JP6362504B2 - Battery voltage estimation device - Google Patents

Description

  The present invention relates to a battery voltage estimation device that estimates a battery voltage.

  For example, in Patent Document 1, a CPU converts an analog value of a battery voltage applied from an in-vehicle battery into a digital value, and a digital value prepared in advance based on the digital value and an analog value of the battery voltage The analog value of the battery voltage applied from the battery is estimated with reference to the table indicating the correspondence. The estimated analog value of the battery voltage is used for control (for example, system shutdown, reset, etc.) of the in-vehicle device when the power supply is abnormal or for self-diagnosis of the in-vehicle device.

JP 2006-266983 A

  However, the voltage drop amount of the battery voltage applied from the vehicle battery varies depending on the current characteristic or temperature characteristic of the internal element interposed between the connector terminal of the battery and the input port of the CPU. For this reason, even if a table created without considering the current characteristic or temperature characteristic of the internal element as in Patent Document 1 is used, it cannot cope with various actual situations, and the estimation accuracy is poor. It was.

  An object of the present invention is to provide a battery voltage estimation device capable of accurately estimating an analog value of a battery voltage applied from a battery.

The battery voltage estimation device according to the present invention includes a conversion unit, a temperature measurement unit, a current measurement unit, a table group, and an estimation unit. The conversion unit has an internal element interposed between a connector terminal connecting the battery and the input terminal, and converts an analog value of a voltage applied from the connector terminal to the input terminal by the battery from the connector terminal to a digital value. The temperature measurement unit measures the ambient temperature of the internal element. The current measuring unit measures a load current flowing from the battery to the load. The table group is a table for estimation indicating the correspondence between the analog value and the digital value of the battery voltage applied to the connector terminal by the battery, and the internal element voltage that is the load current flowing from the battery to the load and the ambient temperature of the internal element. It has for every fluctuation factor of the amount of descent . The estimation unit refers to the selection table indicating the correspondence between the variation factor of the voltage drop amount of the internal element and the estimation table of the table group, and generates an estimation table that matches the variation factor of the voltage drop amount of the internal element. An analog value of the battery voltage applied to the connector terminal by the battery is estimated by selecting from the table group and referring to the selected estimation table based on the digital value converted by the conversion unit. In this configuration, the estimation unit selects the estimation table that matches the ambient temperature measured by the temperature measurement unit with reference to the selection table and the load current measured by the current measurement unit from the table group, and the selected estimation table Is estimated based on the digital value of the battery voltage converted by the conversion unit, and the analog value of the battery voltage applied from the battery to the connector terminal is estimated.

  According to the present invention, there is an effect that the analog value of the battery voltage applied from the battery can be accurately estimated.

It is a block diagram which shows the structure of the vehicle equipment system to which the battery voltage estimation apparatus which concerns on Embodiment 1 of this invention is applied. It is a figure which shows the example of the table for estimation. 6 is a diagram illustrating an example of a selection table in the first embodiment. FIG. It is a block diagram which shows the structure of the vehicle equipment system to which the battery voltage estimation apparatus which concerns on Embodiment 2 of this invention is applied. FIG. 10 is a diagram illustrating an example of a selection table in the second embodiment. It is a figure which shows the other example of the table for selection in Embodiment 2. FIG. It is a block diagram which shows the structure of the vehicle equipment system to which the battery voltage estimation apparatus which concerns on Embodiment 3 of this invention is applied. FIG. 20 is a diagram illustrating an example of a selection table in the third embodiment. It is a block diagram which shows the structure of the vehicle equipment system to which the battery voltage estimation apparatus which concerns on Embodiment 4 of this invention is applied. FIG. 20 is a diagram illustrating an example of a selection table in the fourth embodiment.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of an in-vehicle device system to which a battery voltage estimation device according to Embodiment 1 of the present invention is applied. In FIG. 1, an in-vehicle device system 1 is a system that is mounted on a vehicle and manages power supply from a battery 2 to electronic devices (such as loads 14 and 16). In the in-vehicle device system 1, the battery 2 is connected to the connector terminal “a”, and is connected to a display 3 and an in-vehicle LAN (Local Area Network) 4 that are used as output destinations of power supply management information. Further, the in-vehicle device system 1 includes a CPU (central processing unit) 11, an in-vehicle LANIF (interface) 12, power supply units 13 and 15, and loads 14 and 16 in which an internal circuit 10 is interposed between a connector terminal a and an AD port b. Is provided.

  As shown in FIG. 1, the internal circuit 10 is provided between the connector terminal a of the in-vehicle device system 1 and the AD port b of the CPU 11, and is composed of internal elements such as a coil, a diode, and a resistor. The internal elements have current characteristics. For example, the voltage drop amount varies depending on the magnitude of the load current flowing from the battery 2 to the loads 14 and 16, and the voltage drop amount of the internal circuit 10 composed of these internal elements also varies. To do.

The CPU 11 functions as the battery voltage estimation device according to the first embodiment. The configuration includes an ADC 110, a table group 111, an estimation unit 112, and a control unit 113.
The ADC 110 is an analog / digital converter having an AD port b as an input terminal. Further, the ADC 110 converts the analog value of the voltage applied from the connector terminal a through the internal circuit 10 to the AD port b which is an input terminal by the battery 2 into a digital value. A numerical value obtained by dividing the maximum value of the input voltage applied to the AD port b by the resolution of the digital processing is defined as a unit voltage, and the digital value is sequentially associated with a value obtained by decreasing the maximum value of the input voltage for each unit voltage. For example, if the maximum value of the input voltage applied to the AD port b is 3.3V and 8-bit processing is possible, the unit voltage is 0.01V because 3.3V / 256 gradations. Digital values 0 to 256 are sequentially assigned to 3.29 V, 3.28 V,..., Where the maximum value 3.3 V of the input voltage is lowered every 0.01 V. When the ADC 110 detects an analog value of the voltage applied to the AD port b, the ADC 110 converts the analog value into a digital value corresponding to the analog value.

The table group 111 is a table group having a plurality of estimation tables for each variation factor of the voltage drop amount of the internal element.
The estimation table is a table showing a correspondence relationship between an analog value and a digital value of the battery voltage applied to the connector terminal a by the battery 2.
The table group 111 is stored in a ROM (Random Access Memory) (not shown) built in the CPU 12, for example.

FIG. 2 is a diagram showing an example of the estimation table, and shows the estimation tables TA, TB, and TC for each variation factor of the voltage drop amount of the internal circuit 10. A / D conversion values D ₁ , D ₂ ,..., D _n are digital values of the battery voltage applied to the AD port b.
For example, 8 in the case of bit A / D conversion, the digital value of 0 to 256 is A / D converted value _{D 1,} D 2, · · ·, assigned as _{D n.}

  The variation factor of the voltage drop amount of the internal circuit 10 is, for example, an operation mode that defines a load current flowing from the battery 2 to the loads 14 and 16. The estimation tables TA, TB, and TC are estimation tables for each operation mode with different load currents. Here, the estimation table TA corresponds to the operation mode A, the estimation table TB corresponds to the operation mode B, and the estimation table TC corresponds to the operation mode C.

The A / D conversion values D ₁ , D ₂ ,..., D _n are values obtained by dividing the maximum value of the input voltage applied to the AD port b by the resolution of the digital processing, and are input to the AD port b. The maximum value of the voltage is assigned to a value that is lowered for each unit voltage. For example, when the maximum value of the input voltage applied to the AD port b by the battery 2 is 3.3 V and 8-bit A / D conversion is performed, the unit voltage is 3.3 V / 256 gradations. A / D conversion values D ₁ , D ₂ ,..., D _{n which} are 0.01 V and are digital values of 0 to 256 are lower than the maximum input voltage 3.3 V at the AD port b for each unit voltage. Each value is assigned.

The battery voltage analog values in the estimation tables TA, TB, and TC are the batteries that are applied to the connector terminal a by the battery 2 when a voltage corresponding to the A / D conversion value is applied to the AD port b. It is an analog value of voltage. That is, this analog value corresponds to the remaining amount of the battery 2 that does not include the voltage drop of the internal circuit 10. An analog value of the battery voltage is obtained in advance by experiment and is associated with the A / D conversion value described above.
For example, in the estimation table TB, the A / D conversion value Dn includes a voltage applied to the AD port b when the battery voltage 16V is applied to the connector terminal a (the voltage of the internal circuit 10 in the operation mode B). Voltage including the drop).

The estimation unit 112 refers to the selection table and selects from the table group 111 an estimation table that matches the variation factor (for example, the current operation mode) of the voltage drop amount of the internal circuit 10.
Further, the estimation unit 112 estimates the analog value of the battery voltage applied to the connector terminal a by the battery 2 by referring to the selected estimation table based on the digital value converted by the ADC 110.
FIG. 3 shows an example of the selection table in the first embodiment, and shows a case where the fluctuation factor of the voltage drop amount of the internal circuit 10 is the operation mode. The selection table 111a shows the correspondence between the operation modes A, B, C,... And the estimation tables TA, TB, TC,.

Since the estimation unit 112 knows which of the operation modes A, B, C,... Is currently set, the current operation mode is referred to by referring to the selection table 111a. It is possible to select a table for guessing that matches.
The selection table 111a is stored in a ROM (not shown) built in the CPU 12, for example. Alternatively, one table data of the table group 111 may be used.

The control unit 113 manages power supply from the battery 2 to the electronic devices (loads 14 and 16) based on the analog value of the battery voltage estimated by the estimation unit 112.
The power supply unit 13 converts the voltage of the battery 2 into a driving voltage for the load 14 and supplies the converted voltage.
Similarly, the power supply unit 15 converts the voltage of the battery 2 into a driving voltage for the load 14 and supplies it.
The loads 14 and 16 are electronic devices that are driven by power supplied from the power supply units 13 and 15. For example, a disk playback device, a wireless communication device, and the like mounted on a vehicle.

Next, the operation will be described.
The ADC 110 converts an analog value of a voltage applied to the AD port b from the connector terminal a through the internal circuit 10 by the battery 2 into a digital value. This digital value is sent to the estimation unit 112. In addition, the estimation unit 112 refers to the selection table 111a and selects an estimation table that matches the current operation mode.

  Next, the estimation unit 112 refers to the estimation table selected as described above based on the digital value converted by the ADC 110, and estimates the analog value of the battery voltage applied to the connector terminal a by the battery 2. To do. The estimated analog value of the battery voltage is sent to the control unit 113.

The control unit 113 manages power supply from the battery 2 to the electronic devices (loads 14 and 16) based on the analog value of the battery voltage estimated by the estimation unit 112.
For example, if the estimated analog value of the battery voltage exceeds a predetermined upper limit value, it is determined that an overvoltage has been applied to the in-vehicle device system 1, and an instruction to stop power supply to the power supply units 13 and 15 is given. To do. Thereby, the load 14 and 16 will be in the state by which the power supply was shut down, and it can prevent generation | occurrence | production of abnormal operation or circuit destruction by overvoltage.
When the estimated analog value of the battery voltage falls below a predetermined lower limit value, it is determined that the voltage applied to the in-vehicle device system 1 has abnormally decreased and, for example, a load is applied to the power supply units 13 and 15. 14 and 16 are instructed to restart.

  The estimation unit 112 may display the analog value of the battery voltage estimated as described above on the display 3 by sending the analog value of the battery voltage to the display 3 via the in-vehicle LANIF 12. Thereby, the user can grasp the state of power supply in the in-vehicle device system 1 via the display 3. The estimated analog value of the battery voltage may be displayed on the display unit of another in-vehicle device via the in-vehicle LAN 4.

As described above, according to the first embodiment, the in-vehicle device system 1 includes the battery voltage estimation device. This battery voltage estimation device is provided as one function of the CPU 11 and includes an ADC 110, a table group 111, and an estimation unit 112. In the ADC 110, an internal circuit 10 is interposed between a connector terminal a that connects the battery 2 and the AD port b, and an analog of a voltage that is applied from the connector terminal a to the AD port b by the battery 2 through the internal circuit 10. Convert the value to a digital value. The table group 111 includes an estimation table indicating a correspondence relationship between an analog value and a digital value of the battery voltage applied to the connector terminal a by the battery 2 for each variation factor of the voltage drop amount of the internal circuit 10. The estimation unit 112 refers to the selection table 111a, selects an estimation table that matches the variation factor of the voltage drop amount of the internal circuit 10 from the table group 111, and converts the selected estimation table into a digital value converted by the ADC 110. Based on this, an analog value of the battery voltage applied to the connector terminal a by the battery 2 is estimated.
By configuring in this way, the battery voltage applied to the connector terminal a by the battery 2 can be estimated according to various fluctuation factors of the voltage drop amount of the internal circuit 10, so that the analog value of the battery voltage is It is possible to estimate with high accuracy.

In the first embodiment, an operation mode that defines a load current that flows from the battery 2 to the loads 14 and 16 as a variation factor of the voltage drop amount of the internal circuit 10 is employed.
The estimation unit 112 refers to the selection table 111a, selects an estimation table suitable for the operation mode from the table group 111, refers to the selected estimation table based on the digital value converted by the ADC 110, and determines the battery 2 Thus, the analog value of the battery voltage applied to the connector terminal a is estimated. By comprising in this way, the battery voltage according to the operation mode can be estimated.

Embodiment 2. FIG.
FIG. 4 is a block diagram showing the configuration of an in-vehicle device system to which the battery voltage estimation device according to Embodiment 2 of the present invention is applied. In FIG. 4, the same components as those in FIG. Similarly to the first embodiment, the in-vehicle device system 1A is a system that is mounted on a vehicle and manages power supply from the battery 2 to electronic devices (such as loads 14 and 16). The in-vehicle device system 1A includes a CPU 11A having an internal circuit 10 interposed between the connector terminal a and the AD port b, an in-vehicle LANIF 12, power supply units 13 and 15, loads 14 and 16, and a temperature measurement circuit 17. The temperature measurement circuit 17 is a temperature measurement unit that measures the ambient temperature of the internal circuit 10.

The CPU 11A is a CPU that functions as the battery voltage estimation device according to the second embodiment, and includes an ADC 110, a table group 111A, an estimation unit 112A, and a control unit 113.
The table group 111 </ b> A has an estimation table for each ambient temperature indicating a correspondence relationship between an analog value and a digital value of the battery voltage applied to the connector terminal a by the battery 2.

The estimation unit 112A refers to a selection table indicating a correspondence relationship between the ambient temperature of the internal circuit 10 and the estimation table of the table group 111A, and is used for estimation that matches the current ambient temperature measured by the temperature measurement circuit 17. A table is selected from the table group 111A.
In addition, the estimation unit 112A estimates the analog value of the battery voltage applied to the connector terminal a by the battery 2 by referring to the selected estimation table based on the digital value converted by the ADC 110.

FIG. 5 shows an example of the selection table in the second embodiment, and shows a case where the fluctuation factor of the voltage drop amount of the internal circuit 10 is the ambient temperature of the internal circuit 10.
The selection table 111b shows a correspondence relationship between the ambient temperature ranges T1, T2, T3,... And the estimation tables TA, TB, TC,.
The estimation unit 112A determines which of the ambient temperature ranges T1, T2, T3,... Is the current ambient temperature measured by the temperature measurement circuit 17, and estimates corresponding to the ambient temperature range of the determination result. Select a table. Thereby, the battery voltage according to the ambient temperature of the internal circuit 10 can be estimated.

Further, the estimation table may be selected based on the operation mode described in the first embodiment and the ambient temperature of the internal circuit 10.
FIG. 6 shows another example of the selection table in the second embodiment, in which the fluctuation factor of the voltage drop amount of the internal circuit 10 is an operation mode in which the load current flowing from the battery 2 to the loads 14 and 16 is defined. The case where it is the ambient temperature of the internal circuit 10 is shown.
The selection table 111c includes the operation modes A, B, C,... And the ambient temperature ranges T1, T2, T3,... And the corresponding estimation tables TA, TB, TC,. The correspondence is shown.
The estimation unit 112A determines which of the ambient temperature ranges T1, T2, T3,... Is the current ambient temperature measured by the temperature measurement circuit 17, and estimates corresponding to the ambient temperature range of the determination result. The table for use is specified, and the table for estimation corresponding to the operation mode currently set in the in-vehicle device system 1A is selected. Thereby, the battery voltage according to the operation mode and the ambient temperature of the internal circuit 10 can be estimated.

  As described above, according to the second embodiment, the in-vehicle device system 1A includes the temperature measurement circuit 17 that measures the ambient temperature of the internal circuit 10, and the fluctuation factor of the voltage drop amount of the internal circuit 10 is the internal circuit. 10 ambient temperature. The estimation unit 112A selects from the table group 111A an estimation table that matches the ambient temperature measured by the temperature measurement circuit 17 based on the selection table 111b, and based on the digital value obtained by converting the selected estimation table by the ADC 110. Thus, an analog value of the battery voltage applied to the connector terminal a by the battery 2 is estimated. With this configuration, it is possible to accurately estimate the battery voltage corresponding to the ambient temperature of the internal circuit 10.

Further, according to the second embodiment, the fluctuation factors of the voltage drop amount of the internal circuit 10 are the operation mode that defines the load current that flows from the battery 2 to the load and the ambient temperature of the internal circuit 10.
The estimation unit 112A selects an estimation table that matches the current operation mode and the ambient temperature measured by the temperature measurement circuit 17 from the table group 111A, and refers to the selected estimation table based on the digital value converted by the ADC 110. Thus, the analog value of the battery voltage applied to the connector terminal a by the battery 2 is estimated. With this configuration, it is possible to accurately estimate the battery voltage corresponding to the operation mode and the ambient temperature of the internal circuit 10.

Embodiment 3 FIG.
FIG. 7 is a block diagram showing a configuration of an in-vehicle device system to which the battery voltage estimation device according to Embodiment 3 of the present invention is applied. In FIG. 7, the same components as those of FIG. Similarly to the first embodiment, the in-vehicle device system 1B is a system that is mounted on a vehicle and manages power supply from the battery 2 to the electronic devices (loads 14, 16 and the like). The in-vehicle device system 1B includes a CPU 11B having an internal circuit 10 interposed between the connector terminal a and the AD port b, an in-vehicle LANIF 12, power supply units 13 and 15, loads 14 and 16, and a current measurement circuit 18. The current measurement circuit 18 is a current measurement unit that is connected to both ends of the current measurement shunt resistor Ra and measures a load current flowing from the battery 2 to the loads 14 and 16.

The CPU 11B is a CPU that functions as a battery voltage estimation device according to the third embodiment, and includes an ADC 110, a table group 111B, an estimation unit 112B, and a control unit 113.
The table group 111 </ b> B has an estimation table for each load current indicating the correspondence between the analog value and the digital value of the battery voltage applied to the connector terminal a by the battery 2.

The estimation unit 112B refers to the selection table indicating the correspondence between the load current flowing from the battery 2 to the loads 14 and 16 and the estimation table of the table group 111B, and matches the load current measured by the current measurement circuit 18. The estimation table is selected from the table group 111B.
Further, the estimation unit 112B estimates the analog value of the battery voltage applied to the connector terminal a by the battery 2 with reference to the selected estimation table based on the digital value converted by the ADC 110.

FIG. 8 shows an example of the selection table in the third embodiment, and shows a case where the fluctuation factor of the voltage drop amount of the internal circuit 10 is a load current flowing from the battery 2 to the loads 14 and 16. The selection table 111d shows the correspondence between the load current ranges IA, IB, IC,... And the estimation tables TA, TB, TC,.
The estimation unit 112B determines whether the load current measured by the current measurement circuit 18 is in the load current range IA, IB, IC,..., And generates an estimation table corresponding to the load current range of the determination result. select. Thereby, the battery voltage according to the load current flowing from the battery 2 to the loads 14 and 16 can be estimated.

As described above, according to the third embodiment, the in-vehicle device system 1B includes the current measurement circuit 18 that measures the load current flowing from the battery 2 to the loads 14 and 16, and changes in the voltage drop amount of the internal circuit 10. The factor is a load current flowing from the battery 2 to the loads 14 and 16.
The estimation unit 112B refers to the selection table 111d and selects an estimation table that matches the load current measured by the current measurement circuit 18 from the table group 111B.
Next, the estimation unit 112B estimates the analog value of the battery voltage applied to the connector terminal a by the battery 2 by referring to the selected estimation table based on the digital value converted by the ADC 110. With this configuration, it is possible to accurately estimate the battery voltage corresponding to the load current flowing from the battery 2 to the loads 14 and 16.
For example, at the time of rising after power-on or disk loading, a so-called transient state occurs in which a voltage drop of the internal circuit 10 is different from that in the steady state.
Even in this case, the battery voltage can be accurately estimated by selecting an appropriate estimation table based on the load current measured by the current measurement circuit 18.

Embodiment 4 FIG.
FIG. 9 is a block diagram showing a configuration of an in-vehicle device system to which the battery voltage estimation device according to Embodiment 4 of the present invention is applied. In FIG. 9, the same components as those in FIG. Similarly to the first embodiment, the in-vehicle device system 1C is a system that is mounted on a vehicle and manages power supply from the battery 2 to electronic devices (such as loads 14 and 16). The in-vehicle device system 1C includes a CPU 11C having an internal circuit 10 interposed between a connector terminal a and an AD port b, an in-vehicle LANIF 12, power supply units 13, 15, loads 14, 16, a temperature measuring circuit 17 and a current measuring circuit 18. Prepare.
The temperature measurement circuit 17 is a temperature measurement unit that measures the ambient temperature of the internal circuit 10.
The current measurement circuit 18 is a current measurement unit that is connected to both ends of the current measurement shunt resistor Ra and measures a load current flowing from the battery 2 to the loads 14 and 16.

The CPU 11C is a CPU that functions as the battery voltage estimation device according to the fourth embodiment, and includes an ADC 110, a table group 111C, an estimation unit 112C, and a control unit 113.
The table group 111 </ b> C has an estimation table indicating the correspondence between the analog value and the digital value of the battery voltage applied to the connector terminal a by the battery 2 for each ambient temperature and load current.

  The estimation unit 112C refers to the selection table indicating the correspondence between the ambient temperature of the internal circuit 10 and the load current flowing from the battery 2 to the loads 14 and 16 and the estimation table of the table group 111C. An estimation table that matches the measured ambient temperature of the internal circuit 10 and the load current measured by the current measurement circuit 18 is selected from the table group 111C. Further, the estimation unit 112 </ b> C refers to the selected estimation table based on the digital value converted by the ADC 110, and estimates an analog value of the battery voltage applied to the connector terminal a by the battery 2.

FIG. 10 shows an example of the selection table according to the fourth embodiment. The variation factor of the voltage drop amount of the internal circuit 10 is the ambient temperature of the internal circuit 10 and the load current flowing from the battery 2 to the loads 14 and 16. Shows the case. 10, the selection table 111e includes an ambient temperature range T1, T2, T3,... And a load current range IA, IB, IC,... And the corresponding estimation tables TA, TB, TC,.・ The correspondence with is shown.
The estimation unit 112C determines which of the load current ranges IA, IB, IC,... Is the load current measured by the current measurement circuit 18, and generates an estimation table corresponding to the load current range of the determination result. Identify. Then, the estimation unit 112C selects an estimation table corresponding to the ambient temperature measured by the temperature measurement circuit 17 from the specified estimation table.
Thereby, the battery voltage according to the load current flowing from the battery 2 to the loads 14 and 16 and the ambient temperature of the internal circuit 10 can be estimated.

As described above, according to the fourth embodiment, the in-vehicle device system 1C includes the temperature measurement circuit 17 that measures the ambient temperature of the internal circuit 10 and the current measurement circuit 18 that measures the load current flowing from the battery 2 to the load. The fluctuation factors of the voltage drop amount of the internal circuit 10 are the load current flowing from the battery 2 to the loads 14 and 16 and the ambient temperature of the internal circuit 10.
The estimation unit 112C refers to the selection table 111e and selects from the table group 111C an estimation table that matches the ambient temperature measured by the temperature measurement circuit 17 and the load current measured by the current measurement circuit 18. Then, the estimation unit 112C estimates the analog value of the battery voltage applied from the battery 2 to the connector terminal a by referring to the selected estimation table based on the digital value of the battery voltage converted by the ADC 110.
With this configuration, it is possible to accurately estimate the battery voltage corresponding to the load current flowing from the battery 2 to the loads 14 and 16 and the ambient temperature of the internal circuit 10.
For example, at the time of rising after power-on or disk loading, a so-called transient state occurs in which a voltage drop of the internal circuit 10 is different from that in the steady state.
Even in this case, the battery voltage can be accurately estimated by selecting an appropriate estimation table based on the ambient temperature measured by the temperature measurement circuit 17 and the load current measured by the current measurement circuit 18. Become.

  In the first to fourth embodiments, the case where the fluctuation factor of the voltage drop amount of the internal circuit 10 is the operation mode, the load current, the ambient temperature of the internal circuit 10, and a combination thereof is shown. It is not limited to this. That is, any factor other than the operation mode, load current, and ambient temperature may be used as long as the voltage drop amount of the internal circuit 10 varies.

  In the present invention, within the scope of the invention, any combination of each embodiment, any component of each embodiment can be modified, or any component can be omitted in each embodiment. .

  1, 1A-1C In-vehicle device system, 2 Battery, 3 Display, 4 In-vehicle LAN, 10 Internal circuit, 11, 11A-11C CPU, 12 In-vehicle LANIF, 13, 15 Power supply unit, 14, 16 Load, 110 ADC, 111, 111A-111C table group, 111a-111e selection table, 112, 112A-112C estimation part, 113 control part.

Claims (1)

An internal element is interposed between the connector terminal connecting the battery and the input terminal, and an analog value of a voltage applied to the input terminal from the connector terminal by the battery through the internal element is converted into a digital value. A conversion unit;
A temperature measuring unit for measuring the ambient temperature of the internal element;
A current measuring unit for measuring a load current flowing from the battery to the load;
An estimation table indicating a correspondence relationship between an analog value and a digital value of a battery voltage applied to the connector terminal by the battery is a load current flowing from the battery to a load and an ambient temperature of the internal element. A table group for each variation factor of the voltage drop,
With reference to a selection table that indicates the correspondence between the variation factor of the voltage drop amount of the internal element and the estimation table of the table group, the estimation table that matches the variation factor of the voltage drop amount of the internal element is An estimation unit that selects from the table group, refers to the selected estimation table based on the digital value converted by the conversion unit, and estimates an analog value of the battery voltage applied to the connector terminal by the battery; Prepared ,
The estimation unit refers to the selection table, selects an estimation table that matches the ambient temperature measured by the temperature measurement unit and the load current measured by the current measurement unit from the table group, and selects the selected estimation A battery voltage estimation device that estimates an analog value of a battery voltage applied from the battery to the connector terminal by referring to the table based on a digital value of the battery voltage converted by the conversion unit.

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