CN116897296A - Sensor output compensation circuit - Google Patents
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Abstract
The invention provides a sensor output compensation circuit capable of performing sensitivity temperature compensation of a sensor output with high accuracy in all temperature areas with high accuracy, and capable of achieving miniaturization and cheapness of a circuit. A sensor output compensation IC (1) applies bias voltages to power supply terminals (2 a, 2 b) of a TMR sensor (2) by a sensitivity temperature coarse adjustment compensation circuit (6 a) and a sensitivity temperature fine adjustment compensation circuit (6 b) which are provided as sensitivity temperature fine adjustment circuits, the bias voltages canceling variations occurring in sensitivity with respect to changes in ambient temperature. A sensitivity temperature coarse adjustment compensation circuit (6 a) receives the voltage conversion temperature from the temperature sensor circuit (11), and generates a bias voltage (Va) by inverting-amplifying the voltage conversion temperature at an amplification rate (R12/R11) corresponding to the rate of change of sensitivity with respect to ambient temperature, and supplies the bias voltage to one power supply terminal (2 a). The sensitivity temperature fine adjustment compensation circuit (6 b) generates a minute compensation bias voltage which further counteracts the minute fluctuation of the sensitivity remaining after the cancellation by the action of the sensitivity temperature fine adjustment compensation circuit (6 a), and supplies the generated minute compensation bias voltage as a bias voltage (Vb) to the other power supply terminal (2 b).
Description
Technical Field
The present invention relates to a sensor output compensation circuit for compensating the sensitivity of the output of a sensor in which sensor elements are bridged.
Background
Conventionally, as such a sensor output compensation circuit, for example, a sensor output compensation circuit in an amplifying circuit for a magnetoresistive element disclosed in patent document 1 is known.
The amplifying circuit for a magneto-resistive element includes a magneto-resistive element formed by bridging four ferromagnetic magneto-resistive element patterns, and differential amplifying circuits are connected to a pair of output terminals of the magneto-resistive element, thereby differentially amplifying an output voltage of the magneto-resistive element. The differential amplifier circuit is provided with an offset adjustment circuit for changing the midpoint potential of the amplified output voltage to a predetermined potential by a variable resistor, and a temperature compensation circuit for compensating for the fluctuation of the amplitude of the output voltage due to the temperature change is provided as a sensor output compensation circuit at a subsequent stage.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open No. 11-194160
Disclosure of Invention
Problems to be solved by the invention
However, in the temperature compensation circuit disclosed in the above-described conventional patent document 1, since a thermistor element is used for the temperature compensation resistor, only temperature compensation depending on the characteristics of the thermistor is performed. Therefore, the temperature range in which temperature compensation is possible is limited, and sensitivity compensation for temperature variation over a wider range is not possible, so there is a limit in sensitivity temperature compensation at the sensor output. Further, since there is also a variation in the characteristics of the thermistor element, the variation occurs as it is in the temperature compensation characteristics, and there is a problem in that the temperature compensation is highly accurate. Further, since a thermistor element is used for the temperature compensation circuit, it is difficult to make the temperature compensation circuit IC (high integration) and miniaturize or reduce the cost.
Technical scheme for solving problems
The present invention has been made to solve the above problems, and has:
a differential amplifier circuit that amplifies, as a sensor output, a differential voltage of each detection voltage appearing at a pair of detection signal output terminals of a sensor formed by bridging a sensor element whose resistance value varies according to a detected physical quantity;
a temperature sensor circuit for detecting an ambient temperature; and
a sensitivity temperature characteristic compensation circuit for applying a bias voltage to a pair of power supply terminals of the sensor based on the ambient temperature detected by the temperature sensor circuit, the bias voltage canceling out a variation occurring in sensitivity of the sensor output with respect to a variation in ambient temperature,
thus forming a sensor output compensation circuit.
According to this configuration, the fluctuation in the sensitivity of the sensor output with respect to the change in the ambient temperature is canceled out and compensated for by applying a bias voltage for canceling out the fluctuation to the pair of power supply terminals of the sensor by the sensitivity temperature characteristic compensation circuit. Therefore, unlike the conventional temperature compensation circuit disclosed in patent document 1, which can perform only temperature compensation depending on the thermistor characteristics, the temperature range in which temperature compensation is possible is not limited. In addition, the variation of the thermistor element in the temperature compensation characteristic is not generated as in the prior art. Therefore, it becomes possible to perform temperature compensation with high accuracy and sensitivity uniformly in all temperature regions. Further, since the sensor output compensation circuit can be configured without using a thermistor element for the temperature compensation circuit, the sensor output compensation circuit can be made IC, and the sensor output compensation circuit can be made compact and inexpensive.
Effects of the invention
Thus, according to the present invention, it is possible to provide a sensor output compensation circuit capable of performing temperature compensation with high sensitivity for a sensor output with high accuracy in the same manner in all temperature ranges, and capable of achieving miniaturization and cost reduction of the circuit.
Drawings
Fig. 1 is a circuit diagram showing a schematic configuration of an entire sensor output compensation circuit according to an embodiment of the present invention.
Fig. 2 is a circuit diagram for explaining the function of the linear compensation circuit in the sensor output compensation circuit shown in fig. 1.
In fig. 3, (a) is a graph showing a change in sensor output with respect to a magnetic field, and (b) is a graph showing a distortion with a sensor output that occurs non-linearly.
In fig. 4, (a) is a graph showing a control signal output from the linear compensation circuit in order to change the resistance value of the variable resistor R4, and (b) is a graph showing distortion of the sensor output after compensation by the linear compensation circuit.
Fig. 5 is a circuit diagram for explaining the function of the sensitivity temperature compensating circuit in the sensor output compensating circuit shown in fig. 1.
In fig. 6, (a) is a graph showing temperature characteristics regarding sensitivity of the sensor output, and (b) is a graph showing temperature characteristics regarding sensitivity of the sensor output after the sensitivity temperature compensation by the sensitivity temperature compensation circuit.
Fig. 7 is a graph showing a change in voltage conversion temperature output from the temperature sensor circuit with respect to ambient temperature.
Fig. 8 is a circuit diagram for explaining the function of the offset temperature compensating circuit in the sensor output compensating circuit shown in fig. 1.
In fig. 9, (a) is a graph showing the temperature characteristic of the fluctuation ratio of the offset voltage, and (b) is a graph showing the temperature characteristic of the fluctuation ratio of the offset voltage after being compensated by the offset temperature compensation circuit.
Detailed Description
Next, a mode for implementing the sensor output compensation circuit of the present invention will be described.
Fig. 1 is a circuit diagram showing a schematic configuration of an entire sensor output compensation circuit according to an embodiment of the present invention.
The sensor output compensation circuit is a circuit for inputting the output of a TMR (Tunnelinng Magneto-Resistive: tunnel magneto-resistance) sensor 2 and performing various compensation of the sensor output, and is formed into a sensor output compensation IC1 by being integrated into an IC. TMR sensor 2 is configured by bridging TMR elements whose resistance value varies in accordance with a magnetic field as a physical quantity to be detected, and operates by applying a predetermined voltage to a pair of power supply terminals 2a, 2 b. The magnetic field detected by TMR sensor 2 appears as a voltage difference between the pair of detection signal output terminals 2c, 2d and is supplied as a sensor output to signal input terminals 1a, 1b of sensor output compensation IC1. Such TMR sensor 2 is used, for example, for monitoring the current supplied to the motor of the hybrid vehicle.
The various types of compensation performed by the sensor output compensation IC1 include linear compensation, sensitivity temperature characteristic compensation (TCS (Temperature Coefficient Sensitivity): hereinafter referred to as "sensitivity temperature characteristic compensation"), offset compensation, and offset temperature characteristic compensation (TCO (Temperature Characteristic of Offset): hereinafter referred to as "offset temperature characteristic compensation") of the sensor output. Further, the offset compensation for each individual of TMR sensor 2 is included.
The linearity compensation is compensation for removing nonlinear components in the sensor output and ensuring the linearity of the sensor output. The offset compensation is compensation for canceling offset voltages that occur at the pair of detection signal output terminals 2c, 2d when the TMR sensor 2 does not detect a magnetic field. The offset temperature compensation is compensation for eliminating temperature variation of the offset voltage. Further, the sensitivity compensation is compensation for canceling the deviation caused by each body of the TMR sensor 2 with respect to the sensitivity of the TMR sensor 2. The sensitivity of TMR sensor 2 is a value obtained by dividing the rated magnetic field by the output span voltage obtained by subtracting the offset voltage from the rated output voltage of sensor output compensation IC1, meaning the change in output voltage per unit magnetic field. The sensitivity temperature compensation is compensation for eliminating temperature variation of sensitivity temperature characteristics indicating the maximum variation of output span voltage at compensation temperature.
The sensor output compensation IC1 includes a differential amplifier circuit 3 including an instrumentation amplifier, and a compensation amplifier circuit 4 for compensating the output of the differential amplifier circuit 3. The differential amplifier circuit 3 includes operational amplifiers 31 and 32 for amplifying the respective detection voltages appearing at the pair of detection signal output terminals 2c and 2d of the TMR sensor 2, and an operational amplifier 33 for differentially amplifying the amplified detection voltages. The differential voltage of each detection voltage appearing at the pair of detection signal output terminals 2c, 2d is treated as a substantial sensor output. When the resistors connected to the operational amplifiers 31 to 33 and the resistance values thereof are R0, R1, R2, R3, R1', R2', and R3' as shown in the drawing, the differential amplifier circuit 3 outputs an output a obtained by amplifying the sensor output with an amplification factor α represented by the following expression (1).
α＝(R3/R2)×{1+(2×R1)/R0}…(1)
Wherein r1=r1 ', r2=r2 ', r3=r3 ', and R0 is a varistor.
The sensitivity of the sensor output is adjusted by making the variable resistor R0 variable, so that the deviation caused by the individual of the TMR sensor 2 can be compensated for. A variable voltage source VREF1 is connected to the noninverting input terminal of the operational amplifier 33 via a resistor R3'. The offset voltage of the sensor output is adjusted by making the output voltage of this variable voltage source VREF1 variable, and is adjusted so that the output voltage VOUT appearing at the output terminal OUT of the sensor output compensation IC1 becomes zero when the magnetic field is not detected by the TMR sensor 2.
The compensation amplifier circuit 4 includes an operational amplifier 41 connected to a variable resistor R4 and a variable resistor R5, and outputs an output B obtained by inverting-amplifying an output a of the differential amplifier circuit 3 as an output voltage VOUT to an output terminal OUT of the sensor output compensation IC 1. As a result, the sensor output is amplified at an amplification factor β shown in the following expression (2).
β＝α×(R5/R4)
＝(R3/R2)×{1+(2×R1)/R0}×(R5/R4)…(2)
The amplification factor (R5/R4) of the compensation amplification circuit 4 is changed by changing the resistance value of the connected variable resistor R4 or R5. In the present embodiment, the connection between a plurality of resistors, not shown, is switched by a plurality of switches, not shown, to change the combined resistance value of the plurality of resistors, and thus the resistance values of the variable resistors R4 and R5 are variable, respectively.
The sensor output compensation IC1 of the present embodiment includes a linear compensation circuit 5 that compensates for the linearity of the sensor output, a sensitivity temperature compensation circuit that compensates for the sensitivity temperature characteristic of the sensor output, and an offset temperature compensation circuit 7 that compensates for the temperature characteristic of the offset voltage of the sensor output. In the present embodiment, the sensitivity warm-up compensation circuit includes a sensitivity warm-up rough adjustment compensation circuit 6a and a sensitivity warm-up fine adjustment compensation circuit 6b. The differential amplifier circuit 3, the compensation amplifier circuit 4, the linear compensation circuit 5, the sensitivity temperature coarse adjustment compensation circuit 6a, the sensitivity temperature fine adjustment compensation circuit 6b, and the offset temperature compensation circuit 7 constitute a compensation module 8 of the sensor output compensation IC 1.
The sensor output compensation IC1 includes a regulator circuit (VREG) 9, a reference voltage circuit (VREF) 10, and a temperature sensor circuit 11. The regulator circuit 9 generates a reference voltage from the voltage input to the power supply terminal VDD. The reference voltage circuit 10 generates reference voltages of respective values used in the sensitivity warm-up coarse adjustment compensation circuit 6a, the sensitivity warm-up fine adjustment compensation circuit 6b, the offset warm-up compensation circuit 7, and the like, based on the reference voltage generated by the regulator circuit 9. The temperature sensor circuit 11 detects the ambient temperature as a voltage by a diode, and outputs the detected voltage conversion temperature to the sensitivity temperature coarse adjustment compensation circuit 6a and the offset temperature compensation circuit 7. In addition, since TMR sensor 2 and sensor output compensation IC1 are disposed close to each other, the ambient temperature detected by temperature sensor circuit 11 is detected as the ambient temperature of TMR sensor 2.
The sensor output compensation IC1 includes an EEPROM12 that allows a user to rewrite the stored content. With this EEPROM12, setting DATA is written from the DATA terminal DATA by a user. Based on the setting data, setting adjustment of the compensation operation performed by the various compensation circuits in the compensation module 8 is performed, and setting adjustment of temperature detection in the temperature sensor circuit 11 is performed.
In the present embodiment, the linear compensation by the linear compensation circuit 5 is performed by changing the amplification factor (R5/R4) of the compensation amplification circuit 4 as described later, and the amplification factor (R5/R4) is changed by switching the connection state between the plurality of resistors constituting the variable resistor R4 by a plurality of switches according to the setting data written to the EEPROM 12. The sensitivity temperature compensation by the sensitivity temperature coarse adjustment compensation circuit 6a and the sensitivity temperature fine adjustment compensation circuit 6b is performed by switching the resistance values of the variable resistors R11 to R14, which will be described later, and the reference voltages VREF3 and VREF4 (see fig. 5) according to the setting data written in the EEPROM 12. The offset temperature compensation by the offset temperature compensation circuit 7 is also performed by switching the connection states of the switches 75 and 76 (see fig. 8) described later according to the setting data written in the EEPROM 12. The temperature sensor circuit 11 is adjusted to output 1[V as a voltage conversion temperature when the ambient temperature is 25 ℃ based on the setting data written to the EEPROM 12.
Fig. 2 is a circuit diagram for explaining the function of the linear compensation circuit 5 in the sensor output compensation IC1 shown in fig. 1. In the same drawing, the same or corresponding parts as those in fig. 1 are denoted by the same reference numerals, and the description thereof will be omitted.
The linearity-compensation circuit 5 comprises a plurality of comparators 51, 52, 53, …, 5n. The output voltage of the differential amplifier circuit 3 is commonly input to one input terminal of each of the comparators 51, 52, 53, …, 5n, and predetermined reference voltages vref_l1, vref_l2, vref_l3, …, vref_ln output from the reference voltage circuit 10 are input to the other input terminal. These reference voltages vref_l1, vref_l2, vref_l3, …, and vref_ln correspond to the respective sensor outputs corresponding to the magnetic fields causing the given respective distortions having the nonlinear appearance at the sensor outputs, and are set in advance according to the setting data written to EEPROM 12.
The linear compensation circuit 5 changes the resistance value of the variable resistor R4 by switching a plurality of switches constituting the variable resistor R4 based on the comparison result between the plurality of reference voltages and the output voltage of the differential amplifier circuit 3, thereby changing the amplification factor (R5/R4) of the compensation amplifier circuit 4 to an amplification factor that cancels the distortion.
Here, the case will be described in which the resistance value of the variable resistor R4 is changed by switching the plurality of switches constituting the variable resistor R4, and thus the amplification factor (R5/R4) of the compensation amplifier circuit 4 is changed, but the configuration may be adopted in which the resistance value of the variable resistor R5 is changed by switching the plurality of switches constituting the variable resistor R5, and thus the amplification factor (R5/R4) of the compensation amplifier circuit 4 is changed.
Fig. 3 (a) is a graph showing an example of the relationship between the magnetic field supplied to TMR sensor 2 and the sensor output that appears as a differential voltage between detection signal output terminals 2c, 2d when each magnetic field is supplied to TMR sensor 2. The horizontal axis of the same graph is the magnetic field [ mT ] provided to TMR sensor 2, and the vertical axis is the sensor output [ mV ]. The characteristic line y represents a change in the sensor output with respect to each magnetic field when the ambient temperature of the sensor output compensation IC1 is 25 ℃. The characteristic line y can be expressed as a polynomial of the following expression (3) using the magnetic field x as a variable.
y＝-6.469e -0.7 x 3 -1.512e -0.6 x 2 +2.175e -0.2 x+4.306e -0.3 …(3)
In the illustration of the same graph, at first glance, the characteristic line y appears to be a straight line, but includes nonlinear components shown in items 1 and 2 on the right side of item (3), and the graph shown in fig. 3 (b) is obtained when the relationship between the magnetic field and the sensor output is expressed by removing the linear component on the right side of item 3. The horizontal axis of the same graph represents the magnetic field [ mT ] supplied to TMR sensor 2, but the vertical axis represents the sensor output [ mV ] from which the linear component is removed. Furthermore, the characteristic line y' represents a distortion with a sensor output that occurs non-linearly. This distortion affects the magnetic field detection accuracy of TMR sensor 2, and is therefore compensated for by linear compensation circuit 5.
According to the same graph, since distortion exists in magnetic field regions of about +8[ mT ] or more and about-8 [ mT ] or less, when sensor output with respect to a predetermined magnetic field is obtained in these magnetic field regions, the amplification factor of the compensation amplification circuit 4 is made variable by the linear compensation circuit 5, and the distortion is cancelled.
Fig. 4 (a) is a graph showing an example of the control signal v supplied from the linear compensation circuit 5 to each switch of the variable resistor R4. The horizontal axis of the same graph represents the magnetic field [ mT ] supplied to TMR sensor 2, and the vertical axis represents the voltage [ V ] of control signal V. The characteristic line a indicates a magnetic field change of the input voltage input to the input terminals 1a and 1b of the sensor output compensation IC1, and the characteristic line b indicates a magnetic field change of the output voltage VOUT output to the output terminal OUT of the sensor output compensation IC 1. The characteristic line c, d, e, f shows control signals v1, v2, v3, and v4 for correcting distortion of the sensor output of about +8[ mt ] or more in the positive magnetic field shown in fig. 3 (b), and the characteristic line g, h, i, j shows control signals v5, v6, v7, and v8 for correcting distortion of the sensor output of about-8 [ mt ] or less in the negative magnetic field. The control signals v1 to v8 change between a high level of +5[V and a low level of 0 v, and for example, when the control signals change to the low level, the switches sw1 to sw8 are closed and controlled.
In the same graph, regarding the distortion of the sensor output in the magnetic field region of about +8[ mt ] or more, the switch sw1 is closed-controlled by lowering the control signal v1 indicated as the characteristic line c in the magnetic field of about +7[ mt ], and the resistance value of the variable resistor R4 is changed, whereby the amplification factor of the compensation amplification circuit 4 is changed to the amplification factor that cancels the distortion in the magnetic field at this time. Further, the switch sw2 is closed-controlled by lowering the control signal v2 indicated as the characteristic line d in the magnetic field of about +10[ mt ], the switch sw3 is closed-controlled by lowering the control signal v3 indicated as the characteristic line e in the magnetic field of about +13[ mt ], and the switch sw4 is closed-controlled by lowering the control signal v4 indicated as the characteristic line f in the magnetic field of about +15[ mt ], whereby the resistance value of the variable resistor R4 is variable, and the amplification factor of the compensation amplifier circuit 4 is changed to an amplification factor that cancels distortion in each magnetic field.
Similarly, with respect to distortion of the sensor output in the magnetic field region of about-8 [ mt ] or less, the switches sw5 to sw8 are closed-controlled by the control signals v5 to v8 indicated as characteristic lines g to j, and the resistance value of the variable resistor R4 is variable, whereby the amplification factor of the compensation amplification circuit 4 is changed to an amplification factor that cancels the distortion in each magnetic field.
Fig. 4 (b) is a graph showing distortion of the sensor output after compensating for the nonlinearity of the sensor output by such resistance value control of the variable resistor R4 performed by the linear compensation circuit 5. The horizontal axis of the same graph represents the magnetic field [ mT ] supplied to TMR sensor 2, and the vertical axis represents the proportion [% ] of distortion components contained in output voltage VOUT output to output terminal OUT of sensor output compensation IC 1. The characteristic line k represents a fluctuation characteristic of a distortion component included in the output voltage VOUT with respect to a change in the magnetic field.
The distortion of the sensor output in the magnetic field region of about +8[ mt ] or more decreases to the right with respect to the increase in the magnetic field as shown in fig. 3 (b), but it is understood from the characteristic line k that the amplification factor of the compensation amplification circuit 4 increases at each timing when the control signals v1, v2, v3, v4 are sequentially lowered in level in each magnetic field of about +7[ mt ], about +10[ mt ], about +13[ mt ], and about +15[ mt ], whereby the proportion of the distortion component increases to the right, and the effect of canceling the decrease in the distortion shown in fig. 3 (b) is exerted.
The distortion of the sensor output in the magnetic field region of about-8 mt or less increases to the left with respect to the decrease in the magnetic field as shown in fig. 3 (b), but it is similarly understood from the characteristic line k that the amplification factor of the compensation amplification circuit 4 decreases at each timing when the respective control signals v5 to v8 are sequentially lowered in level according to the decrease in the magnetic field, whereby the proportion of the distortion component decreases to the left, and the effect of canceling the increase in the distortion shown in fig. 3 (b) is exerted.
Further, the proportion of the distortion component increases in the positive magnetic field region to rise rightward, and then temporarily decreases in a rightward direction due to the decrease in the original distortion shown in fig. 3 (b). In addition, in the magnetic field region on the negative side, after decreasing downward to the left, the original distortion increases to temporarily increase upward to the left due to the increase in distortion shown in fig. 3 (b). Therefore, the characteristic line k fluctuates up and down in a zigzag shape as shown in fig. 4 (b), but the fluctuation range of the distortion component is suppressed to ±0.1[% ] or less, and the linearity of the sensor output can be ensured.
As described above, according to the sensor output compensation IC1 according to the present embodiment, the linear compensation circuit 5 controls the plurality of switches to switch the connection between the plurality of resistors connected to the compensation amplification circuit 4 as the variable resistor R4, and the amplification factor of the compensation amplification circuit 4 is variable by changing the combined resistance value of the plurality of resistors. If the output voltage of the differential amplifier circuit 3 is compared with a plurality of preset reference voltages vref_l1, vref_l2, vref_l3, …, and vref_ln to become voltages corresponding to the outputs of the sensors corresponding to the magnetic fields causing the predetermined distortions, the switch is switched. By switching the switch, the amplification factor of the compensation amplification circuit 4 becomes an amplification factor that cancels out each given distortion from the output of the differential amplification circuit 3 according to the output voltage of the differential amplification circuit 3, and the linearity of the sensor output can be ensured.
That is, according to the sensor output compensation IC1 of the present embodiment, the amplification factor of the compensation amplification circuit 4 that compensates the output of the differential amplification circuit 3 can be changed to the amplification factor that cancels the distortion by the linear compensation circuit 5, and thus the distortion that appears non-linearly in the sensor output with respect to the change in the magnetic field can be compensated. Therefore, compared with a conventional nonlinear compensation circuit (see japanese patent application laid-open No. 2003-248017) that performs linear compensation by feeding back the sensor output, the response speed of the circuit is faster, and nonlinear compensation of the sensor output can be performed at a high speed. Further, since the addition circuit is not required for the sensor output compensation circuit as in the conventional art, the circuit scale of the sensor output compensation IC1 can be suppressed.
Fig. 5 is a circuit diagram for explaining the functions of the sensitivity warm coarse adjustment compensation circuit 6a and the sensitivity warm fine adjustment compensation circuit 6b in the sensor output compensation IC1 shown in fig. 1. In the same drawing, the same or corresponding parts as those in fig. 1 are denoted by the same reference numerals, and the description thereof will be omitted. The sensitivity temperature coarse adjustment compensation circuit 6a and the sensitivity temperature fine adjustment compensation circuit 6b constitute a sensitivity temperature compensation circuit in which a bias voltage that counteracts variations in sensitivity of the sensor output due to changes in ambient temperature is applied to the pair of power supply terminals 2a, 2b of the TMR sensor 2 based on the ambient temperature detected by the temperature sensor circuit 11. Since the sensor sensitivity can be made variable by adjusting the bias voltage with respect to the TMR sensor 2, the temperature characteristic of the sensitivity can be compensated by making the bias voltage variable with respect to the ambient temperature.
The sensitivity temperature coarse adjustment compensation circuit 6a includes an inverting amplifier circuit including an operational amplifier 61, a coarse adjustment variable resistor R11, and a coarse adjustment variable resistor R12. The reference voltage VREF3 generated by the reference voltage circuit 10 is input to the non-inverting input terminal of the operational amplifier 61. The sensitivity temperature coarse adjustment compensation circuit 6a receives the voltage conversion temperature output from the temperature sensor circuit 11 according to the ambient temperature. Then, the voltage conversion temperature is amplified in an inverted manner at an amplification factor (R12/R11) corresponding to the rate of change of the sensitivity of the sensor output with respect to the ambient temperature, and a bias voltage Va is generated and supplied to one power supply terminal 2a of the pair of power supply terminals 2a, 2 b.
Fig. 6 (a) is a graph showing an example of temperature characteristics regarding sensitivity of the sensor output. The horizontal axis of the same graph represents the ambient temperature [ °c ] of TMR sensor 2, and the vertical axis represents the rate of change of sensitivity [% ] at each ambient temperature when a magnetic field of 20[ mt ] is supplied to TMR sensor 2. The characteristic line m represents a characteristic of a change rate of sensitivity with respect to an ambient temperature, and the ambient temperature can be expressed as the following expression (4) as a variable x.
m＝-0.0952x+2.4[％]…(4)
As shown by a characteristic line m of the graph, the rate of change in sensitivity exhibits a temperature characteristic having a slope (-0.0952 x) of 1 time, which decreases linearly with an increase in temperature. Therefore, in order to prevent sensitivity from being affected by a change in ambient temperature, in the present embodiment, bias voltage Va having a slope (+ 0.0952 x) of 1 times opposite to characteristic line m is supplied as a temperature compensation voltage to a pair of power supply terminals 2a, 2b of TMR sensor 2, and sensitivity is compensated so that characteristic line m has a flat characteristic with respect to a change in ambient temperature.
For this reason, in the present embodiment, the voltage conversion temperature outputted from the temperature sensor circuit 11 and having the same slope as the characteristic line m is inputted to the sensitivity coarse adjustment compensation circuit 6a, and the polarity of the slope of the voltage conversion temperature is inverted in the inverting amplification circuit of the sensitivity coarse adjustment compensation circuit 6 a. The voltage conversion temperature is amplified at an amplification factor (R12/R11) of the inverting amplification circuit having a slope equal to the slope of the characteristic line m, that is, at an amplification factor corresponding to the rate of change of the sensitivity of the sensor output with respect to the ambient temperature, so that a temperature compensation voltage is generated as the bias voltage Va.
Fig. 7 is a graph showing a change in the voltage conversion temperature output from the temperature sensor circuit 11 with respect to the ambient temperature. The horizontal axis of the same graph represents the ambient temperature [ °c ] of the sensor output compensation IC1, and the vertical axis represents the output voltage V of the temperature sensor circuit 11 at each ambient temperature. The characteristic line o shows the temperature characteristic of the voltage conversion temperature as the output voltage of the temperature sensor circuit 11. As shown in the graph, the characteristic line o of the voltage conversion temperature and the characteristic line m of the fluctuation ratio of the sensitivity each have a negative polarity slope that decreases linearly with an increase in temperature.
The inverting amplifier circuit of the sensitivity temperature coarse adjustment compensation circuit 6a changes the amplification factor (R12/R11) by changing the resistance value of the connected coarse adjustment variable resistor R11 or coarse adjustment variable resistor R12. The respective resistance values of the rough-tuning variable resistor R11 and the rough-tuning variable resistor R12 are variable by changing the combined resistance value of the plurality of rough-tuning resistors by switching the connection between the plurality of rough-tuning resistors by the plurality of switches. By switching the switch, the amplification factor (R12/R11) of the inverting amplification circuit is set to an amplification factor that cancels out the fluctuation of sensitivity due to the ambient temperature, so that the magnitude of the slope of the characteristic line o of the voltage conversion temperature matches the magnitude of the slope of the characteristic line m of the fluctuation of sensitivity. Further, the polarity of the slope of the characteristic line o of the voltage conversion temperature is inverted from the polarity of the slope of the characteristic line m of the fluctuation ratio of the sensitivity by inverting the voltage conversion temperature by the inverting amplification circuit.
Therefore, one power supply terminal 2a of the pair of power supply terminals 2a, 2b of TMR sensor 2 is supplied with bias voltage Va in which the voltage conversion temperature outputted from temperature sensor circuit 11 is inversely amplified at an amplification factor (R12/R11) corresponding to the rate of change of the sensitivity with respect to the ambient temperature as the sensitivity temperature compensation voltage. Therefore, by supplying the bias voltage Va, which changes in polarity opposite to the sensitivity at the same rate of change with respect to the ambient temperature, to one power supply terminal 2a of the sensor, it is possible to cancel out the fluctuation component of the sensitivity included in the sensor output appearing at the pair of detection signal output terminals 2c, 2d of the TMR sensor 2. Further, the temperature sensor circuit 11 can cancel out the fluctuation component of the sensitivity without providing a dedicated circuit for compensating the sensitivity temperature characteristic.
Fig. 6 (b) is a graph showing the ambient temperature characteristics of the fluctuation ratio of the sensitivity subjected to temperature compensation in this way. Like the graph of fig. 6 (a), the horizontal axis of the graph of fig. 6 (b) represents the ambient temperature [ deg.c ], and the vertical axis represents the rate of change of sensitivity at each ambient temperature [% ] when a magnetic field of 20[ mt ] is supplied to TMR sensor 2. The characteristic line n represents the change in the rate of change of sensitivity with respect to the ambient temperature. As shown in the graph, the fluctuation ratio of the sensitivity of the sensor output compensation IC1 after compensation converges to a small fluctuation range of ±0.03[% ] or less.
However, in the present embodiment, in order to perform temperature compensation of sensitivity with higher accuracy, the sensitivity temperature fine adjustment compensation circuit 6b constituting the sensitivity temperature fine adjustment compensation circuit generates a minute compensation bias voltage that further cancels out the minute fluctuation of the sensitivity of the sensor output remaining after cancellation by the action of the sensitivity temperature fine adjustment compensation circuit 6a as shown in fig. 6 (b). The generated minute compensation bias voltage is supplied as bias voltage Vb to the other power supply terminal 2b of the pair of power supply terminals 2 a.
The sensitivity temperature fine adjustment compensation circuit 6b includes: an inverting amplifier circuit including an operational amplifier 62, a micro-adjustment variable resistor R13, and a micro-adjustment variable resistor R14; and a sensitivity compensation voltage circuit 63. The reference voltage VREF4 generated by the reference voltage circuit 10 is input to the non-inverting input terminal of the operational amplifier 62. The sensitivity compensation voltage circuit 63 generates a sensitivity compensation voltage which is a base of a minute compensation bias voltage for canceling out minute variations in sensitivity remaining in the sensor output. The inverting amplification circuit including the operational amplifier 62 inverts the sensitivity compensation voltage generated by the sensitivity compensation voltage circuit 63 by an amplification factor (R14/R13) to generate a minute compensation bias voltage, and outputs the minute compensation bias voltage to the other power supply terminal 2b.
The amplification factor (R14/R13) is changed by changing the resistance value of the micro-variable resistor R13 or the micro-variable resistor R14 connected to the operational amplifier 62. The resistance values of the micro-adjustment variable resistor R13 and the micro-adjustment variable resistor R14 are each variable by switching the connection between the plurality of micro-adjustment resistors by a plurality of switches, thereby changing the combined resistance value of the plurality of micro-adjustment resistors. By switching the switch, the magnitude of the minute compensation bias voltage generated by the sensitivity warm-up adjustment compensation circuit 6b can be adjusted, and the minute fluctuation of the sensor output remaining after the offset by the action of the sensitivity warm-up adjustment compensation circuit 6a can be appropriately offset.
As described above, according to the sensor output compensation IC1 of the present embodiment, as described above, the fluctuation in the sensitivity of the sensor output with respect to the change in the ambient temperature is offset and compensated by applying the bias voltage Va that offsets the fluctuation to the pair of power supply terminals 2a, 2b of the sensor by the sensitivity temperature compensation circuit. Therefore, unlike the conventional temperature compensation circuit disclosed in patent document 1, which can perform only temperature compensation depending on the thermistor characteristics, the temperature range in which temperature compensation is possible is not limited. In addition, the variation of the thermistor element in the temperature compensation characteristic is not generated as in the prior art. Therefore, it becomes possible to perform temperature compensation with high accuracy and sensitivity uniformly in all temperature regions. Further, since the sensor output compensation circuit can be configured without using a thermistor element for the temperature compensation circuit, the sensor output compensation circuit can be made IC, and the sensor output compensation circuit can be made compact and inexpensive.
Further, according to the sensor output compensation IC1 of the present embodiment, the minute fluctuation of the sensor output remaining after being offset by the action of the sensitivity temperature fine adjustment compensation circuit 6a is offset by generating the bias voltage Vb for further offset of the minute fluctuation as the minute compensation bias voltage by the sensitivity temperature fine adjustment compensation circuit 6b and supplying the bias voltage Vb to the other one of the pair of power supply terminals 2a, 2b. Therefore, it becomes possible to perform temperature compensation of sensitivity with higher accuracy in the same manner in all temperature regions.
Further, by compensating the bias voltage of TMR sensor 2 at two positions of power supply terminals 2a, 2b, the sensitivity temperature compensating circuit can be provided with a coarse tuning function and a fine tuning function, and thus sensitivity temperature coarse tuning compensating circuit 6a and sensitivity temperature fine tuning compensating circuit 6b can be optimally designed, respectively. Accordingly, the circuit constants of the elements constituting the respective circuits can be optimized, the adjustment resolution of the respective circuits can be improved, and the increase in the area of the circuits can be suppressed. Further, according to the sensor output compensation IC1 according to the present embodiment, since the bias voltage of the TMR sensor 2 is directly controlled, compensation of the sensor sensitivity can be performed without impairing the detection accuracy.
Fig. 8 is a circuit diagram for explaining the function of the offset temperature compensating circuit 7 in the sensor output compensating IC1 shown in fig. 1. In the same drawing, the same or corresponding parts as those in fig. 1 are denoted by the same reference numerals, and the description thereof will be omitted.
The offset temperature compensating circuit 7 refers to the ambient temperature detected by the temperature sensor circuit 11, and inputs the reference voltage VREF2, which is obtained by canceling the variation of the offset voltage output from the sensor due to the variation of the ambient temperature, to the reference voltage terminal of the compensating amplifying circuit 4.
The temperature variation of the offset voltage output by the sensor is shown in the graph shown in fig. 9 (a). The horizontal axis of the graph indicates the ambient temperature [ °c ] of the sensor output compensation IC1, and the vertical axis indicates the rate of change [% ] of the offset voltage at each ambient temperature based on the offset voltage at the ambient temperature of 25 ℃. Further, each characteristic line shows a temperature characteristic with respect to each offset voltage of the plurality of TMR sensors 2. As shown in the graph, the temperature characteristic of each offset voltage has a slope of 1 time and varies linearly. The offset temperature compensating circuit 7 inputs the reference voltage VREF2, which cancels the fluctuation, to a reference voltage terminal, which is a non-inverting input terminal of the operational amplifier 41 in the compensating amplifying circuit 4.
In the present embodiment, the offset temperature compensating circuit 7 includes a 1 st inverting amplifier circuit 72 including an operational amplifier 71, a 2 nd inverting amplifier circuit 74 including an operational amplifier 73, a 1 st switch 75, and a 2 nd switch 76.
The 1 st inverting amplifier circuit 72 is configured by connecting a resistor R7 and a variable resistor R8 to the operational amplifier 71, and the reference voltage VREF21 is supplied to the non-inverting input terminal of the operational amplifier 71. The 1 st inverting amplifier circuit 72 performs inverting amplification of the ambient temperature detected as the voltage by the temperature sensor circuit 11 at an amplification ratio (R8/R7) corresponding to the variation ratio of the offset voltage. The change rate of the offset voltage corresponds to the slope of each characteristic line in the graph shown in fig. 9 (a), and the amplification factor (R8/R7) is matched with the change rate of the offset voltage by adjusting the resistance value of the variable resistor R8.
The 2 nd inverting amplifier circuit 74 is configured by connecting a resistor R9 and a variable resistor R10 to the operational amplifier 73, and the reference voltage VREF22 is supplied to the non-inverting input terminal of the operational amplifier 73. The 2 nd inverting amplifier circuit 74 inverts the polarity of the output of the 1 st inverting amplifier circuit 72 by an amplification factor (R10/R9). The amplification factor (R10/R9) is basically set to 1 by adjusting the resistance value of the variable resistor R10. When the offset voltage changes with respect to the ambient temperature and increases with an increase in the ambient temperature, the 2 nd switch 76 is closed and controlled so that the output of the 2 nd inverting amplifier circuit 74 is input to the reference voltage terminal of the operational amplifier 41 as the reference voltage VREF 2.
Therefore, in the case where the temperature characteristic of the offset voltage of the sensor output compensation IC1 is represented by, for example, a characteristic line p of a straight line rising to the right, which increases with an increase in ambient temperature, in the graph shown in fig. 9 (a), the voltage outputted from the temperature sensor circuit 11, which decreases with an increase in ambient temperature, is represented by a characteristic line of a straight line falling to the right, and is converted into a voltage having a characteristic rising to the right, the slope of which is the same as the magnitude of the rate of change of the offset voltage of the characteristic line p and the polarity of which is inverted, in the offset temperature compensating circuit 7, by the 1 st inverting amplifier circuit 72. Then, the 2 nd switch 76 is closed-controlled, and thus the voltage is converted by the 2 nd inverting amplifier circuit 74 into the reference voltage VREF2 having a characteristic of falling rightward with the polarity of the slope inverted. Therefore, the compensation amplifier circuit 4 amplifies the output voltage including the offset voltage indicated by the characteristic line p of the straight line rising rightward, which is output from the differential amplifier circuit 3, with reference to the reference voltage VREF2, and thus the variation due to the temperature characteristic of the offset voltage is canceled.
Fig. 9 (b) is a graph showing temperature characteristics with respect to each offset voltage of the four TMR sensors 2 after being compensated by the offset temperature compensating circuit 7. The horizontal axis and the vertical axis of the same graph are the same as those in fig. 9 (a). The graph shown in fig. 9 (b) shows a characteristic line p before compensation, and the temperature characteristic of the offset voltage of TMR sensor 2 having the characteristic line p is compensated to a temperature characteristic having a substantially flat slope by the offset compensation described above and the slope of the arrow shown by the dot line is inclined.
When the offset voltage changes with respect to the ambient temperature and changes with an increase in the ambient temperature, the 1 st switch 75 is closed and controlled so that the output of the 1 st inverting amplifier circuit 72 is input to the reference voltage terminal of the operational amplifier 41 as the reference voltage VREF2. Therefore, in the case where the temperature characteristic of the offset voltage of TMR sensor 2 is represented by, for example, a characteristic line q of a straight line falling rightward, which is reduced with an increase in ambient temperature with respect to a fluctuation in ambient temperature, in the graph shown in fig. 9 (a), since 1 st switch 75 is closed-controlled, the voltage represented by the characteristic line of the straight line falling rightward, which is outputted from temperature sensor circuit 11 with an increase in ambient temperature, is converted into reference voltage VREF2 having a characteristic rising rightward, which has the same magnitude of slope as the magnitude of the fluctuation rate of the offset voltage of characteristic line q and whose polarity of the slope is inverted, in offset temperature compensating circuit 7. Accordingly, the compensation amplifier circuit 4 amplifies the output voltage including the offset voltage indicated by the characteristic line q of the straight line falling rightward, which is output from the differential amplifier circuit 3, with reference to the reference voltage VREF2, whereby the variation due to the temperature characteristic of the offset voltage is canceled out as in the graph shown in fig. 9 (b).
As described above, according to the sensor output compensation IC1 of the present embodiment, when the offset voltage changes with respect to the ambient temperature and changes with an increase in the ambient temperature, the output of the 2 nd inverting amplifier circuit 74 is input to the reference voltage terminal of the compensation amplifier circuit 4 through the 2 nd switch 76. Accordingly, the ambient temperature detected as a voltage by the temperature sensor circuit 11 is inversely amplified by the 1 st inverting amplifying circuit 72 at an amplification ratio (R8/R7) corresponding to the fluctuation ratio of the offset voltage, and the polarity is inverted by the 2 nd inverting amplifying circuit 74, so that an ambient temperature inversion signal whose fluctuation ratio of the offset voltage is reduced with an increase in the ambient temperature is input as the reference voltage VREF2 from the 2 nd inverting amplifying circuit 74 to the reference voltage terminal of the operational amplifier 41. Therefore, the compensation amplifier circuit 4 amplifies the output of the differential amplifier circuit 3 with the ambient temperature inversion signal as a reference, and thereby the sensor output whose temperature fluctuation of the offset voltage is canceled can be obtained from the compensation amplifier circuit 4.
When the offset voltage varies with respect to the ambient temperature and decreases with an increase in the ambient temperature, the 1 st switch 75 causes the output of the 1 st inverting amplifier circuit 72 to be input to the reference voltage terminal of the operational amplifier 41. Accordingly, the 1 st inverting amplifier circuit 72 performs inverting amplification at an amplification factor (R8/R7) corresponding to the variation factor of the offset voltage, and an ambient temperature inverting signal whose variation factor of the offset voltage increases with an increase in ambient temperature is input as the reference voltage VREF2 from the 1 st inverting amplifier circuit 72 to the reference voltage terminal of the operational amplifier 41. Therefore, the compensation amplification circuit 4 amplifies the output of the differential amplification circuit 3 with the ambient temperature inversion signal as a reference, and thus the sensor output whose offset voltage variation occurring with respect to the change in ambient temperature is offset can be obtained from the compensation amplification circuit 4.
That is, according to the sensor output compensation IC1 of the present embodiment, the compensation amplifier circuit 4 that compensates the output of the differential amplifier circuit 3 amplifies the output of the differential amplifier circuit 3 with reference to the reference voltage VREF2 input to the reference voltage terminal of the operational amplifier 41 from the offset temperature compensating circuit 7, whereby the fluctuation of the offset voltage of the sensor output occurring with respect to the change in the ambient temperature can be canceled. Therefore, the offset voltage can be compensated with high accuracy and simplicity by one compensation operation. Thus, unlike the conventional offset adjustment circuit disclosed in patent document 1, which adjusts the offset of the sensor output by adjusting only the midpoint potential of the differential amplifier circuit by the variable resistor, the temperature compensation of the offset voltage of the sensor output can be performed easily and accurately.
In the sensor output compensation IC1 according to the present embodiment, the circuits constituting the sensor output compensation circuit are mounted on the same IC. Therefore, variations due to wiring between circuits constituting the sensor output compensation circuit and differences in mounting components constituting the circuits are reduced. Therefore, the sensor output compensation IC1 can perform each compensation of the sensor output with high accuracy. Further, it becomes possible to mount the compensation function entirely on the IC. Further, by monitoring the sensor output of the compensated TMR sensor 2, it becomes possible to perform each compensation with high accuracy for each TMR sensor 2 with a relatively simple circuit configuration. In addition, in the compensation adjustment of each compensation circuit, by selecting the setting data written to EEPROM12, it becomes possible to easily and selectively select the compensation value.
Further, by mounting the temperature sensor circuit 11 on the same IC as each of the other circuits constituting the sensor output compensation circuit, the relative positions of the temperature sensor circuit 11 and each of the other circuits become constant. Therefore, an error between the ambient temperature detected by the temperature sensor circuit 11 and the ambient temperature of the other circuits is reduced. Further, even when the temperature sensor circuit 11 is provided separately from the ICs of the other circuits, an error is not generated between the ambient temperature detected by the temperature sensor circuit 11 and the ambient temperature used in the ICs due to parasitic resistance components or the like of the wiring connection portion connecting the temperature sensor circuit 11 and the ICs by wire bonding. As a result, according to the sensor output compensation IC1 of the present embodiment, temperature compensation of the sensor sensitivity and offset voltage can be performed with high accuracy.
Description of the reference numerals
1: a sensor output compensation IC;
2: TMR sensor;
2a, 2b: a pair of power supply terminals of TMR sensor 2;
2c, 2d: a pair of detection signal output terminals of TMR sensor 2;
3: a differential amplifying circuit;
4: an amplifying circuit for compensation;
5: a linear compensation circuit;
51. 52, 53, …, 5n: a comparator;
6a: a sensitivity temperature coarse adjustment compensation circuit;
6b: a sensitivity temperature fine adjustment compensation circuit;
7: an offset temperature compensation circuit;
72: a 1 st inverting amplifier circuit;
74: a 2 nd inverting amplifier circuit;
75: a 1 st switch;
76: and a 2 nd switch.
Claims (6)
1. A sensor output compensation circuit, comprising:
a differential amplifier circuit that amplifies, as a sensor output, a differential voltage of each detection voltage appearing at a pair of detection signal output terminals of a sensor formed by bridging a sensor element whose resistance value varies according to a detected physical quantity;
a temperature sensor circuit for detecting an ambient temperature; and
and a sensitivity temperature characteristic compensation circuit that applies a bias voltage to a pair of power supply terminals of the sensor, based on the ambient temperature detected by the temperature sensor circuit, the bias voltage canceling out a variation in sensitivity of the sensor output with respect to a change in the ambient temperature.
2. The sensor output compensation circuit of claim 1 wherein,
the sensitivity temperature characteristic compensation circuit includes: and a sensitivity temperature coarse adjustment compensation circuit which receives a voltage conversion temperature outputted as a voltage according to the ambient temperature from the temperature sensor circuit, and generates the bias voltage by inverting-amplifying the voltage conversion temperature at an amplification rate corresponding to a rate of change of the sensitivity of the sensor output with respect to the ambient temperature, and supplies the bias voltage to one of the pair of power supply terminals.
3. The sensor output compensation circuit of claim 2 wherein,
the sensitivity temperature coarse adjustment compensation circuit changes the amplification factor by changing the resistance value of a connected variable resistor for coarse adjustment,
the resistance value of the coarse tuning variable resistor is variable by changing the combined resistance value of the plurality of coarse tuning resistors by switching the connection between the plurality of coarse tuning resistors using a plurality of switches.
4. A sensor output compensation circuit according to claim 2 or 3, wherein,
the sensitivity temperature characteristic compensation circuit includes: and a sensitivity temperature fine adjustment compensation circuit for generating a minute compensation bias voltage to be further cancelled by the minute fluctuation of the sensitivity of the sensor output remaining after the cancellation by the action of the sensitivity temperature fine adjustment compensation circuit, and supplying the generated minute compensation bias voltage to the other one of the pair of power supply terminals.
5. The sensor output compensation circuit of claim 4 wherein,
the sensitivity temperature fine adjustment compensation circuit comprises: an amplifying circuit for adjusting the magnitude of the minute compensation bias voltage,
the amplifying circuit changes the amplification factor by changing the resistance value of the connected trimming variable resistor,
The resistance value of the tuning variable resistor is variable by changing the combined resistance value of the plurality of tuning resistors by switching the connection between the plurality of tuning resistors using a plurality of switches.
6. The sensor output compensation circuit of any one of claims 1 to 5 wherein,
the sensor element is a TMR element.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2021-061404 | 2021-03-31 | ||
| JP2021-063118 | 2021-04-01 | ||
| JP2021063118 | 2021-04-01 | ||
| PCT/JP2022/010726 WO2022209720A1 (en) | 2021-03-31 | 2022-03-10 | Sensor output compensation circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116897296A true CN116897296A (en) | 2023-10-17 |
Family
ID=88312495
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202280015905.9A Pending CN116897296A (en) | 2021-03-31 | 2022-03-10 | Sensor output compensation circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116897296A (en) |
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2022
- 2022-03-10 CN CN202280015905.9A patent/CN116897296A/en active Pending
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