JP2008154323A - Charger and method for detecting charged state - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely manage the charged state of a charger. <P>SOLUTION: The charger having a charging circuit 1, performing constant voltage charging of a charging object secondary batter RB by applying a constant voltage at least in the last stage of charging, is provided with a means VS for detecting the voltage applied to the charging object secondary batter RB during constant-voltage charging; and a means MM for storing correction information, indicating correspondence of the voltage applied to the secondary batter RB and the full-charge capacity during constant voltage charging for the charging object secondary batter RB. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charging device provided with a charging circuit that applies a constant voltage to a secondary battery to be charged at least at the end of charging to perform constant voltage charging, and a charging state detection method in the charging device.

In such a charging device, various charging states are managed when charging a secondary battery to be charged.
For example, as one of the management of the state of charge, in order to make it easier for the user or the like to grasp the state of charge, it is often performed to display how much charging has progressed in a percentage display or the like. ing.
For detecting the progress of charging of the secondary battery, for example, by accumulating the charging current after starting the charging, etc., to determine the amount of charge to the secondary battery after starting the charging, It is detected as a percentage of the total charge that is scheduled to be charged to the secondary battery.
As the planned total charge amount, it is common to use the full charge capacity of the secondary battery as described in, for example, Patent Document 1 below.
JP 2005-10032 A

However, if the full charge capacity of the secondary battery is used as it is as the planned total charge amount for detecting the progress of charging, an appropriate display can be performed for displaying the progress of charging on the display means. There was no case.
That is, when the full charge capacity of a secondary battery is measured in advance before connecting the secondary battery to the charging circuit, the applied voltage in constant voltage charging can be accurately measured when measuring the full charge capacity. Even if the charging voltage is set to a predetermined value, the charging voltage in the constant voltage charging of the charging circuit may vary from the predetermined voltage value when it is incorporated into a charging circuit that is actually used with the secondary battery. .
In such a state, if the full charge capacity measured in advance is used to detect the progress of charging, the charging voltage of the actual charging circuit varies from the predetermined voltage, so that the charging capacity of the charging circuit However, even if the battery is charged to a state of 100%, there is a case where the display indicating the progress of the charge does not reach 100%.
In addition, even when measuring the full charge capacity of a secondary battery after incorporating it into the actual charging circuit, the charging voltage of the charging circuit may fluctuate later due to various factors such as the operating environment. In such a case, the same problem as described above occurs.
As described above, the management of the progress of the charging has been described as one of the management of the charging state. However, there are many cases in which the charging state is inconvenient due to variations in the charging voltage in constant voltage charging.
The present invention has been made in view of such circumstances, and an object of the present invention is to enable accurate management of a charging state in a charging device.

  The first invention of the present application is a charging device provided with a charging circuit that applies a constant voltage to a secondary battery to be charged at least at the end of charging to perform constant voltage charging, and the charging target in the constant voltage charging Voltage correction means for detecting the voltage applied to the secondary battery of the battery, and a correction for indicating the correspondence between the voltage applied to the secondary battery and the full charge capacity in the constant voltage charging for the secondary battery to be charged Storage means for storing information.

That is, for the secondary battery to be charged, the correspondence between the voltage applied to the secondary battery during constant voltage charging and the full charge capacity when fully charged with the applied voltage is obtained in advance as correction information. deep.
When the constant voltage charging at the end of charging is performed in the charging process of the secondary battery, the voltage applied to the secondary battery in the constant voltage charging is detected, and the actual information is obtained using the correction information. Various correction processes are performed so that the full charge capacity corresponding to the charging voltage is set as a reference.

  According to a second aspect of the present application, in addition to the configuration of the first aspect of the invention, a charge amount detection unit that detects a charge amount of the secondary battery to be charged in a charging process, and the charge amount detection unit Charge state detection means for detecting the progress of charging of the secondary battery to be charged as a ratio of the charge amount to the planned total charge amount based on the detection information of the charge state, the charge state detection means, From the detection information of the voltage detection means and the correction information, the charging is configured to detect the progress of the charging in a state where a full charge capacity corresponding to the applied voltage is the planned total charge amount, and the charging The progress of the charging detected by the state detection means is configured to be displayed on the display means.

That is, for the secondary battery to be charged, the correspondence between the voltage applied to the secondary battery during constant voltage charging and the full charge capacity when fully charged with the applied voltage is obtained in advance as correction information. In addition, the correction information is used to display the progress of charging accurately corresponding to the actual charging operation of the charging device.
Therefore, when the secondary battery is charged at the end of charging in the charging process of the secondary battery, the voltage applied to the secondary battery in the constant voltage charging is detected, and the correction information is used to The degree of progress of charging based on the full charge capacity corresponding to the actual charging voltage is detected and displayed.

As the contents of the correction information, the reference applied voltage is set in addition to the information that directly associates the value of the applied voltage to the secondary battery with the value of the full charge capacity at the applied voltage. The ratio of the full charge capacity at the applied voltage to the full charge capacity at the reference applied voltage may be stored as a correction ratio in correspondence with the value of each applied voltage.
Therefore, in the detection of the progress of the charging, in addition to the method of calculating the value of the full charge capacity stored corresponding to the detected applied voltage as the planned total charge amount, A method may be used in which a value obtained as the planned total charge amount is calculated by dividing the value obtained as the planned total charge amount by the correction ratio stored in correspondence with the detected applied voltage, and as a result, according to the detected applied voltage. What is necessary is just to be calculated in a state where the full charge capacity becomes the planned total charge amount.

  Further, the third invention of the present application is to charge the degree of progress of charging in a charging device provided with a charging circuit that applies constant voltage to a secondary battery to be charged at least at the end of charging to perform constant voltage charging. In the charging state detection method for detecting the amount of charge to the secondary battery to be charged in the process and detecting the amount of charge detected as a percentage of the planned total charge amount, for the secondary battery to be charged, The correction information indicating the correspondence between the applied voltage to the secondary battery in the constant voltage charging and the full charge capacity is obtained in advance, the applied voltage to the secondary battery to be charged in the constant voltage charging is detected, From the detection information of the applied voltage to the secondary battery and the correction information, the degree of progress of the charge is detected in a state where the full charge capacity corresponding to the applied voltage becomes the planned total charge amount.

That is, for the secondary battery to be charged, the correspondence between the voltage applied to the secondary battery during constant voltage charging and the full charge capacity when fully charged with the applied voltage is obtained in advance as correction information. In addition, the correction information is used to detect the degree of progress of charging accurately corresponding to the actual charging operation of the charging device.
Therefore, when the secondary battery is charged at the end of charging in the charging process of the secondary battery, the voltage applied to the secondary battery in the constant voltage charging is detected, and the correction information is used to The degree of charge progress is detected based on the full charge capacity corresponding to the actual charge voltage.

Note that, as the content of the correction information, as in the second invention, information in which the value of the voltage applied to the secondary battery is directly associated with the value of the full charge capacity at the applied voltage. In addition, a reference applied voltage is set, and the ratio of the full charge capacity at the applied voltage to the full charge capacity at the reference applied voltage is corrected according to the value of each applied voltage. You may ask for it.
Therefore, in the detection of the progress of the charging, in addition to the method of calculating the value of the full charge capacity stored corresponding to the detected applied voltage as the planned total charge amount, A method of calculating a value obtained by calculating the full charge capacity as the planned total charge amount by dividing the value by the correction ratio obtained corresponding to the detected applied voltage may be used, and as a result, depending on the detected applied voltage. It may be calculated in a state where the full charge capacity becomes the planned total charge amount.

According to the first aspect of the invention, since the state of charge corresponding to the actual charge voltage in the charging device can be managed, the state of charge can be managed accurately.
In addition, according to the second aspect of the invention, since the progress of charging corresponding to the actual charging voltage in the charging device is detected and displayed, the progress of charging can be appropriately displayed.
In addition, according to the third aspect of the present invention, it is possible to detect the progress of charging corresponding to the actual charging voltage in the charging device.

Embodiments of a charging device and a charging state detection method of the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic circuit configuration in a state in which a secondary battery RB to be charged and a charging device BC are assembled and connected in a circuit manner.
In the present embodiment, a lithium ion battery is illustrated as the secondary battery RB.
The charging device BC includes a charging circuit 1 for charging the secondary battery RB, a voltage detection circuit 2 for detecting a charging voltage for the secondary battery RB, and a current integration circuit for integrating the current value detected by the current sensor 3. 4, a charging state detection unit 5 that detects the progress of charging of the secondary battery RB to be charged based on the detection information of the voltage detection circuit 2 and the current integration circuit 4, and the charge detected by the charging state detection unit 5 A level meter 6 as display means LM for displaying the degree of progress is provided.

The charging circuit 1 applies constant voltage to the secondary battery RB to be charged at least at the end of charging to perform constant voltage charging. As a stage before the constant voltage charging, a charging current of constant current is used. Constant current charging is performed by supplying the secondary battery RB. That is, it is a circuit of a type that charges the secondary battery RB by a so-called constant current-constant voltage charging method.
As a series of operations of this charging system, the battery voltage of the secondary battery RB is kept at a constant current until the battery voltage rises to a set voltage (in this embodiment, “4.1 V” is assumed as a design specification). When the secondary battery RB is charged and reaches the set voltage, the battery is charged at a constant voltage with the set voltage thereafter.
Such a charging circuit 1 can be constituted by, for example, a constant current circuit to which a limiter circuit that limits the output voltage to the above set voltage is added.

The voltage detection circuit 2 detects the charging voltage applied to the secondary battery RB from the charging circuit 1 and sends it to the charging state detection unit 5 as digital data.
In the present embodiment, the voltage detection circuit 2 functions as voltage detection means VS that detects the voltage applied to the secondary battery RB to be charged in constant voltage charging.

The current integration circuit 4 starts a process of integrating the current value obtained from the detection signal of the current sensor 3 at a certain period from the time when the start command is received from the charge state detection unit 5, and the result of the integration is converted into digital data. As shown in FIG.
Since the integrated value (in other words, the time integrated value of the charging current) of the charging current in a certain period corresponds to the amount of charge to the secondary battery RB, the current integrating circuit 4 is the secondary charging target in the charging process. It functions as charge amount detection means CS for detecting the charge amount to the battery RB.

The charge state detection unit 5 is mainly composed of a microprocessor and a memory 5a, and performs charge by executing “state display correction process” shown in the flowchart of FIG. 2 as one of a plurality of processing functions in charge. Detection of the degree of progress.
The progress of charging is indicated by how much of the total charge amount until the full charge (scheduled total charge amount) has already been charged, and the total charge amount to the secondary battery RB It is detected as a percentage of the charge amount. Accordingly, the charging state detection unit 5 functions as charging state detection means CP that detects the progress of charging.
The process of FIG. 2 is periodically executed during the charging period of the secondary battery RB.
When charging of the secondary battery RB is started, charging is initially performed by constant current charging, and a current having a constant current value is supplied from the charging circuit 1 to the secondary battery RB.
Along with this, the voltage of the secondary battery RB gradually increases.

During the constant current charging, even if the processing of FIG. 2 is executed, constant voltage charging has not been reached (step # 1), and the processing is immediately terminated.
Although the detailed description of detection of the progress of charging during constant current charging is omitted, it corresponds to the full charge capacity when the secondary battery RB to be charged is fully charged at the set voltage (4.1 V). The charge state detection unit 5 performs the calculation by calculating the ratio of the charge amount to the secondary battery RB to be charged.
The calculated progress of charging is displayed on the level meter 6.
Here, the amount of charge to the secondary battery RB uses data received from the current integrating circuit 4. As described above, the current integration circuit 4 integrates the supply current value from the charging circuit 1 to the secondary battery RB at a constant period from the time when the start command is received from the charging state detection unit 5.

When the charging of the secondary battery RB proceeds and the voltage of the secondary battery RB increases and reaches the set voltage (4.1 V) for constant voltage charging, the process shifts to constant voltage charging.
As the battery shifts to the constant voltage charging, the charging circuit 1 notifies the charging state detection unit 5 of the fact.
When the process of FIG. 2 is executed in the period after the transition to the constant voltage charging, it is notified that the charging circuit 1 has shifted to the constant voltage charging (step # 1), so the process proceeds to step # 2. Then, it instructs the voltage detection circuit 2 to measure the charging voltage and receives data of the measurement result.

When the measured value of the charging voltage at that time is obtained, the full charge capacity corresponding to the charging voltage is calculated (step # 3).
That is, there is no problem as long as the charging voltage in constant voltage charging output from the charging circuit 1 exactly matches the set voltage (4.1 V) as described above. The actual charging voltage of the charging circuit 1 may have a slight error, and the charging voltage may vary due to fluctuations in the operating environment of the charging circuit 1 (temperature fluctuations, etc.).
Such fluctuation of the charging voltage affects the current capacity when the actual full charge is reached.For example, the current capacity when the charging voltage is full when the charging voltage is lower than the above specification is It will fall slightly.

In such a case, as in the case of constant-current charging, if the degree of progress of charging is calculated based on the full charge capacity corresponding to the set voltage (4.1 V) of the design specification, the charging voltage at that time is used. Even when the full charge is reached, a state where the full charge display (for example, 100%) is not reached continues as the display of the progress of the charge.
Therefore, in order to appropriately display the progress of charging, the full charge capacity corresponding to the actual charging voltage is obtained.

For this process, the charging state detection unit 5 previously stores correction information indicating the correspondence between the voltage applied to the secondary battery RB and the full charge capacity in the constant voltage charging for the secondary battery RB to be charged. It is obtained and stored in the memory 5a which is the storage means MM.
Specific data of the correction information includes, for example, a full charge capacity of 9 Ah when the applied voltage in constant voltage charging is 4.05 V, a full charge capacity of 10 Ah when the applied voltage in constant voltage charging is 4.1 V, When the applied voltage in constant voltage charging is 4.15 V, the full charge capacity is stored as 11 Ah.
These numerical values are obtained by precisely setting the charging voltage in the constant voltage charging of the secondary battery RB to be charged to the respective voltage values and actually charging to the full charge to obtain the full charge capacity.
Although the measured value of the charging voltage obtained in step # 2 is located between these skipped voltage values, the full charge capacity corresponding to the measured value of the charging voltage is calculated from the above data by interpolation processing.

When the full charge capacity corresponding to the measured value of the charge voltage is obtained as described above, the degree of progress of charge is calculated based on the full charge capacity (step # 4).
Specifically, the charge amount data up to that point is taken in from the current integrating circuit 4, and the progress of the charge is calculated as a ratio of the taken charge amount to the full charge capacity obtained in step # 3.
In other words, the full charge capacity corresponding to the applied voltage detected by the voltage detection circuit 2 is calculated from the detection information of the voltage detection circuit 2 and the correction information stored in the memory 5a in the state where the planned total charge amount is reached. Then, the progress of charging is detected.
Then, the level of charge progress determined in this way is displayed on the level meter 6 (step # 5).
The charging state detection unit 5 periodically repeats the process of FIG. 2 to periodically detect the progress of charging and display the detection result.
As a result, even if the charging voltage for constant voltage charging varies, the progress of charging can be accurately displayed following the variation.

[Another embodiment]
Hereinafter, other embodiments of the present invention will be listed.
(1) In the above embodiment, the current value is detected using the current sensor 3 to detect the amount of charge to the secondary battery RB. The method for detecting the current value can be variously changed such as obtaining the value.
(2) In the above embodiment, the case where the charging device BC is provided with the level meter 6 which is the display means LM for displaying the detection result of the progress of charging is exemplified, but the charging device BC itself has a display means. You may comprise so that only the signal for displaying on the display means LM may be output, without providing LM.
(3) In the above embodiment, the process of FIG. 2 is described as being periodically executed during the charging period of the secondary battery RB. However, the correction is executed only once when fully charged. You may comprise.

The block block diagram concerning embodiment of this invention The flowchart concerning embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging circuit RB Secondary battery CP Charging state detection means CS Charge amount detection means MM Storage means VS Voltage detection means

Claims (3)

A charging device provided with a charging circuit that applies a constant voltage to a secondary battery to be charged at least at the end of charging to perform constant voltage charging,
Voltage detecting means for detecting an applied voltage to the secondary battery to be charged in the constant voltage charging;
A charging device comprising storage means for storing correction information indicating a correspondence relationship between a voltage applied to the secondary battery in the constant voltage charging and a full charge capacity of the secondary battery to be charged. A charge amount detecting means for detecting a charge amount to the secondary battery to be charged in a charging process;
Charge state detection means for detecting the progress of charging of the secondary battery to be charged as a ratio of the charge amount to the planned total charge amount based on detection information of the charge amount detection means;
The charging state detecting means includes
From the detection information of the voltage detection means and the correction information, the full charge capacity according to the applied voltage is configured to detect the progress of the charge in a state where the planned total charge amount is reached,
The charging device according to claim 1, wherein the charging device is configured to display a progress degree of the charging detected by the charging state detection unit on a display unit. The degree of progress of charging in a charging device provided with a charging circuit that applies a constant voltage to a secondary battery to be charged at least at the end of charging and is charged at a constant voltage is determined to the secondary battery to be charged in the charging process It is a charge state detection method for detecting a charge amount and detecting it as a ratio of the detected charge amount to a planned total charge amount,
For the secondary battery to be charged, correction information indicating a correspondence relationship between the applied voltage to the secondary battery and the full charge capacity in the constant voltage charging is obtained in advance,
Detecting a voltage applied to the secondary battery to be charged in the constant voltage charging;
Charge state detection that detects the degree of progress of the charge from the detection information of the applied voltage to the secondary battery and the correction information in a state where the full charge capacity corresponding to the applied voltage becomes the planned total charge amount Method.

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