JPH10304592A - Method and equipment for controlling charging of secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently charge a secondary battery to an actually full charged state by determining the constant voltage charging duration from the charging current at the time of constant-voltage charging and controlling the constant-voltage charging according to the duration. SOLUTION: It this equipment, a microprocessor 10 which is installed in a power management controller 10 reads in current values set in a specified cycle at the time of constant-voltage charging in a registor 12a of a memory 12 and charging current values stored in a specified cycle at the time of constant-voltage charging in a registor of a charging controlling section 15 and compares them. When it determines that the charging current value has become less than the set current value, it drives a driver 17 to put a LED displaying section 16 in a 90% charging rate displayed state and, at the same time, reads in the set time and drives a timer 14 to start a time counting operation. When the time counting operation is finished, the microprocessor 10 puts the LED displaying section 16 in a full charge displayed state and, at the same time, outputs a command to terminate charging to the charging controlling section 15 to finish the charging. By this method, a secondary battery can be efficiently charged and controlled into a truly full charged state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control method and a charge control device for a secondary battery such as a lithium ion battery which performs constant voltage charging after constant current charging.

[0002]

2. Description of the Related Art A rechargeable battery such as a lithium ion battery which requires constant voltage charging control has a larger charging capacity as a constant voltage control voltage (hereinafter, referred to as a control voltage) is higher. I can't do it. Therefore, in order to obtain a sufficient charge capacity, it is necessary to perform charge control at a voltage as high as possible within the overvoltage range.

Conventionally, in charge control of a lithium ion battery, a charge termination process in a constant voltage charge after a constant current charge, as shown in FIG. The charging output has been stopped upon detecting that the charging current has dropped.

However, in the above-described charging control, if a power supply cable of a certain length is interposed between the charging power supply source and the secondary battery, the terminal contact resistance of the secondary battery is further increased. Due to the addition of the resistance, the influence of the voltage drop increases, and the battery does not reach a true full charge state, causing a reduction in the charging rate and causing a problem such as a short operation time of the device.

At this time, the relationship between the charging output and the terminal voltage of the secondary electric field is as shown in FIG. 6, and the effect of the voltage drop is eliminated as the charging termination current approaches zero. When a general AD converter is used as a current detection method for an electronic device, a detection error exists on the order of several tens of mA. Therefore, when charging is terminated within a detectable current range, the influence of a voltage drop cannot be eliminated. This leads to a decrease in charging capacity. In FIG. 6, a indicates the transition from constant current charging to constant voltage charging, and at this time, the terminal voltage of the secondary battery has not reached the set voltage.

As described above, conventionally, when the power supply cable is interposed between the charging power supply source and the terminal of the secondary battery, the influence of the voltage drop increases, causing a reduction in the charging rate and the operation of the device. There was a problem that the time was shortened.

[0007]

As described above, in charging control of a secondary battery requiring constant voltage charging control of a lithium ion battery or the like, conventionally, a charging power supply source and a terminal of the secondary battery are used. When the power supply cable is interposed between
The effect of the voltage drop increases, leading to a decrease in the charging rate,
There has been a problem that the operation time of the device is shortened.

[0008] The present invention has been made in view of the above circumstances,
In charge control of a secondary battery that requires constant voltage charge control such as a lithium ion battery, the charging rate can be greatly improved, and power is supplied between a charging power supply source and a terminal of the secondary battery. A charge control method and a charge control device for a secondary battery which can efficiently control the charge of a secondary battery to a true full charge state by eliminating useless charging time even when the influence of a voltage drop becomes large due to the interposition of a cable or the like. The purpose is to provide.

[0009]

SUMMARY OF THE INVENTION The present invention determines the constant voltage charging time from the charging current at the time of constant voltage charging in the charging control of a secondary battery requiring constant voltage charging control of a lithium ion battery or the like. However, by performing the constant voltage charging control according to the time, even if the power supply cable or the like is interposed between the charging power supply source and the terminal of the secondary battery and the influence of the voltage drop is increased, the useless charging time is reduced. , And the charge of the secondary battery can be efficiently controlled to a true fully charged state.

That is, the present invention relates to a charging control method for a secondary battery requiring constant voltage charging control, wherein a charging current is measured at the time of constant voltage charging, and the measured current value is reduced to a set current value or less. Then, constant-voltage charging is performed continuously from the time to a set time.

Further, the present invention relates to a method of controlling charging of a secondary battery which requires constant voltage charging control, wherein a charging current value is measured at a predetermined timing after the start of constant voltage charging, and charging is performed according to the measured current value. It is characterized in that the time is determined and the constant voltage charging is performed continuously until the time.

Further, the present invention provides a charging control apparatus for a secondary battery which performs constant voltage charging after constant current charging, means for setting a charging current value, and means for holding the set charging current value. Means for setting the charging time, means for holding the set charging time, means for measuring the charging current during constant voltage charging, and comparing the measured charging current value with the set charging current value Means for determining that the measured charging current value is equal to or less than the set charging current value, and that the measured charging current value is equal to or less than the set charging current value. Means for continuously executing constant-voltage charging for the set charging time from the time when the determination is made.

Further, according to the present invention, in a charging control apparatus for a secondary battery which performs constant voltage charging after constant current charging, a table defining a charging current value and a charging time is provided. Means for measuring a charging current, and means for determining a constant voltage charging time with reference to the table based on the measured charging current value, according to the charging current value measured at the beginning of constant voltage charging A constant voltage charging time is determined.

By having the above-described charge control function of the secondary battery, even if a power supply cable or the like is interposed between the charging power supply source and the terminal of the secondary battery, the influence of the voltage drop becomes large. In addition, it is possible to efficiently control the charging of the secondary battery to a true fully charged state while saving unnecessary charging time.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part according to a first embodiment and a second embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes an intelligent power supply provided in a small electronic device such as a portable computer, which uses a secondary battery power source such as a lithium ion battery requiring constant voltage charging control as an operation power source. A power management controller (PMC) that performs power management processing including power control of the entire system and charging control of the secondary battery.

Numerals 11 to 17 are constituent elements of a power management controller (PMC) 10 for realizing an intelligent power supply. Among these components, 11 is a power management controller (P
Microcomputer (μ) serving as a control center of the MC) 10
p) In the first embodiment, the charging current is compared with a set current value (P1) described later during the constant voltage charging, and the charging current is within the set current value (P1). Is determined, a set time (T
An instruction is issued to a charge control unit 15 described later so as to continue the constant voltage charging for only M).

Reference numeral 12 denotes a memory (MEM) used for processing control of the microprocessor (μp) 11. In the first embodiment, the memory (MEM) is compared with the charging current at the time of constant voltage charging, and is set in advance. It has a register 12a for holding a set current value (P1) and a register 12b for holding a preset charging time (TM).

Reference numeral 13 denotes a communication interface (Sys-I / F) for exchanging data with a CPU that controls the entire system, and controls the system control such as turning on / off a system power supply and power supply abnormality. Notify the CPU.

Reference numeral 14 denotes a timer (TIM) for counting a timer under the control of the microprocessor (μp) 11. In the first embodiment, a timer (TIM) 14 controls the register (Rt) under the control of the microprocessor (μp) 11. The timer count is performed according to the charging time (TM) set in ()).

Reference numeral 15 denotes the microprocessor (μp) 1
1 is a charge control unit that controls the supply of charging power to the secondary battery under the control of the control unit 1. In the first embodiment, the charge current at the time of constant voltage charge is controlled according to the instruction of the microprocessor (μp) 11. Becomes smaller than or equal to the set current value (P1), the charging power of the constant voltage is continuously output for a set time (TM) to be described later. A register (R) that can be read by the microprocessor (μp) 11
c), the charging current value at the time of constant voltage charging is set in the register (Rc).

Reference numeral 16 denotes an LED display unit for displaying a charged state and a fully charged state, and 17 denotes a microprocessor (μ).
p) A driver (D) for controlling the drive of the LED display section 16 under the control of 11.

FIG. 2 is a diagram for explaining the charge control operation in the first embodiment of the present invention. When the charge current during constant-voltage charge falls within the set current value (P1), the charge control operation is started. The charging power of the constant voltage is output continuously for the set time (TM) from the time point.

At this time, the set current value (P1) and the set time (TM) indicate various battery characteristics including the battery capacity, battery voltage, charge current curve, etc. of the secondary battery (here, lithium battery) to be charged. From time to time, it is possible to estimate the time to full charge and the change in power at the time of constant voltage charging. Therefore, the optimal set current value (P1) and set time (T
M) can be selected and set in advance. As a result, the charging rate and charging termination of the used secondary battery can be performed at appropriate timing. In the first embodiment, as shown in FIG. 2, a charging rate of 90% is set as a set current value (P1), the charging rate (90%) is displayed at that time, and the setting is performed from the time. When the constant voltage charging for the time (TM) has elapsed, the charging is stopped and the state (full charge state) is displayed.

The operation of the first embodiment of the present invention will now be described with reference to FIGS. By the charge control of the power management controller (PMC) 10,
A secondary battery (lithium ion battery), which is a source of system power supply during battery driving, is subjected to constant current / constant voltage charging control as shown by the charging current characteristics in FIG.

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

Power management controller (PM
C) Microprocessor (μp) 11 provided in 10
In the constant voltage charging, at a predetermined cycle, the set current value (P1) set in the register 12a of the memory (MEM) 12 and the register (Rc) of the charge control unit 15
Then, the charge current value stored in the register (Rc) is read and compared to determine whether or not the charge current value stored in the register (Rc) is within the set current value (P1) set in the register 12a.

Here, the charging current value is equal to the set current value (P1).
When it is determined that the time is within the range, the driver (D) 17 is driven and controlled, and the LED display unit 16 is set to the display state of the charging rate of 90%, and the set time set in the register 12b of the memory (MEM) 12 is set. (TM) is read, 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 according 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 completed, the microprocessor 11 notifies the microprocessor (μp) 11 of the end of the timer count.

When the microprocessor (μp) 11 receives the timer count end notification from the timer (TIM) 14, it controls the driving of the driver (D) 17 to bring the LED display section 16 into the full charge display state and to control the charge control. Part 15
To output a charge end command.

As a result, the charging control section 15 stops supplying the constant voltage charging current to the secondary battery and terminates the charging. When the charging current at the time of constant voltage charging falls within the set current value (P1), a charge control function of continuously outputting the constant voltage charging power for the set time (TM) from that point is provided. Therefore, even if a power supply cable or the like is interposed between the charging power supply source and the terminal of the secondary battery and the influence of the voltage drop increases, the secondary battery can be efficiently and efficiently stored by eliminating unnecessary charging time. Charge control can be performed to a fully charged state.

As a specific numerical example of the first embodiment, the charge current shows a drooping characteristic after the transition to the constant voltage charge control, and the charge rate becomes about 90% at a charge current of 80 mA. . Thereafter, the time required to complete charging can be expected to be about 2 hours based on the charging characteristics.
mA (P1 = 80 mA) and 2 hours (TM =
The timer of 2h) is operated, and charging is terminated after reaching 2 hours. At this time, the LED display unit 16 notifies the user of the full charge state. At this time, constant-current / constant-voltage charging can be achieved in a relatively short time up to a charging rate of about 90%. By displaying the state of charge, usability can be improved.

Next, a second embodiment of the present invention will be described with reference to FIGS. 1, 3 and 4. The second embodiment is significantly different from the above-described first embodiment in that the first embodiment has a constant set time (TM) from the time when the charging current during constant voltage charging becomes within the set current value (P1). In contrast, the second embodiment recognizes the charging current value at the time of constant voltage charging, and sets the constant voltage charging time according to the charging current value. It is characterized by charging control that is determined (that is, the constant voltage charging time is varied according to the charging current value).

In the second embodiment, a charge current value and a charge time are defined as a comparison value with the constant voltage charge current value at the time of constant voltage charge, instead of the register 12a holding the set current value (P1). Charge control table (PT) 1
2c is used.

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

The operation of the first embodiment of the present invention will now be described with reference to FIGS. 1, 3 and 4. FIG. 3 shows a charge control table (P) according to the second embodiment of the present invention.
FIG. 4 is a diagram for explaining the configuration of T), and FIG. 4 is a diagram for explaining a charge control operation in the embodiment.

The power management controller (PM
C) By the charge control of 10, the secondary battery (lithium ion battery), which is the source of the system power supply during battery operation, is subjected to constant current / constant voltage charge control as shown by the charge current characteristic in FIG.

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

Power management controller (PM
C) Microprocessor (μp) 11 provided in 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 stores the charge current value in the charge control table (PT) in the memory (MEM) 12. ) It determines which of the charging current ranges immediately after the start of the constant voltage charging defined in 12c, and sets a timer set value indicating the constant voltage charging time defined in the corresponding charging current range to a timer (TIM). The timer (TIM) 14 is set in the register (Rt) 14 and the timer (TIM) 14 is started.

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

Thus, the timer (TIM) 14 starts a timer counting operation according to the charging time (TM) set in the register (Rt). Then, when the timer count operation according to the charging time set in the register (Rt) is completed, 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, it controls the driving of the driver (D) 17 to bring the LED display section 16 into the full charge display state and to control the charge control. Part 15
To output a charge end command.

As a result, the charging control unit 15 stops supplying the constant voltage charging current to the secondary battery and terminates charging. By using such a charge control table (PT) 12c to provide a charge control function of outputting constant-voltage charge power for a set time according to a charge current at the start of constant-voltage charge, a charge power supply source and a secondary Even if a power supply cable or the like is interposed between the terminal of the battery and the influence of the voltage drop becomes large, it is possible to efficiently charge the secondary battery to a true fully charged state by eliminating unnecessary charging time. Further, for example, when the secondary battery is replaced, it is possible to perform optimal charging that matches the state of charge (charging rate) of the replaced secondary battery.

In the second embodiment, the charging current range immediately after the start of the constant voltage charging defined in the charging control table (PT) 12c is divided into three levels of P1 to P2, P2 to P3, and P3 or less. When the current is in the range of P1 to P2, the timer set value indicating the constant voltage charging time is set to 1.5h
(90 minutes), and 1 when it is in the range of P2 to P3
h (60 minutes), 0.5h (30
However, the present invention is not limited to this, and it is possible to control the charging time more finely by setting it to four or more levels.

[0045]

As described above in detail, according to the present invention, in charging control of a secondary battery which requires constant voltage charging control of a lithium ion battery or the like, the charging current at the time of constant voltage charging is changed to a constant voltage. By determining the charging time and performing constant voltage charging control in accordance with the time, even if a power supply cable or the like is interposed between the charging power supply source and the terminal of the secondary battery, the influence of the voltage drop increases, It is possible to efficiently control the charging of the secondary battery to a true fully charged state while saving unnecessary charging time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part according to an embodiment of the present invention.

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

FIG. 3 is a diagram illustrating a configuration of a charge control table (PT) according to a second embodiment of the present invention.

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

FIG. 5 is a diagram showing charging characteristics of a lithium ion battery.

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

[Explanation of symbols]

 Reference Signs List 10: Power management controller (PMC), 11: Microprocessor (μp), 12: Memory (MEM), 12a: Register for holding set current value (P1), 12b: Register for holding set time (TM), 12c ... Charge control table (PT), 13 ... Communication interface (Sys-I / F), 14 ... Timer (TIM), 15 ... Charge control unit, 16 ... LED display unit, 17 ... Driver (D).

Claims (7)

[Claims] In a charge control method for a secondary battery that requires constant voltage charge control, a charge current is measured during constant voltage charge, and when the measured current value falls below a set current value, A charge control method for a secondary battery, comprising: performing constant-voltage charging continuously from the time to a set time. 2. A charge control method for a secondary battery requiring constant voltage charge control, wherein a charge current value is measured at a predetermined timing after the start of constant voltage charge, and a charge time is determined according to the measured current value. And a method of controlling the charging of the secondary battery, wherein the constant voltage charging is continuously performed until the time. 3. The charging control method for a secondary battery according to claim 1, wherein a charging current at the time of constant voltage charging is measured on a charging power supply side. 4. A charge control device for a secondary battery which performs constant voltage charge after constant current charge, comprising: means for setting a charge current value; means for holding the set charge current value; Means for setting, means for holding the set charging time, means for measuring the charging current during constant voltage charging, comparing the measured charging current value with the set charging current value, Means for determining that the measured charging current value is equal to or less than the set charging current value, and when determining that the measured charging current value is equal to or less than the set charging current value, Means for continuously performing constant-voltage charging for the set charging time from the time point. 5. A charge control device for a secondary battery that performs constant voltage charge after constant current charge, comprising: a table defining a charge current value and a charge time; and measuring the charge current at the beginning of constant voltage charge. Means for determining a constant voltage charging time by referring to the table based on the measured charging current value, and a constant voltage charging time according to the charging current value measured at the beginning of the constant voltage charging. A charge control device for a secondary battery, characterized in that: 6. The charge control device for a secondary battery according to claim 4, further comprising display means for displaying at least a constant voltage charge state or a full charge state. 7. The charging control device for a secondary battery according to claim 4, wherein a current value of the constant voltage charging is measured on a charging power supply side.