JPH08196042A - Charging and discharging protection unit for secondary battery - Google Patents

Abstract

PURPOSE: To protect an element from deterioration and destruction, by connecting a diode in series with a switch means in a reverse direction against the conduction direction of a parasitic diode in a charging circuit and a discharging circuit. CONSTITUTION: Voltages of secondary batteries 10 and 12 are measured by a control circuit 210 at charging time. When the voltages are in a given value, the voltage is supplied through a terminal 32, a charging path diode 240, and a charging-path breaking switch element 220 to the secondary batteries 10 and 12 during the charging time. When one of batteries 10 and 12 is full charged to an upper level, a drain/source current is stopped to prevent overcharging. The discharging current is carried from a positive terminal of the secondary battery through the charging breaking switch element 230 and a charging path diode 250 to the terminal 32 during discharging. Though the current tends to flow through a parasitic diode 222, the reverse conduction against the charging path diode 240 can be prevented. As a result, a deterioration in performance or destruction of an element is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery charge / discharge protection device for preventing overcharge and overdischarge of a secondary battery,
In particular, the present invention relates to a secondary battery charge / discharge protection device used in, for example, a power supply device detachably mounted in a portable electronic device.

[0002]

2. Description of the Related Art With the miniaturization of various electronic devices such as video camera integrated VTRs (video tape recorders), personal computers, and telephones, many portable electronic devices have been developed. A primary battery or a secondary battery is widely used as a power source for these portable electronic devices. In particular, secondary batteries are widely used in portable electronic devices because they can be used repeatedly.

When such a secondary battery is used as a power supply device, it is necessary to prevent overcharge and overdischarge of the secondary battery. For example, when the secondary battery is in an overcharged state or an overdischarged state, a substance inside the battery is decomposed, resulting in a problem that the battery capacity is reduced. If such overcharging and overdischarging are repeated, the capacity of the battery is reduced at an accelerating rate and the life of the battery is exhausted.

As a preventive measure against these problems, the battery voltage is monitored so that the charging path is shut off when the battery voltage exceeds a predetermined set voltage during charging, and the battery voltage drops below another set voltage during discharging. In this case, a method of cutting off the discharge path is adopted. For example, in Japanese Utility Model Laid-Open No. 02-136445, the battery voltage of each of a plurality of rechargeable batteries connected in series is detected, and the voltage of any one of the rechargeable batteries is above or below a set voltage. In this case, a protection circuit for a rechargeable battery has been proposed, which cuts off the charging path or the discharging path, respectively.

In this case, as means for shutting off the charging path and the discharging path, considering cost and external size,
Switching off by means of semiconductor switches is generally applied to advantage. For example, JP-A-04-33271 and JP-A-04-75430
Japanese Patent Laid-Open Publication No. 04-75431 and the like propose a power supply device for a secondary battery using a field effect transistor including a parasitic diode inside as a switch element.
In particular, the power supply device described in Japanese Patent Laid-Open No. 04-75430 has a first field effect transistor for blocking a charging path and a second field effect transistor for blocking a discharging path on one terminal side of a secondary battery. When connected in series, when the voltage across the battery drops to a first voltage near the chargeable voltage, the first field effect transistor is turned on to open the charging path and rise to a second voltage higher than the first voltage. When the first field effect transistor is turned off to cut off the charging path, and when the battery voltage rises to a third voltage near the dischargeable voltage, the second field effect transistor is turned on to open the discharge path, When the voltage dropped to the fourth voltage lower than the third voltage, the second field effect transistor was turned off to interrupt the discharge path. In this case, at the time of overcharge protection that cuts off the charging path, the first field effect transistor in the off state secures the discharging path by the internal parasitic diode that conducts in the direction opposite to the charging direction. In addition, during over-discharge protection that cuts off the discharge path, the second field effect transistor in the off state secures the charge path by the internal parasitic diode that conducts in the direction opposite to the discharge direction. That is,
Because of its structure, the field effect transistor includes a parasitic diode that causes a current to flow in the opposite direction to the blocking direction, so that only a blocking effect in one direction can be expected. In the above publication, this phenomenon is positively used to secure a path in the opposite direction to the direction in which two field effect transistors are connected in series in the opposite direction in the opposite direction, and the overcharge protection and the overcharge protection of the secondary battery are ensured. It realized discharge protection.

[0006]

However, in the above-mentioned prior art, since the parasitic diodes inside the switch element, which are not originally intended to be used due to their original structure, are utilized to secure the respective charge / discharge paths, There is a drawback that the element itself is likely to be deteriorated, the function as a switch is deteriorated, and the element is easily broken. Therefore, when the switch function is deteriorated, the charging / discharging path cannot be cut off at a desired point in time, and if it is used without knowing it, a problem due to overcharge or overdischarge of the secondary battery as described above is likely to occur. was there.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a more reliable charge / discharge protection device for a secondary battery by preventing deterioration and destruction of elements while maintaining protection operations against overcharge and overdischarge. To aim.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, a secondary battery charge / discharge protection device according to the present invention includes a secondary battery charging / discharging device which prevents overcharge and overdischarge of a rechargeable secondary battery. In the discharge protection device, the first switch means is connected in series to the charging path of the secondary battery and is normally turned on to conduct current in the charging direction and to cut off the path in the charging direction when turned off. First switching means including therein a parasitic diode that conducts in the direction and a discharge path of the secondary battery, which is connected in series and is normally turned on to conduct current in the discharge direction and cut off the path in the discharge direction when turned off. The second switch means is a second switch means that internally includes a parasitic diode that conducts in the charging direction when turned off, and the battery voltage of the secondary battery is detected to make the battery voltage equal to or higher than the first set voltage. If Control means for turning off the first switch means and turning off the second switch means when the battery voltage becomes equal to or lower than the second set voltage, and the charging path and the discharging path are secondary batteries. A first diode, which is connected in parallel with one of the input / output terminals, is connected in series to the charging path with a first switch device in a direction opposite to the conduction direction of the parasitic diode of the first switch means, and has a discharge path with a first diode. The second switch means is connected in series with a second diode in a direction opposite to the conduction direction of the parasitic diode.

In this case, a plurality of secondary batteries are connected in series, and the control means monitors the battery voltage of each secondary battery, and any one of the voltage values becomes equal to or higher than the first set voltage. It is preferable to turn off the first switch means at the time of, and turn off the second switch means when any one of the voltage values becomes equal to or lower than the second set voltage. Further, the secondary battery has a plurality of batteries connected in series, and the control means monitors the voltage between both ends of the batteries connected in series to control the first switch means and the second switch means. May be.
On the other hand, the secondary battery may be used alone, and the control circuit may detect the voltage across the single secondary battery to control the first switch means and the second switch means.

Further, both the charging path in which the first switch means and the first diode are arranged and the discharging path in which the second switch means and the second diode are arranged are both positive with respect to the secondary battery. Alternatively, it may be arranged in parallel on either one of the negative paths.

[0011]

According to the secondary battery charge / discharge protection device of the present invention, when the secondary battery voltage does not reach the first set voltage during charging, the first normally-on A charging current from a charger or the like is supplied to the secondary battery via the switch means and the first diode. When the control means detects that the battery voltage of the secondary battery has become equal to or higher than the first set voltage as the charging progresses, the first switch means is turned off to cut off the charging path and overcharge the secondary battery. Prevent. At this time, the current in the discharging direction from the secondary battery is connected in series to the second switch means which is turned on and this without passing through the parasitic diode of the first switch means which is turned off. It bypasses the second diode and flows to the outside. Further, at the time of discharging, if the voltage of the secondary battery has not reached the second set voltage, the secondary battery is supplied to the load via the second switch means and the second diode which are normally turned on. When the control means detects that the battery voltage of the secondary battery has become equal to or lower than the second set voltage due to the progress of discharge, the second switch means is turned off to interrupt the discharge path to over-discharge the secondary battery. Prevent. At this time, the current in the charging direction to the secondary battery does not pass through the parasitic diode of the second switch means, and the first switch means turned on and the first diode connected in series to the first switch means. Is bypassed and supplied to the battery.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a secondary battery charge / discharge protection device according to the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment in which the charge / discharge protection device according to the present invention is applied to a secondary battery power supply device 30. The secondary battery power supply device 30 in the present embodiment includes two secondary batteries 10,1.
A power source formed as a so-called battery pack 30 in which the positive terminal 32 and the negative terminal 34 are provided to the outside by connecting the two in series and via the charge / discharge protection device 20 that prevents overcharging and overdischarging. The device is, for example, a power supply device that is detachably mounted in a portable video camera integrated VTR.

Specifically, the secondary battery 10, 1 in this embodiment is
2 is, for example, a nickel-cadmium (Ni-Cd) battery,
Nickel-metal hydride (Ni-H) batteries, preferably lithium-ion (L
i ⁺ ) Rechargeable batteries such as secondary batteries are used. For example, a lithium-ion secondary battery has an operating voltage range of 2.5 to 4.2 V per cell, and when the terminal voltage exceeds about 4.3 V due to charging, it causes a larger deterioration in performance than normal cycle deterioration. Further, when the terminal voltage of the battery becomes about 2.4 V or less due to discharge, it causes a larger deterioration in performance than normal cycle deterioration. In particular, when the characteristics of the batteries vary, a battery that is fully charged or emptied first is likely to be overcharged or over-discharged before the other battery. Therefore, the charge / discharge protection device of the present embodiment
When the secondary batteries 10 and 12 are lithium-ion batteries, for example, 20 detects the terminal voltage of each battery 10 and 12,
To prevent the voltage of either one of the batteries 10 and 12 from exceeding 4.3V and below 2.4V, shut off the charge and discharge paths respectively and prevent overcharging and overdischarging of the respective batteries 10 and 12. To prevent.

Specifically, the charge / discharge protection device 20 of this embodiment
Is a control circuit 210 and a switching device 220 for blocking the charging path.
A discharge path cutoff switching element 230, a charge path diode 240, and a discharge path diode 250. The control circuit 210 is a switch control circuit that detects the terminal voltages of the secondary batteries 10 and 12 and controls the switch elements 220 and 230 based on the detection results. The control circuit 210 includes, for example, a first battery voltage detection circuit 300, a second battery voltage detection circuit 302, a
Of the comparison circuit 304, the second comparison circuit 306, the first OR circuit 308, the second OR circuit 310, the first switch drive circuit 312, and the second switch drive circuit 314. ing. The first battery voltage detection circuit 300 includes a first secondary battery 10
Of the first comparison circuit 304 connected to the positive terminal and the negative terminal of
Is a detection circuit to be supplied to. Similarly, the second battery voltage detection circuit 302 is connected to the positive terminal and the negative terminal of the second secondary battery 12 and supplies the detected voltage corresponding to the potential difference to the second comparison circuit 306. Advantageously, as shown in FIG. 1, the potential from the negative terminal of the first secondary battery 10 and the potential from the positive terminal of the second secondary battery 12 are common to the first voltage detection circuit 300 and The voltage is supplied to the second voltage detection circuit 302, and the detection circuits 300 and 302 are respectively referenced with reference to this.
Detects the potential difference from the other terminal voltage.

The first comparison circuit 304 is a one-input / two-output comparator for detecting whether or not the voltage value from the first voltage detection circuit 300 is equal to or higher than the first set voltage or lower than the second set voltage. It is a comparison circuit formed by. First
The set voltage of is near the upper limit of the operating voltage of each secondary battery 10, 12, for example, in the above-mentioned lithium ion battery.
It is set to a voltage value of 4.2 to 4.3V below 4.3V. The second set voltage is 2.4 to 2.5V, which exceeds 2.4V in the vicinity of the lower limit of the operating voltage, for example, in the case of the lithium ion battery.
Is set to the voltage of. Similarly, the second comparison circuit 306
Is a comparison circuit formed by a one-input / two-output comparator that detects whether or not the voltage value from the second voltage detection circuit 302 is equal to or higher than the first set voltage or equal to or lower than the second set voltage. is there. The outputs of the comparison circuits 304 and 306 are supplied to the first OR circuit 308 with the detection result as to whether or not the voltage is equal to or higher than the first set voltage, and the detection result as to whether or not the voltage is equal to or lower than the second set voltage is output to the second OR circuit. Supply to 310.

The first OR circuit 308 includes a first comparison circuit 304.
And a detection result from the second comparison circuit 306, which is a logical circuit, and outputs an effective output to the first switch when one of the detection outputs detects a voltage value equal to or higher than the first set voltage. Supply to the drive circuit 312. Similarly, the second OR circuit 310 includes a first comparison circuit 304 and a first comparison circuit 30.
A logical circuit that takes the logical sum of the outputs of the results of detecting the voltage value equal to or lower than the second set voltage at 6 and supplies the valid output to the second switch drive circuit 314 when any of the outputs becomes valid. Is.

The first switch drive circuit 312 is a voltage generation circuit that generates a signal for controlling the charge path cutoff switch element 220 to turn off, and responds to the logic output from the first OR circuit 308 to generate a predetermined output. Is supplied to the first switch element 220. Similarly, the second switch drive circuit 314 is a voltage generation circuit that controls the discharge path blocking switch element 230 to be off, and outputs a control signal in response to the logic output from the second OR circuit 310.

Returning to FIG. 1, the charge path cutoff switch element 220 is a semiconductor switch formed of a field effect transistor (FET) that operates at a low voltage such as C-MOS, and together with the charge path diode 240. It is a first switch element that forms a charging path. This charge path blocking switch element 220 is preferably a normally-off type P-channel enhancement type field effect transistor which is turned on at a negative voltage, and is normally turned on and charged in the charging direction (see FIG. Is a switch element that conducts a current in the direction of arrow X) and is turned off by a positive control voltage from the control circuit 210 to cut off the current in the charging direction. Specifically, as shown in FIG. 1, the drain D is connected to the positive terminal side of the secondary battery 10, the source S is connected to the input / output terminal 32 side via the charge path diode 240, and the gate G is controlled. A control voltage from circuit 210 is applied. Further, the field-effect transistor 220 has a parasitic diode 222 inside the source S and the drain D in the OFF state in the direction opposite to the blocking direction, that is, in the discharge direction due to its structure.

The discharge path cutoff switch element 230 is a semiconductor switch formed of, for example, a normally-off type P-channel enhancement type field effect transistor similarly to the charge path cutoff switch element 220, and together with the discharge path diode 250. It is a second switch element that forms a discharge path. This switch element for interrupting the discharge path
230 is arranged in parallel to the charging path including the first switching element 220 and the first diode 240 and in the opposite direction to the first switching element 220, and is normally turned on and in the discharging direction (arrow in the figure). It is a second switch that allows a current in the Y direction) to pass therethrough and shuts off the current in the discharge direction when it is turned off. Specifically, the source S is connected to the plus terminal side of the battery 10 and the drain D is connected to the input / output terminal 32 side in the discharge path, and the control signal from the control circuit 210 is supplied to the gate G. This second field effect transistor 230 is
Like the field effect transistor 220, the parasitic diode 232, which conducts in the drain D-source S direction, that is, the charging direction in the off state due to its structure, is included inside.

On the other hand, the charge path diode 240 is connected in series to the charge path cutoff switch element 220 in the charge path, and conducts a current in the charge direction when the switch element 220 is on, and cuts off a current in the discharge direction when the switch element is off. This is the first diode. Various diodes such as a Schottky barrier diode, a germanium diode, or a silicon-based diode are effectively applied to the first diode 240 to prevent the parasitic diode 222 from conducting when the first switch element 220 is off. . Similarly, the discharge path diode 250 is connected in series to the discharge path cutoff switch 230 in the discharge path, conducts the current in the discharge direction when the switch is on, and interrupts the current in the charge direction when the switch is off and is a parasitic diode. It is a second diode that prevents the conduction of 232.

The operation of the secondary battery charge / discharge protection device of the present embodiment having the above-mentioned structure will be described. First, the battery pack 30 formed as a secondary power supply device is attached to, for example, a portable electronic device, and connected to the internal circuit of the device at terminals 32 and 34. Next, when charging the secondary batteries 10 and 12, when the power cord of the device is connected to an AC power source, the charging circuit inside the device supplies the charging current to the power supply device 30 via the terminals 32 and 34. . At this time, if the control circuit 210 detects the voltages of the secondary batteries 10 and 12 and the respective voltage values are within a predetermined value, the control voltage from the control circuit 210 to the switch elements 220 and 230 is set as a negative voltage, The switch elements 220 and 230 are turned on. As a result, the charging current flows from the terminal 32 to the secondary battery 1 via the charging path diode 240 and the charging path cutoff switch element 220.
0, 12 are supplied to the secondary battery 10, 12 through the terminal 34, and a current flows in the charging direction to the device side through the terminal 34 to charge the secondary battery 10, 12, respectively.

In this state, if the charging progresses and one of the secondary batteries 10 and 12 becomes fully charged and the charging state continues, the battery that has been fully charged first becomes the upper limit of the chargeable state. Reach For example, when the first secondary battery 10 reaches the upper limit of the chargeable state and the detected voltage from the first battery voltage detection circuit 300 becomes, for example, 4.2V to 4.3V, this is sent to the first comparison circuit 304. And the effective output is supplied to the first OR circuit 308. At this time, the second voltage detection circuit 302 detects that the voltage of the second secondary battery 12 has not reached 4.2V, and the second comparison circuit 306 to the first OR circuit 308.
Output to is invalid output. But first
In the OR circuit 310, the effective output from the first comparison circuit 304 is supplied to the first switch drive circuit 314. As a result, the first switch drive circuit 314
A positive control voltage is supplied to the gate G of the field effect transistor 220.

As a result, the first field effect transistor
The drain-source current of 220 is cut off, and the current in the charging direction X from the terminal 32 is cut off. As a result, overcharge of the first secondary battery 10 is prevented. When the battery pack 30 in such a state is attached to an electronic device and used, its discharge current passes from the positive terminal of the battery 10 through the discharge interruption switch element 230 in the on state of the discharge path and further through the discharge path diode 250. , From the terminal 32 toward the device. At this time, a current in the discharging direction tends to flow through the parasitic diode 222 of the charge cutoff switch element 220. However, since the charge path diode 240 connected in series to the charge cutoff switch element 220 is in the opposite direction to the parasitic diode 222, the current in the discharge direction from the parasitic diode 222 is cut off. As a result, the conduction of the parasitic diode 222 is prevented.

When the charging current is interrupted by the first field effect transistor 220 as a result of the upper limit of the chargeable state of the first secondary battery 10 shown above, the first secondary battery 10 When the voltage of the first battery 10 drops below 4.2V due to the averaging of the internal impedance of the battery or the ion concentration inside the battery, the control circuit 210 detects this and shuts off the charge. The control voltage to the switch element 220 is set to a negative voltage. As a result, the charge cutoff switch element 220
Is turned on, and charging of the secondary batteries 10 and 12 is started again via the charge path diode 240.

On the other hand, when the electronic device is in use, when the power switch of the device is turned on, the secondary batteries 10 and 12 are discharged to supply power to the device. At this time, if the control circuit 210 detects the voltages of the secondary batteries 10 and 12 and the respective voltage values are within the predetermined values, the control voltage from the control circuit 210 to the switch elements 220 and 230 is in a negative voltage state. Yes, the switch elements 220 and 230 are in the ON state. As a result, the discharge current flows from the positive terminal of the battery 10 to the input / output terminal via the switch element 230 and the diode 250 in the discharge path.
It reaches 32 and flows into the equipment. Further, a current flows from the device to the battery 12 through the terminal 34 in the discharging direction, and the secondary batteries 10 and 12 are discharged.

In this state, for example, the secondary batteries 10 and 12
As a lithium battery in a camera-integrated VTR device
If continuous shooting for more than a time is performed, the secondary battery 10,1
Each voltage value of 2 falls below 3.0V. further,
If you continue to operate the equipment and the secondary batteries 10 and 12 are discharged,
Either of the secondary batteries 10 and 12 approaches the operating voltage lower limit value. For example, if the detected voltage from the first battery voltage detection circuit 300 becomes, for example, 2.4 V to 2.5 V when the first secondary battery 10 approaches the lower limit of the operating voltage, this is detected by the first comparison circuit 304. Upon detection, a valid output is supplied to the second OR circuit 310. At this time, the voltage of the second secondary battery 12 is, for example, 2.
It is assumed that the second voltage detection circuit 302 detects that the voltage has not reached 4V, and the output from the second comparison circuit 306 to the second OR circuit 310 is an invalid output. But the second OR
In the circuit 310, the effective output from the first comparison circuit 304 supplies the effective output to the second switch drive circuit 314. As a result, the second switch drive circuit 314 becomes the second switch drive circuit 314.
A positive control voltage is supplied to the gate G of the field effect transistor 230.

As a result, the second field effect transistor
The drain-source current of 230 is cut off and the battery 10,1
The current in the discharge direction Y passing through the discharge path from 2 is cut off.
When trying to charge the battery pack 30 in such a state,
The current in the charging direction flows from the negative terminal of the battery 10 to the terminal 34 via the battery 12, and further via the terminal 32 to the charge path diode 240 and the charge path interruption switch element 220 in the ON state to the positive terminal of the battery 10. Flow to. At this time, a current in the charging direction also tries to flow in the parasitic diode 232 of the switch element 230 for discharging the discharge, but the energizing direction of the second diode 250 connected in series to this is the opposite direction to the parasitic diode 232. Therefore, the current flowing in the charging direction is cut off to prevent the parasitic diode 232 from being energized.
Next, when the voltage of the first battery 10 exceeds 2.4V, the control circuit 210 detects this and sets the control voltage to the discharge interruption switch 230 to a negative voltage. As a result, the discharge cutoff switch 230 is turned on to enable the discharge and prevent over-discharge.

Next, in order to clarify the characteristic point of the present invention, the effect is further clarified by comparing the comparative example shown in FIG. 7 with this embodiment. The first and second diodes 240,250 are removed and the switch elements 220,230 are connected in series. According to this, when the control circuit 210 detects that the batteries 10 and 12 are fully charged during charging, the first switch element 220 is turned off. As a result, the current in the charging direction is cut off, and the current in the discharging direction at that time passes through the parasitic diode 222 of the first switch element 220, which is off from the batteries 10 and 12.
Further, it flows to the terminal 32 through the second switch element 230 which is turned on. When discharged, either battery 10,12
Is approaching the discharge limit, the second switch element 230 is turned off. As a result, the discharge current is interrupted, and the current in the charging direction at that time passes through the parasitic diode 232 of the second switch element 230 that is off from the terminal 32, and is further turned on. Battery through 220
Inflow to 10,12. Therefore, when each of the switch elements 220 and 230 is turned off, a current flows through the parasitic diodes 222 and 232, and a current different from the original structure causes deterioration of the elements, resulting in deterioration of switch characteristics and eventually destruction of the elements themselves.

In this embodiment, each switch element 22
The diodes 240 and 250 that conduct in only one direction are connected in series to 0 and 230, and they are arranged in parallel.Therefore, the current in the direction different from the breaking direction of each switch 220 and 230 that occurs when the switch is turned off conducts the parasitic diode 222 and 232. This prevents the switch characteristics from being deteriorated and the element from being destroyed.

In the above embodiment, the case where the battery pack 30 is mainly mounted in the camera-integrated VTR has been described as an example, but the present invention can of course be mounted in other electronic equipment. Further, in the above-mentioned embodiment, the case where the lithium ion battery is used has been mainly described, but other secondary batteries may be used in the present invention, and the first and second set voltages at that time are different from those of the respective batteries. Of course, you may change it depending on the characteristics.
Furthermore, in the above-described embodiment, the case where the field effect transistor is used as the switch element has been described as an example, but other electronic switch elements may be used in the present invention.

In the above embodiment, two secondary batteries 10,1 are used.
Although the case of using 2 has been described as an example, the present invention can of course be applied to the case where one battery is used alone as shown in FIG. Further, in the above embodiment, the control circuit 210 is configured to detect the terminal voltage of each of the batteries 10 and 12. However, in the present invention, the voltage across the plurality of batteries connected in series as shown in FIG. May be detected. Further, in the present invention, as shown in FIG.
The switches 220 and 230 may be controlled by detecting the voltage of each of the N or more batteries and detecting that any one of the voltages has become higher or lower than a predetermined set voltage. Furthermore, in the above embodiment, the switch elements 220 and 230 and the diodes 240 and 250 are arranged on the plus terminal 32 side with respect to the secondary batteries 10 and 12, respectively. However, in the present invention, for example, as shown in FIG. You may arrange.

As described above, the present invention is not limited to the above-described embodiments at all, and includes all the improvements or applications made without departing from the matters recited in each claim of the claims.

[0033]

As described above in detail, according to the charge / discharge protection device for a secondary battery according to the present invention, a charge path and a discharge path, in which a parasitic diode and a diode opposite to the parasitic diode are connected in series, are connected to a switch element. Since they are connected in parallel and placed at the input / output terminals of the battery, when the switch element on either path is turned off, the current will flow to the other path before the current flows to the parasitic diode, and to the switch element. The reverse current can be prevented from flowing. As a result,
It is possible to prevent the deterioration of the device, prevent the device from being damaged due to the deterioration of the device performance and the device, and to obtain the secondary battery charge / discharge protection device with safer operation.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a secondary battery power supply device to which a secondary battery charge / discharge protection device according to the present invention is applied.

FIG. 2 is a functional block diagram showing an example of an internal configuration of a control circuit applied to the embodiment of FIG.

FIG. 3 is a circuit configuration diagram showing another embodiment of a secondary battery power supply device to which a secondary battery charge / discharge protection device according to the present invention is applied.

FIG. 4 is a circuit configuration diagram showing another embodiment of a secondary battery power supply device to which a secondary battery charge / discharge protection device according to the present invention is applied.

FIG. 5 is a circuit configuration diagram showing another embodiment of a secondary battery power supply device to which a secondary battery charge / discharge protection device according to the present invention is applied.

FIG. 6 is a circuit configuration diagram showing another embodiment of the secondary battery power supply device to which the secondary battery charge / discharge protection device according to the present invention is applied.

FIG. 7 is a circuit configuration diagram showing a comparative example for clarifying the effect of the secondary battery charge / discharge protection device according to the present invention.

[Explanation of symbols]

 10,12 Secondary battery 210 Control circuit 220 Charge cutoff switch element 230 Discharge cutoff switch element 222,232 Parasitic diode 240 Charge path diode 250 Discharge path diode

[Procedure amendment]

[Submission date] December 8, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (5)

[Claims] 1. A secondary battery charge / discharge protection device for preventing overcharge and overdischarge of a rechargeable secondary battery, wherein the device is connected to a charging path of the secondary battery and is normally turned on. First switching means for conducting a current in the charging direction and interrupting a path in the charging direction when turned off, the first switching means including therein a parasitic diode that conducts in the discharging direction when turned off; Is a second switch means that is connected to the discharge path and normally turns on to conduct a current in the discharge direction and shuts off the path in the discharge direction when turned off. A second switch means including the first switch means for detecting a battery voltage of the secondary battery, and when the battery voltage is equal to or higher than a first set voltage in the vicinity of full charge of the secondary battery. Turn off and Control means for turning off the second switch means when the pond voltage becomes equal to or lower than a second preset voltage near the end of discharge, the charging path and the discharging path are the secondary battery and A first diode, which is connected in parallel to the one input / output terminal in a branched manner, is connected to the charging path in series with the first switch unit in a direction opposite to the conduction direction of the parasitic diode of the first switch unit. A charging / discharging protection device for a secondary battery, wherein a second diode in a direction opposite to a conduction direction of the parasitic diode is connected in series to the second switch means in the discharging path. 2. The charging / discharging protection device for a secondary battery according to claim 1, wherein a plurality of batteries are connected in series to the secondary battery, and the control means controls the battery voltage of each secondary battery. Monitoring, when any one of the battery voltages becomes equal to or higher than the first set voltage, the first switch means is turned off, and when any one of the battery voltages becomes equal to or less than the first set voltage, A secondary battery charging / discharging protection device, characterized in that the second switch means is turned off. 3. The charging / discharging protection device for a secondary battery according to claim 1, wherein a plurality of batteries are connected in series to the secondary battery, and the control means is provided between both ends of the batteries connected in series. When the voltage is monitored and the voltage value becomes equal to or higher than the first set voltage, the first switch means is turned off, and when the voltage value becomes equal to or lower than the second set voltage, the second switch A charging / discharging protection device for a secondary battery, characterized in that the means is turned off. 4. The charging / discharging protection device for a secondary battery according to claim 1, wherein the secondary battery is used alone, and the control circuit detects the voltage across both ends of the secondary battery. When the value becomes equal to or higher than the first set voltage, the first switch means is turned off, and when the voltage value becomes equal to or lower than the second set voltage, the second switch means is turned off. Secondary battery charge and discharge protection device. 5. The charging / discharging protection device for a secondary battery according to claim 1, wherein the charging path in which the first switch means and the first diode are arranged, and the second switch means and the second diode are provided. A charging / discharging protection device for a secondary battery, wherein both of the arranged discharge paths are arranged in parallel to either the positive or negative path of the secondary battery.