Abstract:
An electronic device operable from one of an external power supply and a battery. The electronic device includes a display part, a power converter, an inverter generating an operating voltage for the display part, a system part generating information to be displayed on the display part and operable from an output of the power converter, a battery, an input power detector, and a switching controller. The switching controller controls power to the inverter so that where the input power detector detects availability of an external power, the switching controller supplies the external power to the power converter and the power converter supplies power to the inverter to generate the operating voltage for the display part; and where the input power detector detects the external power is not available, the switching system supplies battery power to the power converter and the inverter independently.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2005-31626, filed Apr. 15, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     An aspect of the present invention relates to an electronic device, and more particularly, to an electronic device wherein a path of power supplied to display is switched according to whether external power is supplied.  
         [0004]     2. Description of the Related Art  
         [0005]     Electronic devices employing batteries are widely used to enable portability and mobility. Such electronic devices include portable computers like laptop computers, notebook computers, personal digital assistants (PDA); mobile phones; CD players; video camcorders; etc. Generally, the electronic devices are provided with a connection terminal for connecting an adapter to use external power through an AC/DC adapter, as well as a battery. A secondary battery which is rechargeable is employed in the electronic devices and is recharged by power from the adapter.  
         [0006]     The electronic devices may be provided with a display panel to display an image thereon, and a liquid crystal display (LCD) panel is widely used as the display panel.  
         [0007]     The LCD panel is a light-receiving display panel unlike a cathode ray tube (CRT) or a plasma display panel (PDP), and includes a lamp to provide light.  
         [0008]      FIG. 1  illustrates an example of a power supply system of a conventional portable computer. As shown in  FIG. 1 , the portable computer includes an adapter  110  and a battery  111  to supply power; a battery charger  112  to charge the battery  111  by using power from the adapter  110 ; an adapter detector  113  to detect whether the adapter  110  is connected; an LCD panel  116 ; a lamp  115  to emit light to the LCD panel  116 ; an inverter  114  to receive power from the adapter  110  or the battery  111  and convert the power into alternating current power for driving the lamp  115 ; and a system power supply  120 a to convert the power from the adapter  110  or the battery  111  into power for driving a system part  117 .  
         [0009]     The power from the adapter  110  or the battery  111  is supplied to the system power supply  120   a  and the inverter  114  according to switching movement of a VDC switch  118  in response to the detection of the adapter detector  113 . The adapter detector  113  and the VDC switch  118  control the power supplied from the adapter  110  to be supplied to the system power supply  120   a  and/or the inverter  114 , prior to the power supplied from the battery  111 .  
         [0010]     The system power supply  120   a  converts the power supplied from the adapter  110  or the battery  111  into power for driving the system part  117  to supply the converted power to each of electronic components of the system part  117 . The system power supply  120   a  includes DC/DC converters  121   a  and  122   a , e.g., a switching voltage regulator, to output power at different voltage levels. An inverter switch  137  is provided to cut off power supplied to the inverter  114 .  
         [0011]     In the power supply system shown in  FIG. 1 , a voltage level of the power input to the inverter  114  ranges from a voltage level of power output from the adapter  110  to a voltage level output by the battery  111 . For example, if the voltage level of output power of the battery  111  is 9V to 11.1 V (for a 3S battery) and the voltage level of the output power of the adapter  110  is 19V, the voltage level of the input power of the inverter  114  ranges from 9V to 19V.  
         [0012]     The inverter  114  is designed to have a breakdown voltage corresponding to 19V to satisfy the input voltage of 9V to 19V and duty fluctuation becomes large, thereby preventing a realization of high efficiency in selecting a MOSFET as a switching element and in designing a high voltage transformer.  
         [0013]      FIG. 2  illustrates another example of a power supply system of another conventional portable computer. Unlike the power supply system of the portable computer shown in  FIG. 1 , the power supply of the portable computer shown in  FIG. 2  supplies the inverter  114  with power from one of DC/DC converters  121   b  and  122   b  of a system power supply  120   b , thereby maintaining a voltage level of power input to the inverter  114 , for example, at 5V.  
         [0014]     However, while the battery  111  supplies power, in the power supply system of the portable computer shown in  FIG. 2 , the power from the battery  111  is input to the inverter  114  through the DC/DC converter  122   b  of the system power supply  120   b  and goes through a power conversion process twice, thereby lowering conversion efficiency of the DC/DC converter  122   b  and the inverter  114  corresponding to load in view of the battery  111 , and thus losing electric power unnecessarily. That is, the conversion efficiency of the DC/DC converter  122   b  and the inverter  114  should be more than 95%, respectively, to maintain the conversion efficiency of the load of more than 90% with respect to the input to the battery  111 . However, it is difficult to realize the DC/DC converter  122   b  and the inverter  114  with more than the 95% conversion efficiency.  
       SUMMARY OF THE INVENTION  
       [0015]     Accordingly, an aspect of the present invention is to provide an electronic device which selectively supplies power output from a system power converter and a battery to a display power converter to realize a narrow input voltage range of input power to the display power converter depending on whether external power is supplied, and increases a usage time of the battery by improving design efficiency of the display power converter.  
         [0016]     The foregoing and/or other aspects of the present invention are achieved by providing an electronic device which receives power from one of an external power supply and a battery outputting first power to drive the electronic device. The electronic device includes a display part; a system power converter to convert the external power supplied from the external power supply into second power at a preset voltage level; a display power converter to convert one of the first power and the second power into power for driving the display part and supply it to the display part; and a power controller to supply the second power from the system power converter as input power of the display power converter if detected that the external power is supplied from the external power supply, and supply the first power from the battery as the input power of the display power converter if the external power is cut off from the external power supply.  
         [0017]     According to an aspect of the present invention, the electronic device may include a system part to display an image through the display part, wherein the system power converter receives the first power if the external power is cut off from the external power supply to convert it into the second power, and the second power output from the system power converter is supplied as power for driving the system part.  
         [0018]     According to an aspect of the present invention, the display part may include a light-receiving display panel to display an image thereon and a lamp to emit light to the display panel to display the image on the display panel, wherein the display power converter comprises an inverter to convert the first power or the second power into alternating current power for driving the lamp, and supply the alternating current power to the lamp.  
         [0019]     According to an aspect of the present invention, the display panel may include a liquid crystal display (LCD) panel.  
         [0020]     According to an aspect of the present invention, the power controller may include a power switch which is switched to supply one of the first power and the second power to the inverter; and a switching controller to control the switch corresponding to the supply of the external power.  
         [0021]     According to an aspect of the present invention, the power switch may include a first switch to control the first power to be supplied to the inverter and a second switch to control the second power to be supplied to the inverter.  
         [0022]     According to an aspect of the present invention, the second switch may include a switching element to control the second power to be supplied to the inverter and a diode which is connected in parallel with the switching element to cut off power from the inverter to the system power converter.  
         [0023]     According to an aspect of the present invention, the second power is included in the range of the voltage level of the first power.  
         [0024]     According to an aspect of the present invention, the first power from the battery which is supplied as the input power of the display power converter does not pass through the system power converter in the state where the supply of the external power is cut off from the external power supply.  
         [0025]     The foregoing and/or other aspects of the present invention are achieved by providing an electronic device which receives power from one of an external power supply and a battery outputting first power. The electronic device includes a display part; a system part to display an image through the display part; a plurality of system power converters to convert one of the external power supplied from the external power supply and the first power into a second power at different voltage levels for driving the system part; a display power converter to convert one of the second power output from one of the plurality of system power converters and the first power into a power for driving the display part, and supply the converted power to the display part; and a power controller to supply the second power from one of the plurality of system power converters as an input power of the display power converter if detected that the external power is supplied from the external power supply, and supply the first power from the battery as the input power of the display power converter if the external power is cut off from the external power supply.  
         [0026]     According to an aspect of the present invention, a voltage level of the second power supplied to the display power converter is close to a voltage level of the first power.  
         [0027]     According to an aspect of the present invention, the power controller may include a power switch which is switched to supply one of the first power and the second power to the inverter; and a switching controller to control the switch corresponding to the supply of the external power.  
         [0028]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0030]      FIGS. 1 and 2  illustrate a power supply system of a conventional electronic device;  
         [0031]      FIG. 3  is a control block diagram of an electronic device according to a first embodiment of the present invention;  
         [0032]      FIG. 4  is a control block diagram of an electronic device according to a second embodiment of the present invention; and  
         [0033]      FIG. 5  illustrates the relation between a voltage level of input power of an inverter and efficiency of the inverter. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0034]     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
         [0035]     An electronic device according to a first embodiment of the present invention receives power from one of an external power supply and a battery to drive the electronic device. That is, the electronic device may receive power from the external power supply or the battery. As shown in  FIG. 3 , the electronic device according to the first embodiment includes display parts  15  (lamp) and  16  (LCD panel), a battery  11 , a system power supply  20   a , and a power controller  30 . The electronic device may also include an external power supply (hereinafter, to be referred to as an adapter) such as an adapter  10 , etc., to supply external power.  
         [0036]     A system part  17  includes a plurality of electronic components to perform major functions of the electronic device. For example, if the electronic device according to an embodiment of the present invention is provided as a portable computer, the system part  17  may include a CPU, a memory such as a RAM, etc., a chipset, a main board and a graphic card. Here, the system part  17  receives power from the system power supply  20   a.    
         [0037]     The battery may be provided as a secondary battery  11  which is rechargeable by a battery charger  12 . For example, a lithium-ion battery or other rechargeable secondary battery may be used.  
         [0038]     Here, the battery  11  includes at least one battery cell with a specification about a voltage level of a first power as a recharging and output power thereof. As an example of the first embodiment according to the present invention, the battery  11  may include three battery cells.  
         [0039]     A maximum voltage level of power output from the respective battery cells is 3.7V, and a cut-off voltage of the respective battery cells is 3V as an example. Accordingly, the voltage level of the first power output from the battery  11  having the three battery cells is 9V to 11.1V.  
         [0040]     The adapter  10  may include an AC/DC adapter to convert commercial alternating current power used at home, etc., into direct current power. Alternatively, the adapter  10  may be a DC/DC adapter to use direct current power such as a cigar jack for vehicles as input power. The electronic device according to the first embodiment of the present invention receives the external power from the adapter  10 , and a voltage level of the external power supplied from the adapter  10  is 19V as an example.  
         [0041]     The system power supply  20   a  converts the external power supplied from the adapter  10  when the adapter  10  is connected or converts a first power supplied from the battery  11  into power at various voltage levels for driving the system part  17 , and supplies the converted power to the system part  17 . For example, if the electronic device is provided as a portable computer, the system power supply  20   a  outputs power at voltage levels, e.g., 5V, 3.3V, 2.5V, etc., for driving the respective electronic components of the system part  17 . The power at various voltage levels which is output from the system power supply  20   a  is used for driving the respective electronic components and transmitting a signal, as necessary.  
         [0042]     The system power supply  20   a  may include a plurality of system power converters, e.g., DC/DC converters  21   a  and  221   a , each including, for example a switching voltage regulator to generate power at a specified voltage level. Hereinafter, the system power converters will be described as the DC/DC converters  21   a  and  221   a  as an example.  
         [0043]     The display parts  15  and  16  may include a light-receiving display panel to display an image thereon; and a lamp  15  to emit light to the display panel  16  to display the image on the display panel  16 . The light-receiving display panel will be described as an LCD panel  16  as an example, as shown in  FIG. 3 . Further, the LCD panel  16  may comprise a light-receiving display panel which displays the image by receiving light from the lamp  15 .  
         [0044]     The display power converter supplies power to the display part  15  and  16 . Here, the display power converter includes an inverter  14  to supply alternating current power for driving the lamp  15 , as an example.  
         [0045]     The inverter  14  receives either the first power from the battery  11  or second power supplied from one (hereinafter, referred to as an inverter DC/DC converter  221   a ) of the plurality of DC/DC converters  21   a  and  221   a  of the system power supply  20   a  to convert the received power into power for driving the lamp  15 , and supplies the converted power to the lamp  15 .  
         [0046]     The inverter DC/DC converter  221   a  converts the external power from the adapter  10  or the first power from the battery  11  into the second power at a preset voltage level to supply the converted power to the inverter  14 .  
         [0047]     If the external power is supplied, the power controller  30  controls the second power output from the inverter DC/DC converter  221   a  to be supplied to the inverter  14 . If the power from the adapter  10  is cut off, for example, if a user disconnects the adapter  10  or a usage power connected with the adapter  10 , the power controller  30  controls the first power output from the battery  11  to be supplied to the inverter  14 . Accordingly, if the external power is input from the adapter  10 , the external power is converted into the second power by the inverter DC/DC converter  221   a  to be supplied to the lamp  15  for driving the lamp  15 . If the external power is not input, the first power output from the battery  11  is directly applied to the inverter  14 , thereby reducing power loss by unnecessary conversion by the inverter DC/DC converter  221   a  and increasing usage time of the battery  11 .  
         [0048]     The electronic device shown in  FIG. 3  may comprise an adapter detector  13  to detect whether the external power is supplied from the adapter  10 . The power controller  30  may determine the supply of the external power corresponding to the detection of the adapter detector  13 . The power controller  30  a may comprise a power switch  31  and a switching controller  38 .  
         [0049]     The power switch  31  switches one of the first power output from the battery  11  and the second power output from the inverter DC/DC converter  221   a  to the inverter  14 , according to the control of the switching controller  38 .  
         [0050]     The power switch  31  may include a first switch  34  to control the first power output from the battery  11  to be supplied to the inverter  14 ; and a second switch  37  to control the second power output from the inverter DC/DC converter  221   a  to be supplied to the inverter  14 . That is, the inverter  14  is supplied from the DC/DC converter  221   a  or directly from the battery  11 .  
         [0051]     The first switch  34  may include a first switching element  32  which is switched according to the control of the switching controller  38  to control the connection between the battery  11  and the inverter  14 ; and a first diode  33  which is connected in parallel with the first switching element  32 . Here, a cathode of the first diode  33  is connected to the battery  11  and an anode of the first diode  33  is connected to the inverter  14 . Accordingly, if the voltage level of the first power output from the battery  11  is larger than a voltage level of the second power output from the inverter DC/DC converter  221   a , the first power from the battery  11  may be prevented from being supplied to the inverter  14  when the first switch  34  is turned off.  
         [0052]     The second switch  37  may include a second switching element  35  which is switched according to the control of the switching controller  38  to control the connection between the inverter DC/DC converter  221   a  and the inverter  14 ; and a second diode  36  which is connected in parallel with the second switching element  35 . An anode of the second diode  36  is connected to the inverter DC/DC converter  221   a  and a cathode thereof is connected to the inverter  14 . Accordingly, when the first switching element  32  is turned on and the second switching element  35  is turned off by the control of the switching controller  38  to supply the first power from the battery  11  to the inverter  14 , the first power at the larger voltage level than the second power is prevented from flowing to the inverter DC/DC converter  221   a.    
         [0053]     The switching controller  38  turns on and off the first switching element  32  and/or the second switching element  35  according to the detection of the adapter detector  13 . That is, the switching controller  38  turns off the first switching element  32  and turns on the second switching element  35  if the adapter detector  13  detects that the external power is supplied from the adapter  10 .  
         [0054]     Meanwhile, the switching controller  38  turns off the second switching element  35  and turns on the first switching element  32  if the adapter detector  13  detects that the external power is not supplied from the adapter  10 .  
         [0055]     The voltage level of the second power output from the inverter DC/DC converter  221   a  may be close to the voltage level of the first power output from the battery  11 . As described above, if the voltage levels of the power output from the respective DC/DC converters  21  a and  221   a  of the system power supply  20   a  are +5V, +3.3V and +2.5V and the voltage level of the first power output from the battery  11  is in the range of 9V to 11.1V, the DC/DC converter  22   a  outputting a power of 5V among the DC/DC converters  21   a  and  221   a  of the system power supply  20   a  may be used as the inverter DC/DC converter  22   a . Also, if one of the DC/DC converters  21   a  and  22   a  of the system power supply  20   a  outputs power at the voltage level included in the range of 9V to 11.1V which is the same as the voltage level of the first power output from the battery  11 , the corresponding DC/DC converters  21   a  and  22   a  may be used as the inverter DC/DC converter  22   a . Then, the voltage level of the input power to the inverter  14  (INV_VDC) becomes 9V to 11.1V, thereby reducing a design margin of the inverter  14 . That is, a narrow INV_VCD may be realized with respect to an input of the inverter  14 , so that the inverter  14  can use a low breakdown voltage by the realization of the narrow INV_VDC, thereby reducing switching loss and conduction loss and ultimately increasing usage time of the battery  11 . Thus, the voltage output from the DC/DC converter  22   a  may be within about 20% of the voltage output by the battery  11 .  
         [0056]      FIG. 5  illustrates the relation between the voltage level of the input power of the inverter  14  and efficiency of the inverter  14 . As shown in  FIG. 5 , the lower the voltage level of the input power and the narrower the fluctuation of the voltage level of the input power is, the higher the efficiency of the inverter  14  is. Accordingly, if the narrow INV_VDC is realized with respect to the input of the inverter  14 , the battery  11  is used longer due to efficiency improvement of the inverter  14 . Cases  1 - 4 , as shown, represent results of testing four samples subjected to a same testing condition.  
         [0057]     In the embodiment shown in  FIG. 3 , a VDC switch  18  makes one of the external power from the adapter  10  and the first power from the battery  11  to be supplied to the system power supply  20   a  and/or the DC/DC converters  21   a  and  22   a . That is, the switch  18  supplies the external power from the adaptor  10  or the first power from the battery  11  to the system power supply  20   a  and/or the DC/DC converters  21   a  and  22   a . The VDC switch  18  may switch according to the control of the switching controller  38 . The switching controller  38  controls the VDC switch  18  to supply the external power from the adapter  10  to the system power supply  20   a  and/or the DC/DC converters  21   a  and  22   a , prior to the power from the battery  11 .  
         [0058]     An electronic device according to a second embodiment of the present invention will be described with reference to  FIG. 4 .  
         [0059]     The electronic device shown in  FIG. 4  includes a display power converter, for example, a DC/DC converter  22   b , which converts external power from an adapter  10  into second power at a preset voltage level to supply it to an inverter  14 , and a system power supply  20   b . As shown in  FIG. 4 , the DC/DC converter  22   b  receives first power outputted from a battery  11  when power from the adapter  10  is cut off. Even if a user disconnects the adapter  10  while using the electronic device in the state that the electronic device is connected with the adapter  10 , the inverter  14  is continuously supplied with power by the first power outputted from the battery  11  until the power inputted to the inverter  14  is converted from the second power to the first power according to a switching movement of a power switch  31  of a power controller  30 .  
         [0060]     Like in the first embodiment shown in  FIG. 3 , the power controller  30  controls the second power output from the DC/DC converter  22   b  to be supplied to the inverter  14  if the supply of the external power is detected. Conversely, if the supply of the external power is not detected, the power controller  30  controls the first power output from the battery  11  to be supplied to the inverter  14 .  
         [0061]     A voltage level of the second power output from the DC/DC converter  22   b  according to the second embodiment of the present invention may be close to a voltage level of the first power output from the battery  11 . The voltage level of the second power output from the DC/DC converter  22   b  may be included in the range of the voltage level of the first power output from the battery  11 . As described above and as can be seen from  FIG. 5 , if the voltage level of the first power output from the battery  11  is in the range of 9V to 11.1V, the voltage level of the second power output from the DC/DC converter  22   b  may be included in the range of 9V to 11.1V, for example, 10V. Then, the voltage level of the input power to the inverter  14  becomes 9V to 11.1V, thereby reducing a design margin of the inverter  14 . That is, a narrow INV_VDC may be realized with respect to an input of the inverter  14 , thereby reducing switching loss and ultimately increasing usage time of the battery  11  due to the realization of the narrow INV_VDC.  
         [0062]     Where electronic components of the system part  17  include an electronic component which uses a power corresponding to the voltage level of the second power, the second power output from the DC/DC converter  22   b  may also supply power to the corresponding electronic component.  
         [0063]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.