Temperature compensation circuit and current sensor

Abstract

The application relates to the technical field of sensors and discloses a temperature compensation circuit and a current sensor. The application adds a grounding circuit to the Wheatstone bridge, the grounding circuit makes the output voltage of the Wheatstone bridge irrelevant to temperature, so that the compensation of the temperature drift of the sensor is completed, the working mode switching of the power management module is carried out, the accuracy of the current sensor is improved, the performance of the sensor does not need to be tested in advance for compensation, the uniformity requirement of the performance of the sensor is low, and the application is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, specifically to a temperature compensation circuit and a current sensor. Background Technology

[0002] As the energy industry transitions towards clean, low-carbon, safe, and efficient operations, there is an urgent need for highly sensitive and reliable sensors in power grids and new energy vehicles. Facing the digital transformation of the power grid and the wide-area, distributed, panoramic information sensing of the "source-grid-load-storage" system, miniaturized, highly sensitive, and low-power magnetic sensors are needed to provide high-precision sensing and measurement capabilities of AC and DC magnetic fields and current signals under complex operating conditions, thus providing crucial guarantees for the safe operation of power grid equipment and reliable power supply. Currently, the main methods for current measurement include current transformers, shunt resistors, fiber optic current transformers, zero-flux current transformers, and current sensors based on magnetic chips. Tunneling magnetoresistive devices (TMRs) are the latest generation of magnetic field measurement technology based on the magnetoresistive effect. Compared with traditional Hall devices, anisotropic magnetoresistive devices, and giant magnetoresistive devices, they possess higher sensitivity and have broad application prospects in the field of power system current measurement.

[0003] However, TMR also suffers from temperature drift, resulting in unstable output at different temperatures. The conventional compensation method requires prior testing of the TMR's performance and the use of appropriate algorithms for compensation. The drawback of this method is that it necessitates performance testing for each TMR device before shipment, making it unsuitable for large-scale mass production. Summary of the Invention

[0004] In view of this, the present invention provides a temperature compensation circuit and a current sensor to solve the problem that conventional TMR compensation methods require prior testing of TMR performance and compensation using algorithms. The drawback of this method is that it requires performance testing of each TMR device before it leaves the factory, which is not suitable for large-scale mass production.

[0005] In a first aspect, the present invention provides a temperature compensation circuit applied to a sensor based on a Wheatstone bridge. The first power supply terminal of the Wheatstone bridge is connected to a first power supply. The circuit includes a grounding circuit, an amplification circuit, and a division circuit. The grounding circuit has a first terminal connected to the second power supply terminal of the Wheatstone bridge and a second terminal grounded, which is used to make the output voltage of the Wheatstone bridge independent of temperature. The amplification circuit has a first input terminal and a second input terminal connected to the first output terminal and the second output terminal of the Wheatstone bridge, respectively, and its output terminal connected to the first input terminal of the division circuit, which is used to amplify the output voltage of the Wheatstone bridge. The voltage between the output terminal of the amplification circuit and the second power supply terminal of the Wheatstone bridge is the temperature-compensated voltage of the Wheatstone bridge.

[0006] This invention compensates for the temperature drift of the TMR by adding a grounding circuit, thereby improving the accuracy of the current sensor. Furthermore, it eliminates the need to test the performance of the TMR beforehand for compensation, thus having lower requirements for the performance uniformity of the TMR and making it suitable for mass production.

[0007] In one alternative embodiment, the temperature compensation circuit further includes a division circuit, the second input of which is connected to the second power supply terminal of the Wheatstone bridge, for calculating the voltage ratio between the output voltage of the amplifier circuit and the voltage of the ground circuit, the voltage ratio being used to calculate the current.

[0008] In one alternative implementation, the grounding circuit includes a grounding resistor.

[0009] In one optional embodiment, the division circuit includes: a first logarithmic operation circuit, a second logarithmic operation circuit, a subtraction operation circuit, and an exponential operation circuit. The first logarithmic operation circuit has its input terminal connected to the output terminal of the amplifier circuit, and its output terminal connected to the first input terminal of the subtraction operation circuit. It is used to take the logarithm of the amplifier circuit's output voltage. The second logarithmic operation circuit has its input terminal connected to the second power supply terminal of the Wheatstone bridge, and its output terminal connected to the second input terminal of the subtraction operation circuit. It is used to take the logarithm of the ground circuit voltage. The subtraction operation circuit has its output terminal connected to the input terminal of the exponential operation circuit, and its output terminal connected to the input terminal of the exponential operation circuit. It is used to subtract the two input voltages. The exponential operation circuit performs an exponential operation on the input voltages and outputs the ratio of the amplifier circuit's output voltage to the ground circuit voltage.

[0010] In one optional embodiment, both the first logarithmic operation circuit and the second logarithmic operation circuit include: a first resistor, a second resistor, a first operational amplifier, and a first switch. The first operational amplifier has its non-inverting input connected to a second power supply through the first resistor, and its inverting input connected to the output of the amplifier circuit or the second power supply of the Wheatstone bridge through the second resistor. The first terminal of the first switch is connected to the first output terminal. The second terminal of the first switch is connected to the inverting input of the first operational amplifier, and its control terminal is connected to a third power supply.

[0011] In one optional embodiment, the subtraction circuit includes: a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a second operational amplifier, and a second switch. The second operational amplifier has its non-inverting input connected to the output of the first logarithmic operation circuit via the third resistor, and its non-inverting input also connected to a second power supply via the fourth resistor. Its inverting input is connected to the output of the second logarithmic operation circuit via the fifth resistor, and its output is connected to its inverting input via the sixth resistor. Its output is also connected to the first terminal and the control terminal of the second switch. The second switch has its second terminal connected to the input of the exponential operation circuit.

[0012] In one optional implementation, the exponential operation circuit includes a seventh resistor, an eighth resistor, and a third operational amplifier. The third operational amplifier has its non-inverting input connected to a second power supply via the seventh resistor, its inverting input connected to the output of the subtraction operation circuit, and its output connected to its inverting input via the eighth resistor. The output of the third operational amplifier is the ratio of the output voltage of the amplifier circuit to the voltage of the ground circuit.

[0013] In one alternative implementation, the division circuit includes a digital signal processing chip.

[0014] In one alternative implementation, the digital signal processing chip calculates the magnetic field strength of the Wheatstone bridge according to the following formula:

[0015]

[0016] In the formula, V0 is the ratio of the amplifier circuit output voltage to the ground circuit voltage, V1 is the output voltage of the Wheatstone bridge, V2 is the ground circuit voltage, and R... C Δ is the grounding resistance value, Gain is the amplifier gain, and Δ is the coefficient related to the magnetic field strength.

[0017] In a second aspect, the present invention provides a current sensor, comprising: a Wheatstone bridge and a temperature compensation circuit according to the first aspect and any optional embodiment thereof.

[0018] This invention utilizes a temperature compensation circuit to compensate the Wheatstone bridge. By adding a grounding circuit to the temperature compensation circuit, the output voltage of the Wheatstone bridge becomes independent of temperature, thereby improving the accuracy of current detection.

[0019] In one alternative implementation, the Wheatstone bridge has four arms, each with a ninth resistor. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the temperature compensation circuit and current sensor according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of another temperature compensation circuit and current sensor according to an embodiment of the present invention;

[0023] Figure 3 This is a specific circuit topology diagram of the division circuit according to an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] According to an embodiment of the present invention, a temperature compensation circuit is provided, which is applied to a sensor based on a Wheatstone bridge, such as... Figure 1 As shown, the Wheatstone bridge consists of four arms, each of which is equipped with a magnetic susceptor (R1 to R4). The temperature compensation circuit includes: grounding circuit 11, amplification circuit 12, and division circuit 13.

[0026] like Figure 1 As shown, the Wheatstone bridge has its first power supply terminal connected to a first power supply, its second power supply terminal connected through the first terminal of the grounding circuit 11, and its first output terminal and second output terminal connected to the first input terminal and second input terminal of the amplifier circuit 12, respectively.

[0027] Specifically, such as Figure 1 As shown, among the four magnetoresistors, R1 and R4 have the same magnetic sensitivity direction, R2 and R3 have the same magnetic sensitivity direction, and R1 and R2 have opposite magnetic sensitivity directions. When there is no magnetic field, the resistance of R1 to R4 is R. When the magnetic field changes, the resistance of R2 and R3 increases by Δ, and the resistance of R1 and R4 decreases by Δ. At this time, V is obtained. OUT It is used to characterize the magnitude of the magnetic field.

[0028]

[0029]

[0030]

[0031] However, under the influence of temperature, the resistance values ​​of R1 to R4 change. We can assume that the amount of resistance change caused by temperature is T. Since the four bridge resistors are at the same temperature, the amount of change is the same.

[0032] at this time:

[0033] R1=R4=R-Δ+T (4)

[0034] R2=R3=R+Δ+T (5)

[0035]

[0036]

[0037]

[0038] V OUT There is a temperature-related variable T that affects the calculation results of the magnetic field.

[0039] like Figure 1 As shown, grounding circuit 11, with its second terminal grounded, is used to make the output voltage of the Wheatstone bridge independent of temperature.

[0040] Specifically, in this embodiment... Figure 1 The diagram shows that a temperature-insensitive grounding circuit 11 is added to the ordinary Wheatstone bridge. The resistance of the grounding circuit 11 does not change with temperature, and makes equation (8) independent of the variable T, thereby achieving temperature compensation.

[0041] like Figure 1 As shown, the amplifier circuit 12 has its output terminal connected to the first input terminal of the divider circuit 13, and it is used to amplify the output voltage of the Wheatstone bridge.

[0042] Optionally, the amplifier circuit 12 in this embodiment may include an operational amplifier, but this is only an example and is not intended to be limiting.

[0043] like Figure 1 As shown, the division circuit 13 has its second input terminal connected to the second power supply terminal of the Wheatstone bridge. It is used to calculate the magnetic field strength of the Wheatstone bridge based on the output voltage of the amplifier circuit and the ground circuit voltage.

[0044] Specifically, in this embodiment, the division circuit 13 performs a division operation on the output voltage of the amplifier circuit and the ground circuit voltage to obtain a voltage ratio that is independent of the variable T.

[0045] In some alternative implementations, such as Figure 1 As shown, the grounding circuit 11 includes: a grounding resistor R C .

[0046] Specifically, the grounding resistance R in this embodiment C This is a high-precision resistor that is insensitive to temperature; its resistance value does not change with temperature. Under the combined influence of temperature and magnetic field:

[0047]

[0048]

[0049]

[0050] In some alternative implementations, such as Figure 2 As shown, the division circuit 13 includes: a first logarithmic operation circuit 131, a second logarithmic operation circuit 132, a subtraction operation circuit 133, and an exponential operation circuit 134.

[0051] like Figure 2 As shown, the first logarithmic operation circuit 131 has its input terminal connected to the output terminal of the amplifier circuit 12, and its output terminal connected to the first input terminal of the subtraction operation circuit 133. It is used to take the logarithm of the output voltage of the amplifier circuit.

[0052] like Figure 2 As shown, the second logarithmic operation circuit 132 has its input terminal connected to the second power supply terminal of the Wheatstone bridge, and its output terminal connected to the second input terminal of the subtraction operation circuit 133. It is used to take the logarithm of the ground circuit voltage.

[0053] Optionally, such as Figure 3 As shown, both the first logarithmic operation circuit 131 and the second logarithmic operation circuit 132 include: a first resistor (R6, R8), a second resistor (R5, R7), a first operational amplifier (U1, U2), and a first switch (S1, S2). The first operational amplifier has its non-inverting input connected to the second power supply VDD2 through the first resistor, and its inverting input connected to the output of the amplifier circuit 12 or the second power supply of the Wheatstone bridge through the second resistor. The first terminal of the first switch is connected to the output of the first operational amplifier. The second terminal of the first switch is connected to the inverting input of the first operational amplifier, and its control terminal is connected to the third power supply VDD1.

[0054] like Figure 2 As shown, the subtraction circuit 133 has its output terminal connected to the input terminal of the exponentiation circuit 134, and its output terminal connected to the input terminal of the exponentiation circuit 134. It is used to subtract the two input voltages.

[0055] Optionally, such as Figure 3 As shown, the subtraction circuit 133 includes: a third resistor R9 and a fourth resistor R 11 Fifth resistor R 10 The sixth resistor R 12 The second operational amplifier U3 and the second switch S3 are described above. The non-inverting input of the second operational amplifier U3 is connected to the output of the first logarithmic operation circuit 131 via a third resistor R9, and its non-inverting input is also connected to a fourth resistor R... 11 It is connected to the second power supply VDD2, and its inverting input is connected to the fifth resistor R. 10 It is connected to the output of the second logarithmic operation circuit 132, and its output is connected to the sixth resistor R.12 Its output is connected to the first terminal of the second switch S3 and the control terminal of the second switch S3; the second terminal of the second switch S3 is connected to the input terminal of the exponential operation circuit 134.

[0056] like Figure 2 As shown, the exponential operation circuit 134 is used to perform exponential operations on the input voltage and outputs the ratio of the output voltage of the amplifier circuit to the ground circuit voltage.

[0057] Optionally, such as Figure 3 As shown, the exponentiation circuit 134 includes: a seventh resistor R 13 The eighth resistor R 14 and the third operational amplifier U4, wherein the non-inverting input of the third operational amplifier U4 is connected to the seventh resistor R. 13 It is connected to the second power supply VDD2, and its inverting input is connected to the output of the subtraction circuit 133. Its output is connected to the eighth resistor R. 14 When connected to its inverting input, its output terminal outputs the ratio of the output voltage of the amplifier circuit to the voltage of the ground circuit.

[0058] In some alternative implementations, the division circuit 13 includes a digital signal processing chip.

[0059] Specifically, in the improved Wheatstone bridge, the bridge output is connected to amplifier circuit 12, and then a divider circuit 13 is connected to complete the relevant signal processing. Based on the above calculations, we obtain:

[0060]

[0061] Digital signal processing chips calculate the magnetic field strength of the Wheatstone bridge using the following formula:

[0062]

[0063] In the formula, V0 is the ratio of the amplifier circuit output voltage to the ground circuit voltage, V1 is the output voltage of the Wheatstone bridge, V2 is the ground circuit voltage, and R... C Δ is the grounding resistance value, Gain is the amplifier gain, and Δ is the coefficient related to the magnetic field strength.

[0064] based on Figures 1-3 The Vo obtained from equation (13) is a function unrelated to temperature. Therefore, by adding a precision resistor, the TMR temperature drift can be compensated, the working mode of the power management module can be switched, and the accuracy of the current sensor can be improved. This embodiment has a wide range of applications and can be used for current sensors, wire and cable monitoring, etc.

[0065] This embodiment provides a current sensor, such as... Figure 1 As shown, it includes: a temperature compensation circuit for the Wheatstone bridge and the above embodiments and any optional implementation thereof. The Wheatstone bridge has four arms, each with a ninth resistor.

[0066] This invention designs a magnetic current sensor circuit and achieves temperature compensation for the magnetic current sensor by adding a temperature-insensitive high-precision resistor and a division operation circuit to the bridge circuit.

[0067] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A temperature compensation circuit, characterized by, The application is applied to a sensor based on a Wheatstone bridge, a first power supply terminal of the Wheatstone bridge is connected to a first power supply, and the circuit comprises a grounding circuit, an amplification circuit and a division circuit, wherein The grounding circuit is connected to a second power supply terminal of the Wheatstone bridge at a first end and grounded at a second end, and is used to make the output voltage of the Wheatstone bridge irrelevant to temperature; The amplification circuit is connected to a first output terminal and a second output terminal of the Wheatstone bridge at a first input end and a second input end respectively, and is connected to a first input end of the division circuit at an output end, and is used to amplify the output voltage of the Wheatstone bridge; The voltage between the output end of the amplification circuit and the second power supply terminal of the Wheatstone bridge is the temperature-compensated voltage of the Wheatstone bridge; The division circuit is connected to the second power supply terminal of the Wheatstone bridge at a second input end, and is used to calculate the voltage ratio of the output voltage of the amplification circuit and the voltage of the grounding circuit, and the voltage ratio is used to calculate the current; The grounding circuit comprises a grounding resistor; The division circuit comprises a first logarithm operation circuit, a second logarithm operation circuit, a subtraction operation circuit and an exponential operation circuit, wherein the first logarithm operation circuit is connected to the output end of the amplification circuit at an input end, is connected to a first input end of the subtraction operation circuit at an output end, and is used to take the logarithm of the output voltage of the amplification circuit; the second logarithm operation circuit is connected to the second power supply terminal of the Wheatstone bridge at an input end, is connected to a second input end of the subtraction operation circuit at an output end, and is used to take the logarithm of the voltage of the grounding circuit; the subtraction operation circuit is connected to the input end of the exponential operation circuit at an output end, is connected to the input end of the exponential operation circuit at an output end, and is used to subtract the two input voltages; and the exponential operation circuit is used to perform exponential operation on the input voltage, and outputs the ratio of the output voltage of the amplification circuit and the voltage of the grounding circuit.

2. The temperature compensation circuit of claim 1, wherein, The first logarithm operation circuit and the second logarithm operation circuit each comprise a first resistor, a second resistor, a first operational amplifier and a first switch, wherein The first operational amplifier is connected to the second power supply through the first resistor at a non-inverting input end, is connected to the output end of the amplification circuit or the second power supply terminal of the Wheatstone bridge through the second resistor at an inverting input end, and is connected to the first end of the first switch at an output end; The second end of the first switch is connected to the inverting input end of the first operational amplifier, and the control end is connected to a third power supply.

3. The temperature compensation circuit of claim 1, wherein, The subtraction operation circuit comprises a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a second operational amplifier and a second switch, wherein The non-inverting input end of the second operational amplifier is connected to the output end of the first logarithm operation circuit through the third resistor, is also connected to the second power supply through the fourth resistor, the inverting input end is connected to the output end of the second logarithm operation circuit through the fifth resistor, the output end is connected to the inverting input end through the sixth resistor, and the output end is also connected to the first end of the second switch and the control end of the second switch; A second switch, a second end of which is connected to an input end of the exponential operation circuit.

4. The temperature compensation circuit of claim 1, wherein, The exponential operation circuit comprises a seventh resistor, an eighth resistor and a third operational amplifier, wherein, The third operational amplifier has a non-inverting input end connected to the second power supply through the seventh resistor, an inverting input end connected to an output end of the subtraction operation circuit, and an output end connected to the inverting input end through the eighth resistor, and outputs a ratio of an output voltage of the amplification circuit to a voltage of the grounding circuit.

5. A temperature compensation circuit, characterized by, The circuit is applied to a sensor based on a Wheatstone bridge, a first power supply end of the Wheatstone bridge is connected to a first power supply, and the circuit comprises a grounding circuit, an amplification circuit and a division circuit, wherein, The grounding circuit has a first end connected to a second power supply end of the Wheatstone bridge and a second end grounded, and is used for making an output voltage of the Wheatstone bridge irrelevant to temperature; The amplification circuit has a first input end and a second input end connected to a first output end and a second output end of the Wheatstone bridge respectively, and an output end connected to a first input end of the division circuit, and is used for amplifying the output voltage of the Wheatstone bridge; A voltage between the output end of the amplification circuit and the second power supply end of the Wheatstone bridge is a temperature-compensated voltage of the Wheatstone bridge; The division circuit has a second input end connected to the second power supply end of the Wheatstone bridge, and is used for calculating a voltage ratio of an output voltage of the amplification circuit to a voltage of the grounding circuit, and the voltage ratio is used for calculating a current; The grounding circuit comprises a grounding resistor; The division circuit comprises a digital signal processing chip, and the digital signal processing chip calculates the magnetic field strength of the Wheatstone bridge according to the following calculation formula: In the formula, V0 is the ratio of the output voltage of the amplification circuit to the voltage of the grounding circuit, V1 is the output voltage of the Wheatstone bridge, V2 is the voltage of the grounding circuit, RC is the resistance value of the grounding resistor, Gain is the gain of the amplification circuit, and Δ is a coefficient related to the magnetic field strength.

6. A current sensor, characterized by The circuit comprises: The Wheatstone bridge and the temperature compensation circuit according to any one of claims 1-5.

7. The current sensor of claim 6, wherein, The Wheatstone bridge has four bridge arms, and each bridge arm is provided with a ninth resistor.

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