Abstract:
The objective of the present invention is to provide an information processing device that is operable by a battery and which suppresses the generation of standing waves and has little radiation noise. In the information processing device of the present invention having means for connecting to a battery pack that stores a battery for supplying power to the information processing device, there is one or more capacitive element (for example, a capacitor) in the proximity of the terminals of the positive and negative poles of the battery when the battery pack is connected to the information processing device, and it is possible for at least the terminal of the positive pole of the battery or the terminal of the negative pole of the battery to be connected electrically to the ground of the information processing device by way of this capacitive element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an information processing device that is capable of being operated by battery, and in more particular, to the mounting and power-supply configuration of the battery for a notebook type personal computer. 
     2. Description of Related Art 
     There are notebook type personal computers that are used, for example, as in the case of the notebook type computer device disclosed in Japanese Patent Application Publication Heisei 5-143192, wherein a battery pack of rechargeable secondary batteries (hereafter called batteries) is mounted in the main body. In many cases the battery pack is detachable/attachable from the notebook computer, and in order to avoid being partially inserted due to mishandling by the operator such that only the positive or negative power-supply wire is connected, the distance between the two power-supply terminals is made as short as possible when it is connected to the notebook PC. 
     SUMMARY OF THE INVENTION 
     As shown in FIG. 12, if the battery pack  50 , as described above, contains batteries with a negative terminal on the opposite side of the positive terminal, positive  54  and negative  53  power-supply wires must run from both ends of the battery  56 . 
     In the case of this kind of construction, the impedance from the supply terminal  57  for supplying current to the notebook PC to the battery terminals  51 ,  52  is a minimum at the supply terminal  57 , and is a maximum at the battery terminals  51 ,  52 . Therefore, if noise generated from the LSI or signal wires in the notebook PC  58  is transferred as high-frequency current to the power-supply wires  53 ,  54  in the battery pack, reflection occurs at the battery terminals  51 ,  52 , and by superimposing the reflected waves with the incident waves, a standing wave, whose wavelength is equal to double the length of the power-supply wire L 55 , is generated (see FIG.  13 ). Therefore, the power-supply wires  53 ,  54  act as an antenna and make it easy to radiate noise to the outside. 
     The object of this invention is to provide an information processing device that is operable with battery which has little radiation noise and which suppresses the generation of standing waves. 
     In order to accomplish the aforementioned object, the present invention provides, in an information processing device with means which connects to a battery pack that stores a battery for supplying power to the information processing device, for example, at least one capacitive element (for example a capacitor) mounted in the proximity of the terminals of the positive and negative poles of the battery when the battery pack is connected to the information processing device. At least the terminal of the positive pole of the battery or the terminal of the negative pole of the battery may be connected electrically to the ground of the information processing device through this capacitive element. Here, what is meant by proximity is, for example, between the positive or negative pole and the terminal, or between the positive or negative pole of the battery and the circuit first connected by the battery. 
     It is also possible to connect the terminal of the negative pole of the battery to the ground of the information processing device without the capacitive element. 
     In addition, this invention provides a battery pack comprising means in the proximity of at least the positive terminal or negative terminal of the battery for connecting electrically the positive terminal or negative terminal of the battery to the ground of the information processing device. 
     It is possible to provide a capacitive element between the terminal of the positive pole of the battery and the terminal of the negative pole of the battery, and to connect the terminal of the positive pole and the terminal of the negative pole of the battery through the capacitive element. 
     Moreover, the present invention provides, for example, an information processing device comprising at least one capacitive element and at least one of means which connects electrically between the capacitive element and the terminal of the positive pole of the battery or the terminal of the negative pole of the battery, wherein the capacitive element connects electrically to ground. 
     Here, the means which connects electrically to the terminal of the negative pole of the battery can be connected electrically to ground without the capacitive element. 
     Moreover, the present invention provides, for example, a battery pack comprising capacitive elements and means provided in the proximity of the terminal of the positive pole of the battery and terminal of the negative pole of the battery, respectively, for connecting the capacitive elements and the ground of the information processing device, wherein the terminal of the positive pole of the battery and the terminal of the negative pole of the batter are connected electrically to ground through the capacitive elements provided in the proximity of the terminal of the positive pole of the battery and terminal of the negative pole of the battery, respectively. 
     Here, it is also possible to connect the terminal of the negative pole of the battery to ground without the capacitive element. 
     The present invention also provides a battery, for example, comprising a capacitive element wherein the positive pole and the negative pole of the battery are connected electrically through the capacitive element. 
     Moreover, the present invention provides an information processing device, for example, comprising a ground connector provided between both ends of the battery pack and the connector which electrically connects the positive pole and negative pole of the battery. 
     Furthermore, this invention provides an information processing device, for example, comprising a ground connector located between both ends of the battery pack and the connector which electrically connects the positive pole and negative pole of the battery and within a distance of ¼ or preferably ⅕ the length of the battery pack from the both ends of the substrate of the battery pack. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a drawing which explains a first embodiment of the present invention; 
     FIG. 2 is a drawing of the first embodiment constructed with a capacitor inside the notebook PC; 
     FIG. 3 is a drawing of the first embodiment constructed with a capacitor inside the battery; 
     FIG. 4 is a drawing of the first embodiment constructed using a coil; 
     FIG. 5 is a drawing which explains a second embodiment of the present invention; 
     FIG. 6 is a drawing of the second embodiment constructed using a coil; 
     FIG. 7 is a drawing of the second embodiment constructed with a capacitor inside the notebook PC; 
     FIG. 8 is a drawing of the second embodiment constructed with a capacitor inside the battery; 
     FIG. 9 shows an example of applying the second embodiment to a battery pack which has a power-supply wire on one of the battery terminals; 
     FIG. 10 is a drawing of the second embodiment constructed such that a positive terminal and a negative terminal of the battery are connected by way of a capacitor; 
     FIG. 11 is a general view showing the first embodiment of the present invention; 
     FIG. 12 is a drawing which explains the problems to be solved; 
     FIG. 13 shows the current distribution of the power-supply wires; 
     FIG. 14 is a diagram showing the connected state of the notebook PC and the battery; 
     FIG. 15 is an exterior view of the battery pack; 
     FIG. 16 is a diagram showing the installation of the ground connection fittings on the PC side; 
     FIG. 17 is a diagram showing the construction of the secondary battery charging power supply and control substrate inside the battery pack; 
     FIG. 18 is a diagram showing the noise reduction theory of a third embodiment; 
     FIG. 19 is a graph showing the relationship between the antenna length of the dipole antenna and the power-supply efficiency; and 
     FIGS. 20A and 20B are diagrams showing the noise reduction effect according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will be explained with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. The circuit in the drawing comprises a battery  2 , a negative terminal  12  of the battery  2 , a positive terminal  13  of the battery  2 , a power-supply wire (+)  3  which runs from the positive terminal  13  of the battery, a power-supply wire (−)  4  which runs from the negative terminal  12  of the battery, and power-supply terminals (+)  5 , (−)  11  for supplying current from the battery  2  to the electronic device. The power-supply wires (+)  3  and (−)  4  connect the power-supply terminals (+)  5  and (−)  11  from the positive terminal  13  and negative terminal  12  on both sides of the battery  2  and arrange the power-supply terminals (+)  5  and (−)  11  so as to close the distance therebetween. Furthermore, there are capacitors  8  connected to the negative terminal  12  and positive terminal  13  of the battery  2 , and they connect to ground  10 . The battery current  14  is direct current so it flows to the terminals without passing through the capacitors  8 . On the other hand, a high-frequency current (noise component)  15  flows through the capacitors  8  to ground  10 . Therefore, there is a reduction in the reflection of the high-frequency current (noise component) at the terminals, making it difficult for a standing wave whose wavelength corresponds to the length of the power-supply wire L 55  to be generated, and it possible to control the radiated noise. 
     In addition, as shown in FIG. 4, it is possible to reduce noise by connecting coils  41  in series with negative terminal  12  and positive terminal  13  of the battery  2 . At high frequency, the impedance of the coils  41  becomes higher than that of the capacitors  8 , so the high-frequency current flowing to the terminals is reduced, and thus it is possible to reduce the reflection at the terminals. Therefore, a standing wave is hardly generated and it is possible to suppress the radiated noise. 
     Next, FIG. 2 shows an example of applying the first embodiment to a notebook PC  24 . The construction of the battery pack  1  shown in the figure comprises a battery  2 , power-supply wire (+)  3 , power-supply wire (−)  4 , power-supply terminal (+)  5  and power-supply terminal (−)  11  for supplying current from the battery  2  to the notebook PC  24 . The battery  2  is not limited to a single battery but can be constructed with a plurality of battery cell connected in series or parallel, and it comprises a positive terminal  13  and negative terminal  12 . The connector  6  connects the negative terminal  12  and power-supply wire (−)  4 , and the connector.  7  connects the positive terminal  13  and the power-supply wire (+)  3 , and can be a fitting, metal plate, etc. Furthermore, the connectors  6  and  7  have connection terminals  21 ,  22 , respectively, that connect to the notebook PC  24 . There are capacitors  23  in the notebook PC  24 , and they connect the connection terminals  21 ,  22  to ground  25  of the notebook PC  24  through the capacitors  23 . It is desirable that the ground  25  is a common return wire with the signal (signal ground) on the board of the notebook PC  24 . In this way, it is possible to construct a notebook PC  24  with battery pack  1  in which radiation noise is hardly generated. 
     FIG. 11 is a general view of an example of the notebook PC  24  with battery pack  1 . The battery pack  1  comprises connection terminals  21 ,  22 , a power-supply terminal (+)  5  and power-supply terminal (−)  11 . The notebook PC  24  comprises connection terminals  121 ,  122  that connect to the connection terminals  21 ,  22 , and power-supply terminals  115 ,  111  that connect to the power-supply terminals (+)  5 , (−)  11 . In FIG. 11, only the electrical connection is shown, however, it is also possible to install means for a physical connection, such as fasteners or the like, and battery control signal wires. 
     Next, FIG. 3 shows an example of the battery pack  30  when capacitors are installed in the battery pack and notebook PC  34 . The configuration of the battery pack  30  shown in this figure comprises a battery  2 , power-supply wires (+)  3  and (−)  4 , and power-supply terminals (+)  5  and (−)  11  for supplying current from the battery  2  to the notebook PC  34 . Connector  6  connects the negative terminal  12  of the battery  2  with the power-supply wire (−)  4 , and connector  7  connects the positive terminal  13  of the battery  2  with the power-supply wire (+)  3 . Furthermore, the connector  6  and connector  7  connect to the ground  32  of the battery pack  30  through capacitors  31 . The ground  32  of the battery pack  30  can be, for example, a conductive plate. Moreover, a terminal  35  connects the ground  32  of the battery pack  30  with the ground  36  of the notebook PC  34 . In this way, it is possible to construct a notebook PC  34  with battery pack  30  in which radiated noise is hardly generated. 
     Next, FIG. 5 shows a second embodiment of the present invention in which a power-supply wire (−)  4  is connected directly to ground  10  without the use of a capacitor. A power-supply wire (+)  3  connect to ground  10  through a capacitor  8  in the same way as in the first embodiment shown in FIG.  1 . In this way as well, high-frequency current (noise component) flows to ground  10  so that it is possible to reduce the reflection at the terminals, and it is possible to suppress radiated noise that is caused by generation of standing waves. 
     Furthermore, as shown in FIG. 6, it is also possible to install coils  41  at the negative terminal  12  and positive terminal  13  of the battery  2 . For high frequency, the impedance of the coils  41  is higher than that of the capacitor  8 , so it is possible to reduce the high-frequency current that flows in the terminals, as well as reduce the reflection at the terminals. Therefore, it is possible to suppress the radiated noise that is caused by generation of standing waves. 
     Next, FIG. 7 shows an example of applying the second embodiment in a notebook PC  71 . A capacitor  23  is located in the notebook PC  71 , the connection terminal  22  connects to the ground  75  of the notebook PC  71  through the capacitor  23 , and the connection terminal  21  connects directly to the ground  75  of the notebook PC  71 . In addition, by connecting the battery pack  1 , which was explained in the example of applying the first embodiment to the notebook PC  24 , to the notebook PC  71 , it is possible to construct a notebook PC  71  with battery pack  1  in which radiated noise is hardly generated. 
     Furthermore, it is also possible to install a capacitor inside the battery pack  80  (see FIG.  8 ). The connector  6  connects the negative terminal  12  of the battery  2  with the power-supply wire (−)  4 , and the connector  7  connects the positive terminal  13  of the battery  2  with the power-supply wire (+)  3 . In addition, a capacitor  31  is installed so that the connector  7  is connected to the ground  32  of the battery pack  80  through the capacitor  31 , while the connector  6  is connected directly to the ground  32  of the battery pack  80 . Also, the ground  32  of the battery pack  80  is connected to the ground  36  of the notebook PC  34  through the connection terminal  35 . In this way, it is possible to construct a notebook PC  34  with battery pack  80  in which radiated noise is hardly generated. 
     Moreover, it is possible to locate the power-supply terminal for supplying current from the battery to the notebook PC near one of the battery terminals instead of in the center of the battery pack. For example, FIG. 9 shows an example of a battery pack  90  in which the both the positive and negative power-supply terminals are located near the negative terminal of the battery  2 . The power-supply terminals (−)  91  and (+)  92  are located near the negative terminal  12  of the battery  2 , and the connection terminal  93  is located at the connector  7 . Also, it is possible to arrange a capacitor  23  inside the notebook PC  96  and to connect the connection terminal  93  to the ground  97  of the notebook PC  96  through the capacitor  23 . In this example, the power-supply terminals (−)  91 , (+)  92  are located near the negative terminal  12 , however it is also possible to locate them on the side of the positive terminal  13 . Also, it is possible to locate the capacitor  23  inside the battery pack  90 . 
     It is further possible to connect the positive terminal and the negative terminal of the battery by a capacitor. FIG. 10 shows an example of a battery pack  100  in which the positive terminal  13  and the negative terminal  12  are connected by a capacitor  31 . The connectors  6  and  7  of the battery terminals  12 ,  13  are connected by the capacitor  31 , and a connection terminal  101  is located at the connector  6  which is connected to the negative terminal  12  of the battery  2 . This connection terminal  101  connects to the notebook PC  102 , and can be connected to the ground  103  of the notebook PC  102 . In this example, the connection terminal  101  is located at the connector  6 , however it is also possible to locate it at the connector  7 . 
     It is also possible to place the capacitor  31  inside the notebook PC  102 . The power-supply terminals (−)  11 , (+)  5  are connected via the capacitor  31  installed in the notebook PC  102 . The connection terminal connects to the ground of the notebook PC  101 . 
     Next, FIGS. 14 through 20 will be used to explain the application of a third embodiment to a notebook PC. FIG. 14 shows the state of a battery pack  502  mounted to a notebook PC  500 . The notebook PC  500  of this embodiment is a portable type with a width of 283 mm and depth of 235 mm, and the battery pack  502  is mounted to the outside of the PC body  501  through power-supply connectors  520  and  522 . Moreover, the ground of the circuit board  510  of the notebook PC  500  is connected to the ground of the battery pack  502  through the ground connection fittings  531  and  532  on the battery pack  502 , and the ground connection fittings  541  and  542  on the PC  500 . 
     FIG. 15 shows the shape of the battery pack  502 . The battery pack  502  is constructed so as to hold six secondary rechargeable batteries  505 , and a secondary rechargeable battery power supply and control board  575 , and it is nearly rectangular solid with a length L of 203 mm, depth of 24 mm and height of 21 mm. This battery pack  502  has a power-supply connector  520  which is located at almost center and at 85.5 mm from the end of the battery pack. In order to prevent poor connection due to only one side being connected, the power-supply connector  520  is located around the center of the battery pack  502  so that the battery pack can be held by the guides  507 ,  508  on the side of the board and by the power-supply connector  520 . Also, at positions 16 mm ( 16 / 203 &lt;⅕) and 26.5 mm ( 26 . 5 / 203 &lt;⅕) from the end of the battery pack  502 , or in other words, at a position from both ends of the battery pack  502  at a distance of ⅕ or less the full length of the battery pack  502 , there are ground connection fittings  531  and  532  which connect electrically to the ground of the secondary rechargeable battery power supply and control board  575 . These connection fittings  531 ,  532  are formed in a protruding shape from a thin spring-like plate such as phosphor bronze. Therefore, it is possible to minimize the connection resistance between them and the connecting surface with the ground connection fittings  541  and  542  of the PC  500 , and thus the connection has low impedance even in the high frequency range. 
     FIG. 16 shows the installation state of the ground connection fitting  541  of PC  500 . The ground connection fitting  541  is fastened to the PC circuit board  510  at the screw hole  545 . When fastening it, there is a ground pad  519  in the screw hole  545  on the side of the PC circuit board  510 , and by fastening the circuit board  510  to the ground connection fitting  541  with a screw, it is possible to connect the circuit board  510  with the ground connection fitting  541  so that there is low impedance even in the high frequency range. Also, the ground connection fitting  541  can be a thin spring-like plate such as phosphor bronze as in the case of the ground connection fittings  531 ,  532  of the battery, and the end is formed in a protruding circular shape. The protruding circular shaped section is formed so that it sticks out of the window formed in the body  501  of the PC  500 . With this kind of structure, the protruding circular shaped section is pressed against and comes in contact with the ground connection fitting  531  of the battery, when the battery pack  502  is installed, making it possible to connect the circuit board  510  of the PC  500  and the secondary rechargeable battery power supply and control board  575  of the battery pack  502  with low impedance even in the high frequency range. 
     FIG. 17 shows the wiring of the secondary rechargeable battery power supply and control board  575  of the battery pack  502 . The board  575  is a two-layered board with a signal wiring layer  576  and ground layer  577 . The wire  578  for the positive terminal and the wire  578  for the negative terminal are wired on the signal wiring layer  576  from the power-supply connector  520 . The wire  578  for the positive terminal and the wire  579  for the negative terminal connect to the secondary rechargeable battery  505 . Also, on the board  575 , there are ground pads  533 ,  534  for connecting the ground connection fittings  531  and  532 . The ground layer  577  functions as the reference potential for the circuits for battery control located on the board, so it has a planar shape. 
     FIG. 18 shows a noise generation model of the battery pack  502 . The wire  578  for the positive terminal and the wire  579  for the negative terminal shown in FIG. 17 are wired in opposite directions on the left and right and supply power to the positive and negative terminals of the secondary rechargeable battery  505 , respectively, and when the construction is not that of this invention, they form a half-wavelength dipole antenna and become a source of radiated noise. On the other hand, the ground layer  577  is connected with low impedance to the ground of the PC through the pads  533 ,  534 . Also, the wire  578  for the positive terminal and the wire  579  for the negative terminal have micro stripwire construction and with the ground layer  577  of the planar construction, and the wire  578  for the positive terminal and the wire  579  for the negative terminal have a capacitive coupling with the ground layer  577 . Generally, large current flows through the wire  578  for the positive terminal and the wire  579  for the negative terminal and are made of wide wire, so the capacitance between the terminal wires  578 ,  579  and the ground layer  577  is sufficiently large, and both are coupled with low impedance in high frequency. Therefore, it is possible for the terminal wires  578 ,  579  and the PC ground to be coupled with low impedance even in the high-frequency range. In this way, the noise that emerges from the power-supply connector  520  is reduced through the ground connection ( 531 - 541 ,  532 - 542 ). 
     Next, FIG. 19 shows the measurement results of the radiation efficiency at two frequencies for the noise component that does not return to the PC from the ground connection ( 531 - 541 ,  532 - 542 ). The upper graph shows the result in a low frequency and the lower graph shows the result in a high frequency. The vertical axis of this graph shows the radiated power in decibels when the antenna length is changed, based on the radiated power of a half-wavelength dipole antenna as a reference. The horizontal axis of the graph is the length ratio, with half the length of the battery pack ½L taken as being 1. The value of the power of the ideal dipole antenna is used as the calculated value of this radiated power. The value of the radiated power differs depending on the surface skin depth at the target frequency, so in the graph shown in FIG. 19, there is a gap in the values of the radiated power. When the ground connection ( 531 - 541 ,  532 - 542 ) position is ¼ the length of the battery pack (0.5 on the X axis), the radiation efficiency drops to −20 dB in the worst case, however there is no problem on the outside of the ground connection ( 531 - 541 ,  532 - 542 ) position, even if becoming an antenna. 
     Moreover, with respect to the standing waves that are generated in the terminal wires  578 ,  579 , since they are connected to ground at the points of the pads  533 ,  534 , the waveform becomes a node at this point, and waves whose wavelength are ⅕ or less than the basic wave (the frequency is 5×) becomes the main component. However, in the case of trapezoidal waves that are used in digital circuits, since there is large damping for a wavelength less than ⅕ the basic wave, there is little effect from noise radiation from ⅕ wavelengths. 
     FIG. 20 shows the results of measuring the effect of actually using this invention in a trial machine. The size of the battery pack is the same as the one shown in FIG. 15, and the method of installing it in the PC and its construction are the same as those shown in FIG.  14 . FIG. 20A shows the results of measuring noise radiated from a conventional battery pack whose ends are not grounded, with the 3-meter method in an electromagnetic darkroom. Also, FIG. 20B shows the results of measuring noise radiated from a battery pack constructed according to the present invention in which the ends are grounded, with the 3-meter method in an electromagnetic darkroom. From these results it was confirmed that in the case of not using the present invention, the radiated noise was at a peak at approximately 300 MHz near the resonant frequency of the antenna whose wavelength is half the length of the battery pack (resonant frequency is 350 MHz for a battery pack length of 0.2 m and dielectric constant of 4.6), whereas, when constructed using the present invention, there was hardly any radiated noise in the 300 MHz range. From these results, it can be seen that by using the construction of this invention, it is possible to reduce the 15 to 20 dB noise. 
     By making a ground connection ( 531 - 541 ,  532 - 542 ) and connecting the circuit board  510  of the PC  500  with low impedance, standing waves are hardly generated. In addition, by connecting to ground at a position ¼ to ⅕ the length of the battery pack from the end of the battery pack, it is possible to make an antenna with poor radiation efficiency and to reduce the noise. Furthermore, it is possible to reduce noise by changing basic digital signal waves in the high frequency range in which it is easy for radiated noise to occur to higher harmonics with large damping. 
     With this invention, by grounding the battery terminals with a capacitive element, it is possible to provide an information processing device that is capable of being operated by battery, in which the generation of standing waves that occur between the battery terminals is controlled and the radiated noise is reduced.