JP4133735B2 - Battery pack - Google Patents

Description

  The present invention relates to a battery pack for a secondary battery such as a lithium ion battery.

  Since an electronic device using a battery pack usually requires several types of power supply voltages, a plurality of voltage converters are provided in the main body of the electronic device, and step-up / step-down is performed by a voltage converter, for example, a DC-DC converter. And generating the required multiple voltages. Similarly, at the time of charging the secondary battery pack, the output voltage of the charger (AC adapter) is stepped up / stepped down using the DC-DC converter of the electronic device main body.

  For example, Patent Literature 1 below discloses a battery pack that outputs a constant voltage by combining a secondary battery and a step-down voltage converter.

Japanese Patent Laid-Open No. 7-7864

  FIG. 4 shows the relationship between a conventional battery pack and an electronic device body. Reference numeral 1 indicates a battery pack, and reference numeral 10 indicates an electronic apparatus main body. The electronic device main body 10 includes a discharge circuit 11. The battery pack 1 includes a secondary battery 2, a protection circuit (IC circuit) 3, a discharge control FET 4, a charge control FET 5, and parasitic diodes 6 and 7 of these FETs 4 and 5, respectively. .

  The secondary battery 2 is a lithium ion battery, a lithium polymer battery, a nickel metal hydride battery, a nickel cadmium battery, a lithium metal battery, or the like. In the case of a lithium ion battery, for example, a prismatic battery is used, and the secondary battery 2 is entirely covered with an iron battery can. In the case of a lithium polymer battery, the battery is sealed with an aluminum laminate film.

  Since the lithium ion battery is vulnerable to overcharge and overdischarge, the battery cell and the protection circuit are integrated into a battery pack. The function of the protection circuit 3 has three functions of overcharge protection, overdischarge protection, and overcurrent protection. These protection functions will be briefly described.

The overcharge protection function will be described. When a lithium ion battery is charged, the battery voltage continues to rise even after full charge. If this overcharge state occurs, there is a possibility that a dangerous state will occur. Therefore, the charging is carried out at a constant current constant voltage charging control voltage needs to perform the following rating (e.g. 4.2V) of the battery. However, there is a risk of overcharging due to the failure of the charger or the use of a different model charger. When overcharged and the battery voltage exceeds a certain voltage value, the protection circuit turns off the charge control FET 5 and cuts off the charging current. This function is an overcharge protection function.

  The overdischarge protection function will be described. When the battery is discharged to a rated discharge end voltage or lower and the battery voltage is in an overdischarged state of, for example, 2 V to 1.5 V or lower, the battery may fail. When discharged and the battery voltage falls below a certain voltage value, the protection circuit turns off the discharge control FET 4 and cuts off the discharge current. This function is an overdischarge function.

  The overcurrent protection function will be described. When the + and-terminals of the battery are short-circuited, a large current flows and there is a risk of abnormal heat generation. When the discharge current flows over a certain current value, the protection circuit turns off the discharge control FET 4 and cuts off the discharge current. This function is an overcurrent protection function.

The discharging DC-DC converter 12 and the charging DC-DC converter 13 of the electronic device main body 10 are connected to the external terminals of the battery pack 1 described above. The discharge DC-DC converter 12 stabilizes the battery voltage taken out to the external terminal to a predetermined output voltage and supplies it to the discharge circuit 11 through the discharge terminal 14 and the ground terminal 15.

  The charging voltage supplied from the charger 17 is input to the charging terminal 16 and the ground terminal 15 to the charging DC-DC converter 13. The output voltage set to the rated charging voltage value by the charging DC-DC converter 13 is supplied to the secondary battery 2 of the battery pack 1 via the external terminal.

FIG. 5 shows another configuration example of the connection relationship between the conventional battery pack and the electronic device main body 10 . The difference from the configuration of FIG. 4 is that the charging DC-DC converter 12 is built in the battery pack 1.

FIG. 6 shows still another configuration example of the connection relationship between the conventional battery pack and the electronic device main body 10 . The difference from the configuration of FIG. 4 is that the discharge DC-DC converter 13 is built in the battery pack 1.

  As described above, since the conventional secondary battery pack uses the charging DC-DC converter 12 and the discharging DC-DC converter 13 separately, two DC-DC converters are required. did. Therefore, there is a drawback that the cost is increased and a part arrangement place is required. In addition, since the electronic device main body has a DC-DC converter, there is a concern about the influence of noise generated by the DC-DC converter, and it is necessary to consider countermeasure circuits and the like.

  Accordingly, an object of the present invention is to use both a voltage converter for charging and a discharge, reduce the cost and reduce the location of parts, and further, the electronic device body has a voltage conversion circuit such as a DC-DC converter. It is an object of the present invention to provide a battery pack that can reduce the influence of radiation noise generated from a voltage conversion circuit.

In order to achieve the above-described problem, the present invention provides a battery pack having a built-in secondary battery.
A charge input terminal and a discharge output terminal;
A bidirectional and switching DC-DC converter housed in a case together with a secondary battery and mounted on the same substrate as the protection circuit of the secondary battery;
First switch means for switching the input to the DC-DC converter between the secondary battery side and the charge input terminal side, and second switch means for switching the output of the DC-DC converter between the discharge output terminal side and the secondary battery side The DC-DC converter is switched between a charging mode configured to supply a charging voltage to the secondary battery and a discharging mode that outputs a predetermined discharge voltage obtained by converting the voltage of the secondary battery. Switching means for
Control signal generating means for generating a control signal for controlling the switching means,
The control signal generating means identifies a regular charger, and generates a control signal for the switching means to switch the DC-DC converter to the charging mode only when the regular charger is connected. It is a pack.

  In this invention, one voltage converter has functions for charging and discharging, and since these functions are switched by the switching means, compared to having separate voltage converters for charging and discharging, Costs can be reduced, and it is unnecessary to have a voltage converter in the electronic device body. Furthermore, in the electronic device body or the battery pack, the space required for installing the voltage converter can be narrowed.

  When a DC / DC converter is used as the voltage converter, radiation noise is generated by switching control at a high frequency of 10 kHz to 2 MHz. In this invention, by having a DC / DC converter as a voltage converter inside the battery pack, the distance between the internal circuit of the electronic device and the DC / DC converter can be increased, and the influence of noise on the internal circuit of the electronic device is suppressed. it can. Further, by incorporating a voltage converter in the battery pack, high frequency electromagnetic wave noise can be reduced by an iron battery can in a rectangular battery or an aluminum laminate film in a lithium polymer battery.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the connection configuration of the first embodiment of the present invention. Parts corresponding to those of the conventional configuration described above are shown with the same reference numerals. That is, the battery pack 1 includes the secondary battery 2 and the protection circuit 3, and the discharge control FET 4 and the charge control FET 5 are controlled by the output of the protection circuit 3. The electronic device main body 10 includes a discharge circuit 11 that requires a DC power supply.

  Discharge circuit 11 is connected to discharge output terminal 14 and ground terminal 15. Although not shown, the external charger 17 supplies a charging voltage of, for example, 5 V between the charging terminal 16 and the ground terminal 15 using an AC 100 V of a household power supply (commercial power supply) as a DC voltage.

  Reference numeral 21 is a DC-DC converter. In order to obtain a plurality of discharge output voltage values other than the DC-DC converter 21, another DC-DC converter may be provided. The DC-DC converter 21 is built in a relatively hard case made of a material such as plastic together with the secondary battery 2 and the protection circuit 3. Specifically, for example, the DC-DC converter 21 and the protection circuit 3 are mounted on a substrate, and the secondary battery 2 is disposed adjacent to the substrate. Note that the DC-DC converter 21 may be disposed in the exterior case of the secondary battery 2 together with the power generation element.

  The DC-DC converter 21 is a circuit that generates a stabilized output voltage having a value different from the input voltage (battery voltage). As the DC-DC converter 21, ones having various configurations can be used. That is, a charger pump system using a capacitor and a switch element, a step-up converter (step-down converter) using a diode, an inductor, a capacitor, and a switch element, or a switching regulator using a transformer and a switch element can be used. Furthermore, a piezoelectric inverter using a piezoelectric transformer or a series regulator using a bipolar transistor element may be used. As a charger pump type DC-DC converter and switching regulator, a very small one of about 4 mm square has been developed, and it is relatively easy to incorporate the DC-DC converter 21 together with the protection circuit 3 in the battery pack. .

  An input terminal of the DC-DC converter 21 is connected to the charging terminal 16 via the switch SW1, and an output terminal thereof is connected to the positive electrode of the secondary battery 2 via the switch SW2. The input terminal of the DC-DC converter 21 is connected to the positive electrode of the secondary battery 2 via the switch SW11, and the output terminal is connected to the discharge output terminal 14 via the switch SW12. Specifically, the switches SW1 to SW12 are constituted by semiconductor switches, relay contacts, or the like.

  Reference numeral 22 denotes a detector. The detector 22 generates a control signal C1 for controlling the switches SW1 and SW2, a control signal C2 for controlling the switches SW11 and SW12, and a control signal C3 for switching the output voltage of the DC-DC converter 21. The detector 22 is connected to an ID resistance recognition terminal 23 capable of reading a value of an identification resistance (hereinafter referred to as “ID resistance”) of the charger 17. The ID resistor is for specifying the type of the charger based on the resistance value, and the detector 22 can determine whether or not the connected charger 17 is correct from the read value of the ID resistor. The detector 22 has an electronic circuit configuration or a microcomputer configuration.

  When the regular charger 17 is not connected, the discharge mode is set, the switches SW1 and SW2 are turned off, the switches SW11 and SW12 are turned on by the control signals C1, C2, and C3, and the DC-DC converter 21 is turned on. Is set to the set discharge output voltage value. In the discharge mode, for example, a voltage of 3 V generated by the DC-DC converter 21 from a battery voltage of 2.5 V to 4.2 V, for example, is supplied to the discharge circuit 11 connected to the terminals 14 and 15.

  When the detector 22 detects that the regular charger 17 is connected based on the ID resistance, the charging mode is set, the switches SW1 and SW2 are turned on by the control signals C1, C2, and C3, and the switches SW11 and SW12 are turned on. Is turned off, and the output voltage of the DC-DC converter 21 is set to the set rated rated voltage value. In the charging mode, for example, the secondary battery 2 is charged with a charging voltage of, for example, 4.2 V generated by the DC-DC converter 21 from a charging voltage of 6 V, for example.

  FIG. 2 shows the connection configuration of the second embodiment of the present invention. In the second embodiment, a microcomputer indicated by reference numeral 24 is provided. The microcomputer 24 generates control signals C1, C2 and C3.

  The microcomputer 24 performs digital communication with the charger 17 via the communication terminal 25. Conventional two-wire communication can be used as a digital communication system. The microcomputer 24 determines whether or not the regular charger 17 is connected by performing digital communication.

  In the state where the regular charger 17 is not connected, the discharge mode is set. That is, the control signals C1, C2, and C3 are set to the discharge output voltage value in which the switches SW1 and SW2 are turned off, the switches SW11 and SW12 are turned on, and the output voltage of the DC-DC converter 21 is set.

  When the microcomputer 24 determines that the regular charger 17 is connected by digital communication, the charging mode is set, the switches SW1 and SW2 are turned on by the control signals C1, C2, and C3, and the switches SW11 and SW12 are turned off. The output voltage of the DC-DC converter 21 is set to the set rated charge voltage value.

FIG. 3 shows a reference connection configuration for explaining the present invention. In this configuration , a mechanical switch indicated by reference numeral 26 is provided. That is, when the charger 7 is connected to the electronic device main body 10, a switch 26 that is turned on (or turned off) by a mechanical configuration is provided. This switch 26 generates a control signal C0.

In a state where the charger 17 is not connected, for example, the switch 26 is turned off, the control signal C0 becomes, for example, “0” (meaning logical 0), and the discharge mode is set. That is, according to the control signal C0, the switches SW1 and SW2 are turned off, the switches SW11 and SW12 are turned on, and the output voltage of the DC-DC converter 21 is set to the discharge output voltage value.

When the charger 17 is connected, the switch 26 is turned on, the control signal becomes “1” (meaning logical 1), the charging mode is set, and the switches SW1 and SW2 are turned on by the control signal C0. The switches SW11 and SW12 are turned off, and the output voltage of the DC-DC converter 21 is set to the rated charging voltage value.

The present invention is not limited to the above-described embodiments, and various modifications and applications are possible without departing from the gist of the present invention. In the embodiments above mentioned For example, the use of the four switches, replacing the input-side switches SW1 and SW11 to the switch having two input terminals and one output terminal, the output-side switch SW2 and SW12 By replacing with a switch having one input terminal and two output terminals, a configuration using two switches can be realized. Further, when the output voltage in the charge mode and the output voltage in the discharge mode have the same voltage value, it is not necessary to supply a control signal for switching the output voltage to the DC-DC converter 21.

  Furthermore, you may make it connect directly with respect to a battery pack, without connecting a charger to an electronic device main body. Furthermore, as the DC-DC converter, one having a bidirectional input to output direction may be used.

It is a connection diagram of a 1st embodiment of this invention. It is a connection diagram of the second embodiment of the present invention. FIG. 3 is a connection diagram of a reference configuration for explaining the present invention; It is a connection diagram of an example of a conventional battery pack. It is a connection diagram of the other example of the conventional battery pack. FIG. 10 is a connection diagram of still another example of a conventional battery pack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery pack 2 Secondary battery 3 Protection circuit 9 Case 10 Electronic device main body 11 Discharge circuit 14 Discharge output terminal 15 Ground terminal 16 Charge input terminal 17 Charger 22 Detector 23 ID resistance recognition terminal 24 Microcomputer 25 Communication terminal 26 Mechanical switch

Claims (4)

In battery packs with built-in secondary batteries,
A charge input terminal and a discharge output terminal;
A bidirectional and switching DC-DC converter housed in a case together with a secondary battery and mounted on the same substrate as the protection circuit of the secondary battery;
First switch means for switching the input to the DC-DC converter between the secondary battery side and the charging input terminal side, and a first switch means for switching the output of the DC-DC converter between the discharge output terminal side and the secondary battery side . One of a charging mode for supplying a charging voltage to the secondary battery and a discharging mode for outputting a predetermined discharging voltage obtained by converting the voltage of the secondary battery. Switching means for switching the DC-DC converter;
Control signal generating means for generating a control signal for controlling the switching means,
The control signal generating means identifies a regular charger and generates a control signal for the switching means to switch the DC-DC converter to the charging mode only when a regular charger is connected. Battery pack featuring. In claim 1,
The battery pack is for detecting the identification resistance of the charger. In claim 1,
The battery pack in which the detection means performs digital communication with the charger. In claim 1,
A battery pack in which the switching means switches the value of the output voltage of the DC-DC converter between the charging mode and the discharging mode.

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