JPH07235333A - Battery device - Google Patents

Abstract

PURPOSE:To prevent a secondary battery from being deeply discharged even if it is fitted in an electronic appliance with the power off and left for a long time and interlock the operation of a switch part with the indication on a display part. CONSTITUTION:A voltage sensing part 10 is provided to senses the voltage of a secondary battery 8, and a switch part 9 inserted in a path for the discharge current of the secondary battery 8 is turned off when its voltage is below a specified level in conformity to the sensing signal given by the voltage sensing part 10, and thereby the discharge path for a load 5 is shut. The sensing signal is also fed to a residual amount display circuit 11 to make indication of the residual amount based upon the sensing signal.

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 battery which has a built-in rechargeable secondary battery such as a nickel cadmium (hereinafter referred to as NiCd) battery and is used as a driving power source for various portable devices. It relates to the device.

[0002]

2. Description of the Related Art For example, in various portable electronic equipment such as camcorders, portable cassette players and disc players, generally, a battery device incorporating a rechargeable secondary battery can be used as a power source for driving the equipment. Has been done. As such a secondary battery, for example, a nickel-cadmium battery (nickel cadmium battery), a lithium-ion battery, or the like is known, and by forming an assembled battery in which these single secondary batteries are connected in series, a required DC power source can be obtained. A battery device having a 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.

[0004]

By the way, even if the power of the electronic device is turned off, if the battery device containing the secondary battery is left attached to the device, the electronic device is a load. A dark current will flow through the secondary battery, and the secondary battery will continue to be discharged during this period, albeit slightly. 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 after a voltage of a certain level or higher is obtained, the level of the charging current is increased to shift 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 then trickle charging is performed again. After that, when the time set by the timer elapses, the charging is terminated. In this way, the secondary battery is appropriately charged.

However, if the secondary battery in the deeply discharged state is charged by the above-described method, for example, a predetermined trickle charge is enough to shift to the quick charge regardless of how much it is charged by the first trickle charge. The above voltage cannot be obtained and the device enters an inactivated state. Therefore, once the secondary battery is in the inactivated state, there is a problem that it is impossible to obtain a proper fully charged state even if the secondary battery is charged by the charging device.

[0007]

In view of the above problems, the present invention is a battery which can prevent a deep discharge of a secondary battery even when the secondary battery is left in a power-off electronic device for a long time. The purpose is to obtain the device. For this reason, a path through which the discharge current of the secondary battery should flow and a path through which the charging current of the secondary battery should flow are provided, and conduction / ON should be performed for the path through which the discharge current of the secondary battery should flow.
Insert the switch that can be turned off. Then, a voltage detection unit capable of detecting the voltage of the secondary battery is provided, and based on the detection signal output from this, the switch unit is turned off when the voltage of the secondary battery is lower than a predetermined value. I decided to configure it. Further, the remaining amount display unit configured to display the remaining amount of the secondary battery based on the detection signal of the voltage detection unit is provided.

[0008]

According to the above construction, when the voltage of the secondary battery becomes lower than the predetermined voltage, the connection with the load is cut off, so that the secondary battery is not discharged by the dark current flowing through the load.

[0009]

EXAMPLE FIG. 3 is a perspective view showing the external appearance of a battery device as an example of the present invention. 2 provided on the upper surface of the battery device 1 shown in this figure is an LED 2a and an LED 2b for indicating the remaining battery level. For example, the LEDs 2a and 2b each have a built-in secondary battery of a predetermined voltage or less. In this case, the predetermined voltage set in the LED 2a is set higher than the predetermined voltage set in the LED 2b. That is, both the LED 2a and the LED 2b are lit up to a voltage at which the remaining amount of the battery is sufficient and only the LED 2b is lit when the remaining amount of the battery is reduced to some extent but the voltage of the electronic device is sufficient. When the remaining amount further decreases and the voltage becomes a voltage required for charging, both the LED 2a and the LED 2b are turned off.

Reference numeral 3 is a check switch for checking the remaining amount. When the check switch 3 is pressed once, the remaining amount is displayed on the display unit 2 for several seconds, for example, depending on the remaining amount of the secondary battery at that time. It is done for a certain period of time. It is also conceivable that the remaining amount is displayed only while the check switch 3 is pressed. Further, although the display form of the display unit 2 enables three-stage display including the extinguished state by the LED, the display device and the display method are not limited to this. For example, it is possible to make various changes such as changing the number of steps of remaining amount display, or displaying with another display device or display element such as an LCD panel.

FIG. 1 is a diagram showing the internal configuration of a battery device 1 of this embodiment. In this figure, 4 indicates a charger separate from the battery device of this embodiment, and 5 indicates a circuit of the electronic device as a load. Further, on the side of the battery device 1, reference numerals 6 and 7 respectively indicate a positive electrode and a negative electrode, which are actually provided at predetermined positions in the housing of the battery device 1 and are connected to the charger 4 or the load 5. Reference numeral 8 denotes a rechargeable secondary battery. In this case, a plurality of NiCd cells are connected in series to form an assembled battery having a power supply voltage of a predetermined level. Reference numeral 9 denotes a switch portion, which is turned on when the secondary battery 8 is at a predetermined voltage or higher at the time of load connection as will be described later, but is switched to the off state when the voltage becomes lower than the predetermined voltage. Further, it is assumed that the switch portion 9 allows the current to pass only in the direction indicated by the solid arrow in the frame. In this case, the switch unit 9 is actually composed of an electronic switch. Further, D ₁ connected in parallel with the switch unit 9 indicates a diode, and as shown in the figure, it is connected so as to have a conduction direction opposite to that of the switch unit 9. Therefore, when the battery charger 1 is connected to the battery device 1, the charging current flows through the diode D _1, and when the battery device 1 is connected to the load 5, the switch unit 9 is used. A path through which the discharge current of the secondary battery 8 flows is formed.

Reference numeral 10 designates a voltage detecting section capable of detecting the voltage of the secondary battery 8. Then, in the case of the present embodiment, the detection signal of the voltage detection unit 10 is supplied to the switch unit 9 and the remaining amount display circuit 11. That is, it becomes possible to perform on / off control of the switch unit 9 and display control of the remaining battery level based on this detection signal.

Reference numeral 3 is a check switch, which is actually provided on the housing of the battery device 1 as described above with reference to FIG. Reference numeral 11 denotes a remaining amount display circuit for displaying the remaining amount. The remaining amount display circuit 1
1 is actually connected to the negative electrode side of the secondary battery 8 and includes a current detection resistor R ₁ used for remaining amount detection in its circuit. The reference numeral 2 connected to the remaining amount display circuit 11 is a display unit for displaying the remaining amount, and as shown in FIG. 3, the remaining amount is displayed stepwise by, for example, two LEDs. , Is provided so as to be exposed on the housing.

Next, an example of the configuration of the voltage detecting section 10 will be described with reference to FIG. In this figure, 5 indicates a load. That is, this figure shows the case where a load is connected to the battery device 1. Further, 8 is a secondary battery, and 9 is a switch part, which are the same as those shown in FIG. R ₄ connected in series between the switch unit 9 and the ground represents a voltage detecting resistor. C indicates a comparator,
For example, a C-MO that can operate even with very low power consumption
It is composed of an S circuit and the like. A voltage value obtained by dividing the power supply voltage by the resistors R ₂ and R ₃ is input to the inverting input of the comparator C as a reference voltage. Incidentally, as shown in () of the figure, instead of the resistor R ₃ , a Zener diode ZD ₁ having a predetermined Zener voltage can be inserted here to form the reference voltage. On the other hand, the non-inverting input is connected to the connection point between the switch unit 9 and the voltage detecting resistor R ₅ as shown in the figure. That is, the voltage generated across the resistor R _{4 while} the secondary battery 1 is discharging the load 5 is input to the non-inverting input as a detection voltage. Therefore, the resistance values of the resistors R ₂ and R ₃ that set the reference voltage are also set correspondingly. As a result, the comparator C outputs the H level as a detection signal when the secondary battery 8 has a voltage equal to or higher than a preset predetermined voltage,
When the voltage is lower than the predetermined voltage, the L level can be output. Then, this detection signal is input to the switch unit 9 and the remaining amount display circuit 11 (not shown) as shown in the figure. R ₅ represents, for example, a resistor for holding the switch 9 on.

When the voltage detector 10 has the above-mentioned structure,
The switch section 9 is turned on when the detection signal supplied from the comparator C (voltage detection section 10) is at H level, and turned off when it is at L level. Further, in the remaining amount display circuit 11, display control for lighting both the LEDs 2a and 2b or only the LED 2b is performed according to the voltage across the battery, but when the voltage across the battery is extremely low. Therefore, the LED 2a and the LED 2b are both controlled to be turned off.

The configuration of the voltage detection unit 10 is not limited to the above circuit, and various changes can be made as long as the voltage of the secondary battery 8 can be detected. For example, it is conceivable to use a comparator having a hysteresis characteristic as the comparator C, and connect the connection point of the load 5 and the switch unit 9 and the non-inverting input and omit the resistor R _{4 although} not shown. As described above, since the switch unit 9 is actually an electronic switch, it has a so-called ON resistance even in the conductive state. Therefore, in this case, the voltage generated across the switch unit 9 by the on-resistance is used as the detection voltage. As for the operation of the voltage detection unit 10 in this configuration, when the remaining amount of the secondary battery 1 has a margin, the voltage at both ends of the switch unit 9 is higher than the reference voltage, and therefore the H level is output from the comparator C. Then, the switch unit 9 is turned on. Then, when the remaining amount of the secondary battery 1 decreases due to the influence of dark current and the voltage across the switch unit 9 becomes lower than the reference voltage, the output of the comparator C becomes L.
Become a level. As a result, the switch unit 9 is turned off, but when the switch unit 9 is turned off and the load 5 and the ground are cut off, the voltage supplied to the non-inverting input rises again. However, since the comparator C has the hysteresis characteristic as described above, the L level output is held and the switch unit 9 is maintained in the OFF state even if the voltage of the non-inverting input of the comparator C rises. Further, it may be considered that the detection operation described above can be performed by software of a microcomputer.

Therefore, the operation of the battery device 1 of the present embodiment having the above configuration will be described. First, when the charger 4 is connected to the battery device 1 to charge the secondary battery 8, the charging current is supplied from the charger 4, so that the direction of current flow in the battery device 1 is It becomes as shown by arrow A in the figure. Further, in this case, a power supply for operating the voltage detection unit 10 (for example, a power supply for driving the comparator C in the case of FIG. 2).
Is configured to be supplied only when the load 5 is connected, and is not operated when the charger 4 is connected as described above. Therefore, at this time, the switch unit 9 is also turned off. For example, at this time, the current flowing to the secondary battery 8 passes through the resistor R ₁ , but at this time, since the switch unit 9 is in the non-conducting state as described above, in this case, it passes through the diode D ₁ . As a path to the negative electrode 7. This allows
The secondary battery 8 is charged. Further, in the present embodiment, the remaining amount display can be displayed even during charging, and the remaining amount shown in this case means the current charging amount. For example, when the battery device 1 is set in the charger 4 and is being charged, if the check switch 3 is pressed once, the remaining amount display circuit 11 displays a display for a predetermined number of seconds according to the current charge amount. It will operate as done in part 2.

Next, a case where the electronic device, that is, the load 5 is connected to the battery device 1 will be described.
In this case, since the discharge current flows from the secondary battery 8 in the battery device 1 to the load, the current flowing in the battery device 1 is opposite to the arrow B in FIG. It becomes the direction shown in. At this time, the diode D ₁
Is applied with a potential in the opposite direction, and thus becomes non-conductive. Therefore, as the path of the current flowing through the secondary battery 8, it is assumed that the switch unit 9 is in the ON state, and the current flows from the secondary battery 8 to the positive electrode 6 through the switch unit 9 and the resistor R _1. It will be. Therefore, for example, if the electronic device indicated by the load 5 is turned on, the secondary battery 8
Is supplied as a power supply voltage to the circuit of the electronic device indicated by the load 5 to operate the device.

Next, a case will be described in which the battery device 1 is connected to the load 5 (the electronic device concerned) as described above, and the power of the electronic device, which is the load 5, is turned off. For example, in the state as described above, if the power supply voltage of the secondary battery 8 is equal to or higher than the predetermined voltage value, the voltage detection unit 10 outputs the H level detection signal, and thus the switch unit 9 is turned on. And is in conduction. At the same time, since the levels at both ends of the battery are input to the remaining amount display circuit, if the check switch 3 is pressed once at this time, the LEDs 2a, 2
Display control is performed by the remaining amount display circuit 1 so that both b or only the LED 2b are turned on. By the way, in the above-mentioned state, since the load 5 side and the battery device 1 are connected via the plus / minus electrodes 6 and 7, for example, even if the power of the electronic device which is the load 5 is off, the load 5 is dark. Since a current is flowing, this causes a resistance R ₁ from the switch unit 9.
To the secondary battery 8 via. Therefore, the secondary battery 8 is gradually discharged, but the remaining amount thereof is gradually reduced, and the voltage of the secondary battery 8 is also reduced accordingly. During this period, the voltage detection unit 10 continues the detection operation. However, when the voltage of the secondary battery 8 drops below a predetermined value as it falls, the voltage detection unit 10 outputs an L level detection signal instead of the H level. Will be. As a result, the switch unit 9 is turned off, that is, non-conducting, so that the connection between the secondary battery 8 and the load 5 is turned off. Therefore, almost no dark current flows between the load 5 and the battery device 1, and even if the battery device 1 is mounted as it is with the power of the electronic device turned off and left for a long time, the secondary battery 8 is prevented from falling into a deep discharge state.

Incidentally, the voltage detecting section 10 has at least the load 5
As long as it is connected, the voltage detecting unit continues to detect the voltage. However, as described above, the voltage detecting unit 10 is configured to operate with a very small power consumption. The current that should flow in 10 is significantly smaller than the dark current that was flowing in the load 5, so there is no particular problem. Further, although the battery voltage is extremely low, the LEDs 2a and 2b of the display unit 2 are both turned off, that is, a display indicating that the battery device 1 needs to be charged is displayed. For example, if the user presses the check switch 3 once in this state, the LE of the display unit 2
Since both D2a and 2b are not lit, it can be recognized that the battery device 1 needs to be charged.

It is needless to say that the configuration of the embodiment of the battery device of the present invention is not limited to the one described above, and various changes can be made. For example, in the above embodiment, the ON / OFF control of the switch unit 9 and the control relating to the display are possible based on the detection signal of the voltage detecting unit 10, but the portion relating to the remaining amount display (for example, the check switch of FIG. 1). It is also possible to omit 3, the remaining amount display circuit 11, the display unit 2) and to control only the switch unit 9. Further, the present invention is suitable for being applied to a battery device having a built-in nickel cadmium battery having the charging characteristics shown in FIG. 4, but is also applicable to a battery device having another type of secondary battery built therein. .

[0022]

As described above, according to the battery device of the present invention, the switch unit is activated when the voltage of the secondary battery is less than the predetermined value based on the detection signal of the voltage detecting unit which detects the voltage of the secondary battery. By cutting off the path between the secondary battery and the load in the off state, it is possible to prevent the secondary battery from being deeply discharged even when the battery device is attached to the electronic device whose power is off for a long time. As a result, the secondary battery is also prevented from being inactivated, so that it is possible to always obtain a properly charged battery device even after this when the battery is charged. Also,
By configuring the remaining amount display circuit so that the remaining amount can be displayed based on the detection signal of the voltage detection unit, the display operation can be linked with the operation of the switch unit.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an example of the configuration of a voltage detection circuit of this embodiment.

FIG. 3 is a perspective view showing the external appearance of the battery device according to the present embodiment.

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

[Explanation of symbols]

1 Battery Device 2 Display Units 2a, 2b LED 3 Check Switch 4 Charger 5 Load 8 Secondary Battery 9 Switch Unit 10 Voltage Detection Unit 11 Remaining Amount Display Circuit C Comparator D ₁ Diodes R ₁ , R ₂ , R ₃ , R ₄ resistance

Claims (2)

[Claims] 1. A path through which a discharge current of a secondary battery should flow and a path through which a charging current of the secondary battery should flow are respectively provided, and conduction is turned on for a path through which a discharge current of the secondary battery should flow. A switch unit that can be turned on / off is inserted, and a voltage detection unit that can detect the voltage of the secondary battery is provided, and the switch unit determines that the voltage of the secondary battery is predetermined based on a detection signal of the voltage detection unit. A battery device characterized in that it is configured to be turned off when it is lower than a value. 2. The battery device according to claim 1, further comprising a remaining amount display unit configured to perform a remaining amount display of the secondary battery based on a detection signal of the voltage detection unit. .