JPH11178218A - Feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the residual capacity of each secondary battery of a feeding device by the use of a plurality of secondary batteries in combination for a common load. SOLUTION: In a feeding device, switch elements 21 and 31 are respectively connected in series between secondary batteries 11 and 12 and a load 1 and a circuit 14, which measures the voltage of the batteries 11 and 12 and displaying elements 21 and 31 which respectively display the remaining capacities of the batteries 11 and 12 are provided. When the feeding device is used, the voltage of the batteries 11 and 12 are supplied to the load 1 by turning on/off the switch elements 21 and 31. When prescribed operation is made, only one of the switch element 21 or 31 is turned on, and the other switch element 31 or 21 is turned off. The voltage of the battery 11 or 12 corresponding to the turned-on element 21 or 31 is measured by means of the circuit 41, and the measured results are displayed by means of the displaying elements 46 and 47.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for supplying power from a plurality of secondary batteries to a common load.

[0002]

2. Description of the Related Art For example, as shown in FIG. 3, two battery packs 11 and 12 are housed as an external power supply device 10 of a video camera 1 and the output voltage is supplied to the video camera 1 through a cable 2. In some cases, long-time shooting outdoors or the like is made possible.

In this case, the battery packs 11 and 12 are the same, but can be used alone as a power source for the video camera 1.

When the battery packs 11 and 12 are used together, the power supply 10 is provided with a battery pack as shown in FIG. Between the power input terminals Ta and Tb to which the power supply terminals 11 and 12 are connected and the common power output terminal To;
Diodes D1 and D2 for backflow prevention are connected. The terminals Tc, Td and Tg are an input terminal and an output terminal on the ground side.

Conventionally, nickel cadmium batteries and nickel-metal hydride batteries have been generally used as power sources for the above-mentioned video cameras. Recently, lithium-ion batteries and lithium-ion batteries having higher capacity and higher energy density have been used. Batteries are being used.

This lithium ion battery has a nominal voltage of 3.6 V, three times higher than the nominal voltage of a nickel cadmium battery or a nickel hydride battery, and a charge / discharge cycle life of 1200 times. It is more than twice as long as 500 times for nickel-metal hydride batteries.

As shown in FIG. 5, the discharge characteristics of a lithium ion battery have a steeper gradient than that of a nickel cadmium battery or a nickel hydride battery, and exhibit a monotonically decreasing characteristic.

Therefore, in the power supply apparatus 10 shown in FIG. 4, first, power is supplied to the video camera 1 from one of the two battery packs 11 and 12 having a higher terminal voltage, for example, the battery pack 11. When the power supply proceeds, when the terminal voltage of the battery pack 11 decreases and becomes equal to the terminal voltage of the battery pack 12, power is supplied to the video camera 1 from both the battery packs 11 and 12.

[0009]

The capacity of a lithium-ion battery is defined as the amount of discharge until the terminal voltage per unit cell reaches, for example, a reference voltage Vst of about 3 V (see FIG. 5). When the terminal voltage per unit cell becomes equal to or lower than the reference voltage Vst, power cannot be stably supplied to the load, and a so-called dead battery condition occurs.

Therefore, if a user of a portable electronic device such as a video camera can easily know the remaining capacity of the secondary battery, the user can know the timing of replacement in advance and can use the electronic device in a planned manner. Becomes possible.

However, for a common load, two 2
When the secondary batteries are used in combination, as described above, there are cases where power is supplied independently and cases where two batteries are supplied simultaneously, according to the level relationship between the terminal voltages. In the latter case, two secondary batteries are connected in parallel. At this time, since the terminal voltages affect each other, each terminal voltage cannot be measured correctly, and The remaining capacity of the next battery cannot be displayed correctly.

The present invention is intended to solve such a problem.

[0013]

Therefore, according to the present invention, in a power supply apparatus for supplying voltages of a plurality of secondary batteries each exhibiting a monotonically decreasing discharge characteristic to a common load, the plurality of secondary batteries are provided. A plurality of switch elements respectively connected in series between the load, a circuit for measuring the voltage of the secondary battery, and a display element for displaying the remaining amount of each of the plurality of secondary batteries. In use, the plurality of switch elements are turned on / off to supply the voltage of the plurality of secondary batteries to the load, and when a predetermined operation is performed, one of the plurality of switch elements is used. Are sequentially turned on, the remaining switch elements are turned off, and of the plurality of secondary batteries, the voltage of the secondary battery corresponding to the turned on switch element is measured by the circuit, and the measurement result is obtained. Up It is an added showing the display device power supply apparatus. Therefore, the terminal voltages of the plurality of secondary batteries are measured independently and sequentially, and the remaining amounts are displayed according to the measurement results.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
It has first and second power supply circuits 20, 30 corresponding to the first and second battery packs 11, 12, respectively, and has a control circuit 40 for controlling both power supply circuits 20, 30.

In the first power supply circuit 20,
First power input terminal Ta to which battery pack 11 is connected
Is connected to the drain of the switching FET 21 and its source is connected to the power output terminal To. Also, FE
The gate of T21 is a control FET through a resistor 26.
The source is connected to the power input terminal Tc on the ground side.

Further, when the resistors 27 and 28 are connected in series between the power supply input terminals Ta and Tc and the battery pack 11 is connected, the divided voltage V11 is taken out. To the non-inverting input terminal of the operational amplifier 23. When the resistors 48 and 49 are connected in series between the power supply output terminal To and the ground terminal Tg and an output voltage is obtained at the terminals To and Tg, the divided voltage V10 is obtained.
And the divided voltage V10 is supplied to the inverting input terminal of the operational amplifier 23. Then, the output voltage of the operational amplifier 23 is supplied to the gate of the FET 22.

Further, the second power supply circuit 30 has the same configuration as the first power supply circuit 20.
In the part corresponding to 0, reference numeral 3 is used instead of reference numerals 21 to 28.
The description is omitted by attaching 1 to 38. The power supply circuit 2
At 0 and 30, the corresponding elements have equal characteristics. Also, the resistors 27, 28, 37, 38, 48, 49
Are equal to each other. Further, resistors 37 and 38
Is a voltage V12.

The control circuit 40 includes a microcomputer 41, a switch 45, and two LEDs 46 and 47.
It is composed of That is, the power input terminal Ta,
Tb is connected to the input terminal of the three-terminal regulator 42 through the diodes 43 and 44, and the ground terminal is connected to the terminals Tc and Td. Thus, the battery pack 1
When the terminals 1 to 12 are connected to the terminals Ta, Tc to Tb, Td, a constant DC voltage, for example, a DC voltage of 5 V is taken out from the three-terminal regulator 42, and this voltage is supplied to the power terminal Vc of the microcomputer 41. It is supplied as a voltage.

Further, a power input terminal Ta and a ground terminal T
c, resistors 51 and 52 are connected in series, and the divided voltage obtained at the connection midpoint is connected to a microcomputer 41.
Analog input terminal (input terminal of a built-in A / D converter) Aa. Similarly, resistors 53 and 54 are connected in series between the power input terminal Tb and the ground terminal Td,
The divided voltage obtained at the connection midpoint is supplied to the analog input terminal Ab of the microcomputer 41.

A pull-up resistor 55 and a switch 45 are connected in series between the output terminal of the three-terminal regulator 42 and the ground terminal Td. Connected to. The switch 45 is a non-lock type normally open switch.

Further, output terminals Oa and Ob of the microcomputer 41 are connected to the gates of the FETs 24 and 34, and a display element is provided between the output terminal of the three-terminal regulator 42 and the output terminals Oc and Od of the microcomputer 41. LEDs 46 and 47 are current limiting resistors 56 and 57
Connected through.

The battery packs 11 and 12 are, for example,
Each is composed of two lithium ion batteries connected in series and has a nominal voltage of 7.2V.

In such a configuration, the battery pack 11
Is connected to the terminals Ta and Tc, the divided voltage V11 of the output voltage and the divided voltage V10 of the output voltage of the output terminals To and Tg are compared in the operational amplifier 23. Then, at this time, the output voltages of the terminals To and Tg become 0
Therefore, V11> V10, and the output of the operational amplifier 23 becomes "H" level. As a result, the FET 22 is turned on, the FET 21 is turned on, and the terminal voltage of the battery pack 11 is output to the terminals To and Tg through the FET 21.

When the terminal voltage of the battery pack 11 is output to the terminals To and Tg, the voltage V10 increases. However, the voltages at the terminals To and Tg are lower by the voltage drop between the drain and source of the FET 21. , V11> V10, and the ON state of the FET 21 continues. Therefore, when the battery pack 11 is connected to the terminals Ta and Tc, the terminal voltage is continuously output to the terminals To and Tg.

Also, only the battery pack 12 has terminals Tb and Tb.
Similarly, when the terminal is connected to the terminal d, the terminal voltage is continuously output to the terminals To and Tg.

Further, when both battery packs 11 and 12 are connected, if the terminal voltage of one battery pack, for example, battery pack 11 is higher than the terminal voltage of battery pack 12, this battery pack 11 Are at terminals To and T
By output to g, V12 <V10. As a result, the output of the operational amplifier 33 becomes “L” level and the FE
Since T32 is turned off, the FET 31 is also turned off.

When the terminal voltage of the battery pack 12 is higher than the terminal voltage of the battery pack 11,
ET31 is turned on, and FET21 is turned off.

Therefore, both battery packs 11, 12
Is connected, the battery pack with the higher terminal voltage is used.

As the battery pack 1 is used, both battery packs 1
When the terminal voltages of the terminals 1 and 12 become equal, V11> V10, V12
> V10, the outputs of the operational amplifiers 23 and 33 are both at the "H" level.
31 is turned on, and both battery packs 11 and 12 are used.

Thus, in the power supply apparatus 10, when one of the battery packs 11 and 12 is connected, the battery pack is used. When both are connected, the battery pack with the higher terminal voltage is used first, and then when both terminal voltages are equal, both are used. Thus, the battery packs 11 and 12 are used.

Further, when the switch 45 is pressed,
The remaining capacity of the battery packs 11 and 12 is
1 is measured as follows, and the measurement result is LE
Displayed by D46 and D47.

That is, when only the battery pack 11 is connected, the terminal voltage is divided by the resistors 27 and 28 and supplied to the terminal Aa of the microcomputer 41. 11 is connected and its terminal voltage can be known. Similarly, the microcomputer 41
When only the battery pack 12 is connected, it is possible to know that only the battery pack 12 is connected and the terminal voltage thereof.

When the user presses the switch 45,
The switch output changes from “H” level to “L” level, which is the terminal Ct of the microcomputer 41.
Supplied to Then, in the microcomputer 41, first, the connection state of the battery packs 11 and 12 is determined.

For example, when only the battery pack 11 is connected, the remaining amount of the battery pack 11 is measured according to the divided voltage supplied to the terminal Aa, and the output terminal Oc is determined according to the measurement result. Is controlled, and the lighting of the LED 46 is controlled in accordance with the remaining amount of the battery pack 11.

That is, for example, when the remaining amount of the battery pack 11 is sufficient, the LED 46 is lit continuously for, for example, seven seconds. When the remaining amount is slightly low, for example, as shown in FIG. 2A, the light is blinked only three times in a short cycle TL, and this blink is repeated for seven seconds in a long cycle Tr.

Further, when the remaining amount is smaller, for example, as shown in FIG. 2B, the light is blinked only twice in a short cycle TL, and this blink is repeated for seven times in a long cycle Tr.
Repeated over seconds. Further, when there is almost no remaining amount, the light is turned on once only once, and this lighting is repeated at a long cycle Tr. When there is no remaining amount, the LED 46 does not light.

In this way, the lighting of the LED 46 is controlled according to the remaining amount of the battery pack 11, and the remaining amount is notified to the user. Also, when only the battery pack 12 is connected, the
The lighting of 47 is similarly controlled, and the remaining amount is notified to the user.

Further, when both the battery packs 11 and 12 are connected, first, the terminal 0b is set to the "H" level to turn on the FET 34, thereby irrespective of the output level of the operational amplifier 33. The FET 32 is turned off, and the FET 31 is also turned off. Therefore, the battery pack 12 will be operated regardless of the remaining amount of the battery pack 12 thereafter.
Is not output to the terminals To and Tg.

As a result, regardless of the remaining amount of the battery pack 11, V11> V10, the FET 21 remains on, and the terminal voltage of the battery pack 11 is output to the terminals To and Tg. Therefore, the battery pack 11
Indicates that the video camera 1 is in a load state.

Subsequently, the terminal voltage of the battery pack 11 at this time is measured by the microcomputer 41 through the resistors 51 and 52, and according to the measurement result, the remaining amount of the battery pack 11 is determined by the lighting state of the LED 46 as described above. Is displayed. At this time, since the FET 31 is off, the terminal voltage of the battery pack 12 does not affect the measurement result.

When this display is performed for, for example, seven seconds, the FET 34 is turned off and the FE
T24 is turned on, so that the terminal voltage of the battery pack 12 is output to the terminals To and Tg.

Subsequently, the terminal voltage of the battery pack 12 at this time is measured by the microcomputer 41 through the resistors 53 and 54, and according to the measurement result, the remaining amount of the battery pack 12 depends on the lighting state of the LED 47 as described above. , For example, for 7 seconds. At this time, since the FET 21 is off, the terminal voltage of the battery pack 11 does not affect the measurement result.

After the above display is performed,
The device 10 returns to the state before the switch 45 was pressed.

Thus, according to the power supply device 10, even when both the battery packs 11 and 12 are connected, when measuring the remaining amount of one, the other connection is turned off. Can be independently and accurately measured.

In the above description, two battery packs are used. However, three or more battery packs may be used. In this case, the number of power supply circuits and the number of LEDs may be the same as that of the battery packs. The present invention can be similarly applied to a case where a plurality of secondary batteries are used in an electronic device such as a notebook personal computer.

[0046]

According to the present invention, when a plurality of secondary batteries are used together for a common load, the terminal voltage of each secondary battery can be correctly measured, and the remaining capacity can be correctly determined. Can be displayed.

[Brief description of the drawings]

FIG. 1 is a connection diagram illustrating one embodiment of the present invention.

FIG. 2 is a diagram for explaining the present invention.

FIG. 3 is a conceptual diagram for explaining the present invention.

FIG. 4 is a connection diagram for explaining the present invention.

FIG. 5 is a characteristic diagram for explaining the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Video camera, 2 ... Cable, 10 ... Power supply device, 1
1 and 12: Battery pack, 20 and 30, Power supply circuit, 21, 22, 24, 31, 32, and 34: FE
T, 23 and 33: operational amplifier, 40: control circuit, 4
DESCRIPTION OF SYMBOLS 1 ... Microcomputer, 42 ... 3-terminal regulator, 45 ... Operation switch, 46 and 47 ... LED

Claims (1)

[Claims] 1. A power supply device for supplying a voltage of a plurality of secondary batteries each exhibiting a monotonically decreasing discharge characteristic to a common load, wherein a series connection is made between the plurality of secondary batteries and the load. A plurality of switch elements, a circuit for measuring the voltage of the secondary battery, and a display element for displaying the remaining amount of each of the plurality of secondary batteries. Is turned on and off to supply the voltages of the plurality of secondary batteries to the load, and when a predetermined operation is performed, only one of the plurality of switch elements is sequentially turned on, and the remaining switch elements are turned on. A power supply device that is turned off, of the plurality of secondary batteries, measures the voltage of the secondary battery corresponding to the turned on switch element by the circuit, and displays the measurement result on the display element. .