JPH0974688A - Battery charging circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To share a battery charging circuit for a plurality of kinds of battery packs by providing an error amplifier which supplies a voltage of logic '0' to an output terminal when the voltage of a battery is lower than a reference value or a voltage of logic '1' when the voltage of the battery is higher than the reference value and turning on/off a switch control terminal by receiving the voltage supplied from the amplifier. SOLUTION: A battery charging circuit is provided with an error amplifier EA which controls a charging switch 14 upon receiving the fully charged voltage VREF of a battery pack 11 charged with a DC power supply voltage VCC and the voltage at an intermediate tap which is obtained by dividing the voltage VD of the pack 11 with a resistor. The switch 14 is composed of a P-channel FET and the power supply voltage VCC is applied across the source S of the FET and the drain D of the FET is connected to the positive terminal +B of the pack 11. The gate G of the FET is connected to the amplifier EA and the switch 14 is set so that the switch 14 can be turned on and off when the input from the amplifier EA has logic '0' and '1'. Therefore, the battery charging circuit has an extremely large effect on the economy, because the circuit can be shared for a plurality of kinds of battery packs.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a charging circuit for charging a secondary battery such as a lithium ion battery.

[0002]

2. Description of the Related Art A secondary battery incorporated in a battery pack or the like of a portable electronic device is a battery that can be repeatedly used by recharging discharged electric power. Such a secondary battery has a defect that it is generally vulnerable to overdischarge and overcharge. Therefore, conventionally, a protection device is provided in the battery pack, and when the protection device detects an overcharged state or an overdischarged state of the secondary battery, charging by an external power source or discharge to an external load is blocked to prevent the secondary battery. It is usual to protect the battery.

[0003]

A battery pack having such a secondary battery contains one secondary battery or two or three secondary batteries connected in series with each other. There are various types of battery packs such as those that do.

The conventional charging circuit can only charge the secondary battery of one type of battery pack, and in order to charge a plurality of types of battery packs, a plurality of types of charging circuits must be prepared, which is economical. Not at all.

Further, in a battery pack containing a plurality of secondary batteries connected in series with each other, when the secondary batteries are in an overdischarged state, the capacity of the battery is reduced and the battery is overdischarged. I don't know if it was the one that was overcharged due to a short circuit or deterioration of the secondary battery. The battery pack usually has the protective device built therein as described above. In the case of over-discharging, the discharge control FET (field effect transistor) in the protective device is turned off. If you charge at this time,
A current flows through the body diode of the discharge control FET. At this time, when high current charging is performed, the discharge control FET generates heat,
A battery pack containing a secondary battery that is over-discharged due to a decrease in battery capacity may also be short-circuited or broken.

Therefore, it is an object of the present invention to provide a charging circuit which can be shared by a plurality of different types of battery packs.

Another object of the present invention is to charge a secondary battery in an over-discharged state with a low current first, raise the battery voltage to a dischargeable state, and carry out a large-current charging at that time. Accordingly, it is an object of the present invention to provide a charging circuit capable of safely charging a battery pack containing a secondary battery that has been over-discharged due to a decrease in battery capacity.

[0008]

According to one aspect of the present invention, there is provided a first battery pack having a first positive polarity terminal, a first negative polarity terminal, and a first battery unit, A charging circuit used in combination with any one of a second battery pack having a second positive terminal, a second negative terminal, and a second battery unit, the first battery Units are N connected in series with each other (N is an integer of 2 or more)
Second rechargeable batteries, the second battery unit has M (M is an integer greater than or equal to 1 smaller than N) rechargeable batteries connected in series, and the second rechargeable battery includes the N rechargeable batteries. The batteries and the M secondary batteries have the same full charge voltage in a fully charged state, and the N secondary batteries are
The first positive terminal and the first positive terminal are arranged such that the first positive terminal has a voltage N times the full charge voltage with respect to the first negative terminal in a fully charged state. One of the M secondary batteries is connected to one negative terminal, and the second positive terminal of the M secondary batteries is fully charged to the second negative terminal in a fully charged state. Is connected to the second positive polarity terminal and the second negative polarity terminal so that the charging circuit has a voltage M times higher than that of the second positive polarity terminal, and the charging circuit is combined with the first battery pack. When used, the N secondary batteries are charged such that the first positive terminal has a voltage N times the full charge voltage with respect to the first negative terminal, and the charging circuit When used in combination with the second battery pack, the second positive terminal The charging circuit is configured to charge the M secondary batteries to have a voltage M times the full charge voltage with respect to the second negative terminal, and the charging circuit includes a charging switch and a charging control. A charging circuit, the charging switch includes a switch input terminal to which a positive DC power supply voltage is applied, and the first battery pack when the charging circuit is used in combination with the first battery pack. Switch output connected to the first positive terminal of the second battery pack when the charging circuit is used in combination with the second battery pack. The switch control terminal has a terminal and a switch control terminal, and is turned on when a voltage of logical "0" is applied to the switch control terminal, and permits the DC power supply voltage of the switch input terminal to be sent to the switch output terminal. The control terminal is turned off when a voltage of logic "1" is applied to prohibit sending of the DC power supply voltage of the switch input terminal to the switch output terminal. A circuit input terminal connected to the DC power supply voltage, a circuit output terminal connected to the switch control terminal, and the charging circuit when the charging circuit is used in combination with the first battery pack. Connected to the first positive terminal and the switch output terminal of the battery pack, and when the charging circuit is used in combination with the second battery pack, the second battery pack A first positive terminal connecting terminal connected to a second positive terminal and also connected to the switch output terminal, and the charging circuit combined with the second battery pack. A second positive terminal connecting terminal connected to the second positive terminal of the second battery pack when used, the charging control circuit is connected to the circuit input terminal, A reference voltage circuit for converting a power supply voltage into a reference voltage equal to the full-charge voltage, and a divider negative polarity terminal, a divider positive polarity terminal, the divider negative polarity terminal and the divider positive polarity terminal are sequentially connected, Having first to Nth resistors connected in series with each other and having the same resistance value,
The divider negative polarity terminal is connected to ground, the divider positive polarity terminal is connected to the first positive polarity terminal connection terminal, and the Mth resistance of the first to Nth resistors is connected. And a (M + 1) th resistor connecting point is connected to the second positive terminal connecting terminal, the voltage divider for dividing the voltage of the first positive terminal connecting terminal, and the charging circuit. Comparing the voltage across the first resistor equal to the current voltage of one of the secondary batteries of the combined battery pack to the reference voltage, across the first resistor; When the voltage is lower than the reference voltage, the voltage of the logic "0" is supplied to the circuit output terminal, and when the voltage across the first resistor is equal to or higher than the reference voltage, the circuit output terminal is connected to the circuit output terminal. And an error amplifier that supplies a voltage of logic "1". That the charging circuit can be obtained.

According to a second aspect of the present invention, a first battery pack having a first positive polarity terminal, a first negative polarity terminal, and a first battery unit, and a second positive polarity A second terminal having a terminal, a second negative terminal, and a second battery unit
In the charging circuit, the first battery unit has N (N is an integer of 2 or more) secondary batteries connected in series with each other. The second battery unit has M (M is an integer of 1 or more smaller than N) secondary batteries connected in series, and the N secondary batteries and the M secondary batteries are connected to each other. The secondary batteries have the same full charge voltage in a fully charged state, and the N secondary batteries have the first positive terminal with the first negative electrode in a fully charged state. A positive polarity terminal and a first negative polarity terminal so as to have a voltage N times the full charge voltage with respect to a positive polarity terminal, and the M secondary batteries are respectively connected to the first positive polarity terminal and the first negative polarity terminal. Is fully charged, the second positive terminal is
Is connected to the second positive polarity terminal and the second negative polarity terminal so that the negative polarity terminal has a voltage M times the full charge voltage, and the charging circuit includes the charging circuit. When the battery pack is used in combination with the first battery pack, the N positive voltage terminals have a voltage N times the full charge voltage with respect to the first negative voltage terminal. When the secondary battery is charged and the charging circuit is used in combination with the second battery pack, the second positive terminal is M of the full charge voltage with respect to the second negative terminal.
The charging circuit has a charging switch and a charging control circuit, and the charging switch has a positive DC power source. When the switch input terminal to which a voltage is applied and the charging circuit are used in combination with the first battery pack, the switch input terminal is connected to the first positive terminal of the first battery pack, and the charging circuit is When used in combination with the second battery pack, it has a switch output terminal connected to the second positive terminal of the second battery pack and a switch control terminal, and the switch control terminal has a logic. It turns on when a voltage of "0" is applied, permits sending of the DC power supply voltage of the switch input terminal to the switch output terminal, and turns off when a voltage of logic "1" is applied to the switch control terminal. Is intended to prohibit the transmission to the switch output terminal of the DC power source voltage of the switch input terminal, the charge control circuit is connected to the switch input terminal, a circuit input terminal to which the DC power supply voltage is applied,
When the charging circuit is used in combination with the circuit output terminal connected to the switch control terminal, the charging circuit is connected to the first positive terminal of the first battery pack and A first positive terminal connecting terminal connected to the switch output terminal and the second positive terminal of the second battery pack when the charging circuit is used in combination with the second battery pack. And a second positive terminal connecting terminal connected to the switch output terminal, the charge control circuit is connected to the circuit input terminal, and the DC power supply voltage is equal to the full charge voltage. A reference voltage circuit for converting into a reference voltage is sequentially connected between the divider negative polarity terminal, the divider positive polarity terminal, the divider negative polarity terminal and the divider positive polarity terminal, and they are connected in series and mutually. First through N has a resistance value equal to
The divider negative polarity terminal is connected to ground, the divider positive polarity terminal is connected to the first positive polarity terminal connection terminal, and the first to Nth resistors. A voltage division for connecting a connection point between the Mth resistor and the (M + 1) th resistor in the second positive polarity terminal connection terminal to divide the voltage of the first positive polarity terminal connection terminal. And a voltage across the first resistor equal to the current voltage of one of the rechargeable battery and the secondary battery of the battery pack associated with the charging circuit is compared to the reference voltage,
When the voltage across the resistor is lower than the reference voltage, the logic "0" voltage is supplied to the circuit output terminal, and when the voltage across the first resistor is equal to or higher than the reference voltage. Is provided with an error amplifier that supplies the voltage of the logic "1" to the circuit output terminal.

According to a third aspect of the present invention, there is provided a charging circuit used in combination with a battery pack having a positive terminal, a negative terminal and a battery unit, wherein the battery units are mutually The battery includes N (N is an integer of 2 or more) secondary batteries connected in series, and the N secondary batteries have the same full charge voltage in a fully charged state. Each of the secondary batteries has the positive terminal and the negative terminal such that the positive terminal has a voltage N times the full charge voltage with respect to the negative terminal in a fully charged state. The charging circuit is for charging the N secondary batteries such that the positive terminal has a voltage N times the full charge voltage with respect to the negative terminal. Yes, the charging circuit has a charging switch and charging control And a road, the charge switch,
It has a switch input terminal to which a positive DC power supply voltage is applied, a switch output terminal connected to the positive terminal of the battery pack, and a switch control terminal, and a voltage of logic "0" is applied to the switch control terminal. Is turned on when the switch input terminal is turned on, the sending of the DC power supply voltage of the switch input terminal to the switch output terminal is permitted, and it is turned off when a voltage of logical “1” is applied to the switch control terminal, Sending a DC power supply voltage to the switch output terminal is prohibited, the charging control circuit is connected to the switch input terminal, the circuit input terminal to which the DC power supply voltage is applied, and the switch control terminal. The circuit has a circuit output terminal to be connected and a positive terminal connecting terminal that is connected to the positive terminal and is connected to the switch output terminal. A circuit connected to the circuit input terminal for converting the DC power supply voltage to a reference voltage equal to the full-charge voltage; a divider negative terminal, a divider positive terminal, and a divider negative terminal. And first to Nth resistors which are sequentially connected between the divider positive polarity terminals and which are connected in series with each other and have the same resistance value, and the divider negative polarity terminal is connected to the ground and The divider positive polarity terminal is connected to the positive polarity terminal connection terminal and is equal to the current voltage of one of the voltage divider that divides the voltage of the positive polarity terminal connection terminal and the secondary battery of the battery pack. The voltage across the first resistor is compared to the reference voltage, and when the voltage across the first resistor is less than the reference voltage, the logic "0" voltage is applied to the circuit output terminal. Supply the first When the voltage across resistor is equal to or higher than the reference voltage and an error amplifier for supplying a voltage of the logic "1" to the circuit output terminal,
The charge control circuit further has a negative terminal connecting terminal connected to the negative terminal, the negative terminal connecting terminal is connected to the ground through a resistor for current detection, The charge control circuit is further connected to the negative polarity terminal connection terminal, and supplies a voltage of the logic “1” to the circuit output terminal when the current flowing through the negative polarity terminal connection terminal is equal to or more than a predetermined current value. When the current flowing through the negative polarity terminal connection terminal is smaller than the predetermined current value, the N secondary batteries include a current limiting amplifier that supplies the voltage of the logic “0” to the circuit output terminal. Each has a voltage equal to or lower than a predetermined voltage lower than the full-charge voltage in a state of being over-discharged, and the charge control circuit further includes:
When it is detected that the voltage between both ends of the resistor is less than the predetermined voltage, the logic "1" voltage is output, and the logic "1" voltage is supplied to the circuit output terminal. And a low voltage detecting circuit for supplying the voltage of the logical "0" to the circuit output terminal when the voltage between both ends of the resistor is larger than the predetermined voltage, and the low voltage. A low current supply circuit for supplying the DC power supply voltage of the circuit input terminal as a low current to the positive polarity terminal connection terminal only while the detection circuit outputs the voltage of the logic "1", A charging circuit is obtained, characterized in that the low current is lower than the current flowing through this charging switch when said charging switch is turned on.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIGS. 1 and 2, the charging circuit 10 according to the first embodiment of the present invention includes a first battery pack 11
(FIG. 1) and the second battery pack 12 (FIG. 2) are used in combination.

In FIG. 1, the first battery pack 11 is
It has a first positive polarity terminal + B, a first negative polarity terminal -B, and a first battery unit. The first battery unit has N (N is an integer of 2 or more) secondary batteries 13 connected in series with each other. In the example shown, N is 2. In FIG. 2, the 2nd battery pack 12 has the 2nd positive polarity terminal + B, the 2nd negative polarity terminal -B, and the 2nd battery unit. The second battery unit has M (M is an integer of 1 or more smaller than N) number of secondary batteries 13 connected in series with each other. In the example shown, M is 1
It is. 1 and 2, the N (= 2) secondary batteries 13 and the M (= 1) secondary batteries 13 have the same full charge voltage in a fully charged state.

Referring to FIG. 3, there is shown the relationship between the battery voltage and the usage time when the secondary battery is a lithium ion battery. This lithium-ion battery has a full charge voltage of, for example, 4.2V. The battery voltage of this lithium-ion battery gradually drops from 4.2 V to 3.0 V with use time. After the voltage drops to 3.0 V, the battery voltage drops sharply and becomes an over-discharged state.

In FIG. 1, N (= 2) secondary batteries 1
3 shows that the first positive terminal + B has a full charge voltage N with respect to the first negative terminal -B in a fully charged state.
The first positive terminal + B so as to have a voltage of (= 2) times
And the first negative terminal-B. In FIG. 2, in the M (= 1) rechargeable batteries, the second positive terminal + B has a full charge voltage of M (= 1) The second positive terminal + B and the second negative terminal -B so that the voltage is doubled.
It is connected to the.

In FIG. 1, the charging circuit 10 has a first positive terminal + B and a first negative terminal −B when the charging circuit 10 is used in combination with the first battery pack 11.
This is for charging the N (= 2) secondary batteries 13 so that the battery B has a voltage N (= 2) times the full charge voltage. In FIG. 2, the charging circuit 10 is the charging circuit 1
When 0 is used in combination with the second battery pack 12, the second positive terminal + B has a voltage M (= 1) times the full charge voltage with respect to the second negative terminal -B. To M
This is for charging (= 1) secondary batteries 13.

In FIGS. 1 and 2, the charging circuit 10 is
The charging switch 14 includes a P-channel FET and a charging control circuit 15. The charging switch 14 includes a switch input terminal (source of P-channel FET) S, a switch output terminal (drain of P-channel FET) D,
It has a switch control terminal (P-channel FET gate) G. A positive DC power supply voltage VCC is applied to the switch input terminal S. The switch output terminal D is connected to the first positive terminal + B of the first battery pack 11 when the charging circuit 10 is used in combination with the first battery pack 11, and the charging circuit 10 is connected to the second battery. Pack 12
When used in combination with, the battery is connected to the second positive terminal + B of the second battery pack 12. The charging switch 14 is turned on when a voltage of logic “0” (specifically, a ground voltage) is applied to the switch control terminal G, and permits the DC power supply voltage VCC of the switch input terminal S to be sent to the switch output terminal D. When the voltage of the logic "1" (specifically, the positive voltage) is applied to the switch control terminal G, the switch control terminal G is turned off, and the DC power supply voltage VCC of the switch input terminal S is prohibited from being sent to the switch output terminal D. is there.

The charge control circuit 15 has a switch input terminal S.
A circuit input terminal IN to which the DC power supply voltage VCC is applied, a circuit output terminal EXT connected to the switch control terminal G, a first positive terminal connection terminal CEL2,
It has a second positive terminal connecting terminal CEL1. The first positive polarity terminal connection terminal CEL2 has a first positive polarity of the first battery pack 11 when the charging circuit 10 is used in combination with the first battery pack 11 (in the case of FIG. 1). When the charging circuit 10 is connected to the terminal + B and is also connected to the switch output terminal D and is used in combination with the second battery pack 12 (in the case of FIG. 2), the second battery pack 12 2 and the switch output terminal D. The second positive polarity terminal connection terminal CEL1 has a second positive polarity of the second battery pack 12 only when the charging circuit 10 is used in combination with the second battery pack 12 (in the case of FIG. 2). Connected to terminal + B.

The charge control circuit 15 has a reference voltage circuit 16 connected to the circuit input terminal IN. The reference voltage circuit 16 has a reference voltage VRE equal to the DC power supply voltage VCC equal to the full charge voltage (4.2V in the example of a lithium ion battery).
Convert to F. Specifically, the reference voltage circuit 16 includes a starting circuit including a current mirror circuit 17, a reference voltage generating circuit including a bandgap Zener diode ZD,
And another reference voltage generating circuit including an operational amplifier OP. The start switch 18 is closed and the switch terminal S
When W becomes the ground potential, a bias current flows from the circuit input terminal IN through the current mirror circuit 17 of the starting circuit,
The bandgap Zener diode ZD becomes active. The bandgap Zener diode ZD generates a reference voltage of 1.25 V in the operating state.
A reference voltage of V is applied to the operational amplifier OP. Assuming that the adjustment terminal ADJ is supplied with the ground potential, the operational amplifier OP generates the reference voltage VREF of 4.2V when receiving the reference voltage of 1.25V. When the adjustment terminal ADJ is open, the operational amplifier OP is
Receiving 1.25V reference voltage, 4.1V reference voltage V
Generate REF.

Lithium ion batteries can be classified into graphite type lithium ion batteries and coke type lithium ion batteries. Graphite type lithium ion batteries have a full charge voltage of 4.2 V, and coke type lithium ion batteries are It has a full charge voltage of 4.1V. Adjustment terminal AD
Both a graphite-based lithium-ion battery and a coke-based lithium-ion battery can be supported depending on whether or not J is given a ground potential.

The charge control circuit 15 further includes a voltage divider V
D. The voltage divider VD is sequentially connected between the divider negative polarity terminal, the divider positive polarity terminal, the divider negative polarity terminal and the divider positive polarity terminal, and is connected in series with each other and has a resistance value equal to each other. 1 to Nth resistors R _{1 to} R _N. In the illustrated example, N =
2, the Nth resistor R _N corresponds to the _second resistor R ₂ . The divider negative polarity terminal is connected to the ground and the divider positive polarity terminal is the first positive polarity terminal connection terminal CE.
It is connected to L2. First to Nth resistors R _{1 to} R _N
Of the Mth resistor R _M and the (M + 1) th resistor R _{M + 1}
The connection point with is connected to the second positive terminal connection terminal CEL1. In the illustrated example, since M = 1, as described above, the Mth resistor R _M corresponds to the _first resistor R ₁ and the (M + 1) th resistor R _{M + 1} is the second resistor. Corresponding to the resistor R ₂ . Therefore, the connection point between the _first resistor R ₁ and the second resistor R ₂ is connected to the second positive terminal connecting terminal CEL1. With this structure, the voltage divider VD divides the voltage of the first positive polarity terminal connection terminal CEL2.

The charge control circuit 15 further includes an error amplifier E
Have A. The error amplifier EA measures the voltage across the first resistor R ₁ (which is equal to the current voltage of one of the secondary batteries 13 of the battery pack 11 or 12 associated with the charging circuit 10). The first voltage is compared with the reference voltage VREF.
Resistor when the voltage is smaller than the reference voltage VREF across the R ₁ supplies a voltage of the logic "0" to the circuit output terminal EXT, first resistor reference voltage across R ₁ is a voltage V
When it is REF or more, the logic "1" is given to the circuit output terminal EXT.
Supply the voltage of.

The charge control circuit 15 further has a negative polarity terminal connection terminal CS. This negative polarity terminal connection terminal CS
Is connected to the first negative terminal -B of the first battery pack 11 when the charging circuit 10 is used in combination with the first battery pack 11 (in the case of FIG. 1). 1
When 0 is used in combination with the second battery pack 12 (in the case of FIG. 2), it is connected to the second negative terminal -B of the second battery pack 12. The negative terminal connecting terminal CS is connected to the ground G via the current detecting resistor RD.
It is connected to ND.

The charge control circuit 15 further includes a current limiting amplifier LA connected to the negative terminal connection terminal CS.
This current limiting amplifier LA has this negative terminal connecting terminal C
When the current flowing through S is equal to or higher than a predetermined current value, the voltage of the logic "1" is supplied to the circuit output terminal EXT, and when the current flowing through the negative polarity terminal connecting terminal CS is smaller than the predetermined current value, the logic The voltage of "0" is supplied to the circuit output terminal EXT. Specifically, the current limiting amplifier LA compares the voltage of the negative terminal connection terminal CS with a reference voltage of 100 mV obtained by dividing the reference voltage of 1.25 V generated by the band gap Zener diode ZD by the resistance voltage divider 19. When the voltage of the negative polarity terminal connection terminal CS is 100 mV or more, the voltage of the logic "1" is supplied to the circuit output terminal EXT, and when the voltage of the negative polarity terminal connection terminal CS is less than 100 mV, the logic "0" is output. The voltage of "the circuit output terminal EXT
To supply. As a result, the negative polarity terminal connection terminal CS is set to 1
Make sure no current of more than 00 mV flows.

With reference to FIG. 4, according to the charging circuit 10 of FIGS. 1 and 2, the constant current charging by the current limiting amplifier LA is followed by the constant voltage charging by the error amplifier EA.

As shown in FIG. 2, the charging circuit 10 has a second
When used in combination with the battery pack 12, the switch output terminal (drain) D of the charging switch (P-channel FET) 14 serves as a charging force, and the second positive terminal connecting terminal CEL1 serves as a charging sense. Become.

Referring to FIG. 5, a charging circuit 10 'according to a second embodiment of the present invention is similar to the charging circuit 10 shown in FIGS. 1 and 2 except as follows. That is, when the charging circuit 10 'is used in combination with the second battery pack 12, the first positive polarity terminal connecting terminal CEL2 also charges the second positive polarity terminal + B of the second battery pack 12. The switch output terminal D of the switch (P-channel FET) 14 is not connected and is opened. This charging circuit 10 'also operates similarly to the charging circuit 10 of FIG.

Referring to FIGS. 6 and 7, the third aspect of the present invention is described.
The charging circuit 20 according to this embodiment is similar to the charging circuit 10 shown in FIGS. 1 and 2 except for the following. That is,
The charging circuit 20 is used in combination with either the first battery pack 21 (FIG. 6) or the second battery pack 22 (FIG. 7).

In FIG. 6, the second battery pack 21 is
It has a first positive polarity terminal + B, a first negative polarity terminal -B, and a first battery unit. The first battery unit has N (N is an integer of 2 or more) secondary batteries 13 connected in series with each other. In the example shown, N is 3. In FIG. 7, the second battery pack 22 has a second positive terminal + B, a second negative terminal -B, and a second battery unit. The second battery unit has M (M is an integer of 1 or more smaller than N) number of secondary batteries 13 connected in series with each other. In the example shown, M is 2
It is. In FIG. 6 and FIG. 7, the N (= 3) secondary batteries 13 and the M (= 2) secondary batteries 13 have the same full charge voltage in a fully charged state. The full charge voltage is 4.2V, for example.

In FIG. 6, N (= 3) secondary batteries 1
3 shows that the first positive terminal + B has a full charge voltage N with respect to the first negative terminal -B in a fully charged state.
The first positive terminal + B so that the voltage is (= 3) times as high.
And the first negative terminal-B. In FIG. 7, in each of the M (= 2) secondary batteries, the second positive terminal + B has a full charge voltage of M (=) with respect to the second negative terminal -B in a fully charged state. 2) The second positive terminal + B and the second negative terminal -B so that the voltage is doubled.
It is connected to the.

In FIG. 6, the charging circuit 20 has a first positive terminal + B and a first negative terminal − when the charging circuit 20 is used in combination with the first battery pack 21.
This is for charging the N (= 3) secondary batteries 13 so that the battery B has a voltage N (= 3) times the full charge voltage. In FIG. 7, the charging circuit 20 is the charging circuit 2
When 0 is used in combination with the second battery pack 22, the second positive terminal + B has a voltage M (= 2) times the full charge voltage with respect to the second negative terminal -B. To M
This is for charging (= 2) secondary batteries 13.

The charge control circuit 15 includes a first positive terminal connecting terminal CEL3 and a second positive terminal connecting terminal CEL2.
With. The first positive polarity terminal connection terminal CEL3 has a first positive polarity of the first battery pack 21 when the charging circuit 20 is used in combination with the first battery pack 21 (in the case of FIG. 6). The charging circuit 20 is connected to the terminal + B and the switch output terminal D, and the charging circuit 20 is connected to the second battery pack 2
When used in combination with 2 (in the case of FIG. 7), it is connected to the second positive terminal + B of the second battery pack 22 and the switch output terminal D. The second positive polarity terminal connection terminal CEL2 has the second positive polarity of the second battery pack 22 only when the charging circuit 20 is used in combination with the second battery pack 22 (in the case of FIG. 7). Connected to terminal + B.

The charge control circuit 15 further includes a voltage divider V
D. The voltage divider VD is sequentially connected between the divider negative polarity terminal, the divider positive polarity terminal, the divider negative polarity terminal and the divider positive polarity terminal, and is connected in series with each other and has a resistance value equal to each other. 1 to Nth resistors R _{1 to} R _N. In the illustrated example, N =
3, the Nth resistor R _N corresponds to the _third resistor R ₃ . The divider negative polarity terminal is connected to the ground and the divider positive polarity terminal is the first positive polarity terminal connection terminal CE.
Connected to L3. First to Nth resistors R _{1 to} R _N
Of the Mth resistor R _M and the (M + 1) th resistor R _{M + 1}
The connection point with is connected to the second positive terminal connection terminal CEL2. In the illustrated example, since M = 2, as described above, the Mth resistor R _M corresponds to the _second resistor R ₂ , and the (M + 1) th resistor R _{M + 1} is the third resistor. Corresponding to the resistor R ₃ of. Therefore, the connection point between the second resistor R ₂ and the third resistor R ₃ is connected to the second positive terminal connecting terminal CEL2. With this structure, the voltage divider VD divides the voltage of the first positive polarity terminal connection terminal CEL3.

The charge control circuit 15 further includes an error amplifier E
Have A. The error amplifier EA measures the voltage across the first resistor R ₁ (which is equal to the current voltage of one of the secondary batteries 13 of the battery pack 21 or 22 associated with the charging circuit 20). The reference voltage VREF (= 4.2V)
When the voltage across the first resistor R ₁ is smaller than the reference voltage VREF (= 4.2V), the circuit output terminal E
The voltage of the logic "0" is supplied to XT, and the first resistor R
_When the voltage between both ends of ₁ is equal to or higher than the reference voltage VREF (= 4.2V), the voltage of the logic "1" is supplied to the circuit output terminal EXT.

As shown in FIG. 3, each of the secondary batteries 13 has a predetermined voltage of 3.0 V or less which is lower than the full charge voltage of 4.2 V in the over-discharged state.

In FIGS. 6 and 7, the charge control circuit 15
Further includes a low voltage detection comparator LVD and an inverter 30.
It has a low voltage detection circuit including. This low-voltage detection circuit includes a first resistor R in the low-voltage detection comparator LVD.
_When it is detected that the voltage between both ends of ₁ is equal to or less than the predetermined voltage of 3.0 V, the inverter 30 outputs the voltage of the logic "1" and outputs the voltage of the logic "1" to the circuit output terminal EX.
When the voltage across the first resistor R ₁ in the low voltage detection comparator LVD is larger than the predetermined voltage 3.0V, the voltage of the logic "0" is output and the logic "0" is supplied to the low voltage detection comparator LVD. Is supplied to the circuit output terminal EXT.

The illustrated low-voltage detecting comparator LVD divides the reference voltage of 1.25 V generated by the bandgap Zener diode ZD and the voltage across the first resistor R ₁ at a predetermined resistance ratio. It is configured to perform substantially the same operation as described above by comparing the above-mentioned voltage value. In the figure, LV is a low-voltage detection comparator LV.
The output of D is shown.

6 and 7, the charge control circuit 15
Further has a low current supply circuit including a resistor 31 and a switch 32. The switch 32 of this low current supply circuit is
The inverter 30 of the low-voltage detection circuit has the logic "1".
Is turned on only while the voltage of
The DC power supply voltage V.sub.C is supplied to the first positive terminal connection terminal CEL3 as a low current in the resistor 31. The low current supplied by the low current supply circuit is lower than the current flowing through the charge switch 14 when the charge switch 14 is turned on. By thus passing through the resistor 31, charging can be performed with a low current determined by (DC power supply voltage VCC of the circuit input terminal IN-voltage of the first positive polarity terminal connection terminal CEL3) / (resistance value of the resistor 31). Become.

Referring to FIG. 4, according to the charging circuit 20 of FIGS. 6 and 7, when the first or second battery pack 21 or 22 includes an overdischarged secondary battery, first, ,
A low current supply circuit including a resistor 31 and a switch 32 charges the over-discharged battery with a low current of, for example, several mA. As a result, if the voltage of one of the secondary batteries 13 rises to a predetermined range (2.8 V to 3.0 V), the charging switch 14 under the control of the current limiting amplifier LA, for example,
It automatically shifts to constant current charging with a large current of several hundred mA. This utilizes the fact that when the battery capacity decreases and the secondary battery is over-discharged, the battery capacity increases when the secondary battery is charged with a low current, and the battery voltage rapidly increases. When an abnormality such as a short circuit occurs in the secondary battery and the secondary battery is over-discharged, the battery capacity does not increase even if this secondary battery is charged with a low current, and the battery voltage increases rapidly. There is nothing to do. Following such constant current charging, constant voltage charging is performed by the charging switch 14 under the control of the error amplifier EA. In this way, charging by low current charging raises the battery voltage of the secondary battery, and at that time constant current charging by large current is performed, the secondary battery is over-discharged due to the decrease in battery capacity. The built-in battery pack can be charged safely.

The charging circuit 20 shown in FIG. 6 can be used exclusively for charging the first battery pack 21. In this case, the second positive terminal connecting terminal CEL2 becomes unnecessary.

[0041]

As described above, the charging circuit according to the present invention can be shared by a plurality of different types of battery packs, so that the economical effect is extremely large.

Furthermore, in the charging circuit according to the present invention, charging is performed by low current charging to increase the battery voltage of the secondary battery, and at that time constant current charging is performed by a large current, so that the battery capacity is reduced. You can safely charge the battery pack that contains the overcharged secondary battery.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a charging circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a charging circuit according to a first embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of the charging circuit according to the present invention.

FIG. 4 is a diagram for explaining the operation of the charging circuit according to the present invention.

FIG. 5 is a diagram illustrating a charging circuit according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a charging circuit according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a charging circuit according to a third embodiment of the present invention.

[Explanation of symbols]

 10, 10 ', 20 Charging circuit 11, 21 First battery pack 12, 22 Second battery pack 13 Secondary battery 14 Charging switch 15 Charging control circuit 16 Reference voltage circuit VD Voltage divider EA Error amplifier LA Current limiting amplifier LVD Low voltage comparator 30 Inverter 31 Resistor 32 Switch

Claims (6)

[Claims] 1. A first battery pack (11 in FIG. 1 or 21 in FIG. 6) having a first positive terminal, a first negative terminal, and a first battery unit; Charging circuit used in combination with either a second battery pack (12 in FIG. 2 or 22 in FIG. 7) having a positive terminal, a second negative terminal, and a second battery unit. (10 in FIGS. 1 and 2 or 20 in FIGS. 6 and 7), wherein the first battery units are connected in series with each other.
(N is an integer of 2 or more) number of secondary batteries (13 in FIG. 1 or 13 in FIG. 6), and the second battery units are M connected in series (M is smaller than N 1 An integer greater than or equal to)
2 secondary batteries (13 in FIG. 2 or 13 in FIG. 7), the N secondary batteries and the M secondary batteries are equal to each other in a fully charged state. The N secondary batteries are arranged such that the first positive polarity terminal has a voltage N times the full charge voltage with respect to the first negative polarity terminal in a fully charged state. Are connected to the first positive polarity terminal and the first negative polarity terminal, and the M secondary batteries have the second positive polarity terminal in the fully charged state. So that it has a voltage M times the full charge voltage with respect to the negative terminal of 2.
The charging circuit is connected to the second positive terminal and the second negative terminal, and the charging circuit has the first positive polarity when the charging circuit is used in combination with the first battery pack. Charging the N secondary batteries so that the terminals have a voltage N times the full charge voltage with respect to the first negative terminal, and the charging circuit is combined with the second battery pack. Charging the M secondary batteries so that the second positive terminal has a voltage M times the full charge voltage with respect to the second negative terminal when used. The charging circuit has a charging switch (14) and a charging control circuit (15), and the charging switch has a positive DC power supply voltage (VCC).
When the charging circuit is used in combination with the switch input terminal (S) to which is applied, the charging circuit is connected to the first positive terminal of the first battery pack, and the charging circuit is connected to the first positive terminal. . A switch output terminal (D) connected to the second positive terminal of the second battery pack when the circuit is used in combination with the second battery pack.
And a switch control terminal (G), which is turned on when a voltage of logical "0" is applied to the switch control terminal, and permits the DC power supply voltage of the switch input terminal to be sent to the switch output terminal. The switch control terminal is turned off when a voltage of logic “1” is applied to prohibit sending of the DC power supply voltage of the switch input terminal to the switch output terminal. Circuit input terminal (I
N), a circuit output terminal (EXT) connected to the switch control terminal, and the first positive electrode of the first battery pack when the charging circuit is used in combination with the first battery pack. And a switch output terminal, and is connected to the second positive terminal of the second battery pack when the charging circuit is used in combination with the second battery pack. And a first positive terminal connecting terminal connected to the switch output terminal (CEL2 in FIGS. 1 and 2 or CEL2 in FIGS. 6 and 7).
3), and when the charging circuit is used in combination with the second battery pack, the second battery pack of the second battery pack is used.
Second positive terminal connecting terminal (CEL1 in FIGS. 1 and 2 or CEL in FIGS. 6 and 7) connected to the positive terminal of
2) and the charge control circuit is connected to the circuit input terminal, and the DC power supply voltage is equal to a reference voltage (V
REF), a reference voltage circuit (16), a divider negative polarity terminal, a divider positive polarity terminal, the divider negative polarity terminal, and the divider positive polarity terminal, which are sequentially connected to each other and are connected in series and are mutually 1 to N resistors having the same resistance value (R _{1 to} R _{2 in} FIGS. 1 and ₂ or R _{1 to} R _{3 in} FIGS. 6 and 7), and the negative terminal of the divider is ground. And the divider positive terminal is connected to the first positive terminal connecting terminal, and the first to N-th terminals are connected.
Mth resistor (R _{1 in} FIGS. 1 and 2 or R _{2 in} FIGS. 6 and 7) and (M + 1) th resistor (R _{2 in} FIGS. 1 and ₂ or 6) And a voltage divider (VD) whose connection point to R ₃ ) in FIG. 7 is connected to the second positive terminal connecting terminal and divides the voltage of the first positive terminal connecting terminal.
Comparing the voltage across the first resistor equal to the current voltage of one of the secondary batteries of the battery pack associated with the charging circuit with the reference voltage,
When the voltage across the resistor is lower than the reference voltage, the logic "0" voltage is supplied to the circuit output terminal, and when the voltage across the first resistor is equal to or higher than the reference voltage. Has an error amplifier (EA) for supplying the voltage of the logic "1" to the circuit output terminal. 2. The charging control circuit is further connected to the first negative terminal of the first battery pack when the charging circuit is used in combination with the first battery pack, When the charging circuit is used in combination with the second battery pack, the negative terminal connecting terminal (C) is connected to the second negative terminal of the second battery pack.
S), and this negative polarity terminal connection terminal is connected to the ground via a current detection resistor (RD), and the charge control circuit is further connected to the negative polarity terminal connection terminal. When the current flowing through the negative polarity terminal connecting terminal is equal to or greater than a predetermined current value, the voltage of the logic “1” is supplied to the circuit output terminal, and the current flowing through the negative polarity terminal connecting terminal is the predetermined current. When it is smaller than the value, a current limiting amplifier (L) that supplies the voltage of the logical "0" to the circuit output terminal
The charging circuit according to claim 1, further comprising A). 3. Each of the N secondary batteries and the M secondary batteries has a voltage equal to or lower than a predetermined voltage lower than the full charge voltage in an overdischarged state, and the charge control circuit includes: Further, when it is detected that the voltage across the first resistor is equal to or lower than the predetermined voltage, the voltage of the logic "1" is output, and the voltage of the logic "1" is output to the circuit output terminal. When the voltage across the first resistor is higher than the predetermined voltage, the voltage of the logic "0" is output, and the voltage of the logic "0" is supplied to the circuit output terminal. Circuit (LVD and 3 in FIGS. 6 and 7)
0) and the DC voltage of the circuit input terminal is supplied to the first positive terminal connecting terminal as a low current only while the low voltage detecting circuit outputs the voltage of the logic "1". Low current supply circuit (31 and 32 in FIGS. 6 and 7)
3. The charging circuit according to claim 2, wherein the low current is lower than a current flowing through the charging switch when the charging switch is turned on. 4. A first battery pack (11 in FIG. 1) having a first positive terminal, a first negative terminal, and a first battery unit; and a second positive terminal. A charging circuit (10 ') used in combination with either a second battery pack (12 in FIG. 5) having a second negative terminal and a second battery unit, the charging circuit comprising: No. 1 battery units are connected in series with each other.
(N is an integer of 2 or more) number of secondary batteries (13 in FIG. 1), and the second battery units are M (M is an integer of 1 or more smaller than N) connected in series with each other. 5 secondary battery (13 in FIG. 5), the N secondary batteries and the M
The plurality of secondary batteries have the same full-charge voltage in a fully charged state, and the N secondary batteries have the first positive terminal in the fully charged state. The first positive terminal and the first negative terminal so as to have a voltage N times the full charge voltage with respect to one negative terminal.
Of the M secondary batteries, the second positive terminal is connected to the second negative terminal of the full charge voltage in a fully charged state. It is connected to the second positive terminal and the second negative terminal so as to have a voltage of M times, and the charging circuit is used by combining the charging circuit with the first battery pack. And charging the N secondary batteries so that the first positive terminal has a voltage N times the full charge voltage with respect to the first negative terminal. When the second secondary battery pack is used in combination with the second secondary battery pack, the second positive terminal has a voltage M times the full charge voltage with respect to the second negative terminal. For charging a battery, wherein the charging circuit comprises a charging switch (14) , And a charge control circuit (15), the charge switch, the positive polarity of the DC power source voltage (VCC)
When the charging circuit is used in combination with the switch input terminal (S) to which is applied, the charging circuit is connected to the first positive terminal of the first battery pack, and the charging circuit is connected to the first positive terminal. When a circuit is used in combination with the second battery pack, the second battery pack of the second battery pack is used.
A switch output terminal (D) connected to the positive terminal of
A switch control terminal (G), which is turned on when a voltage of logic "0" is applied to the switch control terminal, permits the sending of the DC power supply voltage of the switch input terminal to the switch output terminal, and The control terminal is turned off when a voltage of logic "1" is applied to prohibit sending of the DC power supply voltage of the switch input terminal to the switch output terminal, and the charging control circuit is connected to the switch input terminal. A circuit input terminal (I
N), a circuit output terminal (EXT) connected to the switch control terminal, and the first positive electrode of the first battery pack when the charging circuit is used in combination with the first battery pack. A first positive terminal connecting terminal (CEL2 in FIGS. 1 and 5) connected to the battery terminal and the switch output terminal, and the charging circuit is used in combination with the second battery pack. And a second positive terminal connecting terminal (CEL1 in FIGS. 1 and 5) connected to the second positive terminal of the second battery pack and connected to the switch output terminal, The charge control circuit is connected to the circuit input terminal and sets the DC power supply voltage to a reference voltage (V) equal to the full charge voltage.
REF), a reference voltage circuit (16), a divider negative polarity terminal, a divider positive polarity terminal, the divider negative polarity terminal, and the divider positive polarity terminal, which are sequentially connected to each other and are connected in series with each other. The first to Nth resistors (R _{1 to} R _{2 in} FIGS. 1 and 5) having the same resistance value are provided, the negative terminal of the divider is connected to the ground, and the positive terminal of the divider is The Mth resistor (R _{1 in} FIGS. 1 and 5) of the _{first to} Nth resistors and the (M + 1) th resistor (which are connected to the first positive polarity terminal connection terminal). Figure 1
And a voltage divider (VD) whose connection point to R ₂ ) in FIG. 5 is connected to the second positive polarity terminal connection terminal to divide the voltage of the first positive polarity terminal connection terminal, and the charging circuit. Comparing the voltage across the first resistor equal to the current voltage of one of the secondary batteries of the battery pack combined with the reference voltage, across the first resistor. Is supplied to the circuit output terminal when the voltage is lower than the reference voltage, and is supplied to the circuit output terminal when the voltage across the first resistor is equal to or higher than the reference voltage. A charging circuit having an error amplifier (EA) for supplying the voltage of the logic "1". 5. The charge control circuit is further connected to the first negative terminal of the first battery pack when the charge circuit is used in combination with the first battery pack, When the charging circuit is used in combination with the second battery pack, the negative terminal connecting terminal (C) is connected to the second negative terminal of the second battery pack.
S), and this negative polarity terminal connection terminal is connected to the ground via a current detection resistor (RD), and the charge control circuit is further connected to the negative polarity terminal connection terminal. When the current flowing through the negative polarity terminal connecting terminal is equal to or greater than a predetermined current value, the voltage of the logic “1” is supplied to the circuit output terminal, and the current flowing through the negative polarity terminal connecting terminal is the predetermined current. When the value is smaller than the value, a current limiting amplifier (L
The charging circuit according to claim 4, further comprising A). 6. A charging circuit (20 in FIG. 6) used in combination with a battery pack (21 in FIG. 6) having a positive terminal, a negative terminal and a battery unit, the battery unit comprising: Has N (N is an integer of 2 or more) secondary batteries (13 in FIG. 6) connected in series with each other, and the N secondary batteries are mutually charged in a fully charged state. The N secondary batteries have equal full-charge voltages, and the positive terminals have a voltage N times the full-charge voltage with respect to the negative terminals in a fully charged state. The charging circuit is connected to the positive polarity terminal and the negative polarity terminal, and the charging circuit is configured so that the positive polarity terminal has a voltage N times the full charge voltage with respect to the negative polarity terminal. It is for charging the secondary battery, and the charging circuit is a charging switch. Switch (14) and a charge control circuit (15), wherein the charge switch has a positive DC power supply voltage (VCC).
Has a switch input terminal (S), a switch output terminal (D) connected to the positive terminal of the battery pack, and a switch control terminal (G), and the switch control terminal has a logic “0”. When a voltage of "1" is applied, the switch is turned on, the sending of the DC power supply voltage from the switch input terminal to the switch output terminal is permitted, and when a voltage of logic "1" is applied to the switch control terminal, the switch input terminal is turned off. The charging control circuit is connected to the switch input terminal, and the DC input voltage is applied to the circuit input terminal (I) to which the DC power supply voltage is applied.
N), a circuit output terminal (EXT) connected to the switch control terminal, and a positive terminal connection terminal (CEL3 in FIG. 6) connected to the positive terminal and the switch output terminal. The charging control circuit is connected to the circuit input terminal, and the DC power supply voltage is a reference voltage (V) equal to the full charge voltage.
REF), a reference voltage circuit (16), a divider negative polarity terminal, a divider positive polarity terminal, the divider negative polarity terminal, and the divider positive polarity terminal, which are sequentially connected to each other and are connected in series with each other. The first to Nth resistors (R _{1 to} R _{3 in} FIG. 6) having equal resistance values are provided, the negative terminal of the divider is connected to the ground, and the positive terminal of the divider is the positive terminal. A voltage divider (VD) connected to the terminal connection terminal and dividing the voltage of the positive terminal connection terminal, and the first resistor equal to the current voltage of one of the secondary batteries of the battery pack. The voltage across the first resistor is compared to the reference voltage, and when the voltage across the first resistor is less than the reference voltage, the logic "0" is output to the circuit output terminal.
And an error amplifier (EA) that supplies the voltage of the logic "1" to the circuit output terminal when the voltage across the first resistor is equal to or higher than the reference voltage. The charge control circuit further has a negative terminal connection terminal (CS) connected to the negative terminal, and the negative terminal connection terminal is connected to the ground via a current detection resistor (RD). The charge control circuit is further connected to the negative polarity terminal connection terminal, and when the current flowing through the negative polarity terminal connection terminal is equal to or more than a predetermined current value, the voltage of the logic “1” is applied. When the current supplied to the circuit output terminal and flowing through the negative polarity terminal connection terminal is smaller than the predetermined current value, the current limiting amplifier (L) that supplies the voltage of the logic "0" to the circuit output terminal.
A), each of the N secondary batteries has a voltage equal to or lower than a predetermined voltage lower than the full-charge voltage in an overdischarged state, and the charge control circuit further includes: When it is detected that the voltage across the resistor is equal to or lower than the predetermined voltage, the logic "1" voltage is output, and the logic "1" voltage is supplied to the circuit output terminal. When the voltage between both ends of the resistor is larger than the predetermined voltage, the voltage of the logic "0" is output, and the low voltage detection circuit (LVD and LVD in FIG. 6) which supplies the voltage of the logic "0" to the circuit output terminal. 30),
A low current supply circuit that supplies the DC power supply voltage of the circuit input terminal as a low current to the positive terminal connection terminal only while the low voltage detection circuit outputs the voltage of the logic "1" (FIG. 6). 31 and 32), and the low current is lower than the current flowing through the charging switch when the charging switch is turned on.