Digital/analog converter, display device using the same, and display panel and driving method thereof

• US 20060077142A1
• Filed: 09/15/2005
• Published: 04/13/2006
• Est. Priority Date: 10/08/2004
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Kwon, Oh-Kyong
• Granted Patent: US 8,570,253 B2
• Time in Patent Office: Days
• US Class Current: 345/77
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: 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
• CPC Class Codes: H03M 1/0607 Offset or drift compensation removal of offset already present on the analogue input signal H03M1/1295
• CPC Class Codes: H03M 1/664 Non-linear conversion not otherwise provided for in subgroups of H03M1/66
• CPC Class Codes: 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

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

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 respective data lines and scan lines;

a data driver for dividing a plurality of grayscale data into at least two grayscale sections, converting 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, the plurality of grayscale data comprising a first data and a second data; and

a scan driver for sequentially applying the selection signals to the plurality of scan lines,

wherein the data driver outputs a first current corresponding to a first grayscale section of the at least two grayscale sections by using the first data, the first grayscale section being indicated by at least one of the plurality of grayscale data,

wherein the data driver outputs a second current corresponding to the first grayscale section by using the second data, and

wherein the data driver divides the plurality of grayscale data into a first group of the grayscale data and a second group of the grayscale data by using the second data, and respectively controls current variations for the second current with respect to the first group of the grayscale data and the second group of the grayscale data with different references.

2. The display device of claim 1, wherein the first data is a high-order bit data of the grayscale data, and the second data is a low-order bit data of the grayscale data.

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

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

5. The display device of claim 4, 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.

6. The display device of claim 5, wherein the variations of the second current in the second group of the grayscale data is set to be double the respective variations of the second current in the first group of the grayscale data.

7. 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 respective 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.

8. The display device of claim 7, wherein the grayscale current generator comprises:

a first current output unit for outputting the first current corresponding to the first grayscale section by using the first 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 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 second data in the first group of the grayscale data and the second group of the grayscale data, and outputting the second current by using the second data and the first reference voltage output from the multiplexer.

9. The display device of claim 8, 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 first data and outputting the third currents from the first transistors as the first current.

10. The display device of claim 9, 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 grayscale sections; and

the first current is substantially the same as a sum of the third currents.

11. The display device of claim 8, 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 second data and outputting currents of the transistors from the second transistor groups as the second current; and

a third switch being coupled with one of the at least two transistors in each of the second transistor groups and a respective one of the second switches.

12. The display device of claim 11, wherein the currents output from the respective second transistor groups are respectively set to be different from each other.

13. The display device of claim 11, wherein the second switches for outputting the currents of the transistors included in a respective one of the second transistor group are turned on simultaneously.

14. The display device of claim 11, wherein the third switch in each of the second 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 second transistor groups is controlled to be turned on when the grayscale data of the second group of the grayscale data is input.

15. The display device of claim 14, wherein the third switch in each of the second transistor groups is controlled to be turned on in all grayscale sections except the first grayscale section.

16. 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, the plurality of grayscale data comprising a first data and a second data,

wherein the grayscale current generator generates a first current corresponding to a first grayscale section of the at least two grayscale sections by using the first data, the first grayscale section being indicated by the at least one of the plurality of grayscale data, and

generates a second current corresponding to the first grayscale section by using the second data, wherein the grayscale current generator divides the first grayscale section into at least two sub-grayscale sections of the grayscale data by using the second data, and respectively controls current variations for the second current with respect to the at least two sub-grayscale sections of the grayscale data with different references.

17. The display panel of claim 16, wherein the first current is an initial current for the first grayscale section, and the variations of the second current correspond to the second data.

18. The display panel of claim 16, 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.

19. The display panel of claim 18, wherein the grayscale current generator comprises:

a first current output unit for outputting the first current corresponding to the first grayscale section by using the first 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 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 sub-grayscale sections, and outputting the second current by using the second data and the first reference voltage output from the multiplexer.

20. A digital/analog converter for converting a plurality of grayscale data into grayscale currents and outputting the grayscale currents, the digital/analog converter dividing the plurality of grayscale data into at least two grayscale sections including a first grayscale section, and converting the plurality of grayscale data into the grayscale currents, the digital/analog converter comprising:

a first current output unit for outputting a first current corresponding to the first grayscale section by using a first data among the grayscale 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 grayscale sections and outputting the first reference voltage; and

a second current output unit for dividing the first grayscale section into at least two sub-grayscale sections and generating a second current by using a second data among the grayscale data and the first reference voltage output from the multiplexer,

wherein the second current output unit respectively controls current variations for the second current with respect to the at least two sub-grayscale sections with different references by using the second data.

21. The digital/analog converter of claim 20, wherein the first grayscale section is a lowest grayscale section among the plurality of grayscale sections.

22. The digital/analog converter of claim 20, 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 respective variation in a high grayscale section of the at least two sub-grayscale sections,

23. A digital/analog converter for converting a plurality of grayscale data into grayscale currents and outputting them comprising:

a reference current output unit for outputting a plurality of reference currents by using a first data among the grayscale data;

a multiplexer for receiving respective unit currents corresponding to the plurality of reference currents and selectively outputting a corresponding one of the unit currents based on the first data;

a fine current output unit for outputting a plurality of fine currents based on the corresponding one of the unit currents output by the multiplexer and a second data other than the first data among the grayscale data; and

a switch for being turned on based on the second data and selectively transmitting the plurality of fine currents output by the fine current output unit to an output terminal,

wherein a respective one of the grayscale currents belongs to one of a plurality of grayscale current sections divided with reference to the plurality of reference currents, wherein a first grayscale current section among the plurality of grayscale current sections is divided into at least two sub-grayscale sections of the grayscale data by using the second data, and wherein the switch divides the grayscale data into the at least two sub-grayscale sections of the grayscale data by using the second data, and controls current variations for the fine currents with respect to the at least two sub-grayscale sections of the grayscale data with different references.

24. The digital/analog converter of claim 23, wherein the fine current output unit comprises:

a first transistor and a second transistor for outputting a first current in response to the corresponding one of the unit currents output by the multiplexer and to a first bit of the second data;

a third transistor and a fourth transistor for outputting a second current in response to the corresponding one of the unit currents output by the multiplexer and to a second bit of the second data;

a fifth transistor and a sixth transistor for outputting a third current in response to the corresponding one of the unit currents output by the multiplexer and to a third bit of the second data; and

a seventh transistor and an eighth transistor for outputting a fourth current in response to the corresponding one of the unit currents output by the multiplexer and to a fourth bit of the second data.

25. The digital/analog converter of claim 24, wherein the switch comprises:

a first switch for being turned on in response to the fourth bit of the second data, and coupling the second transistor with the output terminal;

a second switch for being turned on in response to the fourth bit of the second data, and coupling the fourth transistor with the output terminal; and

a third switch for being turned on in response to the fourth bit of the second data, and coupling the sixth transistor with the output terminal.

26. The digital/analog converter of claim 25, wherein the switch comprises:

a fourth switch for coupling the second transistor with the output terminal according to the first data;

a fifth switch for coupling the fourth transistor with the output terminal according to the first data;

a sixth switch for coupling the sixth transistor with the output terminal according to the first data; and

a seventh switch for coupling the eighth transistor with the output terminal according to the first data.

27. 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, and the first grayscale section comprises two sub-grayscale sections, 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 using a first 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;

generating a third current corresponding to the first reference signal and generating a second current by using the third current and a second data of the grayscale data; and

combining the first current and the second current and outputting them as the data current, wherein variations for the second current are respectively controlled with respect to the at least two sub-grayscale sections of the grayscale data with different references by using the second data.

28. The driving method of claim 27, wherein the first reference signal is a voltage corresponding to a unit current of the first grayscale section.