Processing circuit, current sensor, and processing method

Abstract

A processing circuit that processes a detection signal detected by a sensor element includes a main circuit that generates an output signal in response to the detection signal, an alternative circuit that generates an alternative signal in response to the value of the detection signal at a timing different from that of the output signal, a noise detection unit that outputs a noise signal that indicates the presence or absence of noise in the detection signal, and a selection unit that selects and outputs either the output signal or the alternative signal in response to the noise signal, and the selection unit outputs the alternative signal for a period longer than the noise detection period.

Description

[Technical Field]

[0001] The present invention relates to a processing circuit, a current sensor, and a processing method. [Background technology]

[0002] Patent Document 1 describes detecting voltage transients in a magnetic field sensor integrated circuit such as a current sensor. [Prior art document] [Patent documents] Patent Document 1: U.S. Patent No. 10,156,614 Summary of the Invention

[0003] In a first aspect of the present invention, there is provided a processing circuit that processes a detection signal detected by a sensor element, the processing circuit comprising: a main circuit that generates an output signal in response to the detection signal; an alternative circuit that generates an alternative signal in response to the value of the detection signal at a timing different from that of the output signal; a noise detection unit that outputs a noise signal that indicates the presence or absence of noise in the detection signal; and a selection unit that selects and outputs either the output signal or the alternative signal in response to the noise signal, wherein the selection unit outputs the alternative signal for a period longer than the noise detection period.

[0004] In the processing circuit, the selection section may output the substitute signal from the start of noise detection until a first set period has elapsed, or from the start of noise detection until a second set period has elapsed since the end of noise detection.

[0005] In any of the above processing circuits, the selection section may output the substitute signal for a period longer than the time required for the influence of noise in the detection signal on the output signal to converge.

[0006] In the processing circuit, the selection section may output the alternative signal for a period based on a time constant of the main circuit.

[0007] In any of the above processing circuits, the substitution circuit may generate a substitution signal according to a value of the detection signal at least one of before and during noise detection by the noise detection section.

[0008] In any of the above processing circuits, the substitution circuit may have a holding circuit that holds information about the detection signal, and the substitution circuit may generate the substitution signal based on the information held in the holding circuit.

[0009] In the processing circuit, the holding circuit may sequentially update the held information in response to the input detection signal, and may stop updating the information during the noise detection period.

[0010] In any of the above processing circuits, the substitution circuit may generate a substitution signal from information that is output in a last-in, first-out manner from the information held in the holding circuit.

[0011] In the above processing circuit, the holding circuit may generate a substitute signal starting from information that is Nth or later information designated in advance from the latest information in the update order.

[0012] In the processing circuit, the holding circuit may hold information on the detection signal that has been AD converted by the main circuit, and the holding circuit may have a shift register, and the shift register may sequentially record the information on the detection signal.

[0013] In the above processing circuit, the shift register may have at least a first holding unit and a second holding unit, the first holding unit and the second holding unit being continuous memory areas, the shift register may record information of the detection signal in a last-in, first-out manner in the order of the first holding unit to the second holding unit, and the substitution circuit may generate a substitution signal from the information recorded in the second holding unit.

[0014] Any of the above processing circuits may further include a connection circuit that connects the input of the detection signal to the main circuit to a predetermined reference voltage in response to noise detection by the noise detection section.

[0015] In any of the above processing circuits, the period during which the alternative signal is output may be longer than the period during which the connection circuit connects the input of the detection signal to the main circuit to a predetermined reference voltage.

[0016] In any of the above processing circuits, the period during which the alternative signal is output may be variable.

[0017] In a second aspect of the present invention, there is provided a current sensor comprising a sensor element that outputs a detection signal corresponding to a magnetic field generated by a current to be measured flowing through a conductor, and a processing circuit according to the first aspect of the present invention that is connected by wiring to the sensor element arranged via the conductor.

[0018] In any of the above current sensors, the sensor element may be a Hall element, and a parasitic capacitance may be generated by the wiring and the conductor.

[0019] In a third aspect of the present invention, there is provided a processing method for processing a detection signal detected by a sensor element, which includes generating an output signal according to the detection signal, generating a substitute signal according to the value of the detection signal at a timing different from that of the output signal, outputting a noise signal indicating the presence or absence of noise in the detection signal, selecting and outputting either the output signal or the substitute signal according to the noise signal, and outputting the substitute signal for a period longer than the noise detection period.

[0020] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a top view showing an example of a current sensor 100. FIG. [Figure 2] 1 is a cross-sectional view of a current sensor 100. FIG. [Figure 3] FIG. 2 is a diagram illustrating a first more specific configuration example of the current sensor 100 of the present embodiment. [Figure 4]An example of the operation of the current sensor 100 according to this embodiment will be described. [Figure 5] FIG. 4 is a diagram illustrating a second configuration example of the current sensor 100 of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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.

[0023] Fig. 1 is a top view showing an example of a current sensor 100. Fig. 2 is a cross-sectional view taken along the line J-J' of the current sensor 100 shown in Fig. 1. The current sensor 100 measures the current value of a current I to be measured flowing through a conductor 110. The current sensor 100 includes the conductor 110, a first sensor element 113a, a second sensor element 113b, a processing circuit 120, and a metal plate 130.

[0024] Conductor 110 has current path 111 and two lead terminals 112a and 112b. A current I to be measured flows through conductor 110. One end of current path 111 is connected to lead terminal 112a, and the other end is connected to lead terminal 112b. Current path 111 is U-shaped so that the current I to be measured flows in a circular direction from lead terminal 112a to lead terminal 112b.

[0025] The first sensor element 113a and the second sensor element 113b are arranged opposite each other via the conductor 110 and output detection signals corresponding to a magnetic field. The first sensor element 113a may output a detection signal of the voltage VH1P and a detection signal of the voltage VH1N from a pair of first output terminals, and the second sensor element 113b may output a detection signal of the voltage VH2P and a detection signal of the voltage VH2N from a pair of second output terminals. The first sensor element 113a and the second sensor element 113b may be, for example, a Hall element, a magnetoresistive effect element, a Hall IC, or a magnetoresistive effect IC. The first sensor element 113a and the second sensor element 113b are electrically connected to the processing circuit 120 via wiring 160, which is a conducting wire such as a metal wire. The first sensor element 113a is arranged in a gap 110a of the conductor 110 located inside the U-shaped current path 111. Thus, the wiring 160 crosses the conductor 110 between the first sensor element 113a and the processing circuit 120. The second sensor element 113b is disposed in the gap 110b between the U-shaped portion of the current path 111 and the U-shaped portion of the metal plate 130.

[0026] The processing circuit 120 is connected to the first sensor element 113a and the second sensor element 113b. The processing circuit 120 is connected to the first sensor element 113a, which is disposed via the conductor 110, by wiring 160. The processing circuit 120 processes the detection signals detected by the first sensor element 113a and the second sensor element 113b. The processing circuit 120 is configured, for example, by an LSI (Large Scale Integration). The processing circuit 120 is supported on a metal plate 130 insulated from the conductor 110. The processing circuit 120 is electrically connected to the lead terminal 141 via a wire 150, which is a conducting wire such as a metal wire. The metal plate 130 includes a U-shaped portion, and the U-shaped portion of the current path 111 is disposed inside the U-shaped portion of the metal plate 130.

[0027] 2, the conductor 110, the lead terminal 141, the processing circuit 120, the first sensor element 113a, and the second sensor element 113b are sealed in a mold resin 180 and formed into the same package. The mold resin 180 is a mold resin such as an epoxy resin.

[0028] In the current sensor 100, when a current I to be measured flows through the conductor 110, a magnetic field is generated in the U-shaped portion of the current path 111 according to the amount and direction of the current. The first sensor element 113a is disposed in a gap 110a near the U-shaped portion of the current path 111. Therefore, the first sensor element 113a detects a magnetic flux density generated by the current I to be measured flowing through the conductor 110, and outputs an electric signal according to the magnetic flux density to the processing circuit 120.

[0029] The second sensor element 113b detects the magnetic flux density generated by the current to be measured I flowing through the conductor 110, and outputs an electric signal corresponding to the magnetic flux density to the processing circuit 120. In this way, the first sensor element 113a and the second sensor element 113b detect a current corresponding to the current to be measured I flowing through the conductor 110.

[0030] The first sensor element 113a and the second sensor element 113b are disposed at a distance from the conductor 110 by gaps 110a and 110b, respectively, and are always out of contact with the conductor 110. This prevents electrical conduction between the conductor 110 and the first sensor element 113a, and between the conductor 110 and the second sensor element 113b, ensuring a gap (clearance) for maintaining insulation. The first sensor element 113a is supported by an insulating member 114, shown by a dashed line in FIG. 1. The insulating member 114 may be, for example, an insulating tape made of a polyimide material with high dielectric strength.

[0031] In the side view of the current sensor 100 taken along line J-J' shown in Fig. 2, the insulating member 114 is joined to a portion of the rear surface 130A of the metal plate 130 and is formed to support the first sensor element 113a. Although Fig. 2 shows only the first sensor element 113a, the insulating member 114 also supports the second sensor element 113b in the same manner as the first sensor element 113a.

[0032] A step 101 is formed on the back surface of a portion of the conductor 110, and this step 101 ensures that the conductor 110 is always positioned so that it does not come into contact with the insulating member 114. A molding resin 180 is filled between the back surface of the conductor 110 and the insulating member 114. The insulating member 114 is made of, for example, an insulating tape made of a polyimide material with excellent pressure resistance, and is attached to the back surface 130A of the metal plate 130 in the state shown in FIG. 2, and supports the first sensor element 113a from the back surface.

[0033] The conductor 110 and the first sensor element 113a are provided on the same surface of the insulating member 114. The height position of the magnetic sensing surface 116 of the first sensor element 113a is located between the bottom surface and the top surface of the conductor 110, for example, in the center.

[0034] The first sensor element 113a and the second sensor element 113b are electrically connected to the processing circuit 120 via wiring 160, which is a conductor such as a metal wire. However, due to the above-described structure, the conductor 110 and the wiring 160 are electrically connected by a parasitic capacitance 117. In such a current sensor 100, when a transient high voltage (dv / dt) is applied to the conductor 110, voltage noise propagates to the processing circuit 120 via the parasitic capacitance 117. The processing circuit 120 of the current sensor 100 in this embodiment reduces the effect of voltage noise on the output value.

[0035] 3 is a diagram showing a more specific first configuration example of the current sensor 100 of this embodiment. The processing circuit 120 has a bias circuit 200, a chopper switch 210, a reference circuit 215, a noise detection unit 220, a timer circuit 235, a connection circuit 240, a main circuit 250, an alternative circuit 260, and a selection unit 270.

[0036] The bias circuit 200 is connected to the first sensor element 113a and the second sensor element 113b and supplies a current or voltage to the first sensor element 113a and the second sensor element 113b. The bias circuit 200 applies (flows into) an excitation current to the first sensor element 113a and the second sensor element 113b. The chopper switch 210 performs chopper driving by switching between a pair of input terminals and a pair of first output terminals that supply a drive current to the first sensor element 113a, and a pair of input terminals and a pair of second output terminals that supply a drive current to the second sensor element 113b. The reference circuit 215 supplies a reference voltage VREF to a connection destination. The reference voltage may be a predetermined voltage value, for example, ground.

[0037] The noise detection unit 220 is connected to the pair of first output terminals of the first sensor element 113a, the pair of second output terminals of the second sensor element 113b, and the reference circuit 215. The noise detection unit 220 outputs a noise signal indicating the presence or absence of noise in the detection signal. The noise detection unit 220 detects a common-mode voltage obtained by combining the voltage of the first detection signal output from the first output terminal of the first sensor element 113a and the voltage of the second detection signal output from the second output terminal of the second sensor element 113b. When a transient high voltage (dv / dt) is applied to the conductor 110, the noise detection unit 220 detects the common-mode voltage obtained by combining the voltages propagated through the parasitic capacitances 117.

[0038] The noise detection unit 220 includes a high-pass filter 222, a low-pass filter 228, and a comparison unit 232. The high-pass filter 222 combines the voltage of the first detection signal and the voltage of the second detection signal. The high-pass filter 222 includes a plurality of first capacitors 223 and 224, a plurality of second capacitors 225 and 226, and a first resistor 227. One end of each of the plurality of first capacitors 223 and 224 is connected to a pair of first output terminals of the first sensor element 113a, and the other end is connected to the first resistor 227 via a node 231. One end of each of the plurality of second capacitors 225 and 226 is connected to a pair of second output terminals of the second sensor element 113b, and the other end is connected to the first resistor 227 via a node 231. The second capacitors 225 and 226 have the same capacitance as the first capacitors 223 and 224. The other end of the first resistor 227 is connected to the reference circuit 215, and the reference voltage VREF is applied thereto.

[0039] A first resistor 227 is connected between a node 231 to which the first capacitors 223, 224 and the second capacitors 225, 226 are connected and an output terminal of the reference circuit 215 that outputs the reference voltage VREF. This allows the first capacitors 223, 224, the second capacitors 225, 226, and the first resistor 227 to form a differentiation circuit that functions as a high-pass filter.

[0040] Low-pass filter 228 includes second resistor 229 and third capacitor 230. One end of second resistor 229 is connected to one end of first resistor 227 and node 231, and the other end is connected to comparing unit 232 and one end of third capacitor 230. One end of third capacitor 230 is connected between second resistor 229 and comparing unit 232, and the other end is grounded. Low-pass filter 228 configures an integrating circuit by connecting second resistor 229 between node 231 and comparing unit 232, and connecting ground GND between second resistor 229 and comparing unit 232 via third capacitor 230. Configuring such an integrating circuit makes it possible to remove unintended high-frequency noise.

[0041] The noise detection unit 220 has the function of detecting a common-mode voltage by connecting the pair of first output terminals of the first sensor element 113a and the pair of second output terminals of the second sensor element 113b to a common node 231 via first capacitors 223 and 224 and second capacitors 225 and 226, respectively. With this circuit configuration, the voltage change excited in response to the measurement current I flowing through the conductor 110 is expressed by the following equation, where ΔV1 is the differential output of the first sensor element 113a and ΔV2 is the differential output of the second sensor element 113b.

[0042] ΔV1=VH1P-VH1N (1) ΔV2=-(VH2P-VH2N) (2)

[0043] From this, if the voltages of the detection signals output from the pair of first output terminals of the first sensor element 113a and the pair of second output terminals of the second sensor element 113b are expressed as ΔV1 and ΔV2, they can be expressed by the following equation. VH1P=ΔV1 / 2 (3) VH1N=-ΔV1 / 2 (4) VH2P=-ΔV2 / 2 (5) VH2N=ΔV2 / 2 (6)

[0044] Here, the voltage VHPF of the signal output from the node 231 via the uniform first capacitances 223, 224 and second capacitances 225, 226 is expressed by the following equation using the above equations (3) to (6). VHPF=VH1P+VH1N+VH2P+VH2N =ΔV1 / 2-ΔV1 / 2-ΔV2 / 2+ΔV2 / 2=0...(7)

[0045] According to equation (7), the change voltage excited according to the current I to be measured becomes 0 and is not output.

[0046] On the other hand, if the voltage propagated by the transient high voltage (dv / dt) to the conductor 110 via the parasitic capacitance 117 is a voltage ΔVd in the same direction, then VH1P, VH1N, VH2P, and VH2N are expressed by the following equations. VH1P=ΔVd (8) VH1N=ΔVd (9) VH2P=ΔVd (10) VH2N=ΔVd (11)

[0047] Here, the voltage VHPF of the signal output from the node 231 via the uniform first capacitances 223, 224 and second capacitances 225, 226 is expressed by the following equation using the above equations (8) to (11). VHPF=VH1P+VH1N+VH2P+VH2N =ΔVd+ΔVd+ΔVd+ΔVd=Δ4Vd...(12)

[0048] As shown in equation (12), the voltages of the detection signals output from the pair of first output terminals of the first sensor element 113a and the pair of second output terminals of the second sensor element 113b to which the transient high voltage (dv / dt) is applied are combined and output from node 231. Therefore, with this connection configuration, the noise detection unit 220 can detect only the transient high voltage (dv / dt).

[0049] The above description has been given using a pair of first output terminals of the first sensor element 113a and a pair of second output terminals of the second sensor element 113b. It is clear that in the case of a single sensor element, the noise detection unit 220 can perform similar detection even when using a pair of output terminals VH1P and VH1N. Furthermore, when the processing circuit 120 selects any two of the pair of first output terminals of the first sensor element 113a and the pair of second output terminals VH1P, VH1N, VH2P, and VH2N of the second sensor element 113b, the processing circuit 120 can also select any combination in which the voltage change excited in response to the current I to be measured is zero, depending on the relative positions of the first sensor element 113a, the second sensor element 113b, and the conductor 110.

[0050] The comparison unit 232 is connected to the reference circuit 215. The comparison unit 232 may compare the voltage input from the low-pass filter 228 with a predetermined threshold and, when the input voltage exceeds the threshold, output a noise signal (the Detect signal in FIG. 3 ) indicating that noise has been detected. The comparison unit 232 may be supplied with a voltage of VREF±ΔV (threshold), where VREF is the reference voltage supplied to the high-pass filter 222. The comparison unit 232 compares |Δ4Vd| with |ΔV| using a general window comparator circuit. If Δ4Vd is larger, the noise signal is set to a first logic (e.g., High), and if Δ4Vd is smaller, the noise signal is set to a second logic (e.g., Low). Here, in this embodiment, the noise detection period may be the period from when the noise signal becomes the first logic at the nth time (n is an odd number, and the same applies hereinafter; for example, n=1), becomes the second logic, and then becomes the first or second logic again (the (n+1)th time). In addition to this definition of the noise detection period, the period in which the first logic is applied may also be defined as the noise detection period.

[0051] The timer circuit 235 is connected to the comparison unit 232 and counts at an arbitrary CLK, which is not shown in Fig. 3. The timer circuit 235 outputs a first timer signal (Mask signal in Fig. 3) and a second timer signal (DIG signal in Fig. 3) in response to the noise signal from the comparison unit 232.

[0052] The timer circuit 235 receives the nth noise signal of the first logic (e.g., High) from the comparison unit 232, changes the first timer signal from the second logic (e.g., Low) to the first logic, maintains the first logic for a predetermined first count, and then changes the first timer signal from the first logic to the second logic. Furthermore, the timer circuit 235 receives the nth noise signal of the first logic from the comparison unit 232, changes the second timer signal from the second logic to the first logic, maintains the first logic for a predetermined second count, and then changes the first timer signal from the first logic to the second logic. At this time, the timer circuit 235 does not accept noise signals from the (n+1)th onward for a certain period of time. That is, the timer circuit 235 does not accept noise signals of the second logic for a certain period of time, and then, at a certain time thereafter, the timer circuit 235 is initialized and performs an operation to accept the next noise signal. Here, the first count and the second count may be preset to periods longer than the noise detection period.

[0053] The connection circuit 240 is connected to the first output terminal of the first sensor element 113a, the second output terminal of the second sensor element 113b, the reference circuit 215, and the timer circuit 235. In response to noise detection by the noise detection unit 220, the connection circuit 240 may connect the detection signal input to the main circuit 250 to a predetermined reference voltage. The connection circuit 240 has a plurality of first switches 242 between the pair of first output terminals of the first sensor element 113a and the pair of second output terminals of the second sensor element 113b and the main circuit 250, respectively. The connection circuit 240 also has a plurality of second switches 244 between the pair of first output terminals of the first sensor element 113a and the pair of second output terminals of the second sensor element 113b and the main circuit 250, respectively, and between the pair of second output terminals of the first sensor element 113a and the pair of second output terminals of the second sensor element 113b and the reference circuit 215, respectively. The connection circuit 240 switches the first switch 242 and the second switch 244 on and off in response to the first timer signal. In response to the first timer signal, the connection circuit 240 is controlled such that the second switch 244 is turned off when the first switch 242 is turned on, and the second switch 244 is turned on when the first switch 242 is turned off.

[0054] When the first timer signal is at a second logic level (e.g., Low), the connection circuit 240 is controlled to turn on the first switch 242 and turn off the second switch 244, thereby selecting and outputting the output from the first output terminal of the first sensor element 113a and the second output terminal of the second sensor element 113b. On the other hand, when the first timer signal is at a first logic level (e.g., High), the connection circuit 240 is controlled to turn off the first switch 242 and turn on the second switch 244, inputting the reference voltage from the reference circuit 215 to the main circuit 250 and outputting a voltage equivalent to the current to be measured I=0. This makes it possible to suppress peaks in the sensor output caused by noise. Here, the connection circuit 240 is described as outputting a voltage equivalent to the current to be measured I=0, but any voltage may be output.

[0055] The main circuit 250 generates an output signal according to an input signal. When the first timer signal is at the second logic level, the main circuit 250 may generate an output signal according to the detection signals from the first sensor element 113a and the second sensor element 113b. The main circuit 250 includes a subtraction circuit 252, an amplifier circuit 254, and an AD converter 256.

[0056] The subtraction circuit 252 is connected to the connection circuit 240. The subtraction circuit 252 calculates the difference between the signals input from the connection circuit 240. The subtraction circuit 252 calculates the current value based on the difference between the output of the first sensor element 113a and the output of the second sensor element 113b, canceling out the influence of externally generated magnetic fields, i.e., offsetting in-phase noise.

[0057] While noise is not detected by noise detection unit 220, subtraction circuit 252 derives the current value of the current flowing through conductor 110 based on the output of first sensor element 113a and the output of second sensor element 113b. In response to noise detection by noise detection unit 220, the output of first sensor element 113a and the output of second sensor element 113b are masked by connection circuit 240, and subtraction circuit 252 outputs a signal based on the reference voltage. Depending on the number of sensors and the arrangement of conductor 110, subtraction circuit 252 may be an adder circuit or a differential amplifier circuit.

[0058] The amplifier circuit 254 is connected to the subtraction circuit 252. The amplifier circuit 254 amplifies the output value from the subtraction circuit 252 by a predetermined gain.

[0059] The AD converter 256 is connected to the amplifier circuit 254. The AD converter 256 outputs an output signal obtained by converting the analog signal output by the amplifier circuit 254 into a digital signal. The AD converter 256 is, for example, a delta-sigma AD converter.

[0060] The current sensor 100 configured as described above calculates a current value based on the difference between the outputs of the first sensor element 113a and the second sensor element 113b, thereby canceling the influence of externally generated magnetic fields. That is, in an ideal case, the current sensor 100 configured as described above would not detect the influence of a transient high voltage (dv / dt) applied to the conductor 110. However, due to wire sweep during filling with molding resin or deviation during assembly, the balance of the parasitic capacitance 117 is disrupted, and the voltage noise propagating to the processing circuit 120 is not canceled out, resulting in the output signal being generated from an amplified signal.

[0061] The substitute circuit 260 is connected to the AD converter 256. The substitute circuit 260 generates a substitute signal according to the value of the detection signal at a timing different from that of the output signal generated by the main circuit 250. The substitute circuit 260 may generate a substitute signal according to the output signal generated by the main circuit 250. The output signal input to the selection section 270 simultaneously with the substitute signal may be generated at a timing different from that of the output signal used to generate the substitute signal (i.e., from a detection signal at a different timing).

[0062] The substitution circuit 260 includes a holding circuit 262. The holding circuit 262 may hold information about the detection signal. The holding circuit 262 may hold, as information about the detection signal, the value of an output signal generated from the detection signal by the main circuit 250. The holding circuit 262 may hold information about the detection signal that has been AD converted by the main circuit 250. As a result, the substitution circuit 260 may generate and output a substitution signal based on the information held in the holding circuit 262. The holding circuit 262 includes a register 264, an update switch 266, and a switching unit 268. Note that, in the configuration example described below, an example is shown in which the main circuit 250 includes an AD converter 256, but this is not limited thereto, and the substitution circuit 260 may output an analog signal. In this case, the substitution circuit 260 may hold the analog signal output by the amplifier circuit 254 in the holding circuit 262 and generate a substitution signal according to the held analog signal.

[0063] The register 264 is connected to the AD converter 256. The register 264 may sequentially update the information it holds in response to the input detection signal, and may stop updating the information during the noise detection period. The register 264 may hold 16 bits or more, and may be a shift register, for example. The register 264 may hold the bit values ​​of the output signal input from the AD converter 256 in the order of input. The register 264 has a first holding unit 264a that holds newer information in the register 264, and a second holding unit 264b that holds older information. The first holding unit 264a and the second holding unit 264b may be continuous storage areas. The register 264 may record the detection signal information in a last-in, first-out manner, from the first holding unit 264a to the second holding unit 264b. The first holding unit 264a may hold the most recent bits (for example, 3 or more bits) in the register 264, and the second holding unit 264b may hold bits (for example, 16 or more bits) that were updated before the information held in the first holding unit 264a. The second holding unit 264b may output last-in-first-out information (the most recent one or more bits in the second holding unit 264b) and first-in-first-out information (the oldest one or more bits in the second holding unit 264b). The second holding unit 264b may output newer (for example, the latest) information and older (for example, the oldest) information in accordance with the input order to different input terminals of the switching unit 268 in response to a reverse signal REV from a control circuit (not shown).

[0064] The update selector switch 266 is disposed between the first holding unit 264a and the second holding unit 264b. For example, the update selector switch 266 may be turned off during a noise detection period in which noise is detected by the noise detection unit 220, and may be turned on during periods other than the noise detection period. The update selector switch 266 may be turned off when the second timer signal becomes a first logic (e.g., High), and may be turned on when the second timer signal becomes a second logic (e.g., Low). This allows the holding circuit 262 to disconnect one or more bits that are the most recent in the update order (e.g., up to the pre-specified N-1th piece of information held in the first holding unit 264a of the register 264) from the second holding unit 264b. The holding circuit 262 may generate a substitute signal using, as a starting point, information that is a pre-specified Nth piece or more (N is an integer equal to or greater than 2) from the most recent information in the update order. By controlling the update selector switch 266 to be turned off, the holding circuit 262 does not hold information that is affected by noise during the noise detection period.

[0065] The switching unit 268 may output one of the newer information and the older information from the second holding unit 264b in response to a reverse signal REV from a control circuit (not shown). The reverse signal REV from the control circuit (not shown) may be set in response to an input from a user, and may be a signal that instructs the switching unit 268 to output either the newer information or the older information. By the switching unit 268 outputting the newer information from the second holding unit 264b, the substitution circuit 260 can generate a substitution signal from the information held in the holding circuit 262 that has been output in a last-in, first-out order.

[0066] The selection unit 270 is connected to the main circuit 250, the alternative circuit 260, and the timer circuit 235. The selection unit 270 selects and outputs either the output signal or the alternative signal in response to the noise signal. The selection unit 270 outputs the alternative signal for a period longer than the noise detection period. The selection unit 270 may output the alternative signal for a period longer than the time required for the influence of noise in the detection signal on the output signal to converge. The time required for the influence of noise in the detection signal to converge may be based on a time constant of the main circuit 250 (e.g., the amplifier circuit 254). The selection unit 270 may output the alternative signal for a period based on the time constant of the main circuit 250. The selection unit 270 may select and output either the output signal or the alternative signal in response to a second timer signal from the timer circuit 235. The selection unit 270 may select and output an alternative signal during a period in which the second timer signal from the timer circuit 235 is at a first logic (e.g., High), and may select and output an output signal from the main circuit 250 during a period in which the second timer signal is at a second logic (e.g., Low).

[0067] Fig. 4 shows an example of the operation of the current sensor 100 according to this embodiment. In Fig. 4, time t indicates the time axis of each signal, the input voltage indicates a voltage value generated by the current flowing through the conductor 110, the noise signal indicates the output (Detect) of the comparison unit 232, the first timer signal indicates the signal (MASK) output from the timer circuit 235 to the connection circuit 240, the output of the amplifier circuit 254 indicates the analog signal output from the amplifier circuit 254, the second timer signal indicates the signal (DIG) output from the timer circuit 235 to the substitution circuit 260 and the selection unit 270, and OUT indicates the signal output from the selection unit 270.

[0068] When the input current in the conductor 110 changes, a transient high voltage (dv / dt) is input to the processing circuit 120, and the comparator 232 outputs a noise signal that goes High at the timing of the change in the input voltage (the timing at which the slope of the input voltage changes). Here, the noise detection period may be the period from the nth High (rising edge) in the noise signal to the (n+1)th High or Low (falling edge).

[0069] The timer circuit 235 outputs a first timer signal that is high from the nth time the noise signal goes high until the first count, and that is low otherwise. The connection circuit 240 connects the detection signal input to the main circuit 250 to the reference circuit 215 while the first timer signal is high. When the connection circuit 240 connects the input to the main circuit 250 to the reference circuit 215, the amplifier circuit 254 outputs an amplified signal corresponding to the reference voltage. This allows the output of the amplifier circuit 254 to change to the reference voltage without exceeding the upper limit of normal operation, thereby effectively reducing the influence of noise on the output signal of the main circuit 250. The period during which the first timer signal is high (i.e., the first count) may be at least longer than the noise detection period. Here, the period during which the first timer signal is high (i.e., the first count) may be set in the timer circuit 235 in advance to a time equal to or longer than the acquired time, which is determined in advance through experiment or simulation. The time required for the detection signal input to the main circuit 250 to converge to the reference voltage when connected to the reference circuit 215 may be determined in advance through experiment or simulation. Alternatively, the noise detection period may be obtained in advance through an experiment or a simulation, and a time equal to or greater than the obtained noise detection period may be set in the timer circuit 235 in advance.

[0070] The timer circuit 235 outputs a second timer signal that is high from the nth time the noise signal goes high until the second count, and that is low during other periods. The selection unit 270 may output the substitute signal from the start of noise detection until a first set period (e.g., the second count) has elapsed. The selection unit 270 outputs the substitute signal from the substitute circuit 260 during the period when the second timer signal is high (substitute signal output period), and outputs the output signal from the main circuit 250 during the period when the second timer signal is low. The holding circuit 262 turns off the update selector switch 266 during the period when the second timer signal is high, and turns on the update selector switch 266 during the period when the second timer signal is low. As a result, the current sensor 100 outputs a substitute signal that indicates the value of the output signal immediately before noise detection during the period when the second timer signal is high, thereby enabling an output with reduced influence of noise. In the output of the current sensor 100 in FIG. 4, the dashed line indicates the output signal generated by the main circuit 250 while the second timer signal is high, and the dashed-dotted line indicates the ideal value of the output signal when there is no noise. The period during which the second timer signal is high (i.e., the second count number) may be longer than the period during which the first timer signal is high. Therefore, the period during which the alternative signal is output can be longer than the period during which the connection circuit 240 connects the input of the detection signal to the main circuit 250 to a predetermined reference voltage. The selector 270 can more effectively reduce the influence of noise by switching from outputting the alternative signal to outputting the output signal after the influence of noise on the main circuit 250 has converged. Here, the period during which the second timer signal is high (i.e., the second count number) may be determined in advance through experiment or simulation, and a period equal to or longer than the convergence time may be preset in the timer circuit 235. The period during which the second timer signal is High (ie, the second count number) may be a period that is one or two clocks longer than the first timer signal (eg, the first count number+1 or 2).

[0071] The period for outputting the substitute signal may be variable. The end point of the period for outputting the substitute signal may be based on the start of noise detection or the end of noise detection. For example, the selection unit 270 may output the substitute signal from the start of noise detection until the second set period has elapsed since the end of noise detection. The timer circuit 235 may output a second timer signal that goes High when the noise signal goes High for the nth time, remains High for a predetermined third count (second set period) from the (n+1)th time the noise signal goes High or Low, and stays Low for the rest of the period. Because the period for outputting the substitute signal is determined based on the end of noise detection, the current sensor 100 can more reliably output a signal with reduced noise influence. The period for outputting the substitute signal (the second count or the third count) may be changed by user input.

[0072] The current sensor 100 of this embodiment as described above can reduce the influence of noise by outputting a substitute signal instead of an output signal for a period longer than the noise detection period. However, if the substitute signal is output only during the noise detection period, the output signal will be output after the noise detection period, before the influence of noise has subsided, and this may further deteriorate the output accuracy when switching from the substitute signal.

[0073] 5 is a diagram showing a second configuration example of the current sensor 100 of this embodiment. The current sensor 100 of the second configuration example has a configuration similar to that of the current sensor 100 of the first configuration example and may operate in the same manner, except that the processing circuit 120 does not have the connection circuit 240, the noise detection unit 220 is not connected to the sensor element, and the alternative circuit 260 has an arithmetic circuit 500. Below, differences from the first configuration example will be mainly described.

[0074] The noise detecting section 220 may receive a control signal for controlling the current under measurement flowing through the conductor 110 from an external control circuit or the like, and may detect noise in response to the control signal. The noise detecting section 220 may output a noise signal indicating that noise has been detected in response to receiving a control signal for switching a switch connected to the conductor 110 to change the flow of the current under measurement. The noise detecting section 220 may set the noise signal to a first logic level (e.g., High) in response to receiving a control signal for turning on the switch connected to the conductor 110, and may then set the noise signal to a second logic level (e.g., Low) in response to receiving a control signal for turning off the switch connected to the conductor 110.

[0075] The timer circuit 235 outputs a second timer signal in response to a noise signal. The timer circuit 235 may set the second timer signal to the first logic in response to the noise signal becoming the first logic. The period during which the second timer signal is at the first logic in response to the noise signal (i.e., the period during which the selection unit 270 outputs the alternative signal) may be preset to a time equal to or longer than the time it takes for the effects of noise to converge on the output of the main circuit 250 that is not connected to the reference voltage by the connection circuit 240. In the second configuration example, the outputs of the first sensor element 113a and the second sensor element 113b are not connected to the reference voltage, and the convergence of the effects of noise on the output signals is delayed. Therefore, the period during which the selection unit 270 outputs the alternative signal in the second configuration example may be longer than the period during which the selection unit 270 outputs the alternative signal in the first configuration example.

[0076] The alternative circuit 260 has a holding circuit 262 and an arithmetic circuit 500. The holding circuit 262 may hold the output signal generated by the main circuit 250 at least one of before and during noise detection by the noise detection section 220 (i.e., during the noise detection period). The holding circuit 262 may be similar to that in the first configuration example.

[0077] The arithmetic circuit 500 is connected to the holding circuit 262. The arithmetic circuit 500 may generate an alternative signal according to the value of the detection signal at least in one of before and during the noise detection by the noise detection unit 220. The arithmetic circuit 500 may calculate the value of the output signal held in the holding circuit 262 and generate the calculation result as an alternative signal. The arithmetic circuit 500 may output, as an alternative signal, a predicted value calculated based on the value of the output signal before the noise detection (for example, immediately before). For example, the arithmetic circuit 500 may calculate a differential value or a predicted value from the values of a plurality of output signals before the noise detection and output the calculation result as an alternative signal. Alternatively, the arithmetic circuit 500 may output, as an alternative signal, an average value of the value of the output signal before the noise detection (for example, immediately before) and the value of the output signal during the noise detection. Further, the arithmetic circuit 500 may output, as an alternative signal, a calculation result obtained by multiplying the value of the output signal during the noise detection by a predetermined coefficient m (for example, 0 < m < 1). Further, the arithmetic circuit 500 may output, as an alternative signal, a calculation result obtained by adding a value obtained by multiplying a difference between the value of the output signal before the noise detection (for example, immediately before) and the value of the output signal during the noise detection by a predetermined coefficient m to the value of the output signal before the noise detection (for example, immediately before).

[0078] The selection unit 270 may select and output the alternative signal output by the arithmetic circuit 500 during the period when the second timer signal from the timer circuit 235 is at the first logic (for example, High), and may select and output the output signal during the period when the second timer signal is at the second logic (for example, Low).

[0079] The current sensor 100 of the second configuration example can output an alternative signal in which the influence of noise on the output signal is reduced by calculation in response to noise detection.

[0080] In the first and second configuration examples described above, the processing circuit 120 is configured as an LSI, but configuration examples other than these may also be employed. For example, the configuration from the first sensor element 113a and the second sensor element 113b to the main circuit 250 may be integrated into a single LSI or IC, and the noise detection unit 220, the timer circuit 235, the alternative circuit 260, and the selection unit 270 may be integrated into another MCU (Micro Controller Unit) or IC.

[0081] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0082] It should be noted that the execution order 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 that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[0083] 100 Current Sensor 101 Steps 110 Conductor 110a Gap 110b Gap 111 Current Path 112a Lead terminal 112b lead terminal 113a first sensor element 113b second sensor element 114 Insulating materials 116 Magnetically sensitive surface 117 Parasitic capacitance 120 Processing Circuit 130 Metal plate 141 Lead terminal 150 wire 160 Wiring 180 Molding resin 200 Bias circuit 210 Chopper Switch 215 Reference circuit 220 Noise detection unit 222 High-pass filter 223 1st capacity 224 1st capacity 225 2nd capacity 226 2nd capacity 227 1st resistance 228 Low-pass filter 229 2nd resistor 230 3rd capacity 231 nodes 232 Comparison Section 235 Timer Circuit 240 Connection Circuit 242 First Switch 244 Second Switch 250 Main circuit 252 Subtraction Circuit 254 Amplifier Circuit 256 AD converter 260 Alternative Circuit 264 registers 264a 1st holding part 264b 2nd holding part 266 Update Switch 268 Switching Unit 270 Selection Section

Claims

1. A processing circuit for processing a detection signal detected by the sensor element, a main circuit for generating an output signal in response to the detection signal; a substitution circuit that generates a substitution signal according to a value of the detection signal at a timing different from that of the output signal; a noise detection unit that outputs a noise signal indicating whether or not noise is present in the detection signal; a selection unit that selects and outputs either an output signal or an alternative signal in response to the noise signal; The selection unit outputs the alternative signal for a period longer than a noise detection period. Processing circuitry.

2. The selection unit outputs the substitute signal from the start of noise detection until a first set period has elapsed, or from the start of noise detection until a second set period has elapsed from the end of noise detection.

2. The processing circuit of claim 1.

3. The selection unit outputs the alternative signal for a period longer than the time required for the influence of noise in the detection signal on the output signal to converge.

2. The processing circuit of claim 1.

4. The selection unit outputs the alternative signal for a period based on a time constant of the main circuit.

4. The processing circuit of claim 3.

5. The substitution circuit generates the substitution signal according to a value of the detection signal at least one of before noise detection by the noise detection unit and during noise detection.

2. The processing circuit of claim 1.

6. the alternative circuit has a holding circuit that holds information about the detection signal; The substitution circuit generates the substitution signal based on the information held in the holding circuit.

2. The processing circuit of claim 1.

7. The holding circuit sequentially updates the held information in response to the input detection signal, and stops updating the information during the noise detection period.

7. A processing circuit according to claim 6.

8. The substitution circuit generates the substitution signal from the information outputted in a last-in, first-out manner from the information held in the holding circuit.

7. A processing circuit according to claim 6.

9. The holding circuit generates the substitute signal using information that is Nth or later information designated in advance from the latest information in the update order as a starting point.

9. A processing circuit according to claim 8.

10. the holding circuit holds information about the detection signal that has been AD converted by the main circuit; the holding circuit includes a shift register; The shift register sequentially records the information of the detection signal.

9. A processing circuit according to claim 8.

11. The shift register comprises: The device has at least a first holding portion and a second holding portion, the first storage unit and the second storage unit are continuous storage areas, the shift register records the information of the detection signal in a last-in, first-out manner in the order from the first holding unit to the second holding unit, The substitution circuit generates the substitution signal from the information recorded in the second holding unit.

11. The processing circuit of claim 10.

12. a connection circuit that connects the input of the detection signal to the main circuit to a predetermined reference voltage in response to the detection of noise by the noise detection unit; 2. The processing circuit of claim 1.

13. The period during which the alternative signal is output is longer than the period during which the connection circuit connects the input of the detection signal to the main circuit to a predetermined reference voltage.

13. A processing circuit according to claim 12.

14. The period during which the alternative signal is output is variable.

2. The processing circuit of claim 1.

15. a sensor element that outputs a detection signal corresponding to a magnetic field generated by a current to be measured flowing through a conductor; and a processing circuit according to claim 1 connected by wiring to the sensor element disposed via the conductor. Current sensor.

16. the sensor element is a Hall element, Parasitic capacitance occurs between the wiring and the conductor.

16. The current sensor of claim 15.

17. A processing method for processing a detection signal detected by a sensor element, comprising: generating an output signal in response to the detection signal; generating a substitute signal according to a value of the detection signal at a timing different from that of the output signal; outputting a noise signal indicating the presence or absence of noise in the detection signal; selecting and outputting either an output signal or an alternative signal in response to the noise signal; The output of the alternative signal is performed for a period longer than the noise detection period. Processing method.

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