JP3322780B2 - Rechargeable battery charging circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a charging circuit for a secondary battery, and more particularly to a charging circuit for charging a battery pack having a built-in protection circuit.

[0002]

2. Description of the Related Art In general, a non-aqueous solvent-based secondary battery such as a lithium secondary battery or a lead-acid battery has a battery voltage that is too low during discharging or standing, or conversely, too high during charging. The battery performance may be degraded or safety may be impaired. In particular, in the case of a lithium secondary battery, for example, when the battery voltage becomes 2 V or less, the copper of the current collector used for the negative electrode starts to dissolve in the electrolytic solution to deteriorate the battery performance, and the battery voltage becomes 4.5 V or more. As a result, gas is generated by decomposition of the electrolytic solution, and as a result, the pressure inside the battery increases, the safety valve operates, and liquid leakage may occur.

For this reason, it is necessary to monitor the battery voltage and control the charging and discharging so that the battery voltage is within a predetermined range before use. Conventionally, when a lithium secondary battery is used, the discharge current is cut off when the battery voltage drops and reaches a preset discharge prohibition voltage, and the charge is cut off when the battery voltage rises and reaches the charge prohibition voltage. A method of performing charging and discharging via a protection circuit having a function is generally employed.
Here, the discharge prohibition voltage is a voltage 2 at which the negative electrode copper begins to melt.
The voltage is set to a voltage higher than V, for example, 2.3 V, and the charging prohibition voltage is set to a voltage slightly lower than the voltage at which decomposition of the electrolytic solution starts, for example, 4.35 V.

In charging such a lithium secondary battery, the battery voltage is checked before a charging current is passed,
If the voltage is too low (for example, 2.15 V or less) or if the voltage is too high (for example, 4.35 V), charging is not performed.

[0005]

In the prior art described above, if a normal battery is left in a discharged state and the battery voltage falls below 2.3V and falls within a range of 2.15V or more, for example, the protection circuit is activated. In the cutoff state, the output voltage of the charger becomes 0
Become a bolt. In this case, even if an attempt is made to charge with the above-mentioned conventional charger, the output voltage is 0 volt, so that the battery cannot be charged even though it is normal, and the battery cannot be used.

The present invention has been made in view of the above circumstances, and when the battery voltage is lower than the discharge cut-off voltage of the protection circuit but not so low that the battery becomes abnormal, that is, the battery is normal, It is an object of the present invention to provide a charging circuit for a secondary battery that can perform normal charging even when a discharge cutoff function of a circuit operates.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, when a secondary battery is in a discharge interruption state, the interruption state is temporarily released and charging is performed while monitoring a terminal voltage of the secondary battery. Is performed.

That is, a charging circuit for a secondary battery according to the present invention includes a switch element connected between the first and second terminals in series with the secondary battery, for flowing a discharge current of the secondary battery, First voltage comparing means for comparing the voltage of the secondary battery with the first set voltage and generating an overdischarge detection output when the voltage of the secondary battery falls below the first set voltage; Discharge control means for holding the cutoff state of the switch element with respect to the overdischarge detection output of the voltage comparison means and for turning on the switch element when a charging current flows to the secondary battery; Second voltage comparing means for comparing the inter-terminal voltage with a second set voltage lower than the first set voltage; and third voltage comparing means for comparing the inter-terminal voltage with a third set voltage lower than the second set voltage. And I3, I2 and I3 in the secondary battery (however, , I1 <I2 <I3) controlling the charging of the secondary battery based on the first, second and third charging power supplies for supplying the charging current and the outputs of the second and third voltage comparing means. Charge control means, wherein the charge control means (a) supplies a charging current to the secondary battery from a third charging power source when the inter-terminal voltage is equal to or higher than a second set voltage;
(b) When the voltage between terminals is less than the second set voltage, the first
Supplying charging current to the secondary battery from the charging power source of (c).
If the inter-terminal voltage is less than the third set voltage in the state of (b), the supply of the charging current from the first, second and third charging power supplies to the secondary battery is stopped, and (d) ( If the inter-terminal voltage is equal to or higher than the third set voltage in the state of b), a predetermined amount of charging current is supplied from the second charging power source to the secondary battery. If the voltage is equal to or higher than the second set voltage, a charging current is supplied from the third charging power source to the secondary battery, and if the inter-terminal voltage is less than the second set voltage in the states (f) and (d), Control for stopping the supply of current from the first, second, and third charging power sources is performed.

Here, taking the case of a lithium secondary battery as an example, the first set voltage is set to a discharge prohibition voltage slightly higher than the voltage at which the negative electrode copper begins to melt, and the third set voltage is set to The voltage is set to a charging prohibition voltage at which charging becomes dangerous because the voltage becomes too low, and the second set voltage is set to an intermediate value between the first set voltage and the third set voltage.

[0010] According to the charging circuit for a secondary battery configured as described above, the terminal voltage (battery voltage) of the secondary battery becomes lower than the first set voltage (discharge inhibition voltage), and the switch element is cut off. When the secondary battery is in the discharge cutoff state and the first and second terminal voltages are equal to or higher than the second set voltage, quick charging is performed by the third charging power supply. When the inter-terminal voltage is less than the second set voltage, a current flows from the first charging power supply to the secondary battery, so that the switch element is turned on, and the secondary battery is released from the discharge cutoff state. And become conductive. In this state, if the inter-terminal voltage is equal to or higher than the third set voltage, a predetermined amount of charging is performed by the second charging power supply. The quick charging is performed by the charging power source of No. 3.

When the battery voltage is equal to or higher than the first set voltage, the secondary battery is released according to the inter-terminal voltage in the same manner as in the case described above, after the discharge cutoff state of the secondary battery is released and the conductive state is established. Alternatively, charging is performed by a third charging power supply.

As described above, according to the present invention, even when the battery voltage is lower than the discharge cut-off voltage, but not so low that the battery becomes abnormal, that is, even when the battery is normal but the discharge cut-off function is working. , And proper charging can be performed according to the voltage between terminals. At this time, efficient charging is performed by appropriately setting the second set voltage. Further, in the charging after the discharge cutoff state of the secondary battery is released, if the inter-terminal voltage is lower than the third set voltage (charging prohibition voltage), the charging is not performed, and the charging is performed immediately after the first charging. A quick charge is not performed by the charging power supply, but a fixed amount of charging is performed by the second charging power supply, and after the voltage exceeds the second set voltage, the quick charging is performed by the first charging and charging power supply. In addition, when the charging is performed by the second charging power supply but the voltage is less than the second set voltage, the charging is stopped. For this reason, even if an abnormality has occurred in the secondary battery, no burden is imposed on the secondary battery due to quick charging, and appropriate measures can be taken even for an abnormality in the secondary battery.

In the present invention, the diode is connected in parallel with the switch element so that the forward direction matches the charging direction of the secondary battery, and the discharge control means determines that the voltage of the secondary battery has reached the first set voltage. At this time, the switch element may be configured to be in a conductive state.

In the rechargeable battery charging circuit having such a configuration, when the inter-terminal voltage is less than the second set voltage in a state where the rechargeable battery is in the discharge cutoff state, the switch element maintains the cutoff state. Meanwhile, current flows from the first charging power source to the secondary battery via the diode, and charging of the secondary battery is started. Thereafter, the secondary battery is charged by the first, second, and third charging power supplies according to the inter-terminal voltage, and when the battery voltage reaches a first set voltage (discharge inhibition voltage), the switch element is turned on. Becomes conductive. In other words, the switch element for flowing the discharge current of the secondary battery remains shut off until the battery voltage reaches the discharge prohibition voltage. Even if the current is interrupted,
Since the secondary battery keeps maintaining the discharge cutoff state, the safety of the secondary battery can be ensured.

Further, in the present invention, the first charging power supply and the second charging power supply may be configured in common, or the second charging power supply and the third charging power supply may be configured in common. . In this case, the charging control means (a) supplies the charging current from the second charging power source to the secondary battery when the terminal voltage is equal to or higher than the second set voltage, and (b) sets the terminal voltage to the second setting voltage. If the voltage is less than the third set voltage, the charging current is supplied from the first charging power source to the secondary battery if the voltage is less than the third set voltage in the states (c) and (b). And stopping the supply of the charging current from the second charging power supply to the secondary battery. If the inter-terminal voltage is equal to or higher than the third set voltage in the state of (d) and (b), the first charging power supply Supplying a predetermined amount of charging current to the secondary battery, and (e)
If the inter-terminal voltage is equal to or higher than the second set voltage in the state of (d), a charging current is supplied from the second charging power source to the secondary battery,
(f) If the inter-terminal voltage is less than the second set voltage in the state of (d), control is performed to stop the supply of current from the first and second charging power supplies.

[0016]

FIG. 1 is a diagram showing a configuration of a charging circuit for a secondary battery according to a first embodiment of the present invention. The charging circuit of the secondary battery is roughly divided into a battery pack 10 and
And a charger 20 for charging the battery.

The battery pack 10 includes a secondary battery 11, an FET (field effect transistor) 1 for flowing a discharge current, an FET 2 for flowing a charge current, a first voltage comparison unit 12, a discharge control circuit 13, Fourth voltage comparison unit 14
Consists of The secondary battery 11, FET2, and FET2 are connected in series between the external terminals a-1 and b-1. Note that the diode D1 is connected to the secondary battery 11 in the FET1.
Connected so that the forward direction matches the charging direction of the
2, a diode D2 is connected so that the forward direction matches the discharge direction of the secondary battery 11.

The first voltage comparator 12 generates an overdischarge detection output when the terminal voltage of the secondary battery 11 drops below a first set voltage (reference voltage V1). Reference voltage generating circuit R for generating V1
EF1. The inverting input terminal of the comparator A1 is commonly connected to the positive terminal of the secondary battery 11 and the external terminal a-1, the non-inverting input terminal of the comparator A1 is connected to the positive terminal of the reference voltage generating circuit REF1, and the reference voltage generating circuit The negative terminal of REF1 is connected to the negative terminal of the secondary battery 11. The reference voltage V1 is set to, for example, a charge prohibition voltage slightly higher than a voltage value at which the negative electrode copper starts to dissolve in a lithium secondary battery.

The fourth voltage comparing section 14 includes a comparator A
2 and a reference voltage generating circuit REF2 for generating a reference voltage Va
The inverting input terminal of the comparator A2 is connected to the plus terminal of the secondary battery 11, the non-inverting input terminal of the comparator A2 is connected to the plus terminal of the reference voltage generation circuit REF2, and the minus terminal of the reference voltage generation circuit REF2. Is connected to the negative terminal of the secondary battery 11. The reference voltage Va is set to a charge prohibition voltage slightly lower than a voltage at which the decomposition of the electrolyte starts due to an excessively high voltage in a lithium secondary battery, for example.

The discharge control circuit 13 comprises an RS flip-flop circuit FF, a comparator A3, and a reference voltage generation circuit REF3 for generating a reference voltage Vb.
The set input terminal S of the flip-flop circuit FF is connected to the output terminal of the comparator A1, and the reset input terminal R
Is connected to the output terminal of the comparator A3, the non-inverting input terminal of the comparator A3 is connected to the minus terminal of the secondary battery 11, and the inverting input terminal is connected to the reference voltage generation circuit REF3.
Connected to the positive terminal of Further, the source terminal of FET1 is connected to the negative terminal of the secondary battery 11, and FE
The drain terminal of T1, the drain terminal of FET2, and the negative terminal of the reference voltage generation circuit REF3 are commonly connected to each other, and the source terminal of FET2 is connected to the external terminal b-1. The inverted output terminal / Q of the flip-flop circuit FF is connected to the gate terminal of the FET1, and the gate terminal of the FET2 is connected to the output terminal of the comparator A2. The reference voltage Vb is set such that VF>Vb> 0 when the forward voltage drop voltage of the diode D1 is VF.

The charger 20 includes a second voltage comparison unit 21 and
A third voltage comparison unit 22, a charge control circuit 23,
Third and fourth switch elements SW2, SW3 and S
W4 and first, second, and third charging power supplies 24, 2
5 and 26.

The second voltage comparing section 21 includes a comparator A
4 and a reference voltage generating circuit REF4 for generating a reference voltage V2 as a second set voltage. A non-inverting input terminal of the comparator A4 is connected to an external terminal a-2, and an inverting input terminal of the comparator A4 is a reference voltage. The plus terminal of the generator REF4 is connected, and the minus terminal of the reference voltage generator REF4 is connected to the external terminal b-2. In addition,
The reference voltage V2 includes a reference voltage V1 and a reference voltage V3 described later.
Set an appropriate value between the two.

The third voltage comparing section 22 includes a comparator A
5 and a reference voltage generating circuit REF5 for generating a reference voltage V3 which is a third set voltage lower than the second set voltage. The non-inverting input terminal of the comparator A5 is connected to an external terminal a-.
2, the inverting input terminal of the comparator A5 is connected to the plus terminal of the reference voltage generation circuit REF5, and the minus terminal of the reference voltage generation circuit REF5 is connected to the external terminal b-2. The reference voltage V3 is set to, for example, a charge prohibition voltage that is a value at which charging becomes dangerous because the voltage of the lithium secondary battery becomes too low.

The charge control circuit 23 includes a second voltage comparison unit 2
The switching elements SW2, SW3, and SW4 are turned on or off by the output signals of the first and third voltage comparison units 22, and are switched.
4 has one terminal connected to the external terminal a-2.

The first charging power supply 24 has a maximum charging current I1
The second charging power supply 25 outputs the maximum charging current I2,
Output the maximum charging current I3. One terminal of the first charging power supply 24 is connected to the other terminal of the second switch element SW2, one terminal of the second charging power supply 25 is connected to the other terminal of the third switch element SW3, One terminal of the charging power supply 26 is connected to the other terminal of the fourth switch element SW4. For the charging power supplies 24, 25, and 26, for example, a power supply circuit that rectifies the output of an AC power supply to obtain a direct current, or another relatively large capacity battery is used. Note that the maximum charging currents I1, I
2, and I3 are in a relationship of I1 <I2 <I3;
When each of the currents is supplied to the battery pack 10, the maximum charging current I1 is set to a very small current such that the voltage drop in the FET1 and the FET2 becomes extremely small.
Is a current sufficient for the terminal voltage VB of the secondary battery 11 to rise from V3 to the reference voltage V2 by charging for a predetermined time Ta described later, and the maximum charging current I3 is sufficient for rapidly charging the secondary battery 11. Current.

Next, the operation of this embodiment will be described with reference to the flowchart shown in FIG. First, regarding the terminal voltage VB of the secondary battery 11, the reference voltage V1 and the reference voltage V
Compare with a. Here, the reference voltage V1 is
For example, it is assumed that the discharge prohibition voltage of No. 1 is set to 2.3 V, and the reference voltage Va is set to, for example, 4.35 V as an overcharge prevention voltage of the secondary battery 11.

When Va.gtoreq.VB.gtoreq.V1, the output of the comparator A1 is at a low level, and the inverted output terminal / Q of the flip-flop circuit FF remains at a high level, so that the FET1 is in a conductive state. Also, the comparator A
Since the output of 2 is at a high level, FET2 is also conductive. At this time, when the battery pack 10 and the charger 20 are connected, the external terminals a-1 and a-2, and b-1 and b-2 are connected, respectively. The charge control circuit 23 includes a switch element S
W2, SW3 and SW4 are cut off and the comparator A4
Compares the terminal voltage Vp, which is the voltage of the series circuit of the secondary battery 11, FET1, and FET2, with the reference voltage V2. At this time, the charge / discharge voltage is 0, and FET1 and F
Since both ET2 are conducting, FET1 and FE2
There is no voltage drop at T2, and the terminal voltage Vp is the terminal voltage Vp.
B. The value of the reference voltage V2 is, for example, 1
It is assumed that 2.15 V is set per cell.

When Vp ≧ V2 (YE in step S2)
S), the charging control circuit 23 determines that the fourth switch element SW4
, And a large current is supplied from the third charging power supply 26 to the secondary battery 11 to start rapid charging.

When Vp <V2 (NO in step S2)
, The charging control circuit 23 makes only the second switch element SW2 conductive (step 3), and causes a minute current to flow from the first charging power supply 24 to the secondary battery 11. Here, the terminal voltage Vp
And a reference voltage V3 are compared by a comparator A5. At this time, the charging / discharging current is very small, and FET1 and FET2
Are in a conductive state, and their internal resistance is very small (for example, 50 mΩ per FET). Therefore, there is almost no voltage drop, and the terminal voltage Vp becomes almost equal to the terminal voltage VB. The value of the reference voltage V3 is set to, for example, 1 in consideration of a voltage value at which the voltage of the secondary battery 11 becomes too low and becomes abnormal.
Set to 2.0V per cell.

When Vp <V3 (NO in step S4)
Since the terminal voltage VB is too low and is abnormal, the switch elements SW2, SW3 and SW4 are turned off and charging is not performed. At this time, a battery abnormality is displayed as needed (step S6).

When Vp ≧ V3 (YE in step S4)
S), only the switch element SW3 conducts, and the secondary battery 11 is charged with the maximum charging current I2 from the second charging power supply 24. Here, the charging with the second charging power supply 24 is continued until the predetermined time Ta elapses (NO in step S8). The predetermined time Ta is set to a time sufficient for the terminal voltage VB to rise from V3 to the reference voltage V2. When the predetermined time Ta has elapsed (YE in step S8)
S), the switch elements SW2, SW3 and SW4 are cut off (step S9), and the inter-terminal voltage Vp is compared with the reference voltage V2. Here, when Vp ≧ V2 (step S10
Is YES), the switch element SW4 is turned on (step S11), and the secondary battery 11 is charged with the maximum charging current I3 from the third charging power source 26,
Quick charging is started. When Vp <V3 (Step S
(NO in 10), since the secondary battery 11 is abnormal, the switch elements SW2, SW3 and SW4 are shut off (step S5), and charging is not performed.

Next, when the terminal voltage VB of the secondary battery 11 is VB
When <V1, since the output of the comparator A1 is at a high level, the inverted output terminal /
Q is low and FET1 is off. On the other hand, the output of the comparator A2 is also at a high level,
2 is a conduction state. At this time, when the battery pack 10 and the charger 20 are connected, the charge control circuit 23 turns off the switch elements SW2, SW3, and SW4 (step S1), and in this state, the comparator A2 sets the terminal voltage Vp.
And the reference voltage V2. At this time, since the FET 1 is in the cutoff state and the charging current is 0, the inter-terminal voltage Vp becomes 0 V. Therefore, Vp <V2 (step S
2; NO), the charge control circuit 23
Only W2 is made conductive (step S3), and a minute current flows from the first charging power supply 24 to the secondary battery 11. Then FE
Although the source and the drain of T1 are cut off, a charging current flows through the diode D1, and the forward voltage effect voltage of the diode D1 at this time is VF, and the reference voltage V
When b is set so that VF>Vb> 0, the source-
Since the voltage VSD between the drains becomes VSD> Vb, the output of the comparator A3 goes high, that is, the reset input terminal R of the flip-flop circuit FF goes high, the flip-flop circuit FF is reset, and the inverted output terminal / Q becomes high. The level becomes high, and FET1 becomes conductive like FET2. After this, the same operation as in step S4 and thereafter when the terminal voltage of the secondary battery 11 is Va ≧ VB ≧ V1 is performed.

The battery pack 10 shown in FIG. 1 has an overcharge prevention function comprising a second voltage comparison circuit 14,
When the terminal voltage VB becomes higher than the reference voltage Va due to an abnormality of the charger 20 or the like, the output of the comparator A2 becomes low level so that the FET2 is turned off and the battery pack 10 and the charger 20 are connected. I try not to charge it.

As described above, in the rechargeable battery charging circuit according to the present embodiment, the battery voltage is lower than the discharge cutoff voltage, but the battery voltage does not drop so much that the battery becomes abnormal, that is, the battery is normal. However, the discharge interruption function of the protection circuit is working, and the external output terminal a-
Even when no voltage is applied to 1 and a-2, charging can be performed normally.

Hereinafter, another embodiment of the present invention will be described with reference to FIG.
In the following embodiments, the same reference numerals are given to portions corresponding to those in FIGS. 1 and 2, and differences from the first embodiment will be mainly described.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a charging circuit for a secondary battery according to the embodiment. In the present embodiment, the discharge control circuit 13 shown in FIG.
The non-inverting input terminal of the comparator A3 is connected to the plus terminal of the secondary battery 11, the inverting input terminal is connected to the plus terminal of the reference voltage generating circuit REF6 that generates the reference voltage V1, and the minus terminal of the reference voltage generating circuit REF6 is connected. The terminal is configured to be connected to the negative terminal of the secondary battery 11.

In this embodiment, when the terminal voltage VB of the secondary battery 11 satisfies VB <V1, the output of the comparator A1 goes high and the output of the comparator A1 goes low at the same time. The inverting output terminal / Q of the circuit FF becomes low level, the FET1 is cut off, and the secondary battery 11 enters a discharge cutoff state. From now on,
As in the first embodiment, the first, second, and third charging power supplies 24, 25, and 2 depend on the value of the inter-terminal voltage Vp.
6, the secondary battery 11 is charged, and the secondary battery 11 is charged.
If there is an abnormality in the charging, the charging is stopped.

At this time, in the first embodiment, when a charging current flows through the diode D1, the comparator A
3, the FET 1 is turned on, and the secondary battery 11 is released from the discharge cutoff state.
Until the terminal voltage VB of the secondary battery 11 reaches the first reference voltage V1, the secondary battery 11 is kept in the discharge cutoff state, and the charging current is supplied to the secondary battery 11 via the diode D1. . When the terminal voltage VB reaches the first reference voltage V1, the comparator A3 sets the FE to FE.
T1 becomes conductive, and the discharge cutoff state of the secondary battery 11 is released.

For this reason, even if a failure or the like occurs in the circuit in a range lower than the discharge prohibition voltage and the charging current is interrupted, the secondary battery 11 keeps the discharge interrupted state. The safety of the secondary battery can be secured.

The present invention is not limited to the above embodiment, but can be implemented with various modifications as follows. (1) In the above embodiment, three charging power supplies are provided using the first, second, and third charging power supplies 24, 25, and 26 that generate charging currents of the maximum charging currents I1, I2, and I3. Although the case has been described, I1 and I2 may be common, or I2 and I3 may be common and two power supplies for charging may be used. Also, the first, second and third charging power supplies may be pulsed, in which case the average may be I1, I2 and I3. (2) In the above-described embodiment, the two methods of overdischarge protection and overcharge protection
Although the case where there are two protection functions has been described, excessive current charging, excessive current discharging protection, and other protection functions may be added. (3) In the above embodiment, the battery pack 10 and the charger 20
However, the secondary battery 11 and the charging circuit may be built in the device body in advance.

[0041]

As described above, according to the present invention,
When the secondary battery is in the discharge interruption state, the interruption state is released once, and the battery is charged while monitoring the battery voltage, so that the battery voltage is lower than the discharge interruption voltage of the protection circuit but the battery becomes abnormal. When the battery has not dropped, that is, the battery is normal, but the battery can be charged normally even when the discharge cutoff function of the protection circuit operates.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a charging circuit for a secondary battery according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment;

FIG. 3 is a diagram illustrating a configuration of a charging circuit for a secondary battery according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Battery pack 11 ... Secondary battery 12 ... First voltage comparison part 13 ... Discharge control circuit 14 ... Fourth voltage comparison part 20 ... Charger 21 ... Second voltage comparison part 22 ... Third voltage comparison part 23 ... Charge control circuit 24 ... First charging power supply 25 ... Second charging power supply 26 ... Third charging power supply FET1, FET2 ... Field effect transistors A1 to A5 ... Comparator REF1 to REF6 ... Reference voltage generation circuit V1 ... V3, Va, Vb: Reference voltage D1, D2: Diode FF: Flip-flop circuit S: Set input terminal R: Reset input terminal / Q: Inverted output terminal a-1, b-1: External terminal a-2, b -2: external terminal SW2: second switch element SW3: third switch element SW4: fourth switch element

Continuation of the front page (72) Inventor Kazuo Muko 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside A / T Battery Co., Ltd. (56) References JP-A-9-17455 (JP, A) JP-A-5-276682 (JP, A) JP-A-2-254930 (JP, A) JP-A-5-49181 (JP, A) JP-A-5-111177 (JP, A) JP-A-6-105458 (JP, A) Kaihei 7-7864 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J 7/10 H01M 10/44

Claims (4)

(57) [Claims] A switch connected between the first and second terminals in series with the secondary battery for flowing a discharge current of the secondary battery; and a voltage of the secondary battery and a first set voltage. And a first voltage comparison means for generating an overdischarge detection output when the voltage of the secondary battery falls below a first set voltage; and an overdischarge detection output of the first voltage comparison means. Discharging control means for holding the cutoff state of the switch element and for turning the switch element into a conductive state when a charging current flows to the secondary battery; and a voltage between terminals of the first and second terminals and the first Second voltage comparing means for comparing a second set voltage lower than the second set voltage, and third voltage comparing means for comparing the inter-terminal voltage and a third set voltage lower than the second set voltage. And I1, I2 and I3 (where I1 I
2 <I3) controlling charging of the secondary battery based on first, second and third charging power supplies for supplying a charging current, and outputs of the second and third voltage comparing means. Charge control means, the charge control means comprising: (a) supplying a charge current from the third power supply to the secondary battery when the inter-terminal voltage is equal to or higher than the second set voltage. (B) when the inter-terminal voltage is less than the second set voltage, supplying a charging current to the secondary battery from the first charging power source; (c) in the state of (b), When the intermediate voltage is less than the third set voltage, the supply of the charging current from the first, second, and third charging power supplies to the secondary battery is stopped, and the state of (d) and (b) When the inter-terminal voltage is equal to or higher than the third set voltage, a predetermined amount of charge is supplied from the second charging power source to the secondary battery. (E) when the inter-terminal voltage is equal to or higher than the second set voltage in the state of (d), supplying a charging current to the secondary battery from the third charging power source; In the state (d), when the inter-terminal voltage is less than the second set voltage, control is performed to stop supply of current from the first, second, and third charging power supplies. Rechargeable battery charging circuit. 2. A switch element connected in series with a secondary battery between first and second terminals for flowing a discharge current of the secondary battery, a voltage of the secondary battery and a first set voltage. And a first voltage comparison means for generating an overdischarge detection output when the voltage of the secondary battery falls below a first set voltage; and an overdischarge detection output of the first voltage comparison means. Discharging control means for holding the cutoff state of the switch element and for turning the switch element into a conductive state when a charging current flows to the secondary battery; and a voltage between terminals of the first and second terminals and the first Second voltage comparing means for comparing a second set voltage lower than the second set voltage, and third voltage comparing means for comparing the inter-terminal voltage and a third set voltage lower than the second set voltage. And I1 and I2 (where I1 <I2) in the secondary battery. First and second charging power supplies for supplying a charging current; and charging control means for controlling charging of the secondary battery based on outputs of the second and third voltage comparing means, The charging control means includes: (a) when the terminal voltage is equal to or higher than the second set voltage, supplies a charging current to the secondary battery from the second charging power source; (b) the terminal voltage Is less than the second set voltage, a charging current is supplied from the first charging power source to the secondary battery, and in the state of (c) and (b), the inter-terminal voltage is set to the third set voltage. When the voltage is less than the voltage, the supply of the charging current from the first and second charging power supplies to the secondary battery is stopped, and in the state of (d) and (b), the voltage between the terminals is set to the third setting. When the voltage is equal to or more than the voltage, a charging current is supplied from the first charging power source to the secondary battery by a predetermined amount, and in the states (e) and (d), When the inter-terminal voltage is equal to or higher than the second set voltage, a charging current is supplied from the second charging power source to the secondary battery. 2. A charging circuit for a secondary battery, which performs control to stop supply of current from the first and second charging power supplies when the voltage is less than the second set voltage. 3. A switch element connected between the first and second terminals in series with a secondary battery for flowing a discharge current of the secondary battery, and a forward direction coincides with a charging direction of the secondary battery. Comparing the diode connected in parallel with the switch element to the voltage of the secondary battery and a first set voltage, and detecting an overdischarge when the voltage of the secondary battery falls below the first set voltage. A first voltage comparing means for generating an output, and an over-discharge detection output of the first voltage comparing means, wherein the switch element is held in a cut-off state, and a voltage of the secondary battery is the first set voltage. A discharge control means for setting the switch element to a conductive state when the voltage reaches the second set voltage, and a second set voltage comparing the inter-terminal voltage of the first and second terminals with a second set voltage lower than the first set voltage. Voltage comparing means, the inter-terminal voltage and the second A third voltage comparing means for comparing the lower than the set voltage third set voltage, the secondary battery I1, I2 and I3 (where, I1 <I
2 <I3) controlling charging of the secondary battery based on first, second and third charging power supplies for supplying a charging current, and outputs of the second and third voltage comparing means. Charge control means, the charge control means comprising: (a) supplying a charge current from the third power supply to the secondary battery when the inter-terminal voltage is equal to or higher than the second set voltage. (B) when the inter-terminal voltage is less than the second set voltage, supplying a charging current to the secondary battery from the first charging power source; (c) in the state of (b), When the intermediate voltage is less than the third set voltage, the supply of the charging current from the first, second, and third charging power supplies to the secondary battery is stopped, and the state of (d) and (b) When the inter-terminal voltage is equal to or higher than the third set voltage, a predetermined amount of charge is supplied from the second charging power source to the secondary battery. (E) when the inter-terminal voltage is equal to or higher than the second set voltage in the state of (d), supplying a charging current to the secondary battery from the third charging power source; In the state (d), when the inter-terminal voltage is less than the second set voltage, control is performed to stop supply of current from the first, second, and third charging power supplies. Rechargeable battery charging circuit. 4. A switching element connected between the first and second terminals in series with a secondary battery for flowing a discharge current of the secondary battery, and a forward direction coincides with a charging direction of the secondary battery. Comparing the diode connected in parallel with the switch element to the voltage of the secondary battery and a first set voltage, and detecting an overdischarge when the voltage of the secondary battery falls below the first set voltage. A first voltage comparing means for generating an output, and an over-discharge detection output of the first voltage comparing means, wherein the switch element is held in a cut-off state, and a voltage of the secondary battery is the first set voltage. A discharge control means for setting the switch element to a conductive state when the voltage reaches the second set voltage, and a second set voltage comparing the inter-terminal voltage of the first and second terminals with a second set voltage lower than the first set voltage. Voltage comparing means, the inter-terminal voltage and the second Third voltage comparing means for comparing a third set voltage lower than the set voltage, and first and second means for supplying a charging current I1, I2 (where I1 <I2) to the secondary battery. A charge power supply; and charge control means for controlling charging of the secondary battery based on outputs of the second and third voltage comparison means, wherein: (a) the terminal voltage When the voltage is equal to or higher than the second set voltage, a charging current is supplied from the second charging power source to the secondary battery. (B) When the inter-terminal voltage is less than the second set voltage, A charging current is supplied from the first charging power source to the secondary battery. If the inter-terminal voltage is less than the third set voltage in the states of (c) and (b), the first and second Stop supplying the charging current from the charging power supply to the secondary battery, and in the state (d) and (b), When the voltage is equal to or higher than the third set voltage, a predetermined amount of charging current is supplied from the first charging power source to the secondary battery. When the voltage is equal to or higher than the set voltage, the charging current is supplied from the second charging power source to the secondary battery, and when the voltage between the terminals is less than the second set voltage in the state of (f) and (d), A control circuit for stopping supply of current from the first and second charging power supplies.