1. Field of the Invention
The present invention relates to a flat panel display, and more particularly, to a method for routing gamma voltages.
2. Description of the Related Art
A camera converts an image signal into an electrical signal, and a display restores the electrical signal converted by the camera to the original image signal. The display needs correction such that the electrical signal is restored close to the original image signal.
The human eyes have a response characteristic in a log curve shape with respect to incident light, in order to receive brightness of light in a wide range. However, an image sensor mounted in a camera may receive brightness of in a limited dynamic range. A complementary metal oxide semiconductor (CMOS) image sensor may be designed to increase a gain, in order to clearly represent a dark portion. In this case, a saturation phenomenon may occur in some bright portions.
Gamma correction means a function of changing brightness or luminance and is used to correct the nonlinearity of photoelectric conversion characteristics of an image device and the saturation phenomenon of light. A mathematical expression applied to the gamma correction may be represented by a curve, and the curve is called a gamma curve. When a gamma value is set to a high value, a center portion of the gamma curve is lifted, so that the screen becomes brighter. When the gamma value is set to a low value, the center portion of the gamma curve is lowered, so that the screen becomes darker.
The flat panel display may include liquid crystal displays (LCDs) or plasma display panels (PDPs). Recently, flat panel displays using organic light emitting devices (OLEDs) have been developed.
In general, the flat panel display includes six to eight source driver integrated circuits (SDICs). Each of the SDICs includes two gamma buffers configured to buffer gamma voltages.
The gamma buffers may be arranged in a predetermined order during design, according to the levels of gamma voltages or gray levels. The voltages output from the respective gamma buffers are transmitted to a resistor string. The resistor string includes 255 resistors connected in series, for example, and voltages dropped by the respective resistors exhibit characteristics of the gamma curve.
In this case, due to the voltages buffered by the gamma buffers and the resistances of the resistors connected to the gamma buffers so as to operate as loads, power consumptions of the gamma buffers may differ from each other. Since the power consumptions of the gamma buffers are not equal, the heating values or temperatures of the gamma buffers may also differ from each other.
Referring to
Furthermore, each of the SDICs IC#1 to IC#6 includes two gamma buffers. That is,
A center PCB (C-PCB) 110 provides a routing path between the S-PCBs 120 and 130.
Here, VL represents a voltage from the lowest voltage of a gamma voltage to a medium voltage of the gamma voltage, and VH represents a voltage from the medium voltage of the gamma voltage to the highest voltage of the gamma voltage. When the gamma voltage is 12V, VL represents a voltage of 0V to 5.9V, and VH represents a voltage of 6.1V to 12V. For example, VL255 represents 0V, and VL00 represents a voltage 5.9V. Furthermore, VH00 represents 6.1V, and VH255 represents 12V.
Due to the differences in power consumption among the gamma buffers included in the respective SDICs IC#1 to IC#6 as illustrated in
The lifetime and reliability of the flat panel display are decided by the lifetimes and reliabilities of the respective SDICs. When the temperature of a specific SDIC among six or eight SDICs is higher than the other SDICs, the lifetime and reliability of the high-temperature SDIC are inevitably decreased, compared to those of the other SDICs. When a defect occurs in any one of SDICs mounted in a flat panel display, the flat panel display does not operate.
Therefore, in order to improve the lifetime and reliability of the flat panel display, the lifetime and reliability of a specific SDIC must be prevented from being reduced and degraded in comparison with those of the other SDICs.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a method for routing gamma voltages, which is capable of reducing temperatures of source driver integrated circuits (SDIC) mounted in a flat panel display and reducing temperature differences among the SDIC.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for routing gamma voltages in a flat panel display that includes a plurality of SDICs each having a plurality of gamma buffers. The method includes: forming routing lines to route a plurality of gamma voltages; connecting the routing lines to output terminals of the gamma buffers; applying the reset gamma voltage to the gamma buffer of a selected SDIC after selecting the SDIC in which the gamma voltage is required to be reset in consideration of heating values of the SDICs; and changing connection between a routing line corresponding to the selected gamma buffer and a tap point of a resistor string of the SDIC such that the connection corresponds to the reset gamma voltage.
According to another aspect of the present invention, there is provided a method for routing gamma voltages in a flat panel display that includes a plurality of SDICs each having a plurality of gamma buffers. The method includes: forming routing lines to route a plurality of gamma voltages; and, exchanging positions to which a pair of selected gamma voltages are applied and transmitting the pair of selected gamma voltages to the routing lines at the exchanged positions after selecting the pair of gamma voltages to be applied to different SDICs in consideration of heating values of the gamma buffers.
According to another aspect of the present invention, there is provided a method for routing gamma voltages in a flat panel display that includes a plurality of SDICs each having a plurality of gamma buffers. The method includes: mounting one or more external gamma buffers outside the plurality of SDICs; forming routing lines to route a plurality of gamma voltages; changing input of the gamma voltage for a selected gamma buffer and connection between the selected gamma buffer and the routing line to the external gamma buffers after selecting one or more the gamma buffers in consideration of heating values of the gamma buffers; and floating the selected gamma buffers.
The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description taken in conjunction with the drawings, in which:
Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.
A flat panel display 100 includes a center printed circuit board (C-PCB) 110 and two source PCBs (S-PCB) 120 and 130.
The C-PCB 110 includes parts for controlling operations performed by the two S-PCBs 120 and 130, and provides a routing path between the S-PCBs 120 and 130. The C-PCB 110 may be electrically connected to the two S-PCBs 120 and 130 through conductive films.
The S-PCB 120 includes three SDICs IC#1 to IC#3.
The SDIC IC#1 includes a gamma buffer GB11 configured to buffer a gamma voltage VH255, a gamma buffer GB12 configured to buffer a gamma voltage VL255, and a resistor string R-ST. The SDIC IC#2 also includes a gamma buffer GB21 configured to buffer a gamma voltage VH223, a gamma buffer GB22 configured to buffer a gamma voltage VL223, and a resistor string R-ST. The SDIC IC#3 includes a gamma buffer GB31 configured to buffer a gamma voltage VH191, a gamma buffer GB32 configured to buffer a gamma voltage VH191, and a resistor string R-ST. The S-PCB 120 includes three SDICs IC#1 to IC#3.
The S-PCB 130 includes three SDICs IC#4 to IC6.
The SDIC IC#4 includes a gamma buffer GB41 configured to buffer a gamma voltage VH127, a gamma buffer GB42 configured to buffer a gamma voltage VL127, and a resistor string R-ST. The SDIC IC#5 also includes a gamma buffer GB51 configured to buffer a gamma voltage VH31, a gamma buffer GB52 configured to buffer a gamma voltage VL31, and a resistor string R-ST. The SDIC IC#6 includes a gamma buffer GB61 configured to buffer a gamma voltage VH00, a gamma buffer GB62 configured to buffer a gamma voltage VH00, and a resistor string R-ST.
In the embodiment of the present invention based on
The gamma buffer GB11 has a power consumption of 10.3 mW in response to the gamma voltage VH255, the gamma buffer GB12 has a power consumption of 1.5 mW in response to the gamma voltage VL255, and the sum of the power consumptions is 11.8 mW. The heating value or temperature of the SDIC IC#1 including the gamma buffers GB11 and GB12 is 50.3° C. The temperature of the gamma buffer GB11 is almost equal to the temperature of the gamma buffer GB11 described with reference to
The gamma buffer GB21 has a power consumption of 14.3 mV in response to the gamma voltage VH223, the gamma buffer GB22 has a power consumption of 12.3 mW in response to the gamma voltage VL223, and the sum of the power consumptions is 26.6 mW. The temperature of the SDIC IC#2 including the gamma buffers GB21 and GB22 is 51.3° C.
The temperature of the SDIC IC#2 according to the embodiment of the present invention based on
Furthermore, the SDIC IC#2 according to the embodiment of the present invention based on
That is, the gamma voltages applied to the gamma buffers GB21 and GB22 the SDIC IC#2 according to the embodiment of the present invention based on
In the embodiment of the present invention based on
Therefore, according to the embodiment of the present invention based on
Meanwhile, the gamma voltages routed to the respective SDIC s IC#1 to IC#6 through routing lines RL are applied to the resistor strings R-ST of the respective SDIC s IC#1 to IC#6.
The resistances of the resistor strings R-ST to operate as loads for the respective gamma voltages are varied, and the power consumptions of the gamma buffers are changed depending on the resistances of the resistor strings R-ST operating as loads of the gamma voltages.
Therefore, according to the embodiment of the present invention based on
Furthermore, the embodiment of
That is, in order to reduce the heating value of a gamma buffer whose gamma voltage was changed, a load needs to be controlled. For this operation, the tap point change is required as illustrated in
More specifically, referring to
Meanwhile, the present invention may be embodied as illustrated in
That is, in the embodiment of
Accordingly, the gamma buffer GB12 buffers the gamma voltage VL00 and provides the buffered voltage to the respective SDICs through the routing lines RL, and the gamma buffer GB62 buffers the gamma voltage VL255 and provides the buffered voltage to the respective SDICs through the routing lines RL.
In the embodiment of
Therefore, in the embodiment of
In the embodiment of
Furthermore, according to the embodiment of
Meanwhile, the present invention may be embodied as illustrated in
Referring to
The external gamma buffers GBE1 and GBE2 are configured to receive the gamma voltage VH00 and VH00 through input terminals thereof.
According to the embodiment of the present invention, a gamma buffer having a high heating value or gamma buffers included in an SDIC having a high heating value are selected and floated, and input of a gamma voltage for the selected gamma buffer and connection between the selected gamma buffer and a routing line RL are changed to the external gamma buffers GBE1 and GBE2.
The present invention may be applied to one gamma buffer having a high heating value or two or more gamma buffers having a high heating value, which are included in different SDIC s, unlike the embodiment of
Furthermore, the number of external gamma buffers may be set to the same number as the number of gamma buffers to change routing.
Furthermore, when necessary, the gamma buffers to change routing may be selected in order of heating value, by the same number as the number of external gamma buffers.
The external gamma buffers may be mounted on the same PCB as the SDIC in which the selected gamma buffer is mounted.
According to the configuration of
Referring to
So far, the flat panel display according to the embodiments of the present invention has been described with reference to the accompanying drawings. A method for routing gamma voltages may also be described by referring to the detailed descriptions with reference to the accompanying drawings.
According to the embodiments of the present invention, the temperatures of the SDICs mounted in the flat panel display may be reduced, and the temperature differences among the SDICs maybe minimized to improve the lifetime and reliability of the flat panel display.
Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and the spirit of the invention as disclosed in the accompanying claims.
This is a continuation-in-part of U.S. patent application Ser. No. 12/594,794, filed Oct. 5, 2009, which is a national entry of International Application No. PCT/KR2008/001672, filed on Mar. 26, 2008, which claims priority to Korean Application No. 10-2007-0036721 filed on Apr. 16, 2007, the entire contents of which are incorporated herein by reference.
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Number | Date | Country | |
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Number | Date | Country | |
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Parent | 12594794 | US | |
Child | 13798216 | US |