JP6645401B2 - Protective equipment - Google Patents

Description

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

Conventionally, in a battery such as a lithium ion secondary battery, when a pressure in a battery case becomes larger than a predetermined value, a current cutoff mechanism for cutting a battery current flowing through the battery may be installed in the battery. (See, for example, Patent Document 1).
Further, a voltage detecting unit and a fuse body are provided in the battery as an overcharge prevention mechanism. There is also a technique for fusing the body (see Patent Document 2).

JP 2014-86140 A JP 2015-130347 A

However, the current cutoff mechanism disclosed in Patent Literature 1 or the like operates due to a pressure increase in the battery due to overcharging or the like, and cannot detect the overvoltage itself and cut off the battery current.
On the other hand, the overcharge prevention mechanism disclosed in Patent Document 2 has a voltage detecting unit, a fuse body, a switch member, and the like provided in the battery. Such sparks may cause ignition of the organic solvent, which is a component of the electrolytic solution.

  The present invention has been made in view of such a problem, and it is an object of the present invention to provide a protection device that can quickly and safely shut off a battery current when a battery exceeds a predetermined battery voltage such as overcharge. .

One embodiment of the present invention is a protection device which is provided outside a battery and protects the battery, and includes a current path through which a battery current for charging and discharging the battery flows, and a current path in the current path or in series with the current path. A connected temperature fuse, an energized heating element that generates heat by energization and heats the temperature fuse, and energizes the energized heating element to generate heat when the battery voltage of the battery exceeds a predetermined operating voltage. An energization control unit that blows the thermal fuse, wherein the energization control unit boosts the battery voltage of the battery and outputs a constant output voltage. Switching element to be turned on and off, and comparing the operating voltage and the battery voltage generated from the output voltage, when the battery voltage exceeds the operating voltage, turn on the switching element, Comparator that performs energization of the serial energization heater, a protective device that have a.

  Since this protection device is installed outside the battery, there is no danger of igniting the electrolyte of the battery during operation and the protection device is safe. When a battery voltage exceeds the operating voltage, a current is supplied to the current-carrying heating element to generate heat under the control of the current-carrying control unit, and the temperature fuse is blown. Thus, with this protection device, when the battery voltage exceeds the operating voltage, the thermal fuse is immediately blown, the current path is cut off, further charging and discharging of the battery is stopped, and the battery is disconnected from external equipment. Can be separated and protected.

  Here, the energized heating element may be any element that generates heat when energized, and examples thereof include a resistance heating element and a heating coil. Further, the energization control unit may be configured with only an analog circuit such as a comparator, or may be configured with a digital circuit including a microcomputer. The operating voltage may be appropriately set according to the type of the battery, the usage environment, and the like. However, the operating voltage may be set to an appropriate value within the range of the overcharge voltage that exceeds the range of the battery voltage normally used. Is preferred.

  Further, in the above-described protection device, it is preferable that the current supply control unit is a protection device that supplies current to the current-carrying heating element even after the thermal fuse is blown until the battery voltage falls below the operating voltage.

  In this protection device, even after the thermal fuse is blown, the energizing heating element is energized until the battery voltage falls below the operating voltage. For this reason, even after the thermal fuse is blown, power is consumed through the current-carrying heating element and the battery voltage can be reduced until the operating voltage falls below the operating voltage, so that the battery can be protected more safely.

FIG. 3 is a circuit diagram of a battery and a protection device connected to the battery according to the embodiment. It is a circuit diagram of a protection device concerning an embodiment. It is a flowchart of battery protection performed by the protection device of the embodiment.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of a lithium ion secondary battery (hereinafter, also simply referred to as “battery”) BT and a protection device 1 according to an embodiment connected thereto, and FIG. 2 is a circuit diagram of the protection device 1. FIG. 3 shows a flowchart of protection of the battery BT using the protection device 1 according to the present embodiment.

  As shown in FIGS. 1 and 2, the protection device 1 connects the battery-side positive terminal 1PB to the positive electrode BTP of the battery BT, and connects the battery-side negative terminal 1NB to the negative electrode BTN of the battery BT. Instead of the negative electrode BTN, the positive terminal 1PT and the negative terminal 1NT are connected to an external device (not shown) for use.

  The protection device 1 includes, among the current paths 1A and 1B through which the battery current Ib flows, a temperature fuse 2 provided in the current path 1A and having a predetermined operating temperature; And an energization control unit 4 for controlling energization of the heating element 3. In this protection device 1, the energization control unit 4 is separate from the thermal fuse 2 and the heating element 3, but the thermal fuse 2 and the heating element 3 are thermally coupled. , And the thermal fuse 2 is arranged to be heated. When the temperature of the thermal fuse 2 exceeds the operating temperature, the thermal fuse 2 itself blows and the current path 1A is cut off.

  The energization control unit 4 determines that the positive electrode wire 4P connected to the positive electrode terminal 4PT is located on the battery BT side (the positive electrode BTP side of the battery BT, the battery-side positive terminal 1PB side) of the current fuse 1A in FIG. (Left side), and a negative electrode wiring 4N connected to the negative electrode terminal 4NT is connected to the current path 1B. As a result, the battery voltage Vb of the battery BT is applied between the positive terminal 4PT and the negative terminal 4NT of the conduction controller 4.

  A step-up constant voltage circuit 41 is connected to the positive terminal 4PT of the energization control unit 4, and boosts and outputs the battery voltage Vb to a higher and constant output voltage Vs (Vs> Vb). The output of the step-up constant voltage circuit 41 is used as a power supply for a comparator 44, and is further divided into a constant operating voltage Vf by resistors 42 and 43 connected in series, and input to an inverting input terminal 44n of the comparator 44. Have been. On the other hand, the battery voltage Vb is input to the non-inverting input terminal 44p of the comparator 44. For this reason, the output voltage Vo appearing at the output terminal 44o of the comparator 44 changes according to the magnitude of the battery voltage Vb. Specifically, when the battery voltage Vb is lower than the operating voltage Vf (Vb <Vf), the output voltage Vo is set to L (low). On the other hand, when the battery voltage Vb is higher than the operating voltage Vf (Vb> Vf), the output voltage Vo is set to H (high).

  In the energization control unit 4 (protection device 1), the operating voltage Vf can be set to an appropriate value. In the present embodiment, the operating voltage Vf corresponds to, for example, the battery voltage Vb when the battery BT exceeds the fully charged battery voltage Vb = 4.25 V and becomes unacceptably overcharged. , Vf = 4.5V.

  The transistor 46, which is a switching element connected to the output terminal 44o of the comparator 44, is turned off when the output voltage Vo is L (low), and does not energize the heating element 3. On the other hand, when the output voltage Vo is H (high), the transistor 46 is turned on, and electricity is supplied to the heating element 3 via the resistor 47. Note that the resistor 47 is a current limiting resistor.

  Therefore, in the protection device 1, when the battery voltage Vb is lower than the operating voltage Vf (Vf = 4.5V in the present embodiment) (Vb <Vf), the power supply to the heating element 3 is not performed (step S1). No in S1). However, when the battery voltage Vb exceeds the operating voltage Vf, for example, when the battery BT is overcharged (Vb> Vf, Yes in step S1), the heating element 3 is energized (step S2). Then, the temperature of the thermal fuse 2 rises due to the heat generated by the heating element 3, and when the temperature exceeds the operating temperature, the thermal fuse 2 is blown and the current path 1A is cut off (step S3).

Thus, in the protection device 1, when the battery voltage Vb exceeds the operating voltage Vf (Vb> Vf), the temperature fuse 2 is quickly blown to cut off the current path 1A, and the battery BT is no longer charged. Discharging can be stopped, and the battery BT can be separated and protected from external devices. In addition, since the protection device 1 is installed outside the battery BT, there is no danger of the electrolyte of the battery BT being ignited by the operation of the protection device 1 and the device is safe.
Moreover, in the protection device 1, not only the operating temperature of the thermal fuse 2 but also the output voltage of the step-up constant voltage circuit 41 in consideration of the amount of heat and the ultimate temperature of the heating element 3 By appropriately selecting the resistance values of Vs, the heating element 3 and the resistor 47, when the battery voltage Vb exceeds the operating voltage Vf and the transistor 46 is turned on, the thermal fuse 2 is reliably blown and the current path 1A is cut off. Can be done.

  Further, in the protection device 1, even if the thermal fuse 2 operates and the current path 1A is cut off, the power supply unit 4 is continuously supplied with power from the battery BT, so that the battery voltage Vb gradually decreases (step S4). . That is, until the battery voltage Vb of the battery BT falls below the operating voltage Vf (Vb <Vf, Yes in step S5), power is supplied from the battery BT to the heating element 3 and is continuously consumed by the heating element 3, and thereafter, the heating element 3 3 is stopped (step S6). Therefore, in the protection device 1, the battery BT can be held in a state where the battery voltage Vb is lower than the operating voltage Vf (Vb <Vf), and the battery BT can be protected more safely.

  In the present embodiment, as described above, the operating voltage Vf is set to Vf = 4.5 V in the overcharge voltage range. Thus, in the protection device 1 according to the present embodiment, when the battery BT is overcharged so as to exceed Vf = 4.5 V, further charging / discharging is stopped and the battery BT can be reliably protected. it can.

In the above, the present invention has been described with reference to the embodiments. However, it is needless to say that the present invention is not limited to the above-described embodiments, and can be appropriately modified and applied without departing from the gist thereof.
In the protection device 1 of the above-described embodiment, the positive electrode wiring 4P of the conduction control unit 4 is connected to the battery BT side of the current path 1A with respect to the temperature fuse 2. However, as shown by a broken line in FIG. 2, the positive wiring 4Pa of the conduction control unit 4 may be connected to the positive terminal 1PT side (the right side in FIG. 2) of the current path 1A with respect to the temperature fuse 2.
In this case, the power supply of the power supply control unit 4 itself is also lost due to the operation (fuse) of the thermal fuse 2, and the operation of the power supply control unit 4 is stopped together with the operation (fuse) of the thermal fuse 2. Can be separated from the outside and protected while the thermal fuse 2 is operating.
In the protection device 1 of the above-described embodiment, the thermal fuse 2 is provided in the current path 1A. However, the thermal fuse may be provided in series with the current path 1A.

BT Lithium ion secondary battery (battery)
Vb Battery voltage Ib Battery current 1 Protector 1A, 1B Current path 2 Thermal fuse 3 Heating element (electric heating element)
4 Energization control unit 41 Step-up constant voltage circuit Vs Output voltage 42, 43, 45, 47 (of step-up constant voltage circuit) Resistance 44 Comparator 46 Transistor Vf Operating voltage

Claims (1)

A protection device installed outside the battery to protect the battery,
A current path through which a battery current for charging and discharging the battery flows;
A thermal fuse connected in series with or in the current path;
An energizing heating element that generates heat when energized to heat the thermal fuse;
When the battery voltage of the battery exceeds a predetermined operating voltage, an energization control unit that energizes the energizing heating element to generate heat and blow the thermal fuse ,
The energization control unit includes:
A boosting constant voltage circuit that boosts the battery voltage of the battery and outputs a constant output voltage,
A switching element for turning on and off energization to the energization heating element, and
Comparing the operating voltage generated from the output voltage with the battery voltage, and when the battery voltage exceeds the operating voltage, turning on the switching element and conducting a current to the energized heating element. , that having a protective device.

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