JP5852882B2 - A / D conversion circuit, A / D converter error correction device, and battery remaining amount detection device - Google Patents

Description

  The present invention relates to an A / D conversion circuit for detecting a current amount, an error correction device for an A / D converter, and a remaining battery level detection device using the same.

  Conventionally, high functionality of a battery-operated device has been rapidly improved, and operation power consumption has increased. In particular, in portable devices such as mobile phone devices and portable game machines, an increase in operating power consumption leads to a decrease in battery operating time, and countermeasures are required because it reduces convenience.

  One countermeasure is to use power stored in the battery to the limit. As a method of implementing this measure, there is a method of observing the amount of coulomb and estimating the remaining battery level based on the measured value.

  The measurement of the amount of coulomb usually requires observation of the voltage across the sense resistor of several tens of mΩ, so that a highly accurate A / D converter is required.

  In general, a portable device is assumed to be carried by a person, and it is considered that a change in ambient temperature is large. In addition, since the operation is performed using a battery such as a secondary battery, it is considered that the change in the power supply voltage accompanying the discharge is large. These changes in usage conditions cause measurement error of the A / D converter used for measuring the coulomb amount. Therefore, the measurement error is reduced by periodically correcting the error.

  As a general error correction method for an A / D converter, as disclosed in Patent Document 1, the input of the A / D converter is short-circuited at a constant period, and the value at the time of the short-circuit is subtracted from the measured value as an error. Accordingly, there are a method for correcting to a correct measurement value, and an error correction method that has a plurality of correction tables in advance and uses different correction values depending on operating conditions as disclosed in Patent Document 2.

  Further, as a more advanced error correction method, as disclosed in Patent Document 3, a correction circuit is operated based on changes in temperature and time, and a correction table is dynamically updated and calculated. Can be mentioned.

  FIG. 4 is a configuration diagram of an error correction circuit of a conventional A / D converter disclosed in Patent Document 1. In FIG.

  As shown in FIG. 4, the error correction circuit 100 of the conventional A / D converter is provided with a selection signal output means 102 on the input side of the A / D converter 101, and the selection signal SEL from the selection signal output means 102. Thus, switch means 103 and 104 and an inverter 105 are provided for changing the input voltage to the A / D converter 101 into the converted voltage V and the “0” voltage. A correction calculation means 106 is provided on the output side of the A / D converter 101.

  With the above configuration, when the selection signal SEL is “L”, the conversion output value from the A / D converter 101 is the conversion output value that should be the converted voltage V + the offset voltage value.

  When the selection signal SEL is “H”, the conversion output value from the A / D converter 101 is only the offset voltage value.

  Therefore, when these are subtracted by the correction calculation means 106, the offset voltage value is canceled out and the converted output value of the converted voltage V is obtained.

  FIG. 5 is a configuration diagram of a battery remaining amount detection device in a conventional mobile phone device body disclosed in Patent Document 2.

  As shown in FIG. 5, in the conventional battery remaining amount detection device 200 in the mobile phone device main body, whether the current state of the mobile phone device is a call or a standby state, and further, an A / D converter 201 is provided. The control unit 202 switches the switch 203 to any one of the threshold ROM tables 204a to 204d in the table 204 and outputs it to the comparator 205 depending on whether the temperature value obtained through the display indicates normal temperature or low temperature. Let

  The voltage value of the battery pack 206 is converted by the A / D conversion unit 207 and input to the comparator 205. The comparator 205 includes threshold values set in any one of the threshold ROM tables 204a to 204d in the table 204 input from the switch 203, and the voltage value of the battery pack 206 input via the A / D conversion unit 207. And the control unit 202 is notified of the result. In the control unit 202, the remaining battery level is determined based on the determination result in the comparator 205, and the remaining battery level is displayed on the display unit 208. The voltage value of the battery pack 206 is also connected to the power supply unit 209.

  In this way, the control unit 202 can accurately detect the remaining battery level based on the determination result in the comparator 205 and display the remaining battery level on the display unit 208 in consideration of the influence of temperature change. The A / D converter 201 is connected to the thermistor 210 of the temperature measuring means, and the measurement data is input to the controller 202.

  FIG. 6 is a configuration diagram of a conventional current measurement circuit disclosed in Patent Document 3. In FIG.

  As shown in FIG. 6, in the conventional current measurement circuit 300, the CPU 301 as the control unit acquires the temperature measured by the temperature sensor 302 and the temperature A / D converter 303 and detects a temperature change. When a temperature change is detected, the memory 304 is searched to obtain a correction value for the measured temperature and used for subsequent error correction. When there is no correction value corresponding to the measured temperature in the memory 304, the CPU 301 controls the selector 305 so that the selection output signal becomes the GND level signal 306 and the reference voltage signal 308 from the reference voltage generator 307. The selector 305 is sequentially switched. A correction value (gain error) is calculated from the data (offset error) of the GND level signal 306 converted by the A / D converter 309 connected to the selector 305 and the data of the reference voltage signal 308 and stored in the memory 304. At the same time, the calculated correction value is used for subsequent error correction. Further, an analog input signal (current signal) 310 to be measured is input to the selector 305 and A / D converted by the A / D converter 309. As a result, it is possible to perform error correction corresponding to both temperature change and change with time.

JP-A-4-916 JP 2000-92721 A JP 2005-244771 A

  In general, since the value of the sense resistor used for measuring the amount of coulomb is very small, the voltage between both ends is several tens to several hundreds mV. In order to measure this minute voltage with high accuracy, an A / D converter with high accuracy but slow response speed such as a delta sigma type A / D converter is used. When the error correction method of Patent Document 1 is applied to an A / D converter having such characteristics, it is necessary to monitor how much current the A / D converter 101 uses continuously. There is a problem that the error measurement accuracy is lowered because the period becomes longer and it is necessary to supplement the unmeasured time with the estimated value. In addition to this, in the error correction method of Patent Document 1, if the resistance value of the short circuit 110 including the switch means 104 in the A / D converter 101 is not significantly smaller than the sense resistance, current also flows in the sense resistance. There is also a problem that offset error correction becomes insufficient.

  Further, in the error correction method of Patent Document 2, there is no dead period, but there is a problem that the accuracy is lowered except for a condition that completely matches the condition of the correction table.

  Further, in the correction method of Patent Document 3, it is possible to improve the accuracy compared to Patent Document 2 by dynamically switching the correction table, but there is a limit to the improvement of accuracy due to the restriction of the number of correction tables. .

  In addition, in the correction methods of Patent Documents 2 and 3, since it is necessary to use a device such as a microcomputer for error correction, the current consumption of the entire device increases and the original purpose of extending the operating time is achieved. There is a possibility of inhibiting.

  As described above, with the conventional correction method, it is difficult to monitor the remaining battery level while maintaining a balance between accuracy and power consumption, particularly in an A / D converter that requires high accuracy such as coulomb amount measurement. Met.

  The present invention solves the above-described conventional problems. An A / D conversion circuit, an A / D converter error correction apparatus, and an A / D converter that can detect a current amount with high accuracy while suppressing current consumption of the system are provided. It aims at providing the used battery remaining charge detection apparatus.

  An error correction apparatus for an A / D converter according to the present invention includes an A / D converter that can detect a current amount, a current amount determination circuit that determines the magnitude of the current amount detected by the A / D converter, A timer circuit that is turned on or off based on a determination result by the current amount determination circuit, and an offset detection that controls detection of the current amount and detection of the offset value by the A / D converter by control from the timer circuit And a current current calculation circuit for calculating a current use current amount by performing a predetermined calculation on the current amount detected by the A / D converter and the offset value, thereby The above objective is achieved.

  Preferably, in the error correction apparatus for an A / D converter according to the present invention, when the current amount determination circuit determines that the current amount is smaller than a predetermined reference value, the timer circuit performs the offset every predetermined time. The input side of the A / D converter is short-circuited using a detection circuit to detect the offset value, and after the offset value is detected, the A / D converter detects a current value, and the current current measurement The circuit corrects the error by subtracting the offset value from the detected current value, and when the current amount determination circuit determines that the current amount is equal to or greater than a predetermined reference value, the timer circuit is turned off to set the offset The detection of the value is interrupted, and the amount of current is detected by the A / D converter.

  Furthermore, it preferably further includes a cumulative current calculation circuit for calculating a cumulative current amount based on the current use current amount calculated by the current current calculation circuit in the error correction apparatus of the A / D converter of the present invention.

  Further preferably, the offset detection circuit in the error correction apparatus for an A / D converter according to the present invention is a first circuit for bypassing and short-circuiting a sense resistor provided between both input terminals of the A / D converter. 1 switch means and a second switch for turning off and opening the sense resistor.

  Further preferably, at the start of offset value detection in the error correction apparatus for an A / D converter of the present invention, the first switch means is turned on and the two input terminals of the A / D converter are short-circuited. The second switch means is opened, and when the offset value detection is completed, the second switch means is turned on and short-circuited, and then the second switch means is turned off and opened.

  Further preferably, in the error correction apparatus for an A / D converter according to the present invention, when the apparatus is on standby, the timer circuit is activated via the current amount determination circuit to control the offset detection circuit at regular intervals. The A / D converter detects an offset value, and the current current calculation circuit subtracts the offset value from the detected current amount to monitor the current current amount, and controls the offset detection circuit when the apparatus is in operation. The A / D converter detects the amount of current in a fixed state.

  The battery remaining amount detection device of the present invention includes an error correction device for the A / D converter of the present invention, and each of the current current calculation circuit and the cumulative current calculation circuit in the error correction device for the A / D converter. And a control unit that performs battery remaining amount detection calculation processing based on the data, thereby achieving the above object.

  Preferably, in the battery remaining amount detection device according to the present invention, the accumulated current amount that is error-corrected by using the A / D converter simultaneously with the start of the standby state in which the current amount is smaller than a predetermined reference value is used. The calculation circuit starts to calculate, and the control unit confirms the accumulated current amount in standby from the accumulated current calculation circuit simultaneously with the release of the standby state and continuously confirms the current amount using the A / D converter. Then, the remaining battery level is calculated based on both measurement results.

  Further preferably, in the remaining battery level detection device of the present invention, the control unit corresponds to a current temperature and power supply voltage state with respect to a current amount calculation result from the current current calculation circuit after the standby state is released. The remaining battery level is calculated by performing correction processing using the plurality of correction tables.

  An A / D conversion circuit according to the present invention includes a sense resistor for detecting a current value provided between both input terminals of an A / D converter, and an offset detection circuit capable of short-circuiting both ends of the sense resistor. Therefore, the above object can be achieved.

  Preferably, the offset detection circuit in the A / D conversion circuit according to the present invention bypasses and opens or shorts both ends of the sense resistor provided between both input terminals of the A / D converter. First switch means and a second switch for opening or connecting the sense resistor.

  Further preferably, in the A / D conversion circuit according to the present invention, when the offset value detection is started, the first switch means is turned on to short-circuit both input terminals of the A / D converter and then the second switch. After the detection of the offset value, the second switch means is turned on and the sense resistor is connected, and then the first switch means is turned off to open the bypass between both ends of the sense resistor.

  With the above configuration, the operation of the present invention will be described below.

  In the present invention, based on the A / D converter that can detect the current amount, the current amount determination circuit that determines the magnitude of the current amount detected by the A / D converter, and the determination result by the current amount determination circuit. Timer circuit that is turned on or off, an offset detection circuit that controls detection of the current amount and offset value by the A / D converter by control from the timer circuit, and current amount detected by the A / D converter And a current current calculation circuit that performs a predetermined calculation on the offset value to calculate the current amount of current used.

  Thus, the current amount detected by the A / D converter is determined by the current amount determination circuit, and the current amount is detected by the A / D converter by the control from the timer circuit based on the determination result by the current amount determination circuit. Since the current usage amount is calculated by controlling the detection of the offset value, it is possible to detect the current amount such as the remaining battery level with high accuracy while suppressing the current consumption of the system.

  As described above, according to the present invention, the amount of current detected by the A / D converter is determined by the current amount determination circuit, and A / D conversion is performed by control from the timer circuit based on the determination result by the current amount determination circuit. Since the current usage current amount is calculated by controlling the detection of the current amount and the offset value by the detector, the current amount such as the remaining battery level can be detected with high accuracy while suppressing the current consumption of the system.

It is a principal part block diagram of the battery remaining charge detection apparatus in Embodiment 1 of this invention. It is a circuit diagram in the case of short-circuiting between the input terminals of the A / D converter of FIG. It is a signal waveform diagram for demonstrating a sensor dead period when error correction is performed by the short circuit between the input terminals of an A / D converter. It is a block diagram of the error correction circuit of the conventional A / D converter currently disclosed by patent document 1. FIG. It is a block diagram of the battery remaining charge detection apparatus in the conventional mobile telephone apparatus main body currently disclosed by patent document 2. FIG. It is a block diagram of the conventional electric current measurement circuit currently disclosed by patent document 3. FIG.

  The case where the first embodiment of the error correction device for an A / D converter of the present invention is applied to a battery remaining amount detection device will be described in detail below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a main part configuration diagram of a remaining battery level detection apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, an error correction apparatus 1 for an A / D converter according to the first embodiment includes an A / D converter 2 (A / D conversion circuit) that can detect either an amount of current or an offset value for error correction. ), A current amount determination circuit 3 that determines the magnitude of the current amount detected by the A / D converter 2, a timer circuit 4 that is turned on / off based on the determination result, and A that is controlled by the timer circuit 4. The offset detection circuit 5 that controls the detection of the current amount and the offset value by the / D converter 2 and the current amount and the offset value detected by the A / D converter 2 are subjected to a predetermined calculation and It has a current current calculation circuit 6 for calculating the amount of current used, and a cumulative current calculation circuit 7 for calculating the amount of current accumulated based on the current amount of current used.

  The battery remaining amount detection device 10 according to the first embodiment includes an error correction device 1 of the A / D converter 2, a current current calculation circuit 6 and an accumulated current calculation circuit 7 of the error correction device 1 of the A / D converter 2. And a control unit (CPU 8) constituting a microcomputer that performs battery remaining amount detection processing based on each data.

  By the A / D converter 2 described above, a sense resistor 21 for detecting a current value provided between both input terminals of the A / D converter 2, and an offset detection circuit 5 for turning on and off both ends of the sense resistor 21. An A / D conversion circuit can be configured.

  In the A / D converter 2, a sense resistor 21 is provided between both input terminals of the A / D converter 2, and a voltage value generated at both ends of the sense resistor 21 when a current flows through the sense resistor 21 is applied between the two input terminals. Thus, it is possible to monitor how much current is used continuously.

  The current amount determination circuit 3 determines whether the current amount detected by the A / D converter 2 is large or small. However, if the current amount is large when the offset is large, for example, if it is a mobile phone device, the current amount during standby is A / D. It is determined whether or not the converter 2 has detected.

  The timer circuit 4 starts when the current amount determination circuit 3 determines that the A / D converter 2 has detected a predetermined minute amount of current, for example, a current amount during standby, and an offset detection circuit is thereby started. 5 is controlled to change the switch SW51 as the first switch means from the OFF state to the ON state, and the switch SW52 as the second switch means is changed from the ON state to the OFF state. As a result, the sense resistor 21 provided between the input terminals of the A / D converter 2 is short-circuited by the switch SW51. As a result, the offset value for error correction is output from the A / D converter 2, and the timer circuit 4 is stopped after a predetermined period thereafter, and the switch SW51 is turned from on to off by controlling the offset detection circuit 5. The switch SW52 is controlled from the off state to the on state. Thus, the amount of current detected through the sense resistor 21 is output from the A / D converter 2.

The offset detection circuit 5 causes a current to flow through the bypass path for bypassing the sense resistor 21, the switch SW 51 as the first switch means for making the bypass path conductive or non-conductive, and the sense resistor 21. And a switch SW52 as second switch means for making the current path conductive or non-conductive . When the switch SW51 is turned on and the switch SW52 is turned off, no current flows through the sense resistor 21, and the offset value of the A / D converter 2 is detected. When the switch SW51 is turned off and the switch SW52 is turned on, a current flows through the sense resistor 21, and the current value is detected by the A / D converter 2.

  The current current calculation circuit 6 performs a predetermined calculation on the detected value of the current amount detected by the A / D converter 2 to calculate the current current amount. From the calculated current amount, A / The offset value detected by the D converter 2 is subtracted to calculate the current amount of current that should be.

  The cumulative current calculation circuit 7 cumulatively calculates the calculated value of the current amount of the current current measurement circuit 6. In short, the cumulative current calculation circuit 7 calculates the cumulative current amount based on the current use current amount calculated by the current current calculation circuit 6.

  In short, when the current amount determination circuit 3 determines that the current amount is smaller than the predetermined reference value, the timer circuit 4 uses the offset detection circuit 5 to detect the input side of the A / D converter 2 at regular intervals. The both ends of the resistor 21 are short-circuited to detect an offset value for error correction. After the offset value is detected, the A / D converter 2 detects the amount of current (current value), and the offset value with respect to the current value. Is corrected by the current current measuring circuit 6 as an offset correction value of the current value, and when the current amount determination circuit 3 determines that the detected current amount is equal to or greater than a predetermined reference value, the timer circuit 4 is turned off to set the offset value. The A / D converter 2 detects the current amount.

  The control unit is composed of a CPU 8 (central processing unit), and based on the data from the current current calculation circuit 6 and the accumulated current calculation circuit 7 in the error correction device 1 of the A / D converter 2, the remaining battery level detection process I do. Simultaneously with the start of the standby state in which the current amount is smaller than the predetermined reference value, the accumulated current calculation circuit 7 starts to calculate the accumulated current amount that has been error-corrected using the A / D converter 2, and the CPU 8 as the control unit Simultaneously with the release, the accumulated current calculation circuit 7 from the accumulated current calculation circuit 7 is checked and the A / D converter 2 is used to continuously check the current amount, and the remaining battery level is calculated based on both measurement results. To do. For the current amount calculation result from the current current calculation circuit 6 after the standby state is released, the CPU 8 as the control unit performs a correction process using a plurality of correction tables corresponding to the current temperature and power supply voltage state to The remaining amount may be calculated.

  As shown in FIG. 2, the A / D converter 2 turns on the switch SW51 by the timer circuit 4, and an offset value for error correction is output from the output of the A / D converter 2, thereby A / D conversion. The sensor 2 does not perform the current detection operation of the sensor 2 and becomes a dead period.

  Here, the sensor dead period will be described with reference to FIG.

  FIG. 3 is a signal waveform diagram for explaining a sensor insensitive period when error correction is performed by a short circuit between the input terminals of the A / D converter 2.

  As shown in FIG. 3, when the switch SW51 is turned on and the switch SW52 is turned off by the timer circuit 4 so as to short-circuit both input terminals of the A / D converter 2 and disconnect the sense resistor 21, the A / D converter The input value to 2 decreases over the signal transition time, and after the input value to the A / D converter 2 has fully decreased, an offset measurement time for error correction is provided. After the error correction offset measurement time, the timer circuit 4 turns off the switch SW51 and turns on the switch SW52, thereby releasing the short circuit between the two input terminals of the A / D converter 2 and setting the sense resistor 21 to A / D. When connected between both input terminals of the converter 2, the input value to the A / D converter 2 is restored over a signal transition time.

  The sensor insensitive period at this time is a period from when the switch SW51 is turned on to when the switch SW51 is turned off until the input value to the A / D converter 2 is restored over a signal transition time. The sensor insensitive period is set periodically at regular intervals, and the current detection operation of the A / D converter 2 is not performed.

  With the above configuration, when detecting a small amount of current that is greatly affected by offset (when waiting for a portable information device such as a mobile phone device), the timer circuit 4 is activated to control the offset detection circuit 5. Periodically (every fixed time), the offset value is detected and subtracted to accurately monitor the amount of current to detect the remaining battery level. When detecting a large amount of current that is not significantly affected by the offset (such as a mobile phone device) If the portable information device is in operation), the control of the offset detection circuit 5 is fixed to the non-measuring side (off state), thereby detecting the amount of current generated as a side effect of the measurement of the offset value, and further the battery It is possible to eliminate errors in remaining amount detection. That is, when the apparatus is on standby, the timer circuit 4 is activated via the current amount determination circuit 3 and the offset detection circuit 5 is controlled so that the A / D converter 2 detects the offset value at regular intervals and calculates the current current. The circuit 6 subtracts this from the detected current amount to monitor the current amount of current, and when the device is operating, the A / D converter 2 operates in a state where the offset detection circuit 5 is fixed without being controlled. The amount is to be detected.

  Since the current amount is small when the system is in the standby state, the cumulative current amount calculation circuit 7 is used to monitor the cumulative current, and at the same time the standby state is canceled and the standby cumulative current amount is confirmed, the error correction circuit 1 By monitoring the current consumption without operating the error correction function, it is possible to monitor the remaining battery level with high accuracy while suppressing the power consumption of the entire device.

  Further, when the system is not in a standby state, it is possible to perform more advanced correction using the CPU 8 as the control unit, but the original operation state requires the CPU 8 even if additional correction is performed. Due to the state, the power consumption of the system hardly changes.

  The purpose of using the offset detection circuit 5 using the switch SW51 and the switch SW52 is to use a resistance value sufficiently lower than that of the sense resistor 21 in order to use the switch SW51 that directly shorts both ends of the sense resistor 21. On the other hand, the offset detection circuit 5 sets the input side of the A / D converter 2 to a short-circuited state by first short-circuiting the switch SW51 and then opening the switch SW52 when measuring the offset value. Thereafter, when the offset value is not measured, the switch SW51 having a large short-circuit resistance value may be used by performing the operation of setting the current measurement state by operating the switch SW51 and the switch SW52 in the reverse order of the short circuit. It becomes possible.

  Therefore, if the switch SW51 whose short-circuit resistance value is sufficiently smaller than the resistance value of the sense resistor 21 is used, it may be configured simply by short-circuiting both ends of the sense resistor 21.

  In addition, by adding a circuit for accumulating the measurement of the coulomb amount when the current amount is small, automatic correction by the error correction circuit 1 is performed when it is required to reduce power consumption such as standby state of the portable information device as much as possible. It is possible to measure the accumulated coulomb amount with high precision while using the control microcomputer while the control microcomputer is stopped, that is, with the standby power having a small amount of electricity.

  When the standby state is released and the accumulated coulomb amount during standby is checked and the device is operating at the time of detecting a large amount of current that is not significantly affected by the offset value, the error correction function of the error correction circuit 1 is not operated and the current amount is By performing the measurement, it is possible to prevent deterioration in accuracy due to the error correction operation of the error correction circuit 1.

  Therefore, by performing these controls, it is possible to monitor the remaining battery level with high accuracy while suppressing the power consumption of the entire device.

  In the standby release, since the microcomputer operates, the current current calculation circuit 6 calculates the current current amount based on the detected current amount data from the A / D converter 2, and the current use current amount is calculated. Based on this, the accumulated current calculation circuit 7 calculates the accumulated current amount. The accuracy can be further improved by further error correction by the CPU 8 of the microcomputer.

  As an example of this additional error correction, there is an example in which a plurality of correction coefficients are switched and used by the CPU 8 of the microcomputer for each temperature and power supply voltage.

  Note that the CPU 8 of the microcomputer is used for the additional correction. However, even if the correction operation is performed in addition to the original microcomputer processing, the current consumption is hardly increased, so that the power consumption is deteriorated. It is not a thing.

  As described above, according to the first embodiment, when the current amount determination circuit 3 determines that the current amount is smaller than the predetermined reference value, the timer circuit 4 uses the offset detection circuit 5 to perform A / The both ends of the sense resistor 21 on the input side of the D converter 2 are short-circuited to detect an offset value for error correction. After the offset value is detected, the A / D converter 2 detects a current amount value (current value). When the current amount measurement circuit 6 determines that the current value is equal to or greater than a predetermined reference value, the current current measurement circuit 6 corrects the offset value with respect to the current value as an offset correction value for the current value. The circuit 4 is turned off, the detection of the offset value is interrupted, and the current amount is detected by the A / D converter 2.

  As a result, in the standby state, the power consumption of the entire device is suppressed, and the coulomb amount is monitored with high accuracy without performing complicated control. By performing the monitoring, it is possible to manage the remaining battery level with high accuracy while suppressing an increase in power consumption of the entire device.

  As mentioned above, although this invention has been illustrated using preferable Embodiment 1 of this invention, this invention should not be limited and limited to this Embodiment 1. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range from the description of the specific preferred embodiment 1 of the present invention based on the description of the present invention and the common general technical knowledge. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  The present invention provides high accuracy while suppressing current consumption of a system in the fields of an A / D conversion circuit for detecting a current amount, an error correction device for an A / D converter, and a battery remaining amount detection device using the same. Can detect the amount of current such as the remaining battery level.

DESCRIPTION OF SYMBOLS 1 Error correction circuit of A / D conversion circuit 2 A / D converter 21 Sense resistance 3 Current amount determination circuit 4 Timer circuit 5 Offset detection circuit 51, 52 Switch SW
6 Current current calculation circuit 7 Cumulative current calculation circuit 8 Control unit (CPU)
10 Battery level detection device

Claims (11)

An A / D converter that can detect the current amount, a current amount determination circuit that determines the magnitude of the current amount detected by the A / D converter, and on or off based on a determination result by the current amount determination circuit a timer circuit which is, by the said timer circuits, the a / D converter at the power flow of the detection and the a / D converter controlled Ru offset detection as detection and is performed in the offset value and use circuit, possess a current current calculation circuit for calculating a current usage amount of current by performing a predetermined operation on the current amount detected by a / D converter and said offset value, said timer circuit, Turns off when the determination result is large, fixes the offset detection circuit in a state where the current amount is detected by the A / D converter, and turns on when the determination result is small. The offset detection circuit detects the current amount and the offset Detection and error correction device of the A / D converter to control to be performed by switching periodically at the A / D converter. 2. The error correction apparatus for an A / D converter according to claim 1, wherein the timer circuit detects the offset at regular intervals when the current amount determination circuit determines that the current amount is smaller than a predetermined reference value. The input side of the A / D converter is short-circuited using a circuit to detect the offset value, and after the offset value is detected, the A / D converter detects a current amount, and the current current calculation circuit Subtract the offset value from the detected current amount to correct the error,
When the current amount determination circuit determines that the current amount is equal to or greater than a predetermined reference value, the timer circuit is turned off to stop detecting the offset value, and the A / D converter detects the current amount. An error correction device for an A / D converter. 2. The error correction apparatus for an A / D converter according to claim 1, wherein the current use current amount calculated by the current current calculation circuit is cumulatively calculated in a time series to obtain a cumulative current amount. An error correction device for an A / D converter further comprising: The error correction apparatus for an A / D converter according to claim 1 or 2, wherein the offset detection circuit includes a bypass path that bypasses a sense resistor provided between both input terminals of the A / D converter ; A first switch that is provided in the bypass path and sets the bypass path to a conductive state or a non-conductive state; a current path that passes a current through the sense resistor; and a current path that is provided in the current path, error correction device of the a / D converter and a second switching means for whether or non-conducting state to a conducting state. 5. The error correction apparatus for an A / D converter according to claim 4, wherein at the start of offset value detection, the first switch means is turned on to bring the bypass path into a conductive state, and then the second switch means is turned off. When the offset value detection ends, the second switch means is turned on to bring the current path into a conductive state, and then the first switch means is turned off to turn off the bypass path. An error correction device for an A / D converter to be in a conductive state . 2. The error correction apparatus for an A / D converter according to claim 1, wherein the timer circuit is activated via the current amount determination circuit when the apparatus is on standby when the determination result is small, and the offset detection circuit is is subtracted from the amount of current the a / D converter has detected the current current calculation circuit is this the offset value to the detected every predetermined time by monitoring and controlling the current amount of current, the determination result is When the apparatus is large, the A / D converter reduces the current amount while the offset detection circuit is fixed by the timer circuit to a state where the current amount is detected by the A / D converter. Error correction device for A / D converter to detect. An error correction apparatus for an A / D converter according to claim 3 , and a remaining battery level detection based on each data from the current current calculation circuit and the accumulated current calculation circuit in the error correction apparatus for the A / D converter A battery remaining amount detection device having a control unit that performs arithmetic processing. In the battery remaining charge detection device according to claim 7,
The cumulative current calculation circuit starts calculating the cumulative current amount based on the current use current amount that has been error-corrected using the current current calculation circuit simultaneously with the start of the standby state in which the current amount is smaller than a predetermined reference value. The control unit confirms the accumulated current amount during standby from the accumulated current calculation circuit simultaneously with the cancellation of the standby state and continuously confirms the current amount using the A / D converter, and both measurement results Battery level detection device that calculates the remaining battery level based on the above.   9. The battery remaining amount detection device according to claim 8, wherein, with respect to a current amount calculation result from the current current calculation circuit after the standby state is released, the control unit includes a plurality of units corresponding to a current temperature and a power supply voltage state. The remaining battery level detection apparatus which performs a correction process using the correction table and calculates the remaining battery level. Possess a sense resistor for current value detection provided between the input terminals of the A / D converter, and an offset detection circuit connected to both ends of the sense resistor,
The offset detection circuit includes a bypass path for bypassing the sense resistor, a first switch means provided in the bypass path for bringing the bypass path into a conductive state or a non-conductive state, and a current through the sense resistor. A / D conversion circuit comprising: a current path through which the current flows; and a second switch means provided in the current path for bringing the current path into a conductive state or a non-conductive state . 11. The A / D converter circuit according to claim 10 , wherein at the time of starting offset value detection, the first switch means is turned on to bring the bypass path into a conductive state, and then the second switch means is turned off to pass the current path. It was a non-conductive state, the offset value detection end later and a non-conducting state the bypass passage off the first switch means after the said current path in a conducting state by turning on the second switch means A / D conversion circuit.

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