chip based on the current flowing through the primary circuit to be measured be the x-axis. Let the PCB layer where the TMR chip is located be the front side of the PCB board. Then the winding method of the calibration coil is as follows: on the back side of the PCB board, the calibration coil is arranged along the y-axis at the position of the TMR chip; on the front side of the PCB board, the calibration coil is wrapped around the TMR chip at a safe distance; the calibration coil is connected between the front and back sides of the PCB board by a via.

[0012] Furthermore, if we denote the axis passing through the center point of the TMR chip and perpendicular to the magnetic sensitivity direction as the axis of symmetry, then the conductor segments of the calibration coil on the back of the PCB board satisfy the following: symmetrically distributed on both sides of the axis of symmetry, and the distance between the normalized equivalent circuit and the TMR chip... The number of conductors and the spacing between them must satisfy the following constraints:

[0013] ;

[0014] In the formula: For a uniform magnetic field Constraint points The difference in magnetic field strength It is a conductor Distance from the axis of symmetry The number of conductors on the back of the PCB board for calibrating the coil, located to the right of the axis of symmetry; , Constraint points The horizontal component of the magnetic field strength along the x-axis is calculated using the following formula:

[0015] ;

[0016] In the formula: Constraint points Distance from the axis of symmetry ,and , , The number of constraint points set on one side of the axis of symmetry to generate a uniform magnetic field domain for the calibration coil is n ≥ m-1; It is the Kronecker function, which has a value of 1 when its first index is equal to its second index, and 0 otherwise. It is the calibration current in the calibration coil; It is the permeability.

[0017] Furthermore, the number and spacing of conductors on the back of the PCB board for the calibration coil also meet the dimensional and process requirements between conductors: if the calibration coil has a central conductor on the axis of symmetry, that is, the distance of the central conductor from the axis of symmetry... Then it requires If the calibration coil does not have a central conductor on the axis of symmetry, that is, the distance of the first conductor from the axis of symmetry... Then it requires ;in, It is the sum of the minimum allowable conductor width and the minimum gap between adjacent conductors.

[0018] Furthermore, in all schemes that satisfy all constraints... In the middle, the preferred option is to make the first constraint point Horizontal component of magnetic induction intensity B along the x-axis Q1x The smallest solution.

[0019] Furthermore, the formula for calibrating the sensitivity coefficient of the TMR electronic instrument transformer is as follows:

[0020] ;

[0021] In the formula: This represents the sensitivity coefficient obtained from calibration; This indicates the distance between the normalized equivalent circuit of the calibration coil and the TMR chip. This indicates the amplifier gain set between the current sensing resistor and the current sensing voltage acquisition unit; It is the resistance value of the current sensing resistor; This indicates the sensor output voltage during calibration; This indicates the sensor output voltage before calibration begins; It is the gain ratio of the TMR sensor; It is the excitation voltage of the TMR sensor; It is the permeability; This represents the output voltage after the current sensing resistor is amplified and gaining power. This represents the normalized equivalent coefficient of the current multiplication of the calibration coil.

[0022] Furthermore, the current multiplication normalization equivalent coefficient of the calibration coil... The calculation method is as follows:

[0023] .

[0024] A method for calibrating the sensitivity coefficient of a TMR sensor according to any one of the above claims, comprising:

[0025] With the sensitivity calibration device in the TMR sensor turned off, use only the TMR electronic current transformer to measure the primary line current. Record the output voltage value of the TMR electronic current transformer at any point during this measurement; this value is the sensor output voltage before calibration begins. ;

[0026] Turn off the sensitivity coefficient calibration device in the TMR sensor, inject transient calibration current into the calibration coil through the calibration power supply, and record the output voltage value of the TMR electronic instrument transformer at this time. And record the voltage value of the current sensing resistor acquired by the current sensing voltage acquisition device after amplification. ;

[0027] The sensitivity coefficient of the TMR electronic instrument transformer is calibrated based on the output voltage of the TMR before and during calibration, as well as the voltage of the current sensing resistor and the relative positional relationship between the calibration coil and the TMR chip.

[0028] Furthermore, according to different current phase angles of the primary circuit, transient calibration currents of corresponding polarities are injected respectively. Through multiple calibrations, the final sensitivity coefficient is obtained, which is then used by the TMR current sensor to measure the primary circuit current, thereby achieving online calibration of the sensitivity coefficient within the positive and negative bipolar symmetrical range.

[0029] Compared with existing technologies, the advantages of this invention are as follows: This invention innovatively designs a conformal uniform magnetic field calibration coil. By directly constructing the calibration coil on the PCB where the TMR chip is located, a uniform horizontal magnetic field is generated through the electromagnetic focusing effect of multi-turn skew-faced windings. The rigidly fixed conformal component improves the space utilization of the TMR sensor, reduces manufacturing costs, and eliminates the risk of mechanical assembly displacement. Regarding calibration current power consumption, under the same current and volume conditions, the power consumption required to generate the same magnetic induction intensity at the TMR chip is reduced by 60% compared to a Helmholtz coil, thus improving the endurance of the sensing node. Attached Figure Description

[0030] Figure 1 This is the structural framework of the TMR sensor with the common structure described in the embodiments of this application.

[0031] Figure 2 This is a schematic diagram illustrating the principle of winding a calibration coil to generate a uniform magnetic field domain as described in the embodiments of this application.

[0032] Figure 3 This is a schematic diagram of the solution to the Diophantine equation described in the embodiments of this application.

[0033] Figure 4The embodiments of this application show the conductor magnetic field distribution (a) and the change of the horizontal component of the magnetic induction intensity of the calibration coil on the back of the PCB board.

[0034] Figure 5 This is a schematic diagram of the magnetic field distribution error after optimizing the coil with a double-sided non-planar structure according to the embodiments of this application. Detailed Implementation

[0035] The embodiments of the present invention will be described in detail below. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operation processes to further explain the technical solutions of the present invention.

[0036] Example 1

[0037] This embodiment provides a structurally common TMR sensor, such as... Figure 1 As shown, the device includes a TMR electronic instrument transformer and a sensitivity coefficient calibration device. The sensitivity coefficient calibration device includes a calibration coil, a calibration power supply, a current-sensing resistor, a current-sensing signal amplifier, a current-sensing voltage acquisition unit, and a processor. The calibration coil, calibration power supply, and current-sensing resistor are connected in series to form a current loop. The calibration power supply discharges to the calibration coil to generate a calibration current. The calibration coil, using a common structural design, is mounted on the PCB board of the TMR electronic instrument transformer and located around the TMR chip, generating a uniform magnetic field in the magnetically sensitive direction of the TMR chip. The current-sensing voltage acquisition unit acquires the voltage of the current-sensing resistor; in this embodiment, the output is the voltage of the current-sensing resistor after amplification by the current-sensing signal amplifier. The processor of the sensitivity coefficient calibration device calibrates the sensitivity coefficient of the TMR electronic instrument transformer based on the output voltage of the TMR electronic instrument transformer before and during calibration, and based on the voltage of the current-sensing resistor and the relative positional relationship between the calibration coil and the TMR chip.

[0038] Let the direction of the primary circuit to be measured by the TMR sensor be the y-axis, and the magnetic sensitivity direction of the TMR chip based on the current flowing through the primary circuit be the x-axis. Let the PCB layer where the TMR chip is located be the front side of the PCB board. Then the winding method of the calibration coil is as follows: on the back layer of the PCB board, the calibration coil is arranged along the y-axis at the position of the TMR chip; on the front layer of the PCB board, the calibration coil is wrapped around the TMR chip at a safe distance; the calibration coil is connected between the front and back sides of the PCB board by a via.

[0039] To generate a uniform magnetic field B for calibration sIn this embodiment, the calibration coil and other components of the sensitivity coefficient calibration device are designed together on the PCB board of the TMR electronic current transformer using a common structural design. The design objectives include the following: (1) forming a horizontal uniform magnetic field covering the area of ​​the TMR chip; (2) low current demand and low power consumption; (3) optimized coil structure volume and common structural design.

[0040] First, consider constructing a measurement model for the key conductor. To ensure the consistency of the uniform magnetic field, the model adopts a left-right symmetrical structure. That is, several conductor segments of the calibration coil on the back of the PCB are symmetrically distributed on the left and right sides of the TMR chip. Construct a main conductor model of the conformal calibration coil, such as... Figure 2 As shown. Within the target radius of the horizontal uniform magnetic field, select values ​​from Q1 to Q... m Using the relationship between the horizontal components of the magnetic induction intensity of the points as constraints, and based on the different relative positions of the first to nth dominant conductors and the TMR chip, we analyze the contribution of different conductor schemes to the magnetic induction intensity at the constraint points of the magnetic sensitive element, and solve for the optimal geometric position of each dominant conductor.

[0041] According to the Biot-Savart law, the constraint points Q of the above dominant body model i Horizontal component of magnetic induction intensity B along the x-axis Qix The calculation formula is:

[0042] ;

[0043] In the formula: and They are the first Constraint points And the distance of conductor j from the axis of symmetry, , ,and , ; It is the Kronecker delta function, which has a value of 1 when its first index is equal to its second index, and 0 otherwise.

[0044] With B Q1x Based on this, let Let i = 2, ..., m. We can obtain an equation or system of Diophantine equations with a number of equations of size m-1, as shown in the following formula. To ensure that the equations have solutions, we need to ensure that n ≥ m-1. The condition for creating a uniform magnetic field is then the intersection of the solutions to the Diophantine equations:

[0045] ;

[0046] Obviously, the larger the value of the number of constraint points m, the stronger the uniform magnetic field constraint and the better the uniformity. However, in practical applications, the solution set is limited by process factors such as line width and line spacing, which may lead to problems that cannot be realized. Therefore, the values ​​of m and n need to be taken into account for the rationality of the solution values ​​of the equation.

[0047] Secondly, under the same current, the solution used should generate the highest possible magnetic flux density. By analyzing the formula for the horizontal component of the magnetic flux density, it can be found that this function in d j → Approaching its supremum at 0, due to the constraint on d j The size relationship between them can be determined by selecting the minimum value in the feasible region according to the order of j, which will satisfy the condition.

[0048] Secondly, in actual engineering, there is no situation where two conductors are infinitely close. From the perspective of practical feasibility, the conductor spacing must meet the minimum process requirements, that is, when d1 = 0, d2 ≥ l. min When d1 ≠ 0, d1 ≥ l min / 2,l min This is the sum of the minimum allowable line width and line spacing. To determine r... s and l min The optimal value of B is determined based on the calculation of the number of typical conductors, as well as whether to place a conductor in the middle (i.e., whether d1 is 0). Table 1 shows the optimal value of B for each conductor. Q1x The value of .

[0049] surface The effect of the central conductor on current efficiency

[0050] ;

[0051] As can be seen from the table, B Q1x With parameter r s and l min Both are negatively correlated; therefore, selecting the minimum value within a reasonable range will yield the optimal magnetic induction intensity utilization. The determination of the center conductor requires determining r. s and l min We'll consider the value of r later, because s and l min When the value is small, the enhancement of magnetic induction intensity by the central conductor is more significant than that by the total number of conductors; conversely, the total number of conductors is more important.

[0052] Finally, a unique optimal solution was selected from all schemes that met the above design objectives. To facilitate the evaluation of the dominance of the magnetic flux density focusing multiplication by the dominant configuration, a method for calculating the gain ratio of the current to the normalized equivalent circuit of the calibration coil, applicable to long straight conductors, was proposed. This method is used to calculate the normalized equivalent current multiplication coefficient g of the calibration coil, which is subsequently used to calibrate the sensitivity coefficient of the TMR electronic current transformer. The calculation method is as follows:

[0053] ;

[0054] Where: k is the conductor number; This represents the total number of conductor segments on the back of the PCB board where the line marker coil is located. When the conductors are axially symmetric, the calculation formula degenerates into:

[0055] ;

[0056] This means that the ratio between the equivalent current value of the virtual conductor and the current value of the calibration coil, after normalizing and converting all the dominant current values ​​of the calibration coil to the position where q is 0, is calculated. The larger the value, the higher the current utilization rate. Based on this formula, the current gain ratio of various coils can also be conveniently evaluated when the coil geometry is known.

[0057] Based on the above steps, a specific embodiment is as follows: After fully considering the constraints of process factors such as PCB line width, line spacing, copper thickness, internal resistance, board thickness, and plating, and according to the actual needs of typical calibration scenarios according to this embodiment of the invention, a set of typical design values ​​was finally determined: r s = 2.1 mm; l min = 0.4 mm; m = 3. Constraint points are uniformly set at the center, boundary, and midpoint of the target uniform magnetic field region to obtain a more uniform magnetic field. The values ​​at the three locations are q1 = 0, q2 = 0.5 mm, and q3 = 1.0 mm. The resulting uniform region has a length of 2.0 mm, which can completely cover the magnetic sensing element of the TMR chip in the horizontal direction. n = 4 (d1 = 0). A system of indeterminate equations is constructed using redundant conductors, expanding the selectable domain of the solution to improve compatibility. The distance of the dominant body from the axis of symmetry does not exceed 5 mm.

[0058] The solution to all Diophantine equations is calculated using the above design values ​​as follows: Figure 3 As shown, the feasible region of the principal conductor's position where a uniform magnetic field can be formed is represented; the intersection of the two surfaces forms a red curve. g can be obtained within the feasible region of the principal conductor's position. max The solution is the unique optimal solution that meets the requirements, as shown by the coordinates of the blue point in the figure. When more conductors are involved in the calculation, it can be achieved by constructing... A single-precision floating-point tensor invokes the graphics processor to quickly compute the feasible region and the required optimal solution. The points marked in blue represent the optimal solution; the solution, retaining four significant digits, is:

[0059] ;

[0060] Substituting the solution into the magnetic induction intensity constraint formula, the current required to generate a horizontal magnetic induction intensity of 1 mT at point Q1 is calculated to be 2.714 A. Substituting it again to check the accuracy loss caused by retaining four significant digits at the three constraint points, the calculation results show that the error at each point is less than one ten-thousandth, the theoretical calculation result is valid, and the requirements for the preparation of a uniform magnetic field are met.

[0061] Finite element simulation was conducted to verify and explore the distribution of the continuous horizontal component of magnetic induction intensity between Q1 and Q3, and a finite element simulation model was constructed as follows. Figure 4 As shown, (a) shows the distribution of the dominant magnetic field obtained by finite element calculation, and (b) is the curve of the variation of the horizontal component of the magnetic induction intensity in the uniform magnetic field domain.

[0062] from Figure 4 It can be seen that the main body design can form a uniform magnetic field region with a width of 2 mm at the magnetic sensing element of the TMR chip. This width is greater than the 1.5 mm width of the magnetic sensing element inside the TMR chip, and it also has a 25% redundancy space, which can meet the calibration requirements of the TMR sensor.

[0063] After designing the double-sided, non-planar coil rewinding, the coil geometry was optimized. Bezier curves were used to optimize the rewinding conductor structure, and the line width was appropriately increased to reduce internal resistance. The optimized coil magnetic field distribution error due to the double-sided, non-planar structure is as follows: Figure 5 As shown, the magnetic induction intensity error was reduced to 0.02%.

[0064] Based on the calibration coil designed above, this embodiment generates a uniform magnetic field domain in the magnetically sensitive direction of the TMR chip, thereby allowing the sensitivity coefficient of the TMR electronic current transformer to be further calibrated using the following calculation formula:

[0065] ;

[0066] In the formula: This represents the sensitivity coefficient obtained from calibration; This indicates the distance between the normalized equivalent circuit of the calibration coil and the TMR chip. This indicates the amplifier gain set between the current sensing resistor and the current sensing voltage acquisition unit; It is the resistance value of the current sensing resistor; This indicates the sensor output voltage during calibration; This indicates the sensor output voltage before calibration begins; It is the gain ratio of the TMR sensor; It is the excitation voltage of the TMR sensor; It is the permeability; This represents the output voltage after the current sensing resistor is amplified and gaining power. This represents the normalized equivalent coefficient of the current multiplication of the calibration coil.

[0067] Example 2

[0068] This embodiment provides a sensitivity coefficient calibration method for the TMR sensor described in Embodiment 1, including:

[0069] Step 1: Turn off the sensitivity coefficient calibration device in the TMR sensor. Use only the TMR electronic current transformer to measure the line current. Record the output voltage value of the TMR electronic current transformer at any time during this line current measurement. This value is the sensor output voltage before calibration begins. ;

[0070] Step 2: Turn off the sensitivity coefficient calibration device in the TMR sensor, inject transient calibration current into the calibration coil through the calibration power supply, and record the output voltage value of the TMR electronic transformer at this time. And record the voltage value of the current sensing resistor acquired by the current sensing voltage acquisition device after amplification. ;

[0071] Step 3: Based on the output voltage of the TMR electronic instrument transformer before and during calibration, and based on the voltage of the current sensing resistor and the relative positional relationship between the calibration coil and the TMR chip, calibrate the sensitivity coefficient of the TMR electronic instrument transformer.

[0072] The calculation formula for calibrating the sensitivity coefficient of the TMR electronic current transformer is the same as that described in Example 1.

[0073] In a preferred embodiment, according to different current phase angles in the primary circuit, a transient calibration current of corresponding polarity is injected by controlling the full-bridge switch. That is, when the primary circuit is in the positive half-cycle of the power frequency current, a positive polarity calibration current is injected, so that the direction of the magnetic field generated by the calibration coil and the primary circuit at the TMR chip is the same; otherwise, a negative polarity calibration current is injected. The full-bridge switch is disconnected 0.1 ms after the current is injected. The sensitivity coefficient matrix is ​​obtained through multiple calibrations and used for subsequent TMR current sensor measurements of the primary circuit current, realizing online calibration of the sensitivity coefficient within the positive and negative bipolar symmetrical range.

[0074] The above embodiments are preferred embodiments of this application. Those skilled in the art can make various changes or improvements based on them. Without departing from the overall concept of this application, these changes or improvements should fall within the scope of protection claimed in this application.

Claims

1. A structurally conformal TMR sensor, characterized in that, include: TMR electronic current transformer and sensitivity coefficient calibration device; The sensitivity coefficient calibration device includes a calibration coil, a calibration power supply, a current sensing resistor, a current sensing voltage acquisition unit, and a processor; The calibration power supply, calibration coil, and current sensing resistor are connected in series to form a current loop. The calibration power supply is used to discharge to the calibration coil to generate a calibration current; The calibration coil adopts a common structural design and is placed around the TMR chip of the TMR electronic current transformer to generate a uniform magnetic field domain in the magnetically sensitive direction of the TMR chip. The current sensing voltage acquisition device is used to acquire the voltage of the current sensing resistor; The processor is used to calibrate the sensitivity coefficient of the TMR electronic instrument transformer based on the output voltage of the TMR electronic instrument transformer before and during calibration, the voltage of the current sensing resistor, and the relative positional relationship between the calibration coil and the TMR chip. The formula for calibrating the sensitivity coefficient of the TMR electronic instrument transformer is as follows: ； In the formula: This represents the sensitivity coefficient obtained from calibration; This indicates the distance between the normalized equivalent circuit of the calibration coil and the TMR chip. This indicates the amplifier gain set between the current sensing resistor and the current sensing voltage acquisition unit; It is the resistance value of the current sensing resistor; This indicates the sensor output voltage during calibration; This indicates the sensor output voltage before calibration begins; It is the gain ratio of the TMR sensor; It is the excitation voltage of the TMR sensor; It is the permeability; This represents the output voltage after the current sensing resistor is amplified and gaining power. This represents the normalized equivalent coefficient of the current multiplication of the calibration coil.

2. The structurally conformal TMR sensor according to claim 1, characterized in that, Let the direction of the primary circuit to be measured by the TMR sensor be the y-axis, and the magnetic sensitivity direction of the TMR chip based on the current flowing through the primary circuit be the x-axis. Let the PCB layer where the TMR chip is located be the front side of the PCB board. Then the winding method of the calibration coil is as follows: on the back layer of the PCB board, the calibration coil is arranged along the y-axis at the position of the TMR chip; on the front layer of the PCB board, the calibration coil is wrapped around the TMR chip at a safe distance; the calibration coil is connected between the front and back sides of the PCB board by a via.

3. The structurally conformal TMR sensor according to claim 2, characterized in that, Let the axis passing through the center point of the TMR chip and perpendicular to the magnetic sensitivity direction be denoted as the axis of symmetry. Then, several conductor segments of the calibration coil on the back of the PCB board satisfy the following: symmetrically distributed on both sides of the axis of symmetry, and the distance between the normalized equivalent circuit of the calibration coil and the TMR chip. The number of conductors and the spacing between them must satisfy the following constraints: ； In the formula: For a uniform magnetic field Constraint points The difference in magnetic field strength It is a conductor Distance from the axis of symmetry The number of conductors on the back of the PCB board for calibrating the coil, located to the right of the axis of symmetry; , Constraint points The horizontal component of the magnetic field strength along the x-axis is calculated using the following formula: ； In the formula: Constraint points Distance from the axis of symmetry ,and , , The number of constraint points set on one side of the axis of symmetry to generate a uniform magnetic field domain for the calibration coil is n ≥ m-1; It is the Kronecker function, when its first subscript... Its value is 1 when it is equal to the second subscript 0, and 0 otherwise; It is the calibration current in the calibration coil; It is the permeability.

4. The structurally conformal TMR sensor according to claim 3, characterized in that, The number and spacing of conductors on the back of the PCB board for the calibration coil also meet the dimensional requirements between conductors: if the calibration coil has a central conductor on the axis of symmetry, that is, the distance of the central conductor from the axis of symmetry... Then it requires If the calibration coil does not have a central conductor on the axis of symmetry, that is, the distance of the first conductor from the axis of symmetry... Then it requires ;in, It is the sum of the minimum allowable conductor width and the minimum gap between adjacent conductors.

5. The structurally conformal TMR sensor according to claim 3, characterized in that, In all schemes that satisfy all constraints In the middle, select the first constraint point. Horizontal component of magnetic induction intensity along the x-axis The smallest solution.

6. The structurally conformal TMR sensor according to claim 1, characterized in that, Current doubling normalized equivalent coefficient of calibration coil The calculation method is as follows: 。 7. A method for calibrating the sensitivity coefficient of a TMR sensor according to any one of claims 1-6, characterized in that, include: With the sensitivity calibration device in the TMR sensor turned off, use only the TMR electronic current transformer to measure the primary line current. Record the output voltage value of the TMR electronic current transformer at any point during this measurement; this value is the sensor output voltage before calibration begins. ; Turn off the sensitivity coefficient calibration device in the TMR sensor, inject transient calibration current into the calibration coil through the calibration power supply, and record the sensor output voltage during calibration. And record the voltage value of the current sensing resistor acquired by the current sensing voltage acquisition device after amplification. ; The sensitivity coefficient of the TMR electronic instrument transformer is calibrated based on the output voltage of the TMR before and during calibration, as well as the voltage of the current sensing resistor and the relative positional relationship between the calibration coil and the TMR chip.

8. The sensitivity coefficient calibration method according to claim 7, characterized in that, At different current phase angles of the primary circuit, transient calibration currents of corresponding polarities are injected. Through multiple calibrations, the final sensitivity coefficient is obtained, which is then used by the TMR current sensor to measure the primary circuit current, thus achieving online calibration of the sensitivity coefficient within the positive and negative bipolar symmetrical range.

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