Organic light-emitting display device

An organic light-emitting display device that increases long range uniformity (LRU). The organic light-emitting display device includes an image display unit including a plurality of pixels defined by a plurality of scan lines and a plurality of data lines, a plurality of film type connection devices electrically connected to the image display unit and at least one DC-DC converter arranged on the plurality of film type connection devices to supply driving voltages to the image display unit.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for ORGANIC LIGHT-EMITTING DISPLAY DEVICE earlier filed in the Korean Intellectual Property Office on Apr. 30, 2010 and there duly assigned Serial No. 10-2010-0040809.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic light-emitting display device.

2. Description of the Related Art

A variety of flat panel displays (FPDs), such as liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), organic light-emitting displays, or the like, have been developed to reduce the weight and volume of cathode ray-tube (CRT) display devices. Among these flat panel display devices, the organic light-emitting display device displays an image using an organic light-emitting diode (OLED) which generates light through a recombination of electrons and holes. The organic light-emitting display device has a wide range of applications, such as PDAs, MP3 players, cellular phones, digital cameras, etc., owing to various advantages thereof such as excellent coloring and thinness.

SUMMARY OF THE INVENTION

The present invention provides an organic light-emitting display device for increasing long range uniformity (LRU).

According to an aspect of the present invention, there is provided an organic light-emitting display device that includes an image display unit including a plurality of pixels defined by a plurality of scan lines and a plurality of data lines, a plurality of film type connection devices electrically connected to the image display unit and at least one DC-DC converter arranged on the plurality of film type connection devices to supply driving voltages to the image display unit.

The at least one DC-DC converter may supply a first power voltage and a second power voltage to the image display unit. The at least one DC-DC converter may be electrically connected to a power generation unit, the at least one DC-DC converter may raise or invert a voltage input from the power generation unit and to generate the first power voltage and the second power voltage. The at least one DC-DC converter may be mounted on the plurality of film type connection devices to correspond to a center of the image display unit. The at least one DC-DC converter may be mounted on the plurality of film type connection devices to correspond to an edge of the image display unit. The at least one DC-DC converter includes a plurality of DC-DC converters, and each of the plurality of DC-DC converters performs a phase control operation by supplying identical voltages and identical currents to the image display unit, respectively. The at least one DC-DC converter may control the first power voltage and the second power voltage that are supplied to the image display unit and to maintain static voltages. The plurality of film type connection devices may be one of flexible printed circuit boards (FPCBs) and tape carrier packages (TCPs). The image display unit may be included in a large size display panel of greater than 40 inches. The at least one DC-DC converter may include a first, a second, a third and a fourth DC-DC converter, the plurality of film type connection devices comprises a first and a second film type connection devices. An output voltage waveform of the second DC-DC converter may be phase delayed by 90 degrees compared to an output voltage waveform of the first DC-DC converter.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described more fully with reference to the accompanying drawings. The detailed description and the drawings are introduced to provide understanding of the present invention and the detailed descriptions of well-known technologies may be omitted. In addition, the specification and the drawing are not provided to limit the scope of the present invention and the scope of the present invention is defined by the claims. The terminologies used herein are for the purpose of describing embodiments well and thus may be interpreted to correspond to the meaning and concept of the present invention.

Although an organic light-emitting display device is exemplified in the embodiments of the present invention, the present invention is not limited thereto. That is, the technical idea of the present invention can be applied to a variety of flat panel display devices.

Turning now toFIG. 1,FIG. 1is a circuit diagram of a pixel circuit101employed in an organic light-emitting display device. Referring toFIG. 1, the pixel circuit101includes a first transistor M1, a second transistor M2, a capacitor Cst, and an organic light-emitting diode (OLED).

A source terminal of the first transistor M1is connected to a first power voltage ELVDD, a drain terminal thereof is connected to an anode of the OLED, and a gate terminal thereof is connected to a first node N1. A source terminal of the second transistor M2is connected to a data line Dm, a drain terminal thereof is connected to the first node N1, and a gate terminal thereof is connected to a scan line Sn. A first terminal of the capacitor Cst is connected to the first power voltage ELVDD, and a second terminal thereof is connected to the first node N1. The OLED includes the anode terminal, a cathode terminal, and an emission layer. The anode terminal of the OLED is connected to the drain terminal of the first transistor M1, and the cathode terminal thereof is connected to a second power voltage ELVSS. If a current flows from the anode terminal of the OLED to the cathode terminal thereof, the emission layer thereof emits light according to the amount of the current. Equation 1 indicates the current that flows in the drain terminal of the first transistor M1.

Id=β2⁢(ELVDD-Vdata-Vth)2[Equation⁢⁢1]
wherein, Id denotes the current that flows in the drain terminal of the first transistor M1, Vdata denotes a voltage of a data signal, ELVDD denotes the first power voltage applied to the source terminal of the first transistor M1, Vth denotes a threshold voltage of the first transistor M1, and β denotes a constant.

Turning now toFIG. 2,FIG. 2is a plan view of an organic light-emitting display device according to an embodiment of the present invention. Referring toFIG. 2, the organic light-emitting display device includes an image display unit100, a data driving unit200, a scan driving unit300, and a DC-DC converter400.

A plurality of pixels101as illustrated inFIG. 1are arranged in the image display unit100and each includes an OLED that emits light according to the current flow. The image display unit100includes n scan lines S1, S2, Sn-1, and Sn that are arranged in a row direction and transmit scan signals, and m data lines D1, D2, Dm-1, and Dm that are arranged in a column direction and transmit data signals. The image pixel unit100is driven by receiving the first power voltage ELVDD and the second power voltage ELVSS from the outside. Therefore, the image display unit100emits light via the OLEDs to display an image according to the scan signals, the data signals, the first power voltage ELVDD, and the second power voltage ELVSS. In the present embodiment, the image pixel unit100is large in size and is included in a large-size display panel.

The data driving unit200receives video data having red, blue, and green components, generates the data signals and applies the data signals to the image display unit100. The data driving unit200is connected to the m data lines D1, D2, Dm-1, and Dm of the image pixel unit100to apply the generated data signals to the image display unit100.

The scan driving unit300applies scan signals to the image display unit100and is connected to the n scan lines S1, S2, Sn-1, and Sn that transmits the scan signals to a specific row of the image display unit100. The pixels101that have received the scan signals also receive the data signals from the data driving unit200, generate a driving current Id, and allow the driving current Id to flow through the OLEDs.

The DC-DC converter400receives a voltage from a power generation unit500, changes a level of the received voltage, generates the first power voltage ELVDD and the second power voltage ELVSS suitable for the image display unit100, and transmits the generated first power voltage ELVDD and second power voltage ELVSS to the image display unit100. The DC-DC converter400includes a regulator as well as a boost circuit for generating the first power voltage ELVDD and an inverter for generating the second power voltage ELVSS.

Turning now toFIG. 3,FIG. 3is a schematic diagram of a structure of a front surface of an organic light-emitting display device according to an embodiment of the present invention. Referring toFIG. 3, the data driving unit200that supplies data signals to the image display unit100is arranged on the lower surface of the image display unit100as a chip on panel (COP), however, the present invention is not limited thereto. The data driving unit200may be arranged outside the panel (not shown) and be connected to the panel through a film type connection device. In this regard, the panel includes the image display unit100corresponding to a display region and a non-display region surrounding the display region.

The scan driving unit300is arranged on a side surface of the image display unit100as a COP, however, the present invention is not limited thereto. The scan driving unit300may be formed outside a panel and connected to the panel through the film type connection device. The image display unit100receives the data signals and the scan signals from the data driving unit200and the scan driving unit300, respectively.

The power generation unit500is arranged outside the panel, generates a voltage, and transmits the generated voltage to a DC-DC converter (not shown) via a source printed circuit board (PCB)510through the film type connection device600.

Turning now toFIG. 4,FIG. 4is a schematic diagram of a structure of a rear surface of the organic light-emitting display device ofFIG. 3according to a first embodiment of the present invention. Referring toFIG. 4, the film type connection device600is electrically connected to the source PCB510and the image display unit100. The film type connection device600may be a flexible printed circuit board (FPCB) or a tape carrier package (TCP). The shape and number of the film type connection device600as shown inFIG. 4are not limited thereto and may be realized in various ways.

The DC-DC converter400is mounted on the film type connection device600. The DC-DC converter400changes the level voltage of the voltage received from the power generation unit500and generates the first power voltage ELVDD and the second power voltage ELVSS suitable for the image display unit100. The DC-DC converter400transmits the generated first power voltage ELVDD and second power voltage ELVSS to the image display unit100. The first power voltage ELVDD and the second power voltage ELVSS are supplied to the pixels101as driving voltages to cause the OLEDs to emit light.

A typical DC-DC converter is disposed outside a panel. Thus, a driving voltage generated by a typical DC-DC converter is applied to an image display unit via a source PCB through a film type connection device. In this regard, a long distance between the DC-DC converter and the image display unit causes the occurrence of a large IR voltage drop. The larger the image display unit, the greater the IR drop. According to an experiment, a voltage applied to an image display unit of about 40 inches is measured to be smaller than a voltage supplied by the DC-DC converter by 2V. This adversely affects long range uniformity (LRU) of the organic light-emitting display device.

However, referring toFIGS. 3 and 4, the DC-DC converter400arranged so that it is closer to the image display unit100so that the first power voltage ELVDD and the second power voltage ELVSS are supplied to the image display unit100through the film type connection device600. A short distance between the DC-DC converter400and the image display unit100reduces the occurrence of the IR drop. Thus, the LRU of the organic light-emitting display device is improved.

The organic light-emitting display device of the first embodiment may include a plurality of film type connection devices600and a plurality of DC-DC converters400mounted on the film type connection devices600. Referring toFIG. 4, the organic light-emitting display device of the first embodiment may include a first film type connection device610, a second film type connection device620, a first DC-DC converter410, and a second DC-DC converter420, however the present invention is not limited thereto as a single DC-DC converter may be mounted on a single film type connection device and still be within the scope of the present invention.

The first DC-DC converter410is mounted on the first film type connection device610corresponding to the center of the image display unit100as shown inFIG. 4. The second DC-DC converter420is mounted on the second film type connection device620also corresponding to the center of the image display unit100. The first power voltage ELVDD and the second power voltage ELVSS that are output from the first and second DC-DC converters410and420are supplied to the image display unit100. In the present embodiment, since the DC-DC converter400is disposed to correspond to the center of the image display unit100, the distance between the DC-DC converter400and the image display unit100does not vary much between pixels, thereby applying the driving voltage output from the DC-DC converter400to the image display unit100uniformly.

The first and second DC-DC converters410and420control the first power voltage ELVDD and the second power voltage ELVSS supplied to the image display unit100to maintain static voltages. Maintenance of static voltages may be achieved in various ways. For example, the first DC-DC converter410feed backs the first power voltage ELVDD output from the first DC-DC converter410and detects and controls an output voltage. Further, the first and second DC-DC converters410and420perform a phase control operation to supply a voltage and current of the same size to the image display unit100, respectively.

Turning now toFIG. 5,FIG. 5is a timing diagram of a phase control operation performed by the first and second DC-DC converters410and420according to the first embodiment of the present invention. Referring toFIG. 5, it is assumed that the first and second DC-DC converters410and420supply a voltage of 10 V to the image display unit100. During the phase control operation, the first DC-DC converter410outputs a voltage of 5V during a first driving period T1, and the second DC-DC converter420outputs a voltage of 0V during the first driving period T1. If the second DC-DC converter420outputs a voltage of 5V during a second driving period T2, the first DC-DC converter410outputs a voltage of 0V during the second driving period T2. In more detail, an output voltage waveform of the second DC-DC converter420is phase-delayed by 180 degrees as compared to an output voltage waveform of the first DC-DC converter410. The phase control operation is to phase-delay output voltage waveforms of the plurality of DC-DC converters400and output voltages thereof according to Equation 2 below. Since the first and second driving periods T1and T2are merely several microseconds (μs) in duration, a voltage of 10V is supplied to the image display unit100. As described above, the plurality of DC-DC converters400may uniformly distribute the load of the image display unit100through phase control.

Turning now toFIG. 6,FIG. 6is a schematic diagram of a structure of a rear surface of the organic light-emitting display device ofFIG. 3according to a second embodiment of the present invention. Referring toFIG. 6, the organic light-emitting display device of the second embodiment may include a first film type connection device610, a second film type connection device620, a first DC-DC converter410, a second DC-DC converter420, a third DC-DC converter430, and a fourth DC-DC converter440. A plurality of DC-DC converters may be mounted on a single film type connection device.

The first DC-DC converter410and the third DC-DC converter430are mounted on the first film type connection device610corresponding to an edge of the image display unit100. The second DC-DC converter420and the fourth DC-DC converter440are mounted on the second film type connection device620corresponding to the edge of the image display unit100. The first power voltage ELVDD and the second power voltage ELVSS that are output from the first through fourth DC-DC converters410,420,430, and440are supplied to the image display unit100. In the present embodiment, since the first through fourth DC-DC converters410,420,430, and440are disposed to correspond to the edge of the image display unit100, the distance between the first through fourth DC-DC converters410,420,430, and440and the image display unit100is very short, thereby reducing the IR drop.

The first through fourth DC-DC converters410,420,430, and440control the first power voltage ELVDD and the second power voltage ELVSS supplied to the image display unit100and maintain static voltages. Maintenance of static voltages is achieved in various ways and a detailed description thereof is not repeated here. The first through fourth DC-DC converters410,420,430, and440also perform a phase control operation to supply a voltage and a current of the same size to the image display unit100, respectively.

Turning now toFIG. 7,FIG. 7is a timing diagram of a phase control operation performed by first through fourth DC-DC converters according to the second embodiment of the present invention. Referring toFIG. 7, it is assumed that the first through fourth DC-DC converters410,420,430, and440supply a voltage of 10 V to the image display unit100. During the phase control operation, the first through fourth DC-DC converters410,420,430, and440each output a voltage of 2.5V, respectively. An output voltage waveform of the second DC-DC converter420is phase-delayed by 90 degrees as compared to an output voltage waveform of the first DC-DC converter410. An output voltage waveform of the third DC-DC converter430is phase-delayed by 180 degrees as compared to the output voltage waveform of the first DC-DC converter410. An output voltage waveform of the fourth DC-DC converter440is phase-delayed by 270 degrees as compared to the output voltage waveform of the first DC-DC converter410. As described above, the first through fourth DC-DC converters410,420,430, and440may uniformly distribute the load to the image display unit100through phase control.

The number of DC-DC converters, the locations where the DC-DC converters are mounted, the number of film type connection devices, and the shapes and sizes of the film type connection devices shown inFIGS. 4 through 6are not limited thereto. As long as the DC-DC converters, which are the core of the present invention, are mounted on the film type connection devices and supply driving voltages to the image display unit, various changes in form and detail may be made by one having ordinary skill in the art and still be within the scope of the present invention as defined by the appended claims.

According to the embodiments of the present invention, a plurality of DC-DC converters are mounted on a film type connection device which is electrically connected to an image display unit, which solves the IR drop problem and improves the LRU of an organic light-emitting display device, thereby allowing for the manufacture of a large-size organic light-emitting device.