KR100304987B1 - Method and apparatus for controlling charging of a secondary battery - Google Patents

Abstract

In an electronic device for carrying out constant voltage charging, a voltage drop caused by a resistance component such as a cable interposed between a charging power supply source and a secondary battery such as a lithium ion battery that requires charging is eliminated, thereby filling the secondary battery. 2, in which the charging current value is measured at the time of constant voltage charging in order to control the charging to the whole state, and after detecting that the measured charging current value has dropped to a predetermined current value, the constant voltage charging is continued for a predetermined time and ends the constant voltage charging. Method and apparatus for controlling charge of a secondary battery.

Description

TECHNICAL AND APPARATUS FOR CONTROLLING CHARGING OF A SECONDARY BATTERY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging control method and apparatus for a secondary battery used for a power source of an electronic device such as a portable computer, and more particularly, to a charging control method and apparatus for a secondary battery requiring constant voltage charging after constant current charging.

Electronic devices, such as portable notebook-type personal computers, are equipped with a rechargeable secondary battery as a power source for driving the device even when a commercial power source cannot be used.

There exists a lithium battery in the secondary battery as such an electronic device battery drive power supply, for example. Secondary batteries, such as this lithium battery, need to be controlled to perform constant voltage charging. In constant voltage charging, the higher the charge control voltage, the greater the charge capacity of the battery. However, if the charging voltage is made too high, there is a risk that the battery is heated. Therefore, for safety measures, charging at overvoltage is not performed. Therefore, the charging control of the secondary battery should be controlled to charge at the highest possible voltage within a range not overvoltage to obtain a sufficient charging capacity.

2. Description of the Related Art Conventionally, secondary batteries execute constant voltage charging control after constant current charging as shown in the charging characteristic diagram of FIG. In other words, the charging control is terminated by stopping the supply of the voltage from the charging voltage supply source at the time when it is detected that the charging current has dropped to the specified current value after the constant current charging for a certain period of time.

However, in the case of carrying out such constant voltage charge control, there is a resistance component depending on the length of the power supply cable itself connecting the charge voltage supply source and the secondary battery in addition to the terminal contact resistance with the secondary battery. Thus, there is a problem that the charging voltage drops. Under the influence of this voltage drop, before the secondary battery becomes a true full charge state, the specified charging current value is detected and the charge termination process is performed. That is, since the termination process of the constant voltage charging is performed before the secondary battery is fully charged, a problem arises in that the charging rate of the battery is lowered, and as a result, the operation time for driving the battery of the electronic device is shortened.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and in the charge control of a secondary battery requiring constant voltage charging, the voltage drop due to the resistance component by the length of the power supply cable itself connecting between the charge voltage source and the secondary battery itself. It is an object of the present invention to provide a method and apparatus for controlling charging of a secondary battery, which can solve the problem, and can charge the secondary battery in a state close to full charge.

In addition, an object of the present invention is to provide a charging control method and apparatus for a secondary battery that can be efficiently charged in a fully charged state by eliminating unnecessary charging time.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the structure of the principal part which concerns on embodiment of this invention.

2 is a diagram for explaining a charge control operation in the first embodiment of the present invention.

3 is an explanatory diagram of a configuration of a charge control table PT according to a second embodiment of the present invention.

4 is a diagram for explaining a charge control operation in a second embodiment of the present invention.

5 shows charging characteristics of a lithium ion battery.

6 is a diagram showing a correlation between a charge output and a battery terminal voltage for explaining a conventional charge control.

<Explanation of symbols for main parts of drawing>

10: Power Management Controller (PMC)

11: microprocessor

12: memory

13: Communication Interface (Sys-I / F)

14: Timer (TIM)

15: charge control unit

16: LED indicator

17: Driver (D)

In the charge control of a secondary battery that requires constant voltage charge control, the present invention determines the constant voltage charge time from the charge current at the time of constant voltage charge and performs constant voltage charge control. Thereby, even if there is a voltage drop by the resistance component of the power cable between the charging power supply source and the secondary battery terminal, the secondary battery can be efficiently charged and controlled in the state of being charged.

That is, according to the present invention, in the charging control of a secondary battery requiring constant voltage charging control, the charging current at the time of constant voltage charging is measured, and the constant voltage charging is continued from the time point when the measured current value reaches a preset predetermined current value. It is characterized in that the execution.

In this case, the relationship between the charge output and the terminal voltage of the secondary battery is as shown in Fig. 6, and the influence of the voltage drop caused by the cable can be eliminated by bringing the charging end current close to zero. Accordingly, the present invention is characterized by continuing the constant voltage charging so that the charging end current is as close as possible to zero.

In addition, a general AD converter is used as a current detection method of an electronic device.

FIG. 6 shows a state in which the terminal voltage of the secondary battery does not reach the set voltage at the time point a when the transition from the constant current charging to the constant voltage charging is performed.

In addition, the present invention provides a charge control method for a secondary battery that requires constant voltage charge control, wherein the charge current value is measured at a predetermined timing after the start of constant voltage charge, the charge time is determined according to the measured current value, and the constant voltage is maintained until the time. It is characterized by continuing to charge.

In addition, the present invention provides a charging control apparatus for a secondary battery that performs constant voltage charging after constant current charging, comprising: means for setting a charge current value, means for maintaining a set charge current value, means for setting a charge time, and set charge Means for maintaining time, means for measuring the charge current during constant voltage charging, and means for comparing the measured charge current value with the set charge current value to determine that the measured charge current value is equal to or less than the set charge current value. And means for continuously executing constant voltage charging for the set charging time from that time point when it is determined that the measured charge current value is equal to or less than the set charging current value.

In addition, the present invention provides a charge control apparatus for a secondary battery that performs constant voltage charging after constant current charging, comprising: a table defining a charge current value and a charging time, means for measuring the charge current at the beginning of constant voltage charging, and the measurement. And a means for determining the constant voltage charging time with reference to the table based on the set charging current value, wherein the constant voltage charging time is determined according to the charging current value measured at the beginning of the constant voltage charging.

By having the charge control function of the secondary battery as described above, even if the effect of the voltage drop becomes large through the power supply cable or the like between the charging power supply source and the terminal of the secondary battery, the unnecessary charge time is eliminated efficiently. Charge control of the secondary battery in a full charge state.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

FIG. 1 is a block diagram showing the configuration of a Power Management Controller (PMC) 10 that performs charge control of a secondary battery according to the present invention.

This PMC 10 uses the secondary battery power supply as an operation power supply. For example, an intelligent power supply provided in a small electronic device such as a portable computer is realized, and is responsible for power management processing including power supply control of the entire system and charge control of the secondary battery.

As a component of the power management controller (PMC) 10 for realizing an intelligent power supply, there is a microprocessor 11 which forms a control center. The microprocessor 11 compares the charging current with the setting current value P1 described later during constant voltage charging, and determines that the charging current has reached the setting current value. Instructions are provided to the charging control unit 15 to be described later.

The memory 12 is used for process control of the microprocessor 11. This memory has a register 12a for holding a preset set current value P1 compared with the charging current during constant voltage charging and a register 12b for holding a preset charging time TM. The memory also has a charge control table (PT) 12c described in the second embodiment.

The communication interface (Sys-I / F) 13 is for exchanging data with the microprocessor 11 that is in charge of controlling the entire system. Notify the microprocessor in charge of system control.

The timer TIM 14 executes a timer count under the control of the microprocessor 11, and executes a timer count according to the charging time set in the register Rt 141 under the control of the microprocessor 11.

The charging control unit 15 controls the supply of charging power to the secondary battery under the control of the microprocessor 11, and the charging current at the time of constant voltage charging is instructed by the microprocessor 11 to register 12a. When it is within the set current value P1, the charging power of the constant voltage is continuously output from the time point for a predetermined set time TM. In addition, the microprocessor 11 has a register Rc which can be read, and sets the charging current value at the time of constant voltage charging to the register Rc.

The LED display unit 16 displays the state of charge and the state of full charge, and the driver (D) 17 controls the driving of the LED display unit 16 under the control of the microprocessor 11.

It is a figure for demonstrating the charge control operation in 1st Embodiment of this invention. When the charging current at the time of constant voltage charging is within the set current value P1, the charging power of a constant voltage is output continuously from that time point for the set time TM.

At this time, the set current value P1 and the set time TM are determined at the time of constant voltage charging from various battery characteristics including the battery capacity, the battery voltage, the charging current curve, and the like of the secondary battery (for example, a lithium battery) to be charged. It is possible to estimate the time until the full charge and the change in power, and therefore, it is possible to select and set in advance the set current value P1 and the set time TM that are optimal for the secondary battery to be charged. This makes it possible to control the charge rate of the secondary battery and stop charging at an accurate timing. In this first embodiment, as shown in Fig. 2, the charging rate (90%) is displayed at that time by setting the charging rate 90% as the set current value P1, and for a predetermined set time TM from the time point. Charging is stopped when the constant voltage charging has elapsed, and the state (full charge state) is displayed.

Herein, the operation in the first embodiment of the present invention will be described with reference to FIG. 1 and FIG. 2.

The secondary battery (lithium ion battery), which is a source of system power when the battery is driven by the charge control of the power management controller (PMC) 10, is charged with constant current and constant voltage as shown in FIG. Controlled.

Here, the charging control unit 15 provided in the power management controller (PMC) 10 holds the current value in the register R as update data that changes with the charging time during constant voltage charging.

The microprocessor 11 installed in the power management controller (PMC) 10 has a set current value P1 set in the register 12a of the memory MEM 12 at a predetermined period during the constant voltage charging, and the charging. The charging current value stored in the register Rc 151 of the control unit 15 is read and compared to determine whether the charging current value stored in the register Rc is within the set current value P1 set in the register 12a.

Here, when it is determined that the charging current value is within the set current value P1, the driver D 17 is driven to control the LED display unit 16 to a display state of 90% of the charge rate, and at the same time the memory MEM ( The set time TM set in the register 12b of 12) is read out, set in the register Rt 141 of the timer 14, and the timer 14 is started.

As a result, the timer 14 starts a timer counting operation corresponding to the charging time TM set in the register Rt. When the timer count operation according to the charging time TM set in the register Rt is terminated, the microprocessor 11 is notified of the end of the timer count.

When the microprocessor 11 receives the timer count end notification from the timer 14, the microprocessor 11 drives the driver (D) 17 to drive the LED display unit 16 to the full charge display state and simultaneously charges the charging control unit 15. Output the command to end.

As a result, the charging control unit 15 stops the supply of the constant voltage charging current to the secondary battery and ends the charging.

In this manner, when the charging current at the time of constant voltage charging is within the set current value P1, the charging power supply source and the charging control function for outputting the charging power of the constant voltage continuously for the set time TM from that point of time are provided. Even if a power supply cable or the like is interposed between the terminals of the secondary battery, even if the effect of the voltage drop becomes large, unnecessary charge time can be eliminated and the secondary battery can be efficiently charged and controlled in a true full charge state.

If the specific numerical example of said 1st Embodiment is shown, after switching to constant voltage charge control, a charge current will show a vertical fall characteristic, and will become a charge rate of about 90% at 80 mA of charge current. After that, the time required to complete the charging can be estimated to be about 2 hours from the charging characteristic, so that the timer for 2 hours (TM = 2h) is operated at the same time as detecting the charging current of 80 mA (P1 = 80 mA), reaching 2 hours. After that, charging is terminated. At that time, the LED display unit 16 notifies the user of the full charge state. At this time, the constant current / constant voltage charging can be reached at a relatively fast time until the charging rate is about 90%, but since the charging speed tends to be slow after that, the charging status display is executed at the time of reaching 90% (80 mA detection time). The convenience of use can be improved by doing.

Next, with reference to FIG. 1, FIG. 3, and FIG. 4, 2nd Embodiment of this invention is described.

The second embodiment differs greatly from the first embodiment described above in that the first embodiment continues the constant voltage for a predetermined set time TM from the time when the charging current at the time of constant voltage charging is within the set current value P1. In contrast to the charging control for outputting the charging power, in the second embodiment, the charging current value is recognized at the time of constant voltage charging, and the constant voltage charging time is determined according to the charging current value (that is, the constant voltage charging time is set in accordance with the charging current value). Change) charge control.

In the second embodiment, the charge control table PT 12c which defines the charge current value and the charge time instead of the register 12a holding the set current value P1 as a comparison value with the constant voltage charge current value at the time of constant voltage charging. ) Is used.

The relationship between the charge current value immediately after the constant voltage charge start and the charge time defined by this charge control table (PT) 12c is, for example, the charge immediately after the constant voltage charge start as shown in FIGS. 3 and 4 in this embodiment. The current level is divided into three levels of P1 to P2, P2 to P3, and P3 or less, and when the charging current is within the range of P1 to P2, the timer setting indicating the constant voltage charging time is 1.5h (90 minutes), and the P2 to P3 It is 1h (60 minutes) when it is in a range, and 0.5h (30 minutes) when it is P3 or less.

Here, with reference to FIG. 1, FIG. 3, and FIG. 4, operation | movement in 2nd Embodiment of this invention is demonstrated. FIG. 3 is a diagram for explaining the configuration of the charge control table PT in the second embodiment of the present invention, and FIG. 4 is a diagram for explaining the charge control operation in the second embodiment.

By the charge control of the power management controller (PMC) 10, the secondary battery (lithium ion battery) serving as a source of system power when the battery is driven is shown in FIG. 4 as a constant current and constant voltage charge control. do.

Here, the charging control unit 15 provided in the power management controller (PMC) 10 holds in the register (Rc) 151, as update data, a current value that changes with the charging time during constant voltage charging.

The microprocessor (p) 11 installed in the power management controller (PMC) 10 reads the charge current value stored in the register Rc of the charge control unit 15 at the start of the constant voltage charge, and charges the charge. It is determined whether the current value is within the charge current range immediately after the start of the constant voltage charge defined in the charge control table PT 12c of the memory MEM 12, and the constant voltage charge defined in the corresponding charge current range is determined. The timer setting value indicating the time is set in the register Rt of the timer (TIM) 14, and the timer (TIM) 14 is started.

For example, when the charging current immediately after the start of constant voltage charging is within the range of P1 to P2, the timer setting value indicating the constant voltage charging time is 1.5h (90 minutes), and when it is within the range of P2 to P3, 1h (60 minutes). When P3 or less, 0.5h (30 minutes), the corresponding timer setpoint is set in the register Rt of the timer TIM 14, and the timer TIM 14 is started.

As a result, the timer TIM 14 starts a timer counting operation corresponding to the charging time TM set in the register Rt. When the timer count operation according to the charging time set in the register Rt ends, the microprocessor (μp) 11 is notified of the end of the timer count.

When the microprocessor (μp) 11 receives the timer count end notification from the timer (TIM) 14, the microprocessor (μp) 11 drives the driver (D) 17 to control the drive, thereby bringing the LED display unit 16 into a charge completion display state. The charging command 15 outputs an instruction to end the charging.

As a result, the charging control unit 15 terminates the supply of the constant voltage charging current to the secondary battery and ends the charging.

In this way, the charging control table (PT) 12c is used to provide a charging control function for outputting the charging power of the constant voltage for a predetermined time according to the charging current at the start of the constant voltage charging. A power supply cable or the like is interposed between the terminals so that the secondary battery can be efficiently charged and fully charged with high efficiency by eliminating unnecessary charging time even when the voltage drop is greatly affected. In addition, for example, when the secondary battery is replaced, optimum charging in accordance with the state of charge (charge rate) of the replaced secondary battery becomes possible.

Moreover, in 2nd Embodiment mentioned above, the charge current range immediately after the constant voltage charge start defined in the charge control table (PT) 12c is divided into three levels of P1-P2, P2-P3, P3 or less, and charge current is P1-- The timer setting value for the constant voltage charging time is within 1.5h (90 minutes) when within the range of P2, 1h (60 minutes) when within the range of P2 to P3, and 0.5h (30 minutes) when below P3. It is not limited to this, It is also possible to carry out more fine charge time control to four levels or more.

As described above, according to the present invention, in the charge control of a secondary battery that requires constant voltage charge control such as a lithium ion battery, the constant voltage charge time is determined from the charge current at the time of constant voltage charge, By carrying out the constant voltage charging control, the power supply cable is interposed between the charging power supply source and the terminal of the secondary battery to eliminate the unnecessary charging time even if the effect of the voltage drop becomes large. It is possible.

Claims (8)

In the charge control method of a secondary battery that requires constant voltage charging, Measuring a charge current value during constant voltage charging; Detecting that the measured charging current value falls to a predetermined current value previously stored in a memory; And when the prescribed current value is detected, terminating the constant voltage charging after continuing the constant voltage charging for the predetermined time based on a predetermined time previously stored in a memory. The method of claim 1, wherein the terminating of the constant voltage charging is performed when the charging current value approaches zero. In the charge control method of a secondary battery that requires constant voltage charging, Measuring a charge current value during constant voltage charging; Detecting that the measured charging current value falls to a predetermined current value previously stored in a memory; Notifying the state of charge when the prescribed current value is detected; If the prescribed current value is detected, terminating the constant voltage charging after continuing the constant voltage charging for the predetermined time based on a predetermined time previously stored in a memory; And notifying the end of charging when the constant voltage charging is terminated. In the charge control device of a secondary battery that requires constant voltage charging, Means for measuring a charge current value during constant voltage charging; Means for detecting that the measured charge current value has dropped to a prescribed current value previously stored in a memory; And a means for terminating said constant voltage charging after continuing said constant voltage charging for said predetermined time based on a predetermined time previously stored in a memory when said prescribed current value is detected. . The charge control device for a secondary battery according to claim 4, wherein said constant voltage charge terminating means is executed when said charge current value approaches zero. In the charge control device of a secondary battery that requires constant voltage charging, Means for measuring a charge current value during constant voltage charging; Means for detecting that the measured charge current value has dropped to a prescribed current value previously stored in a memory; Means for notifying the state of charge when the specified current value is detected; Means for terminating the constant voltage charging after continuing the constant voltage charging for the predetermined time based on the predetermined time stored in advance in the memory when the prescribed current value is detected; And a means for notifying termination of charge when the constant voltage charge is terminated. In the power supply control apparatus for electronic equipment which operates with the power supply from the secondary battery which requires constant voltage charge, A processor which executes overall processing of power supply control and charge control of the secondary battery; A memory for storing a prescribed charging current value to be detected and a set appropriate charging time, respectively; A charging control unit supplying charging power to the secondary battery; And a timer for measuring the constant voltage charging time, After starting the constant voltage charge of the secondary battery according to the instruction of the processor, the measured charge current is compared with the specified charge current value stored in the memory, and then stored in the memory after detecting that the charge current reaches the specified charge current value. Charge control device for a secondary battery characterized in that the constant voltage charging is continued for a suitable time. 8. The apparatus of claim 7, wherein the memory further includes a table defining charge current values and charge times, And the processor determines a constant voltage charge time with reference to the table based on the measured charge current value.