Loop device

Abstract

A circuit board (10) of a circuit device (1) is provided with: a signal processing unit (3) for processing an input current signal (Iin); an energization control unit (4) through which a current that is larger than the current signal (Iin) flows; and a ground wiring unit (5) connected to a ground terminal (6). The ground wiring unit (5) comprises a main ground (51) common to the signal processing unit (3) and the energization control unit (4), and a plurality of sub-ground wires (52) to (55) connected to the main ground (51), and in the signal processing unit (3), ground portions (31g), (32g) of each of a plurality of analog signal circuits (3A) that are connected to one another by way of an analogue signal line (La) are connected to one another by way of the ground wiring line (521) and are connected to the main ground (51) by way of the same sub-ground wire (52).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2021-176617, filed on October 28, 2021, the contents of which are incorporated herein by reference. [Technical Field]

[0002] The present disclosure relates to a circuit device used for sensor control and the like. [Background technology]

[0003] For example, in-vehicle sensors such as NOx sensors are configured such that a detection signal from a sensor element attached to an exhaust gas passage is input into a sensor control device, and the sensor control device then controls the supply of current to a heater built into the sensor element based on commands from the sensor control device. Various circuits, including a circuit for processing the detection signal, which is a minute current, and a circuit for controlling the supply of current to the heater, are arranged on the circuit board of the sensor control device. While sharing a common ground for the various circuits simplifies the circuit configuration, it raises concerns about the impact of the large current that flows when the heater is energized, and therefore requires ingenuity in the connection structure between each circuit and the ground.

[0004] For example, the sensor control device described in Patent Document 1 has separate grounds for grounding the power supply circuit and the sensor element control circuit, which are signal system drive circuits, and for grounding the heater control circuit, which is a power system drive circuit. Specifically, the signal system ground terminal and the power system ground terminal are provided separately, and are connected to the ground of an external vehicle control device or a battery via different electrical paths. In addition, the ground of the communication system is combined with the signal system to share a common ground. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-244255 Summary of the Invention

[0006] In Patent Document 1, the grounds for the signal and communication systems are separated from the ground for the power system, thereby suppressing the influence of the heater current of the power system flowing to the ground on the control circuit of the signal system. However, even in this case, multiple ground terminals and electrical paths for connecting to the outside are required, and multiple ground wires connected to the respective ground terminals are required on the circuit board. This restricts the layout of various circuits and ground wires and tends to increase the size of the circuit board.

[0007] The object of the present disclosure is to provide a circuit device that improves the degree of freedom in the layout of a circuit board that contains a mixture of circuits that handle minute currents and circuits that handle large currents, and that can improve the accuracy of signal processing while suppressing size increase.

[0008] One aspect of the present disclosure is A circuit device (1) is provided on a circuit board (10), the circuit device (1) including: a signal processing unit (3) for processing an input current signal (Iin); a current control unit (4) through which a current (I) larger than the current signal flows; and a ground wiring unit (5) connected to a ground terminal (6), The signal processing unit includes a plurality of analog signal circuits (3A) connected via analog signal lines (La), The ground wiring section has a main ground (51) common to the signal processing section and the current control section, and a ground (52) connected to the main ground. The above signal processing circuit connection In order to a plurality of sub-ground wirings (52 to 55); The plurality of analog signal circuits include: an I / V conversion circuit (31) that converts the current signal, which is an analog signal, into a voltage signal, and an A / D conversion circuit (32) that converts the voltage signal into a digital signal and outputs it to an arithmetic circuit (33) of the signal processing unit; the A / D conversion circuit is provided independently of the digital signal circuit (3B) including the arithmetic circuit, and is disposed adjacent to the I / V conversion circuit; The above-mentioned I / V conversion circuit and the above-mentioned A / D conversion circuit Between the ground part (31g, 32g) is an independent wiring By ground connection wiring (521) selectively As well as being connected, The above ground connection wiring is are connected to the main ground via the same sub-ground wiring, The potential of the main ground varies in accordance with the operation of the current control unit, the above I / V conversion circuit and the above A / D conversion circuit Ground section to Ground potential (V G1 , V G2 ) The potential of the ground connection wiring is connected to the main ground via the same sub-ground wiring. Varies with the potential of It is located in a circuit device.

[0009] In the circuit device having the above configuration, a ground wiring section is arranged on the circuit board for grounding various circuits constituting the signal processing section and the current control section. Among the signal processing sections, multiple analog signal circuits are connected to the main ground at a single point via the same sub-ground wiring, so that the potentials of the ground sections connected to each other via the ground connection wiring are equivalent. Therefore, regardless of whether or not the potential of the main ground fluctuates, deviations in the reference potential for processing signals input and output via the analog signal lines are suppressed, enabling accurate processing. Furthermore, since the signal processing section and the current control section can share the main ground, there are fewer restrictions on the layout of wiring and circuits, so the size of the circuit board can be suppressed.

[0010] As described above, according to the above aspect, it is possible to provide a circuit device that improves the freedom of arrangement of a circuit board that mixes circuits that handle minute currents and circuits that handle large currents, and that can improve the accuracy of signal processing while suppressing size increase. [Brief explanation of the drawings]

[0011] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: [Figure 1] FIG. 1 is a block diagram showing the configuration of a sensor control circuit to which a circuit device according to a first embodiment is applied; [Figure 2] FIG. 2 is a circuit diagram showing a schematic configuration of a NOx detection system including a sensor control circuit according to the first embodiment; [Figure 3]3A, 3B, and 3C are enlarged cross-sectional views of a main part of the sensor element according to the first embodiment, showing the configuration thereof, in which (a), (b), and (c) are cross-sectional views taken along line aa in (b), line bb in (a), and line cc in (a), respectively; [Figure 4] FIG. 4 is a time chart showing transitions of a current flowing through a ground wiring portion of a sensor control circuit and a ground potential of a plurality of analog signal circuits in the first embodiment; [Figure 5] FIG. 5 is a schematic diagram illustrating a relationship between ground potentials of a plurality of analog signal circuits according to the first embodiment; [Figure 6] FIG. 6 is a schematic diagram illustrating the relationship between ground potentials of a plurality of analog signal circuits in a conventional configuration; [Figure 7] FIG. 7 is a block diagram showing an example of wiring and circuit layout of a ground wiring section of a sensor control circuit according to the first embodiment; [Figure 8] FIG. 8 is a block diagram showing another example of the wiring and circuit arrangement of the ground wiring section of the sensor control circuit in the first embodiment; [Figure 9] FIG. 9 is a block diagram showing another example of the wiring and circuit arrangement of the ground wiring section of the sensor control circuit in a conventional configuration; [Figure 10] FIG. 10 is a block diagram showing an example of the layout of wiring and circuits in the ground wiring section of the sensor control circuit in the first embodiment, in comparison with a conventional configuration; [Figure 11] FIG. 11 is a schematic diagram illustrating the relationship between the ground potentials of a plurality of analog signal circuits in the first embodiment in comparison with a conventional configuration; [Figure 12] FIG. 12 is a time chart showing the influence of heater energization on the NOx detection result by the sensor control circuit in the first embodiment; [Figure 13] FIG. 13 is a time chart showing the influence of heater energization on the NOx detection result by the sensor control circuit in a conventional configuration. [Figure 14] FIG. 14 is a block diagram showing an example of wiring and circuit layout of a ground wiring section of a sensor control circuit in the second embodiment; [Figure 15] FIG. 15 is a block diagram showing another example of the layout of the wiring and circuits of the ground wiring portion of the sensor control circuit in the second embodiment; [Figure 16] FIG. 16 is a block diagram showing an example of wiring and circuit layout of a ground wiring section of a sensor control circuit according to a third embodiment; [Figure 17] FIG. 17 is a block diagram showing another example of the layout of the wiring and circuits of the ground wiring portion of the sensor control circuit in the third embodiment; [Figure 18] FIG. 18 is a graph showing the relationship between the wiring length and the wiring resistance value of the ground wiring portion of the sensor control circuit in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Embodiment 1) A first embodiment of a circuit device will be described with reference to FIGS. 1 and 2, the circuit device of this embodiment can be configured as a sensor control circuit (i.e., SCU; Sensor Control Unit) 1 that controls the operation of a sensor element 2. The sensor element 2 is used, for example, in an on-vehicle sensor such as a NOx sensor, and is installed in an exhaust gas passage of an internal combustion engine (not shown) to detect specific gases such as NOx (i.e., nitrogen oxides) contained in the exhaust gas.

[0013] 1, the sensor control circuit 1 includes a circuit board 10 connected to a sensor element 2, and the circuit board 10 is provided with a signal processing unit 3, a current control unit 4, and a ground wiring unit 5. The signal processing unit 3 is a circuit for processing an input current signal Iin, and includes an analog signal circuit 3A that processes analog signals, and a digital signal circuit 3B that processes digital signals.

[0014] The ground wiring section 5 has a main ground 51 common to the signal processing section 3 and the current control section 4, and a plurality of sub-ground wirings 52 to 55 connected to the main ground 51. One of the sub-ground wirings, the sub-ground wiring 52, is provided as a wiring common to a plurality of analog signal circuits 3A.

[0015] 2, the sensor element 2 is provided with a plurality of cells 22 to 24 and a heater 25. In this case, the current signal Iin input to the signal processing unit 3 is a detected current signal in each cell of the sensor element 2, and corresponds to, for example, the sensor current Is, the monitor current Im, and the pump current Ip output from the sensor cell 22, the monitor cell 23, and the pump cell 24, respectively, as shown in FIG.

[0016] The current control unit 4 is a circuit through which a current larger than the current signal Iin (for example, on the order of nA to mA) input to the signal processing unit 3 flows. The current control unit 4 may include, for example, a heater control circuit 41. The heater control circuit 41 is a circuit for controlling the temperature of the sensor element 2 by turning the heater 25 on and off. In this case, when the heater 25 is driven, a current larger than the current signal Iin (for example, on the order of A) flows.

[0017] 1, the signal processing unit 3 is configured to include a plurality of analog signal circuits 3A connected via analog signal lines (hereinafter, appropriately abbreviated as signal lines) La. Preferably, such analog signal circuits 3A include an I / V conversion circuit 31 and an A / D conversion circuit 32. The I / V conversion circuit 31 converts a current signal Iin, which is an analog signal output from the sensor element 2, into a voltage signal. The A / D conversion circuit 32 further converts the voltage signal converted by the I / V conversion circuit 31 into a digital signal and outputs it to the digital signal circuit 3B.

[0018] The digital signal circuit 3B further processes the digital signal output from the A / D conversion circuit 32 of the multiple analog signal circuits 3A and outputs the processed signal to the outside. Specifically, the digital signal circuit 3B may include multiple circuits such as an arithmetic circuit 33 to which the digital signal from the A / D conversion circuit 32 is input, and a communication circuit 34 for communicating with the outside. The circuit board 10 is also provided with a power supply circuit 11 and the like. The arithmetic circuit 33 and the communication circuit 34 are connected via a digital signal line Lb. The circuits provided on the circuit board 10 and the sensor element 2 will be described in detail later.

[0019] In the ground wiring section 5, the main ground 51 can be provided as a common ground for all circuits arranged on the circuit board 10, in addition to the signal processing section 3 and the current control section 4. The main ground 51 is arranged to connect the ground side of the current control section 4 and the ground terminal 6, and is connected to each circuit on the circuit board 10 via one of the multiple sub-ground wirings 52 to 55.

[0020] The I / V conversion circuit 31 and the A / D conversion circuit 32, which are multiple analog signal circuits 3A, have their ground sections 31g, 32g connected to each other by ground connection wiring 521 and also connected to the main ground 51 via the same sub-ground wiring 52. This makes the potentials of the ground sections 31g, 32g equal, thereby suppressing deviations in the potential that serves as a reference for signal processing (hereinafter referred to as the reference potential, as appropriate). The analog signal circuit 3A inputs or outputs analog signals by signal processing based on this reference potential.

[0021] Preferably, the ground connection wiring 521 is provided as an independent wiring that selectively connects between the ground sections 31g, 32g of the I / V conversion circuit 31 and the A / D conversion circuit 32. Specifically, the ground connection wiring 521 connects only between the ground sections 31g, 32g, and is not connected to other circuit grounds arranged on the circuit board 10 or wiring connected to other circuit grounds. This makes the ground sections 31g, 32g of the multiple circuits to which analog signals are transmitted via the signal line La electrically independent from other circuits arranged on the circuit board 10, suppressing the influence on potential, and reducing restrictions on wiring connections, improving the degree of freedom in layout.

[0022] The connection structure between the ground connection wiring 521 and the ground sections 31g and 32g and the single sub-ground wiring 52 can be selected as appropriate depending on the arrangement of other wiring or circuits on the circuit board 10. For example, as shown in Fig. 1, the ground connection wiring 521 can be arranged as a wiring that connects the connection point between the ground section 31g of the I / V conversion circuit 31 and the sub-ground wiring 52 to the ground section 32g of the A / D conversion circuit 32. However, the present invention is not limited to this example, and the ground connection wiring 521 can also be arranged to connect the connection point between the ground section 32g of the A / D conversion circuit 32 and the sub-ground wiring 52 to the ground section 31g of the I / V conversion circuit 31.

[0023] Furthermore, the location where the sub-ground wiring 52 to which the ground connection wiring 521 is connected and the main ground 51 are connected is not particularly limited, and the connection can be made to any location depending on the arrangement of the other sub-ground wirings 53 to 55 on the circuit board 10. For example, as shown in Fig. 1, in an arrangement in which the heater control circuit 41 is arranged at a position farthest from the ground terminal 6 and the analog signal circuit 3A is adjacent to it, the sub-ground wiring 52 is connected to the main ground 51 at a position farther from the ground terminal 6 than the other sub-ground wirings 53 to 55. However, without being limited to this example, the sub-ground wiring 52 may be arranged closer to the ground terminal 6 than the other sub-ground wirings 53 to 55.

[0024] At this time, the ground potential VG1 and the ground potential V of the A / D conversion circuit 32. G2 are each provided by a common main ground 51 connected via a single sub-ground wiring 52. The main ground 51 is provided in common with other circuits including the heater control circuit 41 of the power supply control unit 4, and the potential fluctuates with the operation of these circuits. Furthermore, in the main ground 51 through which a relatively large current I flows, potential differences are likely to occur depending on the locations where multiple sub-ground wirings 52 to 55 are connected.

[0025] As shown in FIG. 4, even in this case, the I / V conversion circuit 31 and the A / D conversion circuit 32 are connected to the ground potential V G1 , V G2 That is, the magnitude of the current I flowing through the main ground 51 increases and decreases as the heater control circuit 41 turns the heater 25 on and off, and the magnitude of the ground potential V G1 , ground potential V G2 In other words, the ground potential V G1 , ground potential V G2 Since potential fluctuations occur equally regardless of the connection point with the main ground 51, V G1 ≒V G2 The difference is always V G1 -V G2 ≒0.

[0026] 5, when the minute current signal (detection current signal) Iin is processed by the signal processing unit 3, the potential on the ground side, which serves as the reference for signal processing in the analog signal circuit 3A, can be made uniform. That is, the I / V conversion circuit 31 converts the current signal Iin input from the sensor element 2 into a voltage, and converts it to the ground potential V G1 Voltage signal V OUT1 The A / D conversion circuit 32 converts the output from the I / V conversion circuit 31 into a ground potential V G2 The voltage signal V OUT2 It receives the signal as a digital signal and outputs it. G1 ≒V G2Therefore, the voltage signal V OUT1 , V OUT2 This suppresses deviation and improves detection accuracy.

[0027] On the other hand, as shown in FIG. 6, when the I / V conversion circuit 31 and the A / D conversion circuit 32 are connected to the main ground 51 by independent sub-ground wirings 52a and 52b, the ground potential V G1 , V G2 That is, if the sub-ground wirings 52a and 52b in the main ground 51 are connected at different locations (see, for example, the left diagram in FIG. 6), a potential difference (=I×R0) is generated, which is calculated by multiplying the wiring resistance R0 between the connection points by the current I. This potential difference (see, for example, the right diagram in FIG. 6) becomes larger as the current I flowing through the main ground 51 increases, which makes it more likely that the detection accuracy will decrease.

[0028] In addition, the arithmetic circuit 33 and communication circuit 34, which are digital signal circuits 3B in the signal processing section 3, are not affected by potential fluctuations in the main ground 51 during signal processing, and can therefore be connected to the main ground 51 by sub-ground wirings 53 and 54, respectively. The power supply circuit 11, which serves as the power source for these circuits, can also be directly connected to the main ground 51 by sub-ground wiring 55.

[0029] As described above, with the above configuration, the signal processing unit 3 including the analog signal circuit 3A for detecting minute currents and the current control unit 4 through which large currents flow can be arranged on a single circuit board 10 and grounded via the ground wiring unit 5 connected to a single ground terminal 6. Therefore, the detection accuracy can be improved without increasing the size of the circuit board 10, and the degree of freedom in layout is also improved.

[0030] In this embodiment, "connection" refers to connection via electrical wiring for electrical signal transmission, power supply, grounding, etc., and "independent" refers to electrical independence. The same applies to the following embodiments.

[0031] A specific example in which the sensor control circuit 1 is applied to a NOx sensor will be described in detail below. Fig. 2 shows a schematic configuration of a NOx detection system 100 including the sensor control circuit 1, and Fig. 3 shows details of each part of the sensor element 2. The sensor element 2 is usually housed in a sensor housing and is protected by an element cover when in use, but this is not shown here.

[0032] 3, the sensor element 2 includes a measurement gas chamber 20, a reference gas chamber 21, a sensor cell 22, a monitor cell 23, a pump cell 24, and a heater 25. The sensor element 2 is configured by laminating the heater 25, a solid electrolyte body 26, and an insulating layer 261. The measurement gas chamber 20 is formed as a space surrounded by the solid electrolyte body 26 and the insulating layer 261, and exhaust gas is introduced therein as the measurement gas G. The reference gas chamber 21 is formed as a space surrounded by the heater 25 and the solid electrolyte body 26, and air is introduced therein as the reference gas A.

[0033] The solid electrolyte body 26 is made of a zirconia-based solid electrolyte having oxygen ion conductivity. Specifically, for example, yttria-stabilized zirconia (YSZ) can be used as the solid electrolyte. The insulating layer 261 is plate-shaped and is laminated on the plate-shaped solid electrolyte body 26 via a first spacer 201 that forms the measurement gas chamber 20. The first spacer 201 is C-shaped with one side open, and a diffusion resistor 203 is disposed in the open portion to form an exhaust gas inlet 202. As a result, the exhaust gas is introduced into the measurement gas chamber 20 by the diffusion resistor 203 at a predetermined diffusion resistance.

[0034] The solid electrolyte body 26 is stacked on the plate-shaped heater 25 via a second spacer 211 that forms the reference gas chamber 21. The second spacer 211 has an air inlet (not shown) that opens on the opposite side to the inlet 202 of the measurement gas chamber 20. This allows air to be introduced into the reference gas chamber 21, generating a reference potential for calculating the NOx concentration. The insulating layer 261 and the first and second spacers 201, 211 can be made of an insulator such as alumina.

[0035] The solid electrolyte body 26 is formed to separate the measurement gas chamber 20 from the reference gas chamber 21, and is exposed to both the measurement gas chamber 20 and the reference gas chamber 21. This allows oxygen ions to move within the solid electrolyte body 26 in accordance with the difference between the NOx concentration in the exhaust gas and the NOx concentration in the atmosphere, generating a sensor current Is.

[0036] The sensor cell 22 has a sensor electrode 220, a solid electrolyte body 26, and a reference electrode 27. The sensor electrode 220 is formed on a surface of the solid electrolyte body 26 exposed to the measurement gas chamber 20. On the other hand, the reference electrode 27 is formed on a surface of the solid electrolyte body 26 exposed to the reference gas chamber 21. The sensor cell 22 shares the solid electrolyte body 26 and the reference electrode 27 with the monitor cell 23 and the pump cell 24, which will be described later.

[0037] The sensor electrode 220 contains a precious metal, such as platinum (Pt) and rhodium (Rh), and a solid electrolyte having the same composition as the solid electrolyte constituting the solid electrolyte body 26. At this time, NOx contained in the exhaust gas introduced into the measurement gas chamber 20 is adsorbed onto the exposed surface of the precious metal and ionized into nitrogen ions and oxygen ions by catalytic action. Of these, the oxygen ions are conducted within the solid electrolyte contained in the sensor electrode 220 and further conducted to the solid electrolyte body 26, which is detected as the sensor current Is.

[0038] The monitor cell 23 has a monitor electrode 230, a solid electrolyte body 26, and a reference electrode 27. The monitor electrode 230 is formed on the surface of the solid electrolyte body 26 exposed to the measurement gas chamber 20, and is disposed adjacent to the sensor electrode 220 in a direction perpendicular to the flow of exhaust gas from the inlet 202 toward the sensor cell 22. The monitor electrode 230 is an electrode containing, for example, platinum (Pt) and gold (Au), and although it does not have the ability to decompose NOx, it can decompose oxygen molecules, allowing a monitor current Im resulting from oxygen ions to flow.

[0039] The pump cell 24 is located upstream of the sensor cell 22 and the monitor cell 23 in the flow of exhaust gas, and includes a pump electrode 240, a solid electrolyte body 26, and a reference electrode 27. The pump electrode 240 is formed on the surface of the solid electrolyte body 26 that is exposed to the measurement gas chamber 20. Like the monitor electrode 230, the pump electrode 240 is an electrode containing platinum (Pt) and gold (Au), and reduces oxygen to generate oxygen ions. The oxygen ions travel through the solid electrolyte body 26 to the reference electrode 27 and are discharged into the reference gas chamber 21.

[0040] The pump cell 24 is a cell that adjusts the oxygen concentration in the measurement gas chamber 20 by its pumping action. The pump current Ip output from the pump cell 24 corresponds to the oxygen concentration in the measurement gas chamber 20, and a predetermined low oxygen concentration can be maintained in the measurement gas chamber 20 by adjusting the pump voltage applied between the electrodes of the pump cell 24. The sensor cell 22 and monitor cell 23 output a sensor current Is due to NOx and a monitor current Im due to residual oxygen, respectively, for the exhaust gas after the oxygen concentration has been adjusted.

[0041] Therefore, the outputs from these cells are input as detected current signals to the signal processing unit 3 of the sensor control circuit 1, where they are subjected to arithmetic processing and other operations to control pumping by the pump cell 24, and the NOx concentration can be detected based on the detected current signals from the sensor cell 22 and the monitor cell 23. That is, by subtracting the output of the monitor cell 23 from the output of the sensor cell 22, it is possible to obtain the NOx concentration with the offset of the output of the sensor cell 22 caused by residual oxygen canceled.

[0042] The heater 25 maintains the temperature of the solid electrolyte body 26 at a predetermined temperature, for example, 600°C or higher, allowing it to function as a solid electrolyte. The heater 25 is formed by providing a conductor layer 252 that generates heat when electricity is passed between ceramic substrates 251. The conductor layer 252 is formed so as to overlap the solid electrolyte body 26 when the surface on which the various electrodes 220, 230, 240, and 27 are formed is viewed from the front, so that the temperature of at least the portions on which the various electrodes 220, 230, 240, and 27 are formed and their vicinity can be maintained at an activation temperature.

[0043] 2, a NOx detection system 100 including a sensor control circuit 1 is equipped with a circuit board 10 on which a circuit for sensor control is mounted. The circuit board 10 is connected to the sensor element 2, and is also connected to a vehicle electronic control unit (hereinafter referred to as ECU) 7 and a battery B. Terminals for connecting to these external devices are arranged around the periphery of the circuit board 10, and on the circuit board 10 are formed an analog signal circuit 3A and a digital signal circuit 3B which form the signal processing unit 3, a heater control circuit 41 which forms the current control unit 4, a power supply circuit 11, a voltage application circuit 13 for applying a pump voltage, and the like.

[0044] Battery B is, for example, an in-vehicle battery, and is connected between a power supply terminal VB and a ground terminal GND provided on circuit board 10. Power supply terminal VB is connected to heater control circuit 41 via power line Lb, and ground terminal GND is connected to main ground 51. Power supply circuit 11 is connected to power line Lb in parallel with heater control circuit 41. Power supply circuit 11 is a circuit for converting battery voltage and generating power to be supplied to each circuit on circuit board 10; power supply wiring is not shown in the figure.

[0045] The heater control circuit 41 is made up of two switch circuits 42 and 43, and is connected to the heater 25 of the sensor element 2 via heater terminals H+ and H-. That is, the switch circuit 42, which is interposed between the power supply line Lb and the heater terminal H+, is connected to the positive terminal of the heater 25 via a heater wiring L1, and the switch circuit 43, which is interposed between the heater terminal H- and the main ground 51, is connected to the negative terminal of the heater 25 via a heater wiring L2. At this time, the switch circuits 42 and 43 are turned on and off based on a drive signal, which will be described later, so that power can be supplied from the battery B.

[0046] The sensor element 2 is connected to an analog signal circuit 3A on the circuit board 10 via multiple sensor signal lines L4 to L6. The analog signal circuit 3A includes an I / V conversion circuit 31 to which a current signal Iin (detected current signals Is, Im, Ip) from each cell of the sensor element 2 is input, and an A / D conversion circuit 32. The A / D conversion circuit 32 converts the analog signal from the I / V conversion circuit 31 into a digital signal, thereby enabling transmission and reception of signals between the sensor element 2 and the digital signal circuit 3B. The sensor element 2 is also connected to a voltage application circuit 13 provided on the circuit board 10 via sensor wiring L3, allowing the pump voltage applied to the pump cell 24 to be controlled.

[0047] The digital signal circuit 3B includes a microcomputer (hereinafter referred to as "mc") 12 including an arithmetic circuit 33, and a communication circuit 34. The mc 12 has a known configuration including a memory unit such as a ROM and a RAM, a CPU including the arithmetic circuit 33, and executes a pre-stored program and performs predetermined calculations to perform NOx detection processing based on the detected current signal from the sensor element 2. The arithmetic circuit 33 may be built into the mc 12, or may be provided independently, as described below. The A / D conversion circuit 32 may also be built into the mc 12.

[0048] Specifically, the I / V conversion circuit 31 includes a first detection circuit 311, a second detection circuit 312, and a third detection circuit 313, to which detection current signals are input from the respective cells of the sensor element 2. The A / D conversion circuit 32 includes first to third conversion circuits ADC-1 to ADC-3, which are connected to the first to third detection circuits 311 to 313 via signal lines La. The first detection circuit 311 detects the sensor current Is via a signal line L4 connected to the sensor cell 22 and a detection terminal S. The second detection circuit 312 detects the monitor current Im via a signal line L5 connected to the monitor cell 23 and a detection terminal M. The third detection circuit 313 detects the pump current Ip via a signal line L6 connected to the pump cell 24 and a detection terminal P.

[0049] The detected current signals input to the first to third detection circuits 311 to 313 are converted into voltage signals and input to the first to third conversion circuits ADC-1 to ADC-3, respectively. The first to third conversion circuits ADC-1 to ADC-3 further convert the input analog voltage signals into digital signals and output them to the microcomputer 12, which is the digital signal circuit 3B. The microcomputer 12 performs calculations based on the detected current signals of the sensor element 2 in the calculation circuit 33, and transmits the calculation results to the ECU 7 or receives control commands via the communication circuit 34.

[0050] The communication circuit 34 is configured, for example, by a CAN transceiver, and is connected to the ECU 7 via a pair of communication terminals CANL and CANH. This allows the microcomputer 12 to communicate with the ECU 7 and control the operation of the sensor element 2 based on a command signal from the ECU 7. For example, the microcomputer 12 outputs a drive signal for the heater 25 to a heater control circuit 41, which is the power supply control unit 4, and also outputs a control signal for controlling the pump voltage applied to the pump cell 24 to the voltage application circuit 13.

[0051] Specifically, the switch circuits 42, 43 of the current control unit 4 are turned on and off to control the current supply to the heater 25 of the sensor element 2, thereby maintaining the sensor element 2 at a temperature suitable for NOx detection. In the voltage application circuit 13, the pulse generation circuit 14 generates a predetermined pulse signal (pulse width modulation signal) based on the control signal, which is then converted into a predetermined voltage signal by the operational amplifier 15 and applied to the reference electrode 27 of the pump cell 24 via the common terminal COM.

[0052] The voltage applied to the pump cell 24 is adjusted within a range in which the pump current Ip flowing through the pump cell 24 maintains the limiting current characteristic, for example, so that the oxygen concentration in the measurement gas chamber 20 becomes a predetermined low concentration. The microcomputer 12 monitors the oxygen concentration in the measurement gas chamber 20 based on the output from the pump cell 24, for example, and controls the operation of the pump cell 24 by changing the duty ratio of the pulse signal.

[0053] Here, the circuit board 10 is provided with a ground wiring section 5 for grounding each circuit arranged on the board. The ground wiring section 5 has a common main ground 51 and multiple sub-ground wirings 52 to 55. The main ground 51 is provided in common to circuits including the signal processing section 3 and the current control section 4 arranged on the circuit board 10, and each circuit is connected to the main ground 51 by the multiple sub-ground wirings 52 to 55.

[0054] Of the multiple sub-ground wirings 52 to 55, the sub-ground wiring 52 is provided in common to the multiple analog signal circuits 3A connected via a signal line La in the signal processing unit 3. These multiple circuits are the I / V conversion circuit 31 and the A / D conversion circuit 32, and the first to third detection circuits 311 to 313 included in the I / V conversion circuit 31 are connected to the first to third conversion circuits ADC-1 to ADC-3 included in the A / D conversion circuit 32, respectively, via the signal line La. In this case, a ground section 31g common to the first to third detection circuits 311 to 313 is connected to a ground section 32g common to the first to third conversion circuits ADC-1 to ADC-3 by an independent ground connection wiring 521, and is connected to the main ground 51 via the same sub-ground wiring 52.

[0055] The circuit ground for handling analog signals may be provided in common with the ground section 31g of the I / V conversion circuit 31 or the ground section 32g of the A / D conversion circuit 32. For example, the operational amplifier 15 of the voltage application circuit 13 is connected to the ground section 32g of the A / D conversion circuit 32 to provide the same reference ground potential. The sub-ground wirings 53 to 55 are provided for the microcomputer 12 (arithmetic circuit 33), the communication circuit 34, and the power supply circuit 11, which are the digital signal circuit 3B, respectively, and connect the circuit grounds of these components to the main ground 51.

[0056] In this way, by connecting only the ground sections 31g, 32g of the analog signal circuit 3A connected via the signal line La with the ground connection wiring 521, which is an independent wiring, and by sharing the sub-ground wiring 52, it is possible to suppress the influence of the potential of the main ground 51 (see FIGS. 4 to 6 above). This allows the signal processing section 3 including the analog signal circuit 3A that handles minute currents and the current control section 4 that handles large currents to be connected to the common main ground 51, eliminating the need to provide separate grounds or ground terminals for each, and reducing restrictions on the layout of the main ground 51, which requires a relatively large area. Furthermore, since there are no restrictions on the layout of the circuits on the circuit board 10, the size of the board can be suppressed.

[0057] 2, terminals connected to the sensor element 2 are arranged on one of two opposing sides of the circuit board 10, and terminals connected to the battery B and the ECU 7 are arranged on the other of the two sides. As in the arrangement shown in FIG. 1, the signal processing unit 3 and the current control unit 4 have the I / V conversion circuit 31 of the analog signal circuit 3A and the heater control circuit 41 arranged on the side closer to the sensor element 2. In addition, between the I / V conversion circuit 31 and the communication terminals CANL and CANH connected to the ECU 7, the A / D conversion circuit 32 of the analog signal circuit 3A and the microcomputer 12 and communication circuit 34 of the digital signal circuit 3B are arranged in the order in which signals are input and output.

[0058] In this arrangement, the I / V conversion circuit 31 and the A / D conversion circuit 32 of the analog signal circuit 3A are arranged adjacent to each other on the circuit board 10, so that the ground connection wiring 521 that connects the ground sections 31g and 32g can be connected over the shortest distance. In this case, the arrangement of the ground connection wiring 521 is not restricted, and the effects of wiring resistance can be suppressed. However, this arrangement is not limitative, and the digital signal circuit 3B and other circuits are also connected to single sub-ground wirings 53 to 55, so their arrangement on the circuit board 10 is not restricted. The arrangement of the main ground 51 is also not restricted, and can be set appropriately depending on the arrangement of the circuit board 10 and other circuits.

[0059] As shown in an example in FIG. 7 , in a configuration in which each circuit and the ground wiring section 5 are arranged on one surface of the circuit board 10, for example, a single main ground 51 is wired between two opposing sides so as to cross the center of the circuit board 10. A heater control circuit 41 and an I / V conversion circuit 31 are arranged on one of the opposing sides, and a ground terminal 6 is arranged in the middle of the other side. One end of the main ground 51 is connected to the ground terminal 6, and the other end is connected to the heater control circuit 41. An A / D conversion circuit 32 and a power supply circuit 11 are arranged adjacent to the heater control circuit 41 and the I / V conversion circuit 31, facing each other with the main ground 51 in between. An arithmetic circuit 33 and a communication circuit 34 are arranged adjacent to these circuits, facing each other with the main ground 51 in between.

[0060] 8, the arithmetic circuit 33 may be positioned opposite the heater control circuit 41 with the main ground 51 interposed therebetween, and the I / V conversion circuit 31 and the A / D conversion circuit 32 may be sequentially disposed adjacent thereto. In either case, the I / V conversion circuit 31 and the A / D conversion circuit 32 of the analog signal circuit 3A are connected via a signal line La, and are connected to the grounds by a ground connection wiring 521, and are also connected to the main ground 51 via a sub-ground wiring 52. The arithmetic circuit 33, the communication circuit 34, and the power supply circuit 11 are connected to the main ground 51 via sub-ground wirings 53 to 55, respectively.

[0061] This eliminates the need to separate ground patterns for grounding the signal processing unit 3 and the energization control unit 4, improving the degree of freedom in the layout of wiring patterns and circuit arrangement. The A / D conversion circuit 32 and the arithmetic circuit 33 can be configured to be built into the microcomputer 12, or can be configured to be independent of each other. Preferably, the A / D conversion circuit 32 and the arithmetic circuit 33 are provided independent of the microcomputer 12, and the I / V conversion circuit 31 and the A / D conversion circuit 32 are arranged adjacent to each other and connected at the shortest distance, which is advantageous for improving detection accuracy.

[0062] In contrast to this, for example, as shown in the conventional configuration example in FIG. 9, if the main ground 51a of the power system to which the heater control circuit 41 is connected and the main ground 51b of the signal system to which each circuit 31 to 34 of the signal processing unit 3 is connected are provided separately, restrictions will arise on the wiring or circuit layout in order to connect the main ground 51b of the signal system to each circuit 31 to 34.

[0063] Therefore, in the example shown in FIG. 9, the circuits 31 to 34 are arranged opposite to each other with the main ground 51b interposed therebetween and connected by the sub-ground wirings 52 to 55. However, the main ground 51a of the power system is arranged so as to bypass these circuits. If an attempt is made to avoid this, the circuit board 10 will inevitably become larger. Also, in any case, a ground terminal 61 to which the main ground 51a of the power system is connected and a ground terminal 62 to which the main ground 51b of the signal system is connected are each required. The sub-ground wirings 52 that connect the I / V conversion circuit 31 and the A / D conversion circuit 32 to the main ground 51b are independent sub-ground wirings 52a and 52b, respectively.

[0064] In [1] shown in FIG. 10, as in this embodiment, the I / V conversion circuit 31 and the A / D conversion circuit 32 are connected by a ground connection wiring 521 and then connected to the main ground 51 by a sub-ground wiring 52 (wiring resistance R1). It is shown in comparison with the conventional configuration [2] shown in FIG. 9 and the conventional configuration [3] shown in FIG. 6. [1] to [3] shown in FIG. 11 are the current I flowing through the main ground 51 or the main ground 51a in each configuration, and the ground potentials V G1 , V G2 of the I / V conversion circuit 31 and the A / D conversion circuit 32, and their difference values are compared and shown.

[0065] In FIGS. 10 and 11, in the conventional configuration [2], the main ground 51a of the power system and the ground terminal 61 are separated from the main ground 51b of the signal system and the ground terminal 62. Therefore, it is not affected by the current I flowing through the main ground 51a. Also, since the current I1 flowing through the main ground 51b of the signal system is sufficiently smaller than the current I (that is, I1 << I), the potential difference between the ground potentials V G1 , V G2 hardly occurs (that is, I1 × R0 ≒ 0). That is, the ground potentials V G1 , V G2 do not fluctuate, and the difference value is V G1 -V G2 ≒ 0, but the wiring and circuit layout, etc. are restricted.

[0066] On the other hand, in the conventional configuration [3], the I / V conversion circuit 31 and the A / D conversion circuit 32 are connected to the common main ground 51 and the ground terminal 6 by the sub-ground wirings 52a and 52b, respectively, so that the ground potential V G1 , V G2 That is, the potential of the sub-ground wiring 52a, which is connected to the main ground 51 at a position farther from the ground terminal 6, becomes higher than the potential of the sub-ground wiring 52b, which is closer, and the ground potential V G1 and the ground potential V of the A / D conversion circuit 32. G1 Between 52b, the potential difference (V G1 -V G2 ) occurs. This causes a delay in the transfer of signals between the I / V conversion circuit 31 and the A / D conversion circuit 32, resulting in a decrease in detection accuracy.

[0067] In contrast, in the configuration [1] of this embodiment, the I / V conversion circuit 31 and the A / D conversion circuit 32 are connected to the main ground 51 at one point by the sub-ground wiring 52, so there is no potential difference due to the connection position as in the conventional configuration [3]. In other words, the current I flowing through the common main ground 51 causes the ground potential V G1 , V G2 Although the ground potential V fluctuates, the grounds are connected to each other by an independent ground connection wiring 521, so the ground potential V G1 , V G2 are equivalent, and no potential difference occurs (i.e., I1 × R0 ≒ 0). Therefore, it is possible to improve detection accuracy while ensuring freedom of layout.

[0068] 12 shows the effect of the configuration [1] of this embodiment, and shows the time transition when the NOx concentration is continuously detected by the signal processing unit 3 in the sensor control circuit 1 based on the detected current signal from the sensor element 2. The I / V conversion circuit 31 and the A / D conversion circuit 32 are connected by a ground connection wiring 521 having a predetermined wiring resistance, and the heater 25 of the sensor element 2 is turned on and off at predetermined intervals using the heater control circuit 41, to investigate the effect that fluctuations in the potential of the main ground 51 have on the NOx detection result.

[0069] For comparison, FIG. 13 shows the ground potential V G1 , V G2 The time transition of the NOx detection result was examined under the same conditions when a deviation occurred. The conditions for energizing the heater by the energization control unit 4 and the wiring resistance of the ground connection wiring 521 were as follows. [conditions] Heater current: 2A Wiring resistance of ground connection wire 521: 0.8 mΩ

[0070] From the results of FIG. 12, it can be seen that the NOx detection result fluctuates over time, but when the average value of the NOx concentration when the heater is on and the average value of the NOx concentration when the heater is off are calculated, no substantial difference is found. This is because, in the configuration of the ground wiring part 5 of this embodiment, the heater current does not change the ground potential V G1 , V G2 This shows that even if the voltage fluctuates, the reference potential does not shift and therefore the NOx detection result is hardly affected.

[0071] On the other hand, the results in Figure 13 show that the NOx detection results fluctuate significantly in either an increasing or decreasing direction when the heater is on or off, resulting in a difference of approximately 10 ppm between the on-average and off-average. This fluctuation can be calculated, for example, by calculating the deviation in the reference potential from V = RI as follows, and then converting it into an NOx value using the detection error (0.15 mV / ppm) due to the difference in the reference potential: Detection error due to difference in reference potential: 0.15mV / ppm Reference potential deviation = 2A x 0.8mΩ = 1.6mV Deflection amount (detection error) = 1.6 mV ÷ 0.15 mV / ppm ≒ 10 ppm

[0072] (Embodiment 2) A second embodiment of the circuit device will be described with reference to FIGS. In the first embodiment described above, an example configuration was shown in which each circuit and the ground wiring section 5 were arranged on one surface of the circuit board 10, but as shown in Fig. 14, the circuit board 10 may be a double-sided board 10a. For convenience, Fig. 14 shows two surfaces 101a and 102a of the double-sided board 10a stacked one above the other, with the upper surface being designated as the front surface 101a and each circuit, including the multiple analog signal circuits 3A, being arranged on that surface. The other surface, the lower surface, is designated as the back surface 102a and the main ground 51 of the ground wiring section 5 is arranged on that surface.

[0073] On the front surface 101a of the double-sided substrate 10a, there are arranged the circuits 31 to 34 of the signal processing unit 3, including the analog signal circuit 3A, the heater control circuit 41 of the power supply control unit 4, and the power supply circuit 11. The arrangement of the circuits on the front surface 101a is not particularly limited, and here, the arrangement is the same as that shown in FIG. 7 above, except that the arithmetic circuit 33 and the power supply circuit 11 are swapped. That is, the I / V conversion circuit 31 and the A / D conversion circuit 32, which are the multiple analog signal circuits 3A, are arranged adjacent to each other and connected via a signal line La formed on the front surface 101a, and the ground sections 31g and 32g are connected by a ground connection wiring 521. The arithmetic circuit 33 is arranged adjacent to the A / D conversion circuit 32, and the power supply circuit 11 is arranged opposite to it.

[0074] A ground pattern is formed over the entire back surface 102a of the double-sided substrate 10a, constituting a main ground 51, and the circuits on the front surface 101a are connected by sub-ground wiring 52 to 55. In this case, the sub-ground wiring 52 to 55 are formed of conductors arranged to penetrate the double-sided substrate 10a, and are connected to the circuit grounds of the circuits 31 to 34 of the signal processing unit 3. In addition, the circuit ground of the heater control circuit 41 is connected to the main ground 51 by ground connection wiring 51c arranged to penetrate the double-sided substrate 10a.

[0075] As another example shown in Fig. 15, the circuit board 10 may be a multilayer board 10b. For convenience, Fig. 15 shows three layers 101b, 102b, and 103b of the three-layer multilayer board 10b stacked one on top of the other, with the layers being designated from top to bottom as the surface layer 101b, the inner layer 102b, and the back layer 103b. Here, the circuits including the multiple analog signal circuits 3A are arranged on the surface layer 101b, and the main ground 51 is arranged on a different layer, the inner layer 102b.

[0076] In this example, the front surface 101a of the front surface layer 101b is provided with the circuits 31-34 of the signal processing unit 3 including the analog signal circuit 3A, the heater control circuit 41 of the power supply control unit 4, and the power supply circuit 11. The arrangement of these circuits is the same as that shown in FIG. 14 above, and they are connected to the main ground 51, the sub-ground wires 52-55, and the ground connection wire 51c of the ground wiring unit 5 formed on substantially the entire surface of the inner surface layer 102b. The circuits formed on the back surface layer 103b are not particularly limited, and are not shown here.

[0077] In this way, the circuit board 10 may be a double-sided board 10a or a multilayer board 10b, which improves the degree of freedom in wiring and circuit layout. Furthermore, by arranging the main ground 51 on a surface or layer different from the surface 101a of the double-sided board 10a or the surface layer 101b of the multilayer board 10b, where the circuits are arranged, the wiring constraints on the sub-ground wiring 52-55 and the ground connection wiring 51c are reduced, and wiring resistance is reduced by wiring the shortest distance. Furthermore, by arranging the main ground 51 on the inner surface layer 102b of the multilayer board 10b, the influence of external noise is reduced, which is advantageous for improving detection accuracy.

[0078] (Embodiment 3) A second embodiment of the circuit device will be described with reference to FIGS. In each of the above embodiments, the I / V conversion circuit 31 and the A / D conversion circuit 32, which are the multiple analog signal circuits 3A, are arranged adjacent to each other on the circuit board 10, the double-sided board 10a, or the multilayer board 10b. However, they do not necessarily have to be adjacent to each other. For example, as shown in Fig. 16, an arithmetic circuit 33 may be arranged between the I / V conversion circuit 31 and the A / D conversion circuit 32. In this case, too, it is sufficient that the ground sections 31g and 32g of these circuits are connected by independent ground connection wiring 521.

[0079] 17, the A / D conversion circuit 32 may be built into the microcomputer 12. In this case, the ground section 32g of the A / D conversion circuit 32 is substantially the same as the ground of the microcomputer 12. The microcomputer 12 also has a built-in arithmetic circuit 33 (not shown).

[0080] In these configurations, the wiring resistance value of the ground connection wiring 521 connecting the ground parts 31g and 32g of the I / V conversion circuit 31 and the A / D conversion circuit 32 is appropriately set, and the ground potential V G1 , V G2 It is preferable to make the influence of deviations in the above-mentioned range small enough.

[0081] 18, there is a correlation between the wiring length and wiring width of the ground connection wiring 521 and the wiring resistance value, and the shorter the wiring length or the wider the wiring width, the lower the wiring resistance value. Here, in order to perform NOx detection based on the detection current signal from the sensor element 2 with high accuracy, the wiring resistance value can be set so that the detection error falls within a predetermined tolerance range (for example, 1 ppm or less) based on the current value (I) flowing between the grounds of the I / V conversion circuit 31 and the A / D conversion circuit 32 in the sensor control circuit 1 and the voltage value (V) generated between the grounds.

[0082] Specifically, the current value (I) flowing between grounds is set as follows based on the maximum current value required when the I / V conversion circuit 31 and the A / D conversion circuit 32 transmit signals: Also, the voltage value (V) generated between grounds is set as follows so that the detection error due to deviation of the reference potential is kept below 1 ppm. Current flowing between grounds (I): 4mA Voltage between grounds (V): 0.1mV or less In this case, since R=V / I (≦0.1 m / 4 mA=25 mΩ), it is preferable that the wiring resistance value of the ground connection wiring 521 is 25 mΩ or less.

[0083] 18 was calculated using the following formula. The wiring material was copper, and the resistivity and wiring thickness were set to the values shown below. In this case, it is desirable to set the wiring length and wiring width of the ground connection wiring 521 appropriately depending on the wiring and circuit layout, etc., so that the wiring resistance value is 25 mΩ or less. Wiring resistance value = resistivity × (wiring length / wiring length × wiring thickness) Resistivity (copper): 1.72×10 8 Ω m Wiring thickness: 35 μm

[0084] In each of the above circuit devices, the signal processing unit 3, which processes a minute current signal from the sensor element 2, and the current control unit 4, through which a large current flows due to heater drive, are coexist on the circuit board 10, and this configuration makes it possible to improve detection accuracy while suppressing the effects of large current. Furthermore, since the ground wiring unit 5 shares the main ground 51, there are fewer restrictions on circuit layout and wiring, and there is no need to provide multiple ground terminals 6 for external connection. Therefore, when used for sensor control, etc., it is possible to achieve both compactness and high-precision detection.

[0085] The present disclosure is not limited to the above-described embodiments and can be applied to various embodiments without departing from the spirit and scope of the present disclosure. For example, in the above-described embodiments, an example was shown in which the circuit device was applied to a sensor control circuit 1 of a NOx sensor, but the circuit device may be applied to various gas sensors other than NOx sensors. Furthermore, the circuit configuration of the sensor control circuit 1, the connection structure with an external device, and the like can be changed as desired depending on the application, etc.

[0086] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure. Examples of the form are shown below. Section 1. A circuit device (1) is provided on a circuit board (10), the circuit device (1) including: a signal processing unit (3) for processing an input current signal (Iin); a current control unit (4) through which a current (I) larger than the current signal flows; and a ground wiring unit (5) connected to a ground terminal (6), The signal processing unit includes a plurality of analog signal circuits (3A) connected via analog signal lines (La), the ground wiring section has a main ground (51) common to the signal processing section and the current control section, and a plurality of sub-ground wirings (52 to 55) connected to the main ground, The ground sections (31g, 32g) of the analog signal circuits are connected to each other by a ground connection wiring (521), and are also connected to the main ground via the same sub-ground wiring, The potential of the main ground varies in accordance with the operation of the current control unit, The ground potential (V G1 、V G2 ) is provided by the main ground connected via the same sub-ground wiring. Section 2. Item 2. The circuit device according to item 1, wherein the ground connection wiring is an independent wiring that selectively connects the ground sections of the plurality of analog signal circuits. Section 3. 3. The circuit device according to item 1 or 2, wherein the plurality of analog signal circuits include an I / V conversion circuit (31) and an A / D conversion circuit (32), the I / V conversion circuit converting the current signal, which is an analog signal, into a voltage signal, and the A / D conversion circuit converting the voltage signal into a digital signal and outputting it to an arithmetic circuit (33) of the signal processing unit. Section 4. 4. The circuit device according to item 3, wherein the A / D conversion circuit is provided independently of a digital signal circuit (3B) including the arithmetic circuit (33), and is disposed adjacent to the I / V conversion circuit. Section 5. 5. The circuit device according to any one of items 1 to 4, wherein the current signal is a detected current signal of a sensor element (2) provided outside the circuit board, and the power supply control unit includes a heater control circuit (41) that controls power supply to a heater (25) built into the sensor element. Section 6. The circuit device according to any one of items 1 to 5, wherein the circuit board is a double-sided board (10a), and the ground connection wiring is formed on a surface (101a) on which the plurality of analog signal circuits are arranged, and is connected to the main ground arranged on a surface (102a) different from the surface (101a) by the ground connection wiring arranged to penetrate the double-sided board. Section 7. The circuit device according to any one of items 1 to 5, wherein the circuit board is a multi-layer board (10b), and the ground connection wiring is arranged on a layer (101b) on which the plurality of analog signal circuits are arranged, and is connected to the main ground arranged on a layer (102b) different from the layer by the ground connection wiring arranged to penetrate the layer. Section 8. 8. The circuit device according to any one of items 1 to 7, wherein the wiring resistance value of the ground connection wiring is set to 25 mΩ or less.

Claims

1. A circuit device (1) is provided on a circuit board (10) with a signal processing section (3) for processing an input current signal (Iin), a current control section (4) through which a current (I) larger than the current signal flows, and a ground wiring section (5) connected to a ground terminal (6), The signal processing unit includes a plurality of analog signal circuits (3A) connected via analog signal lines (La), the ground wiring section has a main ground (51) common to the signal processing section and the current control section, and a plurality of sub-ground wirings (52 to 55) for connecting a circuit of the signal processing section to the main ground, The plurality of analog signal circuits include an I / V conversion circuit (31) that converts the current signal, which is an analog signal, into a voltage signal, and an A / D conversion circuit (32) that converts the voltage signal into a digital signal and outputs it to an arithmetic circuit (33) of the signal processing unit, the A / D conversion circuit is provided independently of the digital signal circuit (3B) including the arithmetic circuit, and is disposed adjacent to the I / V conversion circuit; The ground sections (31g, 32g) of the I / V conversion circuit and the A / D conversion circuit are selectively connected by a ground connection wiring (521) which is an independent wiring, and the ground connection wiring is connected to the main ground via the same sub-ground wiring, The potential of the main ground varies in accordance with the operation of the current control unit, The ground potential (V Ｇ１ , V Ｇ２ The potential of the ground connection wiring that provides the sub-ground varies together with the potential of the main ground that is connected via the same sub-ground wiring.

2. The current signal is a detection current signal of a sensor element (2) provided outside the circuit board, and the current control unit includes a heater control circuit (41) that controls current flow to a heater (25) built into the sensor element, as described in claim 1.

3. A circuit device as described in claim 1 or 2, wherein the circuit board is a double-sided board (10a), and the ground connection wiring is formed on the surface (101a) on which the plurality of analog signal circuits are arranged, and is connected to the main ground arranged on a surface (102a) different from the surface (101a) by the ground connection wiring arranged to penetrate the double-sided board.

4. A circuit device as described in claim 1 or 2, wherein the circuit board is a multilayer board (10b), and the ground connection wiring is arranged on a layer (101b) on which the plurality of analog signal circuits are arranged, and is connected to the main ground arranged on a layer (102b) different from the layer by the ground connection wiring arranged to penetrate the layer.

5. A circuit device as described in claim 1 or 2, wherein the wiring resistance value of the ground connection wiring is set to 25 mΩ or less.

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