Ad conversion system

Abstract

This AD conversion system (1) comprises: an AD converter (10) that converts an analog signal input from an input path (25) into a digital signal and outputs the digital signal to an output path (26); a first element unit (11) electrically connected to the input path (25); and a second element unit (12) electrically connected to the input path (25). The first element unit (11): switches between a first operation state in which a voltage corresponding to a detection target, which is a detection target voltage or a detection target current, is output to the input path (25) side, and a first stop state in which the output of the voltage corresponding to the detection target is stopped; and outputs a first reference voltage in the first stop state. The second element unit (12) switches between a second operation state in which a second reference voltage different from the first reference voltage is output to the input path (25) side, and a second stop state in which the output of the second reference voltage is stopped.

Description

AD conversion system

[0001] The present disclosure relates to an AD conversion system.

[0002] Patent Document 1 discloses an abnormality detection device for an AD converter. This abnormality detection device selectively outputs a first reference voltage or a second reference voltage using a first multiplexer, and selectively outputs the voltage output from the first multiplexer and a voltage input to an input terminal using a second multiplexer. This abnormality detection device detects an abnormality based on the output value of the AD converter when the first reference voltage or the second reference voltage is input to the AD converter.

[0003] A configuration in which a first reference voltage (power supply voltage) and a second reference voltage (ground voltage) are selectively input to an AD converter using a multiplexer is also disclosed in Japanese Patent Laid-Open No. 2003-222999.

[0004] JP-A-8-56160 JP-A-8-330959

[0005] In the configurations of Patent Documents 1 and 2, a multiplexer is required to input the first reference voltage and the second reference voltage to the AD converter.

[0006] An object of the present disclosure is to provide a technique that allows selective input of a first reference voltage and a second reference voltage to an AD converter without using a multiplexer.

[0007] The AD conversion system of the present disclosure comprises an AD converter that converts an analog signal input from an input path into a digital signal and outputs the digital signal to an output path; a first element unit electrically connected to the input path; and a second element unit electrically connected to the input path, wherein the first element unit switches between a first operating state in which it outputs a voltage corresponding to a detection target, which is a detection target voltage or a detection target current, to the input path, and a first stop state in which it stops outputting the voltage corresponding to the detection target, and outputs a first reference voltage in the first stop state; and the second element unit switches between a second operating state in which it outputs a second reference voltage different from the first reference voltage to the input path, and a second stop state in which it stops outputting the second reference voltage.

[0008] The technology according to the present disclosure can selectively input the first reference voltage and the second reference voltage to the AD converter without using a multiplexer.

[0009] FIG. 1 is a schematic diagram illustrating the configuration of an AD conversion system according to a first embodiment. FIG. 2 is a timing chart illustrating the first and second determination processes performed under normal conditions. FIG. 3 is a timing chart illustrating the first and second determination processes performed in a state where an abnormality has occurred in which the output value of the AD converter is fixed near the median value. FIG. 4 is a timing chart illustrating the first and second determination processes performed in a state where an abnormality has occurred in which the output value of the AD converter is fixed at the maximum value. FIG. 5 is a schematic diagram illustrating the configuration of an AD conversion system according to a second embodiment. FIG. 6 is a schematic diagram illustrating the configuration of an AD conversion system according to a third embodiment. FIG. 7 is a schematic diagram illustrating the configuration of an AD conversion system according to a fourth embodiment.

[0010] [Description of Embodiments of the Present Disclosure] In the following, embodiments according to the present disclosure are listed and exemplified.

[0011] [1] An AD conversion system comprising: an AD converter that converts an analog signal input from an input path into a digital signal and outputs the digital signal to an output path; a first element unit electrically connected to the input path; and a second element unit electrically connected to the input path, wherein the first element unit switches between a first operating state in which it outputs a voltage corresponding to a detection target, which is a detection target voltage or a detection target current, to the input path, and a first stop state in which it stops outputting the voltage corresponding to the detection target, and outputs a first reference voltage in the first stop state; and the second element unit switches between a second operating state in which it outputs a second reference voltage different from the first reference voltage to the input path, and a second stop state in which it stops outputting the second reference voltage.

[0012] With this configuration, the first element unit switches between a first operating state and a first stopped state, so that a voltage corresponding to the detection target and the first reference voltage can be selectively applied to the input path. Furthermore, when the second element unit is in the second operating state, the second reference voltage can be applied to the input path. In other words, with this configuration, the first reference voltage and the second reference voltage can be selectively input to the AD converter without using a multiplexer.

[0013] [2] The AD conversion system described in [1], wherein the first element unit has a first resistor unit that electrically connects the input path to ground and outputs a ground voltage as the first reference voltage when in the first stop state.

[0014] This configuration simplifies the configuration of the first element unit, and also allows the ground voltage to be applied to the input path as the first reference voltage when the first element unit is in the first stopped state and the second element unit is in the second stopped state.

[0015] [3] The AD conversion system described in [2], wherein the first element unit has a second resistor unit that divides the voltage to be detected together with the first resistor unit, and when in the first operating state, outputs a voltage obtained by dividing the voltage to be detected by the first resistor unit and the second resistor unit to the input path side.

[0016] According to this configuration, the voltage to be detected can be divided by the first resistor section and the second resistor section, and the divided voltage can be applied to the input path.

[0017] [4] The AD conversion system according to [3], wherein the voltage to be detected is the output voltage of a high-voltage battery mounted on a vehicle.

[0018] According to this configuration, the voltage of the high-voltage battery applied to the first conductive path can be reduced by dividing the voltage by the first resistor portion and the second resistor portion.

[0019] [5] An AD conversion system described in any one of [2] to [4], wherein the first element unit has a first switch unit arranged between a first conduction path to which the voltage to be detected is applied and the input path, and is in the first operating state when the first switch unit is in an on state, and in the first stopped state when the first switch unit is in an off state.

[0020] According to this configuration, the first element unit switches between a first operating state and a first stopped state by switching the on / off state of the first switch unit, thereby simplifying the configuration for switching the first element unit between the first operating state and the first stopped state.

[0021] [6] An AD conversion system described in any one of [2] to [5], wherein the second element unit has a second switch unit arranged between a second conduction path to which a power supply voltage of the AD converter is applied and the input path, and when the second switch unit is in an on state, it is in the second operating state, and when the second switch unit is in an off state, it is in the second stopped state, and when in the second operating state, it outputs the power supply voltage of the AD converter as the second reference voltage.

[0022] With this configuration, the second element unit switches between the second operating state and the second stopped state by switching the on / off state of the second switch unit, thereby simplifying the configuration for switching the second element unit between the second operating state and the second stopped state. Furthermore, with this configuration, when the second element unit is in the second operating state, the power supply voltage of the AD converter can be applied to the input path as the second reference voltage. In other words, with this configuration, it is possible to simplify the configuration in which the ground voltage is applied to the input path as the first reference voltage and the power supply voltage of the AD converter is applied to the input path as the second reference voltage.

[0023] [7] The AD conversion system described in [1], wherein the first element unit has a differential amplifier circuit that outputs a voltage corresponding to the current to be detected, and is in the first operating state when the differential amplifier circuit is operating and the current to be detected is not interrupted, and is in the first stopped state when the differential amplifier circuit is stopped and the current to be detected is interrupted.

[0024] With this configuration, a voltage corresponding to the current to be detected can be output when the differential amplifier circuit is operating and the current to be detected is not interrupted, and a first reference voltage can be output when the differential amplifier circuit is stopped and the current to be detected is interrupted.

[0025] [8] An AD conversion system described in any one of [1] to [7], comprising a control unit that controls the first element unit and the second element unit, wherein the control unit performs a first determination process of determining an abnormality based on a digital signal output to the output path while controlling the first element unit and the second element unit so that the first reference voltage is applied to the input path, and a second determination process of determining an abnormality based on a digital signal output to the output path while controlling the first element unit and the second element unit so that the second reference voltage is applied to the input path.

[0026] With this configuration, the first and second reference voltages can be applied to the input path in sequence by controlling the first and second element units, and the control unit can determine whether an abnormality has occurred based on the digital signal generated when the first and second reference voltages are applied to the input path.

[0027] [9] An AD conversion system as described in [6], comprising a control unit that controls the first element unit and the second element unit, wherein the control unit performs a first determination process that determines an abnormality based on a digital signal output to the output path when the first element unit is controlled to the first stopped state and the second element unit is controlled to the second stopped state, and a second determination process that determines an abnormality based on a digital signal output to the output path when the second element unit is controlled to the second operating state.

[0028] With this configuration, the first and second reference voltages can be applied to the input path in sequence by controlling the first and second element units, and the control unit can determine whether an abnormality has occurred based on the digital signal generated when the first and second reference voltages are applied to the input path.

[0029]

[10] An AD conversion system described in any one of [1] to [7], comprising a control unit that controls the second element unit, wherein the control unit performs a process of determining the state of the first element unit, and when it determines that the first element unit is in the first stopped state, performs a first determination process of determining an abnormality based on the digital signal output to the output path while controlling the second element unit to the second stopped state, and a second determination process of determining an abnormality based on the digital signal output to the output path while controlling the second element unit to the second operating state.

[0030] When the control unit determines that the first element unit is in the first stopped state, the control unit controls the second element unit to a second stopped state to apply a first reference voltage to the input path, and controls the second element unit to a second operating state to apply a second reference voltage to the input path. The control unit can determine an abnormality based on a digital signal when the first reference voltage and the second reference voltage are applied to the input path.

[0031] [Details of the embodiments of the present disclosure] 1. First embodiment 1-1. Configuration of AD conversion system 1 The AD conversion system 1 is mounted on, for example, a vehicle. The AD conversion system 1 includes an AD converter 10, a first element unit 11, a second element unit 12, and a control unit 13.

[0032] The AD converter 10 converts an analog signal input from an input path 25 into a digital signal and outputs the digital signal to an output path 26 .

[0033] The first element unit 11 is electrically connected to the input path 25. The first element unit 11 switches between a first operating state in which it outputs a voltage corresponding to the voltage to be detected to the input path 25, and a first stopped state in which it stops outputting the voltage corresponding to the voltage to be detected. In the first stopped state, the first element unit 11 outputs a first reference voltage.

[0034] The first element portion 11 has a first resistor portion 11A, a second resistor portion 11B, and a first switch portion 11C.

[0035] The first resistance portion 11A is configured by a resistor. The first resistance portion 11A electrically connects the input path 25 to the ground G. One end of the first resistance portion 11A is electrically connected to the input path 25. The other end of the first resistance portion 11A is electrically connected to the ground G.

[0036] The second resistor 11B is formed of a resistor. The second resistor 11B and the first resistor 11A form a voltage divider circuit that divides the voltage to be detected. One end of the second resistor 11B is electrically connected to one end of the first resistor 11A and to the input path 25 via the first switch 11C. The other end of the second resistor 11B is electrically connected to the first conductive path 21 to which the voltage to be detected is applied. The voltage to be detected is the output voltage of a high-voltage battery B mounted on the vehicle.

[0037] The first switch unit 11C may be configured as a mechanical switch or a semiconductor switch. The first switch unit 11C is provided between the first conductive path 21 and the input path 25. In this embodiment, the first switch unit 11C is provided between the second resistor unit 11B and the input path 25. The first element unit 11 is in a first operating state when the first switch unit 11C is turned on, and in a first stopped state when the first switch unit 11C is turned off.

[0038] In the first operating state, the first element unit 11 outputs a voltage corresponding to the voltage to be detected to the input path 25. In the first operating state, the first element unit 11 outputs a voltage obtained by dividing the voltage to be detected by the first resistor unit 11A and the second resistor unit 11B to the input path 25. In the first stopped state, the first element unit 11 outputs a ground voltage as a first reference voltage to the input path 25.

[0039] The second element unit 12 is electrically connected to the input path 25. The second element unit 12 switches between a second operating state in which it outputs a second reference voltage, different from the first reference voltage, to the input path 25, and a second stopped state in which it stops outputting the second reference voltage. The second element unit 12 includes a second switch unit 12A. The second switch unit 12A may be configured as a mechanical switch or a semiconductor switch. The second switch unit 12A is provided between the input path 25 and a second conduction path 22 to which the power supply voltage (VCC) of the AD converter 10 is applied. One end of the second switch unit 12A is electrically connected to the second conduction path 22. The other end of the second switch unit 12A is electrically connected to the input path 25. The second element unit 12 is in the second operating state when the second switch unit 12A is turned on, and in the second stopped state when the second switch unit 12A is turned off. The second element section 12 outputs the power supply voltage of the AD converter 10 as the second reference voltage in the second operating state, and stops outputting the second reference voltage in the second stopped state.

[0040] When the first element unit 11 is in the first operating state and the second element unit 12 is in the second stopped state, a voltage corresponding to the voltage to be detected is applied to the input path 25. When the first element unit 11 is in the first stopped state and the second element unit 12 is in the second stopped state, a first reference voltage is applied to the input path 25. When the second element unit 12 is in the second operating state, a second reference voltage is applied to the input path 25.

[0041] The control unit 13 is configured by, for example, a microcontroller. The control unit 13 receives the digital signal output from the output path 26. The control unit 13 controls the first element unit 11 and the second element unit 12. The control unit 13 controls the first element unit 11 to a first operating state by controlling the first switch unit 11C to an on state. The control unit 13 controls the first element unit 11 to a first stopped state by controlling the first switch unit 11C to an off state. The control unit 13 controls the second element unit 12 to a second operating state by controlling the second switch unit 12A to an on state. The control unit 13 controls the second element unit 12 to a second stopped state by controlling the second switch unit 12A to an off state.

[0042] The control unit 13 performs a first determination process to determine whether an abnormality exists based on a digital signal output to the output path 26 while controlling the first element unit 11 and the second element unit 12 so that a first reference voltage is applied to the input path 25. Specifically, in the first determination process, the control unit 13 determines whether an abnormality exists based on a digital signal output to the output path 26 when the first element unit 11 is controlled to a first stopped state and the second element unit 12 is controlled to a second stopped state.

[0043] The control unit 13 performs a second determination process to determine whether an abnormality exists based on the digital signal output to the output path 26 while controlling the first element unit 11 and the second element unit 12 so that a second reference voltage is applied to the input path 25. Specifically, in the second determination process, the control unit 13 determines whether an abnormality exists based on the digital signal output to the output path 26 when the first element unit 11 is controlled to the first operating state and the second element unit 12 is controlled to the second operating state.

[0044] 1-2. Example of Operation of the AD Conversion System 1 FIG. 2 shows a timing chart illustrating the first and second determination processes performed under normal conditions. In FIG. 2, at timing t0, the first element unit 11 is in the first operating state, and the second element unit 12 is in the second stopped state. That is, a voltage corresponding to the voltage to be detected is applied to the input path 25 of the AD converter 10. The control unit 13 then starts the first determination process, and at timing t1, switches the first element unit 11 to the first stopped state while maintaining the second element unit 12 in the second stopped state. This causes the input voltage of the AD converter 10 to become the ground voltage (0 V). In this state, the control unit 13 determines an abnormality based on the digital signal. For example, the control unit 13 determines an abnormality when the value indicated by the digital signal deviates from a predetermined ideal value (e.g., 0) or when the difference between the value indicated by the digital signal and the ideal value (e.g., 0) exceeds the normal value. In the example shown in FIG. 2, the value indicated by the digital signal is 0, so the control unit 13 determines that the AD converter 10 is normal. After determining whether or not there is an abnormality, the control unit 13 returns the first element unit 11 to the first operating state at timing t2, and ends the first determination process.

[0045] The control unit 13 then begins a second determination process, and at timing t3, switches the second element unit 12 to the second operating state while maintaining the first element unit 11 in the first operating state. This causes the input voltage of the AD converter 10 to become the power supply voltage (VCC). In this state, the control unit 13 determines an abnormality based on the digital signal. For example, the control unit 13 determines an abnormality when the value indicated by the digital signal deviates from a predetermined ideal value (e.g., maximum value (MAX)) or when the difference between the value indicated by the digital signal and the ideal value (e.g., maximum value (MAX)) exceeds a normal value. In the example shown in FIG. 2 , the value indicated by the digital signal is the maximum value (MAX), so the control unit 13 determines an abnormality. After determining whether or not an abnormality exists, the control unit 13 returns the second element unit 12 to the second stopped state at timing t4, thereby terminating the second determination process.

[0046] 3 shows a timing chart illustrating the first and second determination processes performed when an abnormality occurs in which the output value of the AD converter 10 is fixed near the median value. In FIG. 3 , upon start of the first determination process, at timing t11, the first element unit 11 switches to the first stopped state while the second element unit 12 remains in the second stopped state, and the input voltage of the AD converter 10 becomes the ground voltage (0 V). However, the output value of the AD converter 10 remains fixed near the median value. Therefore, the control unit 13 determines that an abnormality exists. After determining whether or not an abnormality exists, the control unit 13 returns the first element unit 11 to the first operating state at timing t12, thereby terminating the first determination process.

[0047] Thereafter, the control unit 13 starts the second determination process, and at timing t13, switches the second element unit 12 to the second operating state while maintaining the first element unit 11 in the first operating state. As a result, the input voltage of the AD converter 10 becomes the power supply voltage (VCC). However, the output value of the AD converter 10 remains fixed near the median value. For this reason, the control unit 13 determines that an abnormality has occurred. After determining whether or not an abnormality has occurred, the control unit 13 returns the second element unit 12 to the second stopped state at timing t14, and ends the second determination process.

[0048] 4 shows a timing chart illustrating the first and second determination processes performed when an abnormality occurs in which the output value of the AD converter 10 is fixed at its maximum value. In FIG. 4 , upon the start of the first determination process, at timing t21, the first element unit 11 switches to the first stopped state while the second element unit 12 remains in the second stopped state, and the input voltage of the AD converter 10 becomes the ground voltage (0 V). However, the output value of the AD converter 10 remains fixed at its maximum value (MAX). Therefore, the control unit 13 determines that an abnormality has occurred. After determining whether or not an abnormality exists, the control unit 13 returns the first element unit 11 to the first operating state at timing t22, thereby terminating the first determination process.

[0049] Thereafter, the control unit 13 starts the second determination process, and at timing t23, switches the second element unit 12 to the second operating state while maintaining the first element unit 11 in the first operating state. As a result, the input voltage of the AD converter 10 becomes the power supply voltage (VCC). Because the output value of the AD converter 10 is fixed to the maximum value (MAX), this is actually an abnormality. However, the control unit 13 determines that the value indicated by the digital signal is normal because it is the maximum value (MAX). After determining whether or not there is an abnormality, the control unit 13 returns the second element unit 12 to the second stopped state at timing t24, and ends the second determination process.

[0050] 1-3. Examples of Effects of the AD Conversion System 1 As described above, by switching the first element unit 11 between the first operating state and the first stopped state, a voltage corresponding to the voltage to be detected and the ground voltage can be selectively applied to the input path 25. Furthermore, when the second element unit 12 is in the second operating state, the second reference voltage can be applied to the input path. In other words, according to the AD conversion system 1, the first reference voltage and the second reference voltage can be selectively input to the AD converter 10 without using a multiplexer.

[0051] This configuration can simplify the configuration of the first element unit 11. Furthermore, this configuration can apply the ground voltage as the first reference voltage to the input path 25 when the first element unit 11 is in the first stopped state and the second element unit 12 is in the second stopped state.

[0052] According to this configuration, the voltage to be detected can be divided by the first resistor 11A and the second resistor 11B, and the divided voltage can be applied to the input path.

[0053] According to this configuration, the voltage of the high-voltage battery B applied to the first conductive path 21 can be reduced by dividing the voltage by the first resistor portion 11A and the second resistor portion 11B.

[0054] According to this configuration, the first element unit 11 switches between a first operating state and a first stopped state by switching the on / off state of the first switch unit 11C, thereby simplifying the configuration for switching the first element unit 11 between the first operating state and the first stopped state.

[0055] With this configuration, the second element unit 12 switches between the second operating state and the second stopped state by switching the on / off state of the second switch unit 12A, thereby simplifying the configuration for switching the second element unit 12 between the second operating state and the second stopped state. Furthermore, with this configuration, when the second element unit 12 is in the second operating state, the power supply voltage of the AD converter 10 can be applied to the input path 25 as the second reference voltage. In other words, with this configuration, it is possible to simplify the configuration in which the ground voltage is applied to the input path 25 as the first reference voltage and the power supply voltage of the AD converter 10 is applied to the input path 25 as the second reference voltage.

[0056] According to this configuration, the first and second element units 11 and 12 can be controlled to sequentially apply the first and second reference voltages to the input path 25. The control unit 13 can then determine whether an abnormality has occurred based on the digital signal generated when the first and second reference voltages are applied to the input path 25.

[0057] 2. Second Embodiment In the second embodiment, a configuration in which the first element unit is not controlled by the control unit will be described. Note that in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0058] The AD conversion system 201 according to the second embodiment is mounted on, for example, a vehicle. As shown in FIG. 5 , the AD conversion system 201 includes an AD converter 10, a first element unit 211, a second element unit 12, and a control unit 13.

[0059] The first element unit 211 has a first resistor unit 11A and a second resistor unit 11B. The first element unit 211 corresponds to the first element unit 11 described in the first embodiment, except that the first switch unit 11C is removed.

[0060] A changeover switch unit 30 is provided inside or outside the AD conversion system 201. The changeover switch unit 30 is provided between the first conductive path 21 and the high-voltage battery B. The changeover switch unit 30 switches between a permissive state that allows current to flow through the first conductive path 21 and a cutoff state that cuts off current flow through the first conductive path 21. The first element unit 211 is in a first operating state when the changeover switch unit 30 is in an on state, and in a first stopped state when the changeover switch unit 30 is in an off state.

[0061] The control unit 13 controls the second element unit 12. The control unit 13 performs a process of determining whether the first element unit 211 is in a first operating state or a first stopped state. The control unit 13 receives, for example, a state signal SG indicating the state of the first element unit 211 from an external device (for example, a device that controls the changeover switch unit 30) and determines the state of the first element unit 211 based on the state signal SG. If the control unit 13 determines that the first element unit 211 is in the first stopped state, the control unit 13 performs a first determination process of determining an abnormality based on the digital signal output to the output path 26 while controlling the second element unit 12 to the second stopped state. The specific determination method is the same as the method described in the first embodiment.

[0062] The control unit 13 performs a second determination process to determine whether an abnormality has occurred based on the digital signal output to the output path 26 when the second element unit 12 is controlled to be in the second operating state. The timing for performing the second determination process may be when the first element unit 211 is in the first stopped state, or when the first element unit 211 is in the first operating state. The specific determination method is the same as the method described in the first embodiment.

[0063] The AD conversion system 201 of the second embodiment has the following advantages. When the control unit 13 determines that the first element unit 211 is in the first stopped state, the control unit 13 can apply a first reference voltage to the input path 25 by controlling the second element unit 12 to the second stopped state, and can apply a second reference voltage to the input path 25 by controlling the second element unit 12 to the second operating state. The control unit 13 can determine an abnormality based on a digital signal obtained when the first reference voltage and the second reference voltage are applied to the input path 25.

[0064] 3. Third Embodiment In the third embodiment, an example in which the first element unit is configured by an amplifier will be described. Note that in the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0065] The AD conversion system 301 according to the third embodiment is mounted on, for example, a vehicle. As shown in FIG. 6 , the AD conversion system 301 includes an AD converter 10, a first element unit 311, a second element unit 312, and a control unit 13.

[0066] The first element unit 311 is electrically connected to the input path 25. The first element unit 311 switches between a first operating state in which it outputs a voltage corresponding to the current to be detected to the input path 25, and a first stopped state in which it stops outputting the voltage corresponding to the current to be detected. In the first stopped state, the first element unit 311 outputs a first reference voltage.

[0067] The first element unit 311 includes a shunt resistor 311A ​​and an amplifier 311B. The shunt resistor 311A ​​is provided in a conductive path 321 through which the current to be detected flows. The amplifier 311B outputs a voltage corresponding to the voltage across the shunt resistor 311A ​​as a first reference voltage. The voltage corresponding to the voltage across the shunt resistor 311A ​​corresponds to the current to be detected. The amplifier 311B includes a differential amplifier circuit 311C that outputs a voltage corresponding to the current to be detected. The first element unit 311 is in a first operating state when a current flows through the shunt resistor 311A ​​and the differential amplifier circuit 311C is operating. The first element unit 311 is in a first stopped state when the current flowing through the shunt resistor 311A ​​is interrupted and the differential amplifier circuit 311C is stopped. The first element unit 311 outputs a voltage corresponding to the current to be detected in the first operating state and outputs a first reference voltage in the first stopped state.

[0068] The amplifier 311B is a bidirectional current sense amplifier. When no current flows through the shunt resistor 311A, the amplifier 311B outputs a voltage (VCC / 2) that is half the power supply voltage (VCC). That is, the first element unit 311 outputs VCC / 2 as the first reference voltage when in the first stop state. The amplifier 311B outputs a voltage greater than VCC / 2 when the current flowing through the shunt resistor 311A ​​flows in one direction, and outputs a voltage smaller than VCC / 2 when the current flowing through the shunt resistor 311A ​​flows in the other direction. When the current flowing through the shunt resistor 311A ​​flows in one direction, the output value of the amplifier 311B increases as the current value increases. When the current flowing through the shunt resistor 311A ​​flows in the other direction, the output value of the amplifier 311B decreases as the current value increases.

[0069] The second element unit 312 is electrically connected to the input path 25. The second element unit 312 switches between a second operating state in which the second reference voltage is output to the input path 25, and a second stopped state in which the output of the second reference voltage is stopped. The second element unit 312 has a reference voltage circuit 312A that generates the second reference voltage. The second reference voltage may be any voltage different from the first reference voltage, and may be, for example, a ground voltage, a power supply voltage, or some other voltage.

[0070] As in the first embodiment, the control unit 13 controls the first element unit 311 and the second element unit 312 to selectively apply the first reference voltage or the second reference voltage to the input path 25. Then, as in the first embodiment, the control unit 13 determines whether an abnormality has occurred based on the digital signal output from the output path 26. Note that since the first reference voltage is VCC / 2, the ideal value in the first determination process is the median value.

[0071] With this configuration, a voltage corresponding to the current to be detected can be output when the differential amplifier circuit 311C is operating and the current to be detected is not interrupted, and a first reference voltage can be output when the differential amplifier circuit 311C is stopped and the current to be detected is interrupted.

[0072] 4. Fourth Embodiment In the fourth embodiment, a configuration in which the first element unit is not controlled by the control unit will be described, based on the configuration of the third embodiment. Note that in the fourth embodiment, the same components as those in the third embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0073] The AD conversion system 401 according to the fourth embodiment is mounted on, for example, a vehicle. As shown in FIG. 7 , the AD conversion system 401 includes an AD converter 10, a first element unit 311, a second element unit 312, and a control unit 13.

[0074] A changeover switch unit 430 is provided inside or outside the AD conversion system 401. The changeover switch unit 430 switches between an allowable state that allows current to flow through the shunt resistor 311A ​​and a cutoff state that cuts off current flow through the shunt resistor 311A. The first element unit 311 is in a first operating state when the changeover switch unit 430 is in an on state, and in a first stopped state when the changeover switch unit 430 is in an off state.

[0075] The control unit 13 controls the second element unit 312. The control unit 13 performs a process of determining whether the first element unit 311 is in a first operating state or a first stopped state. The control unit 13 receives, for example, a state signal SG indicating the state of the first element unit 311 from an external device (for example, a device that controls the changeover switch unit 430) and determines the state of the first element unit 311 based on the state signal SG. If the control unit 13 determines that the first element unit 311 is in the first stopped state, the control unit 13 performs a first determination process of determining an abnormality based on the digital signal output to the output path 26 while controlling the second element unit 312 to the second stopped state. The specific determination method is the same as in the third embodiment.

[0076] The control unit 13 performs a second determination process to determine whether an abnormality has occurred based on the digital signal output to the output path 26 when the second element unit 312 is controlled to be in the second operating state. The timing for performing the second determination process may be when the first element unit 311 is in the first stopped state or when the first element unit 311 is in the first operating state. The specific determination method is the same as that in the third embodiment.

[0077] The AD conversion system 401 of the fourth embodiment has the following advantages. When the control unit 13 determines that the first element unit 311 is in the first stopped state, the control unit 13 can apply the first reference voltage to the input path 25 by controlling the second element unit 312 to the second stopped state, and can apply the second reference voltage to the input path 25 by controlling the second element unit 312 to the second operating state. The control unit 13 can determine an abnormality based on the digital signal when the first reference voltage and the second reference voltage are applied to the input path 25.

[0078] <Other Embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or below-described embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or below-described embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiments may be modified as follows.

[0079] In each of the above embodiments, the second determination process is performed after the first determination process, but the first determination process may be performed after the second determination process.

[0080] In the first and second embodiments, the second reference voltage does not have to be the power supply voltage of the AD converter, and may be generated by a reference voltage circuit, as in the third embodiment.

[0081] The first reference voltage and the second reference voltage preferably have a relationship in which they are complementary to each other when converted into digital signals, but they do not necessarily have to be complementary to each other.

[0082] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope indicated by the claims or within the scope equivalent to the claims.

[0083] DESCRIPTION OF SYMBOLS 1...AD conversion system 10...AD converter 11...first element section 11A...first resistor section 11B...second resistor section 11C...first switch section 12...second element section 12A...second switch section 13...control section 21...first conductive path 22...second conductive path 25...input path 26...output path 30...changeover switch section 201...AD conversion system 211...first element section 301...AD conversion system 311...first element section 311A...shunt resistor 311B...amplifier 311C...differential amplifier circuit 312...second element section 312A...reference voltage circuit 321...conductive path 401...AD conversion system 430...changeover switch section B...high voltage battery G...ground SG...status signal

Claims

1. An AD conversion system comprising: an AD converter that converts an analog signal input from an input path into a digital signal and outputs the digital signal to an output path; a first element unit electrically connected to the input path; and a second element unit electrically connected to the input path, wherein the first element unit switches between a first operating state in which a voltage corresponding to a detection target, which is a detection target voltage or a detection target current, is output to the input path side, and a first stop state in which the output of the voltage corresponding to the detection target is stopped, and outputs a first reference voltage in the first stop state, and the second element unit switches between a second operating state in which a second reference voltage different from the first reference voltage is output to the input path side, and a second stop state in which the output of the second reference voltage is stopped.

2. The AD conversion system according to claim 1, wherein the first element unit has a first resistance unit that electrically connects the input path to ground, and outputs a ground voltage as the first reference voltage in the first stop state.

3. The AD conversion system according to claim 2, wherein the first element unit has a second resistance unit that divides the detection target voltage together with the first resistance unit, and outputs, to the input path side, a voltage obtained by dividing the detection target voltage by the first resistance unit and the second resistance unit in the first operating state.

4. The AD conversion system according to claim 3, wherein the detection target voltage is an output voltage of a high-voltage battery mounted on a vehicle.

5. The AD conversion system according to any one of claims 2 to 4, wherein the first element unit has a first switch unit provided between a first conductive path to which the detection target voltage is applied and the input path, and enters the first operating state when the first switch unit is in an on state, and enters the first stop state when the first switch unit is in an off state.

6. The AD conversion system according to any one of claims 2 to 4, wherein the second element unit has a second switch unit provided between a second conductive path to which the power supply voltage of the AD converter is applied and the input path, and enters the second operating state when the second switch unit is in an on state, and enters the second stop state when the second switch unit is in an off state, and outputs the power supply voltage of the AD converter as the second reference voltage in the second operating state.

7. The first element unit has a differential amplifier circuit that outputs a voltage corresponding to the current to be detected, and enters the first operating state when the differential amplifier circuit is operating and the current to be detected is not interrupted, and enters the first stop state when the differential amplifier circuit is stopped and the current to be detected is interrupted. The AD conversion system according to claim 1.

8. The AD conversion system according to any one of claims 1 to 4, further comprising a control unit that controls the first element unit and the second element unit, wherein the control unit performs a first determination process for determining an abnormality based on a digital signal output to the output path while controlling the first element unit and the second element unit so that the first reference voltage is applied to the input path, and a second determination process for determining an abnormality based on a digital signal output to the output path while controlling the first element unit and the second element unit so that the second reference voltage is applied to the input path.

9. The AD conversion system according to claim 6, further comprising a control unit that controls the first element unit and the second element unit, wherein the control unit performs a first determination process for determining an abnormality based on a digital signal output to the output path when the first element unit is controlled to be in the first stop state and the second element unit is controlled to be in the second stop state, and a second determination process for determining an abnormality based on a digital signal output to the output path when the second element unit is controlled to be in the second operating state.

10. The AD conversion system according to any one of claims 1 to 4, further comprising a control unit that controls the second element unit, wherein the control unit performs a process of determining the state of the first element unit, and when it is determined that the first element unit is in the first stop state, performs a first determination process for determining an abnormality based on a digital signal output to the output path while controlling the second element unit to be in the second stop state, and a second determination process for determining an abnormality based on a digital signal output to the output path while controlling the second element unit to be in the second operating state.

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