JP2014181981A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor allowing self diagnosis without using two sensor elements.SOLUTION: A current sensor 10 includes a bias magnet 30 that generates a bias magnetic field Bb in a vertical direction to a current magnetic field Bi generated by the flowing of a detected current I. The current sensor 10 includes a sensor element 40 that outputs a sine wave signal containing a sine value and a cosine wave signal containing a cosine value according to an angle θ formed by the bias magnetic field Bb and a synthetic magnetic field Bs composed of the current magnetic field Bi and the bias magnetic field Bb, on the basis of changes in resistance values of each of a plurality of magnetic resistance elements 41-48 when the plurality of magnetic resistance elements 41-48 are affected by an external magnetic field. The current sensor 10 further includes a self-diagnostic circuit 55 that receives the sine wave signal and the cosine wave signal from the sensor element 40 and performs failure determination of the sensor element 40 on the basis of the sine wave signal and the cosine wave signal.

Description

  The present invention relates to a current sensor provided with a self-diagnosis circuit.

  Conventionally, for example, Patent Document 1 has proposed a current detector having a failure diagnosis function. Specifically, in Patent Document 1, two magnetosensitive elements are arranged in one gap of a magnetic core, and a signal processing circuit having the same configuration is provided for each magnetosensitive element. There has been proposed a configuration of a current detector that determines a failure by comparing outputs. That is, the current detector is provided with two circuits each including a magnetosensitive element and a signal processing circuit.

JP 2000-275279 A

  However, in the above conventional technique, a fault diagnosis circuit having the same configuration as that of a circuit for detecting a current is separately provided in order to diagnose a fault of the current detector. For this reason, there exists a problem that the whole structure of an electric current detector becomes complicated, and the cost for performing a failure diagnosis becomes high.

  An object of the present invention is to enable self-diagnosis without using two sensor elements in a current sensor that detects current using a sensor element that detects magnetism.

  In order to achieve the above object, according to the first aspect of the present invention, the current sensor has a second direction perpendicular to the first magnetic field (Bi) generated by the detected current flowing through the detected current path (80). Magnetic field generating means (30) for generating a magnetic field (Bb) is provided.

  The current sensor has a plurality of magnetoresistive elements (41 to 48), and a plurality of magnetoresistive elements (41 to 48) when the plurality of magnetoresistive elements (41 to 48) are affected by an external magnetic field. Based on the change in resistance value, a sine value corresponding to the angle θ formed by the second magnetic field (Bb) and the combined magnetic field (Bs) composed of the first magnetic field (Bi) and the second magnetic field (Bb) is obtained. The sensor element (40) which outputs the sine wave signal containing and the cosine wave signal containing a cosine value is provided.

  The current sensor receives a sine wave signal and a cosine wave signal from the sensor element (40), and performs a predetermined calculation on the sine wave signal and the cosine wave signal to correspond to the magnitude of the detected current. An output arithmetic circuit (54) for outputting a signal is provided.

  Furthermore, the current sensor receives a sine wave signal and a cosine wave signal from the sensor element (40), and also makes a self-diagnosis circuit (55) for determining a failure of the sensor element (40) based on the sine wave signal and the cosine wave signal. It is characterized by having.

  As described above, since the self-diagnosis circuit (55) for performing the failure diagnosis based on the two signals of the sine wave signal and the cosine wave signal output from the sensor element (40) is provided, the sensor element ( 40) and an output arithmetic circuit (54) need not be provided separately. Therefore, a self-diagnosis can be enabled in the current sensor including one sensor element (40) and one output arithmetic circuit (54).

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a schematic diagram when the current sensor in 1st Embodiment of this invention is attached to the bus-bar. It is sectional drawing of the current sensor shown in FIG. It is a circuit diagram of the current sensor shown in FIG. Self-diagnosis result is a diagram showing the relationship between the current value and Vs ² + Vc ² in the case of normal. It is a graph showing a relationship between a current value and Vs ² + Vc ² when the offset fluctuation occurs in Vs. It is a graph showing a relationship between a current value and Vs ² + Vc ² when the offset fluctuation occurs in Vc. It is the figure which showed the output voltage output via a diagnostic terminal from a self-diagnosis circuit. It is the figure which showed the normal Lissajous waveform which the self-diagnosis circuit based on 2nd Embodiment of this invention drew. In 2nd Embodiment, when the offset fluctuation | variation arises in Vs, it is the figure which showed the Lissajous waveform which the self-diagnosis circuit drew. In 2nd Embodiment, when the offset fluctuation | variation arises in Vc, it is the figure which showed the Lissajous waveform which the self-diagnosis circuit drew. It is a circuit diagram of the current sensor which concerns on 4th Embodiment of this invention. In 4th Embodiment, it is the figure which showed the output voltage output via an output terminal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The current sensor according to the present embodiment detects, for example, a detected current flowing in a bus bar connected to an in-vehicle battery or the like.

  As shown in FIGS. 1 and 2, the current sensor 10 includes a substrate 20, a bias magnet 30, a sensor element 40, a circuit chip 50, leads 60, and a mold resin 70.

  The bias magnet 30 generates a bias magnetic field Bb in a direction perpendicular to the current magnetic field Bi generated when the detected current I flows through the bus bar 80 to be detected. The bias magnet 30 is installed on one surface 21 of the substrate 20. The bias magnet 30 plays a role of applying the bias magnetic field Bb to the sensor element 40.

  The sensor element 40 is a plate-shaped chip component having a plurality of magnetoresistive elements whose resistance values change when affected by an external magnetic field. As shown in FIG. 2, the sensor element 40 is disposed on the bias magnet 30. For this reason, for example, the variation in the angle of the bias magnetic field Bb affecting each magnetoresistive element is suppressed as compared with the case where the sensor element 40 is disposed near the corner of the rectangular bias magnet 30 or the like.

  The circuit chip 50 includes a signal processing circuit for performing a preset operation on the signal input from the sensor element 40. The circuit chip 50 is installed on the one surface 21 of the substrate 20.

  The lead 60 is a connection component for electrically connecting the outside and the current sensor 10. In the present embodiment, the plurality of leads 60 are arranged in a direction perpendicular to the longitudinal direction of the leads 60. Each lead 60 is electrically connected to the circuit chip 50 via a wire (not shown).

  The mold resin 70 is a sealing member that seals a part of the substrate 20, the bias magnet 30, the sensor element 40, the circuit chip 50, and the lead 60. Specifically, the mold resin 70 seals each component 20, 30, 40, 50, 60 so that the portion of the lead 60 opposite to the substrate 20, that is, the outer lead portion is exposed. Yes. Thereby, the current sensor 10 is formed as a mold IC. As a material of the mold resin 70, for example, an epoxy resin or the like is employed.

  The current sensor 10 having the above configuration is assembled to the bus bar 80 as shown in FIG. Specifically, the current sensor 10 is assembled to the bus bar 80 so that the direction of the current flowing through the bus bar 80, that is, the longitudinal direction of the bus bar 80 and the bias magnetic field Bb are parallel to each other. In other words, the current sensor 10 is assembled to the bus bar 80 so that the current magnetic field Bi generated by the detected current I flowing in the bus bar 80 and the bias magnetic field Bb are perpendicular to each other. The sensor element 40 is applied with a synthetic magnetic field Bs composed of a bias magnetic field Bb and a current magnetic field Bi.

  Next, the circuit configuration of the sensor element 40 and the circuit chip 50 in the current sensor 10 will be described. As shown in FIG. 3, the sensor element 40 includes a first detection unit 40a and a second detection unit 40b. The first detection unit 40a is configured such that the four magnetoresistive elements 41 to 44 form a bridge circuit. The second detection unit 40b is configured such that the four magnetoresistive elements 45 to 48 form a bridge circuit.

  Although not shown, the magnetoresistive elements 41 to 48 are configured as TMR elements in which a pin magnetic layer, a tunnel layer, a free magnetic layer, and an upper electrode are sequentially formed on the lower electrode. The pinned magnetic layer is a ferromagnetic metal layer whose magnetization direction is fixed. The tunnel layer is an insulating layer for allowing a current to flow from the free magnetic layer to the pinned magnetic layer by the tunnel effect. The free magnetic layer is a ferromagnetic metal layer whose magnetization direction changes under the influence of an external magnetic field.

  Here, as for each magnetoresistive element 41-44 which comprises the 1st detection part 40a, the magnetization direction of a pin magnetic layer is made mutually parallel, respectively. Moreover, the magnetization direction of the pin magnetic layer of each magnetoresistive element 45-48 which comprises the 2nd detection part 40b is with respect to the magnetization direction of the pin magnetic layer of each magnetoresistive element 41-44 which comprises the 1st detection part 40a. And vertical.

  In the sensor element 40, the magnetization directions of the magnetoresistive elements 41 to 44 of the first detection unit 40a are perpendicular to the bias magnetic field Bb, and the magnetization directions of the magnetoresistive elements 45 to 48 of the second detection unit 40b are It is installed on the bias magnet 30 so as to be parallel to the bias magnetic field Bb. Therefore, as shown in FIG. 1, when the angle formed by the bias magnetic field Bb and the combined magnetic field Bs is θ, the voltage signals Vs + and Vs− output from the first detection unit 40a include sine values, that is, sin θ. Signal (SIN output). On the other hand, the voltage signals Vc + and Vc− output from the second detection unit 40b are signals including a cosine value, that is, cos θ (COS output).

  Therefore, the sensor element 40 includes the bias magnetic field Bb and the combined magnetic field Bs based on the change in the resistance value of the plurality of magnetoresistance elements 41 to 48 when the plurality of magnetoresistance elements 41 to 48 are affected by the external magnetic field. A voltage signal corresponding to the angle θ formed by is output.

  The circuit chip 50 includes a power supply circuit 51, a first amplifier circuit 52, a second amplifier circuit 53, an output arithmetic circuit 54, and a self-diagnosis circuit 55. Further, the circuit chip 50 includes a power supply terminal 56 (V), an output terminal 57 (Vout), a diagnosis terminal 58 (Diag), and a ground terminal 59 (GND).

  The power supply circuit 51 is a constant voltage circuit that generates a constant voltage based on a power supply voltage V applied from an external power supply via a power supply terminal 56. Specifically, the power supply circuit 51 uses the constant voltage Vcc generated from the power supply voltage V as the midpoint of the magnetoresistive elements 41 and 44 of the first detection unit 40a of the sensor element 40 and the magnetoresistive element of the second detection unit 40b. Apply to the midpoint of 45,48. The power supply circuit 51 generates and applies voltages for operating the amplifier circuits 52 and 53, the output arithmetic circuit 54, and the self-diagnosis circuit 55, respectively.

  The first amplification circuit 52 is a circuit that amplifies the voltage signals Vs + and Vs− input from the first detection unit 40a of the sensor element 40 and outputs a sine wave signal Vs including a sine value, that is, sin θ. The first amplifier circuit 52 is configured as a differential amplifier circuit, for example. In this case, one input terminal of the first amplifier circuit 52 is connected to the midpoint of the magnetoresistive elements 43 and 44 of the first detection unit 40a, and the voltage signal Vs + is input to the input terminal. The other input terminal of the first amplifier circuit 52 is connected to the midpoint of the magnetoresistive elements 41 and 42, and the voltage signal Vs− is input to the input terminal. Accordingly, the first amplifier circuit 52 differentially amplifies the input voltage signals Vs + and Vs− and outputs a sine wave signal Vs to the output arithmetic circuit 54.

  The second amplifier circuit 53 is a circuit that amplifies the voltage signals Vc + and Vc− input from the second detection unit 40b of the sensor element 40 and outputs a cosine wave signal Vc including a cosine value, that is, cos θ. Similar to the first amplifier circuit 52, the second amplifier circuit 53 is configured as a differential amplifier circuit. In this case, one input terminal of the second amplifier circuit 53 is connected to the midpoint of the magnetoresistive elements 47 and 48 of the second detection unit 40b, and the voltage signal Vc + is input to the input terminal. The other input terminal of the second amplifier circuit 53 is connected to the midpoint of the magnetoresistive elements 45 and 46, and the voltage signal Vc− is input to the input terminal. Therefore, the second amplifier circuit 53 differentially amplifies the input voltage signals Vc + and Vc− and outputs a cosine wave signal Vc to the output arithmetic circuit 54.

  The sine wave signal Vs is expressed as Vs = A · sin θ, for example. The cosine wave signal Vc is expressed as Vc = A · cos θ, for example. Here, since each amplifier circuit 52 and 53 is the same structure, an amplification factor becomes the same value. Moreover, since each detection part 40a, 40b is comprised by the magnetoresistive elements 41-48 made into the same structure except the magnetization direction of a pin magnetic layer, a temperature characteristic also becomes the same value. Therefore, “A” is a parameter common to the sine wave signal Vs and the cosine wave signal Vc.

  The output calculation circuit 54 receives the sine wave signal Vs and the cosine wave signal Vc from the sensor element 40, and performs a predetermined calculation on the sine wave signal Vs and the cosine wave signal Vc to obtain the magnitude of the detected current I. It is a circuit that outputs a corresponding sensor signal. Specifically, the output arithmetic circuit 54 uses the sine wave signal Vs and the cosine wave signal Vc input from the amplifier circuits 52 and 53, and the tangent value (tan θ) at the angle θ between the bias magnetic field Bb and the combined magnetic field Bs. And outputs a signal corresponding to the tangent value to the outside through the output terminal 57 as a sensor signal. That is, the output calculation circuit 54 performs a calculation of dividing the sine wave signal Vs by the cosine wave signal Vc to obtain a tangent value (tan θ), and outputs a signal corresponding to the calculation result as a sensor signal.

  As shown in FIG. 1, tan θ = (current magnetic field Bi) / (bias magnetic field Bb), and the bias magnetic field Bb is constituted by the bias magnet 30 and is constant. Is a signal proportional to the current magnetic field Bi generated by the current I to be detected flowing through the. That is, the sensor signal is a signal that changes linearly with respect to the detected current I flowing through the bus bar 80. The output calculation circuit 54 outputs a signal corresponding to tan θ as a sensor signal.

  Note that “output a signal corresponding to a tangent value as a sensor signal” means that a value obtained by adding a predetermined offset to the calculated tangent value is output as a sensor signal, or the calculated tangent value is directly used as a sensor signal. Or output. In this embodiment, the calculated tangent value is output as it is.

  The self-diagnosis circuit 55 inputs the sine wave signal Vs and the cosine wave signal Vc from the sensor element 40, and determines the failure of the sensor element 40 or each of the amplification circuits 52 and 53 based on the sine wave signal Vs and the cosine wave signal Vc. It is a circuit to perform. Since the sine wave signal Vs and the cosine wave signal Vc are signals obtained via the sensor element 40 and the amplifier circuits 52 and 53, the self-diagnosis circuit 55 is one of the sensor element 40 and the amplifier circuits 52 and 53. It is diagnosed that there is a possibility of failure.

Specifically, the self-diagnosis circuit 55 calculates the sum of Vs ² and Vc ^2, and compares the calculation result with a preset failure determination value to determine a failure of the sensor element 40. The failure determination value is a boundary value, that is, a threshold value between a normal value range and an abnormal value range of Vs ² + Vc ² , and is stored in a storage unit provided in the self-diagnosis circuit 55 at the time of product shipment.

When the sensor element 40 is operating normally, as described above, the sine wave signal Vs is represented by Vs = A · sin θ, and the cosine wave signal Vc is represented by Vc = A · cos θ. Therefore, the sum of Vs ² and Vc ² is Vs ² + Vc ² = A ² (sin ² θ + cos ² θ) = A ² . That is, the sum of Vs ² and Vc ² is a constant value regardless of the current value of the detected current I, as shown in FIG. In such a case, the self-diagnosis circuit 55 compares the failure determination value and A ^2, the sensor element 40 and the amplifier circuits 52 and 53 as well as determined that the operation result A ² is included in the normal range Determined to be normal.

On the other hand, when an abnormality occurs due to deterioration of the sensor element 40, a failure component is included in the sine wave signal Vs and the cosine wave signal Vc. For example, when an offset variation occurs in the sine wave signal Vs, the sine wave signal Vs is expressed by Vs = A · sin θ + Voffs. For this reason, the sum of Vs ² and Vc ² includes a component of Voffs and a component of sin θ. Therefore, as shown in FIG. 5, the sum of Vs ² and Vc ² is not constant with respect to the current value.

When an offset variation occurs in the cosine wave signal Vc, the cosine wave signal Vc is expressed by Vc = A · cos θ + Voffc. Therefore, the sum of Vs ² and Vc ² includes a component of Voffc and a component of cos θ. Therefore, as shown in FIG. 6, the sum of Vs ² and Vc ² is not constant with respect to the current value.

Thus, when the sum of Vs ² and Vc ² is not constant with respect to the current value, the sum of Vs ² and Vc ² exceeds the normal range. Accordingly, the self-diagnosis circuit 55 compares the sum of Vs ² and Vc ² with the failure determination value, determines that the calculation result is abnormal, and abnormalities are detected in either the sensor element 40 or each of the amplifier circuits 52 and 53. It is determined that it has occurred.

  The self-diagnosis circuit 55 outputs a failure diagnosis result to the outside via the diagnosis terminal 58 after making the failure determination as described above. Specifically, as shown in FIG. 7, when the self-diagnosis result is normal, the self-diagnosis circuit 55 outputs the output voltage during normal operation as the output voltage during normal self-diagnosis. That is, the self-diagnosis circuit 55 does not change the voltage applied to the diagnosis terminal 58 when the self-diagnosis is normal.

  On the other hand, when the self-diagnosis result is abnormal, the self-diagnosis circuit 55 outputs a higher output voltage than during normal operation. That is, when the self-diagnosis is abnormal, the self-diagnosis circuit 55 changes the voltage applied to the diagnosis terminal 58. In this way, the self-diagnosis circuit 55 transmits an abnormality to the outside.

  As described above, the present embodiment is characterized by including the self-diagnosis circuit 55 that performs failure diagnosis based on the two signals of the sine wave signal Vs and the cosine wave signal Vc. Further, since the self-diagnosis circuit 55 performs failure diagnosis using the angle components of the sine wave signal Vs and the cosine wave signal Vc, separate configurations of the sensor element 40 and the output arithmetic circuit 54 for failure diagnosis are provided. It can be unnecessary. Therefore, the self-diagnosis can be enabled by one sensor element 40 and one output arithmetic circuit 54 provided in the current sensor 10.

  Here, the detected current I flowing through the bus bar 80 is not always a constant value. The current sensor 10 detects an average value or a peak value of the current value for such a measurement object “current”. Therefore, in order to confirm whether or not the current value detected by the current sensor 10 is a really correct value, conventionally, it has been necessary to provide a current detection unit having exactly the same configuration and compare both values. However, the current sensor 10 according to the present embodiment performs failure determination using the sine wave signal Vs and the cosine wave signal Vc including the failure component. Therefore, it is not necessary to compare the output of the sensor element 40 with the output of another sensor element having the same configuration, and the self-diagnosis function of the current sensor 10 can be realized only by providing the self-diagnosis circuit 55. .

  As for the correspondence between the description of the present embodiment and the description of the claims, the current magnetic field Bi corresponds to the “first magnetic field” of the claims, and the bias magnetic field Bb corresponds to the “first” of the claims. Corresponds to “two magnetic fields”. The bias magnet 30 corresponds to “magnetic field generating means” in the claims, and the bus bar 80 corresponds to “detected current path” in the claims.

(Second Embodiment)
In the present embodiment, parts different from the first embodiment will be described. In the present embodiment, the self-diagnosis circuit 55 performs failure determination based on the Lissajous waveform drawn by the sine wave signal Vs and the cosine wave signal Vc.

  That is, the self-diagnosis circuit 55 draws a Lissajous waveform by the sine wave signal Vs and the cosine wave signal Vc input from the amplifier circuits 52 and 53. As shown in FIG. 8, the Lissajous waveform is a plane figure drawn on orthogonal coordinates by synthesizing two simple vibrations of the sine wave signal Vs and the cosine wave signal Vc. FIG. 8 shows a normal Lissajous waveform at the time of product shipment, for example.

  When the offset fluctuation occurs in the sine wave signal Vs, the Lissajous waveform moves in the sin θ-axis direction from the normal time as shown in FIG. On the other hand, when an offset variation occurs in the cosine wave signal Vc, the Lissajous waveform moves in the cos θ axis direction from the normal time as shown in FIG.

  Therefore, the self-diagnosis circuit 55 compares the Lissajous waveform drawn by the sine wave signal Vs and the cosine wave signal Vc with a failure determination value based on a preset Lissajous waveform at the time of product shipment, thereby obtaining a sensor element. 40 failure determinations are made. That is, the self-diagnosis circuit 55 determines whether or not a predetermined amount has deviated from the circular waveform at the time of product shipment. As described above, the failure can be easily visually determined by drawing the Lissajous waveform.

(Third embodiment)
In the present embodiment, parts different from the first and second embodiments will be described. In the present embodiment, the self-diagnosis circuit 55 compares sin θ with (1-cos ² θ) ^1/2 or compares (1-sin ² θ) ^1/2 with cos θ. The failure determination of the sensor element 40 is performed. Thus, the sine and cosine can be expressed by sin θ or cos θ. Therefore, the self-diagnosis circuit 55 can also perform failure determination using the sine wave signal Vs and the cosine wave signal Vc without using the failure determination value.

(Fourth embodiment)
In the present embodiment, parts different from the first to third embodiments will be described. As shown in FIG. 11, in the circuit chip 50 according to the present embodiment, the self-diagnosis circuit 55 is connected to the output terminal 57 (Vout / Diag). As a result, the self-diagnosis circuit 55 outputs the self-diagnosis result to the outside via the output terminal 57. In other words, the output terminal 57 functions as a dual-purpose terminal that outputs both the sensor signal and the self-diagnosis result.

  Normally, as shown in FIG. 12, the output arithmetic circuit 54 outputs a normal state output voltage within a certain range. However, when the self-diagnosis circuit 55 determines that the sensor element 40 has failed, the self-diagnosis circuit 55 changes the output of the output arithmetic circuit 54.

  Specifically, the self-diagnosis circuit 55 applies a voltage value exceeding the normal state output voltage within a certain range to the output terminal 57. In the present embodiment, the self-diagnosis circuit 55 outputs a voltage higher than the maximum value of the normal state output voltage within a certain range when the self-diagnosis is abnormal. In this way, the self-diagnosis result can also be output to the outside via the output terminal 57. Further, the diagnosis terminal 58 can be omitted, and the configuration of the circuit chip 50 can be simplified.

(Other embodiments)
The configuration of the current sensor 10 shown in each of the above embodiments is an example, and the present invention is not limited to the configuration shown above, and other configurations that can realize the present invention can be used. For example, regarding the positional relationship between the bias magnet 30 and the sensor element 40, as long as the relationship between the magnetization direction of the pin magnetic layer of each of the magnetoresistive elements 41 to 48 and the direction of the bias magnetic field Bb can be maintained as described above, An arrangement relationship may be used.

  In each of the above embodiments, each of the magnetoresistive elements 41 to 48 of the sensor element 40 is configured as a TMR element, but may be configured as a GMR element.

  In each of the above embodiments, the amplifier circuits 52 and 53 are provided on the circuit chip 50, but may be provided on the sensor element 40. Even in this case, the output calculation circuit 54 performs a predetermined calculation on the sine wave signal Vs and the cosine wave signal Vc.

  In the fourth embodiment, the self-diagnosis circuit 55 outputs a voltage higher than the maximum value of the normal state output voltage in a certain range when the self-diagnosis is abnormal. A low voltage may be output.

  Furthermore, in each said embodiment, although the current sensor 10 was comprised so that the to-be-detected current I which flows into the bus-bar 80 connected to a vehicle-mounted battery etc., this is an example of application of the current sensor 10. FIG. Therefore, the measurement target is not limited to the vehicle bus bar 80, and the current sensor 10 may be applied to wiring used for other purposes.

30 Bias magnet (magnetic field generating means)
40 Sensor elements 41 to 48 Magnetoresistive elements 54 Output arithmetic circuit 55 Self-diagnosis circuit 58 Diag terminal 80 Bus bar (detected current path)
Bi current magnetic field (first magnetic field)
Bb Bias magnetic field (second magnetic field)

Claims (6)

Magnetic field generating means (30) for generating a second magnetic field (Bb) in a direction perpendicular to the first magnetic field (Bi) generated by flowing of the detected current through the detected current path (80);
Resistance values of the plurality of magnetoresistive elements (41 to 48) when the plurality of magnetoresistive elements (41 to 48) are affected by an external magnetic field. Is a sine value corresponding to an angle θ formed by the second magnetic field (Bb) and the combined magnetic field (Bs) composed of the first magnetic field (Bi) and the second magnetic field (Bb). A sensor element (40) for outputting a sine wave signal including a cosine wave signal including a cosine value;
A sensor corresponding to the magnitude of the detected current by inputting the sine wave signal and the cosine wave signal from the sensor element (40) and performing a predetermined calculation on the sine wave signal and the cosine wave signal. An output arithmetic circuit (54) for outputting a signal;
In addition,
A self-diagnosis circuit (55) for inputting the sine wave signal and the cosine wave signal from the sensor element (40) and determining a failure of the sensor element (40) based on the sine wave signal and the cosine wave signal. A current sensor comprising: When the sine wave signal is defined as Vs and the cosine wave signal is defined as Vc,
The self-diagnosis circuit (55) includes a sum of Vs ² and Vc ^2, by comparing the failure determination value, and to claim 1, characterized in that the failure determination of the sensor element (40) The current sensor described.   The self-diagnosis circuit (55) performs failure determination of the sensor element (40) by comparing a Lissajous waveform drawn by the sine wave signal and the cosine wave signal with a failure determination value. The current sensor according to claim 1. The sine wave signal is a signal including sin θ, and the cosine wave signal is a signal including cos θ,
The self-diagnosis circuit (55) compares the sin θ with (1-cos ² θ) ^1/2 or compares the (1-sin ² θ) ^1/2 with cos θ. The current sensor according to claim 1, wherein a failure determination of the sensor element is performed.   The current sensor according to any one of claims 1 to 4, further comprising a diagnosis terminal (58) for outputting a failure diagnosis result of the self-diagnosis circuit (55) to the outside.   The self-diagnosis circuit (55) changes the output of the output calculation circuit (54) when it is determined that the sensor element (40) is out of order. The current sensor according to one.

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