JP2015027137A - Battery management circuit, power source management system using the same, and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce duplication of hardware resources in a power source management system equipped with a secondary battery.SOLUTION: A battery monitor part 304 performs at least one of (i) attaching/detaching state of a secondary battery pack 200, (ii) low voltage state of a battery voltage VBAT, and (iii) usable/unusable state of the secondary battery pack 200. A battery measurement part 306 measures battery voltage VBAT, charge/discharge current IBAT, and temperature T of the secondary battery pack, and converts them to digital data. A charging circuit 302 is configured to be able to charge the secondary battery pack by utilizing a DC voltage from an external power source, based on a state detected by the battery monitor part 304 and the information measured with the battery measurement part 306. A coulomb counter 308 measures charge/discharge current IBAT at a predetermined time interval, and by integrating them, calculates a total sum of a charged electric-charge amount or discharged electric-charge amount. A battery management circuit 300 is integrated on one semiconductor substrate.

Description

  The present invention relates to a power management system having a secondary battery.

  CPUs (Central Processing Units) that perform system control and signal processing, liquid crystal panels, wireless communication modules, etc. in various battery-powered electronic devices such as mobile phone terminals, digital cameras, tablet terminals, and notebook personal computers Each of the electronic circuits such as analog and digital circuits operates by receiving power from the secondary battery.

  In battery-driven electronic devices, detection of the remaining battery capacity is an indispensable function. There are two main methods for detecting the remaining capacity of the battery: (1) voltage method and (2) charge integration method, which will be described below.

  In the voltage method, the voltage of the battery (hereinafter also referred to as battery voltage) is measured, and the remaining capacity is estimated from the correspondence between the voltage and the state of charge (SOC). In the charge integration method, the charge current flowing into the battery and the discharge current flowing out from the battery (hereinafter collectively referred to as charge / discharge current or load current) are integrated to calculate the charge charge amount and discharge charge amount to the battery. Estimate capacity.

Special table 2012-533759 gazette JP 2011-066441 A JP 2010-019758 A JP-A-5-323001 JP 2011-123033 A

  In the voltage method, the battery voltage is measured during the battery discharge operation and charged based on the correspondence between the open circuit voltage (OCV) and the state of charge (SOC) measured in advance. The state (SOC) is obtained. On the other hand, the SOC obtained by the charge storage method represents a relative ratio of the current remaining capacity with reference to the fully charged battery capacity BATCAP, and is also referred to as a relative remaining capacity. The absolute remaining capacity (hereinafter, absolute remaining capacity) cannot be determined from the relative remaining capacity SOC obtained by the voltage method.

  What can be measured from the outside of the secondary battery is terminal voltage (referred to as battery voltage) VBAT, and OCV needs to be estimated from battery voltage VBAT. Here, the battery voltage VBAT shows a voltage value lower than the OCV, but this voltage drop is greatly influenced by the battery operating conditions, that is, the waveform of the load current IBAT, the temperature of the battery cell, and the deterioration state of the battery. .

  The reason why the battery voltage is lower than the open circuit voltage is that the internal resistance (equivalent resistance value) of the battery increases depending on the above operating conditions. As a method of correctly detecting the equivalent resistance value of a battery, assuming an equivalent circuit model of the battery, the impedance elements constituting the model, that is, the resistive, capacitive, and inductive impedance elements are identified and the characteristics of the battery are identified. There is a method to try to simulate exactly. FIGS. 1A and 1B are diagrams showing an equivalent circuit model of a battery. Zw in FIG. 1A is an impedance resulting from the diffusion process, and is also referred to as a Warburg impedance.

  When pursuing improvement in accuracy, the equivalent circuit model becomes complicated as shown in FIG. 1A, so that there is a disadvantage that the amount of calculation for calculating the equivalent resistance value increases, and calculation processing time and power consumption increase. Conversely, if the equivalent circuit model is simplified as shown in FIG. 1B in order to reduce the amount of computation, the estimation error may increase.

  In addition, the charge integration method integrates the charge charge amount and discharge charge amount during the actual charge operation and discharge operation. Therefore, the charge integration value is set to zero when complete discharge is completed, and the charge If the battery is charged until the battery voltage reaches the full charge voltage, the charge accumulated value at that time can be regarded as the full charge capacity, and the discharge charge amount is subtracted during the subsequent discharge operation. By doing so, an accurate absolute remaining capacity value can be obtained.

  However, during actual electronic equipment operation, before the system stops operating, the peripheral circuits stop operating and the necessary information and data are saved to a non-volatile storage medium. In this case, it is difficult to make the battery completely discharged. When a battery in an unknown charge state is attached, the relative value of the charge accumulation amount can be accurately obtained, but the absolute value remains unknown.

  FIG. 2 is a block diagram showing a power management system 101r according to the comparative technique examined by the present inventors. It should be noted that the power management system 101r in FIG. In the power management system 101r, a charging circuit 302r, a battery monitoring unit 304r, a battery measuring unit 306r, and a coulomb counter 308r are configured by being divided into two or more individual ICs (Integrated Circuits) or modules.

  The charging circuit 302r receives the DC voltage VEXT from an external power adapter and charges the secondary battery pack 200. Charging circuit 302r can switch between constant current charging and constant voltage charging, for example, and at the time of constant current charging, it detects battery current IBAT and controls the state of charge so that the detected current value approaches the target value. During constant voltage charging, the battery voltage is detected, and the state of charge is feedback-controlled so that the detected value of the battery voltage approaches the target value. In addition, for full charge detection, a voltage comparator for comparing the battery voltage with a threshold value, a voltage comparator for detecting an external DC voltage VEXT, and the like are included. In addition, it has a function of measuring the temperature of the battery for charge current control.

  The battery monitor unit 304r includes (i) detection of attachment / detachment when the secondary battery pack 200 is attached / detached, (ii) detection of an excessively low voltage of the battery voltage VBAT, which is an output of the battery cell 202, and (iii) a battery. The cell 202 can be used or not (dead battery detection) is detected.

  The battery measuring unit 306r measures the output voltage VBAT of the battery cell 202, the charging / discharging current IBAT to the battery cell 202, and the temperature T of the battery cell 202, and converts them into digital data.

  The coulomb counter 308r measures the charge / discharge current IBAT of the battery at a constant time interval (1 second or several seconds), and sets the amount of charge multiplied by the time interval as the charge amount or discharge amount at that time, and integrates this. Thus, the sum of the charge amount or the discharge charge amount is calculated.

  In this comparative technique, a charging circuit 302r, a battery monitoring unit 304r, a battery measuring unit 306r, and a coulomb counter 308r are respectively configured for voltage detection, current detection, and temperature detection, for example, current detection resistance, A / D conversion. Hardware, amplifiers, voltage comparators, etc. are duplicated, and hardware resources are wasted.

  The present invention has been made in view of these problems, and one exemplary object of one aspect thereof is to provide a battery management circuit capable of reducing duplication of hardware resources in a power management system including a secondary battery. is there.

  One embodiment of the present invention relates to a battery management circuit that manages a secondary battery pack. The battery management circuit is configured to execute at least one of (i) a state where the secondary battery pack is attached / detached, (ii) a state where the battery voltage of the secondary battery pack is low, and (iii) a state where the secondary battery pack is usable Battery monitor unit, battery voltage, charging / discharging current to the secondary battery pack, temperature of the secondary battery pack, the battery measuring unit for converting to digital data, the state detected by the battery monitor unit and the battery Based on the information measured by the measurement unit, the charging circuit configured to be able to charge the secondary battery pack using the DC voltage from the external power source, and the charging / discharging current of the secondary battery pack at predetermined time intervals And a coulomb counter that calculates the total amount of charge or discharge charge by measuring and integrating it, and is configured as a single semiconductor substrate or module. That.

  According to this aspect, hardware for detecting battery voltage, charge / discharge current, temperature, etc. required for charging the secondary battery, and required for detecting the remaining capacity of the secondary battery Since some or all of the hardware for detecting battery voltage, charge / discharge current, temperature, etc. can be shared, duplication of hardware resources can be reduced.

The battery measurement unit may include a first A / D converter that converts a detection voltage corresponding to each of the battery voltage, the charge / discharge current, and the temperature into a digital value. The coulomb counter may include a second A / D converter that converts a voltage drop of a current detection resistor provided in series with the secondary battery pack into a digital value. The accuracy of the second A / D converter may be higher than the accuracy of the second A / D converter.
Even when the system is in a resting state, a minute discharge current flows from the battery cell, and the remaining battery level changes. According to the aspect, the remaining capacity can be detected more accurately by configuring the second A / D converter used by the coulomb counter with high accuracy.

  Another aspect of the present invention relates to a power management system. The power management system includes a secondary battery pack, a power management circuit that receives a battery voltage from the secondary battery pack or a DC voltage from an external power source, and generates a power voltage stabilized at a predetermined level. A system controller that receives and operates and the battery management circuit described above may be provided.

  The system controller may be configured to be communicable with the battery management circuit, and may be configured to be able to calculate the remaining battery capacity based on the count value of the coulomb counter and the measurement result by the battery measuring unit.

  Another embodiment of the present invention is an electronic device. The electronic device may include the above-described power management system.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, duplication of hardware resources in a power management system provided with a secondary battery can be reduced.

FIGS. 1A and 1B are diagrams showing an equivalent circuit model of a battery. It is a block diagram which shows the power management system which concerns on the comparison technique which the present inventors examined. It is a block diagram of an electronic device provided with a power management system according to an embodiment. FIG. 4A is a diagram showing an equivalent circuit model of the secondary battery pack, and FIG. 4B is a waveform diagram of the battery voltage and the load current. It is a functional block diagram regarding the detection of the battery remaining capacity of the power management system which concerns on embodiment. It is a flowchart of the remaining capacity detection process of a power management system. It is a flowchart of the initial measurement process of FIG. It is a flowchart of the initial stage SOC estimation process of FIG. It is a flowchart of the SOC estimation process of FIG.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are physically directly connected, or the member A and the member B are electrically connected to each other. Including the case of being indirectly connected through other members that do not substantially affect the state of connection, or do not impair the functions and effects achieved by the combination thereof.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

  Further, in this specification, a reference numeral attached to a voltage signal, a current signal, or a resistor represents a voltage value, a current value, or a resistance value as necessary.

(System configuration)
FIG. 3 is a block diagram of an electronic device including the power management system 101 according to the embodiment.
The electronic device 100 is a battery-driven device, and includes a battery management circuit 300, a system controller 400, and a power management circuit 500 in addition to the secondary battery pack 200. The entire system related to power control in the electronic device 100 including the secondary battery pack 200, the battery management circuit 300, the system controller 400, and the power management circuit 500 is referred to as a power management system 101.

  The secondary battery pack 200 is, for example, a lithium ion battery, and includes a battery cell (single battery) 202, a protection circuit 204, and a thermistor 206. In order to take out the power output of the battery cell 202 to the outside, It has a negative terminal 210.

  One end of the thermistor 206 is connected to the negative electrode terminal 210 of the battery cell, and the other is connected to the temperature detection terminal 212. In this way, the thermistor 206 is incorporated in the secondary battery pack 200 as an example, and in order to measure the temperature of the battery cell 202, a thermistor or other type of temperature sensor is installed on the battery holder side of the device. It is also possible to attach so that it contacts.

  The system controller 400 controls the entire electronic device 100 in an integrated manner. The system controller 400 is mainly realized by a cooperative operation of a main processor 402 that is hardware, and an operating system 404, an application program 406, and a remaining capacity calculation program 408 that are software.

  The system controller 400 performs system control / management and peripheral circuit control under the operating system 404 operating on the main processor 402, and executes the application program 406 and the remaining capacity for estimating the remaining capacity of the battery. The arithmetic program 408 is executed.

  Further, the main processor 402 can communicate with the battery management circuit 300 and the power management circuit 500 via the communication bus 104, receives information from the battery management circuit 300 and the power management circuit 500, and states the battery status and power. Supply status can be monitored and controlled.

  An external power supply (also referred to as a power adapter, not shown) is detachable from the direct current (DC) power input terminal 102. In the state where the external power source is connected, the DC power input terminal 102 is supplied with the external DC voltage VEXT.

  The power management circuit 500 receives the system voltage VSYS and supplies a power supply voltage to the main processor 402 and other peripheral circuits constituting the system controller 400. The system voltage VSYS may be a battery voltage VBAT from the secondary battery pack 200 or a DC voltage VEXT from an external power source stabilized by the battery management circuit 300.

  The power management circuit 500 includes one or a plurality of channels CH1 to CHN power supply circuits. The power supply circuit for each channel is provided for each load, stabilizes the system voltage VSYS at a predetermined level, and supplies a DC power supply voltage to the corresponding load. For example, the power supply circuit of the first channel CH1 supplies the power supply voltage VDD to the system controller 400. The power supply circuit of another channel supplies a power supply voltage to a liquid crystal driver (not shown). The power supply circuit can be a linear regulator, a DC / DC converter, a charge pump circuit, or the like.

  The power management circuit 500 manages the start / stop timing of the voltage output of each of the plurality of channels CH1 to CHN and the supply power.

  The battery management circuit 300 mainly manages the secondary battery pack 200, more specifically, charges the secondary battery pack 200 and detects its state.

  The battery management circuit 300 includes a charging circuit 302, a battery monitor unit 304, a battery measurement unit 306, and a coulomb counter 308. The battery management circuit 300 includes an external input (EXTIN) terminal, a switch (SW) terminal, a system voltage (VSYS) terminal, a positive connection (BAT +) terminal, a negative connection (BAT-) terminal, a thermistor (TH) terminal, It has a ground (GND) terminal.

  The EXTIN terminal is connected to the DC power input terminal 102. The BAT + terminal and the BAT− terminal are connected to the positive terminal 208 and the negative terminal 210 of the secondary battery pack 200, respectively. The TH terminal is connected to the temperature detection terminal 212 of the secondary battery pack 200. The GND terminal is grounded.

  The charging circuit 302 is connected to the EXTIN terminal, BAT + terminal, VSYS terminal, and SW terminal.

  When a valid external DC voltage VEXT is supplied to the DC power input terminal 102, the charging circuit 302 stabilizes the voltage to generate a system voltage VSYS, and supplies the system voltage VSYS to the power management circuit 500 via the VSYS terminal. In addition, when the remaining capacity of the battery cell 202 decreases, the charging circuit 302 charges the secondary battery pack 200 by supplying the charging current ICHG to the battery cell 202 via the BAT + terminal.

  The charging circuit 302 can be switched between a constant current (CC) mode in which the charging current ICHG is constantly stabilized and a constant voltage (CV) mode in which the battery voltage VBAT is stabilized at a constant value. It has become. The charging circuit 302 may be configured with a linear power supply or a switching power supply, and the configuration is not limited.

  The power FET 108 is provided on a path from the positive terminal 208 of the secondary battery pack 200 to the power management circuit 500. The gate of the power FET 108 is connected to the switch terminal SW of the battery management circuit 300. The charging circuit 302 controls on / off of the power FET 108 and switches between a state in which the power management circuit 500 is driven by the battery voltage VBAT and a state in which the power management circuit 500 is driven by the system voltage VSYS.

  While the system controller 400 operates by receiving the system voltage VSYS stabilized by the charging circuit 302, the power consumption of the system controller 400 increases, exceeds the capacity of the external power supply, and the external DC voltage VEXT drops. As a result, power supply to the system controller 400 may be insufficient. Therefore, when the external DC voltage VEXT is low, the system controller 400 interrupts the charging of the battery cell 202 and turns on the power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) 108 to assist the power supply from the battery cell 202. .

  The battery monitor unit 304 includes (i) detection of attachment and detachment when the secondary battery pack 200 is attached and detached, (ii) detection of an excessively low voltage of the battery voltage VBAT that is an output of the battery cell 202, and (iii) a battery. The use / non-use detection (dead battery detection) of the cell 202 is performed, and the detected state of the battery cell 202 is transmitted to the charging circuit 302. The charging circuit 302 controls the charging operation based on the state information of the battery cell 202.

  The first A / D converter 310 receives the voltages of the BAT + terminal, the BAT− terminal, the TH terminal, and the GND terminal. The battery measuring unit 306 uses the first A / D converter 310 to output the output voltage VBAT of the battery cell 202, the charge / discharge current (hereinafter also referred to as charge / discharge current) IBAT to the battery cell 202, Measure temperature T and convert to digital data.

The first A / D converter 310 receives the battery voltage VBAT generated between the BAT + terminal and the BAT− terminal, and converts it into a digital value. Battery measuring unit 306, the digital value is obtained as the battery voltage value D _V of a battery voltage VBAT.

  The current detection resistor 106 is inserted in series with the battery cell 202 on the path of the charge / discharge current IBAT of the battery cell 202. In the present embodiment, the current detection resistor 106 is provided between the negative terminal 210 and the ground line, but the location is not particularly limited. For example, the current sensing resistor 106 may be inserted between the positive terminal 208 and the power FET 108.

The charge / discharge current IBAT of the battery cell 202 flows through the current detection resistor 106, and a voltage drop (referred to as current detection voltage) V _I proportional to the charge / discharge current IBAT is generated at both ends of the current detection resistor 106. The 2A / D converter 312 converts the current detection voltage _{V I} between BAT- terminal and the GND terminal to a digital value.

The resistance value of the current sensing resistor 106 is known. Therefore, the digital operation unit 307 of the battery measuring unit 306 generates a current detection value D _I1 indicating the charge / discharge current IBAT based on the digital value corresponding to the current detection voltage V _I and the resistance value of the current detection resistor 106. The magnitude of the current detection value D _{I1 represents} the magnitude of the charge / discharge current IBAT, and the sign of the current detection value D _I1 represents the direction of the charge / discharge current IBAT.

The temperature detection terminal 212 of the secondary battery pack 200 is pulled up to a constant voltage via the external resistor 110. A current flows to the thermistor 206 built in the secondary battery pack 200 via the resistor 110, so that the resistance value of the thermistor 206 is between both ends of the thermistor 206, that is, between the temperature detection terminal 212 and the negative electrode terminal 210. temperature detection voltage V _T corresponding to occur. Since the resistance value of the thermistor 206 changes according to the temperature change of the battery cell 202, the temperature detection voltage V _T is associated with the temperature of the battery cell 202 on a one-to-one basis. The first A / D converter 310 converts the temperature detection voltage V _T between the TH terminal and the BAT− terminal into a digital value. The digital calculation unit 307 of the battery monitor unit 304 converts a digital value corresponding to the temperature detection voltage V _T into a temperature value D _T indicating the temperature of the battery cell 202.

The first A / D converter 310 measures the battery voltage VBAT, the current detection voltage V _I , and the temperature detection voltage V _T in a time division manner. A single A / D converter is time-divisionally divided into three voltages. You may share with. In order to reduce power loss, the resistance value of the current detection resistor 106 is preferably designed as small as possible. Therefore, when the charging / discharging current IBAT is small, the current detection voltage V _I generated between both ends of the current detection resistor 106 is very small. So the front of the 1A / D converter 310, may be inserted an amplifier for amplifying the current detection voltage V _I.

The measured values measured by the battery measuring unit 306, that is, the output voltage value D _V of the battery cell, the charge / discharge current value D _I , and the temperature value D _T of the battery cell are output to the charging circuit 302 and used for charging operation control. The At the same time, in order to detect the state of charge (SOC) of the battery cell 202, it is read by the system controller 400 (remaining capacity calculation program 408) via the interface unit 314 and the communication bus 104 and used for calculation processing.

The 2A / D converter 312, like the first 1A / D converter 310 converts the current detection voltage _{V I} developed across current sensing resistor 106 to a digital value. The coulomb counter 308 uses the output value of the second A / D converter 312 to measure the charge / discharge current IBAT of the battery at a constant time interval (1 second or several seconds), and calculates the charge amount multiplied by the time interval. The total charge amount or discharge charge amount is calculated by accumulating the charge amount or discharge amount at the time point. This processing may be executed by the digital arithmetic unit 309.

  Even when the system is in a resting state, a minute discharge current flows from the battery cell 202 and the remaining battery capacity changes. Therefore, in order to accurately detect the remaining battery capacity, it is necessary to detect a minute charge / discharge current. Therefore, the second A / D converter 312 used by the coulomb counter 308 has a higher resolution than the first A / D converter 310 used by the battery measuring unit 306, and is slightly less than when the system is in a resting state. It is desirable to detect even a small amount of discharge charge, that is, a small charge / discharge current IBAT.

  The value calculated by the coulomb counter 308 (referred to as the charge count value CCNT) is read by the system controller 400 (remaining capacity calculation program 408) and used for detecting the remaining capacity of the battery, in the same manner as the battery measurement value. When a battery pack with an unknown remaining capacity is attached, initial measurement is performed by the battery measurement unit 306, the initial measurement value is read by the system controller 400 after the system is started, and the initial value of the coulomb counter is set. The

  The system controller 400 estimates the remaining battery capacity of the battery cell 202 based on the information of the secondary battery pack 200 acquired by the battery management circuit 300. The arithmetic processing by the system controller 400 will be described later.

  The above is the configuration of the power management system 101 according to the embodiment.

Next, the advantages will be described. The advantage of the power management system 101 becomes clear by comparison with the power management system 101r of FIG.
According to the power management system 101 of FIG. 3 according to the embodiment, the battery management circuit 300 includes the charging circuit 302 and a device for measuring the state of the battery, that is, the battery monitoring unit 304, the battery measuring unit 306, and the coulomb counter. By integrally configuring 308, hardware resources such as an A / D converter, an amplifier, a resistor, and a comparator can be shared, and overlapping functional blocks can be reduced.

  Next, the remaining capacity calculation process by the battery management circuit 300 and the system controller 400 will be described.

(Secondary battery model)
First, a secondary battery model that can be used for the estimation calculation processing will be described.

  4A is a circuit diagram showing an equivalent circuit model of the secondary battery, and FIG. 4B is a waveform diagram of the battery voltage and the load current.

As shown in FIG. 4A, in the present embodiment, the internal resistance RINT is defined as the sum of a fixed component RF and a fluctuation component RV.
RINT = RF + RV
The fixed component RF includes a fixed resistance component inherent to the battery that does not depend on the operating conditions of the battery, that is, the contact resistance between the electrode active material and the current collector, the electrical resistance of the electrode metal itself, and the like. Further, the fluctuation component RV includes a resistance value fluctuation depending on the operating condition of the battery, that is, a battery characteristic change depending on a battery temperature, a load current fluctuation, and a state of charge (SOC).

More specifically, the fluctuation component RV is defined as the sum of the fluctuation component (transient response component) RI based on the transient response of the current flowing therethrough and the fluctuation component (temperature dependent component RT) depending on the temperature T.
RV = RI + RT
Note that this equivalent circuit model should not be recognized as a publicly known technique, and is originally devised by the present inventors.

  Reference is made to FIG. It is assumed that the load current (discharge current) IBAT is zero before a certain time t0. Here, it is assumed that battery voltage VBAT before time t0 is equal to open circuit voltage OCV.

  When the load current IBAT increases at time t0, the battery voltage VBAT drops instantaneously. This drop amount VDROP is the sum of the voltage drop IBAT × RF of the fixed component RF and the voltage drop IBAT × RT of the temperature dependent component RT.

  Immediately after the load current IBAT begins to flow, the transient response component RI is zero. However, if the load current IBAT continues to flow, the transient response component RI changes according to the history of the past current that has flown so far. As the transient response component RI increases, the voltage drop IBAT × RI between both ends increases, and the battery voltage VBAT further decreases with time. The dependence of the past load current is not limited to the one at the temporary point, but the influence of the current fluctuation from several minutes to several tens of minutes remains. Therefore, the transient response component RI can be accurately described by taking into account the fluctuation history up to several minutes before the residual effect is particularly large.

When the battery voltage VBAT at a certain time is known, the open circuit voltage OCV can be estimated from the following equation.
OCV = VBAT + IBAT * RINT = VBAT + IBAT x (RF + RI + RT)

  The fixed component RF can be acquired in an initial measurement process S102 described later, or a value acquired in advance for a sample of the secondary battery can be used. The value of the fixed component RF acquired in advance is ZBAT1_pre, and the value acquired in the initial measurement process S102 is ZBAT1_init.

  For temperature-dependent component RT, use a secondary battery sample to obtain the relationship between temperature T and temperature-dependent component RT in advance by experiment or simulation, and create a table or relational expression (function) to correlate them. It is stored in the remaining capacity calculation program 408. The temperature dependent component RT calculated by this table or the relational expression is set as ZBAT2_pre (T).

  As can be seen from FIG. 4B, the transient response component RV at a certain time is considered to have a value corresponding to the history of the load current IBAT that has flown so far. Therefore, in the present embodiment, a value CCNTS_var based on the current IBAT flowing in the time interval is defined for a certain time interval that goes back from a certain time. This value CCNTS_var is a parameter indicating the influence degree of the past load fluctuation, and is also simply referred to as an influence degree hereinafter.

  The relationship between the influence degree CCNTS_var and the transient response component RV is acquired in advance by experiment or simulation, and a table or a relational expression (function) for associating them is stored in the remaining capacity calculation program 408. The transient response component RI calculated by this table or the relational expression is assumed to be ZBAT3_pre (CCNTS_var).

  As an example, the value CCNTS_var is calculated by weighting and adding the value CCNT of the coulomb counter acquired over a past fixed interval (for example, several seconds to several tens of seconds). Details of the influence degree CCNTS_var will be described later.

  FIG. 5 is a functional block diagram relating to detection of the remaining battery capacity of the power management system 101 according to the embodiment. The power management system 101 includes a battery measurement unit 700, a coulomb counter 702, and a remaining capacity detection unit 600.

  The battery measurement unit 700 corresponds to the battery measurement unit 306 in FIG. 3 and measures the battery voltage VBAT, the charge / discharge current IBAT, and the temperature T of the secondary battery pack 200. The coulomb counter 702 corresponds to the coulomb counter 308 in FIG. 3 and integrates the charge / discharge current IBAT at predetermined time intervals.

  The remaining capacity detection unit 600 corresponds to a part of the system controller 400 of FIG. 3, and is specifically realized by a combination of the main processor 402 and software. The remaining capacity detection unit 600 calculates the remaining capacity of the secondary battery pack 200, more specifically, the absolute remaining capacity and the relative remaining capacity, based on the battery voltage VBAT, the charge / discharge current IBAT, and the temperature T.

  The remaining capacity detection unit 600 includes a memory 602, an internal resistance calculation unit 604, a voltage drop calculation unit 606, an open-circuit voltage calculation unit 608, a first charge state estimation unit 610, a second charge state estimation unit 612, a coulomb counter correction unit 614, A battery capacity correction unit 616, an initial resistance calculation unit 620, and a deterioration evaluation unit 622 are provided.

  The memory 602 defines a correspondence relationship between a charge state (relative remaining capacity) SOC_ocv indicating a relative remaining amount with respect to the battery capacity BATCAP in a fully charged state of the secondary battery pack 200 and the open circuit voltage OCV of the secondary battery pack 200. Holds a table or function. As described above, this correspondence is acquired in advance.

  As described above, the internal resistance RINT of the secondary battery pack 200 is modeled as the sum of the fixed component RF and the fluctuation component RV, and the fluctuation component RV includes the transient response component RI and the temperature-dependent component RT. The internal resistance calculation unit 604 calculates the internal resistance RINT of the secondary battery pack 200 based on this model. The acquisition unit 604a calculates ZBAT1, which is a fixed component RF, based on a result of an initial measurement process described later. The acquisition unit 604b calculates ZBAT2, which is a transient response component RI, based on the history of the current flowing through the secondary battery pack 200. The count value CCNT of the coulomb counter 702 is used for the current history. The acquisition unit 604c acquires the temperature dependent component RT based on the temperature T. The count value CCNT of the coulomb counter 702 is used for the current history. These resistance components are added by the adder 605, and the internal resistance RINT is calculated.

  The voltage drop calculation unit 606 calculates the voltage drop VDROP by multiplying the internal resistance RINT by the charge / discharge current IBAT.

  The open-circuit voltage calculation unit 608 calculates the open-circuit voltage OCV of the secondary battery pack by adding the voltage drop VDROP to the current battery voltage VBAT.

  The first charge state estimation unit 610 obtains the current charge state SOC_ocv corresponding to the current open circuit voltage OCV based on the OCV-SOC correspondence stored in the memory 602.

  Second charging state estimation unit 612 calculates charging state SOC_cc based on coulomb counter value CCNT and battery capacity BATCAP.

  When the error between the two charge states SOC_ocv and SOC_cc exceeds the allowable value, the coulomb counter correction unit 614 corrects the value CCNT of the coulomb counter.

  The battery capacity correction unit 616 corrects the battery capacity BATCAP when the error exceeds the allowable value between the two charging states SOC_ocv and SOC_cc.

  The initial resistance calculation unit 620 generates an initial value of the fixed component ZBAT1 of the internal resistance RINT based on the battery voltage VBAT and the load current IBAT obtained as a result of the initial measurement process S102 executed immediately after the secondary battery pack 200 is detected. Calculate the value ZBAT1_init.

  The degradation evaluation unit 622 evaluates the degradation level α of the secondary battery pack 200 based on the initial value ZBAT1_init of the fixed component ZBAT1. The battery capacity correction unit 616 corrects the remaining battery level BATCAP in the initial state based on the deterioration degree α.

  The above is a functional block diagram of the power management system 101 regarding the remaining capacity detection. Hereinafter, the remaining capacity detection process of the power management system 101 will be specifically described.

  FIG. 6 is a flowchart of the remaining capacity detection process of the power management system 101. FIG. 7 is a flowchart of the initial measurement process S102 of FIG. FIG. 8 is a flowchart of the initial SOC estimation process S107 of FIG. FIG. 9 is a flowchart of the remaining capacity estimation process S108 of FIG.

Please refer to FIG. The presence or absence of the secondary battery pack 200 is determined by the battery monitor unit 304 of FIG. 3 (S101). Presence of the secondary battery pack 200, or identified on the basis of the terminal voltage V _T of the thermistor 206 for temperature measurement, or connect a known load to the battery can be detected based on the response of the battery at that time . When the secondary battery pack 200 is not detected (N in S101), the battery monitor unit 304 continues the detection operation of the secondary battery pack 200.

  When the secondary battery pack 200 is detected (Y in S101), an initial measurement process is performed (S102).

  The initial measurement process S102 will be described with reference to FIG.

  First, the positive terminal 208 of the secondary battery pack 200 is opened, that is, no load is applied (S102-1), the battery voltage VBAT1 at that time is measured in the no-load state, and is stored in the internal register (S102-2). ). Subsequently, a light load (referred to as a dummy load) with a fixed resistance is connected between the positive terminal 208 of the secondary battery pack 200 and the ground (Ground) (S102-3), and the battery voltage (VBAT0) immediately after that is connected. The load current (IBAT0) is measured (S102-4). VBAT0 and IBAT0 are stored in internal registers. A resistor built in the battery management circuit 300 can be used for the dummy load. Immediately after connecting the dummy load means before the influence of the transient response appears.

  Subsequently, the dummy load connected in step S102-1 is disconnected (S102-5). The VBAT0, IBAT0, and VBAT1 stored in the internal register are read by the remaining capacity calculation program 408 (remaining capacity detection unit 600) after the system controller 400 is started, and the initial SOC estimation process of the secondary battery pack 200 (S107 described later) ).

  When the measurement of the voltage and current is completed, the operation of the coulomb counter 308 is immediately started (S102-6). However, the battery capacity BATCAP, which is the initial value, is a temporary value and is inaccurate until the initial value is set later. However, the relative value (time difference) over time is accurate.

  Subsequently, the power FET 108 in FIG. 3 is turned on, and the battery voltage VBAT of the secondary battery pack 200 starts to be supplied to the power management circuit 500 that is a system load (S102-7).

  The above is the initial measurement process S102.

  Returning to FIG. When the initial measurement process (S102) is completed, the system controller 400 waits for activation (N in S103). When the system controller 400 is activated (Y in S103), the remaining capacity calculation program 408 becomes executable by the main processor 402 under the management of the operating system 404.

  If the remaining capacity of the secondary battery pack 200 is sufficient, the system controller 400 can be activated, and even if the remaining capacity of the secondary battery pack 200 is insufficient, the external power source connected to the DC power input terminal 102 has a predetermined power. If the supply is performed, the system controller 400 can be activated.

  Subsequently, the battery management circuit 300 determines whether or not the external DC voltage VEXT from the external power source is present (S104). Specifically, the battery management circuit 300 includes a comparator (not shown in FIG. 3) that compares the external DC voltage VEXT with a predetermined threshold, and the presence or absence of the external DC voltage VEXT is determined by this comparator. If valid external DC voltage VEXT is input (Y in S104) and secondary battery pack 200 has not reached the fully charged state, charging circuit 302 starts supplying charging power to secondary battery pack 200. (S105). The charging method by the charging circuit 302 is not particularly limited, and a known method or a method that can be used in the future is used. The charge state (S105) continues until the battery voltage VBAT reaches the charge end voltage VCHG_term (N in S106). When the battery voltage VBAT reaches the charge end voltage VCHG_term (Y in S106), the charging is stopped.

  Next, the initial SOC estimation process S107 of the secondary battery pack 200 is performed. The initial SOC estimation process S107 is executed in the system controller 400 based on the remaining capacity calculation program 408.

  The initial SOC estimation process S107 differs depending on whether the charge end voltage is reached by charging (Y in S106) or not (No in S104).

  The initial SOC estimation process S112 in the case where the charging is finished through the charging end voltage VCHG_term will be described.

  In the initial SOC estimation process S112, the value CCNT of the coulomb counter is initialized by the charge end voltage VCHG_term. When the end-of-charge voltage VCHG_term is the maximum charge voltage defined by the specifications of the secondary battery, that is, the full charge voltage (for example, 4.3 V for a lithium ion secondary battery), the battery capacity value BATCAP is Set the same value.

That is, in this case, the SOC value (= CCNT ÷ BATCAP × 100 [%]) obtained from the coulomb counter value CCNT is 100%. In consideration of system requirements or battery life, the end-of-charge voltage VCHG_term may be selected to be lower than the maximum charge voltage (for example, 4.2 V). In that case, the battery capacity value BATCAP is reduced by Equation (1) with reference to the operation end voltage VBAT_low.
BATCAP = BATCAP_max × (VCHG_term-VBAT_low) / (VBAT_max-VBAT_low)… (1)

  Here, BATCAP_max is the maximum capacity of the battery, VCHG_term is the end-of-charge voltage, VBAT_max is the maximum voltage (rated value) of the battery, and VBAT_low is the end-of-operation voltage of the battery. As the BATCAP_max, a rated capacity value of the secondary battery pack 200 or a premeasured value of a sample battery may be used. When the battery is deteriorated as described later, the degree of deterioration is further reflected in the capacity BATCAP.

  Here, the operation end voltage VBAT_low is not the `` discharge end voltage '' defined in JIS C8711, but the system shuts down normally when the system is shut down at the end of the system (saving necessary data to a nonvolatile storage medium, Etc.) is set as a voltage ensuring a sufficient operating voltage and remaining capacity.

  Initial SOC estimation processing S107 when charging is not performed (N in S104) will be described. When the battery pack is installed and there is no DC power input, charging is not performed, and the state of charge (SOC) and remaining capacity of the battery are unknown. The initial SOC estimation process S107 at this time will be described with reference to FIG.

  In the initial SOC estimation process S107 in FIG. 8, the equivalent circuit model of the internal resistance in FIG. 4A is used.

  First, the deterioration degree α of the secondary battery is calculated (S107-1). For the calculation of the deterioration degree α, values VBAT0, IBAT0, and VBAT1 measured when the battery is mounted and stored in the internal register in the above-described initial measurement process (S102 in FIG. 7) are used. In the waveform diagram of FIG. 4B, VBAT1 corresponds to the battery voltage VBAT before time t0, VBAT0 corresponds to the battery voltage VBAT immediately after time t0, and IBAT0 corresponds to the amount of load current IBAT. Correspond.

  Note that VBAT1 acquired in the initial measurement process S102 is not necessarily the OCV of the secondary battery. This is because the battery voltage VBAT does not coincide with the OCV when the secondary battery pack 200 is charged or discharged immediately before that and a sufficient relaxation time has not elapsed since the last use.

Subsequently, using the read value, an initial value ZBAT1_init of the internal resistance of the secondary battery pack 200 is calculated based on the formula (2). The term (VBAT1-VBAT0) / IBAT0 does not substantially include the voltage drop of the fluctuation component RF.By subtracting the temperature-dependent component ZBAT2_pre (T) from this value, the fixed component RF of the internal resistance is reduced. Calculated. This process is executed by the initial resistance calculation unit 620 in FIG.
ZBAT1_init = (VBAT1-VBAT0) / IBAT0-ZBAT2_pre (T) (2)

The present inventors repeatedly charge and discharge the secondary battery pack 200 using the fixed component ZBAT1_init calculated based on the current value IBAT and the voltage value VBAT measured by the initial measurement immediately after detection of the secondary battery pack 200. We found that it increased due to deterioration (cycle deterioration) caused by Therefore, the fixed component ZBAT1_pre in the unused state before deterioration is measured in advance and stored in the memory. The system controller 400 evaluates the deterioration level α of the secondary battery pack 200 based on the value ZBAT1_init calculated by the equation (2) and the value ZBAT1_pre measured in advance. The deterioration degree α is evaluated by the deterioration evaluation unit 622 shown in FIG. This deterioration degree α is defined by, for example, Expression (3), and the value increases as the deterioration progresses.
α = (ZBAT1_init-ZBAT1_pre) / ZBAT1_pre (3)

  The deterioration degree α can be used for managing the life of the battery.

  In addition, the present inventors have found that the deterioration degree α calculated by the expression (3) has a correlation with the deterioration of the capacity of the secondary battery. Therefore, in the present embodiment, the deterioration degree α is reflected in the battery capacity BATCAP. Specifically, the corrected capacity BATCAP ′ is calculated as BATCAP ′ = (1−α) × BATCAP. This process is executed by the battery capacity correction unit 616 of FIG.

  As described above, according to the battery management circuit 300 according to the embodiment, in the initial state, by measuring the specific resistance value RF immediately after flowing the load current IBAT, the secondary battery pack is based on the resistance value. The degradation degree α of 200 can be evaluated, and furthermore, it can be reflected in the battery capacity BATCAP.

  If the initial measurement values VBAT0, IBAT0, and VBAT1 cannot be obtained for some reason as error processing, the rated capacity value BATCAP_max is set to the battery capacity BATCAP assuming that the degree of deterioration is 0 (no deterioration). Good.

Subsequently, an initial value VDROP_init of the voltage drop value VDROP is calculated (S107-2). Specifically, a dummy load is connected to the secondary battery, and the load current IBAT_init and the battery voltage VBAT_init at that time are measured. Then, the initial value VDROP_init of the voltage drop value VDROP is calculated from the equation (4) (S107-2).
VDROP_init = IBAT_init × (ZBAT1_init + ZBAT2_pre (T) + ZBAT3_pre (CCNTS_var))… (4)
The impedance term (ZBAT1_init + ZBAT2_pre (T) + ZBAT3_pre (CCNTS_var)) is calculated by the internal resistance calculator 604 in FIG. 5, and the voltage drop VDROP_init is calculated by the voltage drop calculator 606 in FIG.

The initial value OCV_init of the open circuit voltage OCV is estimated from the equation (5) using the initial voltage drop value VDROP_init thus obtained (S107-3). This estimation is performed by the open circuit voltage calculation unit 608.
OCV_init = VBAT_init + VDROP_init (5)

  The system controller 400 is provided with an OCV-SOC table SOC = table (OCV) indicating the correspondence between the open circuit voltage OCV and SOC (charge state). The SOC represents the current remaining capacity ratio (% in this embodiment) based on the fully charged capacity.

  The system controller 400 refers to this table and estimates the SOC initial value SOC_ocv_init = table (OCV_init) corresponding to the current estimated open circuit voltage OCV_init (S107-4). This estimation is performed by the first charge state estimation unit 610 of FIG.

Further, the initial remaining capacity CCNT_init is calculated according to the equation (6) (S107-5), and is set as an initial value in the coulomb counter (S107-6). BATCAP is the battery capacity. This process is executed by the coulomb counter correction unit 614 of FIG.
CCNT_init = SOC_ocv_init [%] / 100 × BATCAP (6)

  When the secondary battery is deteriorated as described above, the deterioration degree α is reflected in the battery capacity BATCAP.

  Returning to FIG. Through the processing so far, the initial value SOC_ocv_init of the battery remaining capacity relative to the state of charge (SOC) of the battery, that is, the fully charged state, and the initial value CCNT_init of the absolute battery remaining capacity can be estimated.

  Subsequent steps S108, S109, and S110 correspond to a remaining capacity estimation process during the battery discharging operation. The remaining capacity estimation process S108 is repeatedly performed at regular time intervals (for example, several seconds) until the battery voltage falls below the operation end voltage VBAT_low (S109).

  The remaining capacity estimation process S108 will be described with reference to FIG.

  The current battery voltage VBAT (n) and discharge current IBAT (n) are measured at a predetermined cycle by the battery measuring unit 700 (S108-1). n represents the measurement time and is incremented for each measurement.

The degree of influence CCNTS_var based on the load fluctuation history is calculated using the value CCNT of the coulomb counter (S108-2). For this purpose, the past coulomb counter value CCNT for several minutes is always stored. The influence degree CCNTS_var (n) of the current load fluctuation history is defined by Expression (7).
CCNTS_var (n) = Σ _{p = 0: m} [{CCNT (np) -CCNT (np-1)} * K_dec (p)] (7)

Here, CCNTS_var is the degree of influence of the load fluctuation history, CCNT is a coulomb counter value, and K_dec is an attenuation coefficient with time. "n" represents the current time point, "n-1" represents the previous measurement point, and "np" represents the p previous measurement time point. “m” is the number of past samples included in the influence level of the history.
The acquisition unit 604b of the internal resistance calculation unit 604 in FIG. 5 calculates the influence degree CCNTS_var (n) at each time n, and acquires the transient response component ZBAT2 based on the result.

  CCNT (n-p) -CCNT (n-p-1) corresponds to a current at time (n-p) p times before the current time n, and K_dec (p) is a weighting coefficient at time (n-p).

For example, if the measurement time interval is 1 second and the coulomb counter value for the past 2 minutes is held, the number of samples stored in the coulomb counter value is m = 120, and the size of the coulomb counter is 32 bits. In other words, a large buffer of 3840 bits must be prepared, and in the case of hardware implementation, the register amount may become very large. Even in the case of software implementation, the storage area and the calculation amount can be very large. Therefore, this register is stored discretely at a time interval of about 10 seconds and reduced to a buffer amount of about m = 10. Furthermore, the decay coefficient K_dec, which depends on the passage of time, depends on the transient response of the battery, and its decay curve is difficult to express with a simple formula, but it is regarded as a simple exponential decay with a power of 2 and the calculation is simplified. It is desirable to make it. This is because the power of 2 arithmetic processing can be executed by bit shift. For example, the coefficient K_dec (p) for the p time before the current time n is defined as follows.
K_dec (p) = 2 ^-p

  It has been experimentally confirmed that the use of the above reduction in the number of samples and simplification of the attenuation coefficient do not lead to an increase in error. Even if it is a simple calculation, since the influence of the load fluctuation history is very large, it is considered that the effect of reducing the error is great.

  Considering the characteristics of the battery, the transient response due to the electrochemical impedance due to charge transfer / diffusion and the electrical capacitive impedance due to the electric double layer structure generally shows a decay curve with a long decay time. Strictly speaking, an integral operation is required to correctly calculate the influence of the load fluctuation. By replacing it with simple calculation, efficient estimation accuracy can be improved.

Subsequently, the voltage drop VDROP is calculated based on the equation (8) (S108-3).
VDROP (n) = IBAT (n) x (ZBAT1_pre + ZBAT2_pre (T) + ZBAT3_pre (CCNTS_var (n)) (8)
This calculation process is executed by the voltage drop calculation unit 606 in FIG.

And an open circuit voltage (OCV) is estimated based on Formula (9) (S108-4). This process is executed by the open-circuit voltage calculation unit 608 in FIG.
OCV (n) = VBAT (n) + VDROP (n) (9)

  Then, an estimated value SOC_ocv of the state of charge (SOC) is obtained by referring to the table (S108-4). This is executed by the first charging state estimation unit 610 of FIG.

  Where IBAT (n), VBAT (n), and VDROP (n) are the current value, voltage value, and voltage drop value at the current time point (n), respectively, and OCV (n) is the estimated open circuit voltage at the current time point. It is OCV.

On the other hand, the SOC can also be calculated from the value of the coulomb counter value CCNT and the battery capacity BATCAP (rated capacity or effective capacity). This process is executed by the second charge state estimation unit 612 of FIG.
SOC_cc (n) [%] = CCNT (n) / BATCAP (10)

  Here, the battery capacity BATCAP may have an error in calculating the initial estimated value. When discharging starts immediately after the completion of full charge, the voltage drop is large and the error tends to increase.In addition, when the initial state is calculated by estimating the state of charge of the battery with an unknown remaining capacity, the SOC initial value is also calculated. Or there may be an error in estimating the degree of deterioration.

  Therefore, if there is a difference between the SOC value SOC_ocv derived from open-circuit voltage estimation and the SOC value SOC_cc derived from the coulomb counter value, the initial value of the coulomb counter is considered to have an error, and correction to increase or decrease the coulomb counter value is performed. May be. For example, when (SOC_cc−SOC_ocv)> 5%, the charge amount (for example, 1%) corresponding to a predetermined ratio of the rated capacity is reduced from the coulomb counter. This process is executed by the coulomb counter correction unit 614 of FIG.

  At this time, it is preferable to reduce the same amount from BATCAP so that SOC_cc does not become discontinuous. This process is executed by the battery capacity correction unit 616 of FIG. Thereby, the error at the time of initial value estimation due to deterioration or the like is adaptively corrected later. Since the relative value of the coulomb counter is accurate, the calculation of the load fluctuation history is not affected, and the absolute value is corrected. Therefore, not only the SOC value but also the absolute value of the remaining capacity (in [mAh]) I can know.

  The above is the estimation calculation method of the state of charge (SOC) and remaining capacity of the battery by the battery management circuit 300 and the system controller 400 according to the embodiment.

  According to this method, the following advantages can be obtained.

  First, in the measurement of the initial state of the battery (S102), when a load current is temporarily passed through the battery, a part of the function of the battery monitor unit 304 can be used as a dummy load. For example, the battery monitor unit 304 has a function of detecting battery connection, but a circuit element used for this function may be used as a dummy load.

  Second, each time the secondary battery pack 200 in an unknown charging state is mounted, the initial state is measured (S102), so there is no need to have a nonvolatile memory for storing the charging state of the battery. .

  Third, the voltage method and the charge integration method are used in combination, and error correction is performed mutually. Thereby, the remaining capacity can be detected with higher accuracy than in the past.

  Fourth, when the electronic device 100 is in a resting state, it is possible to reduce power consumption by continuing only the accumulation of the charge amount by the coulomb counter 308 and stopping the open circuit voltage (OCV) estimation. Therefore, the open-circuit voltage estimation calculation process (S108) may be performed only during normal operation of the electronic device 100, and can be implemented by software. This means that the hardware of the battery management circuit 300 can be reduced. Note that the first A / D converter 310 may be stopped when the electronic device 100 is in a dormant state, and in this case, power consumption can be reduced.

  Fifth, the calculation of the internal resistance value RINT of the battery does not use an equivalent circuit model, but uses the sum of the fixed component RF and the fluctuation component RV, thereby eliminating complex calculations and reducing the amount of calculation. Time can be shortened and power consumption can be reduced.

  Sixth, since the fluctuation component of the internal resistance value RINT of the battery is calculated in consideration of the battery temperature, load fluctuation, characteristic fluctuation, and deterioration, the estimation error can be reduced.

  Seventh, since the state of charge (SOC) and remaining capacity of the battery are estimated when the device is started up and when the battery is installed, a nonvolatile storage medium (flash memory, etc.) for storing and holding the battery state when the system is stopped Do not need.

  Eighth, by causing the battery remaining capacity estimation device to operate in cooperation with the charging circuit, it is possible to immediately notify the remaining capacity estimation device at the time of charging without passing through software or other communication means. . Further, when measuring the initial state of the battery, a part of the functions of the charging circuit (charging current supply function and no-load / constant load selection function) can be used, and duplication of hardware can be avoided.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and various modifications may exist in each of those constituent elements, each processing process, and a combination thereof. Hereinafter, such modifications will be described.

  In the embodiment, the case where the remaining capacity estimation processing described in FIGS. 6 to 9 is performed by the combination of the battery management circuit 300 and the system controller 400 in FIG. 3 is described, but the present invention is not limited thereto.

  For example, the remaining capacity transition process described with reference to FIGS. 6 to 9 may be performed in the power management system 101r illustrated in FIG.

  Moreover, it is not necessary to employ all the arithmetic processes in FIGS. 6 to 9, and only a part of them may be employed, and a known technique may be used for the remaining part.

  In the embodiment, the case where the system controller 400 is configured by a combination of the main processor 402 and software has been described. However, the present invention is not limited to this, and the system controller 400 may be realized only by hardware. Of the functions of the system controller 400, some or all of the functions related to detection of the remaining capacity of the secondary battery may be incorporated in the battery management circuit 300.

  Conversely, part of the processing performed by the battery management circuit 300, for example, integration processing by the coulomb counter 308, may be performed by the system controller 400. Alternatively, part of the arithmetic processing in the battery measurement unit 306 may be performed by the system controller 400.

  Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate the principles and applications of the present invention, and the embodiments are defined in the claims. Many variations and modifications of the arrangement are permitted without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Electronic device, 101 ... Power management system, 102 ... DC power input terminal, 104 ... Communication bus, 106 ... Current detection resistor, 108 ... Power FET, 200 ... Secondary battery pack, 202 ... Battery cell, 204 ... Protection Circuit, 206 ... Thermistor, 208 ... Positive electrode terminal, 210 ... Negative electrode terminal, 212 ... Temperature detection terminal, 300 ... Battery management circuit, 302 ... Charging circuit, 304 ... Battery monitor unit, 306 ... Battery measurement unit, 308 ... Coulomb counter, 310 ... 1st A / D converter, 312 ... 2nd A / D converter, 314 ... Interface part, 320 ... Charging part, 322 ... Current control transistor, 324 ... Charge control part, 400 ... System controller, 402 ... Main processor, 404: operating system, 406: application program, 4 8 ... residual capacity calculation program 410 ... communication driver program, 500 ... power management circuit.

Claims (7)

A battery management circuit for managing a secondary battery pack,
A battery monitor configured to execute at least one of (i) a state in which the secondary battery pack is attached / detached, (ii) a state in which the battery voltage of the secondary battery pack is low, and (iii) a state in which the secondary battery pack is usable And
A battery measuring unit that measures the battery voltage, a charge / discharge current to the secondary battery pack, a temperature of the secondary battery pack, and converts the measured voltage into digital data;
A charging circuit configured to charge the secondary battery pack using a DC voltage from an external power source based on the state detected by the battery monitoring unit and the information measured by the battery measuring unit;
A coulomb counter that measures the charge / discharge current of the secondary battery pack at a predetermined time interval and calculates the total charge charge or discharge charge amount by accumulating the charge / discharge current;
And a battery management circuit comprising a single semiconductor substrate or module. The battery measurement unit includes a first A / D converter that converts a detection voltage corresponding to the battery voltage, the charge / discharge current, and the temperature into a digital value,
2. The battery management according to claim 1, wherein the coulomb counter includes a second A / D converter that converts a voltage drop of a current detection resistor provided in series with the secondary battery pack into a digital value. circuit.   The battery management circuit according to claim 2, wherein the accuracy of the second A / D converter is higher than the accuracy of the first A / D converter.   The battery management circuit according to claim 2, wherein the first A / D converter is configured to be stoppable. A secondary battery pack,
A power management circuit that receives a battery voltage from the secondary battery pack or a DC voltage from an external power supply and generates a power supply voltage stabilized at a predetermined level;
A system controller that operates in response to the power supply voltage;
The battery management circuit according to any one of claims 1 to 3,
A power management system comprising: The system controller is configured to be communicable with the battery management circuit,
6. The power management system according to claim 5, wherein the remaining capacity of the battery can be calculated based on a count value of the coulomb counter and a measurement result by the battery measurement unit.   An electronic device comprising the power management system according to claim 5.

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