JP5178942B2 - Information processing device - Google Patents

Description

  The present invention relates to an information processing apparatus including a display unit including a light emitting element as a light source.

  In recent years, portable terminal devices including a display unit such as an LCD (Liquid Crystal Display) including a light emitting element such as an LED (Light Emitting Diode) as a light source have been developed. The light emission efficiency of LEDs is still low, but recently the light emission efficiency has been sufficiently improved.

  Patent Document 1 discloses an illumination device that improves luminance unevenness by alternately arranging LEDs connected to a first power supply control circuit and LEDs connected to a second electrolysis control circuit. Yes.

JP 2001-76525 A

  Although there are many variations in the characteristics of the LEDs, luminance unevenness occurs. However, in order to improve the luminance unevenness, it is conceivable to adjust the luminance by feeding back current. However, in the above-described literature, the cathode side of the LED connected to the first power supply control circuit and the cathode side of the LED connected to the second electrolysis control circuit are connected to ground. When the current is measured, it becomes an average value of the current flowing through the circuit including the LED connected to the first power supply control circuit and the current flowing through the circuit including the LED connected to the first power supply control circuit. It is difficult to provide accurate feedback. Therefore, it has been difficult to improve luminance unevenness of the display unit.

  The objective of this invention is providing the information processing apparatus which can improve the brightness nonuniformity of a display unit.

An information processing apparatus according to an example of the present invention is a display panel that displays an image according to a video signal, a light source that illuminates the display panel, and includes a first light emitting element group, a second light emitting element group, A plurality of light emitting element groups including three or more light emitting element groups, and the first light emitting element group includes a plurality of light emitting diodes including the first light emitting diodes connected in series. The second light emitting element group includes a plurality of light emitting diodes including a second light emitting diode connected in series, and the third light emitting element group is connected in series. And a fourth light emitting diode, a plurality of light emitting elements of the first light emitting element group, a plurality of light emitting elements of the second light emitting element group, and the third light emitting element group the plurality of light emitting elements arranged in one direction, before Symbol first Light emitting diodes and prior Symbol second light emitting diode is located between the front Symbol third light emitting diode and the previous SL fourth light emitting diode, a light source, a luminance signal generating circuit for generating a luminance control signal, wherein A plurality of control circuits provided for a plurality of light emitting element groups, wherein one control circuit includes an anode of a light emitting diode at one end of one light emitting element group and the one light emitting element among the plurality of light emitting element groups. The cathode side of the light emitting diode at the other end of the element group is connected, drives the one light emitting element group, detects a current flowing through a plurality of light emitting diodes connected in series within the one light emitting element group, and based on the control signal and the detected current, the in order to adjust the current flowing through the plurality of series-connected light emitting diodes, subjected to the plurality of series-connected light emitting diodes Adjust the voltage, it is connected to the ground, comprising a plurality of control circuits.

  It becomes possible to improve luminance unevenness of the display unit.

1 is a perspective view showing an appearance of an information processing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating an example of a system configuration of the information processing apparatus in FIG. 1. The block diagram which shows the example of a structure of the LED drive circuit and LED group provided in the information processing apparatus of FIG. The figure which shows the structure of the power supply control circuit of FIG. 3, and white LED. The figure which shows the example of a display of LCD when white LED connected to one of the power supply control circuits stops lighting. The figure which shows the printed circuit board with which white LED was mounted, and a light-guide plate. The figure which shows the printed circuit board with which white LED was mounted, and the interface board connected to the printed circuit board. The block diagram which shows the modification of the system configuration | structure of information processing apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

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

  First, the configuration of an information processing apparatus according to an embodiment of the present invention will be described with reference to FIG. 1 and FIG. This information processing apparatus is realized as a battery-driven portable notebook personal computer 10.

  FIG. 1 is a perspective view of the notebook personal computer 10 with the display unit opened. The computer 10 includes a computer main body 11 and a display unit 12. The display unit 12 incorporates a display panel composed of an LCD 17 (Liquid Crystal Display) and a backlight, and the display screen of the LCD 17 is positioned substantially at the center of the display unit 12. The LCD 17 is composed of a transmissive liquid crystal panel. In the display unit 12, a backlight is disposed on the back surface of the LCD 17. The backlight functions as a lighting device for the display unit 12. This backlight includes a light emitting element such as a white LED (White Light Emitting Diode) as a light source. By using the white LED group as the light source of the backlight, it is possible to realize a long lifetime of the backlight and low power consumption.

  The display unit 12 is supported by the computer main body 11, and is freely attached to the computer main body 11 between an open position where the upper surface of the computer main body 11 is exposed and a closed position covering the upper surface of the computer main body 11. ing. The computer main body 11 has a thin box-shaped casing, and a keyboard 13, a power button 14 for turning on / off the computer 10, an input operation panel 15, a touch pad 16, and the like are arranged on the upper surface thereof. Has been.

  The input operation panel 15 is an input device for inputting an event corresponding to a pressed button, and includes a plurality of buttons for starting a plurality of functions for starting a plurality of functions. These button groups also include a brightness control button 15A.

  The brightness control button 15A is a button switch for adjusting the display brightness of the LCD 17, that is, the brightness of the white LED. When the brightness control button 15A is pressed by the user, an event for instructing either increase (high brightness) or decrease (low brightness) of the brightness of the white LED occurs. The computer 10 has a brightness control function for switching the brightness of the white LED in eight stages of display brightness levels 8 to 1. In this embodiment, every time the brightness control button 15A is pressed by the user, the brightness of the white LED is toggled to display brightness levels 8, → 7, → 6,... → 1, → 8. .

  Next, the system configuration of the computer 10 will be described with reference to FIG.

  As shown in FIG. 2, the computer 10 includes a CPU 111, a north bridge 112, a main memory 113, a graphics controller 114, a south bridge 119, a BIOS-ROM 120, a hard disk drive (HDD) 121, and an optical disk drive (ODD) 122. , An embedded controller / keyboard controller IC (EC / KBC) 124, a power controller 125, and the like.

  The CPU 111 is a processor provided to control the operation of the computer 10 and executes an operating system (OS) and various application programs loaded from the hard disk drive (HDD) 121 to the main memory 113.

  The CPU 111 also executes a BIOS (Basic Input Output System) stored in the BIOS-ROM 120. The BIOS is a program for hardware control. This BIOS has a function of controlling the display brightness of the white LED group. The BIOS uses a brightness control table to control the brightness of the white LED. In the brightness control table, brightness control data corresponding to display brightness levels 8 to 1 is set.

  The north bridge 112 is a bridge device that connects the local bus of the CPU 111 and the south bridge 119. The north bridge 112 is provided with a luminance control register 112A, a PWM (Pulse Width Modulation) circuit 112B, and the like as hardware logic for controlling display luminance. The luminance control register 112 </ b> A is an I / O register that can be read / written by the CPU 111. The BIOS writes the brightness control data corresponding to the target display brightness level in the brightness control register 112A. The PWM circuit 112B generates a PWM signal corresponding to the brightness control data written in the brightness control register 112A. The duty ratio of the PWM signal varies depending on the value of the brightness control data. The PWM signal generated from the PWM circuit 112B is sent to the LED drive circuit 20 provided in the display unit 12 as a luminance control signal.

  The LED drive circuit 20 is a circuit that drives the white LED group 19. The white LED group 19 is attached to one end of a light guide plate 18 provided on the back surface of the LCD 17. The light from the white LED group 19 is irradiated in a planar shape by the light guide plate 18. The light guide plate 18 and the white LED group 19 constitute a backlight. The LED drive circuit 20 has a plurality of power supply control circuits. Each power supply control circuit functions as a boost DC-DC converter. The power supply control circuit adjusts the voltage value of the drive voltage supplied to the white LED group 19 in accordance with the PWM signal sent from the PWM circuit 112B in order to adjust the current value flowing through the white LED group 19.

  The north bridge 112 also includes a memory controller that controls access to the main memory 113. The north bridge 112 also has a function of executing communication with the graphics controller 114 via an AGP (Accelerated Graphics Port) bus or the like.

  The graphics controller 114 is a display controller that controls the LCD 17 used as a display monitor of the computer 10. The graphics controller 114 has a video memory (VRAM) 114A. From the display data written in the video memory 114A by the OS / application program, the graphics controller 114 generates a video signal that forms a display image to be displayed on the LCD 17 of the display unit 12. Generate.

  The south bridge 119 controls each device on an LPC (Low Pin Count) bus. The south bridge 119 incorporates an IDE (Integrated Drive Electronics) controller for controlling the HDD 121 and the ODD 122. Further, the south bridge 119 has a function for controlling access to the BIOS-ROM 120.

  The HDD 121 is a storage device that stores various software and data. The HDD 121 stores the above-described operating system and various application systems.

  An optical disk drive (ODD) 122 is a drive unit for driving a storage medium such as a DVD or a CD in which video content is stored.

  The embedded controller / keyboard controller IC (EC / KBC) 124 is a one-chip microcomputer in which an embedded controller for power management and a keyboard controller for controlling the keyboard (KB) 13 and the touch pad 16 are integrated. . This embedded controller / keyboard controller IC (EC / KBC) 124 is, for example, an SMI (System Management Interrupt) to notify the BIOS that a display brightness switching event has been input when the brightness control button 15A is pressed by the user. An interrupt signal such as The embedded controller / keyboard controller IC (EC / KBC) 124 functions to power on / off the computer 10 according to the operation of the power button 14 by the user by operating in cooperation with the power controller 125. have.

  Next, the configuration of the white LED group 19 and the LED drive circuit 20 will be described with reference to FIGS. The white LED group 19 is configured by mounting a plurality of white LEDs in one direction on a printed board 22 having a plurality of wiring layers. On the printed board 22, a plurality of light emitting areas EA1, EA2, EA3,..., EAn are set in a region where the white LED is mounted. Instead of the printed board 22, a flexible printed board may be used.

  In the first light emitting area EA1, white LEDs dA1 (first light emitting elements), dB1 (second light emitting elements), dC1,..., DD1 are arranged in this order. In the second light emitting area EA2, white LEDs dA2 (third light emitting element), dB2 (fourth light emitting element), dC2,..., DD2 are arranged in this order. White LEDs dA3, dB3, dC3,..., DD3 are arranged in this order in the light emitting area EA3. White LEDs dAn, dBn, dCn,..., DDn are arranged in this order in the light emitting area EAn.

  The white LEDs dA1, dA2, dA3,..., DAn are connected in series. White LEDs dB1, dB2, dB3,..., DBn are connected in series. The white LEDs dC1, dC2, dC3,..., DCn are connected in series. The white LEDs dD1, dD2, dD3,..., DDn are connected in series.

  One end of the white LEDs dA1, dA2, dA3,... DAn connected in series, that is, the anode of the white LED dA1, and the other end, that is, the cathode of the white LED dAn, are connected to the corresponding power control circuit 21A in the LED drive circuit 20. . One end of the white LEDs dB1, dB2, dB3,..., DBn connected in series, that is, the anode of the white LED dB1, and the other end, that is, the cathode of the white LED dBn, are connected to the corresponding power supply control circuit 21B in the LED drive circuit 20. . One end of the white LEDs dC1, dC2, dC3,..., DCn connected in series, that is, the anode of the white LED dC1, and the other end, that is, the cathode of the white LED dCn are connected to the corresponding power control circuit 21C in the LED drive circuit 20. . One end of the white LEDs dD1, dD2, dD3,... DDn connected in series, that is, the anode of the white LED dD1, and the other end, that is, the cathode of the white LED dDn, are connected to the corresponding power control circuit 21D in the LED drive circuit 20. .

  White LEDs in each light emitting area EAi (i = 1, 2, 3,..., N) are arranged in accordance with power supply control circuits 21A, 21B, 21C, and 21D that supply drive voltages.

  The power supply control circuit 21A has a function of detecting a current flowing through the white LEDs dA1, dA2, dA3,. Since the cathode side of the white LEDs dA1, dA2, dA3,..., DAn is not connected to the ground, the power supply control circuit 21A is affected by the current flowing through the white LEDs connected to the other power supply control circuits 21B, 21C, 21D. The current flowing through the white LEDs dA1, dA2, dA3,..., DAn can be accurately detected. The power supply control circuit 21A adjusts the value of the drive voltage VdA based on the duty ratio of the PWM signal input as a luminance control signal to the power supply control circuit 21A and the detected current value.

  The power supply control circuit 21B has a function of detecting a current flowing through the white LEDs dB1, dB2, dB3,. Since the cathode side of the white LEDs dB1, dB2, dB3,..., DBn is not connected to the ground, the power supply control circuit 21B is affected by the current flowing through the white LEDs connected to the other power supply control circuits 21A, 21C, 21D. The current flowing through the white LEDs dB1, dB2, dB3,..., DBn can be accurately detected. The power supply control circuit 21B adjusts the value of the drive voltage VdB based on the duty ratio of the PWM signal input as a luminance control signal to the power supply control circuit 21B and the detected current value.

  The power supply control circuit 21C has a function of detecting the current flowing through the white LEDs dC1, dC2, dC3,..., DCn connected in series. Since the cathode side of the white LEDs dC1, dC2, dC3,..., DCn is not connected to the ground, the power supply control circuit 21C is affected by the current flowing through the white LEDs connected to the other power supply control circuits 21A, 21B, 21D. The current flowing through the white LEDs dC1, dC2, dC3,..., DCn can be accurately detected. The power supply control circuit 21C adjusts the value of the drive voltage VdC based on the duty ratio of the PWM signal input as a luminance control signal to the power supply control circuit 21C and the detected current value.

  The power supply control circuit 21D has a function of detecting a current flowing through the white LEDs dD1, dD2, dD3,..., DDn connected in series. Since the cathode side of the white LEDs dD1, dD2, dD3,..., DDn is not connected to the ground, the power supply control circuit 21D is affected by the current flowing through the white LEDs connected to the other power supply control circuits 21A, 21B, 21C. The current flowing through the white LEDs dD1, dD2, dD3,..., DDn can be accurately detected. The power supply control circuit 21D adjusts the value of the drive voltage VdD based on the duty ratio of the PWM signal input as a luminance control signal to the power supply control circuit 21D and the detected current value. The value of the brightness control signal indicates the value of the PWM signal generated from the PWM circuit 112B.

  As shown in FIG. 3, each white LED in the same light emitting area is controlled by a separate power source drive circuit for the current flowing in the white current. As a result, even if the LED elements vary, luminance unevenness is improved and stable driving can be performed. In addition, since the power supply control circuits 21A, 21B, 21C, and 21D can detect the current flowing through the white LED with high accuracy, the accuracy of feedback due to the detected current can be improved, and luminance unevenness can be improved.

  When a conventional white LED is used as a light source, the white LEDs in the same light emitting area are driven by the same power supply driving circuit. Further, a terminal for supplying a driving voltage to the white LED is often provided at an end portion of the printed board. Therefore, the length of the wiring pattern that connects the terminal and the white LED connected in series differs depending on the light emitting area. However, if the length of the wiring pattern differs due to the resistance of the wiring pattern itself, the drive voltage varies greatly depending on the light emitting area (power supply control circuit). As a result, the luminance between the light emitting areas tends to fluctuate.

  In the present embodiment, each white LED in the light emitting area is driven by a different power control circuit. Therefore, a wiring pattern for connecting white LEDs dA1, dA2, dA3,..., DAn in series, a wiring pattern for connecting white LEDs dB1, dB2, dB3,..., DBn in series, white LEDs dC1, dC2, dC3,. , And the wiring patterns for connecting the white LEDs dD1, dD2, dD3,..., DDn in series are made uniform. Therefore, the drive voltage does not vary greatly according to the (power supply control circuit), and the brightness within the LCD 17 surface becomes uniform.

  Further, when a conventional white LED is used as a light source, the white LEDs in the same light emitting area are driven by the same power supply driving circuit. As a result, when the white LED in any one of the light emitting areas cannot be turned on, a portion where the screen cannot be recognized is generated in a block shape. However, in the case of this embodiment, when it becomes impossible to turn on the white LED connected to any one of the power supply control circuits, a portion that cannot be recognized as a block does not occur as shown in FIG. The information displayed on the LCD 17 can be recognized.

  By the way, when the screen size increases, the number of driving in parallel increases, the voltage needs to be increased, and the wiring pattern connected to the white LED needs to be widened. Since the wiring pattern is wide, the outer shape of the printed circuit board becomes large. FIG. 6 shows a configuration that can enlarge the screen without widening the wiring pattern.

  As shown in FIG. 6, the first printed circuit board 201A on which the white LEDs dA1, dB1, dC1, dD1,..., DAn, dBn, dCn, dDn are mounted on one end of the light guide plate 18, white LEDs dE1, dF1, dG1. , DH1,..., DEn, dFn, dGn, dHn are mounted on the second printed circuit board 201B.

  The first printed circuit board 201A is supplied with the drive voltages output from the power supply control circuits 21A, 21B, 21C, 21D to the white LEDs dA1, dB1, dC1, dD1,..., DAn, dBn, dCn, dDn. One terminal 202A is provided. The second printed circuit board 201B receives drive voltages output from a plurality of power supply control circuits including a third power supply control circuit and a fourth power supply control circuit as white LEDs dE1, dF1, dG1, dH1,..., DEn, dFn, A second terminal 202B for supplying to dGn and dHn is provided. The first terminal 202A and the second terminal 202B are disposed so as to sandwich the light guide plate 18 therebetween. By providing the terminals 202A and 202B for supplying a driving voltage in the left-right direction of the light guide plate 18, it is possible to prevent the wiring pattern from becoming wider and the outer shape from becoming larger.

  Further, the PWM circuit 112 </ b> B and the graphics controller 114 are provided in the computer main body 11. In order to display an image on the LCD 17, it is necessary to supply the display unit 12 with a plurality of signals of the PWM signal from the PWM circuit 112 </ b> B and the video signal from the graphics controller 114. In order to supply signals of a plurality of systems, a plurality of cables are required to supply a plurality of signals in the display unit 12, and an arrangement area for arranging the cables is required. With reference to FIG. 7, the structure which can suppress the arrangement | positioning area of a cable is shown.

  As shown in FIG. 7, the interface substrate 211 is disposed on the back side of the light guide plate 18. The interface board 211 is provided with power control circuits 21A, 21B, 21C, and 21D, a first terminal 212, and a second terminal 213. A first flexible printed circuit board 214 is connected to the first terminal 212. A PWM signal and a video signal supplied from the computer main body 11 are supplied to the first flexible printed circuit board 214.

  A second flexible printed circuit board 215 connected to the printed circuit board 22 is connected to the second terminal 213. Then, the power supply control circuits 21A, 21B, 21C, and 21D adjust the drive voltages VdA, VdB, VdC, and VdD according to the PWM signal supplied to the interface board 211. The drive voltages VdA, VdB, VdC, and VdD are supplied to the printed circuit board 22 by the second flexible printed circuit board 215 that connects the interface circuit board 211 and the printed circuit board 22.

  With this configuration, the PWM signal and the video signal can be supplied from one first terminal 212 by connecting the printed board 22 to the interface board 211. As a result, the drive voltages VdA, VdB, VdC, VdD, and the cable for supplying the video signal are only one first flexible substrate 214, and an increase in the arrangement area can be suppressed.

  In the notebook personal computer 10 described above, the LED drive circuit 20 is disposed in the display unit 12. However, as shown in FIG. 8, an LED drive circuit 20 may be arranged in the computer main body 11.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 10 ... Notebook-type personal computer, 11 ... Computer main body, 12 ... Display unit, 13 ... Keyboard, 14 ... Power button, 15 ... Input operation panel, 15A ... Luminance control button, 16 ... Touch pad, 17 ... LCD, 18 ... Light guide plate, 19 ... LED group, 20 ... LED drive circuit, 21A, 21B, 21C, 21D ... Power supply control circuit, 22 ... Printed circuit board, 111 ... CPU, 112 ... North bridge, 112A ... Brightness control register, 112B ... PWM circuit 113 ... Main memory, 114 ... Graphics controller, 114A ... Video memory, 119 ... South bridge, 120 ... BIOS-ROM, 121 ... Hard disk drive, 122 ... Optical disk drive, 124 ... Keyboard controller IC, 125 ... Power supply controller , DA1, dA2, dA3, ..., dAn ... white LED, dB1, dB2, dB3, ..., dBn ... white LED, dC1, dC2, dC3, ..., dCn ... white LED, dD1, dD2, dD3, ..., dDn ... White LED

Claims (3)

A display panel that displays an image in accordance with a video signal;
A light source for illuminating the display panel has a first light emitting element group, and the second light-emitting element group, three or more of the plurality of light emitting element groups and a third group of light emitting elements, wherein The first light emitting element group includes a plurality of light emitting diodes including a first light emitting diode connected in series, and the second light emitting element group includes a plurality of second light emitting diodes connected in series. The third light emitting element group includes a plurality of light emitting diodes including a third light emitting diode and a fourth light emitting diode, which are connected in series. a plurality of light emitting elements, the second element set of the plurality of light emitting elements, and the plurality of light emitting elements of the third light emitting element group are arranged in one direction, before Symbol first light emitting diode and the pre-Symbol second the light-emitting diodes, front Symbol third light emitting diode before Symbol Located between the 4 light-emitting diodes, a light source,
A luminance signal generating circuit for generating a luminance control signal;
A plurality of control circuits provided for the plurality of light-emitting element groups, wherein one control circuit includes an anode of a light-emitting diode at one end of one light-emitting element group and the one light-emitting element group; The cathode side of the light emitting diode at the other end of the light emitting element group is connected, drives the one light emitting element group, detects the current flowing through the plurality of light emitting diodes connected in series in the one light emitting element group, Based on the brightness control signal and the detected current, in order to adjust the current value flowing through the plurality of light emitting diodes connected in series, adjust the voltage supplied to the plurality of light emitting diodes connected in series, An information processing apparatus comprising a plurality of control circuits connected to ground. A light guide plate provided on the back of the display panel;
A first substrate disposed on one end of the light guide plate, and a second substrate;
The plurality of light emitting element groups further includes a fourth light emitting element group, a fifth light emitting element group, and a sixth light emitting element group,
The first substrate is provided with the first light emitting element group, the second light emitting element group, and the third light emitting element group,
The second substrate is provided with the fourth light emitting element group, the fifth light emitting element group, and the sixth light emitting element group,
The fourth light emitting element group includes a plurality of diodes including a fifth light emitting diode connected in series, and the fifth light emitting element group includes a plurality of sixth light emitting diodes connected in series. The sixth light emitting element group includes a plurality of light emitting diodes including a seventh light emitting diode and an eighth light emitting diode, which are connected in series, and the seventh light emitting diode, A fifth light emitting diode, the sixth light emitting diode, and the eighth light emitting diode are arranged in one direction;
The plurality of control circuits include a first control circuit provided for the first light emitting element group, a second control circuit provided for the second light emitting element group, and the third control circuit. A third control circuit provided for the light emitting element group, a fourth control circuit provided for the fourth light emitting element group, and a fifth control circuit provided for the fifth light emitting element group. A fifth control circuit; and a sixth control circuit provided for the sixth light emitting element group.
The information processing apparatus according to claim 1. Each light emitting element group has the same number of light emitting diodes
The information processing apparatus according to claim 1.

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