JPH07235335A - Battery device - Google Patents

Abstract

PURPOSE:To provide a secondary battery which works at a low cost and with a low power consumption and which is prevented from being deeply discharged or from over-current flowing. CONSTITUTION:A discharge switch 6 in which at least the discharge path is capable of being turned on and off, is formed from an electronic switch consisting of a bipolar transistor capable of being produced at a low cost. A low cost element such as a diode is used as a temp. sensing element for sensing the temp. of a secondary battery. Existence of any load is sensed on the basis of the voltage generated due to the on-resistance of the discharge switch 6, and if no load, the current to the base of the switch 6 is limited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery device, and in particular, a built-in rechargeable secondary battery such as a nickel-cadmium (hereinafter referred to as NiCd) battery or a lithium-ion battery, for example, a driving power source for various portable devices. The present invention relates to a battery device used as.

[0002]

2. Description of the Related Art For example, in a portable recorder such as a camcorder (video camera integrated with VTR) or a camcorder, a lighting for photographing, a portable cassette player, a disc player or the like is generally used as a power source for driving the device. A battery device incorporating a rechargeable secondary battery can be used. As such a secondary battery, for example, a nickel-cadmium battery (nickel cadmium battery), a lithium-ion battery, or the like is known. By connecting these single secondary batteries in series to form an assembled battery, a required DC A battery device having a power supply voltage can be obtained.

The battery device as described above is configured as, for example, a power pack housed in a casing that can be attached to the electronic device and the charger. Then, by mounting the battery device at a predetermined position of the electronic device body, the electrodes come into contact with each other and the power supply voltage can be supplied from the battery device to the device side. Therefore,
For example, when the power of the electronic device is turned on, the secondary battery inside the battery device is discharged and the device is driven. When the battery device is attached to the corresponding charger, the built-in secondary battery is charged by the operation of the charger.

By the way, even if the electronic device is turned off, if the battery device having the built-in secondary battery is left attached to the device, a dark current flows through the electronic device as a load. Even though the secondary battery is slightly discharged, it will continue during this period. Then, if such a state continues for a long time, the secondary battery goes beyond the overdischarged state and is in a so-called deep discharge state.

For example, FIG. 4 shows the charging characteristics of a general NiCd battery, in which the vertical axis represents the battery voltage and the horizontal axis represents the charge amount. When charging a nickel-cadmium battery, for example, trickle charging is first performed with a current having a relatively small level, and if a voltage above a certain level is obtained, the level of the charging current is increased and the mode is shifted to rapid charging. Then, at this stage, when −ΔV shown in the figure is obtained, the supply of the rapid charging current is stopped and trickle charging is performed again. After that, when a predetermined time set by the timer has elapsed, the charging is terminated. In this way, the secondary battery is appropriately charged.

However, when the secondary battery in the deeply discharged state is charged by the above method, for example, a voltage sufficient to shift to the quick charge regardless of how much is charged by the first trickle charge. It falls into the state of inactivation that does not reach. Therefore, even if the rechargeable battery once in the deactivated state is charged by the charging device, it cannot be restored so as to obtain the proper fully charged state. Further, if an excessive discharge current flows through the secondary battery due to some failure or abnormality, the battery may generate heat and in the worst case, may explode.

Therefore, the deep discharge of the secondary battery as described above,
In order to prevent the overcurrent from flowing to the secondary battery, FIG.
A battery device provided with a circuit as shown in FIG. In this figure, reference numeral 1 denotes a rechargeable battery such as a rechargeable lithium-ion battery or a nickel-cadmium battery. Also, 2
Indicates a load, which is a circuit of the electronic device that can be driven by the battery device. Further, 3 connected as shown by a broken line indicates a charger. Then, in actuality, either the load 2 (electronic device) or the charger 3 is attached to the battery device to load the load 2 of the secondary battery 1.
Can be discharged or the secondary battery 1 can be charged. In this case, it is assumed that the load is connected to the battery device in order to prevent deep discharge when the load is connected.

Reference numerals 21 and 22 denote comparators, respectively. As shown in the figure, the non-inverting input of the comparator 21 is connected to the power supply line A, and the inverting input is connected to the resistor R ₂₃ connected in series between the power supply line A and ground and the Zener diode ZD ₁ having a predetermined Zener voltage. Connected with a point. Therefore, in the comparator 21, the voltage of the secondary battery, the resistance R _23, and the Zener diode ZD
_When the voltage of the secondary battery is higher than the reference voltage, the detection signal of the H level is output, and when the voltage of the secondary battery is lower than the reference voltage, the detection signal of the L level is output. In addition, the comparator 2
The voltage and the reference voltage set by the resistor R ₂₃ and the Zener diode ZD ₁ are input to the inverting input of 2, and the power is supplied to the non-inverting input by the resistor R ₂₄ and the temperature detecting unit 23 whose resistance value changes with temperature. The voltage obtained by dividing the line A is input. The temperature detection unit 23 is, for example, the secondary battery 1
Shows a temperature change depending on the amount of current, the secondary battery 1
It is placed at a position where the temperature can be detected. Further, as its characteristic, its resistance value is supposed to decrease with an increase in temperature.

When the temperature detected by the temperature detector 23 is low and its resistance value is high, the voltage input to the non-inverting input of the comparator 22 is higher than the reference voltage of the inverting input. Therefore, the comparator 22 outputs an H level detection signal. On the other hand, the temperature detected by the temperature detector 23 is high,
When the resistance value becomes low, the voltage input to the non-inverting input becomes lower than the reference voltage of the inverting input, so that the L-level detection signal is output. in this way,
The comparator 21 is for detecting the voltage of the secondary battery 1, and the comparator 22 is for detecting the temperature of the secondary battery 1.

Reference numeral 24 indicates an AND gate, to which the detection signals of the comparators 21 and 22 are input. Further, its output is connected to the gate of the FET 25. 25 is FE
T is shown and the drain is connected to the load side and the source is connected to ground as shown. Therefore, in this case, F
The ET 25 functions as a switch that turns on / off the path of the discharge current. D ₁₁ is a diode, and the cathode is F
Connected to the drain side of ET25, the anode is FET2
It is provided in parallel with the FET 25 so as to be connected to the source side of the FET 5. Therefore, the diode D ₁₁ serves as a path for a charging current flowing when the charger 3 is connected to the battery device shown in FIG. In addition, R ₂₁ , R ₂₂ ,
R ₂₅ represents resistance.

According to the battery device having the above structure, for example, when the load 2 (circuit of the electronic device) is connected and the remaining amount of the secondary battery 1 is sufficient, the comparator 21 outputs the H level signal. The detection signal is AND gate 24
Is supplied to. Further, at this time, if there is no abnormality such that an overcurrent flows through the secondary battery 1 in the circuit, the temperature detection unit 23 maintains a high resistance value, and therefore the comparator 23 supplies the H level detection signal to the AND gate 24. To be done.
In this way, if the remaining amount of the secondary battery 1 is sufficient and there is no abnormality, the AND gate 24 outputs the H level.
Then, by applying this H-level signal to the gate of the FET 25, the drain-source is turned on and the discharge path of the secondary battery 1 to the load 2 is brought into conduction.

Here, considering a case where a battery device is connected to an electronic device whose power is off, for example, when there is a sufficient remaining amount of the secondary battery 1 as long as there is no abnormality, Thus, the discharge path of the secondary battery 1 is formed. However, in the above state, as described above, the dark current flows through the device, so that the remaining amount of the secondary battery 1 gradually decreases and the voltage thereof also decreases. In this way, when the voltage of the secondary battery 1 becomes lower than the reference voltage set by the resistor R ₂₃ and the Zener diode ZD ₁ , the L-level detection signal is output from the comparator 21. As a result, an L level signal is output from the AND gate 24, and the L level signal is further output from the FET 2
By being applied to the gate of the FET 5, the drain of the FET 25-
The source is turned off, and the discharge path of the secondary battery 1 to the load 2 is cut off. This allows the secondary battery 1
Since the dark current flowing through the load 2 is almost eliminated, the secondary battery is prevented from being deeply discharged and inactivated even when the battery device is left attached to the power-off electronic device for a long time. To be done.

In any case, some abnormality occurs and an excessive discharge current flows out, and the secondary battery 1
If the temperature rises, the temperature of the temperature detector 23 also rises and its resistance value decreases. Accordingly, the detection signal output from the comparator 21 becomes H
Since the level changes from the L level to the L level, the output supplied from the AND gate 24 to the gate of the FET 25 also changes from the H level to the L level.
It becomes a level. Therefore, the drain-source of the FET 25 is turned off and the discharge path of the secondary battery 1 to the load 2 is cut off, so that the abnormal discharge of the secondary battery 1 can be stopped.

[0014]

However, as in the battery device having the above structure, the FET is turned on / off in the discharge path.
When 25 is used, the cost is high because the FET 25 is expensive. Similarly, a fuse, a thermal protector, a PTC (Posi
A temperature detecting element such as a tive tempereture coeficient thermistor) is used, but since these are also expensive, there is a problem of high cost. Therefore, an object of the present invention is to obtain a battery device capable of preventing deep discharge of a secondary battery and overcurrent flowing in the secondary battery at low cost, but in realizing this, it seems that power consumption is low. Is preferably configured.

[0015]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is directed to a battery device having a built-in secondary battery, in which a load detector capable of detecting the presence or absence of a load and a discharge to the load of the secondary battery are discharged. A transistor switch unit of an electronic switch that is capable of turning on / off the conduction of the path and is formed of a bipolar transistor, and a base current variable unit that varies the base current of the transistor switch unit based on the detection signal of the load detection unit are provided. The load detection unit is configured to output a detection signal based on the result of comparing the voltage generated by the ON resistance of the transistor switch unit with a predetermined reference voltage. Further, a discharge temperature detecting unit capable of detecting a temperature change of a predetermined circuit unit at the time of discharging is provided, and the current variable control of the base current changing unit is configured based on the detection signal output from the discharge temperature detecting unit. It was decided to. In addition, the charging switch section is equipped with a charging switch section that can turn on / off the conduction of a signal path through which the charging current flows, and a charging temperature detection section that can detect a temperature change of a predetermined circuit section during charging. The configuration is such that on / off control is performed based on the detection signal of the detection unit. Further, diodes are used for the temperature detecting elements used in the discharge temperature detecting section and the charging temperature detecting section.

[0016]

According to the above structure, the discharge path is turned on / off by the electronic switch formed of an inexpensive bipolar transistor. In addition, it is possible to detect the presence or absence of a load and limit the current flowing to the base of the bipolar transistor when there is no load to reduce the current consumption at this time. Further, if the load detection unit is configured to output the detection signal based on the result of comparing the voltage generated by the ON resistance of the transistor switch unit and the predetermined reference voltage, it is not necessary to provide the detection element. Also, during overcurrent protection during discharge, the electronic switch should be operated by limiting the current flowing to the base of the bipolar transistor, for example, based on the detection signal of the temperature change of the secondary battery or the switch detected by the temperature detector. Is possible. Furthermore, by providing a switch part in the signal path through which the charging current flows and turning on / off based on the detection signal of the temperature detecting part, it is possible to limit not only the overcurrent at the time of discharging but also at the time of charging. Becomes If a diode is used for the temperature detecting element, the temperature detecting section can be constructed at low cost.

[0017]

1 is a circuit diagram showing an embodiment of a battery device of the present invention, in which 1 is a secondary battery, 2 is a load, 3 is a charger, for example, as shown in FIG. Therefore, the description is omitted here. Reference numeral 4 denotes a constant voltage circuit for inputting the voltage of the secondary battery and applying a base current to the base of the discharge switch 6 via the resistor R ₁ with a predetermined constant voltage. R ₁ inserted between the constant voltage circuit 4 and the discharge switch 6 is a current limiting resistor having a high resistance. A bypass switch 5 connected in parallel to the resistor R ₁ controls ON / OFF of conduction according to the output of the AND gate 9. Reference numeral 6 denotes a discharge switch that is connected in series with the load 2 and is capable of turning on / off the conduction of a signal path for discharging. The discharge switch 6 is composed of, for example, an electronic switch made of an inexpensive bipolar transistor. That is, the base is connected to the constant voltage circuit 4 via the resistor R ₄ and the bypass switch 5, as shown equivalently in the circle B, and the collector and the emitter are connected to the load 2 respectively.
Side and ground side can be represented as being connected. Note that the bypass switch 5 described above may also be similarly configured by an electronic switch made of an inexpensive element such as a bipolar transistor. In this case, the base is connected to the AND gate 9, and the collector is the constant voltage circuit 4. It is connected to the output, and the emitter is connected to the base side of the discharge switch 6.

D ₁ represents a diode, which is connected in parallel to the discharge switch 6 and the ground, and the anode side is connected to the ground as shown in the figure. That is, the diode D ₁ forms a path through which the charging current flows through the discharge switch 6 when the charger 3 is connected to the battery device to perform charging.

Reference numeral 7 denotes a comparator provided for load detection. A reference voltage obtained by dividing the voltage of the power supply line A by the resistors R ₂ and R ₃ is input to the inverting input of the comparator 7, and the non-inverting input is connected to the connection point between the load 2 and the discharge switch 6. . The resistor R ₃ may be a Zener diode as shown in parentheses, but it is preferable in terms of cost to use a resistor because it is cheaper. By the way, for example, the electronic device is actually connected, and the electronic device is powered on and operating, that is, the load 2 is supplied by the power supply voltage of the secondary battery 1.
When the discharge switch 6 is in the ON state in a state in which the discharge switch 6 is driven (hereinafter, this state is also referred to as a load), the discharge current will flow there. Since it is an electronic switch, it has a so-called on-resistance for the current flowing between the collector and the emitter. As a result, the collector of the discharge switch 6
A voltage V _CE will be generated between the emitters.

On the other hand, a state in which the power of the electronic device is off even if the load 2 is not connected or is connected (hereinafter, these states are also referred to as a no-load state).
Then, no current flows from the load 2 to the discharge switch 6 or the dark current flowing to the electronic device described above also flows to the battery device side. As a result, in the no-load state, no current flows through the switch section 6, or the amount of current is significantly reduced as compared with when there is a load, so that the collector-emitter voltage V _CE cannot be obtained or drops. .

Therefore, in this embodiment, the collector-emitter voltage V of the discharge switch 6 is applied to the non-inverting input of the comparator 7.
_{The CE} is input and compared with the reference voltage, that is, the discharge switch 6 that originally turns on / off the conduction of the discharge path is used for load detection. In the comparator 7, when the load is applied, the collector-emitter voltage V _CE becomes higher than the reference voltage, and therefore the H level is output as a detection signal. When the load is not applied, the collector-emitter voltage V _CE becomes lower than the reference voltage, and therefore the L level. Will be output.

Reference numeral 8 denotes a comparator for detecting the temperature of the secondary battery 1 during discharging. A voltage obtained by dividing the voltage of the power supply line A by the resistors R ₅ and R ₆ is input to the inverting input of the comparator 8 as a reference voltage, and the voltage of the power supply line A is input to the non-inverting input of the resistor R ₄ and the temperature. The voltage obtained by voltage division by the detection diode D ₂ is input. The temperature detection diode D ₂ is a temperature detection element, and the resistance value in the forward direction is reduced as the temperature rises. Further, in practice, for example, it is arranged near the secondary battery 1 so that the temperature change of the secondary battery 1 can be detected. Alternatively, in the case of the present embodiment, the temperature of the discharge switch 6 which is an electronic switch also changes in accordance with the amount of current flowing therethrough, so it is possible to dispose the discharge switch 6 near the discharge switch 6.

For example, during normal times when there is no abnormality and no excessive current flows in the state in which the discharge path is formed, the temperature of the secondary battery 1 does not rise significantly, so that the temperature detection diode D ₂ also does not rise in temperature. . As a result, the voltage divided by the resistor R ₄ and the temperature detection diode D ₂ becomes higher than the reference voltage, so that the comparator 8 outputs the H level. On the other hand, if some kind of abnormality occurs and an excessive current flows through the secondary battery 1 and the temperature rises, the temperature detection diode D ₂ also rises in temperature and its resistance value becomes low, so that the L level. Will be output.

Reference numeral 9 denotes an AND gate, to which the detection signals of the comparators 7 and 8 are input. The output of the AND gate 9 is output to the bypass switch 5 as an on / off control signal. It should be noted that the AND gate 9 may actually be configured as a part of the bypass switch 5.

Next, the operation of the battery device having the above structure when there is a load will be described. In this case, since the current for driving the load 2 flows as described above, the collector-emitter voltage V _CE is obtained in the discharge switch 6. Therefore, the comparator 7 detects this voltage V _CE and outputs an H level detection signal to the AND gate 9. Further, especially when there is no abnormality in the circuit or the like, the temperature detection diode D ₂ does not detect the temperature rise of the secondary battery 1, so that the comparator 8 supplies the H level detection signal to the AND gate 9.

As described above, if both inputs of the AND gate 9 become H level, the output thereof becomes H level, and this H level output is inputted to the bypass switch 5 as an ON / OFF control signal. ing. In this embodiment, the bypass switch 5 is configured to be turned on when an H level is input and turned off when an L level is input. Therefore, in this case, the bypass switch 5 is turned on. When the bypass switch 5 is turned on as described above, the output of the constant voltage circuit 4 is supplied to the discharge switch 6 via the bypass switch 5 without passing through the current limiting resistor R ₁ . Therefore, it is possible to sufficiently supply the base current to the base of the discharge switch 6, and it is possible to reduce the on-resistance between the collector and the emitter of the discharge switch 6, which is a loss when the load is driven.

Next, the case where the battery device is under no load will be described. In this case, the discharge current for driving the load does not flow, and if the power supply is off and the electronic device is still connected, a dark current on the electronic device side flows. . Therefore, since the emitter-collector voltage V _CE of the discharge switch 6 decreases due to the change in the current flowing through the discharge switch 6 as described above, the load detection comparator 7 has a voltage lower than the reference voltage of the inverting input. Since the comparison voltage of the inverting input (emitter-collector voltage V _CE ) becomes low, the L level is output as the detection signal. Further, at this time, if there is no particular abnormality and the temperature of the secondary battery 1 does not rise, the H level is output from the comparator 8 as in the case of the loaded state. That is, in this case, since the L level (the output of the comparator 7) and the H level (the output of the comparator 8) are input to the AND gate 9, the AND gate 9 must output the L level signal. become.

In this way, the L level is supplied to the bypass switch 5 as the ON / OFF control signal, so that the bypass switch 5 is turned off and becomes non-conductive. Therefore, the output of the constant voltage circuit 4 is supplied to the base of the discharge switch 6 via the current limiting resistor R ₁ . Therefore, the base current supplied to the discharge switch 6 is suppressed even when the remaining amount of the secondary battery 1 has a margin and the battery voltage is sufficient. In this way, the current consumed when there is no load can be saved. Further, even in the above state, for example, if the battery device is still connected to the power-off electronic device, the remaining amount of the secondary battery 1 will gradually decrease due to the dark current described above. When 1 becomes lower than a certain constant voltage, the base current of the discharge switch 6 does not flow from the constant voltage circuit 4 through the current limiting resistor R ₁ at all. As a result, the discharge switch 6 is turned off and the discharge path can be cut off, so that deep discharge of the secondary battery can be prevented.

Further, when some abnormality occurs in a circuit or the like and an excessive discharge current flows through the secondary battery 1 to raise its temperature, the diode D ₂ which is a temperature detecting element is detected.
The temperature also rises and the resistance value of itself decreases. As a result, regardless of the loaded / unloaded state, the comparator 8
The L level detection signal is output to the AND gate 9. Especially when the secondary battery 1 is in an abnormal discharge state and a temperature rise is detected under load, the comparator 8 supplies the L level to the AND gate 9. Even if the detection signal is set to H level and is supplied to the AND gate 9,
An AND gate 9 outputs an L-level ON / OFF control signal to the bypass switch 5. As a result, the base current of the discharge switch 6 is limited as the bypass switch 5 is turned off, so that an excessive discharge current is prevented from flowing in the discharge path.

The load 2 is applied to the battery device of this embodiment.
In place of charging, the charger 3 is connected to perform charging, and the diode D provided in parallel with the discharge switch 6
_A charging path via ₁ is formed, and the secondary battery 1 is charged.

As described above, in this embodiment, the cost is reduced by using the electronic switch constituted by the inexpensive bipolar transistor as the discharge switch 6 for preventing the deep discharge of the secondary battery. Along with this, it is possible to reduce the consumption current by configuring so as to limit the base current flowing through the discharge switch 6 when there is no load. Furthermore, for load detection, the discharge switch 6
It is not necessary to newly load an element such as a resistance for load detection on the circuit by using the voltage V _CE generated in the circuit. In addition, a fuse, a thermal
The cost can also be reduced by using an inexpensive diode element without using a protector, PTC, or the like.

Next, a battery device as another embodiment will be described with reference to FIG. In the present embodiment, in addition to the configuration shown in the previous embodiment in which the base current control of the discharge switch is performed based on the result of detecting the presence or absence of a load, it is configured to prevent overcurrent during charging. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In the figure, reference numeral 11 denotes a charging switch provided on the path of the charging current. The charging switch 11 is provided in parallel with the discharging switch 6 as shown in the drawing, and is configured as, for example, an electronic switch. , Current flows in the direction indicated by the arrow in the frame. Further, in this case, if the H level is input as the ON / OFF control signal from the comparator 12 described below, it is turned on and L
When the level is input, it is turned off.

Reference numeral 12 denotes a comparator for detecting the temperature of the secondary battery 1. A reference voltage obtained by dividing the voltage of the power supply line A by the resistors R ₁₁ and R ₁₂ is input to the inverting input of this comparator, and the non-inverting input is a resistor connected in series between the power supply line A and ground. It is connected to the connection point between R ₁₃ and the temperature detection diode D ₃ . Like the temperature detection diode D ₂ of FIG. 1, the temperature detection diode D ₃ is assumed to have a resistance value in the forward direction which decreases in accordance with an increase in temperature.
In this case, it is provided in the vicinity of the secondary battery 1 so that the temperature of the secondary battery 1 can be detected. Or charging switch 1
Assuming that 1 is an electronic switch, this charging switch 11
It is also possible to arrange it in the vicinity of. In the comparator 12, when the temperature of the temperature detecting diode D ₃ does not rise and the resistance value is high, the voltage divided by the resistor R ₁₃ and the temperature detecting diode D ₃ becomes higher than the reference voltage. An H level detection signal is output. On the other hand, when the temperature of the temperature detecting diode D ₃ rises and its resistance value becomes low, the L level detection signal is output. Then, the detection signal of the comparator 12 is supplied to the charging switch 11 as an on / off control signal as shown in the figure. As described above, since the comparator 12 of the present embodiment controls the on / off of the charging switch 11 based on the detection result, it is provided as a temperature detecting unit for charging.

Reference numeral 13 indicates a constant voltage circuit. The constant voltage circuit 13 in this case is provided to supply the power supply V _CC to the comparator 7 and the comparator 12 as shown in the figure. For example, the comparator 7 and the comparator 12 are configured by bipolar transistors. In this case, if a constant voltage circuit 13 is provided and power is supplied from this at a required voltage, it is possible to reduce the current that should flow in the circuit. For example, the comparator 7 and the comparator 12 are bipolar transistors. Alternatively, the constant voltage circuit may be omitted as long as it is configured by a C-MOS or the like.

According to the above structure, first, when the load is detected, the load detecting comparator 7 detects the load and outputs the H level detection signal. As a result, the bypass switch 5 is turned on. The base current of No. 6 is sufficiently supplied to form the discharge path. On the other hand, when there is no load, this is detected by the comparator 7 and an L level detection signal is output, and the bypass switch 5
Turns off. As a result, the base current of the discharge switch 6 is limited as in the previous embodiment, and even if the battery device is left for a long time in the electronic device whose power is off, the secondary battery 1 is prevented from becoming a deep discharge.

As for the operation during charging, for example, during normal times when there is no particular abnormality in the circuit or the like and an excessive charging current does not flow to the secondary battery 1,
Temperature does not rise significantly, so the temperature detection diode D
_{Since the} temperature of ₂ also does not rise, the comparator 12 outputs the H-level detection signal as described above. Then, since the H level is input to the charging switch 11 as the ON / OFF control signal, the charging switch 11 is turned on and becomes conductive to form the charging path.

On the other hand, when some abnormality occurs in the circuit during charging and an excessive charging current flows in the secondary battery 1 and the secondary battery 1 generates heat, the temperature of the temperature detecting resistor D ₃ is changed. It rises and its resistance value decreases. As a result, the detection signal output from the comparator 12 is L
It becomes the level and is supplied to the charging switch 11. Then, the charging switch 11 to which the L level is input as the on / off control signal is turned off and switched to the non-conducting state, so that the path through which the charging current flows is cut off. As described above, in this embodiment, by turning on / off the conduction of the charging switch 11 provided in the charging path as the temperature of the secondary battery 1 rises during charging, some abnormality occurs during charging and an excessive current flows. Is being prevented.
The charge switch 11 can also be configured to use an electronic switch composed of a bipolar transistor, and in this case, the base current of the charge switch 11 is controlled by the detection signal of the comparator 12. In the present embodiment, the circuit portion (comparator 8, resistor R ₄ , temperature detecting diode D ₂ , resistor R ₅ , resistor R ₅ and resistor 8) relating to the temperature detection of the secondary battery for discharging shown in FIG. Although R ₆ ) is not shown, it is possible to add a temperature detecting unit at the time of discharging to the structure shown in FIG. 2 to prevent overcurrent at the time of discharging also in this embodiment. is there.

[0039]

As described above, in the battery device of the present invention, the switch portion and the like that can turn on / off the conduction of the discharge path and further the charge path are constituted by inexpensive bipolar transistors, and the secondary battery is used. By using an inexpensive element such as a diode as the temperature detecting element used for the temperature detection, the cost can be reduced. Further, by detecting the presence / absence of a load and limiting the base current of the bipolar transistor as the switch section when there is no load, unnecessary power consumption when there is no load is saved. Further, when the load is detected based on the voltage V _CE generated by the ON resistance of the switch section, it is not necessary to newly provide a detection element. Furthermore, if a switch unit is provided in the signal path of the charging current and ON / OFF is performed based on the detection signal of the temperature detection unit, overcurrent at the time of charging as well as at the time of discharging is prevented and reliability is improved. Will be improved.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of a battery device of the present invention.

FIG. 2 is a block circuit diagram showing a battery device of another embodiment.

FIG. 3 is a block circuit diagram showing a battery device in a conventional example.

FIG. 4 is a diagram showing the charging characteristics of a NiCd battery.

[Explanation of symbols]

 1 Rechargeable Battery 2 Load 3 Charger 4, 13 Constant Voltage Circuit 5 Bypass Switch 6 Discharge Switch 7, 8, 12 Comparator 9 AND Gate 11 Charge Switch

Claims (5)

[Claims] 1. A battery device containing a secondary battery, comprising: a load detection unit capable of detecting the presence or absence of a load; an electronic switch provided on a discharge path to the load by the secondary battery and comprising a bipolar transistor. And a base current varying unit that varies a base current of the transistor switching unit based on a detection signal of the load detecting unit. 2. The load detecting section is configured to output a detection signal based on a result of comparing a voltage generated in the transistor switch section with a predetermined reference voltage. Battery device. 3. A discharge temperature detector capable of detecting a temperature change of a predetermined circuit portion at the time of discharge, and a current variable control of the base current variable unit based on a detection signal output from the discharge temperature detector. The battery device according to claim 1 or 2, wherein the battery device is configured to be capable. 4. A charging switch section inserted into a signal path through which a charging current flows, and a charging temperature detecting section capable of detecting a temperature change of a predetermined circuit section at the time of charging, wherein the charging switch section is the charging circuit. The conduction control is performed based on a detection signal of the temperature detection unit.
Alternatively, the battery device according to claim 2 or claim 3. 5. The battery device according to claim 1, wherein a diode is used as a temperature detecting element in at least one of the discharge temperature detecting unit and the charging temperature detecting unit.