Battery pack

A battery pack that enhances the reliability and coupling force of a connection member electrically connecting two protective circuit boards is disclosed. The battery pack includes: a secondary battery including a positive electrode and a negative electrode; a first protective circuit board electrically connected to the battery; a second protective circuit board electrically connected to the first protective circuit board; and at least one conductive plate coupled to one surface of the first protective circuit board and one surface of the second protective circuit board.

CLAIM FOR PRIORITY

This application is based on and claims priority to Korean Patent Application No. 10-2008-0030049 filed on Mar. 31, 2008 in the Korean Intellectual Property Office (KIPO), the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery pack, and more particularly to, a battery pack that enables protective circuit boards coupled to a battery to have structures of high reliability and strong coupling forces.

2. Description of the Related Art

In recent years, compact and light portable electric and electronic appliances such as cellular phones, laptop computers, and camcorders are being actively developed and produced. Such portable electric and electronic appliances have embedded battery packs to allow operation even in places where there is no separate power source. Battery packs are currently employ chargeable and dischargeable batteries as they are more economical. Representative batteries include nickel-cadmium (Ni—Cd) batteries, Nickel-metal hydride (Ni-MH) batteries, lithium batteries, and lithium ion secondary batteries.

In particular, lithium ion batteries have operational voltages around three times higher than those of nickel-cadmium batteries or nickel-metal hydride batteries and are widely used as power sources for portable electronic appliances. In addition, lithium ion batteries are also widely used due to their relatively high energy density per weight.

In a lithium ion secondary battery used in a laptop computer, a plurality of battery cells are connected in series or in parallel in view of the increased power consumption and use time.

In this case, the lithium ion secondary battery for a laptop computer may be realized by a battery pack attachable to and detachable from the laptop computer.

Battery packs have various shapes according to the sizes and efficiencies of laptop computers with which the battery packs are used Since the laptop computers generally have very thin shape, the battery packs are also formed such that they have thicknesses within the thicknesses of the laptop computer.

Further, the battery packs that are detachably mounted to the laptop computers have protective circuits controlling the flows of currents of the batteries as the batteries become overheated, overcurrented, overcharged, overdischarged, or otherwise deteriorated.

In particular, a battery pack for a laptop computer generally employs a plurality of lithium ion secondary batteries, which has an increased possibility of danger. Accordingly, a smart protective circuit having more functions than a general protective circuit controlling one lithium ion secondary battery is mounted to such a battery pack. As the smart protective circuit has diversified functions, its mounting area becomes larger, in which case it occupies a considerable volume inside the battery pack.

In particular, a large amount of current flows through a connector of a battery pack that is connected to a contact portion of a battery of a laptop computer. The connector occupies a considerable space inside the battery pack.

Accordingly, a smart protective circuit is separated onto a board to which a connector is attached and a board to which a protective circuit is attached, in order to more efficiently utilize the interior space of a battery pack.

The separated boards are electrically connected to each other by an electric wire, and a current of up to several tens of Amperes flows through a portion of the electric wire to form a high current path between a positive electrode and a negative electrode of a battery.

However, if the electric wire is not big enough to allow sufficient current to flow, its resistance increases potentially causing overheating of the lithium ion secondary battery due to the obstructed current flow, which can cause explosion or deterioration of the battery. In addition, the coating of the electric wire may be melted by emission of heat, causing a short circuit with other signal wires. In this case, the protective circuit malfunctions or suffers damage, causing decrease of the reliability of the battery pack.

Moreover, the electric wire connecting the separated boards needs to have a sufficient coupling force so as not to be separated from the boards even when the boards are bent or the like in the process of assembling the battery pack.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made in view of the above problems, and the present invention provides a battery pack that improves the reliability of a connection member electrically connecting two protective circuit boards to each other.

The present invention also provides a battery pack that improves the coupling force of a connection member electrically connecting two protective circuit boards to each other.

In accordance with an exemplary embodiment of the present invention, there is provided a battery pack comprising: a secondary battery including a positive electrode and a negative electrode; a first protective circuit board electrically connected to the battery; a second protective circuit board electrically connected to the first protective circuit board; and at least one conductive plate coupled to one surface of the first protective circuit board and one surface of the second protective circuit board.

The conductive plate may include a body having bending regions, and a soldering portion for coupling the first protective circuit board and the second protective circuit to each other by soldering at least portions of the bending region to the first protective circuit board and the second protective circuit.

The at least one conductive plate may be a first conductive plate coupled to the first protective circuit board and the second protective circuit board and a second conductive plate coupled to the first protective circuit board and the second protective circuit board and spaced apart from the first conductive plate.

The first conductive plate may be electrically connected to the positive electrode of the battery and the second conductive plate may be electrically connected to the negative electrode of the battery.

The battery pack may further include a flexible printed circuit board (FPCB) formed between the first conductive plate and the second conductive plate to electrically connect the first protective circuit board and the second protective circuit board to each other. The flexible printed circuit board may be bent in shapes corresponding to the bending regions of the first conductive plate and the second conductive plate.

The conductive plate may have a first electrical connection region in contact with the first protective circuit board, a first bending region extending from the first electrical connection region, a connection region extending from the first bending region, a second bending region extending from the connection region, and a second electrical connection region extending from the second bending region and being in contact with the second protective circuit board.

The soldering portion may include a first soldering portion formed between the first bending region and the first protective circuit board and a second soldering portion formed between the second bending region and the second protective circuit board.

The first electrical connection region may have a shape corresponding to that of the second electrical connection region and is opposite to the second electrical connection region with respect to the center of the connection region, and the first bending region has a shape corresponding to that of the second bending region and is opposite to the second bending region with respect to the center of the connection region.

A central portion of the connection region may be bent so as to maintain the angle between the first protective circuit board and the second protective circuit board by 80 to 100 degrees.

A portion of the first electrical connection region that makes contact with the first protective circuit board may have a rectangular shape, and the soldering portion may have a box-like shape around the portion of the first electrical connection region that makes contact with the first protective circuit board.

The first bending region may have a first bending portion bent from the first electrical connection region and a second bending portion bent in a direction opposite to that of the first bending portion.

The soldering portion corresponding to the first protective circuit board may have a coupling area securing region formed between the first protective circuit board and the first bending portion and a coupling force reinforcing region connected to the coupling area securing region and being formed between the first protective circuit board and the second bending portion.

A distance between a first imaginary tangential line tangential to a full curve point of the first bending portion and a second imaginary tangential line tangential to a full curve point of the second bending portion may be within a range of 3 to 15% of the thickness of the conductive plate.

A distance from the lower surface of each conductive plate and the upper surface of the conductive plate spaced apart from the lower surface by the existence of the bending regions may be within a range of 150 to 250% of the thickness of the conductive plate. The thickness of the conductive plate may be 0.35 mm to 1.1 mm.

The first protective circuit board may include a first insulation substrate, a first printed circuit pattern coupled to the first insulation substrate, and a protective circuit electrically connected to the first printed circuit pattern, and the second protective circuit board includes a second insulation substrate, a second printed circuit pattern coupled to the second insulation substrate, and a protective circuit coupled to the second insulation substrate. The conductive plate may electrically connect the connector and the protective circuit to each other.

An area of one surface of each conductive plate that makes contact with the printed circuit board may be within a range of 70 to 90% of that of the printed circuit board.

The conductive plate may have soldering recesses around its surface making contact with the first protective circuit board and the second protective circuit board respectively.

The connection region is bendable so as to allow the second protective circuit to be mounted so as to extend in a direction that intersects the first protective circuit board.

The conductive plate has a first and a second electrical connection region that couples to the first and second protective circuit board and a connecting region that extends between the first and second electrical connection region, wherein the conductive plate is shaped so that the connection region is spaced from the electrical connection region to thereby permit greater access to the electrical connection regions at the place where the electrical connection regions are coupled to the first and second protective circuit boards for welding therebetween.

Accordingly, the battery pack of the present invention improves reliability by separating a conductive plate, i.e. a connection member electrically connecting two protective circuit boards to each other from a flexible printed circuit board.

Furthermore, the battery pack of the present invention improves coupling force by allowing a conductive plate, i.e. a connection member electrically connecting two protective circuit boards to each other, to strongly couple two protective circuit boards to each other.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used throughout the drawings to refer to the same or like elements, and descriptions of the same elements may not be repeated. Furthermore, detailed descriptions of the same or similar effects and operations of the embodiments incorporated herein may be omitted to avoid obscuring the subject matter of the present invention.

FIG. 1Ais a top view illustrating a battery pack according to an embodiment of the present invention.FIG. 1Bis a front view of the battery pack illustrated inFIG. 1A.FIG. 1Cis a top view ofFIG. 1Awith a multi-cell battery of the battery pack being removed.FIG. 1Dis a top view in which a first protective circuit board and a second protective circuit board are in parallel to each other by deploying the first circuit board illustrated inFIG. 1ain the direction of an arrow.FIG. 1Eis a bottom view ofFIG. 1DwithFIG. 1Dbeing viewed from the bottom.FIG. 1Fis a partially cross-sectional view taken along line I-I ofFIG. 1E.FIG. 1Gis a perspective view of a conductive plate illustrated inFIG. 1E.FIG. 1His a partial bottom view obtained by enlarging a region1hillustrated inFIG. 1E.FIG. 1Iis a partially cross-sectional view obtained by enlarging a region1iillustrated inFIG. 1E.

As illustrated inFIGS. 1A to 1I, the battery pack10according to an embodiment of the present invention includes a multi-cell battery100, a first protective circuit board200, a second protective circuit board300, a pair of conductive plates400, and a pair of soldering portions500. The battery pack10further includes a flexible printed circuit board600.

The multi-cell battery100includes a plurality of battery cells101. In this case, the battery100is a rechargeable lithium ion battery and has a positive electrode110and a negative electrode120. The battery cells101are connected in series or in parallel to each other to form the battery100having the positive electrode110and the negative electrode120. The battery cells101are electrically connected to each other through lead tabs. In the embodiment of the present invention, the plurality of battery cells101form a battery but one battery cell may form a battery.

The first protective circuit board200includes a first insulation substrate210, a first printed circuit pattern220, and a protective circuit230.

The first insulation substrate210is formed of a resin such as epoxy resin or bakelite. A plurality of layers may be compressed in the first insulation substrate210, and a via hole passing through the upper and lower surfaces of the first insulation substrate210may be formed in the first insulation substrate210.

The first printed circuit pattern220is compressed and is adhered to the first insulation substrate210. The first printed circuit pattern220is formed on the upper and lower surfaces of the first insulation substrate210. The first printed circuit pattern220is inserted into an intermediate layer of the first insulation substrate210.

The protective circuit230is electrically connected to the first printed circuit pattern220. The protective circuit230is positioned on the first insulation substrate210. The protective circuit230controls electrical connection for charge and discharge of the battery100according to the voltage of the battery100. More particularly, the protective circuit230includes a passive device, a charge field effect transistor (FET), a discharge FET, a temperature device, and a control circuit. In this case, the control circuit turns on or off the charge FET and the discharge FET during charge of the battery100to charge or discharge the battery100. When the temperature device detects that the temperature of the battery100is above a predetermined value, the control circuit turns off the charge FET and the discharge FET to prevent the battery100from being overheated. The control circuit detects the voltage of the battery100, and recognizes an overcharge or overdischarge state of the battery100according to the detected voltage. In this case, the control circuit turns off the charge FET to prevent a charge operation of the battery100or turns off the discharge FET to prevent a discharge operation of the battery100. When an over-current flows through the battery100, the control circuit protects the battery100by turning off the charge FET and the discharge battery. The control circuit calculates the charge/discharge cycle of the battery100, and extends the lifespan of the battery by controlling charge current according to the calculated charge/discharge cycle.

The second protective circuit board300includes a second insulation substrate310, a second printed circuit pattern320, and a connector330and also includes a second protective circuit. When the mounting space of the first protective circuit board200is narrow, the elements of the protective circuit230may be selectively mounted to the second protective circuit board300. In this case, the second protective circuit board300is electrically connected to the first protective circuit board200through the protective plates400and a flexible printed circuit board600.

The second insulation substrate310has the same or similar shape and material as those of the first insulation substrate210, and detailed descriptions thereof will be omitted.

The second printed circuit pattern320is formed on the upper and lower surfaces and an intermediate layer of the second insulation substrate310. The second printed circuit pattern320is formed in a via hole of the second insulation substrate310. The second printed circuit pattern320is formed of the same conductive metal, such as copper, as that of the first printed circuit pattern220.

The connector330is coupled to one surface of the second insulation substrate310. The connector330includes a plurality of contact terminals and a case surrounding the contact terminals. The connector330is adapted to supply a high current of the positive electrode110and the negative electrode120of the battery100that flows through the first conductive plate410and the second conductive plate420to portable electronic appliances such as laptop computers. In this case, the conductive plates400electrically connect the connector330and the protective circuit230to each other to allow the protective circuit230to function as an electrical passage for protecting the battery100.

The second protective circuit board300to which the connector330is mounted is separated from the first protective circuit board200, in which case the position of the connector330in contact with contact terminals of a battery of a portable electronic device may be easily secured during manufacturing of a battery pack. The conductive plates400electrically connect the first protective circuit board200and the second protective circuit board300to each other and firmly couple the two boards to each other, enabling manufacturing of a battery pack having a stable structure.

The conductive plates400are a first conductive plate410and a second conductive plate420. In this case, the first conductive plate410is electrically connected to the positive electrode110of the battery100and the second conductive plate420is electrically connected to the negative electrode120of the battery100. In other words, the conductive plates400correspond to a charge/discharge high current path of the battery100. The conductive plates400are formed of nickel or a nickel alloy to enhance conductivity and the coupling forces between the conductive plates400and the soldering portions500during its coupling to the printed circuit pattern.

The first conductive plate410includes a first electrical connection region411, a first bending region412, a connection region413, a second bending region414, and a second electrical connection region415.

The first electrical connection region411is electrically connected to the first protective circuit board200. In this case, as illustrated inFIG. 1H, a portion of the first electrical connection region411that makes contact with the first protective circuit board200has a rectangular shape, and the soldering portion500has a box-like shape around the portion of the first electrical connection region411that makes contact with the first protective circuit board200. Accordingly, the first conductive plate410improves the coupling force between the first conductive plate410and the first protective circuit board200, thereby providing a stable structure. The rectangular edges of the first connection region411may be chamfered so as to be rounded.

The area of one surface of each conductive plate400that makes contact with the second printed circuit pattern320is made to be more than 70% of that of the second printed circuit pattern320to improve the conductivity between the conductive plate400and the second printed circuit pattern320. Further, the area of one surface of each conductive plate400that makes contact with the second printed circuit pattern320is made to be less than 90% of that of the second printed circuit pattern320to provide a coupling space in which the soldering portion500is soldered.

The first bending region412includes a first bending portion412aand a second bending portion412b.

The first bending portion412aextends from the first electrical connection region411, and is bent from the end of the first electrical connection region411. The first bending portion412ais bent counterclockwise at the first electrical connection region411to form an arc shape. Accordingly, an area where the soldering portion500can be soldered increases between the first protective circuit board200and the first bending portion412a, thereby increasing the coupling force between the conductive plate400and the first protective circuit board200.

The second bending portion412bextends from the first bending portion412a. The second bending portion412bis bent clockwise to form an arc shape. The second bending portion412bis bent in the direction opposite to the first bending portion412, so that the first electrical connection region411and the connection region413are substantially parallel to each other.

The distance D10between a first imaginary tangential line D11tangential to a full curve point of the first bending portion412aand a second imaginary tangential line D12tangential to a full curve point of the second bending portion412bis within a range of 3 to 15% of the thickness of the conductive plate400. In other words, when the distance D10is above 3% of the thickness of the conductive plate400, the first bending portion412aand the second bending portion412bmay be sufficiently bent to increase the coupling area between the conductive plate400and the soldering portion500. On the other hand, if the distance D10between the first tangential line D11and the second tangential line D12is above 15% of the thickness of the conductive plate400, when the first bending portion412aand the second bending portion412are excessively bent, the coupling area between the conductive plate400and the soldering portion500decreases, weakening the coupling force between the conductive plate400and the soldering portion500. Accordingly, the distance D10needs to be within a range between 3 to 15% to maintain the coupling force of the soldering portion500.

The connection region413extends from the second bending portion412b. In addition, the connection region413is parallel to the first electrical connection region411.

A central portion of the connection region is bent to maintain the angle between the first protective circuit board200and the second protective circuit board300within a range of 80 to 100 degrees. The conductive plate400is bent as illustrated inFIG. 1b. Accordingly, the first protective circuit board200having the protective circuit and the second protective circuit board300having the connector330may be easily mounted longitudinally and transversely inside the battery pack.

The second bending region414extends from the connection region413and includes bending portions414aand414b. The bending portions414aand414bhave shapes corresponding to those of the first bending portion412aand the second bending portion412bof the first bending region412. In other words, each conductive plate400is symmetrical with respect to a reference line vertical to the length of the conductive plate400, the reference line being positioned at the center of the connection region413. Accordingly, detailed descriptions of the bending portions of the second bending region414will be omitted.

The second electrical connection region415extends from the bending portion of the second bending region414and is electrically connected to the second protective circuit board300. The second electrical connection region415has a shape corresponding to that of the first electrical connection region411, and only the relation with which the second electrical region415is coupled to the second protective circuit board300is different from the case of the first electrical connection region411. Accordingly, detailed descriptions of the second electrical connection region415will be omitted.

The second conductive plate420is electrically connected to the negative electrode120of the battery100. In this case, the second conductive plate420is spaced apart from the first conductive plate410to prevent its short circuit with the first conductive plate410. The second conductive plate420has the same or similar shape and material as those of the first conductive plate410, and detailed descriptions thereof will be omitted.

Meanwhile, as illustrated inFIG. 1I, the distance D20from the lower surface of each conductive plate400and the upper surface of the conductive plate400spaced apart from the lower surface by the existence of the bending regions412and414is within a range of 150 to 250% of the thickness T10of the conductive plate400. In the embodiment of the present invention, the thickness of each conductive plate400is 0.35 mm to 1.1 mm. When the distance D20is below 150% of the thickness T10of the conductive plate400, the space for the soldering portion500becomes too small, seriously decreasing the coupling force between the conductive plate400and the protective circuit board. On the other hand, when the distance D20is above 250% of the thickness T10of the conductive plate400, the bending regions412and414of the conductive plate400become too long, unnecessarily increasing the mounting volume of the conductive plate400. Meanwhile, when the thickness T10of each conductive plate400is below 0.3 mm, the strength of the conductive plate400becomes too weak, causing the conductive plate400to be bent even by a small impact and to be short-circuited. On the other hand, when the thickness T10of each conductive plate400is below 1.1 mm, it is difficult to form bending portions of the bending regions412and414, decreasing the coupling area of the soldering portion510, in which case the coupling force between the conductive plate400and the protective circuit boards200and300may be weakened.

Each soldering portion500couples at least one portion of the first bending region412of the first conductive plate400to the first protective circuit board200using solder. The soldering portion500couples at least one portion of the first bending region412of the first conductive plate400to the second protective circuit board300using solder.

As illustrated inFIG. 1F, the soldering portions500are a first soldering portion510formed between the first bending region412and the first protective circuit board200and a second soldering portion520formed between the second bending region414and the second protective circuit board300. In other words, the first soldering portion510is coupled to the first protective circuit board200and the second soldering portion520is coupled to the second protective circuit board300. Accordingly, when the centers of the conductive plates400are bent, the conductive plates400have strong coupling forces so as not to be separated from coupling surfaces of the first protective circuit board200and the second protective circuit board300.

As illustrated inFIG. 1I, the first soldering portion510includes a coupling area securing region511and a coupling force reinforcing region512. The second soldering portion520also includes a coupling area securing region and a coupling force reinforcing region and has a shape corresponding to that of the first soldering portion510, in which case detailed descriptions thereof will be omitted.

The coupling area securing region511is formed between the first protective circuit board200and the first bending portion412a. In other words, the coupling area securing region511is filled between the first bending portion412abetween the first electrical connection region411and the second bending portion412b, and the first protective circuit board200, maximally increasing the coupling area between the conductive plate400and the first protective circuit board200.

The coupling force reinforcing region512extends from the coupling area securing region511and is formed between the first protective circuit board200and the second bending portion412b. The coupling force reinforcing region512supports the coupling area securing region511for securing coupling area, further, enhancing the coupling force between the conductive plate400and the protective circuit board300.

The flexible circuit board circuit board (FPCB)600is formed between the first conductive plate410and the second conductive plate420and electrically connects the first protective circuit board200and the second protective circuit board300to each other. The flexible printed circuit board600includes a plurality of copper foils and an insulation film coating the copper foils. In the flexible printed circuit board600, the copper foils are coated with the insulation film with them being disposed side by side in a row and are integrated with the insulation film. The flexible printed circuit board600functions as an electrical passage through which a signal about the voltage of the battery100and control signals of the protective circuits are transmitted.

As shown inFIG. 1B, the flexible printed circuit board600is bent so as to have a shape corresponding to those of the bending regions412and414of the conductive plate400. When a central portion of the conductive plate400is bent with the flexible printed circuit board not being deflected in a shape corresponding to the conductive plate400, the central portion of the flexible printed circuit board600is excessively deflected and portions of the flexible printed circuit board600that are coupled to the printed circuit boards200and300may be separated. Accordingly, the flexible printed circuit board600is bent in a shape corresponding to the bending regions412and414of the conductive plate400, preventing it from being separated from the protective circuit boards200and300.

As mentioned above, the battery pack10according to the embodiment of the present invention allows the flow of a high current of the battery100using the conductive plates400and transmits only signals using the flexible printed circuit board600. In other words, the protective circuit boards200and300have little possibility of being melted or short-circuited by the heat of the high current path unlike existing protective circuit boards using one flexible printed circuit board for signals and a high current path, enhancing the reliability of the battery pack10.

Furthermore, the conductive plates400of the battery pack10that electrically connect the protective circuit boards200and300to each other are strongly coupled to the protective circuit boards200and300, providing a stable structure.

FIG. 2is a perspective view of a conductive plate of a battery pack according to another embodiment of the present invention.

Referring toFIG. 2, the battery pack according to the embodiment of the present invention includes a multi-cell battery (not shown), a first protective circuit board (not shown), a second protective circuit board (not shown), at least one conductive plate1400, and soldering portions (not shown). The battery pack according to the embodiment of the present invention further includes a flexible printed circuit board (not shown).

In the embodiment of the present invention, the multi-cell battery (not shown), the first protective circuit board (not shown), the second protective circuit board (not shown), the soldering portions (not shown), and the flexible printed circuit board (not shown) are the same or similar as those of the former embodiment of the present invention, and detailed descriptions thereof will be omitted. In the embodiment of the present invention, a modified conductive plate1400will be mainly described.

The conductive plate1400includes a first electrical connection region1410, a first bending region1420, a connection region1430, a second bending region1440, and a second electrical bending region1450.

The first bending region1420, the connection region1430, and the second bending region1440have the same shapes as those of the former embodiment of the present invention, and detailed descriptions thereof will be omitted.

Soldering recesses1460are formed in the first electrical connection region1410and the second electrical connection region1450respectively. The soldering recesses1460are formed at side portions of the first electrical connection region1410and the second electrical connection region1450that make contact with the first protective circuit board and the second protective circuit board respectively. The soldering recesses1460increase the areas of the first electrical connection region1410and the second electrical region1450, increasing the coupling area where the soldering portions are coupled. Accordingly, the conductive plate1400enhances the coupling forces between the conductive plate1400and the first protective circuit board and the second protective circuit board.

As mentioned above, the battery pack according to the embodiment of the present invention has the soldering recesses1460in the conductive plate1400, enhancing the coupling forces between the conductive plate1400and the first protective board and the second protective circuit board.

Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may appear to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention as defined by the appended claims.