TW202037028A - Protective circuit - Google Patents

Abstract

Provided is a protection circuit that can realize a downsizing of a device with a simple configuration while reliably suppressing noise, and also reduce the effect of noise on a human body. A protection circuit (2A) comprises: a protection element (10) having a fusible metal body (11) connected on an energization path in a battery pack (1), and a heating element (12) that is connected to the fusible metal body (11) and enables disconnection by heating the fusible metal body (11); a protection device (20) for detecting an abnormality of a battery (3) connected to the energization path; a switching element (30) that operates so as to energize the heating element (12) of the protection element (10) on the basis of the detection result of the protection device (20); and a frequency selection element (40) that is connected in parallel with the switching element (30) and passes noise in a predetermined frequency band.

Description

protect the circuit

The present invention relates to a protection circuit, for example, to a protection circuit provided in a charging and discharging circuit of a secondary battery.

Previously, protection circuits were installed in mobile devices such as mobile phones, portable computers, or rechargeable electric machines, and various devices equipped with secondary batteries. As a protection circuit for a battery pack equipped with a lithium ion secondary battery, for example, a configuration in which a fuse with a heater including a fuse element and a heater is connected to the charge and discharge circuit of the battery pack is known.

In the above-mentioned protection circuit, in the event of an abnormality such as overcharging, the heater generates heat by the detection element rushing current to the heater, and the fuse element is melted and disconnected by the heat. For example, there is the following structure: in a protection circuit provided with a voltage detection IC (integrated circuit), when the voltage detection IC detects an overvoltage, the field effect electricity on the energization path of the heater When the FET is turned on, the heater generates heat, and the fuse element is melted off by the heat of the heater (Patent Document 1).

Here, the semiconductor constituting the IC or FET has the risk of malfunctioning due to noise generated inside the machine or noise invaded from the outside. For example, in the above-mentioned protection circuit using a lithium-ion battery, when the voltage detection IC used to monitor the overvoltage malfunctions, the fuse with the heater may be accidentally disconnected and the machine may not be used. Therefore, it is necessary to take countermeasures to suppress noise that may have an adverse effect on the IC.

As a mechanism for suppressing noise, for example, a protection circuit for lithium-ion battery packs is proposed, which is a large-capacity capacitor with a value sufficiently lower than the high-frequency internal impedance of a lithium-ion battery, or a high-frequency internal An assembled battery with a lower impedance is constructed by connecting the lithium ion battery in parallel so that the voltage becomes higher than the voltage of the lithium ion battery (Patent Document 2). [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2008-263776 [Patent Document 2] Japanese Patent Laid-Open No. 09-45375

[The problem to be solved by the invention]

Generally speaking, as methods for suppressing noise, the following (1) to (4) can be cited. (1) A method of converting electromagnetic energy into heat energy represented by noise absorbing sheets dispersed with magnetic materials, etc. (2) A method of reflecting unwanted radiation represented by metal shielding (3) A method to discharge the noise on the transmission line to the substrate GND represented by the filter (4) How to release noise to the outside of the machine

However, in the above-mentioned methods (2) and (3), there are cases where the energy of the noise itself is maintained almost without attenuation, so the noise generated in the distant part may be bypassed through the substrate GND, etc., as a result There are situations where the entire machine cannot suppress noise. Therefore, in Patent Document 2, the configuration in which the capacitor is installed has a problem that the noise cannot be reliably suppressed by discharging the noise to GND, and in the configuration in which the assembled battery is installed, there is a problem in that the equipment is enlarged.

In addition, in the above method (4), the noise inside the machine is reduced by releasing the noise to the outside of the machine. However, the presence of the noise not only has a bad influence on the IC, but also has a bad influence on the human body. Therefore, it is desirable to suppress noise inside the machine as much as possible.

In addition, in the method of (1) above, that is, a method of using a noise absorbing sheet that converts noise into heat energy, the noise absorbing sheet is based on the magnetic permeability or particle size (especially the particle size) of the magnetic body The frequency characteristics change, so in order to absorb low-frequency noise of about hundreds of kHz, the noise absorbing sheet must contain a magnetic body with a larger particle size. Therefore, there is a problem that the thickness of the noise absorbing sheet becomes larger and the machine becomes larger.

The object of the present invention is to provide a protection circuit that can reliably suppress noise and realize the miniaturization of the machine with a simple structure, thereby reducing the influence of noise on the human body. [Technical means to solve the problem]

In order to achieve the above object, the present invention provides the following means. [1] A protection circuit with: A protection element, which has a fusible metal body connected to the energization path, and a heating body connected to the above-mentioned fusible metal body and capable of melting and disconnecting the above-mentioned fusible metal body by heating; Protection device, which detects abnormalities of the machine connected to the above-mentioned power path; A switching element that operates by energizing the heating element of the protection element based on the detection result of the protection device; and The frequency selection element is connected in parallel with the above-mentioned switching element and passes noise of a specific frequency band. [2] The protection circuit as in [1] above, wherein the above-mentioned specific frequency band is 1 kHz to 1 GHz. [3] The protection circuit of [1] or [2] above, wherein the magnetic energy of the noise in the specific frequency band is converted into heat energy by the heating element. [4] The protection circuit of [1] above, wherein the frequency selection element is a high-pass filter. [5] The protection circuit of [1] above, wherein the machine is connected to the battery of the power path, The protection device detects the voltage of the battery, and determines whether the battery is abnormal based on the voltage. [6] The protection circuit as in [1] above, which has: A protection element, which has a fusible metal body connected to the energization path, and a heating body connected to the above-mentioned fusible metal body and capable of melting and disconnecting the above-mentioned fusible metal body by heating; A protection device that detects abnormalities in the machine connected to the above-mentioned power path; and A switching element that operates by energizing the heating element of the protection element based on the detection result of the protection device; and The above-mentioned switching element includes a semiconductor element having frequency selectivity for selectively outputting noise of a specific frequency band. [7] The protection circuit as in [6] above, wherein the above-mentioned specific frequency band is 1 kHz to 1 GHz. [8] The protection circuit of [6] or [7] above, wherein the magnetic energy of the noise in the specific frequency band is converted into heat energy by the heating element. [9] The protection circuit according to [6] above, wherein the semiconductor element is a field effect transistor. [10] The protection circuit of [6] above, wherein the machine is connected to the battery of the power path, The protection device detects the voltage of the battery, and determines whether the battery is abnormal based on the voltage. [Effects of Invention]

According to the present invention, noise can be reliably suppressed, and the miniaturization of the machine can be realized with a simple structure, thereby reducing the influence of noise on the human body.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a circuit diagram schematically showing the configuration of the protection circuit of the first embodiment of the present invention. In this embodiment, a protection circuit of a battery pack installed in a mobile device such as a mobile phone is taken as an example for description.

As shown in FIG. 1, the protection circuit 2A includes: a protection element 10 having a fusible metal body 11 connected to the energization path in the battery pack 1, and a fusible metal body 11 connected to the fusible metal body 11 and can be heated The heating element 12 that the molten metal body 11 melts and disconnects; the protection device 20, which detects abnormality of the battery 3 (machine) connected to the above-mentioned energization path; the switching element 30, which is based on the detection result of the protection device 20, to the protection element 10 The heating element 12 operates in a energized manner; and a frequency selection element 40, which is connected in parallel with the switching element 30, and allows noise of a specific frequency band to pass.

The protection element 10 is connected to an external circuit by the first connection portion A, the second connection portion B, and the third connection portion C, thereby constituting a part of the protection circuit 2A. In the protection element 10, the fusible metal body 11 is connected to the energization path (charge and discharge path) of the battery 3 via the first connection portion A and the second connection portion B, and the heating element 12 is connected to the battery 3 via the switching element 30 In the power supply path, the action of the protection element 10 is controlled by the protection device 20. The protection element 10 includes, for example, a fuse with a heater.

The fusible metal body 11 includes, for example, a first fuse element 11A and a second fuse element 11B connected in series on a substrate (not shown). The heating element 12 is connected between the first fuse element 11A and the second fuse element 11B.

The first fuse element 11A and the second fuse element 11B are integrally formed or are composed of different members. The first fuse element 11A and the second fuse element 11B have, for example, a sheet shape or a rod shape.

The fusible metal body 11 is preferably a laminated body including a low melting point metal layer and a high melting point metal layer including a high melting point metal having a higher melting point than the low melting point metal. In this case, the first fuse element 11A and the second fuse element 11B are also a laminated body including a low melting point metal layer and a high melting point metal layer including a high melting point metal having a higher melting point than the low melting point metal. Furthermore, the fusible metal body 11 more preferably has a coating structure including a low melting point metal layer as an inner layer and a high melting point metal layer as an outer layer covering the low melting point metal layer as the inner layer.

Various low-melting-point metals previously used as fuse materials can be used as the material constituting the aforementioned low-melting-point metal layer. Examples of the low melting point metal include SnSb alloy, BiSnPb alloy, BiPbSn alloy, BiPb alloy, BiSn alloy, SnPb alloy, SnAg alloy, SnAgCu alloy, PbIn alloy, ZnAl alloy, InSn alloy, PbAgSn alloy, and the like. The low melting point metal layer does not necessarily need to have a higher melting point than the reflow temperature, and it can also be melted at about 200°C.

The material constituting the high melting point metal layer can be, for example, Ag, Cu, or a metal containing Ag or Cu as a main component. The high melting point metal layer has a higher melting point that does not melt even when the fusible metal body 11 is mounted on an external circuit board using a reflow furnace.

The heating body 12 includes a heater. The heater is formed, for example, by applying a resistive paste including a conductive material such as ruthenium oxide or carbon black, an inorganic binder such as water glass, or an organic binder such as a thermosetting resin, and firing as necessary. In addition, as a heater, thin films such as ruthenium oxide or carbon black may be formed through steps of printing, plating, vapor deposition, and sputtering, or may be formed by attaching or lamination of these films.

The protection device 20 detects the voltage of the battery 3 connected to the energization path of the protection element 10, specifically the voltages of the battery cells 3A, 3B, 3C, and 3D, and determines whether the battery 3 (battery cells 3A to 3D) is generated based on the voltage Abnormalities such as overcharging. When an abnormality occurs in the battery cells 3A to 3D, the protection device 20 activates the protection element 10 to block the energization path. The protection device 20 is connected to the switching element 30 that controls the energization operation to the protection element 10 based on the detection result of the protection device 20, and is further connected to the protection element 10 via the third connection portion C. Furthermore, the protection device 20 outputs a control signal to the switching element 30 in accordance with the abnormality of the battery cells 3A to 3D.

The switching element 30 includes, for example, a field effect transistor (hereinafter also referred to as FET). According to the control signal output from the protection device 20, the switching element 30 energizes the protection element 10 to block the energization path of the battery 3 when the voltage of the battery cells 3A to 3D is above a specific value indicating the overdischarge or overcharge state The way of action.

The frequency selection element 40 is, for example, a high-pass filter, which passes noise in the above-mentioned specific frequency region. The specific frequency band is, for example, 1 kHz to 1 GHz, preferably 1 kHz to 1 MHz. The frequency selection element 40 is connected in parallel with the switching element 30 as described above, and noise of a specific frequency band propagates through the energization path and reaches the frequency selection element 40.

In the protection circuit 2A configured as described above, when the battery 3 is charged, power is supplied from the charging device 4 to the battery 3 via an external circuit. In addition, when the battery 3 is discharged, power is supplied from the battery 3 to the external circuit. The battery 3 is a primary battery or a secondary battery, and examples thereof include a lithium ion secondary battery. Connect a load such as a motor or converter not shown in the figure to the external circuit.

The protection device 20 detects the voltage of each of the battery cells 3A to 3D, and when it is determined that any of the battery cells 3A to 3D has an abnormality such as overcharge, it outputs a control signal to the switching element 30. Thereby, the switching element 30 operates in a manner of energizing the heating element 12, and as a result, by the heating of the heating element 12, at least one of the first fuse element 11A and the second fuse element 11B constituting the fusible metal body 11 Those melted and disconnected. Thereby, the energization path of the battery cells 3A to 3D is blocked.

In addition, if noise of a specific frequency band propagates through the energization path and reaches the frequency selection element 40, it passes through the frequency selection element 40 and reaches the heating element 12 of the protection element 10. In addition, in the heating element 12, the magnetic energy of the noise of a specific frequency band is converted into heat energy by the heating element 12. At this time, the heat energy generated by the heating element 12 due to the noise is sufficiently lower than the heat energy generated by the power supplied from the battery 3 during the abnormal detection of the protection device 20, so the fusible metal body 11 of the protection device 10 will not be removed. Melt disconnection.

As described above, according to this embodiment, since the frequency selection element 40 and the switching element 30 are connected in parallel, noise of a specific frequency band passes through the frequency selection element 40, so the noise passing through the frequency selection element 40 reaches the heating element of the protection element 10. 12. The heating element 12 can be used to absorb the noise. Therefore, noise that adversely affects the protection device 20 can be reliably suppressed. Furthermore, since the protection circuit 2A is provided with the frequency selection element 40, noise can be easily absorbed, and there is no need to provide other members such as a noise absorption sheet. In particular, even in the case of suppressing noise in the low frequency region, there is no need to provide a thick noise absorbing sheet, and the protection circuit 2A or the battery pack 1 can be miniaturized. Furthermore, since the heating element 12 absorbs the noise passing through the frequency selection element 40, the noise can be suppressed inside the mobile device, and the influence of the noise on the human body can be reduced.

Fig. 2 is a circuit diagram schematically showing the configuration of the protection circuit of the second embodiment of the present invention. The protection circuit of the second embodiment is basically the same as the protection circuit 2A of the first embodiment. The same components are assigned the same reference numerals and their description is omitted. The following mainly describes the different parts.

As shown in FIG. 2, the protection circuit 2B includes: a protection element 10 having a fusible metal body 11 connected to the energization path, and a fusible metal body 11 connected to the fusible metal body 11 and capable of melting by heating Disconnected heating element 12; protection device 20, which detects abnormality of battery 3 connected to the above-mentioned energization path; and switching element 50, based on the detection result of protection device 20, to energize heating element 12 of protection element 10 Way of action.

The switching element 50 includes a semiconductor element having frequency selectivity for selectively outputting noise of a specific frequency band. The specific frequency band is, for example, 1 kHz to 1 GHz, preferably 1 kHz to 1 MHz. The semiconductor element is, for example, an FET. The FET is not particularly limited, and, for example, a junction FET or a MOS (metal oxide semiconductor) type FET can be used. In this embodiment, the gate of the FET is connected to the protection device 20 and the drain is connected to the heating element 12.

When the semiconductor element is an FET, it is preferable that the FET is arranged near a load that is a source of noise. Since there is a situation that a load such as a switching motor or a converter generates noise when it is switched, it is possible to suppress the noise that is just generated by arranging a FET near the load.

According to the second embodiment, the switching element 50 includes a semiconductor element having a frequency selection function in addition to a switching function. Therefore, the semiconductor element selectively outputs noise of a specific frequency band, and the noise output from the switching element 50 reaches the heating element 12 of the protection element 10, and the heating element 12 absorbs the noise. Therefore, the noise can be reliably suppressed, and the protection circuit 2B or the battery pack 1 can be miniaturized with a simple configuration, thereby reducing the influence of the noise on the human body. In addition, the protection circuit 2B can have a simpler structure, and the protection circuit 2B or the battery pack 1 can be made more compact.

The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments, and various changes and modifications can be made within the scope of the gist of the present invention described in the scope of the patent application.

For example, in the above embodiment, the protection circuits 2A and 2B are applied to the battery pack 1 of a lithium ion secondary battery, but it is not limited to this, and can be applied to various applications that require the use of electrical signals to block the energization path.

The protection element 10 is installed in mobile devices such as mobile phones, but is not limited to this, and can also be installed in various devices equipped with secondary batteries such as rechargeable electric machines. In addition, in the protection element 10, the fusible metal body 11 is melted and disconnected by the heat of the heating element 12, but it is not limited to this. When the energization path becomes an overcurrent situation, the fusible metal body 11 may be It melts and breaks by self-heating (Joule heat). According to this structure, the energization path of the protection element 10 or the battery 3 can also be blocked.

The protection device 20 detects the abnormality of the battery 3 connected to the energizing path, but it is not limited to this, and it can also detect other devices connected to the energizing path.

1: battery pack 2A: Protection circuit 2B: Protection circuit 3: battery 3A: Battery unit 3B: Battery unit 3C: battery unit 3D: battery cell 4: charging device 10: Protection element 11: Fusible metal body 11A: 1st fuse element 11B: 2nd fuse element 12: heating element 20: Protection device 30: switching element 40: frequency selection element 50: switching element

Fig. 1 is a circuit diagram schematically showing the configuration of the protection circuit of the first embodiment of the present invention. Fig. 2 is a circuit diagram schematically showing the configuration of the protection circuit of the second embodiment of the present invention.

1: battery pack

2A: Protection circuit

3: battery

3A: Battery unit

3B: Battery unit

3C: battery unit

3D: battery cell

4: charging device

10: Protection element

11: Fusible metal body

11A: 1st fuse element

11B: 2nd fuse element

12: heating element

20: Protection device

30: switching element

40: frequency selection element

Claims (10)

A protection circuit with: A protection element, which has a fusible metal body connected to the energization path, and a heating body connected to the above-mentioned fusible metal body and capable of melting and disconnecting the above-mentioned fusible metal body by heating; Protection device, which detects abnormalities of the machine connected to the above-mentioned power path; A switching element that operates by energizing the heating element of the protection element based on the detection result of the protection device; and The frequency selection element is connected in parallel with the above-mentioned switching element and passes noise of a specific frequency band. Such as the protection circuit of claim 1, wherein the above-mentioned specific frequency band is 1 kHz～1 GHz. Such as the protection circuit of claim 1 or 2, wherein the magnetic energy of the noise in the specific frequency band is converted into heat energy by the heating element. Such as the protection circuit of claim 1, wherein the frequency selection element is a high-pass filter. Such as the protection circuit of claim 1, wherein the above-mentioned machine is connected to the battery of the above-mentioned power path, The protection device detects the voltage of the battery, and determines whether the battery is abnormal based on the voltage. Such as the protection circuit of claim 1, which has: A protection element, which has a fusible metal body connected to the energization path, and a heating body connected to the above-mentioned fusible metal body and capable of melting and disconnecting the above-mentioned fusible metal body by heating; A protection device that detects abnormalities in the machine connected to the above-mentioned power path; and A switching element that operates by energizing the heating element of the protection element based on the detection result of the protection device; and The above-mentioned switching element includes a semiconductor element having frequency selectivity for selectively outputting noise of a specific frequency band. Such as the protection circuit of claim 6, wherein the above-mentioned specific frequency band is 1 kHz～1 GHz. Such as the protection circuit of claim 6 or 7, wherein the magnetic energy of the noise in the specific frequency band is converted into heat energy by the heating element. The protection circuit of claim 6, wherein the above-mentioned semiconductor element is a field effect transistor. Such as the protection circuit of claim 6, wherein the above-mentioned machine is connected to the battery of the above-mentioned power path, The protection device detects the voltage of the battery, and determines whether the battery is abnormal based on the voltage.

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