Current sensor

Abstract

SOLUTION: A current sensor may include a detection unit which outputs a detection signal corresponding to a magnetic field generated around a conductor by a flow of a measurement current therein; an amplification circuit, including a first input terminal, a second input terminal, and an output terminal, which amplifies the detection signal input via the first input terminal and outputs an output signal via the output terminal; and a control circuit which is capable of inputting an offset signal to the first input terminal. The amplification circuit may be configured to be capable of switching at least a first amplification factor and a second amplification factor, lower than the first amplification factor, and the control circuit may turn off the input of the offset signal to the first input terminal during a period in which the first amplification factor is set, and input the offset signal to the first input terminal during a period in which the second amplification factor is set.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 discloses a current sensor having a gain that cancels out changes in detection gain in at least a portion of the gain fluctuation band. Patent Document 2 discloses A / D conversion in which a gain switching circuit alternately switches between large and small input ranges while reading digital values ​​at oversampling frequencies higher than conventional sampling frequencies. Patent Document 3 discloses an amplifier that can automatically switch gain according to input voltage. Patent Document 4 discloses making the amplification factor of an operational amplifier variable based on the output voltage of a current detector. [Prior art document] [Patent documents] [Patent Document 1] JP 2020-038196 A [Patent Document 2] JP 2019-152471 A [Patent Document 3] JP 2004-336300 A [Patent Document 4] JP 2010-197065 A Summary of the Invention [Problem to be solved by the invention]

[0003] There is a demand for a current sensor that can measure a wide range of currents while suppressing fluctuations in the amplitude of the output signal output from the amplifier that occur when the gain is switched. [Means for solving the problem]

[0004] A current sensor according to an aspect of the present invention may include a detection unit that outputs a detection signal corresponding to a magnetic field generated in a conductor by a measurement current flowing therethrough. 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 capable of inputting an offset signal to the first input terminal. The amplifier circuit may be configured to be switchable between at least a first amplification factor and a second amplification factor lower than the first amplification factor. The control circuit may stop inputting the offset signal to the first input terminal during a period in which the first amplification factor is set, and may input the offset signal to the first input terminal during a period in which the second amplification factor is set.

[0005] 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 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 when the offset signal is input to the first input terminal.

[0006] In the current sensor, the amplifier circuit may have an impedance element having one end connected to the first input terminal, and the impedance element may be an impedance that suppresses a change in the feedback ratio of the amplifier circuit caused by adding the offset signal to the detection signal.

[0007] 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.

[0008] In any of the current sensors, the amplifier circuit may have 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 when the first amplification factor is used and to a second resistance value lower than the first resistance value when the second amplification factor is used. 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 within the predetermined amplitude range, and 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 within the predetermined amplitude range.

[0009] 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 in parallel with the first resistance element between the output terminal and the first input terminal.

[0010] The control circuit may control the feedback resistance circuit so that, when the amplitude of the detection signal or the output signal is within the predetermined amplitude range, 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 within the predetermined amplitude range, the control circuit may control the feedback resistance circuit so that the first resistance element and the second resistance element are electrically connected between the output terminal and the first input terminal.

[0011] In any of the current sensors, the control circuit may add a first offset signal of a first potential to the detection signal as the offset signal when the amplitude of the detection signal or the output signal exceeds an upper limit of the predetermined amplitude range, and add a second offset signal of a second potential lower than the first potential to the detection signal as the offset signal when the amplitude of the detection signal or the output signal falls below a lower limit of the predetermined amplitude range.

[0012] In any of the current sensors, the amplifier circuit may include a third resistive element having one end to which the detection signal is input and the other end connected to the first input terminal, a fourth resistive element having one end to which a reference potential is applied and the other end connected to the first input terminal, a fifth resistive element having one end to which the offset signal is input and the other end connected to the first input terminal, a first switch that switches whether or not the second resistive element is electrically connected between the output terminal and the first input terminal, a second switch that switches whether or not the fourth resistive element is electrically connected to the first input terminal, and a third switch that switches whether or not the fifth resistive element is electrically connected to the first input terminal. The control circuit may include a comparator that outputs an actuation signal for actuating the first switch, the second switch, and the third switch to electrically connect the second resistive element between the output terminal and the first input terminal, electrically connect the fourth resistive element to the first input terminal, and electrically connect the fifth resistive element to the first input terminal when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range, and a polarity signal indicating whether the amplitude of the detection signal or the output signal exceeds an upper limit value of the predetermined amplitude range or falls below a lower limit value of the predetermined amplitude range. The control circuit may include a selector circuit that, based on the actuation signal and the polarity signal, inputs a first offset signal of a first potential as the offset signal to the one end of the fifth resistive element when the amplitude of the detection signal or the output signal exceeds an upper limit value of the predetermined amplitude range, and inputs a second offset signal of a second potential lower than the first potential as the offset signal to the one end of the fifth resistive element when the amplitude of the detection signal or the output signal falls below the lower limit value of the predetermined amplitude range.

[0013] In any of the current sensors, the comparator may control the output of the actuation signal and the polarity signal by comparing the detection signal or the output signal with a first threshold signal of a third potential indicating an upper limit of the predetermined amplitude range obtained by adding a threshold potential to the reference potential, and a second threshold signal of a fourth potential indicating a 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 to the selector circuit the first offset signal of the first potential obtained by adding an adjustment potential based on the threshold potential to the reference potential, and the second offset signal of the second potential obtained by subtracting the adjustment potential from the reference potential.

[0014] In any one of the current sensors, the fourth resistive element and the fifth resistive element may have a resistance value twice as high as the third resistive element, and the first resistive element and the second resistive element may have a resistance value four times as high as the third resistive element.

[0015] In any of the current sensors, the detection portion may include at least one magnetic sensor.

[0016] In any of the current sensors, the at least one magnetic sensor may be a Hall element, a magnetoresistance element (MR), a giant magnetoresistance element (GMR), a tunneling magnetoresistance element (TMR), a magneto-impedance element (MI element), or an inductance sensor.

[0017] A current sensor according to an aspect of the present invention may include a detection unit that outputs a detection signal corresponding to a magnetic field generated in a conductor by a measurement current flowing therethrough. 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 capable of inputting an offset signal to the first input terminal and the second input terminal. The amplifier circuit may be configured to be switchable between at least a first amplification factor and a second amplification factor lower than the first amplification factor. The control circuit may input the offset signal to the first input terminal during a period in which the second amplification factor is set, and may stop inputting the offset signal to the first input terminal during a period in which the first amplification factor is set.

[0018] The above summary of the invention does not list all of the features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a diagram illustrating an example of a circuit configuration of a current sensor including a correction unit. [Diagram 2] 1 is a diagram illustrating an example of a circuit configuration of a current sensor according to a first embodiment. [Diagram 3] FIG. 13 is a diagram showing an example of a circuit configuration of an amplifier unit when an inverting amplifier circuit is used. [Figure 4] FIG. 4 is a diagram showing a modified example of the circuit configuration of the current sensor according to the first embodiment. [Figure 5A] 1 is a diagram showing an example of an output characteristic of an output signal VOUT relative to a detection signal VIN; [Figure 5B] 1 is a diagram showing an example of an output characteristic of an output signal VOUT relative to a detection signal VIN; [Figure 6A] FIG. 4 is a block diagram of the operational amplifier of FIG. 3 when switches SW2a, SW2b, and SW2c are in an off state. [Figure 6B]FIG. 4 is a block diagram of the operational amplifier of FIG. 3 when switches SW2a, SW2b, and SW2c are in an on state. [Figure 7] FIG. 4 is a diagram showing an example of a Bode plot illustrating the relationship between F0 and a feedback factor β when the operational amplifier in FIG. 3 has a finite amplification factor A0 and a first-order LPF characteristic. [Figure 8] FIG. 11 is a diagram illustrating an example of a circuit configuration of a current sensor according to a second embodiment. [Figure 9] FIG. 13 is a diagram showing an example of a circuit configuration of an amplifier unit when an inverting amplifier circuit is used. [Figure 10] FIG. 13 is a diagram showing a modified example of the circuit configuration of the amplifier section when an inverting amplifier circuit is used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0021] In a current sensor that uses a magnetic sensor to detect the magnetic field generated in a conductor when a current flows, it is possible to expand the measurable current range by using a correction unit composed of a non-volatile memory or a register to correct the offset or adjust the gain of the amplifier unit that amplifies the signal output by the magnetic sensor.

[0022] 1 shows an example of a circuit configuration of a current sensor 100 having the above-mentioned correction unit. The current sensor 100 has a configuration in which the measurement current flowing through the current paths 110a and 110b is detected by two pairs of magnetic sensors 120a and 120b, thereby reducing the influence of the offset magnetic field of disturbance. 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 output from the magnetic sensors 120a and 120b in the 0 degree direction and the 90 degree direction, removes the offset voltage, and outputs the processed signal to the receiving unit 130.

[0023] The receiving unit 130 is connected to the amplifying unit 150a, and is a wiring or a terminal for connecting the signal processed by the chopper circuit 170 to the amplifying unit 150a. The amplifying unit 150a amplifies the signal with a predetermined gain and outputs the signal to the filter unit 140. The filter unit 140 is connected to the amplifying unit 150b, and filters the signal received by the receiving unit 130 so as to reduce the amplitude of the signal within a predetermined frequency range, and outputs the filtered signal.

[0024] The amplifier unit 150b is connected to the output unit 160, and amplifies and outputs the amplitude of the signal by a predetermined gain. The output unit 160 outputs an output signal indicating the measured current in response to the filtered signal received from the amplifier unit 150b.

[0025] The correction section 180 is connected to the amplifier sections 150a and 150b and the filter section 140, corrects the signal, and adjusts the signal of the current value output from the output section 160 to a desired unique value.

[0026] In such a current sensor 100, an initial setting is required in the correction unit 180 every time the gain setting is changed, and the measurable current range cannot be expanded unless the gain setting is changed. Also, even if the gain of the amplifier unit is switched depending on the magnitude of the amplitude of the signal output from the magnetic sensor, the amplitude of the signal output from the amplifier unit may fluctuate due to the gain switching.

[0027] Therefore, there is a demand for a current sensor that can expand the measurable current range while suppressing fluctuations in the amplitude of the signal output from the amplifier that occur when the gain is switched.

[0028] 2 is a diagram showing an example of a circuit configuration of a current sensor 200 according to the first embodiment. The current sensor 200 detects a measurement current flowing through a conductor 210, which is a current path. The current sensor 200 includes a magnetic sensor 220, an amplifier section 250, and an output section 280. The current sensor 200 may be a semiconductor package in which at least one component of the current sensor 200 is disposed on a substrate and covered with a package made of an insulating material such as mold resin or ceramic.

[0029] The current sensor 200 processes a signal output from the magnetic sensor 220 in response to a measurement current flowing through the conductor 210, and outputs an output signal indicating the amount of current, a rising edge, a falling edge, or the like, of the measurement current.

[0030] 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 a measurement current flows. In FIG. 2, the measurement current flows clockwise around the magnetic sensor 220 in a plan view. The cross-sectional shape of the conductor 210 with respect to the direction of the current flow may be a rectangle, a square, a trapezoid, a polygon, a circle, an ellipse, or a combination thereof. When a measurement current flows through the conductor 210, the conductor 210 generates a clockwise magnetic field around the conductor 210 with respect to the direction of the measurement current flow. As a result, the magnetic field is applied to the magnetic sensor 220 in a substantially downward direction.

[0031] The magnetic sensor 220 is disposed 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 magnetoresistance element (MR), a giant magnetoresistance element (GMR), a tunneling magnetoresistance element (TMR), a magnetic impedance 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 by a measurement current flowing therethrough.

[0032] 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 to the amplifier 250 a detection signal having a current value or a voltage value according to the magnetic field.

[0033] The amplifier unit 250 is connected to the output unit 280. The amplifier unit 250 may include an inverting amplifier circuit or a non-inverting amplifier circuit using an operational amplifier. The amplifier unit 250 may amplify the amplitude of the signal by a predetermined gain and output the signal. The amplifier unit 250 feeds back the output signal VOUT, judges the output result based on a predetermined threshold, and controls the output result to be smaller than the predetermined gain. The amplifier unit 250 may also control the gain based on a threshold selected from a plurality of thresholds.

[0034] The output section 280 outputs a sensor output signal VSOUT indicating the magnitude of the measured current in response to the signal received from the amplifier section 250. The output section 280 may be an operational amplifier or a comparator. The amplifier section 250 may control the gain of the amplifier section 250 by feeding back the sensor output signal VSOUT.

[0035] The current sensor 200 according to the first embodiment includes one magnetoelectric conversion element such as a Hall element as the 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 multiple magnetic sensors 220. For example, a pair of magnetic sensors 220 may be arranged to face each other across the conductor 210 in a plan view. The current sensor 200 may amplify a signal after canceling the influence of an externally generated magnetic field based on the multiple magnetoelectric conversion elements and the outputs of the multiple magnetoelectric conversion elements, using an amplifier 250. The current sensor 200 may include a chopper circuit 170, a receiver 130, and a filter 140 shown in FIG. 1.

[0036] 3 shows an example of a circuit configuration of the amplifier section 250 when an inverting amplifier circuit is used. The amplifier section 250 includes an amplifier circuit 260 and a control circuit 300. The amplifier section 250 includes an operational amplifier 262 and a feedback resistor circuit 264.

[0037] 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 an output signal VOUT via the output terminal 262c.

[0038] The control circuit 300 sets the amplification factor of the amplifier circuit 260 to a first amplification factor when the amplitude of the output signal VOUT is within a predetermined amplitude range W, and sets the amplification factor of the amplifier circuit 260 to a second amplification factor lower than the first amplification factor when the amplitude of the output signal VOUT is not within the predetermined amplitude range W. This makes it possible to widen the current range that can be measured by the current sensor 200. However, the amplitude of the output signal VOUT fluctuates at the timing when the amplification factor of the amplifier circuit 260 switches between the first amplification factor and the second amplification factor. When the amplitude of the output signal VOUT fluctuates, the measurement accuracy of the current sensor 200 varies.

[0039] Therefore, the control circuit 300 adds an offset signal VS, which suppresses changes in the amplitude of the output signal VOUT that occur when the amplification factor of the amplifier circuit 260 is switched between the first amplification factor and the second amplification factor, to the detection signal VIN while the amplification factor of the amplifier circuit 260 is set to the second amplification factor, and inputs the added signal to the inverting input terminal 262a.

[0040] 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 a first amplification factor, and is set to a second resistance value lower than the first resistance value in the case of a second amplification factor. The control circuit 300 sets the resistance value of the feedback resistor circuit 264 to the first resistance value when the amplitude of the output signal VOUT is within a predetermined amplitude range W, and sets the resistance value of the feedback resistor circuit 264 to the second resistance value when the amplitude of the output signal VOUT is not within the predetermined amplitude range W.

[0041] The feedback resistor circuit 264 includes a resistor element 266 and a resistor element 268. The resistor element 266 is an example of a first resistor element connected between the output terminal 262c and the inverting input terminal 262a. The resistor element 268 is an example of a second resistor element connected in parallel with the resistor element 266 between the output terminal 262c and the inverting input terminal 262a. The resistance value R2 of the resistor elements 272 and 273 may be twice the resistance value R1 of the resistor element 271 (R2=2×R1). The resistance value R3 of the resistor elements 266 and 268 may be four times the resistance value R1 of the resistor element 271 (R3=4×R1).

[0042] When the amplitude of the output signal VOUT is within a predetermined amplitude range W, the control circuit 300 controls the feedback resistance circuit 264 to electrically connect the resistance element 266 between the output terminal 262c and the inverting input terminal 262a and not electrically connect the resistance element 268 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 resistance circuit 264 to electrically connect the resistance elements 266 and 268 between the output terminal 262c and the inverting input terminal 262a.

[0043] Furthermore, the control circuit 300 adds a first offset signal VHX of a first potential to the detection signal VIN as an offset signal VS when the amplitude of the output signal VOUT exceeds an upper limit value VH of a predetermined amplitude range W. The control circuit 300 adds a second offset signal VLX of a second potential lower than the first potential to the detection signal VIN as an offset signal VS when the amplitude of the output signal VOUT falls below a lower limit value VL of the predetermined amplitude range W.

[0044] Here, if a configuration is adopted in which the offset signal VS is added to the detection signal VIN, the impedance seen from the inverting input terminal 262a of the operational amplifier 262 changes. This affects the feedback factor β of the operational amplifier 262. If the feedback factor β of the operational amplifier 262 changes, the frequency response of the operational amplifier 262 changes.

[0045] Therefore, the amplifier circuit 260 has a resistor element 272 as an impedance element that suppresses a change in the feedback ratio of the amplifier circuit 260 (operational amplifier 262) caused by adding the offset signal VS to the detection signal VIN and has one end connected to the inverting input terminal 262a. The other end of the resistor element 272 may be applied with the reference potential VREF applied to the inverting input terminal 262a.

[0046] The amplifier circuit 260 further includes a resistor element 271 having one end to which the detection signal VIN is input and the other end connected to the inverting input terminal 262a, and a resistor element 273 having one end to which the offset signal VS is input and the other end connected to the inverting input terminal 262b. The resistor element 271 is an example of a third resistor element, the resistor element 272 is an example of a fourth resistor element, and the resistor element 273 is an example of a fifth resistor element.

[0047] The amplifier circuit 260 further includes a switch SW2a that switches whether the resistive element 268 is electrically connected between the output terminal 262c and the inverting input terminal 262a. The amplifier circuit 260 includes a switch SW2b that switches whether the resistive element 272 is electrically connected to the inverting input terminal 262a. The amplifier circuit 260 includes a switch SW2c that switches whether the resistive element 273 is electrically connected to the inverting input terminal 262a.

[0048] The amplifier circuit 260 may further include a switch SW1a that switches whether or not the resistive element 271 is electrically connected to the inverting input terminal 262a, and a switch SW1b that switches whether or not the resistive element 266 is electrically connected between the output terminal 262c and the inverting input terminal 262a.

[0049] The control circuit 300 has an adjustment circuit 320, a comparator 330, and a selector circuit 340 in order to switch the amplification factor of the amplifier circuit 260 by controlling each switch SW and the input of the offset signal VS.

[0050] The comparator 330 is a circuit that performs threshold judgment. 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 to electrically connect the resistive element 268 between the output terminal 262c and the inverting input terminal 262a, electrically connect the resistive element 272 to the inverting input terminal 262a, and output the actuation signal DET and the polarity signal DET_POL. The actuation signal DET indicates a command to electrically connect the resistive 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 falls below the lower limit value VL of the predetermined amplitude range W. The comparator 330 compares the output signal VOUT with a first threshold signal HV of a third potential and a second threshold signal HL of a fourth potential, and outputs the actuation signal DET and the polarity signal DET_POL. The first threshold signal HV indicates an upper limit value VH (VH=VREF+X) of a predetermined amplitude range W obtained by adding a threshold potential X to a reference potential VREF. The second threshold signal HL indicates a 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.

[0051] When the amplitude of the output signal VOUT exceeds an upper limit value VH of a predetermined amplitude range W based on the actuation signal DET and the polarity signal DET_POL, the selector circuit 340 inputs a first offset signal VHX of a first potential as an offset signal VS to one end of the resistor element 273. When the amplitude of the output signal VOUT falls below a lower limit value VL of the predetermined amplitude range W, the selector circuit 340 inputs a second offset signal VLX of a second potential lower than the first potential as an offset signal VS to one end of the resistor element 273.

[0052] The adjustment circuit 320 adjusts an offset signal VS to be added to the detection signal VIN. The adjustment circuit 320 inputs a first offset signal VHX of a first potential VHX (VHX=VREF+X / G) obtained by adding an adjustment potential X / G based on a threshold potential X to a reference potential VREF, and a second offset signal VLX of a second potential VLX (VLX=VREF-X / G) obtained by subtracting the adjustment potential X / G from the reference potential VREF, to the selector circuit 340. The selector circuit 340 determines whether the amplitude of the output signal VOUT exceeds an upper limit value VH or falls below a lower limit value VL of a predetermined amplitude range W based on the operation signal DET and the polarity signal DET_POL, and outputs either the first offset signal VHX or the second offset signal VLX input from the adjustment circuit 320 according to the determination result.

[0053] With the above configuration, the current sensor 200 can expand the measurable current range while suppressing fluctuations in the amplitude of the output signal VOUT output from the amplifier section 250 that occur when the gain is switched.

[0054] The magnetic sensor 220 detects a magnetic field generated by a 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 an inverting input terminal 262a, which is an input terminal of a negative feedback circuit formed by an operational amplifier 262, via a resistive element 271 and a switch SW1a. An output terminal 262c of the operational amplifier 262 is connected to the inverting input terminal 262a via a resistive element 266 and a switch SW1b.

[0055] In the current sensor 200 according to the first embodiment, the switches SW1a and SW1b are configured to be constantly in an ON state. However, the current sensor 200 may include a combination of the switches SW1a, SW1b, the resistor elements 271, and the resistor elements 266. In this case, as shown in FIG. 4, the current sensor 200 may include a correction unit 290 similar to the correction unit 180 in FIG. 1. The control circuit 300 may have a function of controlling the multiple switches SW1 from the correction unit 290 and adjusting the reference gain (R3 / R1).

[0056] The output terminal 262c of the operational amplifier 262 is further connected to the inverting input terminal 262a via the resistor element 268 and the switch SW2a. The switch SW2a is initially set to the OFF state. The switches SW2b and SW2c are also initially set to the OFF state.

[0057] The reference potential VREF of the output signal VOUT is applied to the non-inverting input terminal 262b of the operational amplifier 262 and the other end of the resistor element 272 opposite to the end to which the switch SW2b is connected.

[0058] Also, in the first embodiment, the output signal VOUT is input to the comparator 330 as a signal for threshold determination. The comparator 330 may be a general window comparator circuit. The values VH = VREF + X and VL = VREF - X are input to the comparator 330 as the positive-side determination value and the negative-side determination value, respectively.

[0059] Although not shown in the figure, the determination values may be input to the comparator 330 via an attenuator or a filter with specific band limitation. When an attenuator is used, VH and VL of the determination values may be arbitrary values. VH and VL are also input to the adjustment circuit 320. The adjustment circuit 320 divides ±X used for threshold determination by 1 / G and outputs VHX = VREF + X / G and VLX = VREF - X / G to the selector circuit 340. The comparator 330 inputs the DET signal to the selector circuit 340, the switch SW2a, the switch SW2b, and the switch SW2c.

[0060] The DET signal is Lo when VL < VOUT < VH, and the switches SW2a, SW2b, and SW2c are in the OFF state.

[0061] The DET signal becomes Hi when VH < VOUT or VL > VOUT, and the switches SW2a, SW2b, and SW2c are in the ON state. Also, the DET_POL signal, which is the output of the comparator 330, is input to the selector circuit 340.

[0062] When VH < VOUT, the DET_POL signal goes Hi, and when VL > VOUT, the DET_POL signal goes Lo. By combining and judging the DET_POL signal and the DET signal, when exceeding the positive threshold VH, the selector circuit 340 outputs the first offset signal VHX as the offset signal VS. On the other hand, when falling below the negative threshold VL, the selector circuit 340 outputs the second offset signal VLX as the offset signal VS. The offset signal VS is input to the inverting input terminal 262a of the operational amplifier 262 via the resistor element 273 and the switch SW2c.

[0063] Voltages obtained by adjusting the determination values VH and VL used for determining the threshold of the comparator 330 are input to the selector circuit 340, but voltages having a correlation with the thresholds VH and VL may be input, voltages having no correlation may be input, and they may be appropriately selected.

[0064] When the switches SW1a and SW1b are ON and the switches SW2a, SW2b, and SW2c are OFF, the output signal VOUT is given by the following equation. VOUT=(1 + R3 / R1)×VREF - R3 / R1×VIN ··· (1)

[0065] Here, when R2 = 2×R1 and R3 = 4×R1, equation (1) becomes the following equation. VOUT = 5×VREF - 4×VIN ··· (2)

[0066] When the switches SW1a and SW1b are ON and the switches SW2a, SW2b, and SW2c are ON, the output signal VOUT is given by the following equation. VOUT=(1 + R3 / (2×R2)+R3 / (2×R1))×VREF - R3 / (2×R1)×VIN - R3 / (2×R2)×VS ··· (3)

[0067] Here, when R2 = 2×R1 and R3 = 4×R1, equation (3) becomes the following equation. VOUT = 4×VREF - 2×VIN - VS ··· (4)

[0068] From 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 corresponds to the output signal VOUT being threshold-judged by the comparator 330, and the switches SW2a, SW2b, and SW2c switching from OFF to ON, thereby reducing the amplification factor from the detection signal VIN to the output signal VOUT.

[0069] Here, the offset signal VS for preventing the output signal VOUT from changing at the timing when the switches SW2a, SW2b, and SW2c change from OFF to ON is when VOUT in equation (2) and VOUT in equation (4) have the same value, i.e., when the following equation (5) is satisfied. 5×VREF-4×VIN=4×VREF-2×VIN-VS...(5)

[0070] From equation (5), the offset signal VS for preventing the output signal VOUT from changing is given by equation (6). VS = -VREF + 2 × VIN (6)

[0071] 5A and 5B show an example of the output characteristic of the output signal VOUT with respect to the detection signal VIN. Here, the output characteristic of the output signal VOUT is shown as follows, with Vh being a variable of the measured current, as shown in the following equation. Here, Vh is a positive real number.

[0072] The detection signal VIN is expressed by the following equation using the output signal Vh output from the magnetic sensor 220 and the reference potential VREF. VIN = ±Vh + VREF (7)

[0073] By substituting equation (7) into equation (6), the offset signal VS is given by the following equation (8). VS = VREF ±2 × Vh (8)

[0074] When switches SW1a and SW1b are ON and switches SW2a, SW2b, and SW2c are OFF, the output signal VOUT, when substituting Equation (7) into Equation (2), becomes the following equation. VOUT = 5 × VREF - 4 × VIN = VREF - 4 × (±Vh) ··· (9)

[0075] When switches SW1a and SW1b are ON and switches SW2a, SW2b, and SW2c are ON, the output signal VOUT, when substituting Equation (7) and Equation (8) into Equation (4), becomes the following equation. Here, VS is an offset voltage (fixed value). VOUT = 4 × VREF - 2 × VIN - VS =(VREF - 2 × (±Vh)) - 2 × (±Vh) ··· (10)

[0076] The graphs shown in FIGS. 5A and 5B are graphs showing the output characteristics of the output signal VOUT when the adjustment value G in the adjustment circuit 320 is set to G = 2, VH = VREF + 4 × Vh, VL = VREF - 4 × Vh, VHX = VREF + 2 × Vh, and VLX = VREF - 2 × Vh.

[0077] The graph 400 in FIG. 5A is a composite of the individual graphs of Equation (9) and Equation (10). The graph 401 in FIG. 5B is a graph showing the output characteristics of the output signal VOUT when switches SW2a, SW2b, and SW2c are turned off from on when the output signal VOUT is not included in a predetermined amplitude range W from VREF - 4 × Vh to VREF + 4 × Vh.

[0078] As described above, according to the current sensor 200 having the circuit configuration shown in FIG. 3, when the output signal VOUT is not included in the predetermined amplitude range W, the amplification factor from the detection signal VIN to the output signal VOUT can be changed to decrease. Also, in the range where the measured current is relatively small, i.e., |±Vh| > VIN, the accuracy can be maintained, and in the case of |±Vh| < VIN, the output voltage can be suppressed, enabling a wide range to be obtained.

[0079] Here, let us consider the feedback factor β, which is the negative feedback loop of the amplifier circuit 260. Figures 6A and 6B are block diagrams of the operational amplifier 262 in Figure 3.

[0080] When the switches SW1a and SW1b are ON and the switches SW2a, SW2b, and SW2c are OFF, the current input to the inverting input terminal 262a as the voltage VA of the inverting input terminal 262a can be expressed as (VIN-VA) / R1 when viewed from the input side, and as (VA-VOUT) / R3 when viewed from the output side. (VIN-VA) / R1 and (VA-VOUT) / R3 have the same value, and therefore satisfy the following formula. (VIN-VA) / R1 and (VREF-VA) / R3...(11)

[0081] When equation (11) is expanded in terms of VA, VA can be expressed by the following equation (12). VA=(R1 / (R1+R3))×VOUT+(R3 / (R1+R3))×VIN...(12)

[0082] Therefore, when the switches SW1a and SW1b are ON and the switches SW2a, SW2b, and SW2c are OFF, the circuit can be represented by the block diagram shown in FIG. 6A, and the feedback factor β1 can be expressed by the following equation (13). β1=1 / (1+R3 / R1) (13)

[0083] 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 viewed from the input side, and as (VA-VOUT) / (R3 / 2) when viewed from the output side.

[0084] 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. (VIN-VA) / R1+(VREF-VA) / R2+(VS-VA) / R2=(VA-VOUT) / (R3 / 2)...(14)

[0085] By expanding equation (14) in terms of VA, VA can be expressed by the following equation (15). 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)

[0086] Therefore, when the switches SW1a and SW1b are ON and the switches SW2a, SW2b, and SW2c are ON, it can be represented by the block diagram shown in FIG. 6B, and the feedback factor β2 can be represented by the following equation (16). β2=1 / (1+R3 / (2×R1)+R3 / R2)...(16)

[0087] Here, R2 = 2 × R1 and R3 = 4 × R1, so β1 = β2 = 1 / 5.

[0088] That is, according to the configuration of the current sensor 200 shown in FIG. 3, it is possible to suppress the fluctuation in the feedback factor of the amplifier circuit 260 at the timing when the amplification factor is switched.

[0089] FIG. 7 is an example of a Bode plot showing the relationship between F0 and the feedback factor β when the operational amplifier 262 in FIG. 3 has a finite amplification factor A0 and a first-order LPF characteristic.

[0090] Generally, when an input signal is amplified using operational amplifier 262, the feedback factor β is less than 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 was formed, F0 is also smaller, and the frequency response is lower.

[0091] According to the configuration of the current sensor 200 shown in FIG. 3, when R2 = 2×R1 and R3 = 4×R1, regardless of the on / off states of switches SW2a, SW2b, and SW2c, the feedback ratios β1 = β2. That is, it means that the open-loop gain does not change, and it can be understood that the frequency responsiveness also does not change. By performing the above circuit configuration and constant selection, when the amplification factor from the detection signal VIN to the output signal VOUT is changed to decrease, it becomes possible to control the feedback ratio β so that there is no change. When simply reducing the amplification factor at |±Vh| < VIN, the feedback ratio β becomes β1 < β2 < 1. However, in the state transition from β1 to β2, if the change rate of the feedback ratio is large, when there is a transient current response from a small current to a large current, it becomes a cause of distortion. Therefore, the smaller the change rate of the feedback ratio, the better.

[0092] FIG. 8 is a diagram showing an example of the circuit configuration of the current sensor 700 according to the second embodiment. Similar to FIG. 2, the current sensor 700 detects the measurement current flowing through the conductor 210. Since the current sensor 700 in FIG. 8 has the same function as the current sensor 200 in FIG. 2, only the differential function will be described.

[0093] The amplification unit 750 is connected to the output unit 280 and may be configured as an inverting amplification circuit or a non-inverting amplification circuit using an operational amplifier as an example. The amplification unit 750 may amplify and output the amplitude of the signal with a predetermined gain. The amplification unit 750 branches and connects the output of the magnetic sensor 220 as the detection signal VIN, determines the input result with a predetermined threshold value, and controls it to be smaller than the predetermined gain. Also, similar to the current sensor 200 according to the first embodiment, a plurality of threshold values may be prepared.

[0094] Unlike the current sensor 200, the current sensor 700 determines the threshold value with the detection signal VIN and is suitable for applications that detect transient high currents earlier.

[0095] FIG. 9 shows an example of a circuit configuration using an inverting amplifier circuit of the amplifier unit 750. The amplifier unit 750 has the same function as the amplifier unit 250 of FIG. 3, so only the difference function will be described. In the amplifier unit 750, the detection signal VIN is input as an input signal of the comparator 330 instead of the output signal VOUT. The comparator 330 may similarly use a general window comparator circuit configuration, and VH=VREF+X is input as the positive side judgment value, and VL=VREF-X is input as the negative side judgment value. When the adjustment value G of the adjustment circuit 320 is G=0.5, VH=VREF+Vh, VL=VREF-Vh, VHX=VREF+2×Vh, and 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 those of FIG. 5A and FIG. 5B.

[0096] As described above, the current sensor 200 of the first embodiment and the current sensor 700 of the second embodiment can expand the measurable current range while suppressing fluctuations in the amplitude of the signal output from the amplifier circuit that occur when the gain is switched. Such a technical effect can be realized, for example, as shown in the above-mentioned embodiments, by a current sensor having a detection unit that outputs a detection signal (e.g., a signal generated due to a Hall element receiving a magnetic field) corresponding to a magnetic field generated in a conductor when a measurement current flows, and an amplifier circuit (e.g., an operational amplifier or a comparator) having a first input terminal (e.g., an inverting input terminal of an operational amplifier), a second input terminal (e.g., a non-inverting input terminal of an operational amplifier), and an output terminal, amplifying the detection signal input via the first input terminal and outputting an output signal via the output terminal, the amplifier circuit being configured to be switchable between at least a first amplification factor and a second amplification factor lower than the first amplification factor, and including a control circuit (e.g., control circuit 300 in the embodiments) that can input an offset signal (VS) to the first input terminal, and the control circuit stopping input of the offset signal to the first input terminal during a period when the first amplification factor is set, and inputting the offset signal to the first input terminal during a period when the second amplification factor is set.

[0097] The input and stop of the offset signal to the first input terminal is controlled, for example, by a switch provided between the control circuit and the amplifier circuit described in the embodiment.Then, when the amplitude of the detection signal or the output signal is included in a predetermined amplitude range, the amplification factor of the amplifier circuit is set to a first amplification factor (high gain), and when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range, the amplification factor of the amplifier circuit is set to a second amplification factor (low gain).The input of the offset signal to the first input terminal suppresses a change in the amplitude of the output signal that occurs in response to switching the amplification factor of the amplifier circuit between the first amplification factor and the second amplification factor.

[0098] Furthermore, since the feedback factor of the amplifier circuit does not change with the gain switching, the variation in the frequency response of the amplifier circuit can also be suppressed. Such a technical effect can be realized, for example, as shown in the above embodiment, by having an impedance element whose one end is connected to the first input terminal, and this impedance element is an impedance that suppresses the change in the feedback factor of the amplifier circuit caused by adding the offset signal to the detection signal. Note that a typical example of such an impedance element is connecting the resistor element 272, as shown in the above embodiment.

[0099] The resistance values ​​of the resistive elements 266, 268, 271, 272, and 273 and the potential applied to the resistive element 272 are merely examples. Depending on the resistance values ​​of the resistive elements 266, 268, 271, 272, and 273 or the magnitude of the offset signal VS, the potential applied to the resistive element 272 may be adjusted to an arbitrary potential based on the reference potential VREF so that the feedback ratio of the amplifier circuit 260 does not vary with the gain switching.

[0100] Further, a further modified example of the current sensor described above is shown in FIG. 10. FIG. 10 shows another example of a circuit configuration using an inverting amplifier circuit of the amplifier unit 250 according to the first embodiment. Since it has the same function, only the difference from the above embodiment will be described. The actuation signal DET, which is the output of the comparator 330, is connected to INV1010, which outputs an actuation signal DET_N obtained by inverting the actuation signal DET. A switch SW2d is connected between the non-inverting input terminal 262b, which is the second input terminal of the operational amplifier 262, and VREF, and SW2d is controlled by the actuation signal DET_N. The initial state of the switch SW2d (here, the actuation signal DET_N is Hi) is ON. A switch SW2e is connected between the non-inverting input terminal 262b and the offset signal VS, which is the output of the selector circuit 340, and SW2e is controlled by the actuation signal DET, and the initial state is OFF (here, the actuation signal DET is Lo). When the amplitude of the output signal VOUT is not within a predetermined amplitude range W, the switch SW2d is OFF (the actuation signal DET_N is Lo), the switch SW2e is ON (here, the actuation signal DET is Hi), and the non-inverting input terminal 262b is connected from VREF to the offset signal VS.

[0101] Here, since the non-inverting input terminal 262b is connected from VREF to the offset signal VS, 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 offset signal VS. If the detection signal VIN after this switching is again designated as a detection signal VIN', the detection signal VIN' is expressed by the following equation. VIN' = ±Vh + VS (17)

[0102] When the non-inverting input terminal 262b is connected to the offset signal VS from VREF, the switches SW1a and SW1b are ON, the switches SW2a, SW2b, SW2c, and SW2e are ON, and SW2d is OFF, and the output signal VOUT is expressed by the following equation. VOUT=(1+R3 / (2×R2)+R3 / (2×R1))×VS-R3 / (2×R1)×VIN'-R3 / (2×R2)×VREF...(18)

[0103] Here, when the resistive elements are connected so that R2=2×R1 and R3=4×R1, equation (18) becomes the following equation. VOUT=4×VS-2×VIN'-VREF...(19)

[0104] Here, at the timing when the switches SW2a, SW2b, SW2c and SW2e are turned from OFF to ON and the switch SW2d is turned from ON to OFF (i.e., the timing when the gain of the amplifier circuit 260 is switched), the offset signal VS is set so that VOUT in equation (2) and VOUT in equation (19) have the same value, thereby making it possible to suppress fluctuations in the output signal VOUT. That is, the offset signal VS is controlled to satisfy the following equation (20). 5×VREF-4×VIN=4×VS-2×VIN'-VREF...(20)

[0105] By substituting equations (7) and (17) into equation (20), the offset signal VS is given by the following equation (21). VS = VREF - (±Vh) (21)

[0106] Furthermore, by substituting the equations (17) and (21) into the equation (19), the output signal VOUT is given by the following equation (22): where VS is an offset signal and is a fixed value. VOUT=(VREF-2×(±Vh))-2×(±Vh)···(22)

[0107] Here, it can be seen that equation (10) and equation (22) are the same equation. Therefore, although the connection method in Fig. 10 is different from that in Fig. 3, the same result is obtained, and therefore the output characteristics of the output signal VOUT with respect to the detection signal VIN shown in Fig. 5A and Fig. 5B are also the same.

[0108] However, when deriving the input / output graphs shown in FIGS. 5A and 5B based on the embodiment shown in FIG. 10, the adjustment value G in the adjustment circuit 320 is set to G=4, and the output characteristics of the output signal VOUT are shown by setting VH=VREF+4×Vh, VL=VREF-4×Vh, VHX=VREF+Vh, and VLX=VREF-Vh.

[0109] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the claims that such modifications and improvements can also be included in the technical scope of the present invention.

[0110] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0111] 100 Current Sensor 110a current path 120a, 120b Magnetic sensor 130 Receiving unit 140 Filter section 150a, 150b Amplification section 160 Output section 170 Chopper Circuit 180 Correction section 200,700 Current Sensor 210 Conductor 220 Magnetic Sensor 250,750 Amplification section 260 Amplification Circuit 262 Operational Amplifier 262a Inverting input terminal 262b Non-inverting input terminal 262c output terminal 264 Feedback Resistor Circuit 266,268,271,272,273 Resistive elements 280 Output section 290 Correction Section 300 Control circuit SW1a, SW1b, SW2a, SW2b, SW2c switches 320 adjustment circuit 330 Comparator 340 Selector Circuit DET operation signal DET_POL Polarity signal VIN detection signal VOUT Output signal G Adjustment Value HL Threshold signal (lower limit) HV Threshold signal (upper limit) VS, VHX, VLX offset signals VREF Reference potential

Claims

1. a detection unit that outputs a detection signal corresponding to a magnetic field generated in a conductor when a measurement current flows; 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; a control circuit capable of inputting an offset signal to the first input terminal; the amplifier circuit is configured to be switchable between at least a first amplification factor and a second amplification factor lower than the first amplification factor; the control circuit stops inputting the offset signal to the first input terminal during a period in which the first amplification factor is set, and inputs the offset signal to the first input terminal during a period in which the second amplification factor is set. Current sensor.

2. the control circuit sets 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 sets 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 input of the offset signal to the first input terminal suppresses a change in the amplitude of the output signal that occurs in response to switching the gain of the amplifier circuit between the first gain and the second gain. The current sensor according to claim 1 .

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

4. 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 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 to a second resistance value lower than the first resistance value in the case of the second amplification factor; The control circuit includes:

3. The current sensor according to claim 2, wherein a resistance value of the feedback resistor circuit is set to the first resistance value when the amplitude of the detection signal or the output signal is within the predetermined amplitude range, and a resistance value of the feedback resistor circuit is set to the second resistance value when the amplitude of the detection signal or the output signal is not within the predetermined amplitude range.

6. The feedback resistor circuit includes: a first resistor element connected between the output terminal and the first input terminal; a second resistor element connected in parallel with the first resistor element between the output terminal and the first input terminal, The control circuit includes: When an amplitude of the detection signal or the output signal is within the predetermined amplitude range, the feedback resistance circuit is controlled to electrically connect the first resistance element between the output terminal and the first input terminal and not to electrically connect the second resistance element between the output terminal and the first input terminal; 6. The current sensor according to claim 5, further comprising: a feedback resistor circuit configured to electrically connect the first resistor element and the second resistor element 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.

7. The control circuit includes: when the amplitude of the detection signal or the output signal exceeds an upper limit value of the predetermined amplitude range, a first offset signal of a first potential is added to the detection signal as the offset signal; 3. The current sensor according to claim 2, wherein when the amplitude of the detection signal or the output signal falls below a lower limit value of the predetermined amplitude range, a second offset signal of a second potential lower than the first potential is added to the detection signal as the offset signal.

8. The amplifier circuit includes: a third resistor element having one end to which the detection signal is input and the other end connected to the first input terminal; a fourth resistor element having one end to which a reference potential is applied and the other end connected to the first input terminal; a fifth resistor element having one end to which the offset signal is input and the other end connected to the first input terminal; a first switch that switches whether or not the second resistor element is electrically connected between the output terminal and the first input terminal; a second switch that switches whether or not the fourth resistor element is electrically connected to the first input terminal; a third switch that switches whether or not the fifth resistor element is electrically connected to the first input terminal; having The control circuit includes: a comparator that, when the amplitude of the detection signal or the output signal is not included in the predetermined amplitude range, outputs an activation signal that activates the first switch, the second switch, and the third switch to electrically connect the second resistive element between the output terminal and the first input terminal, electrically connect the fourth resistive element to the first input terminal, and electrically connect the fifth resistive element to the first input terminal, and outputs a polarity signal that indicates whether the amplitude of the detection signal or the output signal exceeds an upper limit value of the predetermined amplitude range or falls below a lower limit value of the predetermined amplitude range; a selector circuit that, when the amplitude of the detection signal or the output signal exceeds an upper limit value of the predetermined amplitude range, inputs a first offset signal of a first potential as the offset signal to the one end of the fifth resistor element, and, when the amplitude of the detection signal or the output signal falls below a lower limit value of the predetermined amplitude range, inputs a second offset signal of a second potential lower than the first potential as the offset signal to the one end of the fifth resistor element, based on the actuation signal and the polarity signal; The current sensor of claim 6 , further comprising:

9. the comparator controls output of the actuation signal and the polarity signal by comparing the detection signal or the output signal with a first threshold signal of a third potential indicating an upper limit of the predetermined amplitude range obtained by adding a threshold potential to the reference potential, and a second threshold signal of a fourth potential indicating a lower limit of the predetermined amplitude range obtained by subtracting the threshold potential from the reference potential, The control circuit includes:

9. The current sensor according to claim 8, further comprising an adjustment circuit that inputs to the selector circuit the first offset signal of the first potential obtained by adding an adjustment potential based on the threshold potential to the reference potential, and the second offset signal of the second potential obtained by subtracting the adjustment potential from the reference potential.

10. a resistance value of the fourth resistor element and the fifth resistor element is twice the resistance value of the third resistor element, 9. The current sensor according to claim 8, wherein the resistance values ​​of the first resistive element and the second resistive element are four times the resistance value of the third resistive element.

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

12. 12. The current sensor of claim 11, wherein the at least one magnetic sensor is a Hall element, a magnetoresistance element (MR), a giant magnetoresistance element (GMR), a tunneling magnetoresistance element (TMR), a magneto-impedance element (MI element), or an inductance sensor.

13. a detection unit that outputs a detection signal corresponding to a magnetic field generated in a conductor when a measurement current flows; 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; a control circuit capable of inputting an offset signal to the first input terminal and the second input terminal; the amplifier circuit is configured to be switchable between at least a first amplification factor and a second amplification factor lower than the first amplification factor; The control circuit inputs the offset signal to the first input terminal during a period in which the second amplification factor is set, and stops input of the offset signal to the first input terminal during a period in which the first amplification factor is set.

Images