Signal processing circuit and sensor unit

Abstract

To provide a signal processing circuit that can reduce electric power consumption.SOLUTION: The signal processing circuit processes detection signals, which are output from a sensor and comprise a DC component and an AC component, and it comprises a low-pass filter that extracts the DC component and a high-pass filter that extracts the AC component from the detection signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a signal processing circuit and a sensor unit. [Background technology]

[0002] In order to improve the detection accuracy of a sensor, various signal processing may be performed on the detection signal output from the sensor. For example, Patent Document 1 discloses a signal processing circuit that can improve the detection accuracy by performing amplification processing or the like on the output signal from a magnetic sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-180727 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the detection signal output from the sensor and input to the signal processing circuit, and the signal processing performed on the detection signal, the power consumption in the signal processing may increase. For example, in a magnetic sensor, when the sensitivity of the sensor is low, the detection signal is amplified in order to detect the detected magnetism with high accuracy. In the signal processing such as the amplification processing, the power consumption may increase depending on the signal to be processed.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a signal processing circuit capable of reducing power consumption. [Means for solving the problem]

[0006] A signal processing circuit according to one aspect of the present disclosure provides a signal processing circuit that processes a detection signal output from a sensor and including a DC component and an AC component, the signal processing circuit including a low-pass filter that extracts the DC component from the detection signal, and a high-pass filter that extracts the AC component from the detection signal.

[0007] The signal processing circuit according to an aspect of the present disclosure may include a signal addition section that adds together the DC component extracted by the low-pass filter and the AC component extracted by the high-pass filter.

[0008] A signal processing circuit according to an aspect of the present disclosure may include a signal correction unit that corrects the sum signal, which is an output signal from the signal addition unit, by applying a correction value calculated based on a DC component to the sum signal.

[0009] A signal processing circuit according to an embodiment of the present disclosure may include a first signal processing unit that performs a first signal processing on a DC component, and a second signal processing unit that performs a second signal processing on an AC component.

[0010] In the signal processing circuit according to an aspect of the present disclosure, the sensor may be a magnetic sensor.

[0011] A sensor unit according to one aspect of the present disclosure includes a sensor and a signal processing circuit formed integrally with the sensor. Effect of the Invention

[0012] According to the present disclosure, it is possible to provide a signal processing circuit capable of reducing power consumption. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram showing a schematic configuration of a sensor unit 100 according to the present embodiment. [Diagram 2] FIG. 1 is a schematic perspective view of a sensor unit 100 according to the present embodiment. [Diagram 3]1 is a circuit diagram showing a schematic configuration of a magnetic detection unit 10 according to the present embodiment. [Figure 4] FIG. 2 is a perspective view showing a schematic configuration of a magnetoresistive effect element 14 according to the present embodiment. [Diagram 5] 1 is a circuit diagram showing a schematic configuration of a magnetic detection unit 10 according to the present embodiment. [Figure 6] 1 is a functional block diagram showing a configuration of a sensor unit 100 according to the present embodiment. [Figure 7] 5A and 5B are diagrams illustrating examples of signal waveforms according to the present embodiment. [Figure 8A] FIG. 4 is a diagram showing frequency characteristics of a signal according to the embodiment. [Figure 8B] FIG. 4 is a diagram showing frequency characteristics of a signal according to the embodiment. [Figure 8C] FIG. 4 is a diagram showing frequency characteristics of a signal according to the embodiment. [Figure 9] 1 is a functional block diagram showing a configuration of a sensor unit 100 according to the present embodiment. [Figure 10] FIG. 4 is a diagram showing frequency characteristics of a signal according to the embodiment. [Figure 11] 1 is a functional block diagram showing a configuration of a sensor unit 100 according to the present embodiment. [Figure 12] 3 is a diagram showing a schematic example of the characteristics of the magnetic detection unit 10 according to the present embodiment. FIG. [Figure 13] 3 is a diagram showing a schematic example of the characteristics of the magnetic detection unit 10 according to the present embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") will be described with reference to the accompanying drawings. Note that in the drawings attached to this specification, the scale and aspect ratios may be appropriately changed and exaggerated from those of the actual objects for the convenience of illustration and ease of understanding.

[0015] In the following, a signal processing circuit that processes a signal detected by a magnetic sensor will be described as an example of a signal processing circuit according to an embodiment of the present disclosure. However, the signal processing circuit according to an embodiment of the present disclosure may be used for signal processing other than signals detected by a magnetic sensor. The signal processing circuit according to the present embodiment may be used for signal processing of signals detected by sensors other than a magnetic sensor, for example.

[0016] Hereinafter, each drawing may show an X-axis, a Y-axis, and a Z-axis. The X-axis, the Y-axis, and the Z-axis form a right-handed three-dimensional Cartesian coordinate system. Hereinafter, the direction of the X-axis arrow may be called the +X direction, and the direction opposite to the arrow may be called the -X direction. The same applies to the other axes. The +Z direction and the -Z direction may be called the "upper side" or "upper" and the "lower side" or "lower", respectively. The Z-axis direction may be called the "stacking direction". The planes perpendicular to the X-axis, Y-axis, or Z-axis may be called the YZ plane, ZX plane, or XY plane. However, these directions are used for convenience to explain the relative positional relationship. Therefore, these directions do not define the absolute positional relationship.

[0017] In the following, terms and / or values ​​that mean shapes and / or geometric conditions do not need to be bound by strict meanings, and may be interpreted as including a range within which similar functions may be expected. For example, "parallel" and / or "orthogonal" correspond to the above terms. Also, "length value" and / or "angle value" correspond to the above numerical values.

[0018] Furthermore, when a certain configuration is expressed as being "above," "below," "upper," "lower," "above," or "below" another configuration, this may include a configuration in which the certain configuration is in direct contact with the other configuration, and a configuration in which another configuration is included between the certain configuration and the other configuration. In other words, a configuration in which another configuration is included between the certain configuration and the other configuration may be expressed as a configuration indirectly in contact with the other configuration. Furthermore, the expressions "above," "upper side," or "above" can be exchanged for the expressions "below," "lower side," or "below." In other words, the up-down direction may be reversed. The same applies to the left and right.

[0019] In the following description, when the same or similar reference numerals are used for the same parts and / or parts having similar functions, repeated description may be omitted. Also, the dimensional ratios in the drawings may differ from the actual ratios. Also, some of the configurations of the embodiments may be omitted from the drawings.

[0020] Fig. 1 is a block diagram showing a schematic configuration of a sensor unit 100 according to this embodiment. As shown in Fig. 1, the sensor unit 100 according to this embodiment includes a magnetic detection unit 10 (also referred to as a "magnetic sensor" in this embodiment) and a signal processing circuit 20. The magnetic detection unit 10 outputs a magnetic signal S when a magnetic field is applied. The signal processing circuit 20 processes the magnetic signal S input from the magnetic detection unit 10. The signal processing circuit 20 performs signal processing on the magnetic signal S and outputs a signal S'.

[0021] In this embodiment, the magnetic detection unit 10 may be, for example, a TMR (Tunnel Magnetoresistance Effect) element. The magnetic detection unit 10 is not limited to a TMR element, and may be a GMR (Giant Magnetoresistance Effect) element, an AMR (Anisotropic Magnetoresistance Effect) element, a Hall element, or another type of magnetic detection element.

[0022] Fig. 2 is a schematic perspective view of the sensor unit 100. As shown in Fig. 2, the magnetic detection unit 10 is formed on the signal processing circuit 20 (+Z direction). A terminal group 62 is provided on an upper surface 10s of the magnetic detection unit 10, and a terminal group 64 is provided on an upper surface 20s of the signal processing circuit 20. The terminal group 62 of the magnetic detection unit 10 and the terminal group 64 of the signal processing circuit 20 are connected to each other by, for example, a plurality of bonding wires 50. The magnetic detection unit 10 may be configured to detect, for example, an external magnetic field.

[0023] Fig. 3 is a circuit diagram showing a schematic configuration of the magnetic detection unit 10. As shown in Fig. 3, the magnetic detection unit 10 has, for example, one or more element units 12. In the example shown in Fig. 3, the magnetic detection unit 10 has a first element unit 12a, a second element unit 12b, a third element unit 12c, and a fourth element unit 12d. The multiple element units 12 of the magnetic detection unit 10 may form a Wheatstone bridge circuit.

[0024] 4 is a perspective view showing a schematic configuration of a magnetoresistance effect element 14 (hereinafter also referred to as an "MR element") included in the element section 12. The element section 12 includes, for example, a plurality of magnetoresistance effect elements 14 connected in series, and each of the plurality of magnetoresistance effect elements 14 may be, for example, a spin-valve type magnetoresistance effect element. As shown in FIG. 4, in this embodiment, the magnetoresistance effect element 14 may be, for example, a substantially oval shape. In this embodiment, the magnetoresistance effect element 14 may be connected to the element section 12 via a plurality of connection layers 16.

[0025] 4, for example, a first connection layer 16a of the multiple connection layers 16 contacts the bottom surfaces of two MR elements 14 adjacent to each other in the circuit configuration, and electrically connects these MR elements 14. In addition, a second connection layer 16b contacts the top surfaces of adjacent MR elements 14, and electrically connects these MR elements 14.

[0026] 4, the MR element 14 has an antiferromagnetic layer 142, a magnetization fixed layer 144, a gap layer 146, and a free layer 148. As shown in FIG. 4, the antiferromagnetic layer 142 is electrically connected to the first connecting layer 16a, and the free layer 148 is electrically connected to the second connecting layer 16b. The antiferromagnetic layer 142 includes an antiferromagnetic material. The antiferromagnetic layer 142 may generate exchange coupling with the magnetization fixed layer 144 to fix the magnetization direction of the magnetization fixed layer 144.

[0027] The spin-valve type MR element 14 is, for example, a TMR element or a GMR element. When the MR element is a TMR element, the gap layer 146 is, for example, a tunnel barrier layer. When the MR element is a GMR element, the gap layer 146 is, for example, a nonmagnetic conductive layer. The arrangement of the antiferromagnetic layer 142, the magnetization fixed layer 144, the gap layer 146, and the free layer 148 of the MR element 14 is not limited to the example shown in FIG. 4. For example, the antiferromagnetic layer 142, the magnetization fixed layer 144, the gap layer 146, and the free layer 148 may be stacked in the Z direction in the reverse order of the example shown in FIG. 4.

[0028] In the spin-valve magnetoresistance effect element 14, the resistance value changes depending on the angle that the magnetization direction of the free layer 148 makes with respect to the magnetization direction of the magnetization fixed layer 144, and when this angle is 0°, the resistance value is at its minimum and when it is 180°, the resistance value is at its maximum.

[0029] For example, as described above with reference to FIG. 3, the magnetic detection unit 10 may include a first element unit 12a, a second element unit 12b, a third element unit 12c, and a fourth element unit 12d, which are a plurality of element units 12, and the first element unit 12a, the second element unit 12b, the third element unit 12c, and the fourth element unit 12d may form a full-bridge Wheatstone bridge circuit. The Wheatstone bridge circuit shown in FIG. 3 includes a power supply port V, a ground port G, and output ports E1 and E2. A voltage of a predetermined magnitude is applied to the power supply port V, and the ground port G is connected to the ground. One end of the first element unit 12a may be connected to the power supply port V, and the other end of the first element unit 12a may be connected to the output port E1. One end of the second element unit 12b may be connected to the output port E1, and the other end of the second element unit 12b may be connected to the ground port G. Similarly, one end of the third element portion 12c may be connected to the ground port G, the other end of the third element portion 12c may be connected to the output port E2, one end of the fourth element portion 12d may be connected to the output port E2, and the other end of the fourth element portion 12d may be connected to the power supply port V.

[0030] In this embodiment, for example, the magnetization direction of the magnetization fixed layer 144 of the magnetoresistance effect element 14 is fixed in a direction parallel to the X-axis. As shown by the arrows in Fig. 3, for example, the magnetization direction of the magnetization fixed layer 144 of the magnetoresistance effect element 14 of the first element unit 12a and the third element unit 12c is "+X direction", and the magnetization direction of the magnetization fixed layer 144 of the magnetoresistance effect element 14 of the second element unit 12b and the fourth element unit 12d is "-X direction". The magnetization direction of the magnetization fixed layer 144 of the magnetoresistance effect element 14 of the first to fourth element units 12a to 12d is parallel to the short diameter direction or short side direction of the magnetoresistance effect element 14 of a substantially oval or substantially rectangular shape in a plan view, and therefore the sensitivity axis of the magnetoresistance effect element 14 of the first to fourth element units 12a to 12d is parallel to the X-axis.

[0031] On the other hand, in this embodiment, the magnetization direction of the free layer 148 of the magnetoresistance effect element 14 in the initial state, in which the magnetic field to be detected is not applied to the magnetic detection unit 10, may be parallel to the Y axis. In the exemplary embodiment shown in FIG. 3, the magnetization easy axis direction of the free layer 148 of the magnetoresistance effect element 14 of the first element unit 12a and the fourth element unit 12d is the "-Y direction", and the magnetization easy axis direction of the free layer 148 of the magnetoresistance effect element 14 of the second element unit 12b and the third element unit 12c is the "+Y direction". In this embodiment, for example, the magnetization easy axis direction of the free layer 148 of the magnetoresistance effect element 14 of the first to fourth element units 12a to 12d is parallel to the major axis direction of the magnetoresistance effect element 14 having a substantially oval shape in a plan view.

[0032] In this embodiment, in the magnetic detection unit 10 shown in FIG. 3, the potential difference between output ports E1 and E2 changes as a magnetic field is applied to each of the magnetoresistance effect elements 14 of the first to fourth element units 12a to 12d, and a differential detector (not shown) outputs a signal S corresponding to the potential difference between the output ports E1 and E2 to the signal processing unit 20 as a signal representing the magnetic field strength.

[0033] The magnetic detection unit 10 may form a half-bridge Wheatstone bridge circuit as shown in Fig. 5. In this case, as shown in Fig. 5, the magnetic detection unit 10 has two element units (a first element unit 12a and a second element unit 12b). As shown in Fig. 5, one end of the first element unit 12a may be connected to a power supply port V, the other end of the first element unit 12a may be connected to an output port E1, one end of the second element unit 12b may be connected to the output port E1, and the other end of the second element unit 12b may be connected to a ground port G.

[0034] Hereinafter, the signal processing unit 20 of the sensor unit 100, which is an example of the signal processing circuit according to the present embodiment, will be described. FIG. 6 is a functional block diagram showing the configuration of the sensor unit 100 according to the present embodiment. The signal processing unit 20 according to the present embodiment is a signal processing circuit that processes the detection signal S output from the magnetic detection unit 10, which is a sensor. As described below, in this embodiment, the detection signal S output from the magnetic detection unit 10 includes a direct current component and an alternating current component. In addition, the signal processing unit 20 includes a low-pass filter 22a that extracts the direct current component from the detection signal S, and a high-pass filter 22b that extracts the alternating current component from the detection signal S. Therefore, in this embodiment, the separation circuit 22 of the signal processing circuit 20 includes the low-pass filter 22a and the high-pass filter 22b. The signal processing circuit 20 may further include an amplifier circuit 24. The amplifier circuit 24 will be described later.

[0035] Note that FIG. 6 illustrates an example in which X-component, Y-component, and Z-component signals (the above-mentioned Sx, Sy, and Sz, respectively) are input from the magnetic detection unit 10 to the signal processing circuit 20, and in FIG. 6, the magnetic detection unit 10 includes the above-mentioned first magnetic detection unit 10a, second magnetic detection unit 10b, and third magnetic detection unit 10c.

[0036] In addition, in this embodiment, the DC component of the detection signal may include a component of a frequency other than the component with a frequency of zero. For example, in addition to the component with a frequency of zero, the DC component of the detection signal may include a component of a predetermined frequency range with a frequency of 1 or more. For example, the DC component of the detection signal in this embodiment may include a component with a frequency of zero Hertz (Hz) or more and 100 Hertz or less. In this case, the AC component of the detection signal in this embodiment may include a component with a frequency of more than 100 Hertz. In addition, the DC component of the detection signal in this embodiment may include a component with a frequency of zero Hertz (Hz) or more and 1000 Hertz or less, and in this case, the AC component of the detection signal in this embodiment may include a component with a frequency of more than 1000. In the following description of this specification, the DC component of the detection signal includes a component with a frequency from zero Hertz (Hz) to a predetermined frequency of 100 Hertz or more, and the AC component of the detection signal includes a component with a frequency band larger than the frequency band of the DC component.

[0037] Through the study of the present inventors, it has been found that the power consumption consumed in signal processing may increase depending on the detection signal output from the sensor and input to the signal processing circuit, and the signal processing performed on the detection signal. For example, when a magnetic sensor is used as a sensor and a detection signal output from the magnetic sensor is processed, if an alternating current magnetic field (AC magnetic field) is superimposed on a magnetic field signal of a direct current magnetic field (DC magnetic field), and both the alternating current component (AC component) and the direct current component (DC component) of the magnetic field signal are input to the magnetic sensor unit, it has been found that the power consumption required for signal processing may increase if the magnetic field signal with the superimposed AC component and DC component is processed as it is.

[0038] Fig. 7 shows an example of the signal waveform of the magnetic field signal processed by the magnetic sensor unit in this case. As shown in Fig. 7, for example, a magnetic field signal in which an AC component with a period T1 is superimposed on a DC component is input. For example, when amplification processing is performed on a magnetic field signal in which an AC component and a DC component are superimposed, the power consumption may be three times or more as much as when amplification processing is performed on only the DC component.

[0039] For example, in an information processing device or information device that uses a sensor to transmit information, it is possible to transmit more information by superimposing not only a DC component but also an AC component. However, expanding the frequency range of the signal may cause an increase in power consumption. For example, it is preferable not to increase power consumption, especially in small portable information devices.

[0040] In recent years, in portable information devices and the like, in order to increase the amount of information, the output signals from various sensors provided in the information devices to the signal processing circuit may be increased by superimposing an AC component on a DC component, for example. In addition, as the performance and functions of information devices become more advanced, more sensors may be installed, and the amount of information from more sensors will also increase. However, particularly in portable information devices, it is preferable to reduce power consumption from the viewpoint of battery consumption, and it is also preferable to reduce power consumption in circuits that process output signals from sensors. For example, portable terminals are equipped with magnetic sensors such as compasses, and there are cases in which it is particularly desirable to reduce power consumption in the compass.

[0041] For example, when amplifying a detection signal input to a signal processing circuit, a telescopic type amplifier circuit that can reduce power consumption relatively compared to a folded cascode type amplifier circuit may be used as the amplifier circuit. However, a telescopic type amplifier circuit cannot increase the input voltage due to the limitation of the number of transistors that can be used, so it is difficult to increase the detection signal input from the sensor. Therefore, it is considered that a signal processing circuit that can increase the output signal from the sensor while suppressing an increase in power consumption is desired, particularly in portable information devices.

[0042] Therefore, the inventors performed a separation process on the magnetic field signal (an example of the detection signal S) using a separation circuit 22, i.e., extracted the DC component using a low-pass filter 22a (LP: (Low pass)) and extracted the AC component using a high-pass filter 22b (HP (High pass)), thereby separating the detected magnetic field signal, thereby making it possible to reduce power consumption in signal processing of the detection signal S, and thus came up with the signal processing circuit 20 according to an embodiment of the present disclosure.

[0043] 6, the signal processing circuit 20 of the sensor unit 100 according to this embodiment includes a low-pass filter 22a and a high-pass filter 22b. In the signal processing unit 20, from the detection signal S including a DC component and an AC component output from the magnetic detection unit 10, the low-pass filter 22a extracts the DC component, and the high-pass filter 22b extracts the AC component.

[0044] Fig. 8A shows a schematic diagram of the frequency characteristic of an input signal in which an AC component is superimposed on a DC component. Fig. 8B shows the frequency characteristic of the DC component after separation, and Fig. 8C shows the frequency characteristic of the AC component after separation. As shown in Figs. 8A, 8B, and 8C, for a signal (Fig. 8A) in which a relatively large amplitude is confirmed up to a relatively high frequency range (e.g., several hundred to several thousand hertz), in the signal processing circuit 20 according to this embodiment, the low-pass filter 22a extracts the DC component (Fig. 8B) (in this embodiment, for example, a band of 100 hertz or less), and the high-pass filter 22b extracts the AC component (Fig. 8C) (in this embodiment, for example, a band of more than 100 hertz).

[0045] The extracted DC component and AC component are each subjected to signal processing in the following process, for example. As shown in Fig. 6, the signal processing circuit 20 includes, for example, a first amplifier circuit 24a (also referred to as a "first signal processing section" in this embodiment) and a second amplifier circuit 24b (also referred to as a "second signal processing section" in this embodiment), and the separated DC component may be amplified by the first amplifier circuit 24a (first signal processing in this embodiment), and the separated AC component may be amplified by the second amplifier circuit 24b (second signal processing in this embodiment). The power consumption in the signal processing such as amplification performed at this time can be reduced compared to the case where the input signal in which the AC component is superimposed on the DC component is subjected to signal processing such as amplification without separation.

[0046] In the signal processing circuit 20 according to the present embodiment, an addition process may be performed on the DC component and the AC component after separation of the detection signal S. As shown in Fig. 9, the signal processing circuit 20 according to the present embodiment may include an addition circuit (signal addition unit 26), and the DC component extracted by the low-pass filter 22a and the AC component extracted by the high-pass filter 22b may be added together. In the subsequent signal processing of the added signal, power consumption can be reduced compared to the case where the input signal in which the AC component is superimposed on the DC component is processed without being separated.

[0047] Fig. 10 shows the frequency characteristics of a signal obtained by adding a DC component (Fig. 8B) and an AC component (Fig. 8C) by the adder circuit 26. As shown in Fig. 10, the added signal shows frequency characteristics similar to those of the signal before separation shown in Fig. 8A over the frequency range of the DC component and the AC component.

[0048] 9 illustrates an example in which the DC component amplified by the first amplifier circuit 24a (i.e., the first output signal output by the first signal processing unit after the first signal processing) and the AC component amplified by the second amplifier circuit 24b (i.e., the second output signal output by the second signal processing unit after the second signal processing) are added by the adder circuit 26, but in the signal processing circuit 20 according to this embodiment, the DC component and the AC component before signal processing such as amplification may be added together. That is, the DC component output by the low-pass filter 22a and the AC component output by the high-pass filter 22b may be added together.

[0049] In the signal processing circuit 20 according to this embodiment, a correction process may be performed on the added signal (also referred to as an "added signal" in this embodiment). As shown in Fig. 11, the signal processing circuit 20 according to this embodiment may include a correction circuit (signal correction unit 28) that corrects the signal added by the signal addition unit 26, and may perform the correction process described below.

[0050] FIG. 12 shows ideal characteristics of the magnetic detection unit 10. FIG. 12 shows, for example, ideal characteristics of the magnetic detection unit 10 with respect to the X-direction component of the external magnetic field. In FIG. 12, the horizontal axis indicates the intensity B of a component in a certain direction of the external magnetic field (for example, the X-direction component), and the vertical axis indicates the X-direction component (Sx) of the detection signal output by the magnetic detection unit 10. In the example shown in FIG. 12, the intensity B is expressed as a positive value when the direction of the X-direction component of the external magnetic field is the +X direction, and the intensity B is expressed as a negative value when the direction of the X-direction component of the external magnetic field is the -X direction. In addition, in the example shown in FIG. 12, the value of the detection signal S is 0 when the intensity B is 0, a positive value when the intensity B is a positive value, a negative value when the intensity B is a negative value, and increases as the intensity B increases. That is, as shown in FIG. 12, ideally, the detection signal S generated by the magnetic detection unit 10 is proportional to the intensity B of the external magnetic field.

[0051] However, depending on the environment in which the sensor unit 100 is used, the magnetic detection section 10 may exhibit characteristics different from those exemplified in Fig. 12. For example, an external magnetic field in a direction other than the X-axis direction may affect the detection signal by the magnetic detection section 10. In this case, distortion occurs in the characteristics with respect to the magnetic field strength, and the magnitude of the gradient of the magnetic detection characteristics may change depending on the strength B of the external magnetic field.

[0052] Fig. 13 shows the characteristics of the magnetic detection unit in a non-ideal case. As shown in Fig. 13, in a non-ideal case, for example, when the strength B of the external magnetic field increases or decreases, the slope of the magnetic detection characteristics with respect to the strength B of the external magnetic field may become small. Therefore, the detection signal S may not be proportional to the magnetic field strength B.

[0053] In this embodiment, for example, a signal correction process may be performed to correct the signal to have characteristics as shown in Fig. 12. For example, the correction process may be performed so that the magnetic field intensity B and the detection signal S are proportional to each other.

[0054] In this embodiment, the correction value applied in the correction process may be calculated using the DC component of the detection signal, as described below. Note that the calculation of the correction value at this time may be performed, for example, in a test field, which is an ideal environment, using the DC component of the detection signal.

[0055] As described above, the characteristics of the detection signal of the magnetic detection unit 10 may be distorted with respect to the magnetic field strength, and the slope of the change in the detection signal with respect to the magnetic field strength may change depending on the magnetic field strength, as shown in Fig. 13. If the detection signal contains only a DC component, for example, in an ideal environment, the detection signal with respect to the change in the external magnetic field strength is proportional to the change in the external magnetic field strength, and is considered to show a linear change as shown in Fig. 12. Therefore, in this embodiment, the distortion of the slope of the change in the detection signal with respect to the magnetic field strength can be corrected by using a correction value calculated using the DC component of the detection signal.

[0056] Furthermore, for example, the scale of the amplitude of the AC component of the detected magnetic field signal may be relatively smaller than the scale of the amplitude of the DC component (for example, the scale of the amplitude of the AC component may be 1 / 10 or less than 1 / 10 of the DC component). In this case, by performing the correction process of the AC component of the detection signal using a correction value calculated based on the DC component, it becomes possible to relatively easily bring the characteristics indicated by the relationship between the magnetic field strength B and the detection signal S closer to the ideal state than when a correction value calculated based on the AC component is applied.

[0057] Also, for example, an offset may occur in the magnetic signal detected by the magnetic detection unit 10 due to factors other than the magnetic field to be detected. For example, when the magnetic detection unit 10 detects a magnetic field generated by a magnetic generator (not shown), an offset may occur due to factors other than the magnetic generator. In this case, a correction value for correcting the offset may be calculated, and the signal correction circuit 28 may perform a correction process.

[0058] In the above-described embodiment, the sensor unit 100 according to this embodiment may be formed by forming the magnetic detection section 10 and the signal processing circuit 20 as separate bodies and sealing them with resin or the like, or the magnetic detection section 10 and the signal processing circuit 20 may be integrally (monolithically) formed. The sensor unit 100 formed by either method has the above-described operational effects.

[0059] In the above embodiment, the sensor unit 100 having one magnetic detection unit 10 has been described as an example, but the present embodiment can also be applied to a case where a plurality of magnetic detection units 10 are provided, and in that case, the same effects as those described above are achieved. For example, the present embodiment can be applied to a case where the magnetic detection unit 10 includes a plurality of magnetic detection units having the same magnetic sensing direction, a case where each magnetic detection unit has one magnetic detection unit having a different magnetic sensing direction, or a case where a plurality of magnetic detection units each having a different magnetic sensing direction are provided. In this way, when a plurality of magnetic detection units are provided and the signal processing circuits connected to each magnetic detection unit are increased, the power consumption may increase with the increase in the signal processing circuits. As described above, the present embodiment can reduce power consumption, so the present embodiment can be effectively applied to a sensor unit 100 that includes a plurality of magnetic detection units and may increase power consumption.

[0060] The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The elements of the embodiments, as well as their arrangements, materials, conditions, shapes, sizes, etc., are not limited to those shown as examples and can be changed as appropriate. In addition, configurations shown in different embodiments can be partially substituted or combined with each other.

[0061] For example, the sensor unit 100 in this embodiment can be applied to a magnetic sensor unit, and when used as a magnetic sensor unit, it may be used to detect a position change in the XY plane or a position change in the Z direction from a change in a magnetic field in the Z direction. Applications that include this sensor include, for example, strain gauges, angle sensors, position sensors, compasses, current sensors, switches, and the like, as well as actuators used in robot joint mechanisms, open / close detection mechanisms for notebook computers, joysticks, brushless motors, magnetic encoders, and other electronic devices. [Explanation of symbols]

[0062] 10 Magnetic detection unit 12 Element section 14 Magnetoresistance effect element 16 Connection Layer 20 Signal Processing Circuit 22 Separation circuit 22a Low-pass filter 22b High Pass Filter 24 Amplification circuit 24a First amplifier circuit (first signal processing section) 24b Second amplifier circuit (second signal processing section) 26 Addition circuit (signal addition section) 28 Correction circuit (signal correction section) 100 Sensor Unit 142 Antiferromagnetic layer 144 Magnetization fixed layer 146 Gap Layer 148 Free layer

Claims

1. A signal processing circuit that processes a detection signal output from a sensor and including a DC component and an AC component, a low-pass filter that extracts the DC component from the detection signal; A high-pass filter that extracts the AC component from the detection signal. Signal processing circuit.

2. 2. The signal processing circuit according to claim 1, further comprising a signal adding section that adds together the DC component extracted by the low-pass filter and the AC component extracted by the high-pass filter.

3. 3. The signal processing circuit according to claim 2, further comprising a signal correction section that corrects an added signal, which is an output signal from the signal addition section, by applying a correction value calculated based on the DC component to the added signal.

4. a first signal processing unit that performs a first signal processing on the DC component; The signal processing circuit according to claim 1 , further comprising: a second signal processing unit that performs second signal processing on the AC component.

5. 5. The signal processing circuit according to claim 4, further comprising a signal adding section that adds a first output signal that is an output signal from the first signal processing section and a second output signal that is an output signal from the second signal processing section.

6. 6. The signal processing circuit according to claim 5, further comprising a signal correction section that corrects an added signal, which is an output signal from the signal addition section, by applying a correction value calculated based on the DC component to the added signal.

7. The signal processing circuit according to claim 1 , wherein the sensor is a magnetic sensor.

8. The sensor; The signal processing circuit of claim 1 which is integral with the sensor; A sensor unit comprising:

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