# US 8,570,253 B2 · Digital/analog converter, display device using the same, and display panel and driving method thereof

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- Number: US 8,570,253 B2
- Document ID: US8570253B2
- Status: Granted
- Kind: B2
- Application number: 11/229,127
- Filed: 2005-09-15
- Published: 2006-04-13
- Granted: 2013-10-29
- Earliest claimed: 2004-10-08
- Assignees: Samsung Display Co., Ltd.
- Applicants: Oh-Kyong Kwon
- Inventors: Oh-Kyong Kwon
- Web page: https://patentgrep.com/patent/US8570253B2

## CPC

- H03M 1/664: {Non-linear conversion not otherwise provided for in subgroups of H03M1/66}
- G09G 3/3208: organic, e.g. using organic light-emitting diodes [OLED]
- G09G 3/3283: in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
- G09G 2310/027: Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
- G09G 2320/0276: for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
- H03M 1/0607: {Offset or drift compensation (removal of offset already present on the analogue input signal H03M1/1295)}
- H03M 1/687: {Segmented, i.e. the more significant bit converter being of the unary decoded type and the less significant bit converter being of the binary weighted type}
- H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C)
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)

## Abstract

A digital/analog (D/A) converter, a light emitting display device using the converter, and a display panel and a driving method thereof. The display device according to an exemplary embodiment of the present invention includes: a display unit having a plurality of data lines for transmitting data currents, a plurality of scan lines for transmitting selection signals, and a plurality of pixel areas defined by the data lines and the scan lines; a data driver for dividing a plurality of grayscale data having a first data and a second data into at least two grayscale sections, converting the grayscale data into a data current, and applying the data current to a data line; and a scan driver for sequentially applying the selection signals to the plurality of scan lines.

## Claims

### Claim 1

A display device comprising:
a display unit comprising a plurality of data lines for transmitting data currents, a plurality of scan lines for transmitting selection signals, and a plurality of pixel areas defined by the data lines and the scan lines;
a data driver for dividing a plurality of grayscale data into at least two grayscale sections, converting at least one of the plurality of grayscale data into at least one of the data currents, and applying the at least one of the data currents to at least one of the data lines, each of the plurality of grayscale data comprising a high-order bit data and a low-order bit data; and
a scan driver for sequentially applying the selection signals to the plurality of scan lines,
wherein the data driver is configured to output a first current corresponding to a first grayscale section of the at least two grayscale sections by utilizing the high-order bit data, the first grayscale section being indicated by the at least one of the plurality of grayscale data,
wherein the data driver is configured to output a second current corresponding to the first grayscale section by utilizing the high-order bit data to select a reference signal, and utilizing the low-order bit data and the selected reference signal to control current variations for the second current,
wherein the data driver is configured to divide the first grayscale section into a first sub-grayscale section and a second sub-grayscale section by utilizing the low-order bit data, a first group of the grayscale data corresponding to the first sub-grayscale section and a second group of the grayscale data corresponding to the second sub-grayscale section, and to control current variations for the second current with respect to the first sub-grayscale section and the second sub-grayscale section, respectively, to be different in accordance with the same selected reference signal, and
wherein the data driver is configured to output the at least one of the data currents as a sum of the first current and the second current.

### Claim 2 (depends on 1)

The display device of claim 1, wherein the first current is an initial current for the first grayscale section.

### Claim 3 (depends on 1)

The display device of claim 1, wherein the first grayscale section is a lowermost grayscale section among the at least two grayscale sections.

### Claim 4 (depends on 3)

The display device of claim 3, wherein, in the first grayscale section, the first group of the grayscale data is a low grayscale data group, and the second group of the grayscale data is a high grayscale data group.

### Claim 5 (depends on 4)

The display device of claim 4, wherein the current variations of the second current for the second group of the grayscale data is set to be double the current variations of the second current for the first group of the grayscale data.

### Claim 6 (depends on 1)

The display device of claim 1, wherein the data driver comprises:
a shift register for receiving a first signal and a clock signal, and shifting the first signal in synchronization with the clock signal into a plurality of shifted signals;
a latch for latching the plurality of grayscale data in synchronization with the shifted signals from the shift register; and
a grayscale current generator for converting the plurality of grayscale data output from the latch into the data currents and outputting the data currents.

### Claim 7 (depends on 6)

The display device of claim 6, wherein the grayscale current generator comprises:
a first current output unit for outputting the first current corresponding to the first grayscale section by utilizing the high-order bit data;
a multiplexer for selecting a first reference voltage corresponding to the first grayscale section from a plurality of first voltages respectively corresponding to unit currents of the at least two grayscale sections and outputting the first reference voltage; and
a second current output unit for setting up the variations of the second current according to the low-order bit data in the first group of the grayscale data and the second group of the grayscale data, and outputting the second current by utilizing the low-order bit data and the first reference voltage output from the multiplexer.

### Claim 8 (depends on 7)

The display device of claim 7, wherein the first current output unit comprises:
a plurality of first transistors for respectively outputting a plurality of third currents corresponding to a second voltage; and
a plurality of first switches for responding to the high-order bit data and outputting the third currents from the first transistors as the first current.

### Claim 9 (depends on 8)

The display device of claim 8, wherein:
the second voltage is substantially the same as the first reference voltage;
the third currents are substantially the same as respective current periods of the at least two grayscale sections; and
the first current is substantially the same as a sum of the third currents.

### Claim 10 (depends on 7)

The display device of claim 7, wherein the second current output unit comprises:
a plurality of transistor groups, each of the transistor groups comprising at least two transistors, the at least two transistors being for respectively outputting fourth currents in response to the first reference voltage output by the multiplexer, the fourth currents of each of the transistor groups being substantially the same to each other;
a plurality of second switches for responding to the low-order bit data and outputting currents of the transistors from the transistor groups as the second current; and
a third switch being coupled with one of the at least two transistors in each of the transistor groups and a corresponding one of the second switches.

### Claim 11 (depends on 10)

The display device of claim 10, wherein currents output from the respective transistor groups are set to be different from each other.

### Claim 12 (depends on 10)

The display device of claim 10, wherein corresponding ones of the second switches for outputting the fourth currents of the at least two transistors included in one of the transistor groups are turned on concurrently.

### Claim 13 (depends on 10)

The display device of claim 10, wherein the third switch in each of the transistor groups is controlled to be all turned off when the grayscale data in the first group of the grayscale data is input, and the third switch in some of the transistor groups is controlled to be turned on when the grayscale data of the second group of the grayscale data is input.

### Claim 14 (depends on 13)

The display device of claim 13, wherein the third switch in each of the transistor groups is controlled to be turned on in all of the at least two grayscale sections except the first grayscale section.

### Claim 15

A display panel comprising:
a display unit comprising a plurality of pixels for displaying images according to an applied data current; and
a grayscale current generator for dividing a plurality of grayscale data into at least two grayscale sections, converting at least one of the plurality of grayscale data into the data current, and applying the data current to a data line, each of the plurality of grayscale data comprising a high-order bit data and a low-order bit data,
wherein the grayscale current generator is configured to generate a first current corresponding to a first grayscale section of the at least two grayscale sections by utilizing the high-order bit data, the first grayscale section being indicated by the at least one of the plurality of grayscale data, and
the grayscale current generator is configured to generate a second current corresponding to the first grayscale section by utilizing the high-order bit data to select a reference signal, and utilizing the low-order bit data and the selected reference signal to control current variations for the second current, wherein the grayscale current generator is configured to divide the first grayscale section into at least two sub-grayscale sections of the grayscale data by utilizing the low-order bit data, and to control current variations for the second current with respect to the at least two sub-grayscale sections of the grayscale data, respectively, to be different while using the same selected reference signal, and
wherein the grayscale current generator is configured to output the data current as a sum of the first current and the second current.

### Claim 16 (depends on 15)

The display panel of claim 15, wherein the first current is an initial current for the first grayscale section, and the variations of the second current correspond to the low-order bit data.

### Claim 17 (depends on 15)

The display panel of claim 15, wherein, among the at least two sub-grayscale sections, a variation of the second current in a low grayscale section of the at least two sub-grayscale sections is controlled to be smaller than a variation in a high grayscale section of the at least two sub-grayscale sections.

### Claim 18 (depends on 17)

The display panel of claim 17, wherein the grayscale current generator comprises:
a first current output unit for outputting the first current corresponding to the first grayscale section by utilizing the high-order bit data;
a multiplexer for selecting a first reference voltage corresponding to the first grayscale section from a plurality of first voltages respectively corresponding to unit currents of the at least two grayscale sections and outputting the first reference voltage; and
a second current output unit for setting up the variations of the second current in the at least two sub-grayscale sections, and outputting the second current by utilizing the low-order bit data and the first reference voltage output from the multiplexer.

### Claim 19

A driving method of a display panel in which a plurality of pixel circuits for displaying images in response to an input data current are formed, wherein a plurality of grayscale data are divided into at least two grayscale sections comprising a first grayscale section, each of the grayscale data comprising a high-order bit data and a low-order bit data, and the first grayscale section is divided into at least two sub-grayscale sections by utilizing the low-order bit, the method comprising:
generating a first current corresponding to the first grayscale section to which at least one of the plurality of grayscale data belongs by utilizing the high-order bit data of the grayscale data;
selectively outputting a first reference signal of the first grayscale section among first signals respectively corresponding to the at least two grayscale sections by utilizing the high-order bit data of the grayscale data;
generating a third current corresponding to the first reference signal and generating a second current by utilizing the third current and the low-order bit data of the grayscale data controlling current variations for the second current with respect to the at least two sub-grayscale sections of the grayscale data, respectively, to be different while using the same first reference signal; and
outputting the data current as a sum of the first current and the second current, wherein variations for the second current are controlled with respect to the at least two sub-grayscale sections of the grayscale data, respectively, with different references by utilizing the low-order bit data.

### Claim 20 (depends on 19)

The driving method of claim 19, wherein the first reference signal is a voltage corresponding to a unit current of the first grayscale section.