Control circuit of panel brightness

• US 6,943,784 B2
• Filed: 03/29/2002
• Issued: 09/13/2005
• Est. Priority Date: 05/01/2001
• Status: Active Grant

• Current Assignee: VIA Technologies Incorporated (VIA Technologies)
• Original Assignee: VIA Technologies Incorporated (VIA Technologies)
• Inventors: Cho, Yu-Bin, Kuo, Hubert
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): Kovalick, Vincent E.
• Application Number:
  US10/108,893
• Publication Number:
  US 20020163489A1
• Time in Patent Office: 1,264 Days
• Field of Search: 345/87, 345/89, 345/204, 345/205, 345/207, 345/214, 345/690, 349/19, 349/56, 349/102
• US Class Current: 345/204
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

A control circuit of panel brightness is disclosed. After a user adjusts a brightness volume control, the brightness volume control will output an adjusting signal. The control circuit of this invention includes a pre-stage circuit, a first brightness control circuit, and a second brightness control circuit. The pre-stage circuit is fro receiving a darkness-adjusting signal, a brightness-adjusting signal, and an enable signal. A first brightness value outputted from the first brightness control circuit can be the first brightness value of the previous time point plus or minus a interval. A second brightness value outputted from the second brightness control circuit can be the second brightness value of the previous time point plus or minus a interval. The first brightness value and the second brightness value are for adjusting panel brightness. The circuit of this invention is simple, easy to design, and less cost.

Claims

1. A control circuit of panel brightness, which responds to an adjustment signal to adjust a panel brightness, comprises:

a pre-stage circuit, for receiving the adjustment signal to obtain a darkness-adjusting signal and a brightness-adjusting signal, the pre-stage circuit further outputting an enable signal related to the darkness-adjusting signal and the brightness-adjusting signal;

a first brightness control circuit, for outputting an adjusted first brightness value and receiving the first brightness value, the first brightness control circuit controlled by the enable signal, the darkness-adjusting signal and the brightness-adjusting signal, wherein the first brightness value is obtained according to the related first brightness value and an interval; and

a second brightness control circuit, for outputting an adjusted second brightness value, and receiving a second brightness value, the second brightness control circuit controlled by the enable signal, the darkness-adjusting signal and the brightness-adjusting signal, wherein the second brightness value is obtained according to the second brightness value and an interval;

wherein the first brightness value and the second brightness value are used for adjusting panel brightness.

2. The control circuit as claim 1, wherein the panel brightness is related to the ratio of the first brightness value to the second brightness value.

3. The control circuit as claim 1, wherein the first brightness control circuit comprises:

a first adder, for receiving the first brightness value in a previous time point, and controlled by a control signal, wherein when the control signal is a first value, the first adder outputs a first adjusted brightness value, which is the sum of the first brightness value and the interval, when the control signal is a second value, the first adder outputs a first adjusted brightness value, which is the subtraction of the interval from the first brightness value, and the control signal is either the brightness-adjusting signal or the darkness-adjusting signal;

a first limiter, for receiving the first adjusted brightness value and outputting a first limiter output, wherein when the first adjusted brightness value is between a first upper limit value and a first lower limit value, the first limiter output is equal to the first adjusted value;

when the first adjusted brightness value is greater than the first upper limit value, the first limiter output is equal to the first upper limit value; and

when the first adjusted brightness value is smaller than the first lower limit value, the first limiter output is equal to the first lower limit value; and

a first flip-flop, outputting the first limiter output as the first brightness value when triggered by the enable signal.

4. The control circuit as claim 1, wherein the first upper limit value and the first lower limit value are the allowable values between the maximum and minimum of the first brightness value.

5. The control circuit as claim 1, wherein the second brightness control circuit comprises:

a second adder, for receiving the second brightness value in a previous time point, and controlled by a control signal, wherein when the control signal is a first value, the second adder outputs a second adjusted brightness value, which is the sum of the second brightness value and the interval, when the control signal is a second value, the second adder outputs a second adjusted brightness value, which is the subtraction of the interval from the second brightness value, and the control signal is either the brightness-adjusting signal or the darkness-adjusting signal;

a second limiter, for receiving the second adjusted brightness value, and outputting a second limiter output, wherein when the second adjusted brightness value is between a second upper limit value, and a second lower limit value, the second limiter output is equal to the f second adjusted value, when the second adjusted brightness value is greater than the second upper limit value, the second limiter output is equal to the second upper limit value; and

when the second adjusted brightness value is smaller than the second lower limit value, the second limiter output is equal to the second lower limit value; and

a second flip- flop, outputting the second limiter output as the second brightness value when triggered by the enable signal.

6. The control circuit as claim 5, wherein the second upper limit value and the second lower limit value are the allowable values between the maximum and minimum of the second brightness value.

7. The control circuit as claim 1, the control circuit is applied to a Liquid Crystal Display.

8. The control circuit as claim 7, the Liquid Crystal Display is a Thin Film Transistor Liquid Crystal Display.

9. The control circuit as claim 7, the Liquid Crystal Display is a Double Super-twisted nematic mode (DSTN) Liquid Crystal Display.

10. The control circuit as claim 1, wherein the first brightness control circuit and the second brightness control circuit each affect a single overall brightness of an entirety of the panel.

11. A control circuit of panel brightness, which responds to an adjustment signal to adjust the panel brightness, comprises:

a pre-stage circuit, for receiving the adjustment signal to obtain a darkness-adjusting signal and a brightness-adjusting signal, the pre-stage circuit further outputting an enable signal related to the darkness-adjusting signal and the brightness-adjusting signal;

a first brightness control circuit, for outputting an adjusted first brightness value, comprising;

a first adder, controlled by the enable signal, for receiving the first brightness value in a previous time point and, outputting a first adjusted brightness value, the first adjusted brightness value being equal to the sum of the first brightness value and the interval, or the subtraction of the interval from the first brightness value;

a first limiter, for receiving the first adjusted brightness value, and outputting a first limiter output related to the first adjusted brightness value, the first limiter output being between the first upper limit value and the first lower limit value; and

a first flip-flop, for receiving the first limiter output, and outputting the first brightness value when triggered by the enable signal; and

a second brightness control circuit, for outputting an adjusted second brightness value, comprising;

a second adder, controlled by an enable signal, for receiving the second brightness value and outputting a second adjusted brightness value, the second adjusted brightness value being equal to the sum of the second brightness value and the interval, or the subtraction of the interval from the second brightness value;

a second limiter, for receiving the second adjusted brightness value, and outputting a second limiter output related to the second adjusted brightness value, the second limiter output being between the second upper limit value and the second lower limit value; and

a second flip-flop, for receiving the second limiter output and outputting the second brightness value when triggered by the enable signal;

wherein the fist brightness value and the second brightness value are for adjusting the panel brightness.

12. The control circuit as claim 11, wherein when the enable signal is a first value, the first adder outputs a first adjusted brightness value, which is the sum of the first brightness value and the interval, and when the enable signal is a second value, the first adder outputs the first adjusted brightness value, which is the subtraction of the interval from the first brightness value.

13. The control circuit as claim 11, wherein, when the first adjusted brightness value is greater than the first upper limit value, the first limiter output is equal to the first upper limit value;

and when the first adjusted brightness value is smaller than the first lower limit value, the first limiter output is equal to the first lower limit value.

14. The control circuit as claim 11, wherein when the enable signal is a first value, the second adder outputs a second adjusted brightness value, which is the sum of the second brightness value and the interval, and when the enable signal is a second value, the second adder outputs a second adjusted brightness value, which is the subtraction of the interval from the second brightness value.

15. The control circuit as claim 11, wherein when the second adjusted brightness value is greater than the second upper limit value, the second limiter output is equal to the second upper limit value;

and when the second adjusted brightness value is smaller than the second lower limit value, the second limiter output is equal to the second lower limit value.

16. The control circuit as claim 11, the control circuit is applied to a Liquid Crystal Display.

17. The control circuit as claim 16, the Liquid Crystal Display is a Thin Film Transistor Liquid Crystal Display.

18. The control circuit as claim 16, the Liquid Crystal Display is a Double Super-twisted nematic mode (DSTN) Liquid Crystal Display.

19. A method for adjusting brightness of a panel according to an adjustment signal, the panel comprising a pre-stage circuit, a first brightness control circuit, and a second brightness control circuit, the method comprising:

receiving the adjustment signal to obtain a darkness-adjusting signal and a brightness-adjusting signal by the pre-stage circuit;

outputing an enable signal related to the darkness-adjusting signal and the brightness-adjusting signal by the pre-stage circuit;

outputting an adjusted first brightness value and receiving the first brightness value by the first brightness control circuit under the control of the enable signal, the darkness-adjusting signal, and the brightness-adjusting signal, wherein the first brightness value is obtained according to the related first brightness value and an interval; and

outputting an adjusted second brightness value, and receiving a second brightness value by the second brightness control circuit under the control of the enable signal, the darkness-adjusting signal, and the brightness-adjusting signal, wherein the second brightness value is obtained according to the second brightness value and an interval;

wherein the first brightness value and the second brightness value are used for adjusting panel brightness.

20. The method for adjusting brightness of a panel according to claim 19, the first brightness control circuit including a first adder, a first limiter, and a first flip-flop, the method further comprising:

receiving the first brightness value in a previous time point by the first adder under the control of a control signal, wherein when the control signal is a first value, the first adder outputs a first adjusted brightness value, which is the sum of the first brightness value and the interval, when the control signal is a second value, the first adder outputs a first adjusted brightness value, which is the subtraction of the interval from the first brightness value, and wherein the control signal is either the brightness-adjusting signal or the darkness-adjusting signal;

receiving the first adjusted brightness value and outputting a first limiter output by the first limiter, wherein when the first adjusted brightness value is between a first upper limit value and a first lower limit value, the first limiter output is equal to the first adjusted value;

when the first adjusted brightness value is greater than the first upper limit value, the first limiter output is equal to the first upper limit value; and

when the first adjusted brightness value is smaller than the first lower limit value, the first limiter output is equal to the first lower limit value; and

outputting the first limiter output as the first brightness value responsive to the enable signal by a first flip-flop.

21. A method for adjusting brightness of a panel according to an adjustment signal, comprising:

receiving the adjustment signal to obtain a darkness-adjusting signal and a brightness-adjusting signal;

outputting an enable signal related to the darkness-adjusting signal and the brightness-adjusting signal;

outputting an adjusted first brightness value and receiving the first brightness value under the control of the enable signal, the darkness-adjusting signal, and the brightness-adjusting signal, wherein the first brightness value is obtained according to the related first brightness value and an interval; and

outputting an adjusted second brightness value, and receiving a second brightness value under the control of the enable signal, the darkness-adjusting signal, and the brightness-adjusting signal, wherein the second brightness value is obtained according to the second brightness value and an interval;

wherein the first brightness value and the second brightness value are used for adjusting panel brightness.

22. The method for adjusting brightness of a panel according to claim 21, further comprising:

receiving the first brightness value in a previous time point under the control of a control signal;

outputting a first adjusted brightness value, wherein when the control signal is a first value, the first adjusted brightness value is the suni of the first brightness value and the interval, when the control signal is a second value, the first adjusted brightness value is the subtraction of the interval from the first brightness value, and wherein the control signal is either the brightness-adjusting signal or the darkness-adjusting signal;

receiving the first adjusted brightness value and outputting a first limiter output, wherein when the first adjusted brightness value is between a first upper limit value and a first lower limit value, the first limiter output is equal to the first adjusted value;

when the first adjusted brightness value is greater than the first upper limit value, the first limiter output is equal to the first upper limit value; and

when the first adjusted brightness value is smaller than the first lower limit value, the first limiter output is equal to the first lower limit value; and

outputting the first limiter output as the first brightness value responsive to the enable signal.