Three-phase array type digital TMR current sensor

Abstract

A three-phase array type digital TMR current sensor comprises a current sensor upper cover, a current sensor lower shell and a PCB, the current sensor upper cover is connected with the current sensor lower shell, and the PCB is located between the current sensor upper cover and the current sensor lower shell. The TMR chips are used for collecting magnetic field data generated by current passing through the three-phase copper bar, the TMR chips are welded on a first straight line or a second straight line on the PCB, and the TMR chips are arranged on the PCB in an array mode; the PCB is also provided with an MCU module which is used for collecting the output of the TMR chip and carrying out calculation to obtain the current value of each phase of the three-phase copper bar. The MCU module is internally provided with a temperature compensation algorithm, a current secondary calibration algorithm and a frequency check and compensation algorithm. The three-phase array type digital TMR current sensor has the advantages of being small in size, light in weight and high in precision, and meanwhile the size and cost of an electric drive controller are greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicle sensors, and in particular to a three-phase array digital TMR current sensor. Background Art

[0002] The functions of current sensors mainly include power measurement, energy monitoring, power protection and current control, and the current sensor of the electric drive controller for new energy vehicles is mainly used to detect the torque and speed of the motor. The current detection accuracy and reliability of this current sensor directly determine the control efficiency, driving stability and safety of the electric drive controller. In the prior art, new energy vehicle manufacturers widely use Hall current sensors. However, Hall current sensors are large in size and weight, high in cost and low in precision. In order to reduce the manufacturing cost of new energy vehicles, Hall current sensors have gradually revealed their disadvantages. Summary of the invention

[0003] In view of the above problems, the present invention provides a three-phase array digital TMR current sensor.

[0004] The technical solutions to the above technical problems are as follows:

[0005] A three-phase array digital TMR current sensor comprises a current sensor upper cover, a current sensor lower shell, and a PCB board, wherein the current sensor upper cover is connected to the current sensor lower shell, the PCB board is located between the current sensor upper cover and the current sensor lower shell, and further comprises a three-phase copper busbar and a plurality of TMR chips for collecting magnetic field data generated by current passing through the three-phase copper busbar, wherein the TMR chips are welded on a first straight line or a second straight line on the PCB board, and the spacing between the TMR chips welded on the first straight line of the PCB board is the same as the spacing between the TMR chips welded on the second straight line of the PCB board, wherein the TMR chips are arranged on the PCB board in an array manner, and an MCU module for collecting the output of the TMR chips and calculating the current value on each phase of the three-phase copper busbar is further provided on the PCB board, wherein the MCU module has a built-in temperature compensation algorithm, a current secondary calibration algorithm, and a frequency check and compensation algorithm, and the working process of the built-in temperature compensation algorithm is to perform table lookup compensation on the zero point and gain of the sensor through the temperature data fed back by the temperature sensor, and the formula is as follows:

[0006] y=k t x+b t

[0007] In the formula, y is the output after temperature compensation; x is the current output; kt is the gain temperature compensation coefficient at the current temperature point; bt is the zero temperature compensation coefficient at the current temperature point. In practical applications, the values ​​of kt and bt are queried according to the current temperature point to calculate the current.

[0008] The frequency measurement and detection algorithm measures the frequency of the primary current in real time and compensates the output current according to the measurement result. The compensation formula is:

[0009] y=k f x+b f

[0010] In the formula, y is the output after frequency compensation, x is the current output, kf is the gain compensation coefficient at the current frequency point, and bf is the compensation coefficient at the current frequency point. In practical applications, the values ​​of kf and bf are queried according to the current frequency point to perform current calculations.

[0011] Furthermore, the number of TMR chips on the PCB board is ≥3.

[0012] Furthermore, the current sensor upper cover includes a bottom and a wall portion, a plurality of snap-in connectors are provided on the wall portion, and the current sensor lower shell includes a lower shell body, a concave cavity is provided on the lower shell body, a plurality of snap-in grooves are provided on the wall surface of the concave cavity, and the snap-in connectors cooperate with the snap-in grooves.

[0013] The beneficial effects of the present invention are as follows: the present invention provides a three-phase array digital TMR current sensor, which detects the magnetic field generated by the three-phase copper busbar according to the characteristics of high sensitivity, low noise and high precision of the TMR chip, and then uses an array arrangement to detect the magnetic fields at different positions of the three-phase copper busbar, and then calculates the magnitude of the current in the three-phase copper busbar through a current solution algorithm while avoiding magnetic interference of different phases. Since the MCU module is built-in on the PCB board, the TMR current sensor can judge the state of the three-phase current and send abnormal conditions to the controller. The three-phase array digital TMR current sensor provided by the present invention has the characteristics of small size, light weight and high precision, and also greatly reduces the size and cost of the electric drive controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 An exploded view of the three-phase array digital TMR current sensor of the present invention;

[0015] Figure 2 It is a front view of the PCB board of the three-phase array digital TMR current sensor of the present invention;

[0016] Figure 3 A three-dimensional diagram of a current sensor upper cover of a three-phase array digital TMR current sensor of the present invention;

[0017] Figure 4 It is a three-dimensional diagram of the lower shell of the current sensor of the three-phase array type digital TMR current sensor of the present invention;

[0018] Figure 5The following is a working diagram of the three-phase array digital TMR current sensor of the present invention;

[0019] Figure 6 This is a flow chart of the temperature compensation algorithm of the present invention;

[0020] Figure 7 This is a flow chart of the frequency checking and compensation algorithm of the present invention.

[0021] Markings in the accompanying drawings: current sensor upper cover 1, bottom 1-1, wall 1-2, card connector 1-3, TMR chip 2, PCB board 3, current sensor lower shell 4, lower shell body 4-1, concave cavity 4-2, card slot 4-3. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0023] like Figures 1 to 7 As shown, a three-phase array digital TMR current sensor includes a current sensor upper cover 1, a current sensor lower shell 4, and a PCB board 3. The current sensor upper cover 1 is connected to the current sensor lower shell 4. The PCB board 3 is located between the current sensor upper cover 1 and the current sensor lower shell 4. It also includes a three-phase copper busbar and a plurality of TMR chips 2 for collecting magnetic field data generated by current passing through the three-phase copper busbar. The TMR chip 2 is welded on the first straight line or the second straight line on the PCB board 3. The spacing between the TMR chips 2 welded on the first straight line of the PCB board 3 is the same as the spacing between the TMR chips 2 welded on the second straight line of the PCB board 3. These TMR chips 2 are arranged on the PCB board 3 in an array. The PCB board 3 is also provided with an MCU module for collecting the output of the TMR chip 2 and calculating the current value on each phase of the three-phase copper busbar. The MCU module has a built-in temperature compensation algorithm, a current secondary calibration algorithm, and a frequency measurement and compensation algorithm. The working process of the built-in temperature compensation algorithm is to perform table lookup compensation on the zero point and gain of the sensor through the temperature data fed back by the temperature sensor. The formula is as follows:

[0024] y=k t x+b t

[0025] Wherein, y is the output after temperature compensation; x is the current output; kt is the gain temperature compensation coefficient of the current temperature point; bt is the zero temperature compensation coefficient of the current temperature point. In practical applications, the values ​​of kt and bt are queried according to the current temperature point to perform current calculation. In this embodiment, the current secondary calibration algorithm is used, that is, the output of the sensor is linearly calibrated again. The formula is the same as that in the temperature compensation algorithm, that is, the current output is calibrated using the kt and bt values ​​at a temperature point of 25°C.

[0026] The frequency measurement and detection algorithm measures the frequency of the primary current in real time and compensates the output current according to the measurement result. The compensation formula is:

[0027] y=k f x+b f

[0028] In the formula, y is the output after frequency compensation, x is the current output, kf is the gain compensation coefficient at the current frequency point, and bf is the compensation coefficient at the current frequency point. In practical applications, the values ​​of kf and bf are queried according to the current frequency point to perform current calculations.

[0029] Specifically, Figure 2 As shown, a plurality of TMR chips 2 are welded on the PCB board 3, and these TMR chips 2 are located on the X1 straight line or the X2 straight line of the PCB board 3, and the spacing between two adjacent TMR chips 2 on the X1 straight line is L2, and the spacing between two adjacent TMR chips 2 on the X2 straight line is L1, wherein L1=L2, thereby ensuring that all the TMR chips 2 are welded on the PCB board 3 in an array arrangement, thereby ensuring that the magnitude and direction of the magnetic field induced by the TMR chip 2 at each position are different.

[0030] The number of TMR chips 2 on the PCB board 3 is ≥ 3.

[0031] The current sensor upper cover 1 includes a bottom 1-1 and a wall portion 1-2, and a plurality of snap-in joints 1-3 are provided on the wall portion 1-2. The current sensor lower shell 4 includes a lower shell body 4-1, and a concave cavity 4-2 is provided on the lower shell body 4-1. A plurality of snap-in grooves 4-3 are provided on the wall surface of the concave cavity 4-2, and the snap-in joints 1-3 cooperate with the snap-in grooves 4-3.

[0032] When assembling the current sensor upper cover 1 and the current sensor lower shell 4, align the card connector 1-3 with the card slot 4-3 in the concave cavity 4-2, and insert the card connector 1-3 into the card slot 4-3 to complete the assembly, wherein the three-phase copper busbar and the PCB board 3 are all installed in the cavity after the current sensor lower shell 4 and the current sensor upper cover 1 are closed.

[0033] MCU peripheral circuits and power input circuits are also set on the PCB board 3. The power input circuit provides basic power supply voltage and electrical protection for the sensor. Each TMR chip 2 will feedback the size of the magnetic field generated by the current on the three-phase current busbar with a fixed gain and zero point. The MCU module will collect the output of each TMR chip 2 and convert it to obtain the corresponding current data. In addition to each corresponding TMR chip 2, the TMR chips 2 on the PCB board 3 are arranged in an interlaced form to measure external interference magnetic fields.

[0034] When using the three-phase array digital TMR current sensor, it is necessary to calibrate the three-phase array digital TMR current sensor in advance to obtain the contribution coefficient of each phase current to each TMR chip. When in use, the MCU module will first collect the data of each TMR chip 2, and apply at least three magnetic field data and the contribution coefficient obtained by calibration to calculate the magnetic field data respectively.

[0035] For example: use 3 sensors to measure three-phase current, the three-phase currents are I1, I2 and I3, and the outputs of the sensors are V1, V2 and V3, then the outputs of the sensors should satisfy the following equation:

[0036]

[0037] Where ai is the contribution coefficient of the three-phase current. During calibration, the sensor is calibrated with three-phase AC current. The number of calibration current points is at least 3. The more current points involved in the calibration, the more accurate the calibration data. Taking 3 calibration current points as an example, since the calibration current is three-phase current, 9 equations can be obtained. Solving the 9 equations can obtain a-i9 contribution coefficients. In actual use, each current point will have 3 sets of equations. Substituting V1-V3 and aj into the equations can solve the three current values ​​I1-I3.

[0038] When more than 3 magnetic sensors are used, the 4th sensor is mainly used to detect external magnetic interference. The sensors are calibrated using the above method, and there are a total of 12 calibration parameters.

[0039] When there is magnetic interference in the sensor's operating environment, the above equation will become as follows:

[0040]

[0041] Where H1 is the magnetic interference in the external environment. H1 can be calculated using the output of V4. Substituting H1 into the first three equations can calculate the current size under external interference.

[0042] In the above equation, the external interference is approximated, assuming that the external magnetic interference has the same effect on the four sensors. However, in actual use, the external interference magnetic field has different effects on the sensors, so the number of magnetic sensors can be increased or a weighted calculation method can be used to compensate the sensor current.

[0043] The sensor has a temperature compensation function. The method is to use the temperature sensor that comes with the MCU module to measure the ambient temperature. When the temperature difference of the sensor is large, the sensor is temperature calibrated. The sensor is in the range of -40-125, and the output current of the sensor is compensated for zero point and gain at intervals of 5°C. The temperature compensation parameters are obtained by actual testing of the sensor. Under normal circumstances, the sensor does not need to be temperature compensated.

[0044] The sensor has a frequency compensation function. Due to the skin effect of current in the copper busbar, the magnetic field around the three-phase copper busbar is positively correlated with the frequency of the current. The sensor can detect the frequency in the three-phase copper busbar in real time and use the frequency data to compensate the current of the sensor.

[0045] The three-phase array digital TMR current sensor also has a pulse detection function. The response time of the TMR chip 2 is less than 6us. In addition, the MCU module performs an output detection of the magnetic sensor every 10us. When the output of the sensor is found to increase suddenly or continuously exceed a certain threshold, the sensor uses the fast response mechanism set in the program to feedback the abnormality to the upper system. There are two ways of feedback. The abnormal data can be sent to the outside through the communication interface; the abnormality can be reported in a fast setting manner through a special abnormal output pin; the above abnormalities are overcurrent and short circuit. Both abnormalities will cause the measured current to rise rapidly or remain in a large state. The lower computer software determines which specific abnormality it is by collecting the current size.

[0046] The above-mentioned communication interfaces are serial communication, CAN communication, LIN communication, and SPI communication; these are realized by adding different peripheral communication chips to the sensor.

[0047] The three-phase array digital TMR current sensor also has a three-phase current balance detection function and a functional safety function. Under normal circumstances, the vector sum of the three-phase current is 0. The sensor determines the vector sum of the three-phase current in real time. When the vector sum is greater than the set threshold, the digital output interface is used to output an abnormal code of the three-phase current imbalance. The functional safety function uses the multiple TMR magnetic sensors in claim 1 as reference data. When one of the sensors fails, an error is reported to the outside through the digital communication interface, and the output current is calculated through the output of other adjacent current sensors. When a phase of the three-phase current fails completely, the current data of the other two phases is used to calculate the current data of the phase according to the vector balance principle.

[0048] Finally, it should be noted that the above-described implementation mode is only a preferred embodiment of the present invention to illustrate the technical solution of the present invention, and does not limit it, let alone limit the protection scope of the present invention; although the invention is described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the protection scope of the claims.

Claims

1. A three-phase array digital TMR current sensor, comprising a current sensor upper cover (1), a current sensor lower shell (4), and a PCB board (3), wherein the current sensor upper cover (1) is connected to the current sensor lower shell (4), and the PCB board (3) is located between the current sensor upper cover (1) and the current sensor lower shell (4), characterized in that: It also comprises a three-phase copper busbar and a plurality of TMR chips (2) for collecting magnetic field data generated by current passing through the three-phase copper busbar. The TMR chips (2) are welded on a first straight line or a second straight line on a PCB (3). The spacing between the TMR chips (2) welded on the first straight line of the PCB (3) is the same as the spacing between the TMR chips (2) welded on the second straight line of the PCB (3). The TMR chips (2) are arranged on the PCB (3) in an array. The PCB (3) is also provided with an MCU module for collecting the output of the TMR chips (2) and calculating the current value on each phase of the three-phase copper busbar. The MCU module has a built-in temperature compensation algorithm, a current secondary calibration algorithm, and a frequency checking and compensation algorithm. The working process of the built-in temperature compensation algorithm is to perform table lookup compensation on the zero point and gain of the sensor through temperature data fed back by the temperature sensor. The formula is as follows: y=k t x+b t In the formula, y is the output after temperature compensation; x is the current output; kt is the gain temperature compensation coefficient at the current temperature point; bt is the zero temperature compensation coefficient at the current temperature point. In practical applications, the values ​​of kt and bt are queried according to the current temperature point to calculate the current. The frequency measurement and detection algorithm measures the frequency of the primary current in real time and compensates the output current according to the measurement result. The compensation formula is: y=k f x+b f Where y is the output after frequency compensation, x is the current output, kf is the gain compensation coefficient at the current frequency point, and bf is the compensation coefficient at the current frequency point. In practical applications, the values ​​of kf and bf are queried according to the current frequency point to perform current calculations.

2. A three-phase array digital TMR current sensor according to claim 1, characterized in that: The number of TMR chips (2) on the PCB board (3) is ≥3.

3. A three-phase array digital TMR current sensor according to claim 1, characterized in that: The current sensor upper cover (1) comprises a bottom (1-1) and a wall portion (1-2), a plurality of clamping joints (1-3) are provided on the wall portion (1-2), the current sensor lower shell (4) comprises a lower shell body (4-1), a concave cavity (4-2) is provided on the lower shell body (4-1), a plurality of clamping grooves (4-3) are provided on the wall surface of the concave cavity (4-2), and the clamping joints (1-3) cooperate with the clamping grooves (4-3).

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