JPH11185824A - Primary battery compatible battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery that is compatible with a conventional, multipurpose primary battery and has high energy density. SOLUTION: In a battery pack that has a lithium ion secondary battery 2 in its insulating case 1 and is provided with an external terminal composed of a positive electrode terminal Ta and a negative electrode terminal Tb on the outer surface of the insulating case 1, a voltage converter 3 to regulate voltage during charging and discharging of the lithium ion secondary battery 2 and a protective element 4 to prevent overcharging and overdischarging of the lithium ion secondary battery are electrically connected in between the lithium ion secondary battery 2 and the external terminals Ta, Tb.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack in which a lithium ion secondary battery is incorporated in an insulating case, and an external terminal comprising a positive terminal and a negative terminal is provided on the outer surface of the insulating case.

[0002]

2. Description of the Related Art Conventionally, general-purpose primary batteries have been widely used as power supplies for toys and portable electronic devices. As such general-purpose primary batteries, single to single manganese dry batteries or alkaline dry batteries are generally used.

However, these general-purpose manganese dry batteries and alkaline dry batteries cannot be charged in principle, so they cannot be reused after use and must be disposed of. There is a problem that it is not preferable from the viewpoint of environmental protection.

[0004] For this reason, a secondary battery that can be charged and discharged has been widely used in place of these general-purpose primary batteries.

Hitherto, as a widely used secondary battery, a nickel cadmium battery, a nickel hydride battery, or a lithium ion secondary battery has been known.

[0006]

However, nickel-cadmium batteries and nickel-metal hydride batteries are compatible because the output voltage is almost the same as that of general-purpose primary batteries (about 1.0 V to 1.5 V). Therefore, when the battery is charged without completely discharging, the initial discharge capacity is reduced by half. For this reason, there is a problem that the discharge capacity is reduced under actual use conditions in which the discharge is less likely to occur. Further, the nickel cadmium battery and the nickel hydride battery do not have a sufficient energy density, and there is a demand for further improving the energy density.

On the other hand, the lithium ion secondary battery has an advantage that the output voltage is as high as about 3.0 V to 4.2 V, the energy density is higher than that of a nickel cadmium battery or a nickel hydride battery, and the discharge capacity can be further increased. Having. Further, the lithium ion secondary battery has an advantage that the weight can be reduced as compared with the nickel cadmium battery or the nickel hydride battery. However, since it is considerably higher than the output voltage of general-purpose primary batteries,
It could not be used as a general-purpose primary battery compatible battery.

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a secondary battery which is compatible with a conventional general-purpose primary battery and has a large discharge capacity.

[0009]

Means for Solving the Problems The present inventor has provided a lithium ion secondary battery having a high energy density in an insulating case provided with external terminals corresponding to each of a positive electrode and a negative electrode.
By providing a voltage converter for controlling the voltage at the time of charging and discharging, and a protection element for preventing overcharging and overdischarging, the inventors have found that the above-mentioned problems can be solved, and have completed the present invention. .

That is, the present invention relates to a battery pack in which a lithium ion secondary battery is incorporated in an insulating case and an external terminal comprising a positive terminal and a negative terminal is provided on the outer surface of the insulating case. Between the secondary battery and the external terminal, a voltage converter for adjusting the voltage when charging and discharging the lithium ion secondary battery, and protection for preventing overcharging and overdischarging of the lithium ion secondary battery And a primary battery compatible battery pack provided with an element.

The cell voltage of the lithium ion secondary battery built in the primary battery compatible battery pack of the present invention is about 3.0 V to 4.2 V, and the output voltage of the external terminal of the alkaline battery which is a general-purpose primary battery ( About 1.0V to 1.5V)
More than twice as high. Therefore, in the present invention, the cell voltage (about 3.0 V-
4.2 V) is converted to about 1.0 V to 1.4 V, and a voltage converter having a function of outputting to the external terminal side is built in the insulating case. The voltage converter adjusts the external terminal voltage at the time of discharge to about 1.0 V to 1.4 V. Such a voltage converter has a function to inevitably triple the current when the voltage of the lithium ion secondary battery is reduced to one third.

The charge voltage of a nickel-cadmium battery or a nickel-metal hydride battery is generally about 1.5V. Therefore, in the present invention, in order to allow charging using a NiCd battery or a nickel-metal hydride battery charger, the external terminal voltage at the time of charging using a NiCd battery or a nickel-metal hydride battery charger is about 1%. 0.5V to about 3.0V to 4.2V,
It is preferable to incorporate a voltage converter having a function of outputting to the lithium ion secondary battery side. As the voltage converter, the lithium ion secondary battery side voltage at the time of charging was 4.2 V
It is preferable to incorporate what is adjusted below.

Therefore, in the present invention, the voltage converter converts the voltage of the lithium ion secondary battery to approximately one third at the time of discharging and outputs the voltage to the external terminal side, and at the time of charging, converts the voltage of the external terminal side to approximately three. A first voltage conversion element for converting the voltage to twice and outputting the same to the lithium ion secondary battery, and a second voltage conversion element for controlling the voltage of the lithium ion secondary battery to not exceed about 4.2 V during charging. And a third voltage conversion element for controlling the voltage on the external terminal side not to exceed 1.5 V during discharging.

Further, in the present invention, an overvoltage charging protection function for preventing the voltage on the lithium ion secondary battery side from exceeding about 4.2 V, and a function for preventing the voltage on the lithium ion secondary battery side from falling below about 3 V. A protection element having an overvoltage discharge protection function is provided.

In the present invention, when a case having the same outer dimensions as a general-purpose primary battery is used as the insulating case, it can be used as a general-purpose primary battery. For example, it can be used instead of AA batteries.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the primary battery compatible battery pack of the present invention will be described in detail.

As shown in FIG. 1A, this primary battery compatible battery pack 10 has the same outer dimensions as a general-purpose battery and an insulating case 1 made of an insulating material such as plastic.
The positive electrode terminal T made of a good conductor such as copper or nickel alloy
a and a negative electrode terminal Tb. Its internal configuration prevents overcharge and overdischarge of the lithium ion secondary battery 2, the voltage converter 3 for adjusting the voltage when charging and discharging the lithium ion secondary battery 2, and the lithium ion secondary battery. (See FIG. 1 (b)).

As shown in FIG. 2, the voltage converter 3 incorporated in the battery pack 10 converts the output voltage of the lithium ion secondary battery 2 to one third at the time of discharging and outputs it to the external terminal side. And a first voltage conversion element 3a for converting the input voltage from the external terminal side to three times during charging and outputting the converted voltage to the lithium ion secondary battery 2, and a voltage on the lithium ion secondary battery 2 side during charging. Voltage conversion element 3b for controlling the voltage not to exceed 4.2 V, and a third voltage conversion element for controlling the voltage of the external terminal to not exceed about 1.5 V during discharging. 3c.

The protection element 4 has a protection function of overvoltage charging for preventing the voltage on the lithium ion secondary battery 2 side from exceeding about 4.2 V during charging, and a protection function for lithium ion secondary battery during discharging. Overvoltage discharge protection function to prevent the voltage on the side from falling below about 3V.

As the voltage converter 3 or each of the voltage conversion elements (3a, 3b, 3c) and the protection element 4 described above, known elements can be used.

The battery pack 10 shown in FIG. 2 starts discharging when the battery pack 10 is connected to the electronic device main body 5 and the power supply of the main body 5 is turned on. When the battery pack 10 is connected to the charger 6 and the power of the charger is turned on, charging starts. Hereinafter, the operation of each component will be described in detail along with the discharging operation and the charging operation of the battery pack. First, the discharging operation and the charging operation of the battery pack will be described.

(1) Operation at Discharge The battery pack 10 is connected to the electronic device main body 5 serving as a load, and the power of the main body 5 is turned on. Then, the voltage (about 4.2 V) of the lithium ion secondary battery 2 is reduced to one third and the current is tripled by the first voltage conversion element 3 a, and a voltage of about 1.4 V is output. . Next, the output voltage is controlled to about 1.5 V or less by the third voltage converter 3c and output to the external terminals Ta and Tb.

(2) Operation during Charging The battery pack 10 is connected to the dedicated charger 6. A voltage of about 1.5 V is applied between the external terminals Ta and Tb from the charger 6, and the charging voltage is tripled by the first voltage conversion element 3a to output a voltage of about 4.5V. . Next, the voltage is converted to about 4.2 V by the second voltage converter 3b, and the lithium ion secondary battery 2 is charged. Therefore, when the battery pack 10 is connected to a charger for a nickel-cadmium battery, the output voltage of the charger is about 1.5 V, so that the battery can be charged in the same manner as a dedicated charger.

Next, the operation of each element constituting the battery pack will be described in detail.

(A) Function of First Voltage Conversion Element The first voltage conversion element 3a has an external terminal voltage of 1.1.
Voltage of the lithium ion secondary battery (about 4.2 V) for a certain period of time when the voltage is below V or above 1.5 V.
Is reduced to one third (approximately 1.4 V) and the current is tripled. As shown in FIG. 3, voltage conversion is performed by connecting three capacitors (C1, C2, C
3) is performed by directly connecting each to the external terminal side. Therefore, the voltage is reduced to one third and the current capacity is tripled. The first voltage conversion element 3a stops the operation of voltage conversion when the voltage on the external terminal side is 1.1 V to 1.5 V, so that no extra current is consumed.

The first voltage conversion element 3a converts the voltage during charging and discharging based on the same action, so that there is no need to switch the operation between charging and discharging.

The operation of the first voltage conversion element 3a at the time of discharging will be described in more detail with reference to FIG. The switching control can be performed by a known control circuit.

(Operation at the time of discharging the first voltage conversion element 3a) When the battery pack is connected to the main body and the discharge is started, the external terminal voltage becomes 1.1V or less, and the control circuit switches the switches SW1 to SW1 for voltage conversion. The operation of SW4 is started as follows. First, when the switch SW1 is turned on, a voltage of about 4.2 V of the lithium ion secondary battery is applied to the capacitors C1, C2, and C3 connected in series, and about 1.4V is applied to both sides of each capacitor. Is generated. Accordingly, the voltage of the lithium ion secondary battery (about 4.2 V) is converted to one third, and the voltages of the capacitors C1, C2, and C3 become about 1.4 V, respectively.

Next, when the switch SW2 is turned on after the switch SW1 is turned off, the capacitor C1
(Approximately 1.4V) is applied to the capacitor C5, and the voltage becomes approximately 1.4V.

Next, when the switch SW3 is turned on after the switch SW2 is turned off, the capacitor C2
(Approximately 1.4V) is applied to the capacitor C5, and the voltage becomes approximately 1.4V.

Next, when the switch SW4 is turned on after the switch SW3 is turned off, the capacitor C3
(Approximately 1.4V) is applied to the capacitor C5, and the voltage becomes approximately 1.4V.

Next, the switch SW4 is turned off. Thereafter, the same operation is repeated from the beginning.

(Operation at the time of charging the first voltage conversion element 3a) When the battery pack is connected to the charger, the external terminal voltage becomes 1.5 V or more, and the control circuit operates the switches SW1 to SW4 for voltage conversion. Is started as follows. First, when the switch SW2 is turned on, the voltage (about 1.5 V) of the capacitor C5 on the external terminal side is applied to the capacitor C1. At this time, the voltage of the capacitor C1 becomes about 1.5V. Next, after the switch SW2 is turned off, the switch SW3 is turned on, and the voltage of the external terminal side capacitor C5 of about 1.5 V
2 is applied. At this time, the voltage of the capacitor C2 becomes about 1.5V.

Next, after the switch SW3 is turned off, the switch SW4 is turned on, and a voltage of about 1.5 V of the capacitor C5 on the external terminal side is applied to the capacitor C3. At this time, the voltage of the capacitor C3 is about 1.5 V
become.

Next, after the switch SW4 is turned off, the switch SW1 is turned on, and a voltage of about 4.5 V is applied to both sides of the series-connected capacitors C1, C2, and C3. Applied to the next battery side. This means that the voltage (about 1.5 V) applied to each of the capacitors C1, C2, and C3 has tripled.

Next, the switch SW1 is turned off.
Thereafter, the same operation is repeated from the beginning.

(Operation of Second Voltage Conversion Element 3b) When the voltage of the first voltage conversion element 3a on the lithium ion battery side is higher than about 4.2 V, the voltage on the lithium ion secondary battery side is about 4. In order not to exceed 2 V, as shown in FIG. 4, the charging current is controlled on / off by a control circuit. That is, the voltage on the lithium ion secondary battery side is about 4.2
When it becomes larger than V, the gate voltage of the FET is set to 0V.
To shut off the charging current. Therefore, at the end of charging,
The voltage of the lithium ion secondary battery stabilizes at about 4.2V,
The FET periodically repeats the on / off operation until it is fully charged.

(Operation of Third Voltage Conversion Element 3c) When the voltage at the external terminal of the first voltage converter 3a is higher than about 1.5 V, the voltage at the external terminal does not exceed about 1.5 V. In order to achieve this, as shown in FIG. 5, the control circuit controls the on / off of the discharge current. That is, the first voltage converter 3a
When the voltage of the external terminal exceeds about 1.5 V, the discharge voltage is cut off by setting the gate voltage of the FET to 0 V. Therefore, the first voltage converter 3a breaks down and the voltage on the external terminal side of the first voltage converter 3a becomes about 1.
If it is higher than 5V, the FET periodically repeats the on / off operation.

(B) Function of protection element (overcharge protection function) When the voltage of the lithium ion secondary battery is higher than about 4.2 V, the voltage on the lithium ion secondary battery side is set to about 4.2 V or less. As shown in FIG. 6, the charging current is cut off. If the second voltage conversion element 3b
Failed and the voltage on the lithium ion secondary battery side was about 4.
If it exceeds 2V, FET1 for charging current interruption
The charging current is cut off by setting the gate voltage at 0 V to 0 V.

(Overdischarge protection function) When the voltage of the lithium ion battery is smaller than about 3 V, the discharge is stopped.
Cut off the discharge current. If the voltage on the lithium ion secondary battery side becomes lower than about 3 V at the end of discharge, the gate voltage of the discharge current interrupting FET 2 is set to 0 V, and the discharge current is interrupted.

Although the primary compatible battery pack of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the present invention can be applied to a battery pack having an external terminal voltage higher than that of a lithium ion secondary battery. For example, if a voltage converter for converting the voltage of a lithium ion secondary battery to more than twice is built in, a battery of an external terminal having an output voltage higher than a cell voltage of 3 to 4 V in one cell in one cell Pack can be realized.
For example, a battery pack compatible with a 9 V box-shaped primary battery 006P can be realized with one cell.

[0042]

The primary battery compatible battery pack of the present invention has a higher output voltage than a nickel-metal hydride battery and has a built-in lithium ion secondary battery having a high energy density. Since the battery is provided with the protection element, it can be compatible with a general-purpose primary battery, such as an alkaline AA battery, and can be charged using a general charger for a nickel-metal hydride battery.

A lithium ion secondary battery built in a primary battery compatible battery pack does not have a memory effect unlike a nickel hydrogen battery. Therefore, the battery pack of the present invention can be fully charged even if charged during the course of discharging, and can secure a sufficient discharging capacity.

The self-discharge amount of the lithium ion secondary battery is smaller than that of the nickel hydrogen battery. Therefore, the battery pack of the present invention has excellent capacity retention characteristics after charging. In addition, a lithium ion secondary battery has a lower specific gravity than a nickel hydride battery, and can be reduced in weight.

[Brief description of the drawings]

FIG. 1 is an external view (FIG. 1 (a)) and an internal configuration diagram (FIG. 1 (b)) of a primary battery compatible battery pack of the present invention.

FIG. 2 is a block diagram of a voltage converter used in the present invention.

FIG. 3 is a circuit diagram of a first voltage conversion element constituting a voltage converter used in the present invention.

FIG. 4 is a circuit diagram of a second voltage conversion element constituting a voltage converter used in the present invention.

FIG. 5 is a circuit diagram of a third voltage conversion element constituting a voltage converter used in the present invention.

FIG. 6 is a circuit diagram of a protection element used in the present invention.

[Explanation of symbols]

1. Insulation case, 2. Lithium ion secondary battery, 3. Voltage converter, 4. Protective element

Claims (2)

[Claims] 1. A battery pack in which a lithium ion secondary battery is built in an insulating case, and an external terminal comprising a positive terminal and a negative terminal is provided on an outer surface of the insulating case. A voltage converter for adjusting the voltage during charging and discharging of the lithium ion secondary battery and a protection element for preventing overcharging and overdischarging of the lithium ion secondary battery are provided between the external terminals. A primary battery compatible battery pack characterized in that: 2. The method according to claim 1, further comprising: converting a voltage of the lithium ion secondary battery to approximately one-third during discharging and outputting the voltage to an external terminal; A first voltage conversion element for outputting to the battery side;
When charging, the voltage on the lithium ion secondary battery side is about 4.2V
And a third voltage conversion element for controlling the voltage of the external terminal during discharge so as not to exceed 1.5 V. Item 1. A primary battery compatible battery pack according to Item 1.