LIQUID CRYSTAL DISPLAY APPARATUS

• US 20120182332A1
• Filed: 01/11/2012
• Published: 07/19/2012
• Est. Priority Date: 01/17/2011
• Status: Active Grant

• Current Assignee: Hung-Ta Liu
• Original Assignee: Hung-Ta Liu
• Inventors: Liu, Hung-Ta
• Granted Patent: US 9,495,896 B2
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

The invention discloses a liquid crystal display (LCD) apparatus and a brightness/luminance holding ratio compensation method. A backlight module of the LCD apparatus may form a plurality of backlight shield-blocking periods in a display frame cycle or adjust output brightness gradually, for compensating a brightness/luminance bias caused by a transmittance variance of liquid crystal cell in the low refresh rate driving LCD apparatus, so as to avoid some abnormal display effects, such as screen flicker. Besides, the LCD apparatus has better energy efficiency by utilizing a low-voltage gray level driving method or saving the power consumption of the backlight module.

Claims

1. A liquid crystal display apparatus with brightness/luminance holding ratio compensation, comprising:

a liquid crystal display panel having a refresh rate, wherein a transmittance or brightness/luminance of the liquid crystal display panel changes over time in a display frame cycle;

a driving circuit for driving the liquid crystal display panel according to a driving voltage; and

a backlight module comprising;

a backlight source;

a backlight driving circuit for driving the backlight source; and

a backlight control circuit for forming a plurality of backlight shield-blocking periods in the display frame cycle and controlling the backlight driving circuit to temporarily turn off or turn dark the backlight source or temporarily turn down the backlight source to a dark state in the backlight shield-blocking periods.

2. The liquid crystal display apparatus of claim 1, wherein the refresh rate is lower than or equal to 20 Hz.

3. The liquid crystal display apparatus of claim 1, wherein the liquid crystal display panel has two or more refresh rates.

4. The liquid crystal display apparatus of claim 1, wherein the liquid crystal display panel is a normally white mode liquid crystal display panel, and a shield-blocking persistent length of the backlight shield-blocking periods sequentially increases in the display frame cycle.

5. The liquid crystal display apparatus of claim 1, wherein the liquid crystal display panel is a normally black mode liquid crystal display panel, and a shield-blocking persistent length of the backlight shield-blocking periods sequentially decreases in the display frame cycle.

6. The liquid crystal display apparatus of claim 1, wherein the display frame cycle is divided into N cycle intervals, and the backlight control circuit forms at least one backlight shield-blocking period in each cycle interval, thus totally forming at least N backlight shield-blocking periods.

7. The liquid crystal display apparatus of claim 1, wherein the display frame cycle is divided into N cycle intervals, and the difference of an optical integration of the transmittance or brightness/luminance of the liquid crystal display apparatus to time for each cycle interval is less than or equal to 5%.

8. The liquid crystal display apparatus of claim 1, wherein the backlight control circuit further comprises a display driving conversion reference table, and during the display frame cycle, the backlight control circuit controls the backlight driving circuit to turn off or turn dark the backlight source and forms a plurality of backlight shield-blocking periods according to the display driving conversion reference table, so as to compensate the effect of the transmittance increasing or decreasing over time.

9. A liquid crystal display apparatus with brightness/luminance holding ratio compensation, at least comprising:

an liquid crystal display panel, having a refresh rate, wherein a transmittance or brightness/luminance of the liquid crystal display panel changes over time in a display frame cycle;

a driving circuit, for driving the liquid crystal display panel according to a driving voltage; and

a backlight module, comprising;

a backlight source;

a backlight driving circuit, providing a backlight driving current for driving the backlight source; and

a backlight control circuit, controlling the backlight driving circuit to gradually or gradiently adjust the backlight driving current in the display frame cycle, so as to make the brightness/luminance of the backlight source change over time.

10. The liquid crystal display apparatus of claim 9, wherein the liquid crystal display panel has two or more refresh rates.

11. The liquid crystal display apparatus of claim 9, wherein the liquid crystal display panel is a normally white mode liquid crystal display panel, the backlight control circuit controls the backlight driving circuit to gradually or gradiently decrease the backlight driving current in the display frame cycle, so as to make the brightness/luminance of the backlight source decrease over time.

12. The liquid crystal display apparatus of claim 11, wherein a variation curve of a transmittance or brightness/luminance versus a liquid crystal driving voltage of the liquid crystal display panel is divided into a plurality of gray level intervals, each of the gray level intervals corresponds to a compensation coefficient of the backlight control circuit, and during each gray level interval, the backlight control circuit controls the backlight driving circuit to gradually or gradiently decrease the backlight driving current according to the compensation coefficient, so as to make the brightness/luminance of the backlight source decrease over time.

13. The liquid crystal display apparatus of claim 11, wherein the display frame cycle is divided into N cycle intervals, and in each cycle interval, the backlight control circuit controls the backlight driving circuit to gradually or gradiently decrease the backlight driving current, so as to make the brightness/luminance of the backlight source decrease along with different cycle intervals.

14. The liquid crystal display apparatus of claim 9, wherein the liquid crystal display panel is a normally black mode liquid crystal display panel, and during the display frame cycle, the backlight control circuit controls the backlight driving circuit to gradually or gradiently increase the backlight driving current, so as to make the brightness/luminance of the backlight source increase over time.

15. The liquid crystal display apparatus of claim 14, wherein a variation curve of the transmittance or brightness/luminance versus a liquid crystal driving voltage of the liquid crystal display panel is divided into a plurality of gray level intervals, each of the gray level intervals corresponds to a compensation coefficient of the backlight control circuit, and during each gray level interval, the backlight control circuit controls the backlight driving circuit to gradually or gradiently increase the backlight driving current according to the compensation coefficient, so as to make the brightness/luminance of the backlight source increase over time.

16. The liquid crystal display apparatus of claim 14, wherein the display frame cycle is divided into N cycle intervals, and in each cycle interval, the backlight control circuit controls the backlight driving circuit to gradually or gradiently increase the backlight driving current, so as to make the brightness/luminance of the backlight source increase along with different cycle intervals.

17. The liquid crystal display apparatus of claim 9, wherein the backlight control circuit further comprises a display driving conversion reference table, and during the display frame cycle, the backlight control circuit controls the backlight driving circuit according to the display driving conversion reference table, so as to compensate the effect of the transmittance increasing or decreasing over time.

18. The liquid crystal display apparatus of claim 9, wherein the display frame cycle is divided into N cycle intervals, and the difference of an optical integration of the transmittance or brightness/luminance of the liquid crystal display apparatus to time for each cycle interval is less than or equal to 5%.

19. A liquid crystal display apparatus, comprising:

a register, for catching an image information;

an liquid crystal display panel, wherein the liquid crystal display panel is a transmissive or transflective normally white mode liquid crystal display panel and has a refresh rate;

a driving circuit, for driving the liquid crystal display panel according to a driving voltage, wherein the liquid crystal display panel has a transmittance or brightness/luminance according to the driving voltage;

a backlight module, comprising;

a backlight source; and

a backlight driving circuit, providing a backlight driving current for driving the backlight source, so as to make the backlight source generate a light ray passing through the liquid crystal display panel; and

a control unit, for calculating and determining the image information of the register, wherein when the dim or dark state of the image frame reaches a certain degree, or an average driving voltage value of the image information is higher than a driving voltage reference value, the transmittance is low, and thus the control unit automatically converts the driving voltage of the image information to a lower driving voltage, so as to increase the transmittance, and correspondingly decreases the level of the backlight driving current or the brightness/luminance of the backlight module, or correspondingly adjusts the turn-on, turn-off or turn-dark period of the backlight.

20. The liquid crystal display apparatus of claim 19, wherein the backlight module automatically sets a proportion of the backlight turn-on, turn-off or turn-dark period (backlight on/off period ratio) or a proportion of the plurality of backlight shield-blocking periods in each display frame cycle, so as to decrease the brightness/luminance of the backlight source in the display frame cycle for compensation, thereby corresponding to the brightness levels of the high transmittance at the lower driving voltage levels.

21. The liquid crystal display apparatus of claim 19, further comprising a backlight control circuit, wherein in the display frame cycle, the backlight control circuit controls the backlight driving circuit to gradually or gradiently decrease the backlight driving current, so as to make the brightness/luminance of the backlight source decrease over time.

22. The liquid crystal display apparatus of claim 19, further comprising a backlight control circuit, wherein the backlight control circuit forms a plurality of backlight shield-blocking periods in the display frame cycle, the backlight control circuit controls the backlight driving circuit to temporarily turn off the backlight source or temporarily turn down the backlight source to a dark state in the backlight shield-blocking periods, and a backlight shield-blocking persistent period of the backlight shield-blocking periods sequentially increases, to decrease the brightness/luminance of the backlight.

23. The liquid crystal display apparatus of claim 19, wherein the backlight module further comprises a display driving conversion reference table, and during the display frame cycle, the backlight module controls the backlight driving circuit according to the display driving conversion reference table, so as to compensate the effect of the transmittance or brightness/luminance decreasing over time in the cycle.