DISPLAY APPARATUS AND CONTROL METHOD THEREOF

• US 20100156866A1
• Filed: 06/10/2009
• Published: 06/24/2010
• Est. Priority Date: 12/24/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: YEO, Dong-Hyun, Park, Jae-Hyoung, Jeon, Byung-Kil
• Granted Patent: US 8,519,940 B2
• Time in Patent Office: Days
• US Class Current: 345/208
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2330/06 Handling electromagnetic interferences [EMI], covering emitted as well as received electromagnetic radiation
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

The present invention relates to a display apparatus to synchronize a synchronous signal and an inverter driving signal in response to a display mode, and a control method thereof. A back light unit of the display apparatus makes a back light to dim based on an inverter driving signal, and a dimming frequency of the back light varies in response to a synchronous signal frequency of the image. When a synchronous signal having an abnormal frequency is inputted to the back light unit for several seconds, the back light unit holds the frequency of the inverter driving signal and the frequency of the inverter driving signal varies smoothly in response to the display mode.

Claims

1. A display apparatus, comprising:

a display panel to display an image according to a synchronous signal; and

a back light unit to emit a light to the display panel,

wherein the light is controlled by an inverter driving signal, a frequency of the inverter driving signal varies in response to a frequency of the synchronous signal.

2. The display apparatus of claim 1, the back light unit comprising;

a back light to receive a power and to emit the light;

an inverter to supply the power to the back light in response to the inverter driving signal;

a driving signal generator to generate the inverter driving signal having the frequency which equals a ratio multiplied by the frequency of the synchronous signal; and

a controller to recognize a change of the frequency of the synchronous signal, the controller to control the driving signal generator by a control signal,

wherein the back light dims based on the inverter driving signal.

3. The display apparatus of claim 2, wherein the frequency of the inverter driving signal varies after a number of frames based on the change of the frequency of the synchronous signal.

4. The display apparatus of claim 2, wherein the synchronous signal comprises a horizontal synchronous signal and a vertical synchronous signal.

5. The display apparatus of claim 3, wherein the controller comprises:

a mode counter to receive the synchronous signal and a count clock comprising a period from a exterior source, the mode counter to transmit a vertical count value of a frame;

a register to store a registered vertical count value;

a comparator to receive the vertical count value of a previous frame and a current frame from the mode counter and the registered vertical count value from the register, the comparator to transmit a compare signal; and

a sync counter to receive the compare signal from the comparator and to transmit the control signal to the driving signal generator,

wherein the vertical count value of the frame is a length of one period of the synchronous signal, the length of one period being based on a number of the count clock periods.

6. The display apparatus of claim 5, wherein:

the sync counter holds a sync counter value as zero or resets to zero when the sync counter receives the compare signal, and the compare signal indicates the vertical count value of the current frame and the registered vertical count value are the same;

the sync counter increases the sync counter value by one when the vertical count value of the current frame is different from the registered vertical count value and the sync counter value is zero at the previous frame, or when the vertical count value of the current frame is different from the registered vertical count value and the vertical count value of the previous frame and the vertical count value of the current frame are the same; and

the sync counter holds the sync counter value as a current value when the sync counter 11 value at the previous frame is not zero and the vertical count value of the previous frame and the vertical count value of the current frame are different.

7. The display apparatus of claim 6, wherein the sync counter determines that the frequency of the synchronous signal is changed and sends the control signal to the driving signal generator to change the frequency of the inverter driving signal as the changed frequency of the synchronous signal multiplied by the ratio, when the sync counter value becomes the same as a predetermined number.

8. The display apparatus of claim 7, wherein the registered vertical count value is updated to the current vertical count value, when the sync counter sends the control signal to the driving signal generator to change the frequency of the inverter driving signal.

9. A back light unit for a display apparatus, comprising:

a back light to receive a power and to emit a light;

an inverter to supply the power to the back light in response to an inverter driving signal;

a driving signal generator to generate the inverter driving signal having a frequency which equals a ratio multiplied by a frequency of a synchronous signal; and

a controller to recognize a change of the frequency of the synchronous signal, the controller to control the driving signal generator by a control signal,

wherein the back light dims based on the inverter driving signal, and the frequency of the inverter driving signal varies in response to the frequency of the synchronous signal.

10. The back light unit of claim 9, wherein the frequency of the inverter driving signal varies after a number of frames based on the change of the frequency of the synchronous signal.

11. The display apparatus of claim 9, wherein the synchronous signal comprises a horizontal synchronous signal and a vertical synchronous signal.

12. The back light unit according to claim 10, the controller comprising;

a mode counter to receive the synchronous signal and a count clock comprising a period from a exterior source, the mode counter to transmit a vertical count value of a frame;

a register to store a registered vertical count value;

a comparator to receive the vertical count value of a previous frame and a current frame from the mode counter, the registered vertical count value from the register, and to transmit a compare signal; and

a sync counter to receive the compare signal from the comparator and to transmit the control signal to the driving signal generator,

wherein the vertical count value of the frame is a length of one period of the synchronous signal, the length of one period based on a number of the periods of the count clock.

13. The back light unit of claim 12, wherein:

the sync counter holds a sync counter value as zero or resets to zero when the sync counter receives the compare signal, the compare signal indicates the vertical count value of the current frame and the registered vertical count value are the same;

the sync counter increases the sync counter value by one when the vertical count value of the current frame is different from the registered vertical count value and the sync counter value is zero at the previous frame, or when the vertical count value of the current frame is different from the registered vertical count value and the vertical count value of the previous frame and the vertical count value of the current frame are the same; and

the sync counter holds the sync counter value as a current value when the sync counter value is not zero and the vertical count value of the previous frame and the vertical count value of the current frame are different.

14. The back light unit of claim 13, wherein when the sync counter value becomes the same as a predetermined number, the sync counter determines the frequency of the synchronous signal is changed and sends the control signal to the driving signal generator to change the frequency of the inverter driving signal as the changed frequency of the synchronous signal multiplied by the ratio.

15. The display apparatus of claim 14, wherein the registered vertical count value is updated to the current vertical count value, when the sync counter sends to the control signal to the driving signal generator to change the frequency of the inverter driving signal.

16. A control method of a display apparatus, the method comprising:

generating an inverter driving signal, the inverter driving signal having a frequency which equals a ratio multiplied by a frequency of a synchronous signal and varying after a number of frames based on a change of the frequency of the the synchronous signal.

17. The method of claim 16, wherein the generating the inverter driving signal comprises;

counting a vertical count value for at least one frame, the vertical count value being a length of one period of the synchronous signal based on a number of periods of a count clock;

comparing the vertical count value of a previous frame and a current frame and a registered vertical count value;

calculating a sync counter value based on the comparison result of the vertical count value of the previous frame, the current frame and the registered vertical count value; and

changing the frequency of the inverter driving signal based on the sync counter value.

18. The method of claim 17, wherein the calculating the sync counter value comprises;

holding the sync counter value as zero or resetting to zero when the vertical count value of the current frame and the registered vertical count value are the same;

increasing the sync counter value by one when the vertical count value of the current frame is different from the registered vertical count value and the sync counter value is zero at the previous frame, or when the vertical count value of the current frame is different from the registered vertical count value and the vertical count value of the previous frame and the vertical count value of the current frame are the same; and

holding the sync counter value as a current value when the sync counter value at the previous frame is not zero, and the vertical count value of the previous frame and the vertical count value of the current frame are different.

19. The method of claim 18, wherein the changing the frequency of the inverter driving signal comprises changing the the frequency of the inverter driving signal as the changed frequency of the synchronous signal multiplied by the ratio when the sync counter value becomes the same as a predetermined number.