JP6292802B2 - Battery circuit, protection circuit - Google Patents

Description

  The present invention relates to a protection circuit that cuts off a current path, and more particularly to a battery circuit that needs to cut off a current path quickly in an emergency, such as a lithium ion secondary battery, and a protection circuit suitable for use in a battery circuit.

  Many secondary batteries that can be charged and used repeatedly are processed into battery packs and provided to users. In particular, in a lithium ion secondary battery having a high weight energy density, in order to ensure the safety of users and electronic devices, generally, a protection circuit for overcharge protection, overdischarge protection, etc. is built in the battery pack, It has a function of shutting off the output of the battery pack in a predetermined case.

  In this type of circuit, the overcharge protection or overdischarge protection operation of the battery pack is performed by turning on / off the output using an FET switch built in the battery pack. However, when the FET switch is short-circuited for some reason, when a lightning surge or the like is applied and an instantaneous large current flows, the output voltage drops abnormally due to the life of the battery cell, or conversely an excessively abnormal voltage Even when a battery pack is output, battery packs and electronic devices must be protected from accidents such as fire. Therefore, a protective element made of a fuse element having a function of cutting off a current path by a signal from the outside is used in order to safely cut off the output of the battery cell in any possible abnormal state.

  As a protection element for such a battery circuit for a lithium ion secondary battery or the like, a structure in which a heating element is provided inside the protection element and a fuse on a current path is blown by the heating element is generally used.

  As a related technique of the present invention, a battery circuit 50 is shown in FIG. The protection circuit 50 is, for example, a battery circuit used for a battery pack of a lithium ion secondary battery. The protection circuit 50 includes a battery stack 51 including a battery cell of the lithium ion secondary battery, and protection that cuts off charging when the battery stack 51 is abnormal. An element 52, a detection element 53 that detects the voltage of the battery stack 51, and a switch element 54 that controls the operation of the protection element 52 according to the detection result of the detection element 53 are provided.

  The protection element 52 is connected in series on the charge / discharge current path of the battery stack 51, is connected to the fuse 55 constituting a part of the charge / discharge current path, and the switch element 54, and is supplied with power from the battery stack 51. And a heating element 56 that generates heat and blows the fuse 55. In the protection element 52, the power supply to the heating element 56 is controlled by the switch element 54.

  The detection element 53 monitors the voltage of the battery stack 51 and outputs a control signal for controlling the switch element 54 when an overcharge voltage or an overdischarge voltage is reached.

  The switch element 54 is configured by, for example, an FET, and operates the protection element 52 when the voltage value of the battery stack 51 exceeds a predetermined overdischarge or overcharge state by a detection signal output from the detection element 53. Then, the charging / discharging current path of the battery stack 51 is controlled to be cut off.

  The battery circuit 50 having such a circuit configuration outputs a detection signal to the switch element 54 when the detection element 53 detects an abnormal voltage of the battery stack 51. Upon receiving the detection signal, the switch element 54 controls the current so that the heating element 56 of the protection element 52 is fed from the battery stack 51. Thereby, the battery circuit 50 can interrupt | block a charging / discharging electric current path | route, when the heat generating body 56 heat | fever-generates and the fuse 55 blows.

Japanese Patent Laid-Open No. 2005-243652 JP 2006-221919 A JP 2009-267293 A

  With recent downsizing and thinning of electronic devices, battery packs for lithium ion secondary batteries are also required to be small and thin. Further, with the widespread use of lithium ion secondary batteries, a protection circuit in a battery pack is required that has a relatively simple structure and is inexpensive while maintaining safety.

  However, in the battery circuit 50 shown in FIG. 8, the voltage of the battery stack 51 is constantly monitored by the detection element 53 that detects the voltage, and when the voltage becomes abnormal, a detection signal is output to the switch element 54 such as an FET. Control is performed so that the heating element 56 of the protection element 52 is energized by the switch element 54. Therefore, in the battery circuit 50, the detection element 53 for detecting the voltage and the switch element 54 for energizing the heating element 56 are essential, and it is necessary to secure a space for arranging the detection element 53 and the switch element 54.

  Therefore, it is difficult to reduce the size and thickness of the battery circuit 50 shown in FIG. 8, and the electronic device on which the battery element 50 such as a battery pack is mounted is hindered from being reduced in size and thickness. Further, the battery circuit 50 shown in FIG. 8 has a large number of parts, which is disadvantageous in terms of manufacturing man-hours and costs.

  Accordingly, an object of the present invention is to provide a battery circuit and a protection circuit that do not require the use of a switching element such as a detection element or FET in addition to the protection element.

In order to solve the above-described problem, a battery circuit according to the present invention includes a battery stack, a soluble conductor connected to a charge / discharge current path of the battery stack, and the melting conductor is blown off by generating heat. A protection circuit unit including a heating element that cuts off a charging / discharging current path, and is connected in series via the heating element and a power feeding circuit, and is connected in parallel to the battery stack, so that the voltage is equal to or higher than a predetermined voltage. It comes to have a current control element for energizing the heating element, the friendly溶導body and is provided on both sides of the connection end of the heating body with respect to the charge and discharge current path.
Further, the battery circuit according to the present invention cuts off the charging / discharging current path by fusing the soluble conductor by generating heat with the battery stack, the soluble conductor connected to the charging / discharging current path of the battery stack. A protection circuit unit including a heating element; and a current control element that is connected in series with the heating element and connected in parallel with the battery stack and energizes the heating element when the voltage exceeds a predetermined voltage. The current control element includes a plurality of Zener diodes having different energization directions connected in series.
Further, the battery circuit according to the present invention cuts off the charging / discharging current path by fusing the soluble conductor by generating heat with the battery stack, the soluble conductor connected to the charging / discharging current path of the battery stack. A protection circuit unit including a heating element, a current control element connected in series with the heating element, connected in parallel with the battery stack, and energizes the heating element when a voltage equal to or higher than a predetermined voltage; A detection element that detects an abnormal voltage of the battery stack; and a switch element that is connected to the heating element and receives a detection signal from the detection element to energize the heating element. The current control element includes the switch It is connected in parallel with the element.

The protection circuit according to the present invention includes a fusible conductor connected to a current path of an external circuit, a heating element that blows off the fusible conductor by heat generation and interrupts the external circuit, and a series of the heating element. And a current control element that is connected in parallel with the external circuit and energizes the heating element when the voltage is equal to or higher than a predetermined voltage, and the fusible conductor includes the heating element for the current path. It is provided on both sides of the connection end.
The protection circuit according to the present invention includes a fusible conductor connected to a current path of an external circuit, a heating element that blows off the fusible conductor by heat generation and interrupts the external circuit, and a series of the heating element. And a current control element that is connected in parallel with the external circuit and that causes the heating element to energize when the voltage exceeds a predetermined voltage, and the current control element includes a plurality of zeners having different energization directions. A diode is connected in series.
The protection circuit according to the present invention includes a fusible conductor connected to a current path of an external circuit, a heating element that blows off the fusible conductor by heat generation and interrupts the external circuit, and a series of the heating element. And a current control element that is connected in parallel with the external circuit and energizes the heating element when the voltage exceeds a predetermined voltage, a detection element that detects an abnormal voltage of the external circuit , and the heating element And a switch element that receives a detection signal from the detection element and energizes the heating element, and the current control element is connected in parallel with the switch element.

  According to the present invention, when the battery stack becomes a high voltage exceeding the rating, the current control element is controlled to flow a current to the heating element, so that the detection element for monitoring the voltage value of the battery stack, Since it is not necessary to provide a switching element such as an FET for controlling energization according to the result of the detection element, the battery pack can be easily downsized, and the number of parts and assembly man-hours are not increased.

FIG. 1 is a circuit diagram showing a battery circuit to which the present invention is applied. FIG. 2 is a circuit diagram showing another battery circuit to which the present invention is applied. FIG. 3 is a circuit diagram showing another battery circuit to which the present invention is applied. FIG. 4 is a cross-sectional view showing a configuration example of the antifuse. FIG. 5 is a circuit diagram showing a battery circuit using an antifuse as a current control element. FIG. 6 is a circuit diagram showing another battery circuit to which the present invention is applied. FIG. 7 is a circuit diagram showing a protection circuit to which the present invention is applied. FIG. 8 is a circuit diagram showing a battery circuit according to a conventional example.

  Hereinafter, a battery circuit and a protection circuit to which the present invention is applied will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention. Further, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Specific dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  As shown in FIG. 1, the battery circuit 1 to which the present invention is applied is used by being incorporated in a circuit in a battery pack 10 of a lithium ion secondary battery, for example. The battery pack 10 includes a battery stack 2, a protection circuit unit 3 that cuts off a charge / discharge current path when the battery stack 2 has an abnormal voltage, and a current control element 4 that controls a current flowing through the protection circuit unit 3.

  The battery stack 2 includes one or a plurality of battery cells 11 of lithium ion secondary batteries.

  The protection circuit unit 3 includes a fusible conductor 5 connected to the charging / discharging current path of the battery stack 2 and a heating element 6 that melts the fusible conductor 5 and cuts off the charging / discharging current path by generating heat.

  As the soluble conductor 5, any metal that is quickly melted by the heat generated by the heating element 6 can be used. For example, a low-melting-point metal such as Pb-free solder mainly containing Sn can be preferably used.

  The soluble conductor 5 may be formed by laminating a low melting point metal and a high melting point metal. As a laminated structure of a low-melting-point metal and a high-melting-point metal, for example, a structure in which a low-melting-point metal foil is coated by high-melting-point metal plating can be exemplified. As the low melting point metal, it is preferable to use solder such as Pb-free solder containing Sn as a main component, and as the high melting point metal, it is preferable to use Ag, Cu or an alloy containing these as main components. Even when the reflow temperature exceeds the melting temperature of the low melting point metal and the low melting point metal melts when the protective element constituting the protection circuit 1 is reflow mounted by containing the high melting point metal and the low melting point metal. The outflow of the low melting point metal to the outside can be suppressed, and the shape of the soluble conductor 5 can be maintained. In addition, even when fusing, the low melting point metal melts, and the high melting point metal is eroded (soldered), so that the fusing can be quickly performed at a temperature lower than the melting point of the high melting point metal.

  The fusible conductor 5 is connected in series on the charging / discharging path of the battery stack 2 by being soldered between a pair of electrodes formed separately from each other and connected to the charging / discharging path of the battery stack 2, Thereby, a part of charging / discharging path | route is comprised, and a charging / discharging path | route can be interrupted | blocked by fusing by the heat_generation | fever of the heat generating body 6. FIG.

  The heating element 6 is a conductive member that has a relatively high resistance value and generates heat when energized, and is made of, for example, W, Mo, Ru, or the like. A powdered body of these alloys, compositions, or compounds is mixed with a resin binder or the like to form a paste, and a pattern is formed on the insulating substrate on which the protective circuit 1 is formed using a screen printing technique. It is formed by firing or the like.

  In the battery circuit 1, the heating element 6 is connected in series with the current control element 4, and the heating element 6 and the current control element 4 are connected in parallel with the battery stack 2. As a result, the battery circuit 1 forms a power supply path 7 that supplies power to the heating element 6. In the power supply path 7, energization of the heating element 6 is regulated by the current control element 4 when the battery cell 11 of the battery stack 2 is at the rated voltage. When the battery cell 11 is overcharged for some reason and the battery stack 2 becomes a high voltage exceeding the rating, the battery circuit 1 is energized in the power supply path 7 by the current control element 4. The heating element 6 starts to generate heat and melts the soluble conductor 5.

  The current control element 4 regulates energization to the heating element 6 side when the voltage of the battery stack 2 is within the rated range. Then, when the voltage of the battery stack 2 becomes equal to or higher than a predetermined value, the current control element 4 energizes the heating element 6 with the current of the battery stack 2 to generate heat.

  As such a current control element 4, for example, a Zener diode 12 can be used. The battery circuit 1 sets the breakdown voltage of the Zener diode 12 to a voltage value (for example, 4.5 v) detected when the battery cell 11 is overcharged, thereby reducing the voltage under normal conditions (for example, 4.2 v). ), The energization of the heating element 6 is restricted and can be used as a normal power supply circuit. When the battery stack 2 becomes a high voltage due to overcharging of the battery cell 11, the battery circuit 1 applies a voltage exceeding the breakdown voltage of the Zener diode 12, thereby causing a current to flow through the power supply path 7. The heating element 6 can generate heat.

  The battery circuit 1 is divided by melting the fusible conductor 1 due to heat generated by the heating element 6 and aggregating the molten conductor on a pair of electrodes separated from each other, thereby blocking the charge / discharge path of the battery stack 2. Can do. Here, the battery circuit 1 interrupts the charge / discharge path irreversibly because the battery circuit 1 interrupts the charge / discharge path by fusing the soluble conductor 5 of the protection circuit unit 3.

  In this way, the battery circuit 1 is controlled so that a current is supplied to the power supply path 7 of the heating element 6 by the current control element 4 when the battery stack 2 becomes a high voltage exceeding the rating due to overcharging of the battery cell 11. Therefore, there is no need to provide a detection element for monitoring the voltage value of the battery stack 2 or a switch element such as an FET for controlling the current of the power supply path 7 according to the result of the detection element. In addition to being easy, the number of parts and the number of assembly steps are not increased.

  In addition, according to the battery circuit 1, since the charge / discharge path is irreversibly blocked by fusing the fusible conductor 5, it is possible to cope with switch element failures, hacking, and vulnerability to cracking, which is stable and reliable. The charge / discharge path can be interrupted.

  Note that, after the fusible conductor 5 is melted, the battery circuit 1 falls below the breakdown voltage of the Zener diode 12 due to the voltage drop due to the discharge of the battery cell 11, thereby stopping the power supply to the heating element 6 and stopping the heat generation. .

  In addition, as shown in FIG. 2, the battery circuit 1 may have two Zener diodes 12 arranged on the power supply path 7 so that the energization directions when a breakdown voltage is applied are opposite to each other. By providing a plurality of zener diodes 12 so that the energization directions are different, the battery circuit 1 is connected in reverse when one zener diode 12 is used, and the power supply path 7 is energized during normal use, and the heating element It is possible to prevent the fusible conductor 5 from fusing due to the heat generated at 6.

  Moreover, the battery circuit 1 may connect the current control element 4 in parallel for each of the plurality of battery cells 11 constituting the battery stack 2 as shown in FIG. For example, the battery stack 2 is configured by connecting four battery cells 11a to 11b in series, and a pair of zener diodes 12a to 12d having opposite energization directions are connected in parallel to each of the battery cells 11a to 11d. Is done. The Zener diodes 12a to 12d are set so that the breakdown voltage value also increases according to the voltage value at the connection location with the battery cells 11a to 11d.

  As described above, the Zener diode 12 is connected to each of the plurality of battery cells 11, so that the battery circuit 1 has a normal voltage value of the battery stack 2 but any one of the battery cells 11 is overcharged due to overcharge. Even in the state, the charging / discharging path can be blocked by energizing the power supply path 7 and fusing the soluble conductor 5 by the heating element 6.

The battery circuit 1 may use an antifuse element as the current control element 4 in addition to the Zener diode 12. The antifuse element 13 is an element that is short-circuited when a voltage of a predetermined level or higher is reached, and a current flows. For example, as shown in FIG. 4, wiring patterns 22 a and 22 b are provided on an insulating substrate 20 with a gap 21 therebetween. And the insulator layer 23 is formed so as to be in contact with both the wiring patterns 22 a and 22 b and straddle the gap 21. This insulator layer 23 can be formed of SiO ₂ or the like.

  The wiring patterns 22a and 22b are insulated by the air gap 21, but when a voltage higher than a predetermined voltage is applied, the insulation by the insulator layer 23 is broken, and the current is insulated from one wiring pattern 22a. It flows through the body layer 23 and flows to the other wiring pattern 22b.

  Also with such an antifuse element 13, when either the battery stack 2 or the battery cell 11 is in a high voltage state, the power supply path 7 is energized by short-circuiting between the wiring patterns 22a and 22b, thereby generating heat. The soluble conductor 5 can be melted by the heat generated by the body 6.

  The antifuse element 13 is not limited to the configuration shown in FIG. 4 and includes any configuration that exhibits an equivalent function.

  In addition, when the battery circuit 1 uses the antifuse 13 as the current control element 4, it is preferable to provide the soluble conductor 5 on both sides of the connection end with the heating element 6 as shown in FIG. 5. In this case, in the battery circuit 1, when the heating element 6 generates heat, the pair of soluble conductors 5 provided on both sides of the connection end with the heating element 6 are fused together. Thereby, in the battery circuit 1, the charging / discharging path of the battery cell 11 is blocked, the power feeding path 7 to the heating element 6 is also blocked, and the heating of the heating element 6 is stopped. Note that the battery circuit 1 may be provided with the fusible conductor 5 on both sides of the connection end with the heating element 6 even when the Zener diode 12 is used as the current control element 4.

  Further, as shown in FIG. 6, the battery circuit 1 is connected to a detection element 8 that detects an abnormal voltage of the battery stack 2 and a heating element, and receives a detection signal from the detection element 8 to supply power to the heating element 6. 7 may be provided, and the current control element 4 may be connected in parallel with the switch element 9.

  The detection element 8 is connected to the battery stack 2 or each battery cell 11 constituting the battery stack 2 and constantly monitors whether or not it is in a high voltage state. 9 outputs a control signal.

  The switch element 9 controls the operation of the protection circuit unit 3 in accordance with the detection result of the detection element 8, and is constituted by, for example, an FET, restricts energization to the power supply path 7, and controls the control signal from the detection element 8. In response, the power supply path 7 is energized.

  In the battery circuit 1, the switch element 9 and the current control element 4 are connected in parallel on the power feeding path 7. The battery circuit 1 includes two methods: a method using the detection element 8 and the switch element 9 or a method using the current control element 4 such as the Zener diode 12 or the antifuse element 13 described above to interrupt the charge / discharge path. .

  Thereby, even when any one of the detection element 8 and the switch element 9 or the current control element 4 fails, the battery circuit 1 can prevent the battery stack 2 and the battery cell 11 from being in a high voltage state. The power feeding path 7 can be energized to block the charge / discharge path.

  In the battery circuit 1, the protection circuit unit 3 and the current control element 4 are provided separately. However, as shown in FIG. 7, the present invention provides a current control element 4, a soluble conductor 5, and a heating element. 6 may be formed on one chip to form the protection circuit 30.

  In the protection circuit 30, both ends of the fusible conductor 5 are connected to an external circuit 31 such as a battery circuit, and constitute a part of the current path of the external circuit 31. The protection circuit 30 is connected in parallel with a device in which the current control element 4 and the heating element 6 need to detect a high voltage state such as a battery stack in the external circuit 31.

  Even when such a protection circuit 30 is incorporated in the external circuit 31, the current control element 4 regulates the energization of the power supply path 7 in a normal state, and the power supply path 7 is energized when the external circuit 31 is in a high voltage state. Thus, the fusible conductor 5 can be blown by the heat generating element 6 by heat generation, and the current path of the external circuit 31 can be cut off.

  The protection circuit 30 can be used not only for a battery circuit but also for various external circuits that need to interrupt a current path by detecting a high voltage state.

DESCRIPTION OF SYMBOLS 1 Battery circuit, 2 Battery stack, 3 Protection circuit part, 4 Current control element, 5 Soluble conductor, 6 Heating element, 7 Feeding path, 8 Detection element, 9 Switch element, 10 Battery pack, 11 Battery cell, 12 Zener diode , 13 Antifuse element, 20 Insulating substrate, 21 Air gap, 22 Wiring pattern, 23 Insulator layer, 30 Protection circuit, 31 External circuit

Claims (14)

A battery stack;
A protection circuit unit comprising a soluble conductor connected to the charging / discharging current path of the battery stack, and a heating element that cuts off the charging / discharging current path by fusing the soluble conductor by generating heat;
A current control element that is connected in series via the heating element and the power supply circuit, connected in parallel to the battery stack, and energizes the heating element when the voltage is equal to or higher than a predetermined voltage,
The fusible conductor is a battery circuit provided on both sides of a connection end of the heating element with respect to the charge / discharge current path.   The battery circuit according to claim 1, wherein the current control element is a Zener diode. The battery circuit according to claim 2, wherein a plurality of the Zener diodes having different energization directions are connected in series. The battery circuit according to claim 1, wherein the current control element is connected in parallel for each battery cell of the battery stack. A detecting element for detecting an abnormal voltage of the battery stack;
A switch element connected to the heating element and receiving a detection signal from the detection element to energize the heating element;
The battery circuit according to claim 1, wherein the current control element is connected in parallel with the switch element.   The battery circuit according to claim 1, wherein the current control element is an antifuse. A battery stack;
A protection circuit unit comprising a soluble conductor connected to the charging / discharging current path of the battery stack, and a heating element that cuts off the charging / discharging current path by fusing the soluble conductor by generating heat;
A current control element connected in series with the heating element, connected in parallel with the battery stack, and energized to the heating element when the voltage is equal to or higher than a predetermined voltage;
The current control element is a battery circuit in which a plurality of Zener diodes having different energization directions are connected in series.   The battery circuit according to claim 7, wherein the current control element is connected in parallel for each battery cell of the battery stack. A battery stack;
A protection circuit unit comprising a soluble conductor connected to the charging / discharging current path of the battery stack, and a heating element that cuts off the charging / discharging current path by fusing the soluble conductor by generating heat;
A current control element connected in series with the heating element, connected in parallel with the battery stack, and energizes the heating element when the voltage is equal to or higher than a predetermined voltage;
A detecting element for detecting an abnormal voltage of the battery stack;
A switch element connected to the heating element, receiving a detection signal from the detection element and energizing the heating element;
The current control element is a battery circuit connected in parallel with the switch element.   The battery circuit according to claim 9, wherein the current control element is a Zener diode or an antifuse. A fusible conductor connected to the current path of the external circuit;
A heating element that cuts off the external circuit by fusing the soluble conductor by generating heat; and
A current control element connected in series with the heating element, connected in parallel with the external circuit, and energizing the heating element when the voltage is equal to or higher than a predetermined voltage;
The fusible conductor is a protection circuit provided on both sides of a connection end of the heating element with respect to the current path. A fusible conductor connected to the current path of the external circuit;
A heating element that cuts off the external circuit by fusing the soluble conductor by generating heat; and
A current control element connected in series with the heating element, connected in parallel with the external circuit, and energizing the heating element when the voltage is equal to or higher than a predetermined voltage;
The current control element is a protection circuit in which a plurality of Zener diodes having different energization directions are connected in series. A fusible conductor connected to the current path of the external circuit;
A heating element that cuts off the external circuit by fusing the soluble conductor by generating heat; and
A current control element connected in series with the heating element, connected in parallel with the external circuit, and energizes the heating element when a voltage equal to or higher than a predetermined voltage,
A detecting element for detecting an abnormal voltage of the external circuit ;
A switch element connected to the heating element, receiving a detection signal from the detection element and energizing the heating element;
The current control element is a protection circuit connected in parallel with the switch element.   The protection circuit according to claim 11, wherein the current control element is a Zener diode or an antifuse.

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