JP3492903B2 - Lithium ion secondary battery charging system and charger - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging system and a charger for a lithium ion battery used in a lithium ion battery pack having a built-in protection circuit in a portable device such as a portable wireless device.

[0002]

2. Description of the Related Art In recent years, as a power source for portable devices, which have been rapidly reduced in size and weight, small and lightweight lithium ion secondary batteries with high energy density have been actively developed and widely used. .

FIG. 4 shows an example of the structure of a conventional lithium ion secondary battery pack, where P is the lithium ion 2
The lithium-ion secondary battery pack P is a secondary battery pack, and the lithium-ion secondary battery pack P includes a positive terminal A, a negative terminal B, a battery cell body 1 including a pair of battery cells 1a and 1b, and a battery cell 1.
The protection circuit 2 for preventing performance deterioration and destruction of a and 1b is provided.

Since the lithium ion secondary battery has a high energy density and is made of a highly ignitable material, it is ruptured or ignited when over-discharge, over-voltage charging, terminal short circuit or the like occurs. May cause significant performance degradation. In order to prevent these occurrences, the protection circuit 2
This protection circuit 2 generally detects a protection switch 2a connected in series between the negative electrode of the battery cell body 1 and the negative terminal B and an overdischarge / overvoltage charge or a terminal short circuit. Control I for turning off the protection switch 2a
It is composed of C2b.

[0005] Incidentally, the lithium ion secondary battery pack P shown in FIG. 4 is a case of two cells in series connected pair of battery cells 1a, 1 b in series, other combinations,
For example, in the case of only one cell or three cells, the connection method and function are the same, so the case of two columns in series will be described as a representative.

As a charging method for the lithium-ion secondary battery pack P having the above-described structure, constant-current constant-voltage charging of 4.1 V or 4.2 V per cell is performed, and the charging is stopped when the charging current decreases to a specified charging current. The method is generally used.

As an example of a circuit block for realizing such a charging system, the one shown in FIG. 5 is known. According to this, the power supply unit 3 for supplying power, the current detection resistor 7,
The base voltage of the output control transistor 6 is controlled from the charging current detected from the voltage drop of the backflow prevention diode 5, the output control transistor 6, and the current detection resistor 7 and the voltage between the terminals A and B of the battery pack P to obtain a constant current. The charging control unit 4 that performs constant voltage charging is included in the configuration.

The charge control unit 4 has a structure in which a comparator and a transistor are combined, and the like. Recently, an IC in which these are combined has been developed and used.

The battery pack P comprises a battery cell 1 and a protection circuit 2. Here, the protection circuit 2
As described above with reference to FIG. 4, it is composed of the control IC 2b and the protection switch 2a having the on-resistance Rx, but since the control IC has high impedance, the influence on charging can be ignored. Therefore, the protection circuit 2 can be regarded as the resistor Rx connected in series to the battery cell 1.

[0010]

However, the conventional lithium-ion secondary battery pack P charging system shown in FIG. 5 has the following problems.

That is, FIG. 6 shows the charging characteristics when the discharged lithium-ion secondary battery is charged by the charging method of the lithium-ion secondary battery pack P shown in FIG. Since the output control is performed so that the terminal AB of the battery pack P becomes the specified charging voltage, the constant current period ends at time T1, and the resistance component of the protection circuit 2 is divided during the constant voltage period thereafter. Due to the voltage drop due to Rx, the specified charging voltage is not applied to the battery cell body 1,
It was reducing the charging efficiency.

By correcting the loss due to the resistance component in series with the battery cell body 1 and increasing the charging voltage,
Japanese Patent Application Laid-Open No. 7-
Known in Japanese Patent Application Laid-Open No. 107677 and Japanese Patent Application Laid-Open No. 9-129270, in these methods, a voltage drop equivalent to the resistance component Rx of the protection circuit 2 such as a resistor or a diode is added to the configuration shown in FIG. Therefore, it is necessary to add an element for obtaining the voltage and a circuit for controlling the output of the charging voltage to the charging control unit 4 so as to increase the charging voltage by the voltage drop.

Further, in the case of a charger to which an unspecified number of battery packs are connected, in the above conventional charging system, the battery back P
Rx of battery back P cannot be dealt with due to variations in Rx of each battery.
Is larger, the effect of correction is smaller, and in the worst case,
There is a problem that the rated charging capacity cannot be obtained because the specified charging voltage cannot be applied. Further, when the Rx of the battery pack P is small, a charging voltage exceeding the specified charging voltage value is applied to the battery cell 1, and there is a risk of deterioration of battery performance such as cycle life or destruction.

Further, in the above-mentioned conventional charging system,
There are other problems as follows. That is, normally, when charging a lithium ion secondary battery, the voltage is checked before starting charging, and when the battery cell voltage of the battery cell 1 is lower than a specified value, for protection and safety of the lithium ion battery charger. Then, the battery was slowly charged with a small current, and after the voltage of the battery cell 1 increased to a specified value, the current was increased to start the rapid charging.

Also, lithium-ion 2 that has been overvoltage-charged
When the next battery is connected, it is determined that the battery is abnormal, charging is not performed, and the user is notified by some means.

However, in a battery pack P having a built-in protection circuit 2 such as a lithium ion secondary battery, in both cases of low voltage and high voltage as described above,
The protection circuit 2 may be in an open state, and in the configuration as shown in FIG. 5, the charging control unit 4 cannot detect the battery cell voltage, and current control at low voltage and abnormalities at high voltage. There was a problem that the display could not be controlled.

In addition, conventional nicad batteries, lead acid batteries, etc.
Te battery pack smell no protection circuit 2, the battery cell voltage during charging can be estimated charge capacity, the battery pack P incorporating the protection circuit 2, such as a lithium ion secondary battery, the protection circuit the voltage drop in the 2, because it can not detect the correct cell voltages, accuracy is a problem called it is impossible to detect a high charge capacity.

In order to solve the above-mentioned problems of the prior art, the present invention achieves high performance by controlling charging with an accurate voltage of the battery cell body without being affected by variations in the protection circuit for each battery pack. It is an object of the present invention to provide a lithium-ion secondary battery charging system and a charger that can perform charging with efficiency and minimize deterioration of battery performance, and that also realizes highly accurate charge capacity detection.

[0019]

To achieve the above object, according to the Invention The power supply present invention detects negative electrode potential of the battery cell by cell the negative electrode potential detecting terminals provided in the battery pack, and for outputting a direct current Part, a current detection resistor that detects a charging current, a cell voltage detection circuit that outputs the voltage of the battery cells of the battery pack, and a constant current charge is performed at a specified charging voltage or less, and the specified charging voltage is reached. After that, a charging circuit configured to have a charging control unit that controls to perform constant-voltage charging with a specified voltage , which is the negative electrode side of the battery cell.
Directly connect one end of the protection resistor to
By connecting directly the negative electrode potential detecting terminal of the other end, in which to perform the charging control by the voltage of the batteries cells.

According to the present invention, since the cell voltage can be accurately monitored without being affected by the variation of the protection circuit, the constant current constant voltage for applying the specified charging voltage to the battery cell regardless of the voltage drop due to the protection circuit. Charge control becomes possible.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 has a construction in which a battery pack has a built-in protection circuit for preventing performance deterioration and destruction of battery cells, and a resistance component is connected in series with the battery cells. a lithium ion secondary battery charging method having the negative electrode potential of the battery cell provided on batteries pack Thus detects the battery cell anode potential measuring terminals, and a power supply unit that outputs a direct current, the charging current a current detection resistor for detecting the cell voltage detection circuit for outputting a voltage of the battery cell of batteries pack, a constant current charging in the following charge voltage prescribed, after reaching the charging voltage of the provisions, specified voltage The charging circuit is configured to have a charging control unit that controls so as to perform constant voltage charging, and the protection resistor is provided on the negative electrode side of the battery cell.
Connect one end directly and connect the other end of the protective resistor directly to the negative
Connect the electrode potential detection pin, characterized in that it is configured to control charging of the charging controller by the voltage of the battery cell
It

In a second aspect of the present invention, the charge control section according to the first aspect checks the voltage of the battery cell before starting charging, and if the voltage is less than a specified voltage, charges the battery with a small current to obtain a specified voltage. The lithium-ion secondary battery charging method is characterized in that control is performed so as to start rapid charging after rising.

According to a third aspect of the present invention, the charge control section according to the second aspect confirms the voltage of the battery cell before starting charging, and if the voltage is equal to or higher than the specified voltage, determines that the battery is abnormal, It is a lithium-ion secondary battery charging method characterized in that the battery is controlled so as not to be charged and the battery abnormality is displayed at the same time.

The present invention according to claim 4 is characterized in that the charging control unit according to claim 3 detects the charge capacity of the battery cell by monitoring the voltage of the battery cell during charging. It is an ion secondary battery charging system.

[0025] The invention according to claim 5, a built-in protection circuit to prevent performance deterioration or destruction of the battery cells in the battery pack, batteries cell and the lithium-ion 2 series resistance component is constituted by connecting a next battery charger, and the battery cell anode potential detection terminal for detecting the negative electrode potential of the batteries cells arranged in batteries pack, a power supply unit that outputs a direct current, a current detection resistor for detecting the charging current, a cell voltage detecting circuit which outputs a voltage of the battery cell of batteries pack, a constant current charging in the following charge voltage prescribed, after reaching the charging voltage of the provision, to perform constant voltage charging under the provisions of the voltage controlled to constitute a charging control unit, further, the negative electrode of the battery cell
Connect one end of the protection resistor directly to the
Directly connecting the negative electrode potential detection terminal to the other end of the anti, and is characterized in that the charging control by the voltage of the batteries cells.

According to a sixth aspect of the present invention, the charge control section according to the fifth aspect confirms the voltage of the battery cell before starting charging, and if the voltage is equal to or lower than the specified voltage, the battery is charged with a small current and the specified voltage The lithium-ion secondary battery charger is characterized in that it is controlled so as to start rapid charging after rising.

According to a seventh aspect of the present invention, the charge control section according to the sixth aspect confirms the voltage of the battery cell before starting charging and determines that the battery is abnormal if the voltage is equal to or higher than a specified voltage. It is a lithium-ion secondary battery charger characterized in that it controls so as not to charge the battery and simultaneously displays a battery abnormality.

The present invention according to claim 8 is characterized in that the charging control unit according to claim 7 detects the charge capacity of the battery cell by monitoring the voltage of the battery cell during charging. It is an ion secondary battery charger.

As a result, since the cell voltage can be accurately monitored without being affected by the variation of the protection circuit, the constant-current constant-voltage charging control for applying the specified charging voltage to the battery cell can be performed regardless of the voltage drop due to the protection circuit. It will be possible.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit block configuration of a lithium ion secondary battery charging system according to the first embodiment of the present invention, and the same functional parts as those of the conventional system shown in FIG. 5 are designated by the same reference numerals. .

That is, P is a battery pack, which includes a battery cell 1, a protection circuit 2, a battery protection resistor 11, a positive terminal A, a negative terminal B, a negative electrode C of the battery cell 1, and a battery cell 1.
Constitute a negative electrode potential measuring terminals S of the battery cell
One end of the battery protection resistor 11 is directly connected to the negative electrode C side of rule 1.
In addition, the negative electrode potential is directly applied to the other end of the battery protection resistor 11.
The detection terminal S is connected .

Further, D is a charging circuit, which includes a power supply unit 3, a backflow prevention diode 5, and cell voltage detection resistors 8, 9, and 1.
It has 0 and 12, and the charge control part 4 and is comprised.

The cell voltage detecting resistors 9 and 12 divide the voltage between the positive terminal A and the negative terminal B of the battery pack P, and the non-inverting input terminal of the operational amplifier 13 is connected to the voltage dividing point. .

The cell voltage detecting resistors 8 and 10 are connected in series between the output terminal of the operational amplifier 13 and the negative electrode potential detecting terminal S of the battery pack P, and the cell voltage detecting resistors 8 and 10 are connected in series. The inverting input terminal of the operational amplifier 13 is connected to the connection point.

The charge control section 4 is connected to both ends of the current detection resistor 7, the output terminal of the operational amplifier 13 and the base of the output control transistor 6.

Next, the charging operation in the first embodiment will be described. Cell voltage detection resistors 8, 9, 10 and 12
, And the battery protection resistor 11 and the operational amplifier 13 form a cell voltage detection circuit by forming a differential amplifier circuit. If each resistance value is adjusted and the amplification factor is set to 1, the output of the operational amplifier 13 will be It is a voltage between the positive terminal A and the negative electrode C which is the cell voltage.

Therefore, the charging control unit 4 determines that the battery cell 1
The charging output can be controlled in accordance with the voltage drop in the protection circuit 2 so that the specified charging voltage is applied to, and efficient constant-current constant-voltage charging becomes possible.

FIG. 2 shows the charging characteristics when the battery pack P of the discharged lithium-ion secondary battery is charged in the circuit block configuration of the lithium-ion secondary battery charging system shown in FIG.

According to the lithium ion secondary battery charging system having the circuit block configuration shown in FIG. 1, constant current charging is performed until the battery cell 1 reaches a specified charging voltage, and during the constant voltage charging period, the battery cell is 1, the specified charging voltage is applied, and the battery pack P terminal plus terminal A and minus terminal B
In between, the voltage drop in the protection circuit 2 is applied and the charging voltage corrected in accordance with the decrease in the charging current is applied.

Further, FIG. 3 shows the charging characteristics of the charging system according to the first embodiment in comparison with the conventional system. According to FIG. 3, in the charging method according to the first embodiment, the battery cell 1 is accurately subjected to the constant current / constant voltage at the specified charging voltage. It has been extended to T2,
The charging capacity will also increase.

Next, a charging method according to the second embodiment of the present invention will be described with reference to FIG.

The charging method of the second embodiment, the charging control unit 4 in FIG. 1, if the cell voltage is lower than the specified value slowly was charged with a small current, after increasing the cell voltage reaches the specified value, quick charge This is a charging method in which the function of performing the operation is added. Since the operational amplifier 13 outputs the cell voltage even when the battery pack P in which the protection circuit 2 is in the open state is connected, the charge control unit 4 always monitors the voltage. Is possible.

Even if an abnormal battery such as a battery cell 1 having a low voltage and the protection circuit 2 being in an open state is connected due to an internal short circuit or over-discharge, charging should be started with a small current. As a result, the charger is safe without being overloaded.

A charging method according to the third embodiment of the present invention will be described with reference to FIG.

In the charging system according to the third embodiment, the charging control unit 4 in FIG. 1 determines that the battery voltage is abnormal when the cell voltage is higher than the specified value, does not charge the battery, and displays the fact to the user. Even if an abnormal battery is connected which is over-voltage charged and the protection circuit 2 is in an open state, a large reverse current does not flow to the charger side. In addition, the user can recognize more than the battery, which increases safety.

Further, a charging system according to the fourth embodiment of the present invention will be described with reference to FIG.

The charging system according to the fourth embodiment has a function of detecting and displaying the charging capacity using the cell voltage in addition to the charging control unit 4 in FIG. 1, and is not affected by the variation of the protection circuit 2. It is possible to know the progress of charging with high accuracy.

Here, according to the charging methods of the first to fourth embodiments of the present invention described above, 75% to 80% of the charging capacity can be charged during the constant current period. Therefore, by detecting the cell voltage, the charge capacity can be detected and displayed at any point of 75% to 80% or less.

During the constant voltage charging period, it is impossible to detect the charging capacity based on the cell voltage, but since this period is the charging current decreasing period, the charging current may change. The charge capacity may be detected. With this method, the charge capacity can be detected and displayed in detail from the empty state of the battery to the state close to the completion of charging, which is a very convenient function for the user.

Further, not only the battery pack P of the lithium ion secondary battery but also other types of batteries such as NiCd and lead storage batteries, when the protection circuit is connected with the same configuration,
The charging method based on the cell voltage detection of the present invention can be applied.

Note that, in FIG. 1, the cell detection circuit composed of 8, 9, 10 and 12 and the operational amplifier 13 may be incorporated in the charge control unit 4 to be integrated. By doing so, it becomes possible to realize the present charging method more easily and at lower cost.

[0053]

As described above, according to the present invention, the charging is accurately controlled by the voltage of the battery cell without being influenced by the variation of the protection circuit for each battery pack, so that the efficiency is high and the deterioration of the battery performance is minimized. Charging of a lithium-ion secondary battery that has the function of detecting the charging capacity with high accuracy by enabling safe control even for an abnormal battery whose protection circuit is in an open state. Can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a lithium-ion secondary battery charging system according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an example of charging characteristics in the charging system of the present invention.

FIG. 3 is a characteristic diagram showing a comparison between charging characteristics according to the present invention and charging characteristics according to a conventional method.

FIG. 4 is a block diagram showing a configuration of a battery pack of a lithium ion secondary battery.

FIG. 5 is a block diagram showing a circuit configuration of a conventional charging system.

FIG. 6 is a characteristic diagram showing an example of charging characteristics in a conventional charging method.

[Explanation of symbols]

1 battery cell 2 protection circuit 3 power supply P battery pack 4 Charge control unit 5 Backflow prevention diode 6 Output control transistor 7 Current detection resistor 8, 9, 10, 12 resistance for cell voltage detection circuit 11 Battery protection resistor Operational amplifier for 13-cell voltage detection circuit A positive terminal B negative terminal C Battery cell negative electrode S Battery cell negative electrode potential detection terminal P battery pack

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-259934 (JP, A) JP-A-9-74688 (JP, A) JP-A-8-123587 (JP, A) JP-A-7- 326389 (JP, A) JP 11-97074 (JP, A) JP 11-149946 (JP, A) JP 9-129270 (JP, A) JP 7-107677 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02J 7/10 H01M 10/44 H02J 7/00

Claims (8)

(57) [Claims] 1. A lithium-ion secondary battery charging system having a structure in which a battery pack has a built-in protection circuit for preventing performance deterioration and destruction of battery cells, and a resistance component is connected in series with the battery cells. Te, the potential of the negative electrode of the battery cells provided in the battery pack detected by the battery cell negative electrode potential measuring terminals, and a power supply unit that outputs a direct current, a current detection resistor for detecting the charging current, the battery pack A cell voltage detection circuit that outputs the voltage of the battery cell, and a constant-current charge at the specified charging voltage or less, and a charge that controls the constant-voltage charging at the specified voltage after reaching the specified charging voltage. and a control unit constitute a charging circuit,
Connect one end of the protective resistor directly to the negative electrode side of the battery cell.
In addition, the negative electrode potential detection is directly applied to the other end of the protection resistor.
A lithium-ion secondary battery charging method , wherein a charging terminal is connected and the charging control unit is configured to perform charging control with the voltage of the battery cell. 2. The charging control unit checks the voltage of the battery cell before starting charging, performs charging with a small current if the voltage is equal to or lower than a specified voltage, and starts rapid charging after rising to the specified voltage. The lithium ion secondary battery charging method according to claim 1, wherein the charging method is controlled. 3. The charging control unit confirms the voltage of the battery cell before starting charging, determines that the battery is abnormal if the voltage is equal to or higher than a specified voltage, and controls not to charge the battery cell. The lithium-ion secondary battery charging method according to claim 2, wherein an abnormality is displayed. 4. The lithium ion secondary battery charging method according to claim 3, wherein the charge control unit detects the charge capacity of the battery cell by monitoring the voltage of the battery cell during charging. 5. A lithium ion secondary battery charger having a structure in which a battery circuit has a built-in protection circuit for preventing performance deterioration and destruction of battery cells, and a resistance component is connected in series with the battery cells. A battery cell negative electrode potential detection terminal for detecting a negative electrode potential of the battery cell provided in the battery pack, a power supply unit for outputting a direct current, a current detection resistor for detecting a charging current, and a battery cell of the battery pack Cell voltage detection circuit that outputs the voltage of the battery and a charging control unit that controls to perform constant current charging below the specified charging voltage and to perform constant voltage charging at the specified voltage after the specified charging voltage is reached. To form a charging circuit, and one end of the protective resistor is directly connected to the negative electrode side of the battery cell.
The negative electrode is directly connected to the other end of the protection resistor while being connected.
Connect the potential detecting terminal, a lithium ion secondary battery charger and feature in that the charging control unit is configured to charge control by the voltage of the battery cell. 6. The charging control unit confirms the voltage of the battery cell before starting charging, performs charging with a small current if the voltage is equal to or lower than a specified voltage, and controls to start rapid charging after rising to the specified voltage. The lithium ion secondary battery charger according to claim 5, wherein 7. The charging control unit confirms the voltage of the battery cell before starting charging, determines that the battery is abnormal if the voltage is equal to or higher than a specified voltage, and controls not to charge the battery cell. The lithium-ion secondary battery charger according to claim 6, which displays an abnormality. 8. The lithium-ion secondary battery charger according to claim 7, wherein the charge control unit detects the charge capacity of the battery cell by monitoring the voltage of the battery cell during charging.