JPH07163060A - Series battery over-discharge prevention circuit, over-charge prevention circuit and charge / discharge control circuit - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a charge / discharge circuit in which none of the batteries are over-discharged or over-charged even if there is capacity variation between the batteries connected in series. [Structure] The over-discharge prevention circuit is connected in series to each of the batteries B1, B2 and B3, and turns on the discharge current path of each battery.
It includes a switching element Q1 that is turned off, a diode D1 that forms a bypass path for a discharge current, and a voltage detector 1 that turns on and off the corresponding switching element when the terminal voltage of each battery is equal to or higher than a set value. The overcharge prevention circuit
A diode D2 that is connected in series to each of the batteries B1, B2 and B3 and forms a charging current path for each battery, a switching element Q3 that forms a bypass path for the charging current, and a terminal voltage of each battery is less than or equal to a set value, or more. The voltage detector 6 turns off and turns on the corresponding switching element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overdischarge prevention circuit, an overcharge prevention circuit, and a charge / discharge control circuit for protecting a battery group connected in series from overdischarge or overcharge.

[0002]

2. Description of the Related Art As a series battery over-discharge prevention circuit and over-charge prevention circuit for lithium secondary batteries,
The one described in JP-A-4-331425 is typical. In this prior art overdischarge prevention circuit, a switching element is inserted in the discharge current path from the series battery to the load, and the series voltage of the battery group is input to the voltage detector. Then, when the series voltage of the battery group falls below the set value during discharging to the load, the switching element is turned off by the detection signal from the voltage detector, and the discharge current path from the battery group to the load is cut off. . Further, in the over-discharge prevention circuit of the prior art, a switching element is inserted in the charging current path from the charging power source to the series battery, and the terminal voltage of each battery connected in series is set to an individual voltage detector. input. And while charging the series battery, one of
When the terminal voltage of even one battery exceeds the set value, the switching element is turned off by the detection signal from the corresponding voltage detector, and the charging path to the battery group is cut off.

[0003]

In the above-mentioned conventional over-discharge prevention circuit, the discharge is stopped when the series voltage of the battery group becomes equal to or lower than the set value, but the capacity variation of the battery groups connected in series is not fixed. When the value is large, it was unavoidable that a certain battery was over-discharged before the discharge was stopped. In other words, if a battery with a smaller charging capacity than others is included, the overall series voltage may exceed the set voltage even if that particular battery reaches an overdischarged state. In this case, over-discharge may occur, and as a worse case, a specific battery may be reversely charged.

In order to solve this problem, the terminal voltage of each battery is monitored in the same manner as the above-mentioned overcharge prevention circuit, and the discharge is stopped when the battery voltage becomes below a set value in any one of them. Can be considered. However, in such a case, although the specific battery is about to be over-discharged, the power supply to the load is stopped despite the sufficient electric capacity remaining in the other batteries. That is, due to some inconvenient batteries, the duration of power supply to the load is significantly shortened.

In the conventional overcharge prevention circuit, if even one battery voltage exceeds the set value, the entire charging is stopped. Therefore, if the battery capacity varies, the charging time is defined by the battery with the smallest charging margin. The battery with ample capacity cannot be fully charged. In order to solve this problem, it is conceivable that the charging is stopped when the series voltage of the battery group reaches a set value as in the overdischarge prevention circuit. However, in such a case, it is likely that a certain battery is overcharged and continues to be charged.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to prevent any battery from being over-discharged even if there is a capacity variation between batteries connected in series. Another object of the present invention is to provide an over-discharge prevention circuit that can supply the entire charging energy to the load without waste. Another object is to prevent each battery from being overcharged even if there is a variation in capacity between batteries connected in series, and to allow each battery to be fully charged. It is to provide an overcharge prevention circuit. Still another object is to provide a charge / discharge control circuit having both the functions of the over-discharge prevention circuit and the over-charge prevention circuit which have excellent performance as described above.

[0007]

The over-discharge prevention circuit of the first invention is connected to a plurality of batteries connected in series, and a plurality of switching elements for turning on / off a discharge current path of each battery. A plurality of diodes that are connected in parallel to each of the series circuits of the battery and the switching element and that form a bypass path for the discharge current from the other battery, and that are attached to each of the batteries and their terminals It is provided with a plurality of voltage detectors that turn on the switching element in series with the corresponding battery when the voltage is equal to or higher than a set value, and turn off the switching element when the terminal voltage is equal to or lower than the set value.

The overcharge prevention circuit of the second invention is connected in series to a plurality of batteries connected in series and forms a charging current path for each battery, and each of the battery and the diode. A plurality of switching elements that are connected in parallel to each of the series circuits and that form a bypass path for charging current to the other battery, and that are attached to each of the batteries, and are applicable when the terminal voltage is less than or equal to a set value. A plurality of voltage detectors that turn off the switching element in parallel with the battery and turn on the switching element when the terminal voltage is equal to or higher than a set value are provided.

The overcharge prevention circuit according to the third aspect of the invention includes a plurality of transistors which are connected in parallel to a plurality of batteries connected in series and which form a bypass path for charging current to the other batteries, and Each battery is provided with a voltage detector that increases the conduction resistance of the transistor in parallel with the corresponding battery as the terminal voltage decreases, and decreases the conduction resistance of the transistor as the terminal voltage increases. is there.

A charge / discharge control circuit according to a fourth aspect of the invention includes both the overdischarge prevention circuit of the first aspect and the overcharge prevention circuit of the second aspect for the same series-connected battery group, and , And an operation control circuit that activates one of the overdischarge prevention circuit and the overcharge prevention circuit in response to an external command signal.

[0011]

In the over-discharge prevention circuit according to the first aspect of the present invention, if the remaining capacity of each battery connected in series is sufficient, all the switching elements in series with each battery are turned on, and all the switching elements of the battery are connected through these. Series current is supplied to the load. Then, when a certain battery reaches immediately before over-discharging, only the switching element associated with that battery is turned off and the discharge of that particular battery is stopped. Since the bypass path is formed, power supply to the load from another battery having a large remaining capacity is continued.

In the overcharge prevention circuit of the second invention,
In a state where the batteries connected in series are not fully charged, the switching elements are all off, so that a charging current flows in series to all the batteries. When a certain battery is fully charged, the switching element associated with the battery is turned on, and the charging current is not supplied to the specific battery, but the switching element that is turned on is fully charged. The other battery continues to be charged because it serves as a bypass path for the charging current to the other battery.

In the overcharge prevention circuit of the third invention,
When the batteries connected in series are not fully charged, the conduction resistance of the transistors is very large, so that a large charging current flows in series to all the batteries. Then, as one battery approaches full charge, the transistor associated with that battery gradually becomes less resistive, gradually reducing the charging current to that particular battery,
Since the reduced amount is bypassed to another battery, a large current is continuously supplied to the other battery to continue charging.

In the charge / discharge control circuit of the fourth invention,
When the load is supplied from the series battery, the overdischarge prevention circuit of the first invention functions, and when the series battery is charged, it functions as the overcharge prevention circuit of the second invention.

[0015]

[Example] [Over-discharge prevention circuit of FIG. 1] Three batteries B1,
A transistor Q1 is inserted in series with each of B2 and B3, and batteries B1, B2,
B3 is connected in series. In addition, each battery B1, B
A diode D1 for a bypass path is connected in parallel to each of the series circuits of B2 and B3 and each transistor Q1. Further, a voltage detector 1 is connected between the terminals of each of the batteries B1, B2, B3, and the output of the voltage detector 1 causes the transistor Q1 in series with the corresponding battery Bi.
Is controlled on / off.

A configuration example of the voltage detector 1 is shown in FIG. This voltage detector 1 has a terminal voltage (Vd-V) of the battery Bi.
s) is used as an operating power supply and also as an input voltage. That is, in the comparator 3 driven by the voltage (Vd-Vs), the value obtained by dividing the voltage (Vd-Vs) by the resistors R1 and R2 is compared with the set voltage Vf set to an appropriate value, When the voltage (Vd-Vs) is equal to or higher than the set voltage Vf, the open collector / output transistor 4 is turned on.

Therefore, when the remaining capacity of each of the batteries B1, B2, B3 is sufficiently large, the terminal voltage of each is higher than the set voltage of the detector 1, and all three transistors Q1 are turned on. In this case, three batteries B1, B2, B
3 are all connected in series to the load 2 via the three transistors Q1, and the series current of the three batteries B1, B2, B3 is supplied to the load 2.

It is assumed that the remaining capacity of one battery B1 becomes dull due to the discharge, and the terminal voltage of the battery B1 becomes equal to or lower than the set voltage of the detector 1. Then, the output of the comparator 1 associated with the battery B1 is inverted and the transistor Q1 associated with the battery B1 is turned off. Therefore, the discharge of the battery B1 is stopped. However, the bypass path by the diode D1 attached to the battery B1 becomes effective, and the output currents from the other two batteries B2 and B3 flow to the load 2 through the diode D1 attached to the battery B1.

Batteries B1 and B connected in series in this way
Voltage monitoring and discharge stop control are performed for each of the batteries 2 and B3, and power supply to the load 2 is continued until all the transistors Q1 associated with the batteries B1, B2, and B3 are turned off. Discharge is stopped in the order of decreasing voltage.

The comparator 3 in the voltage detector 1
An appropriate hysteresis is set for the input / output characteristics of FIG. 2 to prevent unnecessary repetition of on / off of the transistor Q1 (chattering).

[Overcharge prevention circuit of FIG. 3] Three batteries B
Diodes D2 are respectively inserted in series in 1, B2, B3, and batteries B1, B2,
B3 is connected in series. In addition, each battery B1, B
A transistor Q2 for a bypass path is connected in parallel to each series circuit of 2, 2 and each diode D2. Further, a voltage detector 5 is connected between the terminals of each of the batteries B1, B2, B3, and the output of the voltage detector 5 causes the transistor Q2 in parallel with the corresponding battery Bi.
Is controlled on / off. The configuration of the voltage detector 5 is the same as that of FIG. 2 described above, but the set voltage Vf is different from that of the overdischarge prevention circuit of FIG.

A constant current power supply 7 for charging a series circuit of three batteries B1, B2, B3 with three diodes D2 interposed.
Connected to each battery B1, B through the diode D2
2, the charging current flows through B3. At the beginning of charging, the terminal voltage of each battery B1, B2, B3 is equal to or lower than the set voltage of the voltage comparator 5, and the three bypass transistors Q2 are used.
Are all off.

It is assumed that the battery B1 is almost fully charged as charging progresses. In this case, the terminal voltage of the battery B1 becomes equal to or higher than the set voltage of the voltage detector 5, the output of the voltage detector 5 attached to the battery B1 is inverted, and the transistor Q2 attached to the battery B1 is turned on. Therefore, the charging current stops flowing in the battery B1, but the transistor Q associated with the battery B2
The other two batteries B2 and B3 are continuously supplied with the charging current through the battery 2. Since the power supply 7 is a constant current power supply, a constant charging current is supplied regardless of whether the transistor Q2 is on or off.

The batteries B1 and B connected in series in this manner
Voltage monitoring and charge stop control are performed for each of the batteries B and B3, and the charging operation is continued until all the transistors Q2 attached to the batteries B1, B2, and B3 are turned on, and the fully charged state is achieved. Charging is stopped in order from the battery Although not shown, if an LED (light emitting diode) is connected in series with each transistor Q2, it is possible to display whether the individual batteries B1, B2, B3 are being charged or have been charged.

Further, the comparator 3 in the voltage detector 5
An appropriate hysteresis is set for the input / output characteristics (see FIG. 2) so that the transistor Q2 is appropriately turned on / off in the vicinity of full charge to lead to full charge.

[Overcharge Prevention Circuit of FIG. 4] This is a modification of the embodiment of FIG. 3, in which the bypass transistor Q2 in FIG. 3 is replaced with a thyristor Q3, and the voltage detector 5 and the voltage detector 6 are replaced accordingly. Has been changed to. The voltage detector 6 is connected in parallel to the series circuit of the battery Bi and the diode D2, but the set voltage of the internal comparator is set in consideration of the forward drop voltage of the diode D2.
The voltage monitoring function for the battery Bi is the same as that of the embodiment shown in FIG. Of course, the output circuit of the voltage detector 6 is a circuit for driving the gate of the thyristor Q3. The operation of this embodiment is the same as that of the embodiment of FIG.

[Overcharge Prevention Circuit of FIG. 5] This is an analog operation overcharge prevention circuit. Each battery B1, B2, B3
A bypass transistor Q4 and a voltage detector 8 are connected in parallel with each other. The voltage detector 8 is a battery Bi
The lower the terminal voltage of the transistor Q, the more parallel to the battery Bi the transistor Q
4 is increased, and the higher the terminal voltage is, the smaller the conduction resistance of the transistor Q4 is. Therefore, battery B
Most of the charging current from the constant current power source 7 flows through the battery Bi at the initial charging time of i, but as the battery Bi approaches full charge, the bypass current flowing through the transistor Q4 increases, and that much of the charging current of the battery Bi. Charge current decreases. This charging control is performed for each of the batteries B1, B2, B3.

[Charging / Discharging Control Circuit of FIG. 6] This is provided with both the overdischarge prevention circuit of FIG. 1 and the overcharge prevention circuit of FIG. 4 for the same series battery B1, B2, B3, and from the outside. And an operation control circuit for activating one of the overdischarge prevention circuit and the overcharge prevention circuit in response to the command signal.
The main points of the operation control circuit are a switching transistor Qa inserted in series with the power supply terminal Vd of the voltage detector 1 and a switching transistor Qb inserted in series with the power supply terminal Vd of the voltage detector 6. "Discharge" switch 10
When the three transistors Qa are turned on by the drive circuit and the three transistors Qb are turned off by the drive circuit as will be described later, the above-mentioned over-discharge prevention circuit is activated and the three series batteries B1, B2, B3 is connected to load 2. When the switch 10 is switched to the “charging” side and the three transistors Qa are turned off by the drive circuit and the three transistors Qb are turned on, the three series batteries B1, B2, B3 become the charging constant current power source 7. When connected, the above-mentioned overcharge prevention circuit is activated.

FIG. 7 shows an embodiment of a drive circuit for driving the transistors Qa and Qb on / off.
This drive circuit uses the terminal voltage of the battery B3 of the series batteries B1, B2, B3 as a power source, and switches 1 of FIG.
The switches 10a and 10b interlocking with 0 are provided, and the drive signals a1 and a of the transistors Qa are provided at the time of "discharging".
2 and a3 (drive signals b1, b2 and b3 of each transistor Qb are turned off), and drive signals b1, b2 and b3 of each transistor Qb are generated at the time of "charging" (drive signals a1 and a2 of each transistor Qa). , A3
Is off). Of course, in the "stop" state, neither drive signal is off. When the transistor Qa is off, the voltage detector 1 for the overdischarge prevention circuit is immobilized and its power consumption becomes zero. When the transistor Qb is off, the voltage detector 6 for the overcharge protection circuit is immobilized and its power consumption becomes zero. Thus, when not in use, the over-discharge prevention circuit and the over-charge prevention circuit do not consume useless power, and these circuits are
The load of 1, B2, and B3 does not occur.

In the drive circuit shown in FIG. 7, the drive signals a1, a2, a3 of the three transistors Qa are used.
(Drive signals b1, b2, b3 of the transistor Qb)
Need to have an appropriate potential difference. On the other hand, if a photocoupler is used, it is not necessary to consider the potential of each drive signal. That is, the transistor Qa (Qb) may be a phototransistor of a photocoupler, and the phototransistor may be driven to be turned on / off by an optical signal from the LED.

By the way, the over-discharge prevention circuit described above,
The overcharge prevention circuit and the charge / discharge prevention circuit may have some or all of their components integrated in a series battery pack, or some or all of them may be dispersed on the load equipment or charging power source side. May be provided.

[0032]

As described above in detail, in the overdischarge prevention circuit of the first invention, if the remaining capacity of each battery connected in series is sufficient, all the switching elements in series with each battery are It is on, and the series current of all batteries is supplied to the load through them. Then, when a certain battery reaches immediately before over-discharging, only the switching element associated with that battery is turned off and the discharge of that particular battery is stopped. Since the bypass path is formed, power supply to the load from another battery having a large remaining capacity is continued.

In the overcharge prevention circuit of the second invention,
In a state where the batteries connected in series are not fully charged, the switching elements are all off, so that a charging current flows in series to all the batteries. When a certain battery is fully charged, the switching element associated with the battery is turned on, and the charging current is not supplied to the specific battery, but the switching element that is turned on is fully charged. The other battery continues to be charged because it serves as a bypass path for the charging current to the other battery.

In the overcharge prevention circuit of the third invention,
When the batteries connected in series are not fully charged, the conduction resistance of the transistors is very large, so that a large charging current flows in series to all the batteries. Then, as one battery approaches full charge, the transistor associated with that battery gradually becomes less resistive, gradually reducing the charging current to that particular battery,
Since the reduced amount is bypassed to another battery, a large current is continuously supplied to the other battery to continue charging.

In the charge / discharge control circuit of the fourth invention,
When the load is supplied from the series battery, the overdischarge prevention circuit of the first invention functions, and when the series battery is charged, it functions as the overcharge prevention circuit of the second invention.

That is, even if there is a variation in capacity between batteries connected in series, none of the batteries is in an over-discharged state, and the entire charging energy can be supplied to the load without waste. Further, even if there is a capacity variation between the batteries connected in series, none of the batteries is overcharged, and each battery can be fully charged.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an overdischarge prevention circuit.

FIG. 2 is a configuration diagram of an embodiment of a voltage detection circuit.

FIG. 3 is a configuration diagram of an embodiment of an overcharge prevention circuit.

FIG. 4 is a configuration diagram of another embodiment of the overcharge prevention circuit.

FIG. 5 is a configuration diagram of another embodiment of the overcharge prevention circuit.

FIG. 6 is a configuration diagram of an embodiment of a charge / discharge control circuit.

FIG. 7 is a configuration diagram of an embodiment of a drive circuit associated with the above charge / discharge control circuit.

[Explanation of symbols]

 1, 5, 6, 8 Voltage detector 2 Load 7 Constant current power supply for charging B1, BB2, B3 Battery D1 Discharge bypass path diode Q1 Discharge path switching element D2 Charge path diode Q2, Q3 Charge bypass path switching element Q4 Transistor for charging bypass path

Claims (9)

[Claims] 1. A plurality of switching elements each connected in series to a plurality of batteries connected in series to turn on / off a discharge current path of each battery, and each series circuit of the battery and the switching element. And a plurality of diodes that are connected in parallel and form a bypass path for the discharge current from the other battery, and the switching element that is attached to each of the batteries and is in series with the battery when the terminal voltage is equal to or higher than a set value. And a plurality of voltage detectors that turn on the switching element and turn off the switching element when the terminal voltage is less than or equal to a set value. 2. The over-discharge prevention circuit for a series battery according to claim 1, wherein an appropriate hysteresis is set for an input voltage discrimination characteristic of the voltage detector. 3. A plurality of diodes connected in series to a plurality of batteries connected in series to form a charging current path for each battery, and connected in parallel to each series circuit of the battery and the diode. And a plurality of switching elements that form a bypass path for charging current to the other battery, and the switching element that is attached to each of the batteries and turns off the switching element in parallel with the corresponding battery when the terminal voltage is less than or equal to a set value. And a plurality of voltage detectors that turn on the switching element when the terminal voltage is equal to or higher than a set value, and an overcharge prevention circuit for a series battery. 4. The overcharge protection circuit according to claim 3, wherein the charging power source externally applied to the series-connected battery group serves as an operating power source for the voltage detector. Prevention circuit. 5. The overcharge prevention circuit for a series battery according to claim 3, wherein an appropriate hysteresis is set in the input voltage discrimination characteristic of the voltage detector. 6. A plurality of transistors, each of which is connected in parallel to a plurality of batteries connected in series and forms a bypass path for a charging current to another battery, and a terminal attached to each of the batteries and having its terminals. A voltage detector that increases the conduction resistance of the transistor in parallel with the corresponding battery when the voltage is lower, and decreases the conduction resistance of the transistor when the terminal voltage is higher; and Prevention circuit. 7. The method according to claim 1, wherein the same series-connected battery group is used.
An operation comprising both the overdischarge prevention circuit according to claim 3 and the overcharge prevention circuit according to claim 3, and activating one of the overdischarge prevention circuit and the overcharge prevention circuit in response to a command signal from the outside. A series battery charge / discharge control circuit comprising a control circuit. 8. The charge / discharge control circuit according to claim 7, wherein the operation control circuit is not used for the voltage detector in the overdischarge prevention circuit and the voltage detector in the overcharge prevention circuit, respectively. A charging / discharging control circuit for a series battery, comprising a switching circuit for shutting off the operating power source. 9. The series battery according to claim 7, wherein the command signal from the outside is transmitted to the operation control circuit via a photocoupler. Charge and discharge control circuit.