JP2010014651A - Voltage-measuring apparatus, storage device, and voltage measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure a measurement object voltage, with less power consumption. <P>SOLUTION: An object charging section 120 charges a capacitor C11 to the measuring object voltage V<SB>s</SB>. A reference-charging section 130 charges the capacitor C11 to a reference voltage V<SB>ref</SB>. A discharging section 140 discharges the capacitor C11 at a predetermined circuit time constant τ. An object discharge time measuring section 150 measures the time (object discharge time T<SB>s</SB>), until the charge voltage v<SB>c</SB>of the capacitor C11 becomes, from the measuring object voltage V<SB>s</SB>, a detection voltage V<SB>t</SB>by the discharge of the discharge section 140. A reference discharge time measuring section 160 measures the time (reference discharge time T<SB>ref</SB>), when the charge voltage v<SB>c</SB>of the capacitor C11 becomes from a reference voltage V<SB>ref</SB>to a detection voltage V<SB>t</SB>by the discharging of the discharge section 140. A measuring object voltage calculating section 170 calculates the voltage value of the measurement object voltage V<SB>s</SB>, based on the object discharge time T<SB>s</SB>and the reference discharge time T<SB>ref</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a voltage measuring device and a voltage measuring method for measuring a voltage, and a storage device using the same.

In order to prevent data loss due to a power failure or the like, there is a storage device provided with a backup power source. When using a rechargeable battery as the backup power supply, if the main power supply is off for a long period of time, the backup power supply cannot maintain the voltage at which the memory can keep the data, and data may be lost. is there. In order to determine whether data has been lost, the voltage output from the backup power supply is measured, and it is determined whether the voltage is equal to or higher than the voltage at which the memory can continue to hold data.
JP 7-104898 A Texas Instruments Incorporated "Application Report SLAA071" 1999

The power source for operating the voltage measuring device for measuring the voltage of the backup power source is also supplied from the backup power source. If the voltage measuring device consumes a large amount of power to measure the voltage, the backup power supply is consumed, and the period during which the memory can hold data is shortened. For this reason, it is desirable that the power consumed by the voltage measuring device be as small as possible.
The present invention has been made, for example, in order to solve the above-described problems, and an object thereof is to accurately measure a voltage to be measured while suppressing power consumption as much as possible.

The voltage measuring device according to the present invention is:
In a voltage measuring device that measures a voltage to be measured, which is a measurement target,
A capacitor, a target charging unit, a reference charging unit, a discharging unit, a target discharging time measuring unit, a reference discharging time measuring unit, and a measuring target voltage calculating unit;
The target charging unit charges the capacitor up to the measurement target voltage,
The reference charging unit charges the capacitor to a predetermined reference voltage,
The discharging unit discharges the capacitor with a predetermined circuit time constant,
The target discharge time measurement unit is configured such that a charge voltage charged in the capacitor when the target charge unit charges the capacitor to the measurement target voltage and then the discharge unit discharges the capacitor is a predetermined detection voltage. Measure the time to become the target discharge time,
The reference discharge time measurement unit measures a time from when the reference charging unit charges the capacitor to the reference voltage until the charging voltage becomes the detection voltage when the discharging unit discharges the capacitor. As the reference discharge time,
The measurement target voltage calculation unit calculates a voltage value of the measurement target voltage based on the target discharge time measured by the target discharge time measurement unit and the reference discharge time measured by the reference discharge time measurement unit. It is characterized by.

  According to the voltage measuring apparatus of the present invention, the voltage to be measured can be calculated regardless of the circuit time constant. Therefore, even when the circuit time constant is unknown or changes, the voltage to be measured is accurately measured. be able to. In addition, if the capacitance value of the capacitor is small, the current required for charging and discharging the capacitor is small, so that the power consumed to measure the voltage to be measured can be suppressed.

Embodiment 1 FIG.
The first embodiment will be described with reference to FIGS.

FIG. 1 is a system configuration diagram showing an example of the overall configuration of the storage device 800 in this embodiment.
The storage device 800 (battery backup memory system) includes a rechargeable battery 801, a volatile memory 802, an interface unit 803, a voltage measurement device 100, a holding comparison unit 810, a disappearance determination unit 820, and a nonvolatile memory 830.

The storage device 800 operates with power supplied from the main power supply device 200.
The rechargeable battery 801 (battery) is a backup power source using, for example, an electric double layer capacitor. The rechargeable battery 801 is charged by the power supplied from the main power supply device 200. When power is not supplied from the main power supply device 200, the rechargeable battery 801 supplies power for operating the storage device 800 as a backup. (Hereinafter, the voltage value of the power supply voltage supplied from the main power supply device 200 or the rechargeable battery 801 is represented by the symbol “V _cc ”.)
Volatile memory 802 (RAM) stores data. Volatile memory 802 can store stored data if power supply voltage _Vcc is equal to or higher than a predetermined voltage (hereinafter referred to as “holding voltage”, and the voltage value of the holding voltage is represented by the symbol “V _min ”). If the power supply voltage V _cc falls below the holding voltage V _min , it cannot be guaranteed that the data is held, and the stored data may be lost.
The interface unit 803 (host I / F unit) reads out data stored in the volatile memory 802 or the non-volatile memory 830 in accordance with an external command such as a host computer (host CPU) and transmits the read data to the outside. Data is received from the outside and written into the volatile memory 802 or the nonvolatile memory 830.

Voltage measuring device 100 (voltage monitoring unit) measures the power supply voltage _{V cc.} (Hereinafter, the voltage that is the measurement target of the voltage measurement device 100 is referred to as a measurement target voltage, and the voltage value of the measurement target voltage measured by the voltage measurement device 100 is represented by the symbol “V _s ”.)
The holding comparison unit 810 compares the measurement target voltage V _s measured by the voltage measuring device 100 with the holding voltage V _min to determine the magnitude relationship.
The erasure determination unit 820 determines that the data stored in the volatile memory 802 has disappeared when the measurement target voltage V _s is smaller than the retention voltage V _min based on the magnitude relationship determined by the holding comparison unit 810. The disappearance determination unit 820 writes data representing the determination result (hereinafter referred to as “disappearance determination data”) in the nonvolatile memory 830.
The nonvolatile memory 830 stores data. Unlike the volatile memory 802, the nonvolatile memory 830 can hold data without receiving power supply, but the amount of data that can be stored is smaller than that of the volatile memory 802. The nonvolatile memory 830 stores the erasure determination data written by the erasure determination unit 820.
The erasure determination data (battery flag) is, for example, 1-bit data, and represents “0” when it is determined that the data stored in the volatile memory 802 is lost, and the volatile memory 802 holds the data. The case where it is determined that it is present is represented by “1”.

  Note that the interface unit 803, the voltage measurement device 100, the holding comparison unit 810, the disappearance determination unit 820, and the like may be configured by analog circuits or may be configured by digital circuits. Alternatively, it may be composed of an analog / digital hybrid circuit. Alternatively, it may be realized by a microcomputer executing a program. In that case, for example, the nonvolatile memory 830 stores the program executed by the microcomputer.

FIG. 2 is a flowchart showing an example of the flow of erasure determination processing in which the storage device 800 in this embodiment determines data loss.
The disappearance determination process is a process for determining whether or not the data stored in the volatile memory 802 has been lost (possibly).

In the voltage measurement process S410, the voltage measuring apparatus 100 measures the power supply voltage _{V cc} of the rechargeable battery 801 and outputs, to the measured voltage _{V s.}
In the holding comparison step S420, the holding comparison unit 810 compares the measurement target voltage V _s measured by the voltage measuring device 100 in the voltage measurement process S410 with a predetermined holding voltage V _min . If measured voltage _{V s} is maintained voltage _{V min,} and the flow returns to the voltage measurement process S410. When the measurement target voltage V _s is smaller than the holding voltage V _min , the process proceeds to the disappearance determination step S430.
In the erasure determination step S430, the erasure determination unit 820 determines that the data stored in the volatile memory 802 has been lost (possibly), and generates erasure determination data.
In the disappearance determination storage step S440, the nonvolatile memory 830 stores the disappearance determination data generated by the disappearance determination unit 820 in the disappearance determination step S430.

If the main power supply device 200 is off for a short period, the data stored in the volatile memory 802 is retained by the backup from the rechargeable battery 801.
On the other hand, when the main power supply device 200 is turned off for a long time, the power supply voltage V _cc supplied by the rechargeable battery 801 decreases. When the power supply voltage _Vcc falls below the holding voltage _Vmin , there is no guarantee that the data stored in the volatile memory 802 is held. When the voltage measuring device 100 measures the power supply voltage V _cc and the holding comparison unit 810 compares with the holding voltage V _min and the power supply voltage V _cc becomes less than the holding voltage V _min , the disappearance determination unit 820 stores in the nonvolatile memory 830. Since erasure determination data is stored, whether or not the volatile memory 802 has lost (possibly) lost data by reading the data stored in the nonvolatile memory 830 after the main power supply device 200 is turned on. I understand.

  Operating power for the voltage measuring device 100 and the like is supplied from the rechargeable battery 801 as in the volatile memory 802. Therefore, when the power consumption of the voltage measuring device 100 or the like is large, the rechargeable battery 801 is consumed, and the period during which the volatile memory 802 can hold data is shortened. For this reason, it is preferable that the power consumption of the voltage measuring device 100 or the like is small.

FIG. 3 is a block configuration diagram showing an example of a functional block configuration of the voltage measuring apparatus 100 according to this embodiment.
The voltage measuring apparatus 100 includes a capacitor C11, a target charging unit 120, a reference charging unit 130, a discharging unit 140, a target discharging time measuring unit 150, a reference discharging time measuring unit 160, and a measuring target voltage calculating unit 170.

The capacitor C11 is a capacitive element that stores electric charge and generates a voltage at both ends in proportion to the stored electric charge. Hereinafter, the voltage generated at both ends of the capacitor C11 is referred to as “charging voltage” and is represented by the symbol “v _C ”.
Target charging unit 120 receives the measured voltage _{V s,} until the charging voltage _{v c} is substantially equal to the measured voltage _{V s,} charges the capacitor C11.
Reference charging unit 130, (referred to as the "reference voltage" represents a voltage value of the reference voltage by the symbol "V _ref".) Charge voltage v _c is a predetermined voltage to substantially equal, to charge the capacitor C11.
Discharging unit 140 discharges capacitor C11 with a predetermined time constant (hereinafter referred to as “circuit time constant” and represented by symbol “τ”). For example, if the discharge circuit in which the discharge unit 140 discharges the capacitor C11 is an RC series circuit, τ = R · C (C is the capacitance value of the capacitor C11. R is the resistance of the resistor connected in series with the capacitor C11. Electrical resistance value).
Target discharge time measuring unit 150, target charging unit 120 charges the capacitor C11 to the measurement target voltage _{V s,} the discharge unit 140 to start discharge of the capacitor C11, the charging voltage _{v c} is a predetermined voltage (hereinafter " This is called “detection voltage” and is represented by the symbol “V _t ”). Hereinafter, the time measured by the target discharge time measurement unit 150 is referred to as “target discharge time” and is represented by the symbol “T _s ”.
Reference discharge time measurement unit 160, the reference charging unit 130 charges the capacitor C11 up to the reference voltage _{V ref,} the discharge portion 140 from the start of the discharge of the capacitor C11, approximately equal charge voltage _{v c} is the detection voltage _{V t} Measure the time to become. Hereinafter, the time measured by the reference discharge time measurement unit 160 is referred to as “reference discharge time” and is represented by a symbol “T _ref ”.
The measurement target voltage calculation unit 170 is input by the target charging unit 120 based on the target discharge time T _s measured by the target discharge time measurement unit 150 and the reference discharge time T _ref measured by the reference discharge time measurement unit 160. calculating the voltage value V _s of the measured voltage. Measured voltage calculation unit 170 outputs data representing the calculated measured voltage V _s.

  FIG. 4 is a flowchart showing an example of the flow of voltage measurement processing S410 in which the voltage measurement apparatus 100 according to this embodiment measures the voltage to be measured.

In the target charging step S510, the target charging unit 120 charges the capacitor C11 to the measurement target voltage _{V s.}
In the target discharge start step S520, the discharge unit 140 starts discharging the capacitor C11. Capacitor C11 is discharged at the circuit time constant tau, going down the charging voltage v _c.
In the target discharge time measurement starting step S530, the target discharge time measurement unit 150 starts measuring the target discharge time T _s.
In the target voltage comparison step S540, the target discharge time measurement unit 150 compares the charging voltage _{v c} and detection voltage _{V t,} and determines the size relationship. If the charge voltage _{v c} is greater than the detection voltage _{V t,} repeated target voltage comparison step S540. If the charge voltage _{v c} is equal to or less than the detection voltage _{V t,} the process proceeds to a subject discharge time measurement end step S550.
In the target discharge time measurement end step S550, the target discharge time measurement unit 150 ends the measurement of the target discharge time T _s. The target discharge time measurement unit 150 acquires the elapsed time since the start of the measurement of the target discharge time T _{s in} the target discharge time measurement start step S530, and sets it as the target discharge time T _s .
In the reference charging step S560, the reference charging unit 130 charges the capacitor C11 to the reference voltage _Vref .
In the reference discharge start step S570, the discharge unit 140 starts discharging the capacitor C11. Capacitor C11 is discharged at the circuit time constant tau, going down the charging voltage v _c.
In reference discharge time measurement start step S580, the reference discharge time measurement unit 160 starts measuring the reference discharge time _{T ref.}
In the reference voltage comparison step S590, the reference discharge time measurement unit 160 compares the charging voltage _{v c} and detection voltage _{V t,} and determines the size relationship. If the charge voltage _{v c} is greater than the detection voltage _{V t,} repeated reference voltage comparison step S590. If the charge voltage _{v c} is equal to or less than the detection voltage _{V t,} the process proceeds to the reference discharge time measurement end step S600.
In the reference discharge time measurement end step S600, the reference discharge time measurement unit 160 ends the measurement of the reference discharge time _Tref . The reference discharge time measurement unit 160 acquires the elapsed time since the measurement of the reference discharge time T _ref is started in the reference discharge time measurement start step S580, and sets it as the reference discharge time T _ref .
In the measurement target voltage calculation step S610, the measurement target voltage calculation unit 170 performs the target discharge time T _s acquired by the target discharge time measurement unit 150 in the target discharge time measurement end step S550 and the reference discharge in the reference discharge time measurement end step S600. Based on the reference discharge time T _ref acquired by the time measurement unit 160, the measurement target voltage V _s is calculated. Measured voltage calculation unit 170 outputs data representing the calculated measured voltage V _s.

Figure 5 is a graph showing an example of a change in the charging voltage v _c, which is charged in the capacitor C11 in this embodiment.
In the initial state, since the capacitor C11 is not charged, the charging voltage v _c is zero.
Target charging unit 120 charges the capacitor C11 in the target charging step S510, the charging voltage _{v c} reaches the measured voltage _{V s.}
Discharge unit 140 by the target discharge start step S520 starts the discharge of the capacitor C11, the time until the target discharge time measuring unit 150 when the charging voltage v _c is less than the detection voltage V _t by the target voltage comparing step S540 to determine It measured the target discharge time measuring unit 150, a target discharge time T _s.
In the reference charging step S560, the reference charging unit 130 charges the capacitor C11, and the charging voltage vc reaches the reference voltage _Vref .
Reference discharge start step S570 in the discharge portion 140 starts discharge of the capacitor C11, the charging voltage v _c with a reference voltage comparison step S590 is less than the detection voltage V _t reference discharge time measurement unit 160 is a time to determine The reference discharge time measurement unit 160 measures the reference discharge time T _ref .

ただし、Ｖ_ｓは測定対象電圧、Ｖ_ｔは検知電圧、Ｖ_ｒｅｆは基準電圧、Ｔ_ｓは対象放電時間、Ｔ_ｒｅｆは基準放電時間を表わす。 Equation for the measurement target voltage calculating process S610 are measured voltage calculating unit 170 calculates a voltage value V _s of the measured voltage is as follows.

However, _{V s} is measured voltage, _{V t} is the detection _{voltage, V ref} is a reference voltage, _{T s} is the target discharge _{time, T ref} represents the reference discharge time.

ただし、Ｖ_０はｔ＝０における充電電圧ｖ_ｃの初期値、ｅは自然対数の底、Ａは定数でＡ＝ｅｘｐ（−１／τ）である。 When the discharge unit 140 is the elapsed time from the start of discharge the capacitor C11 and t, the charge voltage v _c is a function of t, is expressed by the following equation.

However, _{V 0} is the initial value of the charging voltage _{v c} at t = 0, e is the base of natural logarithms, A is A = exp (-1 / τ) by a constant.

また、対象放電時間測定部１５０がコンデンサＣ１１を測定対象電圧Ｖ_ｓまで充電した場合、Ｖ_０＝Ｖ_ｓであるから、

したがって、

When the reference discharge time measurement unit 160 charges the capacitor C11 to the reference voltage V _ref , V ₀ = V _ref ,

In addition, when the target discharge time measurement unit 150 charges the capacitor C11 to the measurement target voltage V _s , V ₀ = V _s ,

Therefore,

The circuit time constant τ may vary depending on measurement conditions such as element variation and temperature, but the calculation formula for the measurement target voltage calculation unit 170 to calculate the voltage value V _s of the measurement target voltage is a circuit time constant. τ is not included. Therefore, even if the circuit time constant τ has changed or is unknown, the measurement target voltage V _s can be accurately calculated.

Since the reference discharge time T _ref is constant regardless of the measurement target voltage V _s , it is measured and stored only once, and after the second time, the reference discharge time T _ref is not measured. The measurement target voltage calculation unit 170 may calculate the measurement target voltage V _s using the reference discharge time T _ref measured and stored first. In this case, it is necessary to accurately calculate the measurement target voltage V _s in consideration of the possibility that the circuit time constant τ changes with changes in temperature conditions and the reference discharge time T _ref changes as a result. In some cases (for example, when the measurement target voltage V _s and the holding voltage V _min are close), the reference discharge time T _ref may be measured again.

In this manner, the measurement target voltage V _s is measured by measuring the time from discharging the capacitor C11 to the predetermined voltage (detection voltage V _t ). If the capacitance value of the capacitor C11 is small, the current required for charging the capacitor C11 is small, and the power consumed for measurement can be suppressed.

The voltage measuring apparatus 100 in this embodiment measures a measurement target voltage V _s that is a measurement target.
The voltage measuring apparatus 100 includes a capacitor C11, a target charging unit 120, a reference charging unit 130, a discharging unit 140, a target discharging time measuring unit 150, a reference discharging time measuring unit 160, and a measuring target voltage calculating unit 170. And have.
The target charging unit 120 charges the capacitor C11 until the measured voltage _{V s.}
The reference charging unit 130 charges the capacitor C11 up to a predetermined reference voltage _Vref .
The discharging unit 140 discharges the capacitor C11 with a predetermined circuit time constant τ.
The target discharge time measurement unit 150, the target charging unit 120 has charged the capacitor to the measured voltage V _s, the discharge unit 140 is charged in the capacitor C11 by the discharge the capacitor C11 target discharging time T _s charging voltage v _c is by measuring the time until a predetermined detection voltage V _t.
Said reference discharge time measurement unit 160, the reference charging unit 130 has charged the capacitor C11 to the reference voltage _{V ref,} the charging voltage _{v c} by the discharge unit 140 is discharged to the capacitor C11 is the The time until the detection voltage Vt is _reached is measured and set as a reference discharge time _Tref .
The measurement target voltage calculation unit 170 is configured to calculate the measurement target voltage based on the target discharge time T _s measured by the target discharge time measurement unit 150 and the reference discharge time T _ref measured by the reference discharge time measurement unit 160. _Is calculated.

As a result, the measurement target voltage V _s can be calculated regardless of the circuit time constant τ, so that the measurement target voltage V _s can be accurately measured even when the circuit time constant τ is unknown or changes. it can.
Also, the smaller the capacitance value of the capacitor C11, the current required for charging and discharging of the capacitor C11 is small, it is possible to suppress the power consumed in order to measure the measurement target voltage V _s.

ただし、Ｖ_ｓは測定対象電圧、Ｖ_ｔは検知電圧、Ｖ_ｒｅｆは基準電圧、Ｔ_ｓは対象放電時間、Ｔ_ｒｅｆは基準放電時間である。 In the voltage measuring apparatus 100 in this embodiment,
The measured voltage calculating unit 170, using the following formula to calculate the voltage value V _s of the measured voltage.

However, _{V s} is measured voltage, _{V t} is the detection _{voltage, V ref} is a reference voltage, _{T s} is the target discharge _{time, T ref} is the reference discharge time.

Thus, the measurement target voltage V _s can be accurately calculated based on the target discharge time T _s and the reference discharge time T _ref .

  Note that the measurement target voltage calculation unit 170 may calculate the above mathematical formula by referring to a prestored table, or may calculate by another method.

The storage device 800 in this embodiment includes a volatile memory 802, a rechargeable battery 801, the voltage measurement device 100, a holding comparison unit 810, and a disappearance determination unit 820.
The volatile memory 802, if the voltage supplied as the power source is a predetermined hold voltage V _min or more, to hold the stored data.
The rechargeable battery 801 supplies the charged voltage as a power source for the volatile memory 802.
The voltage measuring device 100 measures the voltage charged in the rechargeable battery 801 as the measured voltage V _s.
The holding comparison unit 810 compares the measurement target voltage V _s measured by the voltage measuring device 100 with the holding voltage V _min to determine the magnitude relationship.
The erasure determination unit 820 loses the data stored in the volatile memory 802 when the measurement target voltage V _s is smaller than the retention voltage V _min based on the determination result determined by the holding comparison unit 810. Is determined.

  Thereby, it can be determined whether or not the data stored in the volatile memory 802 has been lost. If the power consumption of the voltage measuring device 100 is small, the power consumed to determine data loss can be suppressed, so that the period in which the volatile memory 802 can hold data can be extended.

The storage device 800 in this embodiment further includes a nonvolatile memory 830.
The nonvolatile memory 830 stores data (disappearance determination data) representing the determination result determined by the disappearance determination unit 820.

  Thereby, it is possible to know whether or not the data stored in the volatile memory 802 is lost after the main power supply is restored while the main power supply is off.

Note that the erasure determination unit 820 may store erasure determination data indicating data retention or data loss in the nonvolatile memory 830 for each determination, or at the first time when the storage device 800 starts battery operation. The erasure determination data indicating data retention may be stored, and when the erasure determination unit 820 determines that the data has been lost, the erasure determination data indicating the data loss may be stored.
The nonvolatile memory 830 is not the loss determination data, the data representing the voltage value of the measured voltage V _s of the voltage measuring device 100 and output as it may be stored. In that case, after the main power supply is restored, it is determined whether or not the data stored in the volatile memory 802 has been lost by comparing the voltage value represented by the data stored in the nonvolatile memory 830 with the holding voltage _Vmin. it can.

The voltage measurement method in this embodiment measures the measurement target voltage V _s that is a measurement target by the following steps.
It charges the capacitor C11 until the measured voltage _{V s.}
To discharge the capacitor C11 in a predetermined circuit time constant tau, a target discharge time T _s by the charging voltage v _c, which is charged in the capacitor C11 measures the time until the predetermined detection voltage V _t.
The capacitor C11 is charged up to a predetermined reference voltage _Vref .
The capacitor C11 is discharged by the circuit time constant tau, the charging voltage v _c is to measure the time until the detection voltage V _t and the reference discharge time T _ref.
Based on the measured target discharge time T _s and the measured reference discharge time T _ref , the voltage value V _s of the measurement target voltage is calculated.

As a result, the measurement target voltage V _s can be calculated regardless of the circuit time constant τ, so that the measurement target voltage V _s can be accurately measured even when the circuit time constant τ is unknown or changes. it can.
Also, the smaller the capacitance value of the capacitor C11, the current required for charging and discharging of the capacitor C11 is small, it is possible to suppress the power consumed in order to measure the measurement target voltage V _s.

The storage device 800 (battery backup memory system) described above retains data on the RAM (volatile memory 802) by the backup power supply (rechargeable battery 801) even when the main power supply (main power supply device 200) is off. Measure the voltage of the backup power supply (rechargeable battery 801) using an electric double layer capacitor, the RAM (volatile memory 802) for storing data to be retained when the main power supply is off, and the backup power supply. The voltage monitor unit (voltage measuring device 100) that measures the backup power supply voltage _Vcc while the main power supply is off, and monitors the measured voltage status information (disappearance determination data). Held in the internal memory (nonvolatile memory 830).
For example, the disappearance determination unit 820 sets a value (= 1) indicating that the backup power supply voltage _Vcc is normal in the battery flag (disappearance determination data) when the main power supply is turned off. Disappearance degree judgment unit 820, a value indicating that the voltage V _cc of the backup power supply circuit (battery 801) is when below the data holding minimum voltage (holding voltage V _min), has become abnormal in the battery flag (loss determination data) (= 0) is set. After the main power is restored, the host CPU checks the battery flag of the voltage monitor unit and determines whether the data on the RAM is retained or lost during the main power off period.

Note that the built-in memory (determination result storage unit) that stores the battery flag (disappearance determination data) may be configured by a volatile memory instead of the nonvolatile memory 830.
In this case, since the value of the battery flag stored in the determination result storage unit may change due to a decrease in the backup power supply voltage _Vcc , the battery flag is not 1-bit data but a plurality of bits (for example, 16 bits). Data. For example, if the backup power supply voltage V _cc is normal, the disappearance determination unit 820 sets the battery flag to “AAAA” in hexadecimal, and if the backup power supply voltage V _cc falls below the holding voltage V _min , And “5555” (inverted each bit of “AAAA”), and the determination result storage unit stores it. After the main power is restored, the host CPU checks the battery flag of the voltage monitor unit. If “AAAA”, it is determined that the data on the RAM is retained during the main power off period. If it is, it is determined that it has disappeared.
When the backup power supply voltage _Vcc falls below the holding voltage _Vmin , the value of the battery flag stored in the determination result storage unit may change, and is not necessarily “5555”. However, since there is no matching bit between “5555” and “AAAA”, if even one bit is held unchanged, the value of the battery flag after the change will not be “AAAA”. Even if all the bits have changed, the bit value after the change is indefinite, so if the probability of becoming “1” is equal to the probability of becoming “0”, the probability of becoming “AAA” is 65536 minutes. It can be said that there is almost no. This probability can be further reduced by increasing the number of bits of the battery flag.
Therefore, it can be determined whether the data is retained or lost by determining whether the value of the battery flag is “AAAA”.
Thus, if the battery flag is data of a plurality of bits and the value of the battery flag indicating abnormality is a value obtained by inverting each bit of the value of the battery flag indicating normality, a determination result storage unit that stores the battery flag is provided. Even with a volatile memory, it is possible to determine whether the data on the RAM is retained or lost during the main power-off period. The possibility of misjudgment is not 0, but can be almost ignored. In order to further reduce the probability of erroneous determination, the number of bits of the battery flag may be increased. For example, it is preferably 16 bits or more.

  In the storage device 800 (battery backup memory system) described above, the voltage monitor unit (nonvolatile memory 830) is connected to the host CPU at the host I / F unit (interface unit 803), and after the main power is restored, the host CPU Confirms the state data of the voltage monitor unit and determines whether the data in the RAM is retained or lost during the main power-off period.

Embodiment 2. FIG.
The second embodiment will be described with reference to FIGS.
Note that portions common to the storage device 800 described in Embodiment 1 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 6 is a circuit diagram showing an example of the circuit configuration of the voltage measuring apparatus 100 according to this embodiment.
The voltage measuring apparatus 100 includes a capacitor C11, a resistor R12, a switch SW22, a reference voltage generation unit 131, a detection voltage generation unit 151, a voltage comparison unit 154, a charge / discharge switching unit 121, a comparison voltage switching unit 133, a timer circuit 155, and target discharge. It has a time measurement unit 150, a reference discharge time measurement unit 160, and a measurement target voltage calculation unit 170.

  The capacitor C11 is a capacitive element. One terminal of the capacitor C11 is electrically connected to a ground wiring having a reference potential in the voltage measuring device 100. The other terminal of the capacitor C11 is electrically connected to the first input terminal of the voltage comparison unit 154.

  The resistor R12 is an electrical resistance element that generates a voltage proportional to the flowing current at both ends. One terminal of the resistor R12 is electrically connected to the first input terminal of the voltage comparison unit 154 together with the terminal that is not connected to the ground wiring of the capacitor C11. The other terminal of the resistor R12 is electrically connected to the common terminal of the switch SW22.

The switch SW22 is a four-terminal component and has a common terminal, a first switching terminal, a second switching terminal, and a switching signal input terminal. The switch SW22 switches between a state where the common terminal and the first switching terminal are conducted and a state where the common terminal and the second switching terminal are conducted according to the switching signal input from the switching signal input terminal. The second switching terminal is insulated when the common terminal and the first switching terminal are conducted, and the first switching terminal is insulated when the common terminal and the second switching terminal are conducted. First switching terminal of the switch SW22 is electrically connected to the terminal voltage measuring device 100 inputs the measured voltage V _s. The second switching terminal of the switch SW22 is electrically connected to the ground wiring. The common terminal of the switch SW22 is electrically connected to the terminal not connected to the capacitor C11 of the resistor R12. The switching signal input terminal of the switch SW22 is electrically connected to the output of the charging / discharging switching unit 121, and inputs the switching signal generated by the charging / discharging switching unit 121.
If the switch SW22 by the switching signal is turned to the common terminal and the first switching terminal, it is applied to the capacitor C11 measured voltage V _s via a resistor R12, to charge the capacitor C11. The switch SW22 and the resistor R12 in this state are an example of a charging unit.
When the switch SW22 conducts the second switching terminal and the common terminal by the switching signal, the capacitor C11 is discharged via the resistor R12. The switch SW22 and the resistor R12 in this state are an example of the discharge unit 140. At this time, the circuit time constant τ at which the discharge unit 140 discharges the capacitor C11 is τ = R · C (R is the electric resistance value of the resistor R12, and C is the capacitance value of the capacitor C11).

The reference voltage generation unit 131 is a circuit that generates a reference voltage V _ref . The reference voltage generation unit 131 includes a constant voltage circuit 132, for example.
The constant voltage circuit 132 (regulator) is a three-terminal component and has an input terminal, a reference terminal, and an output terminal. When a voltage within a predetermined range is applied between the input terminal and the reference terminal of the constant voltage circuit 132, a predetermined constant voltage is generated between the output terminal and the reference terminal. The voltage generated between the output terminal of the constant voltage circuit 132 and the reference terminal is lower than the voltage applied between the input terminal of the constant voltage circuit 132 and the reference terminal, but between the input terminal and the reference terminal. If the voltage applied to is within a predetermined range, the voltage generated between the output terminal and the reference terminal is substantially constant. Input terminal of the constant voltage circuit 132, with the first switching terminal of the switch SW22, and is electrically connected to the terminal voltage measuring device 100 inputs the measured voltage V _s. The reference terminal of the constant voltage circuit 132 is electrically connected to the ground wiring. The output terminal of the constant voltage circuit 132 is electrically connected to the second switching terminal of the switch SW34. Thus, the reference voltage generating unit 131 inputs the measured voltage V _s, if measured voltage V _s inputted is within a predetermined range, a predetermined reference voltage V _ref is lower than the measured voltage V _s Generate.

Detection voltage generating unit 151 is a circuit that generates a detection voltage V _t. The detection voltage generation unit 151 includes, for example, two resistors R52 and R53.
The two resistors R52 and R53 are electric resistance elements having substantially equal electric resistance values. One terminal of the resistor R52 is electrically connected to the output terminal of the constant voltage circuit 132 and to the second switching terminal of the switch SW34. The other terminal of the resistor R52 is electrically connected to one terminal of the resistor R53 and is also electrically connected to the first switching terminal of the switch SW34. The other terminal of the resistor R53 is electrically connected to the ground wiring. Accordingly, the detection voltage generating unit 151, a reference voltage _{V ref} of the reference voltage generating unit 131 has generated by dividing to produce half the voltage of the reference voltage _{V ref,} and the detection voltage _{V t.}
Incidentally, by setting different values the electrical resistance of the two resistors R52, R53, rather than half the reference voltage _{V ref} to the voltage value of the detection voltage _{V t,} different values (e.g., third reference voltage _{V ref} 1 or a quarter).

  In addition, in order to suppress the power consumption in the voltage measuring apparatus 100, the electric resistance values of the two resistors R52 and R53 are set to a sufficiently large value. For example, when the voltage output from the constant voltage circuit 132 is 1 V, if the sum of the electric resistance values of the two resistors R52 and R53 is 100 MΩ, the current flowing through the two resistors R52 and R53 is 0.01 μA. . Then, since the power consumption of the two resistors R52 and R53 is 0.01 μW, if the power consumption of the entire voltage measuring device 100 is about 1 μW, the power consumption of the two resistors R52 and R53 is It can be suppressed to about 1%, and the influence on the power consumption of the entire voltage measuring apparatus 100 can be made minute.

FIG. 7 is a circuit diagram showing another example of the circuit configuration of the voltage measuring apparatus 100 according to this embodiment.
The voltage measurement device 100 shown in this figure is different from the voltage measurement device 100 shown in FIG. 6 in the configuration of the detection voltage generation unit 151, and the other parts are the same.
The detection voltage generation unit 151 includes a constant voltage circuit 136, for example.
Constant voltage circuit 136 is a circuit similar to the constant-voltage circuit 132, a voltage output by the detection voltage _{V t,} lower than the output voltage of the constant voltage circuit 132 (reference voltage _{V ref).} The input terminal of the constant voltage circuit 136 is electrically connected to the output terminal of the constant voltage circuit 132 and the second switching terminal of the switch SW34. The output terminal of the constant voltage circuit 136 is electrically connected to the first switching terminal of the switch SW34. The reference terminal of the constant voltage circuit 136 is electrically connected to the ground wiring. Accordingly, the detection voltage generator 151 generates a low predetermined detection voltage _{V t} than the reference voltage _{V ref.}
As described above, the detection voltage generation unit 151 may be configured by a resistance voltage dividing circuit or a constant voltage circuit. Further, the detection voltage generating unit 151, as long as a circuit that generates a predetermined detection voltage V _t with low power consumption, may be constituted by other circuits.

  The switch SW34 is a component having the same four terminals as the switch SW22. The first switching terminal of the switch SW34 is electrically connected to the connection point of the resistor R52 and the resistor R53. The second switching terminal of the switch SW34 is electrically connected to the output terminal of the constant voltage circuit 132. The common terminal of the switch SW34 is electrically connected to the second input terminal of the voltage comparison unit 154. The switching signal input terminal of the switch SW34 is electrically connected to the output terminal of the comparison voltage switching unit 133, and receives the switching signal generated by the comparison voltage switching unit 133.

The voltage comparison unit 154 (comparator) is a component having two input terminals and one output terminal. The voltage comparison unit 154 compares the potential of the first input terminal and the potential of the second input terminal, determines which one is higher, and outputs a signal indicating the determination result from the output terminal. The first input terminal of the voltage comparison unit 154 is electrically connected to one terminal of the capacitor C11. The second input terminal of the voltage comparison unit 154 is electrically connected to the common terminal of the switch SW34. Thus, a first input terminal of the voltage comparator unit 154 inputs the charging voltage v _c, which is charged in the capacitor C11.
If the switch SW34 by the switching signal is turned to the common terminal and the first switching terminal, a second input terminal of the voltage comparator unit 154 inputs the detected voltage V _t. At this time, the voltage comparison unit 154 compares the charging voltage _{v c} and detection voltage _{V t.} The switch SW34 and the voltage comparison unit 154 in this state are an example of a detection voltage comparison unit.
When the switch SW34 conducts between the second switching terminal and the common terminal by the switching signal, the second input terminal of the voltage comparison unit 154 inputs the reference voltage _Vref . At this time, the voltage comparison unit 154 compares the charging voltage _{v c} and the reference voltage _{V ref.} The switch SW34 and the voltage comparison unit 154 in this state are an example of a reference voltage comparison unit.
In the following description, if the potential of the first input terminal is higher than the potential of the second input terminal, the determination result when the voltage comparison unit 154 determines “H”, and the potential of the first input terminal is the second. The determination result when it is determined that the potential is lower than the input terminal is described as “L”.

A circuit subsequent to the voltage comparison unit 154 is a digital circuit. The circuit subsequent to the voltage comparison unit 154 may be realized by a microcomputer executing a program. If a microcomputer having a voltage comparison function is used, the voltage comparison unit 154 can also be realized using the function of the microcomputer.
Similarly, if a microcomputer having a constant voltage generation function is used, the reference voltage generation unit 131 and the detection voltage generation unit 151 can also be realized using the functions of the microcomputer. If a microcomputer having a function of switching input / output of terminals is used, the switches SW22 and SW34 can also be realized by using the functions of the microcomputer.

  The timer circuit 155 is a circuit that receives a signal output from the voltage comparison unit 154 and counts elapsed time for a period in which the determination result of the voltage comparison unit 154 is “H” based on the input signal. Timer circuit 155 outputs data representing the elapsed time counted.

The charge / discharge switching unit 121 receives the signal output from the voltage comparison unit 154 and the data output from the timer circuit 155, and generates a switching signal for switching the switch SW22 based on the input signal and data.
The charge / discharge switching unit 121 has two modes. One is the target charging mode and the other is the measurement mode.
In the target charging mode, the charge / discharge switching unit 121 switches the switch SW22 to charge the capacitor C11. Based on the data output from the timer circuit 155, the charge / discharge switching unit 121 determines whether a predetermined time (hereinafter referred to as “target charging time” and represented by the symbol “T _c ”) has elapsed. The target charging time T _c is determined based on the time taken until the capacitor C11 is sufficiently charged so that the charging voltage v _c charged in the capacitor C11 can be regarded as being equal to the measurement target voltage V _s. The time is set to about 10 times the constant τ. When it is determined that the target charging time _Tc has elapsed, the charge / discharge switching unit 121 switches to the measurement mode.
In the measurement mode, when the determination result of the voltage comparison unit 154 is “H” based on the signal output from the voltage comparison unit 154, the charge / discharge switching unit 121 switches the switch SW22 to discharge the capacitor C11. When the determination result of the voltage comparison unit 154 is “L”, the switch SW22 is switched to charge the capacitor C11. Originally switched to the measurement mode, the capacitor C11 is charged to a voltage substantially equal measured voltage V _s, the charge and discharge switching unit 121 discharges the capacitor C11 by switching the switch SW22. Thereafter, the charge / discharge switching unit 121 repeats charging / discharging of the capacitor C11, and terminates one measurement when the second discharge is completed. After the measurement is completed, the charge / discharge switching unit 121 switches to the target charge mode.
Incidentally, the second time of charging and discharging in the measurement mode, so the reference discharge for measuring time T _ref ones and do not measure the reference discharge time T _ref is the first time step that after discharge of a single measurement May be switched to the target charging mode.

The comparison voltage switching unit 133 receives the signal output from the voltage comparison unit 154 and generates a switching signal for switching the switch SW34 based on the determination result represented by the input signal.
The comparison voltage switching unit 133 also has two modes. One is an object measurement mode and the other is a reference measurement mode.
In a subject measurement mode, the comparison voltage switching unit 133 switches the switch SW34, to compare the charging voltage _{v c} and detection voltage _{V t} to the voltage comparing unit 154. The comparison voltage switching unit 133 switches to the reference measurement mode when the determination result of the voltage comparison unit 154 changes from “H” to “L” based on the signal output by the voltage comparison unit 154.
In the reference measurement mode, the comparison voltage switching unit 133 switches the switch SW34 to the voltage comparison unit 154 when the determination result of the voltage comparison unit 154 is “L” based on the signal output from the voltage comparison unit 154. to compare the charging voltage _{v c} and the reference voltage _{V ref.} When the determination result of the voltage comparison section 154 is "H", the comparison voltage switching unit 133 switches the switch SW34, to compare the charging voltage _{v c} and detection voltage _{V t} to the voltage comparing unit 154. Thereafter, when the determination result of the voltage comparison unit 154 changes from “H” to “L”, the comparison voltage switching unit 133 switches to the target measurement mode.
The reference measurement mode, because they are for measuring the reference discharge time T _ref, if no measuring the reference discharge time T _ref, the determination result of the voltage comparator 154 in the target measurement mode "H" from "L" Even in the case of changing to, the target measurement mode may be continued without switching to the reference measurement mode.

ただし、αは、基準放電時間Ｔ_ｒｅｆに対する対象放電時間Ｔ_ｓの比（α＝Ｔ_ｓ／Ｔ_ｒｅｆ）である。 The target discharge time measurement unit 150 measures the target discharge time T _s based on the elapsed time counted by the timer circuit 155. The target discharge time measuring unit 150 outputs data representing the measured target discharge time T _s .
The reference discharge time measurement unit 160 measures the reference discharge time T _ref based on the elapsed time counted by the timer circuit 155. The reference discharge time measuring unit 160 outputs data representing the measured reference discharge time T _ref .
The measurement target voltage calculation unit 170 receives the data output from the target discharge time measurement unit 150 and the data output from the reference discharge time measurement unit 160, the target discharge time T _s represented by the input data, and the reference discharge time. based on the T _ref, and calculates the measured voltage _{V s.}
In this example, since the detection voltage V _t is half of the reference voltage V _ref , the calculation formula for the measurement target voltage calculation unit 170 to calculate the measurement target voltage V _s can be simplified as follows.

Here, α is a ratio of the target discharge time T _s to the reference discharge time T _ref (α = T _s / T _ref ).

Figure 8 is a flow chart illustrating an example of the flow of the voltage measurement process S410 that the voltage measuring apparatus 100 according to this embodiment measures a measurement target voltage V _s (the first half).
Figure 9 is a flow chart illustrating an example of the flow of the voltage measurement process S410 voltage measuring apparatus 100 according to this embodiment measures a measurement target voltage V _s (second half).
Figure 10 is a diagram showing an example of states of the respective units of the charging voltage v _c and a voltage measuring device 100 is charged in the capacitor C11 in this embodiment.
In the initial state, the charge / discharge switching unit 121 is in the target charging mode, and the comparison voltage switching unit 133 is in the target measurement mode.

In the target charging start step S511, the charge / discharge switching unit 121 switches the switch SW22 and starts charging the capacitor C11.
In the sense voltage switching step S512, the comparison voltage switching unit 133 switches the switch SW34, and enter the detection voltage _{V t} to the voltage comparator unit 154, to compare the charging voltage _{v c} and detection voltage _{V t.}
In the charging time initialization step S513, the charge / discharge switching unit 121 initializes the timer circuit 155 and sets the elapsed time (hereinafter, represented by the symbol “t”) counted by the timer circuit 155 to zero.

In the target charge comparison step S514, the voltage comparison unit 154 compares the charging voltage _{v c} and detection voltage _{V t,} and determines the size relationship. If the charge voltage _{v c} is equal to or less than the detection voltage _{V t,} repeated target charge comparison step S514. If the charge voltage _{v c} is greater than the detection voltage _{V t,} the process proceeds to charging time measurement start step S515.
In the charging time measurement start step S515, the timer circuit 155 starts measuring the elapsed time t.

In the charging time comparison step S516, the charge / discharge switching unit 121 acquires the elapsed time t measured by the timer circuit 155, compares the acquired elapsed time t with a predetermined target charging time _Tc , Determine the relationship. When the elapsed time t is shorter than the target charging time _Tc , the charging time comparison step S516 is repeated. When the elapsed time t is equal to or longer than the target charging time _Tc , the process proceeds to the target discharge start step S521.
In the target discharge start step S521, the charge / discharge switching unit 121 switches to the measurement mode. Since the determination result of the voltage comparison unit 154 is “H”, the charge / discharge switching unit 121 switches the switch SW22 and starts discharging the capacitor C11.
In the target discharge time initialization step S531, the target discharge time measurement unit 150 initializes the timer circuit 155 and sets the elapsed time t counted by the timer circuit 155 to zero.
In the target discharge time start step S532, the timer circuit 155 immediately starts measuring the elapsed time t because the determination result of the voltage comparison unit 154 is “H”.

In the target voltage comparison step S541, the voltage comparison unit 154 compares the charging voltage _{v c} and detection voltage _{V t,} and determines the size relationship. If the charge voltage _{v c} is greater than the detection voltage _{V t,} repeated target voltage comparison step S541. If the charge voltage _{v c} is equal to or less than the detection voltage _{V t,} the process proceeds to a subject discharge time stopping step S551.
In the target discharge time stop step S551, the timer circuit 155 stops the measurement of the elapsed time t because the determination result of the voltage comparison unit 154 is “L”.
In the target discharge time acquisition step S552, the target discharge time measuring unit 150 acquires the elapsed time t by the timer circuit 155 is measured, the target discharge time T _s.

In the reference charging start step S561, the charge / discharge switching unit 121 switches the switch SW22 to start charging the capacitor C11 because the determination result of the voltage comparison unit 154 is “L”.
In the reference voltage switching step S562, the comparison voltage switching unit 133 switches to the reference measurement mode because the determination result of the voltage comparison unit 154 has changed from “H” to “L”. Comparing the voltage switching unit 133, since the determination result of the voltage comparison section 154 is "L", switches the switch SW34, and inputs the reference voltage _{V ref} to the voltage comparing unit 154, the charging voltage _{v c} and the reference to the voltage comparator 154 The voltage V _ref is compared.
In the reference time initialization step S563, the reference discharge time measurement unit 160 initializes the timer circuit 155 and sets the elapsed time t counted by the timer circuit 155 to zero.

In charging voltage comparison step S564, the voltage comparison unit 154 compares the charging voltage _{v c} and the reference voltage _{V ref,} judges the size relationship. If the charge voltage _{v c} is less than or equal to the reference voltage _{V ref,} repeated charging voltage comparison step S564. If the charge voltage _{v c} is higher than the reference voltage _{V ref,} the process proceeds to the reference discharge time starting step S581.
In the reference discharge time start step S581, the timer circuit 155 starts measuring the elapsed time t because the determination result of the voltage comparison unit 154 is “H”.
In the reference discharge start step S571, the charge / discharge switching unit 121 switches the switch SW22 to start discharging the capacitor C11 because the determination result of the voltage comparison unit 154 becomes “H”.
In the sense voltage switching step S591, the comparison voltage switching unit 133, since the determination result of the voltage comparator 154 becomes "H", it switches the switch SW34, and enter the detection voltage _{V t} to the voltage comparator 154, the charge to compare the voltage _{v c} and the sensing voltage _{V t.}

In the reference voltage comparison step S592, the voltage comparison unit 154 compares the charging voltage _{v c} and detection voltage _{V t,} and determines the size relationship. If the charge voltage _{v c} is greater than the detection voltage _{V t,} repeated reference voltage comparison step S592. If the charge voltage _{v c} is equal to or less than the detection voltage _{V t,} the process proceeds to the reference discharge time stopping step S601.
In the reference discharge time stop step S601, the timer circuit 155 stops the measurement of the elapsed time t because the determination result of the voltage comparison unit 154 becomes “L”.
In the reference discharge time acquisition step S602, the reference discharge time measurement unit 160 acquires the elapsed time t measured by the timer circuit 155 and sets it as the reference discharge time _Tref .

In the discharge time ratio calculation step S611, the measurement target voltage calculation unit 170 measures the target discharge time T _s acquired by the target discharge time measurement unit 150 in the target discharge time acquisition step S552 and the reference discharge time acquisition in the reference discharge time acquisition step S602. Based on the reference discharge time T _ref acquired by the unit 160, the quotient α is calculated by dividing the target discharge time T _s by the reference discharge time T _ref .
In the measurement target voltage calculation step S612, the measurement target voltage calculation unit 170 calculates the measurement target voltage V _s based on the quotient α calculated in the discharge time ratio calculation step S611. Measured voltage calculation unit 170 outputs data representing the calculated measured voltage V _s.

Voltage measuring apparatus 100 in this embodiment, the voltage comparator 154 is constructed by analog circuits, it is compared in an analog manner and a charging voltage v _c and the reference voltage V _ref or sensing voltage V _t.

The voltage measurement apparatus 100 in this embodiment further includes a detection voltage comparison unit (switch SW34, voltage comparison unit 154).
The detection voltage comparator compares the above charging voltage v _c, and the detection voltage V _t, and determines the size relationship.
The target discharge time measurement unit 150 measures the target discharge time T _s based on the determination result determined by the detection voltage comparison unit.
The reference discharge time measurement unit 160 measures the reference discharge time T _ref based on the determination result determined by the detection voltage comparison unit.

Accordingly, the target discharge time T _s and the reference discharge time T _ref can be accurately measured, so that the measurement target voltage calculation unit 170 can accurately calculate the measurement target voltage V _s .

The voltage measuring apparatus 100 in this embodiment further includes a charging unit (switch SW22, resistor R12) and a reference voltage comparison unit (switch SW34, voltage comparison unit 154).
The charging unit charges the capacitor C11 with the applied voltage.
The reference voltage comparator compares the above charging voltage v _c, and the reference voltage V _ref, judges the size relationship.
The reference charging unit (charging and discharging switching unit 121), the measured voltage V _s is applied to the charging unit, on the basis of the determination result of the reference voltage comparison section determines, the charging voltage v _c is the reference voltage The capacitor C11 is charged until it reaches _Vref .

As a result, the time required to charge the capacitor C11 to the reference voltage _Vref can be shortened as compared with the case where the capacitor C11 is charged by applying the reference voltage _Vref to the charging unit, and the circuit configuration can be reduced. It can be simplified.

Voltage measuring apparatus 100 in this embodiment further includes a charging unit (switch SW22, resistor R12).
The charging unit charges the capacitor C11 with the applied voltage.
The target charging unit (charging and discharging switching unit 121), the measured voltage V _s is applied to the charging unit, charges the capacitor C11 up to a predetermined time (target charging time T _c) has elapsed.

Thus, the longer the target charging time T _c is sufficiently, can be regarded as the charging voltage v _c, which is charged in the capacitor C11 is equal to the measured voltage V _s.

The above-described storage device 800 (battery backup system), resistor R12 and a small consumption of the backup power supply voltage V _cc is a power supply voltage to itself by switching the charge voltage to the charge-discharge circuit composed of a capacitor C11 Measure with current.

Embodiment 3 FIG.
The third embodiment will be described with reference to FIGS.
Note that portions common to the storage device 800 described in Embodiment 2 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 11 is a circuit diagram showing an example of a circuit configuration of the voltage measuring apparatus 100 according to this embodiment.
The voltage measuring apparatus 100 includes a capacitor C11, a resistor R12, a switch SW22, a reference voltage generation unit 131, an A / D conversion circuit 156, a reference voltage comparison unit 134, a detection voltage comparison unit 157, a timer circuit 155, a charge / discharge switching unit 121, A target discharge time measurement unit 150, a reference discharge time measurement unit 160, and a measurement target voltage calculation unit 170 are included.

The A / D conversion circuit 156 (analog / digital converter) has a measurement input terminal, a reference input terminal, and a data output terminal (one for serial output and the same number of output data bits for parallel output). The A / D conversion circuit 156 performs analog-to-digital conversion on the voltage applied to the measurement input terminal with reference to the voltage applied to the reference input terminal, and outputs data representing the converted result from the data output terminal. Measurement input terminal of the A / D conversion circuit 156 are electrically connected to a connection point between the capacitor C11 and the resistor R12, to the input of the charging voltage v _c, which is charged in the capacitor C11. The reference input terminal of the A / D conversion circuit 156 is electrically connected to the output of the reference voltage generation unit 131 and inputs the reference voltage V _ref generated by the reference voltage generation unit 131. That, A / D conversion circuit 156, with reference to the reference voltage _{V ref,} the charging voltage _{v c} and analog-digital conversion, and outputs data representing the value of the charging voltage _{v c.} A / D conversion circuit 156, for example, a successive approximation type, a voltage obtained by dividing the reference voltage V _ref min, by comparing the charging voltage v _c, to determine each bit of the output data. The maximum value of the voltage that can be converted by the A / D conversion circuit 156 is the reference voltage V _ref , and even if a higher voltage is input from the measurement input terminal, data representing the maximum voltage in the measurable range (for example, all bits) Is data “1”). Since the reference voltage V _ref generated by the reference voltage generation unit 131 is lower than the measurement target voltage V _s input by the reference voltage generation unit 131, the A / D conversion circuit 156 directly measures the measurement target voltage V _s. I can't do it.

A circuit subsequent to the A / D conversion circuit 156 is a digital circuit. A circuit subsequent to the A / D conversion circuit 156 may be realized by a microcomputer executing a program. If a microcomputer having an analog / digital conversion function is used, the A / D conversion circuit 156 can also be realized by using the function of the microcomputer.
Similarly, if a microcomputer having a constant voltage generation function is used, the reference voltage generation unit 131 and the detection voltage generation unit 151 can also be realized using the functions of the microcomputer. If a microcomputer having a function of switching input / output of terminals is used, the switch SW22 can also be realized using the function of the microcomputer.

The reference voltage comparison unit 134 receives the data output from the A / D conversion circuit 156, and the voltage value represented by the input data is the maximum voltage (that is, the reference voltage V _ref ) that the A / D conversion circuit 156 can convert. It is determined whether or not there is. The reference voltage comparison unit 134 outputs data representing the determination result.
The detection voltage comparison unit 157 receives the data output from the A / D conversion circuit 156, and the voltage value represented by the input data is a predetermined detection voltage V _t (for example, the maximum voltage that can be converted by the A / D conversion circuit 156). It is determined whether it is larger or smaller than half of the above. The detection voltage comparison unit 157 outputs data representing the determination result.

  The timer circuit 155 counts the elapsed time, for example, starting from when the voltage measuring device 100 is turned on regardless of the determination results of the reference voltage comparison unit 134 and the detection voltage comparison unit 157, and represents the counted elapsed time. Is output.

The charge / discharge switching unit 121 receives the data output from the reference voltage comparison unit 134, the data output from the detection voltage comparison unit 157, and the data output from the timer circuit 155, and the determination result or progress represented by the input data. Based on the time, a switching signal for switching the switch SW22 is generated. The procedure by which the charge / discharge switching unit 121 switches the switch SW22 is the same as in the second embodiment.
Each of the target discharge time measurement unit 150 and the reference discharge time measurement unit 160 receives the data output from the detection voltage comparison unit 157 and the data output from the timer circuit 155, and determines the determination result or elapsed time represented by the input data. Based on this, the target discharge time T _s or the reference discharge time T _ref is calculated.

Figure 12 is a flow chart illustrating an example of the flow of the voltage measurement process S410 that the voltage measuring apparatus 100 according to this embodiment measures a measurement target voltage V _s (the first half).
Figure 13 is a flow chart illustrating an example of the flow of the voltage measurement process S410 voltage measuring apparatus 100 according to this embodiment measures a measurement target voltage V _s (second half).

In the target charging start step S511, the charge / discharge switching unit 121 switches the switch SW22 and starts charging the capacitor C11.
In the charging completion time calculating step S517, the charge / discharge switching unit 121 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the charging start time. The charge / discharge switching unit 121 calculates the charge completion time by adding a predetermined target charge time _Tc to the acquired charge start time.

  In the target charging completion determination step S518, the charge / discharge switching unit 121 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the current time. The charge / discharge switching unit 121 compares the acquired current time with the charge completion time calculated in the charge completion time calculation step S517, and determines whether or not the charge completion time has come. If it is determined that the current time is before the charging completion time, the target charging completion determination step S518 is repeated. When it is determined that the current time is after the charge completion time, the process proceeds to the target discharge start step S521.

In the target discharge start step S521, the charge / discharge switching unit 121 switches the switch SW22 to start discharging the capacitor C11.
In the target discharge time storage step S522, the target discharge time measurement unit 150 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the discharge start time. The target discharge time measurement unit 150 stores the acquired discharge start time.

In the target voltage measurement step S542, A / D conversion circuit 156 measures the charging voltage _{v c,} and outputs the data representing the voltage value of the measured charge voltage _{v c.}
In the target voltage comparison step S543, the detection voltage comparison unit 157 inputs the data A / D conversion circuit 156 in the target voltage measurement step S542 is output, and the charging voltage _{v c} of the input data representing a detection voltage _{V t} Are compared to determine the magnitude relationship. If the charge voltage _{v c} is greater than the detection voltage _{V t,} the flow returns to the target voltage measurement step S542. If the charge voltage _{v c} is equal to or less than the detection voltage _{V t,} the process proceeds to a subject discharge time calculating step S553.
In the target discharge time calculation step S553, the target discharge time measurement unit 150 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the discharge end time. The target discharge time measurement unit 150 calculates the target discharge time T _s by subtracting the discharge start time stored in the target discharge time storage step S522 from the acquired discharge end time.

  In the reference charging start step S561, the charge / discharge switching unit 121 switches the switch SW22 and starts charging the capacitor C11.

In the charge voltage measurement step S565, A / D conversion circuit 156 measures the charging voltage _{v c,} and outputs the data representing the voltage value of the measured charge voltage _{v c.}
In charging voltage comparison step S566, the reference voltage comparator 134, a charge voltage _{v c} to enter the data A / D converter circuit 156 has output the charging voltage measurement step S565, the input data representing a reference voltage _{V ref} Are compared to determine the magnitude relationship. If the charge voltage _{v c} is smaller than the reference voltage _{V ref,} the return to the charge voltage measurement step S565. If the charge voltage _{v c} is the reference voltage _{V ref} more, the process proceeds to the reference discharge start step S571.

In the reference discharge start step S571, the charge / discharge switching unit 121 switches the switch SW22 and starts discharging the capacitor C11.
In the reference discharge time storage step S582, the reference discharge time measurement unit 160 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the discharge start time. The reference discharge time measurement unit 160 stores the acquired discharge start time.

In the reference voltage measurement step S593, A / D conversion circuit 156 measures the charging voltage _{v c,} and outputs data representing the charging voltage _{v c} measured.
In the reference voltage comparison step S594, the detection voltage comparison unit 157 inputs the data A / D conversion circuit 156 by the reference voltage measurement step S593 is output, and the charging voltage _{v c} of the input data representing a detection voltage _{V t} Are compared to determine the magnitude relationship. If the charge voltage _{v c} is greater than the detection voltage _{V t,} the flow returns to the reference voltage measurement step S593. If the charge voltage _{v c} is equal to or less than the detection voltage _{V t,} the process proceeds to the reference discharge time calculating step S603.

In the reference discharge time calculation step S603, the reference discharge time measurement unit 160 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the discharge end time. The reference discharge time measuring unit 160 calculates the reference discharge time T _ref by subtracting the discharge start time stored in the reference discharge time storage step S582 from the acquired discharge end time.

In the discharge time ratio calculation step S611, the measurement target voltage calculation unit 170 measures the target discharge time T _s calculated by the target discharge time measurement unit 150 in the target discharge time calculation step S553 and the reference discharge time calculation in the reference discharge time calculation step S603. Based on the reference discharge time T _ref calculated by the unit 160, the quotient α is calculated by dividing the target discharge time T _s by the reference discharge time T _ref .
In the measurement target voltage calculation step S612, the measurement target voltage calculation unit 170 calculates the measurement target voltage V _s based on the quotient α calculated in the discharge time ratio calculation step S611.

Voltage measuring apparatus 100 in this embodiment, the charging voltage v _c and analog-digital conversion, after the digital data is compared with the charging voltage v _c and the reference voltage V _ref or sensing voltage V _t digitally Yes.
Supply voltage measuring device 100, since it is supplied from the rechargeable battery 801, a power supply voltage _{V cc,} is equal to the measured voltage _{V s.} For this reason, the measurement target voltage V _s exceeds the voltage range that the A / D conversion circuit 156 can measure, and the A / D conversion circuit 156 cannot directly measure the measurement target voltage V _s .
According to the voltage measuring apparatus 100 in this embodiment, the voltage to be measured exceeds the voltage range that can be measured by the A / D conversion circuit 156 by measuring the voltage within the voltage range that the A / D conversion circuit 156 can measure. V _s can be measured.

In the storage device 800 (battery backup memory system) described above, the voltage measurement device 100 (power supply voltage measurement method) is a charge / discharge circuit configured by a resistor R12 and a capacitor C11, and charge / discharge switching between charge and discharge of the circuit. A switching unit 121, a charging voltage switching unit (reference voltage comparison unit 134, charging / discharging switching unit 121) for switching the charging voltage, an A / D conversion unit (A / D conversion circuit 156) for measuring the voltage of the charging / discharging circuit, and And a timer unit (target discharge time measurement unit 150, reference discharge time measurement unit 160) for measuring the discharge time, and the backup power supply voltage V from the discharge times T _s and T _ref of the backup power supply voltage V _cc and the reference voltage V _{ref. cc} is derived.
Charging voltage switching unit, and the charging voltage to the battery voltage V _s, the charge and discharge switching unit 121, a charge operation mode of the charge-discharge circuit to charge a certain time the battery voltage V _s to the charging and discharging circuit. The charge / discharge switching unit 121 discharges the charge charged in the charge / discharge circuit by switching the operation mode of the charge / discharge circuit from charge to discharge. The A / D converter (A / D converter circuit 156) measures the voltage value (charge voltage v _c ) of the charge / discharge circuit. From the voltage value obtained from the A / D conversion unit and the timer value obtained from the timer unit, the CPU unit (detected voltage comparison unit 157, target discharge time measuring unit 150) from the start of discharge of the charge / discharge circuit to the detected voltage Is measured (target discharge time T _s ).
Next, the charging voltage switching unit sets the charging voltage to the reference voltage V _ref , and the charging / discharging switching unit 121 charges the charging / discharging circuit by setting the charging / discharging circuit mode to charging. When the voltage value obtained from the A / D conversion unit matches the reference voltage (the voltage value of the A / D converter becomes the maximum measured value), the CPU unit (reference voltage comparison unit 134) is the charge / discharge switching unit 121. To change the operation mode of the charge / discharge circuit to discharge. From the CPU unit (detection voltage comparator 157, the reference discharge time measuring unit 160) is a timer value obtained from the voltage value and a timer unit obtained from the A / D conversion unit, leading to the detection voltage V _t from the discharge start of the charging and discharging circuit Time (reference discharge time T _ref ) is measured.
The CPU unit (measurement target voltage calculation unit 170) calculates a backup power supply voltage (measurement target voltage V _s ) from the measured discharge time values (target discharge time T _s , reference discharge time T _ref ).

As a result, the power supply voltage _Vcc itself that is the power supply of the voltage measuring apparatus 100 can be measured. In addition, since a charge / discharge circuit using a capacitor is used without using active elements, the current consumption during measurement can be kept low, and even when the voltage is measured with the main power off, it is used for backup. It is possible to prevent the backup time of the original purpose RAM (volatile memory 802) from being shortened without consuming much power.

Embodiment 4 FIG.
The fourth embodiment will be described with reference to FIGS.
Note that portions common to the storage device 800 described in Embodiment 3 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 14 is a circuit diagram showing an example of the circuit configuration of the voltage measuring apparatus 100 according to this embodiment.
In addition to the configuration described in the third embodiment, voltage measurement apparatus 100 further includes a reference comparison interval determination unit 135, a detection comparison interval determination unit 158, and a conversion instruction unit 159.

Reference voltage comparator 134 compares the charging voltage v _c and the reference voltage V _ref, not only one large, outputs data representing the difference between the charging voltage v _c and the reference voltage V _ref.
Similarly, the detection voltage comparator 157 compares the charging voltage v _c and detection voltage V _t, and outputs the data representing the difference between the charging voltage v _c and the sensing voltage V _t.

Reference comparison interval determination section 135 inputs the data reference voltage comparator 134 is output, based on the input data, interval reference voltage comparator 134 compares the charging voltage v _c and the reference voltage V _ref (hereinafter Called "reference comparison interval"). The greater the difference between the charging voltage v _c and the reference voltage V _ref, the distance from the charge voltage v _c reaches the reference voltage V _ref, it is considered that there is still enough time, reference comparison interval may be longer . In contrast, when the difference between the charging voltage v _c and the reference voltage V _ref is small, the charging voltage v _c is considered soon reaches the reference voltage V _ref, it is necessary to shorten the reference comparison interval. Therefore, the reference comparison interval determination section 135, based on the difference between the charging voltage v _c and the reference voltage V _ref, a longer reference comparison interval the greater the difference between the charging voltage v _c and the reference voltage V _ref, the charge to shorten the reference comparison interval smaller the difference between the voltage v _c and the reference voltage V _ref, to determine a reference comparison interval.
The reference voltage comparison unit 134 waits for the reference comparison interval determined by the reference comparison interval determination unit 135 to elapse before performing the next comparison.

Detection comparator interval determination section 158 inputs the data detection voltage comparing unit 157 is output, based on the input data, the interval in which the detection voltage comparing unit 157 compares the charging voltage v _c and detection voltage V _t (hereinafter Called "detection comparison interval"). Similar to reference comparison interval as described above, the larger the difference between the charging voltage v _c and the sensing voltage V _t, the detection comparison interval may be longer, the smaller the difference between the charging voltage v _c and the sensing voltage V _t, the detection comparison It is necessary to shorten the interval. Based on the difference between the charging voltage v _c and the detection voltage V _t , the detection comparison interval determination unit 158 increases the detection comparison interval if the difference between the charging voltage v _c and the detection voltage V _t is large, and the charging voltage v _c. the detection so that the difference between the voltage V _t to shorten the detection comparison interval smaller, determines the detection comparison interval.
The detection voltage comparison unit 157 waits for the detection comparison interval determined by the detection comparison interval determination unit 158 to elapse before performing the next comparison.

While the reference voltage comparator 134 also does not compare well detection voltage comparator 157, there is no need to A / D conversion circuit 156 measures the charging voltage v _c. In the meantime, if the A / D conversion circuit 156 does not measure the charging voltage and enters a standby state, power consumption in the A / D conversion circuit 156 can be suppressed. If the A / D conversion circuit 156 does not perform analog-digital conversion, the reference voltage generation unit 131 does not need to generate the reference voltage V _ref . The power consumption in the reference voltage generation unit 131 can also be suppressed.

Based on the reference comparison interval determined by the reference comparison interval determination unit 135 and the detection comparison interval determined by the detection comparison interval determination unit 158, the conversion instruction unit 159 then causes the A / D conversion circuit 156 to charge the charge voltage v _c. Is calculated, and a signal that causes the A / D conversion circuit 156 and the reference voltage generation unit 131 to wait until the calculated time is generated.
The A / D conversion circuit 156 receives the signal generated by the conversion instruction unit 159 and enters a standby state or performs analog-digital conversion based on the input signal. Similarly, the reference voltage generation unit 131 receives the signal generated by the conversion instruction unit 159 and enters a standby state based on the input signal, or generates the reference voltage V _ref .

Figure 15 is a flow chart illustrating an example of the flow of the voltage measurement process S410 that the voltage measuring apparatus 100 according to this embodiment measures a measurement target voltage V _s (the first half).
Figure 16 is a flow chart illustrating an example of the flow of the voltage measurement process S410 voltage measuring apparatus 100 according to this embodiment measures a measurement target voltage V _s (second half).

In the target charging start step S511. The charge / discharge switching unit 121 switches the switch SW22 and starts charging the capacitor C11.
In the charging completion time calculating step S517, the charge / discharge switching unit 121 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the charging start time. The charge / discharge switching unit 121 calculates the charge completion time by adding a predetermined target charge time _Tc to the acquired charge start time.

  In the charge completion standby step S519, the charge / discharge switching unit 121 waits until the charge completion time. For example, the charge / discharge switching unit 121 sets the timer interruption to occur at the charging completion time, and sets the microcomputer to the standby mode. When the charging completion time is reached, a timer interruption occurs, and the charge / discharge switching unit 121 returns from the standby state.

In the target discharge start step S521, the charge / discharge switching unit 121 switches the switch SW22 to start discharging the capacitor C11.
In the target discharge time storage step S522, the target discharge time measurement unit 150 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the discharge start time. The target discharge time measurement unit 150 stores the acquired discharge start time.

In the target voltage measurement step S542, the conversion instruction unit 159 generates a signal indicating the measurement of the charging voltage _{v c} to the A / D conversion circuit 156. The reference voltage generation unit 131 receives the signal generated by the conversion instruction unit 159, returns from the standby state, and generates the reference voltage _Vref . A / D conversion circuit 156 inputs the signal conversion instructing unit 159 generates returns from the standby state, with reference to the reference voltage V _ref of the reference voltage generating unit 131 has generated, measures the charging voltage v _c. After the measurement, A / D conversion circuit 156 outputs the data representing the voltage value of the measured charge voltage v _c. The reference voltage generation unit 131 and the A / D conversion circuit 156 return to the standby state.

In the target voltage comparison step S543, the detection voltage comparison unit 157 inputs the data A / D converter circuit 156 has output the target voltage measuring step S542, from the charging voltage _{v c} of the input data representing the detected voltage _{V t} By subtracting, the difference between the two is calculated. If the calculated difference is a positive value (that is, when the charging voltage v _c is greater than the detection voltage V _t), the process proceeds to a subject compared interval determination step S544. If the calculated difference is 0 or less (that is, when the charging voltage v _c is equal to or less than the detection voltage V _t), the process proceeds to a subject discharge time calculating step S553.
In the target comparison interval determination step S544, the detection comparison interval determination unit 158 determines the detection comparison interval based on the difference calculated by the detection voltage comparison unit 157 in the target voltage comparison step S543. For example, the detection comparison interval determination unit 158 calculates the detection comparison interval by multiplying the difference calculated by the detection voltage comparison unit 157 in the target voltage comparison step S543 by a predetermined constant. For example, the lower limit value of the circuit time constant τ is obtained in advance in consideration of the error between the capacitance value of the capacitor C11 and the electric resistance value of the resistor R12, and the charging voltage v _C is calculated from the lower limit value of the circuit time constant τ as A / The minimum time required for the D converter circuit 156 to reduce the minimum voltage that can be discriminated (for example, if the output of the A / D converter circuit 156 is 8 bits is 1/256 of the reference voltage V _ref ) is calculated. The detection comparison interval determination unit 158 multiplies the difference calculated by the detection voltage comparison unit 157 in the target voltage comparison step S543 by the calculated minimum time to obtain a detection comparison interval.
In the target conversion time calculation step S545, the conversion instruction unit 159 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the current time. The conversion instruction unit 159 calculates the next conversion time by adding the detection comparison interval determined by the detection comparison interval determination unit 158 in the target detection comparison interval determination step S544 to the acquired current time.
In the target conversion standby step S546, the conversion instruction unit 159 waits until the conversion time calculated in the target conversion time calculation step S545. For example, the conversion instruction unit 159 sets the timer interrupt to occur at the conversion time, and sets the microcomputer to the standby mode. When the conversion time is reached, a timer interruption occurs, and the conversion instruction unit 159 returns from the standby state.
Thereafter, the process returns to the target voltage measurement step S542.

In the target discharge time calculation step S553, the target discharge time measurement unit 150 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the discharge end time. The target discharge time measurement unit 150 calculates the target discharge time T _s by subtracting the discharge start time stored in the target discharge time storage step S522 from the acquired discharge end time.
In the reference charging start step S561, the charge / discharge switching unit 121 switches the switch SW22 and starts charging the capacitor C11.

In the charge voltage measurement step S565, the conversion instruction unit 159 generates a signal indicating the measurement of the charging voltage _{v c} to the A / D conversion circuit 156. The reference voltage generation unit 131 receives the signal generated by the conversion instruction unit 159, returns from the standby state, and generates the reference voltage _Vref . A / D conversion circuit 156 inputs the signal conversion instructing unit 159 generates returns from the standby state, with reference to the reference voltage V _ref of the reference voltage generating unit 131 has generated, measures the charging voltage v _c. After the measurement, A / D conversion circuit 156 outputs the data representing the voltage value of the measured charge voltage v _c. The reference voltage generation unit 131 and the A / D conversion circuit 156 return to the standby state.

In charging voltage comparison step S566, the reference voltage comparing unit 134 inputs the outputs A / D conversion circuit 156 at the charging voltage measurement step S565 data, from the reference voltage _{V ref,} the charging voltage _{v c} the entered data represents By subtracting, the difference between the two is calculated. If the calculated difference is a positive value (that is, when the charging voltage v _c is smaller than the reference voltage V _ref), the process proceeds to the charging comparison interval determination step S567. If the calculated difference is 0 or less (that is, when the charging voltage _{v c} is the reference voltage _{V ref} or higher), the process proceeds to the reference discharge start step S571.
In the charging comparison interval determination step S567, the reference comparison interval determination unit 135 determines the reference comparison interval based on the difference calculated by the reference voltage comparison unit 134 in the charging voltage comparison step S566. For example, the reference comparison interval determination unit 135 calculates the reference comparison interval by multiplying the difference calculated by the reference voltage comparison unit 134 in the charging voltage comparison step S566 by a predetermined constant.
In the charge conversion time calculation step S568, the conversion instruction unit 159 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the current time. The conversion instruction unit 159 calculates the next conversion time by adding the reference comparison interval determined by the reference comparison interval determination unit 135 in the charging comparison interval determination step S5777 to the acquired current time.
In the charge conversion standby step S569, the conversion instruction unit 159 waits until the conversion time calculated in the charge conversion time calculation step S568.
Then, it returns to charge voltage measurement process S565.

In the reference discharge start step S571, the charge / discharge switching unit 121 switches the switch SW22 and starts discharging the capacitor C11.
In the reference discharge time storage step S582, the reference discharge time measurement unit 160 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the discharge start time. The reference discharge time measurement unit 160 stores the acquired discharge start time.

In the reference voltage measuring step S593, the conversion instruction unit 159 generates a signal indicating the measurement of the charging voltage _{v c} to the A / D conversion circuit 156. The reference voltage generation unit 131 receives the signal generated by the conversion instruction unit 159, returns from the standby state, and generates the reference voltage _Vref . A / D conversion circuit 156 inputs the signal conversion instructing unit 159 generates returns from the standby state, with reference to the reference voltage V _ref of the reference voltage generating unit 131 has generated, measures the charging voltage v _c. After the measurement, A / D conversion circuit 156 outputs the data representing the voltage value of the measured charge voltage v _c. The reference voltage generation unit 131 and the A / D conversion circuit 156 return to the standby state.

In the reference voltage comparison step S594, the detection voltage comparison unit 157 inputs the data A / D conversion circuit 156 by the reference voltage measurement step S593 is outputted from the charging voltage _{v c} of the input data representing the detected voltage _{V t} By subtracting, the difference between the two is calculated. If the calculated difference is a positive value (that is, when the charging voltage v _c is greater than the detection voltage V _t), the process proceeds to reference comparison interval determination step S595. If the calculated difference is 0 or less (that is, when the charging voltage v _c is equal to or less than the detection voltage V _t), the process proceeds to the reference discharge time calculating step S603.
In the reference comparison interval determination step S595, the detection comparison interval determination unit 158 determines the detection comparison interval based on the difference calculated by the detection voltage comparison unit 157 in the reference voltage comparison step S594. For example, the detection comparison interval determination unit 158 calculates the detection comparison interval by multiplying the difference calculated by the detection voltage comparison unit 157 in the reference voltage comparison step S594 by a predetermined constant.
In the reference conversion time calculation step S596, the conversion instruction unit 159 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the current time. The conversion instruction unit 159 calculates the next conversion time by adding the detection comparison interval determined by the detection comparison interval determination unit 158 in the reference comparison interval determination step S595 to the acquired current time.
In the reference conversion standby step S597, the conversion instruction unit 159 waits until the conversion time calculated in the reference conversion time calculation step S596.
Thereafter, the process returns to the reference voltage measurement step S593.

In the reference discharge time calculation step S603, the reference discharge time measurement unit 160 receives the data output from the timer circuit 155, acquires the elapsed time represented by the input data, and sets it as the discharge end time. The reference discharge time measuring unit 160 calculates the reference discharge time T _ref by subtracting the discharge start time stored in the reference discharge time storage step S582 from the acquired discharge end time.

In the discharge time ratio calculation step S611, the measurement target voltage calculation unit 170 measures the target discharge time T _s calculated by the target discharge time measurement unit 150 in the target discharge time calculation step S553 and the reference discharge time calculation in the reference discharge time calculation step S603. Based on the reference discharge time T _ref calculated by the unit 160, the quotient α is calculated by dividing the target discharge time T _s by the reference discharge time T _ref .
In the measurement target voltage calculation step S612, the measurement target voltage calculation unit 170 calculates the measurement target voltage V _s based on the quotient α calculated in the discharge time ratio calculation step S611.

Figure 17 is a graph showing an example of a change in power consumption of the charge voltage v _c and a voltage measuring device 100 is charged in the capacitor C11 in this embodiment.
Thus, if far from the voltage charging voltage v _c is the target (detection voltage V _t or the reference voltage V _ref), by lengthening the interval for measuring the charging voltage v _c, the power consumption of the voltage measuring device 100 Can be suppressed. Further, when close to the voltage charge voltage v _c is the target, by shortening the interval for measuring the charging voltage v _c, the target discharge time T _s and the reference discharge time T _ref can be accurately measured.

The voltage measurement apparatus 100 in this embodiment further includes a detection comparison interval determination unit 158.
The detection comparison interval determination section 158, based on the determination result of the detection voltage comparator 157 determines, when the difference between the charging voltage v _c and the detection voltage V _t is large, the above detection voltage comparator 157 increase the detection comparison interval for comparing the charging voltage v _c and the detection voltage V _t, when the difference between the charging voltage v _c and the detection voltage V _t is small, to shorten the detection comparison interval.
The detection voltage comparator 157, in accordance with the detection comparison interval the sensing comparator interval determination section 158 has determined is compared with the charging voltage v _c and the detection voltage V _t.

This allows the detection voltage comparing unit 157 to reduce the number of times for comparing the charging voltage v _c and detection voltage V _t, it is possible to suppress the power consumption of the voltage measuring device 100.

The voltage measurement apparatus 100 in this embodiment further includes a reference comparison interval determination unit 135.
The reference comparison interval determination section 135, based on the determination result of the reference voltage comparator 134 determines, when the difference between the reference voltage V _ref and the charging voltage v _c is large, the above reference voltage comparator 134 increase the reference comparison interval for comparing the charging voltage v _c and the reference voltage V _ref, if the difference between the reference voltage V _ref and the charging voltage v _c is small, to shorten the reference comparison interval.
The reference voltage comparator 134, according to the criteria compared intervals the reference comparison interval determination section 135 has determined is compared with the charging voltage v _c and the reference voltage V _ref.

This allows the reference voltage comparing unit 134 to reduce the number of times for comparing the charging voltage v _c and the reference voltage V _ref, it is possible to suppress the power consumption of the voltage measuring device 100.

In the described voltage measurement apparatus 100 (power supply voltage measuring method) or, A / D conversion interval in response to the voltage v _c of the charge and discharge circuit (reference comparison interval, detection comparison interval) by determining the, A / D conversion times The processing power of the voltage monitor unit is reduced.
The voltage measurement apparatus 100 (battery voltage measurement method) can confirm the transition of the discharge voltage by using the A / D converter (A / D conversion circuit 156). The CPU unit (detection comparison interval determination unit 158) determines that there is room in the time to reach the detection voltage V _t while the discharge voltage (charge voltage v _c ) obtained from the A / D conversion unit is high, The time interval for performing the A / D conversion process is wide. The closer the discharge voltage (charge voltage v _c ) is to the detected voltage V _t , the shorter the time interval for performing the A / D conversion process. Between the end of the A / D conversion process and the start of the next A / D conversion process, the current consumption during standby is suppressed by shifting the circuit to the low power consumption mode. With the above processing flow, the number of A / D conversion processes can be reduced, and the current consumption required for the power supply voltage measurement process can be reduced.

Embodiment 5 FIG.
The fifth embodiment will be described with reference to FIGS.
Note that portions common to the storage device 800 described in Embodiments 1 to 4 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 18 is a system configuration diagram showing an example of the overall configuration of the storage device 800 in this embodiment.
The storage device 800 further includes a measurement interval determination unit 840 in addition to the configuration described in the first embodiment.

The holding comparison unit 810 compares the measurement target voltage V _s measured by the voltage measuring apparatus 100 and the holding voltage V _min and determines not only which is larger, but also the measurement target voltage V _s and the holding voltage V _min . Output data representing the difference.
Measuring interval determining unit 840 inputs the data holding comparison unit 810 is output, based on the difference between the measured voltage V _s and the holding voltage V _min of the input data represented, the voltage measuring device 100 measured voltage Vs Is measured (hereinafter referred to as “measurement interval”). If the difference between the measurement target voltage V _s and the holding voltage V _min is large, it is considered that there is still a time allowance for the measurement target voltage V _s to drop to the holding voltage V _min, so the measurement interval may be long. . On the other hand, when the difference between the measurement target voltage V _s and the holding voltage V _min is small, it is considered that the measurement target voltage V _s will soon reach the holding voltage V _min , so it is necessary to shorten the measurement interval. Therefore, the measurement interval determination section 840, based on the difference between the measured voltage V _s and the holding voltage V _min, the measurement interval is long when the difference between the measured voltage V _s and the holding voltage V _min is greater, measured If the difference between the target voltage V _s and the holding voltage V _min is small, the measurement interval is determined so as to shorten the measurement interval.
The voltage measuring apparatus 100 enters a standby state after one measurement is completed, waits for the measurement interval determined by the measurement interval determination unit 840 to elapse, returns from the standby state, and performs the next measurement.

  FIG. 19 is a flowchart showing an example of the flow of erasure determination processing in which the storage device 800 in this embodiment determines data loss.

In the voltage measurement process S410, the voltage measuring apparatus 100 measures the power supply voltage _{V cc} of the rechargeable battery 801 and outputs, to the measured voltage _{V s.} After the measurement is completed, the voltage measuring device 100 enters a standby state.
In the holding comparison step S420, the holding comparison unit 810 calculates a difference between the two by subtracting the holding voltage V _min from the measurement target voltage V _s measured by the voltage measuring device 100 in the voltage measurement process S410. When the calculated difference is 0 or more (that is, when the measurement target voltage V _s is the holding voltage V _min or more), the process proceeds to the measurement interval determination step S425. When the calculated difference is a negative value (that is, when the measurement target voltage V _s is smaller than the holding voltage V _min ), the process proceeds to the disappearance determination step S430.

In the measurement interval determination step S425, the measurement interval determination unit 840 determines the measurement interval based on the difference calculated by the holding comparison unit 810 in the holding comparison step S420. For example, the measurement interval determination unit 840 calculates the measurement interval by multiplying the difference calculated by the holding comparison unit 810 in the holding comparison step S420 by a predetermined constant and adding another predetermined constant. For example, if it takes at least T seconds for the rechargeable battery 801 to be discharged due to power consumption in the storage device 800 and the power supply voltage V _cc to drop by 1 millivolt, the measurement interval determination unit 840 performs the holding comparison unit in the holding comparison step S420. Multiply the value calculated by 810 in millivolt units by T. In addition, since the rechargeable battery 801 is consumed by frequently measuring the power supply voltage _Vcc and the data stored in the volatile memory 802 is lost, the power supply voltage Vcc is overturned. The measurement interval determination unit 840 adds this to the multiplication result as a predetermined constant. The measurement interval determination unit 840 sets the addition result as the measurement interval.
In the measurement standby step S426, the voltage measurement apparatus 100 waits for the measurement interval determined by the measurement interval determination unit 840 in the measurement interval determination step S425 to elapse. After the measurement interval elapses, the voltage measurement device 100 returns from the standby state and returns to the voltage measurement process S410.

In the erasure determination step S430, the erasure determination unit 820 determines that the data stored in the volatile memory 802 has been lost (possibly), and generates erasure determination data.
In the disappearance determination storage step S440, the nonvolatile memory 830 stores the disappearance determination data generated by the disappearance determination unit 820 in the disappearance determination step S430.

Figure 20 is a graph showing one example of a change in power consumption of the power supply voltage V _cc and the voltage measuring apparatus 100 of the storage device 800 in this embodiment.

Voltage measuring device 100, the primary power supply apparatus 200 when turned off, in order to confirm whether the rechargeable battery 801 is fully charged, to measure the supply voltage V _cc. When the power supply voltage _Vcc is far from the holding voltage _Vmin , the measurement interval until the next measurement is lengthened. Thereby, the power consumption of the voltage measuring apparatus 100 can be suppressed. Further, the measurement interval is shortened as the power supply voltage _Vcc approaches the holding voltage _Vmin . Thereby, it is possible to accurately determine data loss.

The storage device 800 in this embodiment further includes a measurement interval determination unit 840.
The measurement interval determination unit 840 determines that the voltage measurement apparatus 100 performs the measurement when the difference between the measurement target voltage V _s and the holding voltage V _min is large based on the determination result determined by the holding comparison unit 810. a longer measurement interval for measuring a target voltage V _s, when the difference between the measured voltage V _s and the holding voltage V _min is small, to shorten the measurement interval.
The voltage measuring device 100, according to the measurement interval the measuring interval determining unit 840 is determined, measuring the measurement target voltage V _s.

As a result, the number of times the voltage measuring device 100 measures the power supply voltage _Vcc can be reduced, so that power consumption in the voltage measuring device 100 can be suppressed and the period in which the volatile memory 802 can hold data is lengthened. Can do.

In the voltage measurement apparatus 100 (power supply voltage measurement method) described above, the measurement interval is determined according to the measurement result of the battery power supply voltage _Vcc , thereby reducing the number of measurement processes and processing of the voltage monitor unit (voltage measurement apparatus 100). Reduce power.

The storage device 800 (battery backup system) described above can be used for power supply voltage measurement by reducing the current consumption in voltage measurement by changing the measurement interval based on the voltage measurement value (measurement target voltage V _s ). The consumption of the accompanying backup power supply (rechargeable battery 801) is reduced to reduce the influence on the original RAM (volatile memory 802) backup time.
The CPU unit (measurement interval determination unit 840) determines that there is room in the time required to reach the minimum data retention voltage (retention voltage V _min ) of the RAM (volatile memory 802) while the backup power supply voltage V _cc is high. And make the backup power supply voltage measurement time interval wide. The closer the power supply voltage V _cc is to the data holding minimum voltage (holding voltage V _min ), the shorter the voltage measurement execution time interval. During the power supply voltage measurement process from the end of the power supply voltage measurement process, the current consumption during standby is suppressed by shifting the voltage monitor unit (voltage measurement device 100) to the low power consumption mode. With the above processing flow, the number of power supply voltage measurements can be reduced, and the current consumption required for the backup power supply voltage measurement process can be reduced.

FIG. 3 is a system configuration diagram illustrating an example of an overall configuration of a storage device 800 according to Embodiment 1. FIG. 7 is a flowchart showing an example of a flow of erasure determination processing in which the storage device 800 according to Embodiment 1 determines data loss. FIG. 3 is a block configuration diagram illustrating an example of a functional block configuration of the voltage measurement apparatus 100 according to the first embodiment. The flowchart figure which shows an example of the flow of the voltage measurement process S410 in which the voltage measurement apparatus 100 in Embodiment 1 measures a measurement object voltage. Graph showing an example of a change in the charging voltage v _c, which is charged in the capacitor C11 in the first embodiment. FIG. 4 is a circuit diagram illustrating an example of a circuit configuration of a voltage measurement device 100 according to a second embodiment. FIG. 6 is a circuit diagram showing another example of the circuit configuration of voltage measurement apparatus 100 in the second embodiment. Flow chart illustrating an example of the flow of the voltage measurement process S410 that the voltage measuring device 100 in the second embodiment measures the measurement target voltage V _s (the first half). Flow chart illustrating an example of the flow of the voltage measurement process S410 voltage measuring apparatus 100 according to the second embodiment measures the measurement target voltage V _s (second half). Diagram showing an example of a state of each part of the charge voltage v _c and the voltage measuring apparatus 100 stored in the capacitor C11 in the second embodiment. FIG. 6 is a circuit diagram illustrating an example of a circuit configuration of a voltage measurement device 100 according to Embodiment 3. Flow chart illustrating an example of the flow of the voltage measurement process S410 that the voltage measuring device 100 according to the third embodiment measures the measurement target voltage V _s (the first half). Flow chart illustrating an example of the flow of the voltage measurement process S410 voltage measuring apparatus 100 according to the third embodiment measures the measurement target voltage V _s (second half). FIG. 6 is a circuit diagram illustrating an example of a circuit configuration of a voltage measurement device 100 according to a fourth embodiment. Flow chart illustrating an example of the flow of the voltage measurement process S410 that the voltage measuring device 100 according to the fourth embodiment measures a measurement target voltage V _s (the first half). Flow chart illustrating an example of the flow of the voltage measurement process S410 voltage measuring apparatus 100 according to the fourth embodiment measures a measurement target voltage V _s (second half). Graph showing an example of a change in power consumption of the charge voltage v _c and the voltage measuring apparatus 100 stored in the capacitor C11 in the fourth embodiment. FIG. 7 is a system configuration diagram illustrating an example of the overall configuration of a storage device 800 according to a fifth embodiment. FIG. 7 is a flowchart showing an example of a flow of erasure determination processing in which the storage device 800 in Embodiment 5 determines data loss. Graph showing an example of a change in power consumption of the power supply voltage V _cc and the voltage measuring apparatus 100 of the storage device 800 in the fifth embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Voltage measuring device, 120 Object charging part, 121 Charge / discharge switching part, 130 Reference charging part, 131 Reference voltage generation part, 132,136 Constant voltage circuit, 133 Comparison voltage switching part, 134 Reference voltage comparison part, 135 Reference comparison interval Determination unit, 140 discharge unit, 150 target discharge time measurement unit, 151 detection voltage generation unit, 154 voltage comparison unit, 155 timer circuit, 156 A / D conversion circuit, 157 detection voltage comparison unit, 158 detection comparison interval determination unit, 159 Conversion instruction unit, 160 reference discharge time measurement unit, 170 measurement target voltage calculation unit, 200 main power supply device, 800 storage device, 801 rechargeable battery, 802 volatile memory, 803 interface unit, 810 retention comparison unit, 820 disappearance determination unit, 830 Non-volatile memory, 840 measurement interval determination unit, C11 capacitor, 12, R52, R53 resistance, SW22, SW34 switch.

Claims (11)

In a voltage measuring device that measures a voltage to be measured, which is a measurement target,
A capacitor, a target charging unit, a reference charging unit, a discharging unit, a target discharging time measuring unit, a reference discharging time measuring unit, and a measuring target voltage calculating unit;
The target charging unit charges the capacitor up to the measurement target voltage,
The reference charging unit charges the capacitor to a predetermined reference voltage,
The discharging unit discharges the capacitor with a predetermined circuit time constant,
The target discharge time measurement unit is configured such that a charge voltage charged in the capacitor when the target charge unit charges the capacitor to the measurement target voltage and then the discharge unit discharges the capacitor is a predetermined detection voltage. Measure the time to become the target discharge time,
The reference discharge time measurement unit measures a time from when the reference charging unit charges the capacitor to the reference voltage until the charging voltage becomes the detection voltage when the discharging unit discharges the capacitor. As the reference discharge time,
The measurement target voltage calculation unit calculates a voltage value of the measurement target voltage based on the target discharge time measured by the target discharge time measurement unit and the reference discharge time measured by the reference discharge time measurement unit. A voltage measuring device characterized by the above. The voltage measurement apparatus according to claim 1, wherein the measurement target voltage calculation unit calculates a voltage value of the measurement target voltage using the following mathematical formula.

However, _{V s} is measured voltage, _{V t} is the detection _{voltage, V ref} is a reference voltage, _{T s} is the target discharge _{time, T ref} is the reference discharge time. The voltage measurement device further includes a detection voltage comparison unit,
The detection voltage comparison unit compares the charging voltage with the detection voltage to determine a magnitude relationship,
The target discharge time measurement unit measures the target discharge time based on the determination result determined by the detection voltage comparison unit,
3. The voltage measuring device according to claim 1, wherein the reference discharge time measurement unit measures the reference discharge time based on a determination result determined by the detection voltage comparison unit. The voltage measuring device further includes a detection comparison interval determination unit,
When the difference between the charging voltage and the detection voltage is large based on the determination result determined by the detection voltage comparison unit, the detection comparison interval determination unit determines whether the detection voltage comparison unit determines the charging voltage and the detection voltage. When the difference between the charging voltage and the detection voltage is small, the detection comparison interval is shortened.
The voltage measurement device according to claim 3, wherein the detection voltage comparison unit compares the charging voltage with the detection voltage according to a detection comparison interval determined by the detection comparison interval determination unit. The voltage measuring device further includes a charging unit and a reference voltage comparing unit,
The charging unit charges the capacitor with an applied voltage,
The reference voltage comparison unit compares the charging voltage with the reference voltage to determine a magnitude relationship,
The reference charging unit applies the measurement target voltage to the charging unit, and charges the capacitor until the charging voltage becomes the reference voltage based on a determination result determined by the reference voltage comparison unit. The voltage measuring device according to claim 1. The voltage measuring device further includes a reference comparison interval determination unit,
When the difference between the reference voltage and the charging voltage is large based on the determination result determined by the reference voltage comparing unit, the reference voltage comparing unit determines that the reference voltage comparing unit determines the charging voltage and the reference voltage. When the difference between the reference voltage and the charging voltage is small, the reference comparison interval is shortened.
The voltage measurement device according to claim 5, wherein the reference voltage comparison unit compares the charging voltage with the reference voltage according to a reference comparison interval determined by the reference comparison interval determination unit. The voltage measuring device further includes a charging unit,
The charging unit charges the capacitor with an applied voltage,
The voltage measurement according to claim 1, wherein the target charging unit applies the measurement target voltage to the charging unit and charges the capacitor until a predetermined time elapses. apparatus. A volatile memory, a rechargeable battery, the voltage measuring device according to any one of claims 1 to 7, a holding comparison unit, and a disappearance determination unit,
The volatile memory holds stored data when a voltage supplied as a power source is equal to or higher than a predetermined holding voltage,
The rechargeable battery supplies the charged voltage as a power source for the volatile memory,
The voltage measuring device measures the voltage charged in the rechargeable battery as the voltage to be measured,
The holding comparison unit compares the measurement object voltage measured by the voltage measuring device with the holding voltage, determines the magnitude relationship,
The erasure determination unit determines that the data stored in the volatile memory is lost when the voltage to be measured is smaller than the holding voltage based on the determination result determined by the holding comparison unit. Storage device. The storage device further includes a measurement interval determination unit,
The measurement interval determination unit is configured to measure the measurement interval at which the voltage measurement device measures the measurement target voltage when the difference between the measurement target voltage and the hold voltage is large based on the determination result determined by the holding comparison unit. When the difference between the voltage to be measured and the holding voltage is small, the measurement interval is shortened,
9. The storage device according to claim 8, wherein the voltage measuring device measures the voltage to be measured according to a measurement interval determined by the measurement interval determining unit. The storage device further includes a nonvolatile memory,
The storage device according to claim 8 or 9, wherein the nonvolatile memory stores data representing a determination result determined by the disappearance determination unit. In the voltage measurement method for measuring the voltage to be measured, which is the object of measurement,
Charge the capacitor to the voltage to be measured above,
Discharge the capacitor with a predetermined circuit time constant, measure the time until the charging voltage charged in the capacitor reaches a predetermined detection voltage, and set the target discharge time,
Charge the capacitor to a predetermined reference voltage,
Discharging the capacitor with the circuit time constant, measuring the time until the charge voltage reaches the detection voltage, and using as a reference discharge time,
A voltage measurement method comprising calculating a voltage value of the measurement target voltage based on the measured target discharge time and the measured reference discharge time.

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