Current sensor

Abstract

The invention provides a current sensor. The current sensor may be provided with a control circuit that sets the amplification factor of the amplification circuit to a first amplification factor when the amplitude of the detection signal or the output signal is included in a predetermined amplitude range, and sets the amplification factor of the amplification circuit to a second amplification factor when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range. And a control circuit that sets the amplification factor of the amplification circuit to a second amplification factor that is lower than the first amplification factor. A bias signal that suppresses a change in amplitude of an output signal generated in response to switching the amplification factor of the amplifier circuit between the first amplification factor and the second amplification factor is added to the detection signal during a period in which the amplification factor of the amplifier circuit is set to the second amplification factor, and is input to the first input terminal.

Description

Technical Field

[0001] The present invention relates to a current sensor. Background Art

[0002] Patent document 1 discloses a current sensor having a gain that eliminates changes in detection gain in at least a portion of a gain variation frequency band. Patent document 2 discloses a method of alternately switching input ranges of large and small using a gain switching circuit while reading digital values ​​by oversampling at a higher sampling frequency than in the past in A / D conversion. Patent document 3 discloses an amplifier capable of automatically switching gain according to input voltage. Patent document 4 discloses a method of making the gain of an operational amplifier variable based on the output voltage of a current detector.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-038196

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-152471

[0007] Patent Document 3: Japanese Patent Application Publication No. 2004-336300

[0008] Patent Document 4: Japanese Patent Application Publication No. 2010-197065 Summary of the invention

[0009] Problems to be solved by the invention

[0010] A current sensor is desired that suppresses fluctuations in the amplitude of an output signal output from an amplifier that is caused by switching of a gain and that has a wide measurable current range.

[0011] Means for solving problems

[0012] A current sensor according to one embodiment of the present invention may include a detection unit that outputs a detection signal corresponding to a magnetic field generated in a conductor due to the flow of a measured current. The current sensor may include an amplifier circuit having a first input terminal, a second input terminal, and an output terminal, amplifying the detection signal input via the first input terminal, and outputting an output signal via the output terminal. The current sensor may include a control circuit that can input a bias signal to the first input terminal. The amplifier circuit may be configured to switch between at least a first amplification factor and a second amplification factor lower than the first amplification factor. The control circuit may stop the input of the bias signal to the first input terminal during a period in which the first amplification factor is set, and input the bias signal to the first input terminal during a period in which the second amplification factor is set.

[0013] In the current sensor, the control circuit may set the amplification factor of the amplifier circuit to the first amplification factor when the amplitude of the detection signal or the output signal is within a predetermined amplitude range, and may set the amplification factor of the amplifier circuit to the second amplification factor when the amplitude of the detection signal or the output signal is not within the predetermined amplitude range. The control circuit may suppress a change in the amplitude of the output signal caused by switching the amplification factor of the amplifier circuit between the first amplification factor and the second amplification factor by inputting the bias signal to the first input terminal.

[0014] In the current sensor, the amplifier circuit includes an impedance element having one end connected to the first input terminal, and the impedance element is an impedance that suppresses a change in a feedback ratio of the amplifier circuit caused by adding the bias signal to the detection signal.

[0015] In any of the current sensors, a reference potential may be applied to the second input terminal, and a potential based on the reference potential may be applied to the other end of the impedance element.

[0016] In any of the current sensors, the amplifier circuit may include a feedback resistor circuit, the feedback resistor circuit being connected between the output terminal and the first input terminal, and being set to a first resistance value in the case of the first amplification factor, and being set to a second resistance value lower than the first resistance value in the case of the second amplification factor. The control circuit may set the resistance value of the feedback resistor circuit to the first resistance value when the amplitude of the detection signal or the output signal is included in the predetermined amplitude range, and may set the resistance value of the feedback resistor circuit to the second resistance value when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range.

[0017] In any of the current sensors, the feedback resistance circuit may include: a first resistance element connected between the output terminal and the first input terminal; and a second resistance element connected between the output terminal and the first input terminal in parallel with the first resistance element.

[0018] It may be that, when the amplitude of the detection signal or the output signal is included in the predetermined amplitude range, the control circuit controls the feedback resistance circuit in a manner that the first resistance element is electrically connected between the output terminal and the first input terminal and the second resistance element is not electrically connected between the output terminal and the first input terminal; and when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range, the control circuit controls the feedback resistance circuit in a manner that the first resistance element and the second resistance element are electrically connected between the output terminal and the first input terminal.

[0019] In any of the current sensors, it may be that, when the amplitude of the detection signal or the output signal exceeds the upper limit value of the predetermined amplitude range, the control circuit adds a first bias signal of a first potential to the detection signal as the bias signal, and when the amplitude of the detection signal or the output signal is less than the lower limit value of the predetermined amplitude range, the control circuit adds a second bias signal of a second potential lower than the first potential to the detection signal as the bias signal.

[0020] In any of the current sensors, the amplifier circuit may have: a third resistor element, one end of which is input with the detection signal, and the other end of the third resistor element is connected to the first input terminal; a fourth resistor element, one end of which is applied with a reference potential, and the other end of the fourth resistor element is connected to the first input terminal; a fifth resistor element, one end of which is input with the bias signal, and the other end of the fifth resistor element is connected to the first input terminal; a first switch, which switches whether the second resistor element is electrically connected between the output terminal and the first input terminal; a second switch, which switches whether the fourth resistor element is electrically connected to the first input terminal; and a third switch, which switches whether the fifth resistor element is electrically connected to the first input terminal. The control circuit may have a comparator, which outputs a working signal and a polarity signal when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range, the working signal causes the first switch, the second switch, and the third switch to operate, and electrically connect the second resistor element between the output terminal and the first input terminal, the fourth resistor element is electrically connected to the first input terminal, and the fifth resistor element is electrically connected to the first input terminal, and the polarity signal indicates whether the amplitude of the detection signal or the output signal exceeds the upper limit value of the predetermined amplitude range or is less than the lower limit value of the predetermined amplitude range. The control circuit may have a selection circuit that, based on the working signal and the polarity signal, inputs a first bias signal of a first potential as the bias signal to the one end of the fifth resistor element when the amplitude of the detection signal or the output signal exceeds the upper limit value of the predetermined amplitude range, and inputs a second bias signal of a second potential lower than the first potential as the bias signal to the one end of the fifth resistor element when the amplitude of the detection signal or the output signal is less than the lower limit value of the predetermined amplitude range.

[0021] In any of the current sensors, the comparator may control the output of the working signal and the polarity signal by comparing a first threshold signal of a third potential and a second threshold signal of a fourth potential with the detection signal or the output signal, the third potential representing the upper limit of the predetermined amplitude range obtained by adding a threshold potential to the reference potential, and the fourth potential representing the lower limit of the predetermined amplitude range obtained by subtracting the threshold potential from the reference potential. The control circuit may further include an adjustment circuit that inputs the first bias signal of the first potential and the second bias signal of the second potential to the selection circuit, the first potential being obtained by adding an adjustment potential based on the threshold potential to the reference potential, and the second potential being obtained by subtracting the adjustment potential from the reference potential.

[0022] In any of the current sensors, the resistance values ​​of the fourth resistor and the fifth resistor may be twice the resistance value of the third resistor. The resistance values ​​of the first resistor and the second resistor may be four times the resistance value of the third resistor.

[0023] In any of the above current sensors, the detection unit may include at least one magnetic sensor.

[0024] In any of the current sensors, the at least one magnetic sensor may be a Hall element, a magnetoresistive element (MR), a giant magnetoresistive element (GMR), a tunnel magnetoresistive element (TMR), a magneto-impedance element (MI element), or an inductive sensor.

[0025] A current sensor according to one embodiment of the present invention may include a detection unit that outputs a detection signal corresponding to a magnetic field generated in a conductor due to the flow of a measured current. The current sensor may include an amplifier circuit having a first input terminal, a second input terminal, and an output terminal, amplifying the detection signal input via the first input terminal, and outputting an output signal via the output terminal. The current sensor may include a control circuit that can input a bias signal to the first input terminal and the second input terminal. The amplifier circuit may be configured to be able to switch between at least a first amplification factor and a second amplification factor lower than the first amplification factor. The control circuit may input the bias signal to the first input terminal during a period in which the second amplification factor is set, and stop inputting the bias signal to the first input terminal during a period in which the first amplification factor is set.

[0026] It should be noted that the above summary of the invention does not list all the features of the present invention. In addition, subsets of these feature groups may also constitute inventions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. 1 is a diagram showing an example of a circuit configuration of a current sensor including a correction unit.

[0028] Figure 2 It is a diagram showing an example of the circuit configuration of the current sensor according to the first embodiment.

[0029] Figure 3 This is a diagram showing an example of a circuit configuration of an amplifier section when an inverting amplifier circuit is used.

[0030] Figure 4 It is a diagram showing a modification of the circuit configuration of the current sensor according to the first embodiment.

[0031] Figure 5A 2 is a diagram showing an example of output characteristics of the output signal VOUT with respect to the detection signal VIN.

[0032] Figure 5B 2 is a diagram showing an example of output characteristics of the output signal VOUT with respect to the detection signal VIN.

[0033] Fig. 6A When switches SW2a, SW2b, and SW2c are in the off state Figure 3 Block diagram of an operational amplifier.

[0034] Figure 6B When switches SW2a, SW2b, and SW2c are turned on Figure 3 Block diagram of an operational amplifier.

[0035] Figure 7 is a diagram showing Figure 3 A diagram showing an example of a Bode diagram of the relationship between F0 and the feedback ratio β when the finite gain A0 of the operational amplifier has a first-order LPF characteristic.

[0036] Figure 8 It is a diagram showing an example of a circuit configuration of a current sensor according to the second embodiment.

[0037] Fig. 9 This is a diagram showing an example of a circuit configuration of an amplifier section when an inverting amplifier circuit is used.

[0038] Fig.10 FIG. 1 is a diagram showing a modified example of the circuit configuration of the amplifier section in the case of using an inverting amplifier circuit.

[0039] Description of symbols

[0040] 100 Current Sensor

[0041] 110A current path

[0042] 120a, 120b magnetic sensor

[0043] 130 Receiving Department

[0044] 140 Filtering Unit

[0045] 150a, 150b Amplification section

[0046] 160 Output

[0047] 170 Chopper Circuit

[0048] 180 Correction Department

[0049] 200, 700 current sensor

[0050] 210 conductor

[0051] 220 Magnetic Sensor

[0052] 250, 750 amplification unit

[0053] 260 amplifier circuit

[0054] 262 Operational Amplifier

[0055] 262a Inverting input terminal

[0056] 262b non-inverting input terminal

[0057] 262c output terminal

[0058] 264 Feedback Resistor Circuit

[0059] 266, 268, 271, 272, 273 resistor elements

[0060] 280 Output

[0061] 290 Correction Department

[0062] 300 control circuit

[0063] SW1a, SW1b, SW2a, SW2b, SW2c switches

[0064] 320 adjustment circuit

[0065] 330 Comparator

[0066] 340 Selection Circuit

[0067] DET working signal

[0068] DET_POL polarity signal

[0069] VIN detection signal

[0070] VOUT output signal

[0071] G Adjustment Value

[0072] HL threshold signal (lower limit)

[0073] HV threshold signal (upper limit)

[0074] VS, VHX, VLX bias signals

[0075] VREF reference potential DETAILED DESCRIPTION

[0076] Hereinafter, the present invention will be described by way of the embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all combinations of features described in the embodiments are necessarily essential to the solution means of the invention.

[0077] In a current sensor using a magnetic sensor that detects a magnetic field generated in a conductor by a flow of current, it can be considered that: for an amplifier that amplifies a signal output by the magnetic sensor, a correction unit composed of a non-volatile memory or a register is used to correct the bias or adjust the gain, thereby expanding the measurable current range.

[0078] Figure 1 An example of a circuit structure of a current sensor 100 having the correction unit described above is shown. The current sensor 100 has a structure in which the influence of the interfering bias magnetic field is reduced by detecting the measurement current flowing to the current paths 110a and 110b using two pairs of magnetic sensors 120a and 120b. The chopper circuit 170 is connected between the magnetic sensors 120a and 120b and the receiving unit 130, and chops the signals output by the magnetic sensors 120a and 120b. The chopper circuit 170 calculates the difference between the signals in the 0-degree direction and the 90-degree direction output by the magnetic sensors 120a and 120b, removes the bias voltage, etc., and outputs the processed signal to the receiving unit 130.

[0079] The receiving unit 130 is connected to the amplifier 150a, and is a wiring or terminal for connecting the signal processed by the chopper circuit 170 to the amplifier 150a. The amplifier 150a amplifies the signal with a predetermined gain and outputs it to the filter 140. The filter 140 is connected to the amplifier 150b, and filters the signal received by the receiving unit 130 in a predetermined frequency range so as to reduce the amplitude and outputs it.

[0080] The amplifier 150b is connected to the output unit 160, and amplifies the amplitude of the signal with a predetermined gain and outputs the amplified signal. The output unit 160 outputs an output signal representing the measured current based on the filtered signal received from the amplifier 150b.

[0081] The correction unit 180 is connected to the amplifiers 150 a and 150 b and the filter unit 140 , and corrects the signal to adjust the current value signal output from the output unit 160 to a desired unique value.

[0082] In such a current sensor 100, each time the gain setting is changed, initial setting needs to be performed in the calibration unit 180. If the gain setting is not changed, the measurable current range cannot be expanded. In addition, even when the gain of the amplifier is switched according to the amplitude of the signal output from the magnetic sensor, the amplitude of the signal output from the amplifier may change due to the switching of the gain.

[0083] Therefore, a current sensor is desired that can expand a measurable current range while suppressing a change in the amplitude of a signal output from an amplifier that is caused by switching of a gain.

[0084] Figure 2 1 is a diagram showing an example of a circuit structure of a current sensor 200 according to the first embodiment. The current sensor 200 detects a measurement current flowing to a conductor 210 as a current path. The current sensor 200 includes a magnetic sensor 220, an amplifier 250, and an output unit 280. The current sensor 200 may be a semiconductor package in which at least one structure of the current sensor 200 is arranged on a substrate and covered by a package, and the package is made of an insulating material such as a molded resin or ceramic.

[0085] The current sensor 200 processes the signal output from the magnetic sensor 220 in response to the flow of the measurement current to the conductor 210 , and outputs an output signal indicating the current amount, rise or fall, etc. of the measurement current.

[0086] The conductor 210 may be a conductor such as a metal provided on a substrate built into a semiconductor package. The conductor 210 may be a part of a lead frame constituting a pair of terminals through which the measurement current flows. Figure 2 In the conductor 210, in a plan view, the measurement current flows in a right-hand rotation so as to surround the magnetic sensor 220. The cross-sectional shape of the conductor 210 relative to the direction of the current flow may be a quadrilateral, a square, a trapezoid, a polygon, a circle, an ellipse, or the like, or a combination thereof. If the measurement current flows to the conductor 210, the conductor 210 generates a right-hand rotation (clockwise) magnetic field around the conductor 210 relative to the direction of the measurement current flow. Thus, a magnetic field is applied approximately downward relative to the magnetic sensor 220.

[0087] The magnetic sensor 220 is arranged near the conductor 210. The magnetic sensor 220 is an example of a magnetoelectric conversion element. The magnetoelectric conversion element includes at least one of a Hall element, a magnetoresistive element (MR), a giant magnetoresistive element (GMR), a tunnel magnetoresistive element (TMR), a magnetoimpedance element (MI element), and an inductance sensor. The magnetic sensor 220 is an example of a detection unit that outputs a detection signal corresponding to a magnetic field generated in the conductor 210 due to the flow of a measurement current.

[0088] The magnetic sensor 220 may be built in the same package as the conductor 210 . The magnetic sensor 220 detects a magnetic field generated by a measurement current flowing through the conductor 210 , and outputs a detection signal having a current value or a voltage value corresponding to the magnetic field to the amplifier 250 .

[0089] The amplifier 250 is connected to the output unit 280. The amplifier 250 may include an inverting amplifier circuit or a non-inverting amplifier circuit using an operational amplifier. The amplifier 250 may amplify the amplitude of the signal at a predetermined gain and output it. The amplifier 250 feeds back the output signal VOUT, determines the output result using a predetermined threshold, and controls it in a manner smaller than the predetermined gain. In addition, the amplifier 250 may also control the gain based on a threshold selected from a plurality of thresholds.

[0090] The output unit 280 outputs a sensor output signal VSOUT indicating the magnitude of the measured current according to the signal received from the amplifier 250. The output unit 280 may be an operational amplifier or a comparator. The amplifier 250 may also feed back the sensor output signal VSOUT to control the gain of the amplifier 250.

[0091] The current sensor 200 involved in the first embodiment includes a magnetoelectric conversion element such as a Hall element as a magnetic sensor 220. However, the number of magnetic sensors 220 included in the current sensor 200 is not limited to one. The current sensor 200 may include a plurality of magnetic sensors 220. For example, when viewed from above, a pair of magnetic sensors 220 may be arranged opposite to each other with a conductor 210 sandwiched therebetween. The current sensor 200 may amplify the signal after eliminating the influence of the magnetic field generated externally based on the outputs of the plurality of magnetoelectric conversion elements and the plurality of magnetoelectric conversion elements, using the amplifier 250. The current sensor 200 may also include Figure 1 The chopper circuit 170, the receiving unit 130 and the filtering unit 140 are shown.

[0092] Figure 3 An example of a circuit configuration of the amplifier 250 when an inverting amplifier circuit is used is shown. The amplifier 250 includes an amplifier circuit 260 and a control circuit 300. The amplifier circuit 260 includes an operational amplifier 262 and a feedback resistor circuit 264.

[0093] The operational amplifier 262 has an inverting input terminal 262a, a non-inverting input terminal 262b, and an output terminal 262c. The inverting input terminal 262a is an example of a first input terminal. The non-inverting input terminal 262b is an example of a second input terminal. The operational amplifier 262 amplifies the detection signal VIN from the magnetic sensor 220 input via the inverting input terminal 262a, and outputs the output signal VOUT via the output terminal 262c.

[0094] When the amplitude of the output signal VOUT is included in the predetermined amplitude range W, the control circuit 300 sets the amplification factor of the amplifier circuit 260 to the first amplification factor. When the amplitude of the output signal VOUT is not included in the predetermined amplitude range W, the control circuit 300 sets the amplification factor of the amplifier circuit 260 to the second amplification factor lower than the first amplification factor. In this way, the current range that can be measured by the current sensor 200 can be expanded. However, when the amplification factor of the amplifier circuit 260 is switched between the first amplification factor and the second amplification factor, the amplitude of the output signal VOUT changes. If the amplitude of the output signal VOUT changes, the measurement accuracy of the current sensor 200 will be deviated.

[0095] Therefore, the control circuit 300 adds the bias signal VS to the detection signal VIN and inputs it to the inverting input terminal 262a during the period when the amplification factor of the amplifier circuit 260 is set to the second amplification factor. The bias signal VS suppresses the change in the amplitude of the output signal VOUT corresponding to the switching of the amplification factor of the amplifier circuit 260 between the first amplification factor and the second amplification factor.

[0096] The feedback resistor circuit 264 is connected between the output terminal 262c and the inverting input terminal 262a, and is set to a first resistance value in the case of the first amplification factor, and is set to a second resistance value lower than the first resistance value in the case of the second amplification factor. When the amplitude of the output signal VOUT is included in the predetermined amplitude range W, the control circuit 300 sets the resistance value of the feedback resistor circuit 264 to the first resistance value, and when the amplitude of the output signal VOUT is not included in the predetermined amplitude range W, the control circuit 300 sets the resistance value of the feedback resistor circuit 264 to the second resistance value.

[0097] The feedback resistance circuit includes a resistance element 266 and a resistance element 268. The resistance element 266 is an example of a first resistance element connected between the output terminal 262c and the inverting input terminal 262a. The resistance element 268 is an example of a second resistance element connected between the output terminal 262c and the inverting input terminal 262a in parallel with the resistance element 266. The resistance value R2 of the resistance element 272 and the resistance element 273 may be twice the resistance value R1 of the resistance element 271 (R2=2×R1). The resistance value R3 of the resistance element 266 and the resistance element 268 may be four times the resistance value R1 of the resistance element 271 (R3=4×R1).

[0098] When the amplitude of the output signal VOUT is within the predetermined amplitude range W, the control circuit 300 controls the feedback resistor circuit 264 so that the resistor element 266 is electrically connected between the output terminal 262c and the inverting input terminal 262a and the resistor element 268 is not electrically connected between the output terminal 262c and the inverting input terminal 262a. When the amplitude of the output signal VOUT is not within the predetermined amplitude range W, the control circuit 300 controls the feedback resistor circuit 264 so that the resistor element 266 and the resistor element 268 are electrically connected between the output terminal 262c and the inverting input terminal 262a.

[0099] Furthermore, when the amplitude of the output signal VOUT exceeds the upper limit value VH of the predetermined amplitude range W, the control circuit 300 adds the first bias signal VHX of the first potential to the detection signal VIN as the bias signal VS. When the amplitude of the output signal VOUT is less than the lower limit value VL of the predetermined amplitude range W, the control circuit 300 adds the second bias signal VLX of the second potential lower than the first potential to the detection signal VIN as the bias signal VS.

[0100] Here, if the bias signal VS is added to the detection signal VIN, the impedance when viewed from the inverting input terminal 262a of the operational amplifier 262 changes. Under this influence, the feedback ratio β of the operational amplifier 262 changes. If the feedback ratio β of the operational amplifier 262 changes, the frequency responsiveness of the operational amplifier 262 changes.

[0101] Therefore, the amplifier circuit 260 has a resistor element 272 as an impedance element having one end connected to the inverting input terminal 262a, and the impedance element is an impedance that suppresses the change in the feedback ratio of the amplifier circuit 260 (operational amplifier 262) caused by adding the bias signal VS to the detection signal VIN. The reference potential VREF applied to the inverting input terminal 262a can be applied to the other end of the resistor element 272.

[0102] The amplifier circuit 260 further includes a resistor 271 to which the detection signal VIN is input at one end and the other end is connected to the inverting input terminal 262a, and a resistor 273 to which the bias signal VS is input at one end and the other end is connected to the inverting input terminal 262b. The resistor 271 is an example of a third resistor, the resistor 272 is an example of a fourth resistor, and the resistor 273 is an example of a fifth resistor.

[0103] The amplifier circuit 260 further includes a switch SW2a for switching whether the resistor element 268 is electrically connected to the output terminal 262c and the inverting input terminal 262a. The amplifier circuit 260 includes a switch SW2b for switching whether the resistor element 272 is electrically connected to the inverting input terminal 262a. The amplifier circuit 260 includes a switch SW2c for switching whether the resistor element 273 is electrically connected to the inverting input terminal.

[0104] The amplifier circuit 260 may further include a switch SW1 a that switches whether the resistor 271 is electrically connected to the inverting input terminal 262 a and a switch SW1 b that switches whether the resistor 266 is electrically connected between the output terminal 262 c and the inverting input terminal 262 a .

[0105] The control circuit 300 includes an adjustment circuit 320 , a comparator 330 , and a selection circuit 340 in order to switch the amplification factor of the amplifier circuit 260 by controlling each switch SW and controlling the input of the bias signal VS.

[0106] The comparator 330 is a circuit for performing threshold determination. When the amplitude of the output signal VOUT is not included in the predetermined amplitude range W, the comparator 330 operates the switches SW2a, SW2b, and SW2c, electrically connects the resistor element 268 between the output terminal 262c and the inverting input terminal 262a, electrically connects the resistor element 272 to the inverting input terminal 262a, and outputs the working signal DET and the polarity signal DET_POL. The working signal DET indicates a command to electrically connect the resistor element 273 to the inverting input terminal 262a. The polarity signal DET_POL indicates whether the amplitude of the output signal VOUT exceeds the upper limit value VH of the predetermined amplitude range W or is less than the lower limit value VL of the predetermined amplitude range W. The comparator 330 outputs the working signal DET and the polarity signal DET_POL by comparing the first threshold signal HV of the third potential and the second threshold signal HL of the fourth potential with the output signal VOUT. The first threshold signal HV represents the upper limit value VH (VH=VREF+X) of the predetermined amplitude range W obtained by adding the threshold potential X to the reference potential VREF. The second threshold signal HL represents the lower limit value VL (VL=VREF-X) of the predetermined amplitude range W obtained by subtracting the threshold potential X from the reference potential VREF.

[0107] Based on the operation signal DET and the polarity signal DET_POL, the selection circuit 340 inputs the first bias signal VHX of the first potential as the bias signal VS to one end of the resistor element 273 when the amplitude of the output signal VOUT exceeds the upper limit value VH of the predetermined amplitude range W. When the amplitude of the output signal VOUT is less than the lower limit value VL of the predetermined amplitude range W, the selection circuit 340 inputs the second bias signal VLX of the second potential lower than the first potential as the bias signal VS to one end of the resistor element 273.

[0108] The adjustment circuit 320 adjusts the bias signal VS added to the detection signal VIN. The adjustment circuit 320 inputs a first bias signal VHX, which is a first potential VHX (VHX=VREF+X / G) obtained by adding an adjustment potential X / G based on the threshold potential X to the reference potential VREF, and a second bias signal VLX, which is a second potential VLX (VLX=VREF-X / G) obtained by subtracting the adjustment potential X / G from the reference potential VREF, to the selection circuit 340. The selection circuit 340 determines whether the amplitude of the output signal VOUT exceeds the upper limit value HV of the predetermined amplitude range W or is less than the lower limit value VL based on the operation signal DET and the polarity signal DET_POL, and outputs one of the first bias signal VHX and the second bias signal VLX input from the adjustment circuit 320 according to the determination result.

[0109] With the above configuration, the current sensor 200 can expand the measurable current range while suppressing the fluctuation in the amplitude of the output signal VOUT output from the amplifier 250 that is caused by switching the gain.

[0110] The magnetic sensor 220 detects the magnetic field generated by the measurement current flowing through the conductor 210, and inputs a signal having a current value or a voltage value corresponding to the magnetic field as a detection signal VIN to the amplifier 250. The detection signal VIN is input to the inverting input terminal 262a, which is an input terminal of the negative feedback circuit composed of the operational amplifier 262, via the resistor element 271 and the switch SW1a. The output terminal 262c of the operational amplifier 262 is connected to the inverting input terminal 262a via the resistor element 266 and the switch SW1b.

[0111] In the current sensor 200 according to the first embodiment, the switch SW1a and the switch SW1b are always in the on state. However, the current sensor 200 may include a plurality of combinations of the switch SW1a, the switch SW1b, the resistor element 271, and the resistor element 266. In this case, Figure 4 As shown, the current sensor 200 may have Figure 1 The control circuit 300 may have a function of controlling the plurality of switches SW1 from the correction unit 290 to adjust the gain (R3 / R1) serving as a reference.

[0112] The output terminal 262c of the operational amplifier 262 is further connected to the inverting input terminal 262a via the resistor 268 and the switch SW2a. The initial setting of the switch SW2a is the off state. The initial setting of the switch SW2b and the switch SW2c is also the off state.

[0113] A reference potential VREF of the output signal VOUT is applied to the non-inverting input terminal 262 b of the operational amplifier 262 and the other end of the resistor 272 opposite to the end connected to the switch SW2 b .

[0114] In the first embodiment, the output signal VOUT is also input as a signal for threshold determination to the comparator 330. The comparator 330 may be a general window comparator circuit. The comparator 330 receives VH=VREF+X as a positive determination value and VL=VREF-X as a negative determination value.

[0115] Although not shown in the figure, for the comparator 330, the determination value may also be input via an attenuator or a filter with specific frequency band limitation. In the case of using an attenuator, VH and VL of the determination value can be set to arbitrary values. VH and VL are also input to the adjustment circuit 320. The adjustment circuit 320 makes ±X for threshold determination become 1 / G, and outputs VHX = VREF + X / G and VLX = VREF - X / G to the selection circuit 340. The comparator 330 inputs the DET signal to the selection circuit 340, as well as the switch SW2a, the switch SW2b, and the switch SW2c.

[0116] The DET signal is Lo when VL < VOUT < VH, and the switches SW2a, SW2b, and SW2c are in the off state.

[0117] The DET signal becomes Hi when VH < VOUT or VL > VOUT, and the switches SW2a, SW2b, and SW2c are in the on state. In addition, the DET_POL signal, which is the output of the comparator 330, is input to the selection circuit 340.

[0118] When VH < VOUT, the DET_POL signal becomes Hi, and when VL > VOUT, the DET_POL signal becomes Lo. By combining the determination using the DET_POL signal and the DET signal, when exceeding the positive threshold VH, the selection circuit 340 outputs the first bias signal VHX as the bias signal VS. On the other hand, when less than the negative threshold VL, the selection circuit 340 outputs the second bias signal VLX as the bias signal VS. The bias signal VS is input to the inverting input terminal 262a of the operational amplifier 262 via the resistor element 273 and the switch SW2c.

[0119] For the selection circuit 340, although the voltages obtained by adjusting the determination values VH and VL used in the threshold determination of the comparator 330 are input, either voltages having a correlation with the thresholds VH and VL or voltages having no correlation can be input, and it can be appropriately selected.

[0120] When the switches SW1a and SW1b are on and the switches SW2a, SW2b, and SW2c are off, the output signal VOUT becomes the following equation.

[0121] VOUT = (1 + R3 / R1) × VREF - R3 / R1 × VIN…(1)

[0122] Here, when R2 = 2 × R1 and R3 = 4 × R1, the equation (1) becomes the following equation.

[0123] VOUT=5×VREF-4×VIN…(2)

[0124] When the switches SW1a and SW1b are on and the switches SW2a, SW2b, and SW2c are on, the output signal VOUT is expressed by the following equation.

[0125] VOUT=(1+R3 / (2×R2)+R3 / (2×R1))×VREF-R3 / (2×R1)×VIN-R3 / (2×R2)×VS…(3)

[0126] Here, when R2=2×R1 and R3=4×R1, equation (3) becomes the following equation.

[0127] VOUT=4×VREF-2×VIN-VS…(4)

[0128] According to equations (2) and (4), the coefficient of the detection signal VIN when the switches SW2a, SW2b, and SW2c are off is -4. On the other hand, the coefficient of VIN when the switches SW2a, SW2b, and SW2c are on is -2. This is equivalent to the fact that the amplification factor from the detection signal VIN to the output signal VOUT is reduced by the comparator 330 performing threshold determination on the output signal VOUT and the switches SW2a, SW2b, and SW2c switching from off to on.

[0129] Here, when the switches SW2a, SW2b, and SW2c change from off to on, the bias signal VS for not changing the output signal VOUT is when VOUT in equation (2) and VOUT in equation (4) have the same value. That is, it satisfies the following equation (5).

[0130] 5×VREF-4×VIN=4×VREF-2×VIN-VS…(5)

[0131] According to equation (5), the bias signal VS for keeping the output signal VOUT unchanged is expressed by equation (6).

[0132] VS=-VREF+2×VIN…(6)

[0133] Figure 5A and Figure 5B An example of the output characteristic of the output signal VOUT with respect to the detection signal VIN is shown. Here, as in the following formula, Vh is used as a variable of the measurement current to express the output characteristic of the output signal VOUT. Here, Vh is a positive real number.

[0134] The detection signal VIN is expressed as in the following equation using the output signal Vh output from the magnetic sensor 220 and the reference potential VREF.

[0135] VIN=±Vh+VREF…(7)

[0136] By substituting equation (7) into equation (6), the bias signal VS becomes the following equation (8).

[0137] VS=VREF±2×Vh…(8)

[0138] When switches SW1a and SW1b are turned on and switches SW2a, SW2b, and SW2c are turned off, if equation (7) is substituted into equation (2), the output signal VOUT becomes the following equation: VOUT = 5 × VREF - 4 × VIN

[0139] = VREF-4×(±Vh)…(9)

[0140] When switches SW1a and SW1b are on and switches SW2a, SW2b, and SW2c are on, if equations (7) and (8) are substituted into equation (4), the output signal VOUT becomes the following equation: Wherein VS is a bias voltage (fixed value).

[0141] VOUT=4×VREF-2×VIN-VS

[0142] =(VREF-2×(±Vh))-2×(±Vh)…(10)

[0143] Figure 5A and Figure 5B The graph shown is a graph showing the output characteristics of the output signal VOUT when the adjustment value G in the adjustment circuit 320 is set to G=2 and H=VREF+4×Vh, VL=VREF-4×Vh, VHX=VREF+2×Vh, and VLX=VREF-2×Vh.

[0144] Figure 5A The coordinate diagram 400 is a synthesis of the separate coordinate diagrams of equation (9) and equation (10). Figure 5B The coordinate graph 401 is a coordinate graph showing the output characteristics of the output signal VOUT when the switches SW2a, SW2b and SW2c are turned from on to off when the output signal VOUT is not included in the predetermined amplitude range W of VREF-4×Vh to VREF+4×Vh.

[0145] As above, according to Figure 3The current sensor 200 of the circuit structure shown can change the amplification factor from the detection signal VIN to the output signal VOUT in a decreasing manner when the output signal VOUT is not included in the predetermined amplitude range W. In addition, it can maintain accuracy in the range where the measured current is small, i.e., |±Vh|>VIN, and can suppress the output voltage in |±Vh|<VIN, enabling a wide range.

[0146] Here, consider the negative feedback loop, i.e., the feedback ratio β, of the amplifier circuit 260. Fig. 6A and Figure 6B is Figure 3 the block diagram in the operational amplifier 262.

[0147] When the switches SW1a and SW1b are ON and the switches SW2a, SW2b, and SW2c are OFF, the voltage VA at the inverting input terminal 262a. The current input to the inverting input terminal 262a can be expressed as (VIN - VA) / R1 when observed from the input side and (VA - VOUT) / R3 when observed from the output side. Since (VIN - VA) / R1 and (VA - VOUT) / R3 take the same value, the following equation is satisfied.

[0148] (VIN - VA) / R1 = (VREF - VA) / R3…(11)

[0149] If Equation (11) is expanded with respect to VA, VA can be expressed by the following Equation (12).

[0150] VA = (R1 / (R1 + R3))×VOUT + (R3 / (R1 + R3))×VIN…(12)

[0151] Thus, when the switches SW1a and SW1b are ON and the switches SW2a, SW2b, and SW2c are OFF, it can be represented by the Fig. 6A block diagram shown, and the feedback ratio β1 can be expressed by the following Equation (13).

[0152] β1 = 1 / (1 + R3 / R1)…(13)

[0153] On the other hand, when the switches SW1a and SW1b are ON and the switches SW2a, SW2b, and SW2c are ON, the current input to the inverting input terminal 262a can be expressed as (VIN - VA) / R1 + (VREF - VA) / R2 + (VS - VA) / R2 when observed from the input side and (VA - VOUT) / (R3 / 2) when observed from the output side.

[0154] Since (VIN-VA) / R1+(VREF-VA) / R2+(VS-VA) / R2 and (VREF-VOUT) / (R3 / 2) have the same value, the following equation (14) is satisfied.

[0155] (VIN-VA) / R1+(VREF-VA) / R2+(VS-VA) / R2=(VA-VOUT) / (R3 / 2)

[0156] …(14)

[0157] If equation (14) is expanded by VA, VA can be expressed by the following equation (15).

[0158] VA=VOUT / (1+R3 / (2×R1)+R3 / R2)+VIN / (1+2×R1 / R3+2×R1 / R2)+VREF / (2+R2 / R1+2×R2 / R3+)+VS / (2+R2 / R1+2×R2 / R3)…(15)

[0159] Thus, when the switches SW1a and SW1b are turned on and the switches SW2a, SW2b, and SW2c are turned on, the Figure 6B The block diagram shown shows that the feedback ratio β2 can be expressed by the following equation (16).

[0160] β2=1 / (1+R3 / (2×R1)+R3 / R2)…(16)

[0161] Here, since R2 = 2×R1 and R3 = 4×R1, β1 = β2 = 1 / 5.

[0162] That is, according to Figure 3 The structure of the current sensor 200 shown can suppress the variation of the feedback ratio of the amplifier circuit 260 at the time of switching the amplification factor.

[0163] Figure 7 It is a diagram showing Figure 3 An example of a Bode diagram showing the relationship between F0 and the feedback ratio β when the finite gain A0 of the operational amplifier 262 has a first-order LPF characteristic.

[0164] Generally, when the input signal is amplified using the operational amplifier 262, the feedback ratio β < 1. Since the open loop gain formed by the feedback loop is A0×β, it can be seen that the gain is smaller than before the feedback loop is formed, F0 is also smaller, and the frequency responsiveness is lowered.

[0165] according to Figure 3The structure of the current sensor 200 shown, when R2 = 2×R1 and R3 = 4×R1 are set, regardless of the on and off states of the switches SW2a, SW2b, and SW2c, the feedback ratios β1 = β2. That is, it means that the open-loop gain remains unchanged, and it can be known that the frequency response also remains unchanged. By selecting the circuit structure and constants as described above, when the magnification from the detection signal VIN to the output signal VOUT changes in a decreasing manner, the feedback ratio β can be controlled without change. When the magnification is simply reduced in |±Vh| < VIN, the feedback ratio β becomes β1 < β2 < 1, but in the state transition from β1 to β2, if the change rate of the feedback ratio is large, when there is a transitional current response from a small current to a large current, since it becomes a cause of distortion, the change rate of the feedback ratio is preferably small.

[0166] Figure 8 FIG. is an example showing the circuit structure of the current sensor 700 according to the second embodiment. Similar to Figure 2 the current sensor 700 detects the measurement current flowing in the conductor 210. Figure 8 The current sensor 700 has the same function as Figure 2 the current sensor 200, so only the different functions will be described.

[0167] The amplification unit 750 is connected to the output unit 280. As an example, it can be structured as an inverting amplification circuit or a non-inverting amplification circuit using an operational amplifier. The amplification unit 750 can amplify the amplitude of the signal by a predetermined gain and output it. The amplification unit 750 is branched and connected with the output of the magnetic sensor 220 as the detection signal VIN, determines the input result through a predetermined threshold value, and controls it in a manner smaller than the predetermined gain. Also, similar to the current sensor 200 according to the first embodiment, multiple threshold values can be prepared.

[0168] Different from the current sensor 200, the current sensor 700 determines the threshold value with the detection signal VIN, and is suitable for applications that can detect transitional high currents faster.

[0169] Fig. 9 FIG. shows an example of the circuit structure of the amplification unit 750 using an inverting amplification circuit. The amplification unit 750 has the same as Figure 3Since the amplifier 250 has the same functions as the amplifier 250, only the different functions will be described. In the amplifier 750, the detection signal VIN is input as the input signal of the comparator 330 instead of the output signal VOUT. The comparator 330 can also use the structure of a general window comparator circuit, with VH=VREF+X as the judgment value input on the positive side and VL=VREF-X as the judgment value input on the negative side. When the adjustment value G of the adjustment circuit 320 is set to G=0.5, VH=VREF+Vh, VL=VREF-Vh, VHX=VREF+2×Vh, VLX=VREF-2×Vh can be set, and the output characteristics from the detection signal VIN to the output signal VOUT are the same as Figure 5A and Figure 5B same.

[0170] As described above, according to the current sensor 200 according to the first embodiment and the current sensor 700 according to the second embodiment, it is possible to expand the measurable current range while suppressing the fluctuation in the amplitude of the signal output from the amplifier circuit due to switching of the gain. Such technical effects can be achieved, for example, as shown in the above-mentioned embodiment, by the following structure: a current sensor including: a detection unit that outputs a detection signal corresponding to a magnetic field generated around a conductor due to the flow of a measurement current (for example, a signal generated by a Hall element receiving the magnetic field); and an amplifier circuit (for example, an operational amplifier or a comparator) having a first input terminal (for example, an inverting input terminal of the operational amplifier), a second input terminal (for example, a non-inverting input terminal of the operational amplifier), and an output terminal, amplifying the detection signal input via the first input terminal and outputting the output signal via the output terminal, wherein the amplifier circuit is configured to be able to switch between at least a first amplification factor and a second amplification factor lower than the first amplification factor, and the current sensor includes a control circuit (for example, the control circuit 300 in the embodiment) capable of inputting a bias signal (VS) to the first input terminal, and the control circuit is configured to stop inputting the bias signal to the first input terminal (disconnect the input) during a period (a first start period) in which the first amplification factor is set, and to input the bias signal to the first input terminal (disconnect the input) during a period (a second start period) in which the second amplification factor is set.

[0171] The input and stop (turning on and off) of the bias signal to the first input terminal are controlled by, for example, a switch provided between the control circuit and the amplifier circuit as described in the embodiment. Furthermore, if the amplification factor of the amplifier circuit is set to a first amplification factor (high gain) when the amplitude of the detection signal or the output signal is included in a predetermined amplitude range, and if the amplification factor of the amplifier circuit is set to a second amplification factor (low gain) when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range, the input of the bias signal to the first input terminal suppresses the change in the amplitude of the output signal generated in response to the switching of the amplification factor of the amplifier circuit between the first amplification factor and the second amplification factor.

[0172] Furthermore, since the feedback ratio of the amplifier circuit does not change with the switching of the gain, the change of the frequency responsiveness of the amplifier circuit can also be suppressed. Such a technical effect can be achieved, for example, as shown in the above-mentioned embodiment, by the following structure: the amplifier circuit has an impedance element, one end of which is connected to the first input terminal, and the impedance element is an impedance that suppresses the change of the feedback ratio of the amplifier circuit generated by adding the bias signal to the detection signal, that is, the impedance element functions in a manner that suppresses the change of the feedback ratio of the amplifier circuit generated by adding the bias signal to the detection signal. It should be noted that such an impedance element is typically connected to the resistor element 272 as shown in the above-mentioned embodiment.

[0173] It should be noted that the resistance values ​​of the resistor elements 266, 268, 271, 272, and 273 and the potential applied to the resistor element 272 shown above are examples. Depending on the resistance values ​​of the resistor elements 266, 268, 271, 272, and 273 or the magnitude of the bias signal VS, the potential applied to the resistor element 272 can be adjusted to an arbitrary potential based on the reference potential VREF so that the feedback ratio of the amplifier circuit 260 does not change with the switching of the gain.

[0174] In addition, Fig.10 2 shows a further modification of the current sensor described above. Fig.10Another example of the circuit structure using the inverting amplifier circuit of the amplifier 250 involved in the first embodiment is shown. Since the same function is provided, only the difference from the above-mentioned embodiment is described. The working signal DET as the output of the comparator 330 is connected to INV1010, and the working signal DET_N obtained by inverting the working signal DET is output. The switch SW2d is connected between the non-inverting input terminal 262b as the second input terminal of the operational amplifier 262 and VREF, and SW2d is controlled by the working signal DET_N. The initial state of the switch SW2d (here, the working signal DET_N is set to Hi) is on. SW2e is connected between the non-inverting input terminal 262b and the bias signal VS as the output of the selection circuit 340, and SW2e is controlled by the working signal DET, and the initial state is off (here, the working signal DET is set to Lo). When the amplitude of the output signal VOUT is not within the predetermined amplitude range W, the switch SW2d is turned off (the working signal DET_N is set to Lo), the switch SW2e is turned on (here, the working signal DET is set to Hi), and the non-inverting input terminal 262b is connected from VREF to the bias signal VS.

[0175] Here, the detection signal VIN is switched from the sum of the output signal Vh output from the magnetic sensor 220 and the reference potential VREF to the sum of the output signal Vh and the bias signal VS by connecting the bias signal VS from VREF through the non-inverting input terminal 262b. If the switched detection signal VIN is reset to the detection signal VIN', the detection signal VIN' is expressed as follows.

[0176] VIN'=±Vh+VS…(17)

[0177] When the non-inverting input terminal 262b is connected to the bias signal VS from VREF, switches SW1a and SW1b are on, switches SW2a, SW2b, SW2c, and SW2e are on, and SW2d is off, and the output signal VOUT is expressed by the following equation.

[0178] VOUT=(1+R3 / (2×R2)+R3 / (2×R1))×VS-R3 / (2×R1)×VIN'-R3 / (2×R2)×VREF…(18)

[0179] Here, when the resistor elements are connected so as to satisfy R2=2×R1 and R3=4×R1, the equation (18) becomes the following equation.

[0180] VOUT=4×VS-2×VIN'-VREF…(19)

[0181] Here, at the time when the switches SW2a, SW2b, SW2c, and SW2e are changed from off to on and the switch SW2d is changed from on to off (i.e., the time when the gain of the amplifier circuit 260 is switched), the bias signal VS is set so that VOUT of the equation (2) and VOUT of the equation (19) have the same value, thereby suppressing the variation of the output signal VOUT. That is, the bias signal VS is controlled so as to satisfy the following equation (20).

[0182] 5×VREF-4×VIN=4×VS-2×VIN'-VREF…(20)

[0183] By substituting equations (7) and (17) into equation (20), the bias signal VS becomes the following equation (21).

[0184] VS=VREF-(±Vh)…(21)

[0185] By further substituting equation (17) and equation (21) into equation (19), the output signal VOUT becomes the following equation (22). It should be noted that VS is a bias signal and is a fixed value.

[0186] VOUT=(VREF-2×(±Vh))-2×(±Vh)…(22)

[0187] Here, it can be seen that equation (10) and equation (22) are the same equation. Therefore, Fig.10 Although it is Figure 3 Different connection methods, but can get the same result, so about Figure 5A and Figure 5B The output characteristics of the output signal VOUT with respect to the detection signal VIN shown are also the same.

[0188] However, based on Fig.10 The embodiment shown is derived Figure 5A and Figure 5B In the case of the input-output coordinate diagram shown, the adjustment value G in the adjustment circuit 320 is set to G=4, and VH=VREF+4×Vh, VL=VREF-4×Vh, VHX=VREF+Vh, VLX=VREF-Vh to show the output characteristics of the output signal VOUT.

[0189] The present invention has been described above using the embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments. It is obvious from the description of the claims that the modes after such changes or improvements are also included in the technical scope of the present invention.

[0190] It should be noted that the execution order of each process such as actions, processes, steps and stages in the device, system, program and method shown in the claims, specifications and drawings can be implemented in any order as long as it is not specifically stated as "before", "before", etc. and the output of the previous process is not used in the subsequent process. Even if the action flow in the claims, specifications and drawings is described using "first", "next", etc. for convenience, it does not necessarily mean that it must be implemented in this order.

Claims

1. A current sensor comprising: a detection unit that outputs a detection signal corresponding to a magnetic field generated in the conductor due to the flow of the measurement current; an amplifier circuit having a first input terminal, a second input terminal, and an output terminal, amplifying the detection signal input via the first input terminal and outputting an output signal via the output terminal; and A control circuit capable of inputting a bias signal to the first input terminal, The amplifier circuit is configured to be capable of switching between at least a first amplification factor and a second amplification factor lower than the first amplification factor. The control circuit stops input of the bias signal to the first input terminal while the first amplification factor is set, and inputs the bias signal to the first input terminal while the second amplification factor is set.

2. The current sensor according to claim 1, wherein: When the amplitude of the detection signal or the output signal is within a predetermined amplitude range, the control circuit sets the amplification factor of the amplifier circuit to the first amplification factor, and when the amplitude of the detection signal or the output signal is not within the predetermined amplitude range, the control circuit sets the amplification factor of the amplifier circuit to the second amplification factor. Input of the bias signal to the first input terminal suppresses a change in the amplitude of the output signal caused by switching the amplification factor of the amplifier circuit between the first amplification factor and the second amplification factor.

3. The current sensor according to claim 2, wherein: The amplifier circuit includes an impedance element, one end of which is connected to the first input terminal. The impedance element is an impedance that suppresses a change in a feedback ratio of the amplifier circuit that is generated by adding the bias signal to the detection signal.

4. The current sensor according to claim 3, wherein: A reference potential is applied to the second input terminal, and a potential based on the reference potential is applied to the other end of the impedance element.

5. The current sensor according to claim 2, wherein: The amplifier circuit includes a feedback resistor circuit connected between the output terminal and the first input terminal, the feedback resistor circuit being set to a first resistance value in the case of the first amplification factor, and being set to a second resistance value lower than the first resistance value in the case of the second amplification factor. When the amplitude of the detection signal or the output signal is within the predetermined amplitude range, the control circuit sets the resistance value of the feedback resistor circuit to the first resistance value. When the amplitude of the detection signal or the output signal is not within the predetermined amplitude range, the control circuit sets the resistance value of the feedback resistor circuit to the second resistance value.

6. The current sensor according to claim 5, wherein: The feedback resistor circuit comprises: A first resistor element connected between the output terminal and the first input terminal; and a second resistance element connected between the output terminal and the first input terminal in parallel with the first resistance element; When the amplitude of the detection signal or the output signal is within the predetermined amplitude range, the control circuit controls the feedback resistance circuit in such a manner that the first resistance element is electrically connected between the output terminal and the first input terminal and the second resistance element is not electrically connected between the output terminal and the first input terminal. When the amplitude of the detection signal or the output signal is not within the predetermined amplitude range, the control circuit controls the feedback resistance circuit so as to electrically connect the first resistance element and the second resistance element between the output terminal and the first input terminal.

7. The current sensor according to claim 2, wherein: When the amplitude of the detection signal or the output signal exceeds the upper limit of the predetermined amplitude range, the control circuit adds a first bias signal of a first potential as the bias signal to the detection signal. When the amplitude of the detection signal or the output signal is smaller than a lower limit value of the predetermined amplitude range, the control circuit adds a second bias signal having a second potential lower than the first potential to the detection signal as the bias signal.

8. The current sensor according to claim 6, wherein: The amplifier circuit has: a third resistor element, one end of which is input with the detection signal, and the other end of which is connected to the first input terminal; a fourth resistor element, one end of which is applied with a reference potential, and the other end of which is connected to the first input terminal; a fifth resistor element, one end of which is input with the bias signal, and the other end of which is connected to the first input terminal; a first switch for switching whether to electrically connect the second resistor element between the output terminal and the first input terminal; a second switch for switching whether to electrically connect the fourth resistor element to the first input terminal; and a third switch for switching whether to electrically connect the fifth resistor element to the first input terminal; The control circuit has: a comparator that, when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range, operates the first switch, the second switch, and the third switch, electrically connects the second resistor element between the output terminal and the first input terminal, electrically connects the fourth resistor element to the first input terminal, and outputs an operation signal and a polarity signal, wherein the operation signal electrically connects the fifth resistor element to the first input terminal, and the polarity signal indicates whether the amplitude of the detection signal or the output signal exceeds an upper limit value of the predetermined amplitude range or is less than a lower limit value of the predetermined amplitude range; and The selection circuit, based on the working signal and the polarity signal, inputs a first bias signal of a first potential as the bias signal to the one end of the fifth resistor element when the amplitude of the detection signal or the output signal exceeds the upper limit value of the predetermined amplitude range, and inputs a second bias signal of a second potential lower than the first potential as the bias signal to the one end of the fifth resistor element when the amplitude of the detection signal or the output signal is less than the lower limit value of the predetermined amplitude range.

9. The current sensor according to claim 8, wherein: The comparator controls the output of the working signal and the polarity signal by comparing a first threshold signal of a third potential and a second threshold signal of a fourth potential with the detection signal or the output signal, wherein the third potential represents an upper limit value of the predetermined amplitude range obtained by adding a threshold potential to the reference potential, and the fourth potential represents a lower limit value of the predetermined amplitude range obtained by subtracting the threshold potential from the reference potential, The control circuit also has an adjustment circuit that inputs the first bias signal of the first potential and the second bias signal of the second potential to the selection circuit, wherein the first potential is obtained by adding an adjustment potential based on the threshold potential to the reference potential, and the second potential is obtained by subtracting the adjustment potential from the reference potential.

10. The current sensor according to claim 8, wherein: The resistance values ​​of the fourth resistor and the fifth resistor are twice the resistance value of the third resistor. The resistance values ​​of the first resistance element and the second resistance element are four times the resistance value of the third resistance element.

11. The current sensor according to claim 2, wherein: The detection unit includes at least one magnetic sensor.

12. The current sensor according to claim 11, wherein: The at least one magnetic sensor is a Hall element, a magnetoresistive element (MR), a giant magnetoresistive element (GMR), a tunnel magnetoresistive element (TMR), a magneto-impedance element (MI element), or an inductive sensor.

13. A current sensor comprising: a detection unit that outputs a detection signal corresponding to a magnetic field generated in the conductor due to the flow of the measurement current; an amplifier circuit having a first input terminal, a second input terminal, and an output terminal, amplifying the detection signal input via the first input terminal and outputting an output signal via the output terminal; and A control circuit capable of inputting a bias signal to the first input terminal and the second input terminal, The amplifier circuit is configured to be capable of switching between at least a first amplification factor and a second amplification factor lower than the first amplification factor. The control circuit inputs the bias signal to the first input terminal while the second amplification factor is set, and stops input of the bias signal to the first input terminal while the first amplification factor is set.

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