Method and device for cancelling external magnetic disturbances of a current sensor of the hall effect

Abstract

The application discloses a kind of external magnetic interference elimination method and device of Hall effect current sensor, belong to sensor chip technical field, based on pre-recorded drive current value, adjust the corresponding proportion of current I1 output by adjustable current source;Adjust the fixed current value I2 output by fixed current source, wherein I1=I2H2 / H1, H1 is the output signal of the first Hall unit, H2 is the output signal of the second Hall unit;Based on the current I1 and the current I2, the first Hall unit and the second Hall unit are driven respectively, and the common-mode signal introduced by external magnetic field is eliminated.The application effectively solves the problem that external magnetic field interference caused by sensitivity mismatch introduced by CMOS manufacturing process is difficult to eliminate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensor chip, in particular to an external magnetic interference elimination method and device of a Hall effect current sensor. BACKGROUND

[0002] The current sensor based on Hall effect utilizes the current flowing through the conductor to generate a corresponding magnetic field, and the magnetic field passes through the adjacent Hall cell to generate a Hall voltage, and the Hall voltage can be measured to calculate the current flowing through the conductor.

[0003] The Hall sensor unit based on CMOS process is an important component of the current sensor chip. When the sensor works in a strong magnetic field environment, such as near a motor motor, in order to overcome the interference of the external magnetic field, a Hall cell is placed on both sides of the lead wire through which a large current flows in the current sensor chip, to offset the common-mode signal introduced by the external magnetic field; At this time, the differential mode of the output voltage of the two Hall cells is taken as the input of the next differential amplifier circuit.

[0004] For example, the patent application for an invention with publication number CN109143122A proposes a Hall sensor. The defect of this scheme is that the CMOS manufacturing process cannot guarantee that the sensitivities of the two Hall elements at different positions on the chip, i.e. the linear slope of the input current and the output voltage, are completely matched. This mismatch results in incomplete elimination of the common-mode signal, thereby affecting the accuracy of the entire current sensor.

[0005] The patent application document with publication number CN109564248A proposes a current sensor with a first Hall element and a second Hall element. In this scheme, the sensitivity between the two Hall cells is calibrated in real time by the magnetic field generated by the calibration coil inside the circuit. A series of timing operations are designed inside the circuit, and how to use the coil and the subsequent comparison circuit to gradually correct the sensitivity error is described. However, this scheme constantly calibrates the magnetic field generated by the two calibration coils, and there is a problem of matching the magnetic field between the two coils. During the calibration process, it also brings certain error; Secondly, the current driving the coil will bring additional power consumption. SUMMARY

[0006] The technical problem to be solved by the present application is how to solve the problem of difficult elimination of external magnetic field interference caused by sensitivity mismatch introduced by CMOS manufacturing process, and realize one-time calibration of Hall cell sensitivity.

[0007] The present application solves the above technical problems by the following technical means:

[0008] In one aspect, the application provides a method for eliminating external magnetic interference of a Hall effect current sensor. The method includes the following steps: placing a first Hall unit and a second Hall unit on both sides of a wire through which a current to be measured flows in the current sensor; connecting a drive end of the first Hall unit to an adjustable current source; connecting a drive end of the second Hall unit to a fixed current source; adjusting an output current I1 of the adjustable current source based on a pre-recorded drive current value; adjusting an output fixed current value I2 of the fixed current source, where I1 = I2H2 / H1, H1 is an output signal of the first Hall unit, and H2 is an output signal of the second Hall unit; and driving the first Hall unit and the second Hall unit based on the current I1 and the current I2, respectively, to eliminate common-mode signals introduced by an external magnetic field.

[0009] adjusting an output current I1 of the adjustable current source based on a pre-recorded drive current value;

[0010] adjusting an output fixed current value I2 of the fixed current source, where I1 = I2H2 / H1, H1 is an output signal of the first Hall unit, and H2 is an output signal of the second Hall unit;

[0011] driving the first Hall unit and the second Hall unit based on the current I1 and the current I2, respectively, to eliminate common-mode signals introduced by an external magnetic field.

[0012] Further, before adjusting the output current I1 of the adjustable current source based on the pre-recorded drive current value, the method further includes the following steps:

[0013] recording Hall voltages V 1(+) and V 2(+) generated by the two Hall units when an external magnetic field B+ is applied to the current sensor;

[0014] recording Hall voltages V 1(-) and V 2(-) generated by the two Hall units when an external magnetic field B- is applied to the current sensor, where B+ and B- have the same magnetic field strength but opposite directions;

[0015] calculating the output signal H1 of the first Hall unit and the output signal H2 of the second Hall unit based on the Hall voltages V 1(+) and V 2(+) and the Hall voltages V 1(-) and V 2(-) ;

[0016] calculating the pre-recorded drive current as I2 / p based on the drive current value I2 of the second Hall unit, where p = H1 / H2.

[0017] Further, the calculation of the output signal H1 of the first Hall unit and the output signal H2 of the second Hall unit based on the Hall voltages V 1(+) and V 2(+) and the Hall voltages V 1(-) and V 2(-) includes the following steps:

[0018] calculating the output signal of the first Hall unit as H1=(V 1(+) -V 1(-) ) / 2;

[0019] calculating the output signal of the second Hall unit as H2=(V 2(+) -V 2(-) ) / 2.

[0020] Further, after calculating the pre-engraved driving current as I2 / p, p=H1 / H2 based on the driving current value I2 of the second Hall unit, the method further comprises:

[0021] converting the driving current I2 / p into binary data according to a coding rule and burning into a ROM.

[0022] Further, adjusting the output current I1 of the adjustable current source in a corresponding proportion based on the pre-engraved driving current value comprises:

[0023] using a decoder to analyze the current binary data pre-engraved in the ROM to obtain a current analysis value;

[0024] using a digital-to-analog conversion circuit to convert the current analysis value into a current I1 in a corresponding proportion.

[0025] In a second aspect, the application further provides an external magnetic interference elimination device for a Hall effect current sensor, the device comprising an adjustable current source, a fixed current source, and a read-only memory, the read-only memory having a pre-engraved driving current value, the output end of the read-only memory being connected to the adjustable current source, the outputs of the adjustable current source and the fixed current source being connected to a first Hall unit and a second Hall unit, respectively.

[0026] The adjustable current source adjusts the output current I1 in a corresponding proportion based on the pre-engraved driving current value in the memory to drive the first Hall unit.

[0027] The fixed current source outputs a fixed current value I2 to drive the second Hall unit, wherein I1=I2H2 / H1, H1 is the output signal of the first Hall unit, and H2 is the output signal of the second Hall unit.

[0028] Further, the adjustable current source comprises a decoder, a digital-to-analog conversion circuit, and a voltage source, the input end of the decoder being connected to the output end of the memory, the output end of the decoder being connected to the input end of the digital-to-analog conversion circuit, and the output end of the digital-to-analog conversion circuit being connected to the voltage source.

[0029] Further, the digital-to-analog conversion circuit comprises a plurality of PMOS tubes, a gate of each of the PMOS tubes is connected to an output of the decoder, a source of each of the PMOS tubes is connected to the voltage source, and a drain of each of the PMOS tubes is connected to the fixed current source.

[0030] Further, the fixed current source provides a reference current flowing through the first Hall unit and the second Hall unit simultaneously, and the current flowing through each of the PMOS tubes is same or different and is less than the reference current.

[0031] The present application has the advantages of:

[0032] (1) The present application connects a driving end of one of the two Hall units placed on both sides of the wire through which the current to be measured flows in the current sensor to an adjustable current source, adjusts the adjustable current source to output a corresponding proportional current value I1 based on a pre-recorded driving current value, adjusts a fixed current source to output a fixed current value I2, and when the first Hall unit and the second Hall unit are driven by the two current values respectively, the common-mode signal introduced by the external magnetic field can be completely eliminated, the sensitivity error between the two Hall units can be calibrated once, the sensitivity of the two Hall units can be matched, the problem that the external magnetic field interference caused by the sensitivity mismatch introduced by the CMOS manufacturing process is difficult to eliminate can be effectively solved, and the precision of the sensor is improved.

[0033] Additional aspects and advantages of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood by the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a flowchart of the external magnetic interference elimination method of the Hall effect current sensor in the present application;

[0035] Figure 2 is a schematic diagram of the principle of eliminating common-mode magnetic field interference in the present application;

[0036] Figure 3 is a structural schematic diagram of the external magnetic interference elimination device of the Hall effect current sensor in the present application;

[0037] Figure 4 is a structural schematic diagram of the adjustable current source in the present application. DETAILED DESCRIPTION

[0038] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0039] With reference to Figure 1 The embodiments of the present application provide a method for eliminating external magnetic interference of a Hall-effect current sensor. First and second Hall units are respectively arranged on two sides of a wire through which a to-be-measured current flows in the current sensor. A driving end of the first Hall unit is connected to an adjustable current source, and a driving end of the second Hall unit is connected to a fixed current source. The method comprises the following steps.

[0040] S10. Based on a pre-recorded driving current value, an adjustable current source outputs a corresponding proportional current I1.

[0041] S20. A fixed current source outputs a fixed current value I2, where I1=I2H2 / H1, H1 is an output signal of the first Hall unit, and H2 is an output signal of the second Hall unit.

[0042] S30. Based on the current I1 and the current I2, the first Hall unit and the second Hall unit are respectively driven to eliminate the common-mode signal introduced by the external magnetic field.

[0043] In the embodiments, the adjustable current source outputs a corresponding proportional current value I1 based on a pre-recorded driving current value, and a fixed current source outputs a fixed current value I2. When the first Hall unit and the second Hall unit are respectively driven by the two current values, the common-mode signal introduced by the external magnetic field can be completely eliminated, that is, I1Q1=I2Q2, and one-time calibration of the sensitivity error between the two Hall units is realized.

[0044] Specifically, the output voltage U of the Hall unit is proportional to the driving current I of the Hall unit and the magnetic induction intensity B in the vertical direction of the Hall unit, and the proportionality coefficient Q, that is, the sensitivity, is related to the chip technology (such as the actual doping concentration and doping implantation depth of the element position), and has a small amplitude fluctuation within a certain range, which is expressed by the following formula:

[0045] U=IQB.

[0046] When there is a to-be-measured current I e When the current I e flows through the side of the Hall unit, a magnetic field perpendicular to the Hall unit is generated, and the intensity B is proportional to I e, the proportionality coefficient k is related to the shape and position of the wire through which the current to be measured is passed in the chip. At this time, the output voltage U of the Hall cell is proportional to the current to be measured Ie.

[0047] However, when there is an interfering strong magnetic field B e outside the chip, this strong magnetic field will be superimposed on the magnetic induction B in the above formula, that is:

[0048] U = IQ(kI e +B e ).

[0049] At this time, the output voltage of the Hall cell is no longer proportional to the current to be measured, and an additional error term is introduced.

[0050] If two Hall cells are placed on both sides of the wire through which the current to be measured is passed in the chip, as shown in Figure 2 , the extra error term can be eliminated to some extent. The magnetic field directions generated by the current on the two Hall cells are opposite, while the direction of the external interference magnetic field is the same; the former is a differential mode signal for the subsequent differential amplification circuit, and the latter is a common mode signal. Then we have:

[0051] U1 = I1Q1(k1I e +B e )

[0052] U2 = I2Q2(k2I e +B e )

[0053] Where U1, I1, Q1, and k1 are the output voltage, driving current, sensitivity, and proportionality coefficient of the first Hall cell, respectively, and U2, I2, Q2, and k2 are the output voltage, driving current, sensitivity, and proportionality coefficient of the second Hall cell, respectively.

[0054] However, due to the CMOS manufacturing process, the sensitivities Q of the two Hall cells will not match, denoted as Q1 and Q2. After the two voltages are sent to the subsequent differential amplification circuit, the actual signal to be amplified is:

[0055] ΔU = U1-U2 = (I1Q1k1-I2Q2k2)I e +(I1Q1-I2Q2)B e

[0056] Where the effective differential mode signal to be amplified is (I1Q1k1-I2Q2k2)I e , which is proportional to the current to be measured I e ; the additional intercept term (I1Q1-I2Q2)B eWill cause the common mode signal can not be completely eliminated, affect the accuracy of the whole current sensor; the embodiment is just by adjusting the current of the calibration adjustable current source I1, eliminating the sensitivity difference of the two hall units in the later test link.

[0057] Specifically, because the CMOS manufacturing process causes the sensitivity Q of the two hall components to be unmatched, in order to achieve the same sensitivity of the two hall components, after the two voltage signals are sent to the subsequent differential amplifier circuit, the actual amplified signal value needs to be △U=U1-U2=0, that is, (I1Q1k1-I2Q2k2)I e +(I1Q1-I2Q2)B e =0.

[0058] Assuming that the value of the current I e to be measured is zero, (I1Q1k1-I2Q2k2)I e =0, from which it can be known that (I1Q1-I2Q2)B e =0, that is, I1Q1=I2Q2.

[0059] Because the sensitivity Q values of the two hall units are different, the driving current connected to the hall unit needs to be adjusted, and in the embodiment, the driving current of the second hall unit is set to a constant I2, and the driving current I1 of the first hall unit is adjusted to I1=I2Q2 / Q1, and the driving current value I1 is pre-recorded to be used to drive the first hall unit after the circuit is powered on again, so as to complete the sensitivity matching between the two hall units.

[0060] In an embodiment, before the step S10 of adjusting the adjustable current source to output a corresponding proportional current I1 based on the pre-recorded driving current value, the method further includes the following steps:

[0061] S11, when an external magnetic field B+ is applied to the current sensor, the hall voltages V 1(+) and V 2(+) generated by the two hall units are recorded respectively;

[0062] S12, when an external magnetic field B- is applied to the current sensor, the hall voltages V 1(-) and V 2(-) generated by the two hall units are recorded respectively, wherein the magnetic field sizes of B+ and B- are the same and the directions are opposite;

[0063] S13, based on the hall voltages V 1(+) and V 2(+) and the hall voltages V 1(-) and V 2(-) , the output signal H1 of the first hall unit and the output signal H2 of the second hall unit are calculated.

[0064] S14, calculating a pre-engraved driving current I2 / p, p=H1 / H2 based on the driving current value I2 of the second Hall unit.

[0065] In an embodiment, the step S13, calculating the output signal H1 of the first Hall unit and the output signal H2 of the second Hall unit based on the Hall voltage V 1(+) and V 2(+) , comprises: 1(-) and V 2(-) .

[0066] calculating the output signal H1 of the first Hall unit as H1=(V 1(+) -V 1(-) ) / 2;

[0067] calculating the output signal H2 of the second Hall unit as H2=(V 2(+) -V 2(-) ) / 2.

[0068] Specifically, V 1(+) =H 1(+) +Ofst1; V 2(+) =H 2(+) +Ofst2, wherein Ofst1 and Ofst2 are the offset voltages of the two Hall units, which are constant values irrelevant to the size of the external magnetic field, H 1(+) is the output value of the first Hall unit under the positive magnetic field, and H 2(+) is the output value of the second Hall unit under the positive magnetic field; V 1(-) =H 1(-) +Ofst1; V 2(-) =H 2(-) +Ofst2, wherein Ofst1 and Ofst2 are the offset voltages of the two Hall units, which are constant values irrelevant to the size of the external magnetic field, H 1(-) is the output value of the first Hall unit under the negative magnetic field, and H 2(-) is the output value of the second Hall unit under the negative magnetic field.

[0069] calculating (V 1(+) -V 1(-) ) / 2=(H 1(+) -H 1(-) ) / 2=H1, which represents the output signal of the first Hall unit;

[0070] calculating (V 2(+) -V 2(-) ) / 2=H 2(+) -H 2(-) ) / 2=H2, which represents the output signal of the second Hall unit.

[0071] In one embodiment, after the step S14: calculating the pre-etched driving current value I2 / p, p=H1 / H2 based on the driving current value I2 of the second Hall unit, the method further comprises the following steps:

[0072] Converting the driving current I2 / p into binary data according to the encoding rule and burning into the ROM.

[0073] It should be noted that the tested driving current value is converted into binary data according to the encoding rule and burned into the memory ROM, and after the circuit is powered on again, the first Hall unit will be driven by the updated driving current, realizing the sensitivity matching calibration between the two Hall units.

[0074] In one embodiment, the step S10: adjusting the output current I1 of the adjustable current source in a corresponding proportion based on the pre-etched driving current value, specifically comprises the following steps:

[0075] S11, using a decoder to analyze the current binary data pre-etched in the ROM to obtain a current analysis value;

[0076] S12, using a digital-to-analog conversion circuit to convert the current analysis value into a corresponding proportion of current I1.

[0077] As shown in Figures 3 to 4 The second embodiment of the present application proposes an external magnetic interference elimination device of a Hall effect current sensor, which comprises an adjustable current source 10, a fixed current source 11 and a read-only memory 3, the read-only memory 3 has pre-etched driving current values, the output end of the read-only memory 1 is connected to the adjustable current source 10, and the outputs of the adjustable current source 10 and the fixed current source 11 are respectively connected to a first Hall unit 1 and a second Hall unit 2.

[0078] The adjustable current source 10 adjusts the output current I1 in a corresponding proportion based on the pre-etched driving current value in the memory 3 to drive the first Hall unit 1.

[0079] The fixed current source 11 outputs a fixed current value I2 to drive the second Hall unit 2, wherein I1=I2H2 / H1, H1 is the output signal of the first Hall unit, and H2 is the output signal of the second Hall unit.

[0080] The embodiment improves the drive constant current source of one of the Hall units into an adjustable current source, uses the characteristics of the sensitivity of the Hall unit related to the input current, adjusts the input current of the Hall unit in the later test link, achieves the effect of adjusting the sensitivity of the Hall assembly, and then matches the sensitivities of the two Hall units, and permanently saves the calibrated sensitivity in the memory device. When the circuit is powered on again, the updated driving current will be used to drive the first Hall unit, and the sensitivity matching and calibration between the two Hall units are completed.

[0081] Specifically, Figure 3 In the middle, "Adjustable Current Source Circuit" means adjustable current source 10, and the adjustable current source must have the following functions: (1) The decoder 12 analyzes the binary data pre-recorded in the memory ROM; (2) The digital-to-analog conversion circuit 13 of the current mode can generate a corresponding proportional current as the adjustable current source I1 according to the value generated by the decoder 12; (3) A fixed current source I2 can be generated.

[0082] "ROM" is a read-only memory 3 that can be used to store calibration data;

[0083] "Comm.Interface" is an interface 4 that can handle specific communication protocols, and can refresh the data of the ROM according to the information received by the interface.

[0084] In an embodiment, as Figure 4 shown, the adjustable current source 10 includes a decoder 12, a digital-to-analog conversion circuit 13, and a voltage source 14, the input end of the decoder 12 is connected to the output end of the memory 3, the output end of the decoder 12 is connected to the input end of the digital-to-analog conversion circuit 13, and the output end of the digital-to-analog conversion circuit 13 is connected to the voltage source 14.

[0085] In an embodiment, the digital-to-analog conversion circuit 13 includes a plurality of PMOS tubes, the gate of each PMOS tube is connected to the output of the decoder 12, the source of each PMOS tube is connected to the voltage source 14, and the drain of each PMOS tube is connected to the fixed current source 11.

[0086] It should be noted that the drive current source for adjusting the Hall element is a digital signal (the data is discrete data, outputting high or low level), which needs to be converted into an analog signal (the data changes continuously) through a digital-to-analog conversion circuit, so that the Hall element can be driven by the analog signal. Figure 4As shown in the 8-bit digital-to-analog converter, 8 PMOS transistors are used as switches with their source terminals connected to a voltage source, and their gate terminals controlled by digital signals outputted by a decoder. The control signals of each PMOS transistor are determined by the data read from a ROM. The drain terminals of each PMOS transistor are connected in series with a fixed current source. The output current is obtained by summing the currents of all the switches to drive the first Hall cell. The current value obtained by the summation is the driving current source value of the first Hall cell.

[0087] In an embodiment, the fixed current source 11 provides a reference current flowing through the first Hall cell and the second Hall cell. The current flowing through each PMOS transistor is the same or different and is less than the reference current.

[0088] It should be noted that the current I_# flowing through each PMOS transistor is the same or different, and the weight of each current can be adjusted according to requirements. I_base is a reference current provided by a fixed current source. The reference current flows through the first Hall cell and the second Hall cell. By setting the reference current, each current I_# can be set to a relatively smaller current to achieve more detailed sensitivity adjustment.

[0089] Further, when the memory burn-in driving current value is performed, the device used for calibration needs to be matched to test the driving current value. For example, as shown in the figure, the "PC & Program" is a computer 5, and a calibration program is run in the computer. The calibration program must be able to control the following units: "DMM", "Magnetic Field Generator", and "Comm.Interface". Figure 3

[0090] The DMM is a digital multimeter 6 used to measure the Hall voltages V1 and V2.

[0091] The Magnetic Field Generator is a magnetic field generating device 7 capable of generating two uniform magnetic fields B+ and B- in the integrated circuit region. B+ and B- are the same magnetic field size but opposite directions, satisfying the operation relationship B+ = (-1) * B-.

[0092] The Comm.Interface is a tool capable of refreshing the ROM content through a specific communication protocol. The communication protocol is not limited as long as it can meet the function.

[0093] The specific calibration process is as follows:

[0094] ​(1) Control the Magenetic Field Generator to generate magnetic field B+ in the area of the interference elimination device; record the voltage V 1(+) = H 1(+) + Ofst1; V 2(+) = H 2(+) + Ofst2.

[0095] (2) Control the Magenetic Field Generator to generate magnetic field B- in the area of the integrated circuit; record the voltage V 1(-) = H 1(-) + Ofst1; V 2(-) = H 2(-) + Ofst2.

[0096] (3) Calculate (V 1(+) -V 1(-) ) / 2 = (H 1(+) -H 1(-) ) / 2 = H1, which represents the output signal of the first Hall unit;

[0097] Calculate (V 2(+) -V 2(-) ) / 2 = (H 2(+) -H 2(-) ) / 2 = H2, which represents the output signal of the second Hall unit.

[0098] (4) Since the second Hall unit is driven by a constant current source, take the signal as a reference to calculate p = H1 / H2.

[0099] (5) Derive the sensitivity error between the Hall units, and it is known that adjusting the driving current to I2 / p can make the sensitivities of the two Hall units match.

[0100] (6) Convert the driving current I2 / p into binary data according to the coding rule and burn it into the ROM.

[0101] It should be noted that other embodiments of the external magnetic interference elimination device of the Hall effect current sensor or the implementation method of the present application can refer to the above-mentioned method embodiments, which will not be repeated here.

[0102] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the description of the specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0103] In addition, the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0104] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method of external magnetic interference cancellation for a Hall effect current sensor, comprising: The first Hall unit and the second Hall unit are respectively arranged on both sides of a wire through which a current to be measured flows in a current sensor, a driving end of the first Hall unit is connected to an adjustable current source, and a driving end of the second Hall unit is connected to a fixed current source, and the method comprises the following steps: Adjusting the adjustable current source to output a corresponding proportional current I1 based on a pre-recorded driving current value; Adjusting the fixed current source to output a fixed current value I2, wherein I1=I2H2 / H1, H1 is an output signal of the first Hall unit, and H2 is an output signal of the second Hall unit; Driving the first Hall unit and the second Hall unit based on the current I1 and the current I2 respectively to eliminate a common-mode signal introduced by an external magnetic field.

2. The method of external magnetic interference cancelation for a Hall effect current sensor as defined in claim 1, wherein, Before the step of adjusting the adjustable current source to output a corresponding proportional current I1 based on a pre-recorded driving current value, the method further comprises the following steps: The Hall voltages V generated by the two Hall cells are recorded respectively when an external magnetic field B+ is applied to the current sensor 1(+) and V 2(+) ; The Hall voltages V generated by the two Hall units are recorded respectively when an external magnetic field B- is applied to the current sensor 1(-) and V 2(-) wherein the magnetic field sizes of B+ and B- are the same and the directions are opposite. based on the Hall voltage V 1(+) and V 2(+) and the Hall voltage V 1(-) and V 2(-) , the output signal H1 of the first Hall cell and the output signal H2 of the second Hall cell are calculated; Calculating a pre-recorded driving current as I2 / p based on a driving current value I2 of the second Hall unit, wherein p=H1 / H2.

3. The method of external magnetic interference cancelation for a Hall effect current sensor as defined in claim 2, wherein, The Hall voltage V 1(+) and V 2(+) and the Hall voltage V 1(-) and V 2(-) , calculating the output signal H1 of the first Hall cell and the output signal H2 of the second Hall cell, comprises: computing an output signal of the first Hall cell as H1 = (V 1(+) -V 1(-) ) / 2; The output signal of the second Hall cell is calculated as H2 = (V 2(+) -V 2(-) ) / 2.

4. The method of external magnetic interference cancelation for a Hall effect current sensor as defined in claim 2, wherein, After the step of calculating a pre-recorded driving current as I2 / p based on a driving current value I2 of the second Hall unit, wherein p=H1 / H2, the method further comprises the following steps: Converting the driving current I2 / p into binary data according to a coding rule and burning the binary data into a ROM.

5. The method of external magnetic interference cancellation for a Hall effect current sensor as defined in claim 4, wherein, The step of adjusting the adjustable current source to output a corresponding proportional current I1 based on a pre-recorded driving current value comprises the following steps: Analyzing current binary data pre-recorded in the ROM by using a decoder to obtain a current analysis value; Converting the current analysis value into a corresponding proportional current I1 by using a digital-to-analog conversion circuit.

6. An external magnetic interference canceling device for a Hall effect current sensor, characterized by, The device comprises an adjustable current source, a fixed current source and a read-only memory, the read-only memory has a pre-recorded driving current value, an output end of the read-only memory is connected to the adjustable current source, and outputs of the adjustable current source and the fixed current source are respectively connected to a first Hall unit and a second Hall unit; The adjustable current source adjusts its output to a corresponding proportional current I1 based on a pre-recorded driving current value in the memory to drive the first Hall unit; The fixed current source outputs a fixed current value I2 to drive the second Hall unit, wherein I1=I2H2 / H1, H1 is an output signal of the first Hall unit, and H2 is an output signal of the second Hall unit.

7. The external magnetic interference canceling device for a Hall effect current sensor according to claim 6, characterized by, The adjustable current source comprises a decoder, a digital-to-analog conversion circuit and a voltage source, an input end of the decoder is connected to an output end of the memory, an output end of the decoder is connected to an input end of the digital-to-analog conversion circuit, and an output end of the digital-to-analog conversion circuit is connected to the voltage source.

8. The external magnetic interference canceling device for a Hall effect current sensor according to claim 7, characterized by, The digital-to-analog conversion circuit comprises a plurality of PMOS tubes, a gate of each PMOS tube is connected to an output of the decoder, a source of each PMOS tube is connected to the voltage source, and a drain of each PMOS tube is connected to the fixed current source.

9. The external magnetic interference canceling device for a Hall effect current sensor according to claim 8, characterized by, The fixed current source provides a reference current flowing through the first Hall unit and the second Hall unit simultaneously, a current flowing through each PMOS tube is the same or different and is smaller than the reference current.

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