Brightness control and power control of display device

• US 5,956,014 A
• Filed: 10/18/1995
• Issued: 09/21/1999
• Est. Priority Date: 10/19/1994
• Status: Expired due to Term

• Current Assignee: Hitachi Maxell Limited (Hitachi, Ltd.)
• Original Assignee: Fujitsu Limited
• Inventors: Tanahashi, Rikurou, Kishi, Tomokatsu, Yamamoto, Akira, Kuriyama, Hirohito, Kameyama, Shigeki, Kaneko, Keiichi, Tajima, Masaya, Tomio, Shigetoshi
• Primary Examiner(s): BRIER, JEFFERY A
• Application Number:
  US08/544,590
• Time in Patent Office: 1,434 Days
• Field of Search: 345/63, 345/77, 345/147, 345/211, 345/212, 345/89, 348/686, 348/687
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/045 Protection against panel overheating
• CPC Class Codes: G09G 3/293 for address discharge
• CPC Class Codes: G09G 3/297 using opposed discharge type panels
• CPC Class Codes: G09G 3/298 using surface discharge panels

Abstract

In a plasma display panel, an analogue brightness value given by a variable resistor is periodically converted into a digital brightness value and stored in a memory. A digital brightness value of a current period is compared with the digital brightness value of the next preceding period stored in the memory, to produce a difference brightness value which is compared with a predetermined brightness value and, if larger than the predetermined value, the brightness value stored in the memory is updated. Alternatively, power consumption of a display device is detected and, when the power consumption is larger than a set point, a brightness value is gradually decreased and, when the power consumption is smaller than the set point, the brightness value is gradually adjusted to a brightness set value.

Claims

1. A display apparatus comprising:

a display panel including a plurality of display cells;

a storage unit for storing a brightness value;

an operation unit calculating a difference between a brightness value input to the operation unit and said brightness value stored in said storage unit, and updating said brightness value stored in said storage unit when the calculated difference is larger than a reference value; and

a display driver for individually driving the display cells of said display panel in response to the brightness value stored in said storage unit.

2. A display apparatus as claimed in claim 1, further comprising:

a brightness control pulse generator periodically generating a brightness control pulse, a duration of which is proportional to an analog brightness value; and

a counter counting horizontal synchronizing signals applied to said display panel while the brightness control pulse exists, to thereby output a count value as the brightness value input to the operation unit.

3. A display apparatus as claimed in claim 2, further comprising:

a corrected brightness control pulse generator generating a corrected brightness control pulse, a duration of which is proportional to the brightness value stored in said storage unit; and

a read only memory storing a first control signal pattern, that causes said display driver to output sustain pulses to said display panel, and a second control signal pattern that does not cause said display driver to output the sustain pulses to said display panel, and selectively outputting the first and the second control signal patterns to said display driver in response to the corrected brightness control pulse.

4. A display apparatus as claimed in claim 3, wherein said corrected brightness control pulse generator includes:

an edge detecting circuit for detecting a rising edge of the brightness control pulse generated by the brightness control pulse generator;

a second counter counting the horizontal synchronizing signals from the rising edge detected by the edge detecting circuit; and

a comparator comparing a count value, as counted by the second counter, with the brightness value, as stored in said storage unit, and outputting a comparison result as the corrected brightness control pulse.

5. A display apparatus as claimed in claim 1, further comprising:

a power consumption detector detecting power consumption in said display panel and outputting a power consumption value;

a comparator comparing the power consumption value with a reference value and outputting a comparison result;

a controller gradually changing an automatic power control output thereof in response to the comparison result; and

a calculator modifying the brightness value input to the operation unit with the automatic power control output.

6. A display controller for controlling a display driver that drives a display panel, comprising:

a storage unit storing a brightness value, the stored brightness value being used by the display driver; and

an operation unit calculating a difference between a brightness value input to the operation unit and said brightness value stored in said storage unit, and updating said brightness value stored in said storage unit when the calculated difference is larger than a reference value, the updated brightness value being the stored brightness value used by the display driver.

7. A display controller as claimed in claim 6, further comprising:

a brightness control pulse generator periodically generating a brightness control pulse, a duration of which is proportional to an analog brightness value; and

a counter counting horizontal synchronizing signals applied to said display panel while the brightness control pulse exists, to thereby output a count value as the brightness value input to the operation unit.

8. A display controller as claimed in claim 7, further comprising:

a corrected brightness control pulse generator generating a corrected brightness control pulse, a duration of which is proportional to the brightness value stored in said storage unit; and

a read only memory storing a first control signal pattern, that causes the display driver to output effective sustain pulses to the display panel, and a second control signal pattern, that does not cause the display driver to output the sustain pulses to the display panel, and selectively outputting the first and the second control signal patterns to the display driver in response to the corrected brightness control pulse.

9. A display controller as claimed in claim 8, wherein said corrected brightness control pulse generator includes:

an edge detecting circuit for detecting a rising edge of the brightness control pulse generated by the brightness control pulse generator;

a second counter counting the horizontal synchronizing signals from the rising edge detected by the edge detecting circuit; and

a comparator comparing a count value, as counted by the second counter, with the brightness value, as stored in said storage unit, and outputting a comparison result as the corrected brightness control pulse.

10. A display controller as claimed in claim 6, further comprising:

a power consumption detector detecting power consumption in a display panel and outputting a power consumption value,

a comparator comparing the power consumption value with a reference value and outputting a comparison result;

a controller gradually changing an automatic power control output thereof in response to the comparison result; and

a calculator modifying the brightness value input to the operation unit with the automatic power control output.

11. A method of controlling a display driver that drives a display panel comprising the steps of:

storing a brightness value in a memory, the stored brightness value being used by the display driver;

calculating a difference between an input brightness value and the brightness value stored in the memory; and

updating the brightness value stored in the memory when the difference calculated in the calculating step is larger than a reference value, the updated brightness value being the stored brightness value used by the display driver.

12. A method as claimed in claim 11, further comprising the step of:

periodically generating a brightness control pulse, a duration of which is proportional to an analog brightness value; and

counting horizontal synchronizing signals applied to said display panel while the brightness control pulse exists, to thereby obtain a count value as the input brightness value.

13. A method as claimed in claim 12, further comprising the steps of:

generating a corrected brightness control pulse, a duration of which is proportional to the brightness value stored in the memory;

reading from a read-only memory a first control signal pattern, that causes the display driver to output effective sustain pulses to the display panel, and a second control signal pattern, that does not cause the display driver to output the sustain pulses to the display panel, and selectively outputting the first and the second control signal patterns to the display driver in response to the corrected brightness control pulse.

14. A method as claimed in claim 13, wherein said corrected brightness control pulse generating step includes the substeps of:

detecting a rising edge of the brightness control pulse generated in the brightness control pulse generating step;

counting the horizontal synchronizing signals from the rising edge detected in the edge detecting substep; and

comparing a count value counted in the counting substep with the brightness value stored in the memory and outputting a comparison result as the corrected brightness control pulse.

15. A method as claimed in claim 11, further comprising the steps of:

detecting power consumption in the display panel and outputting a power consumption value;

comparing the power consumption value with a reference value, the stored brightness value being used by the display drive;

gradually changing an automatic power control output thereof in response to the comparison result; and

modifying the input brightness value with the changing automatic power control output.

16. A display apparatus comprising:

a display panel including a plurality of display cells;

a detector detecting power consumption in said display panel and outputting a power consumption value;

a controller gradually decreasing a brightness value output thereof, when the power consumption value is larger than a set point, and gradually adjusting the brightness value to a brightness set value, when the power consumption value is smaller than the set point; and

a display driver individually driving the display cells of said display panel in response to the brightness value output so that brightness of the display cells varies according to the brightness value.

17. A display apparatus, as claimed in claim 16, wherein:

said controller periodically compares the power consumption value with the set point, in a first interval, and decrements the brightness value when the power consumption value is larger than the set point, to thereby gradually decrease the brightness value; and

said controller periodically compares the brightness value with the brightness set value, in a second interval, when the power consumption value is smaller than the set point, increments the brightness value when the brightness value is smaller than the brightness set value, and decrements the brightness value when the brightness value is larger than the brightness set value and gradually adjusts the brightness value to the brightness set value.

18. A display apparatus, as claimed in claim 17, wherein the first interval is larger than the second interval.

19. A display apparatus, as claimed in claim 17, wherein the first interval and the second interval are externally variable.

20. A display apparatus, as claimed in claim 16, wherein the set point is varied by being multiplied by the brightness set value.

21. A display apparatus as claimed in claim 16 wherein the power consumption is determined as a product of power voltage and power current,

said detector detecting the power voltage;

and

said controller correcting one of the power consumption value and the set point according to the detected power voltage.

22. A display apparatus, as claimed in claim 16, wherein the brightness value is controlled as a function of the brightness value and the power consumption when the power consumption is smaller than the set point.

23. A display apparatus, as claimed in claim 16, further comprising:

a circuit monitoring the operating time of said display panel; and

said controller changes the set point according to the operating time.

24. A display controller for controlling a display driver that drives a display panel, comprising:

a detector detecting power consumption in the display panel and outputting a power consumption value; and

a controller controlling the brightness value, by gradually decreasing the brightness value when the power consumption value is larger than a set point and gradually adjusting the brightness value to a brightness set value when the power consumption value is smaller than the set point, and outputting the controlled brightness value to the display driver for use thereby.

25. A display controller, as claimed in claim 24, wherein:

the controller periodically compares the power consumption value with the set point in a first interval and decrements the brightness value when the power consumption value is larger than the set point, to thereby gradually decrease the brightness value; and

said controller periodically compares the brightness value with the brightness set value in a second interval when the power consumption value is smaller than the set point, increments the brightness value when the brightness value is smaller than the brightness set value and decrements the brightness value when the brightness value is larger than the brightness set value, gradually adjusting the brightness value to the brightness set value.

26. A display controller, as claimed in claim 25, wherein the first interval is larger than the second interval.

27. A display controller, as claimed in claim 25, wherein the first interval and the second interval are externally variable.

28. A display controller, as claimed in claim 24, wherein the set point is varied by being multiplied by the brightness set value.

29. A display controller as claimed in claim 24, wherein the power consumption is determined as a product of power voltage and power current,

said detector detecting the power voltage;

and

said controller correcting one of the power consumption value and the set point according to the detected power voltage.

30. A display controller, as claimed in claim 24, wherein the brightness value is controlled as a function of the brightness value and the power consumption when the power consumption is smaller than the set point.

31. A display controller, as claimed in claim 24, further comprising:

a circuit monitoring the operating time of the display panel; and

said controller changes the set point according to the operating time.

32. A method of controlling a display driver that drives a display panel, comprising the steps of:

detecting power consumption in said display panel and outputting a power consumption value;

controlling a brightness value in accordance with;

gradually decreasing a brightness value when the power consumption value is larger than a set point, and

gradually adjusting the brightness value to a brightness set value when the power consumption value is smaller than the set point; and

outputting the controlled brightness value to the display driver.

33. A method, as claimed in claim 32, wherein:

said gradually decreasing step includes the substeps of;

a) periodically comparing the power consumption value with the set point, and

b) decrementing the brightness value when it is decided in substep a) that the power consumption value is larger than the set point; and

said gradually adjusting step includes the substeps of;

c) periodically comparing the brightness value with the brightness set value when the power consumption value is smaller than the set point,

d) incrementing the brightness value when it is decided in substep c) that the brightness value is smaller than the brightness set value, and

e) decrementing the brightness value when it is decided in substep c) that the brightness value is larger than the brightness set value.

34. A method, as claimed in claim 33, wherein an interval of comparison in substep a) is larger than an interval of comparison in substep c).

35. A method, as claimed in claim 33, wherein an interval of comparison in substep a) and an interval of comparison of in substep c) are externally variable.

36. A method, as claimed in claim 32, wherein the set point is varied by being multiplied by the brightness set value.

37. A method, as claimed in claim 32, further comprising the steps of:

detecting a power voltage; and

correcting one of the power consumption value and the set point according to the detected power voltage.

38. A method, as claimed in claim 32, wherein the brightness value is controlled as a function of the brightness value and the power consumption when the power consumption is smaller than the set point.

39. A method, as claimed in claim 32, further comprising the steps of:

monitoring operating time of said display panel; and

changing the set point according to the operating time.

40. A display controller for controlling a display driver that drives a display panel comprising:

a detector, connected to a power supply line to the display panel, detecting power consumption by detecting a current flowing through the power supply line and outputting an analog detection signal; and

a microprocessor unit, connected to the display driver, comparing a digital detecting value obtained from the analog detection signal with a reference value, determining a digital brightness value based on the comparison result and outputting the digital brightness value to the display driver, the microprocessor unit gradually decreasing the digital brightness value when the digital detection value is larger than the reference value.

41. A display controller as claimed in claim 40, wherein the power consumption is determined as a product of power voltage and power current,

said detector detecting the power voltage;

and

said microprocessor unit correcting one of the digital detecting value and the reference value according to the detected power voltage.

42. A display controller as claimed in claim 40, wherein the digital brightness value is controlled as a function of the digital brightness value and the digital detecting value when the digital detecting value is smaller than the reference value.

43. A display controller, as claimed in claim 40, further comprising:

a circuit monitoring the operating time of the display panel; and

said microprocessor unit changes the reference value according to the operating time.

44. A display apparatus, comprising:

a display panel including a plurality of display cells;

a detector, connected to a power supply line in turn connected to the display panel, detecting power consumption by detecting a current flowing through the power supply line and outputting an analog detection signal;

a display driver;

a microprocessor unit, connected to the display driver, comparing a digital detecting value obtained from the analog detecting signal with a reference value, determining a digital brightness value based on the comparison result and outputting the digital brightness value to the display driver, the microprocessor unit gradually decreasing the digital brightness value when the digital detection value is larger than the reference value; and

the display driver individually driving the display cells of said display panel in response to the digital brightness value output of the microprocessor unit so that brightness of the display cells varies according to the digital brightness value.

45. A display apparatus as claimed in claim 44, wherein the power consumption is determined as a product of power voltage and power current,

said detector detecting the power voltage;

and

said microprocessor unit correcting one of the digital detecting value and the reference value according to the detected power voltage.

46. A display apparatus as claimed in claim 44, wherein the digital brightness value is controlled as a function of the digital brightness value and the digital detecting value when the digital detecting value is smaller than the reference value.

47. A display apparatus as claimed in claim 44, further comprising:

a circuit monitoring the operating time of the display panel; and

said microprocessor unit changes the reference value according to the operating time.

48. A method of controlling a display driver that drives a display panel, comprising the steps of:

detecting power consumption in said display panel and outputting an analog detection signal;

converting the analog detecting signal to a digital detecting value;

comparing the digital detecting value with a reference value and determining a digital brightness value based on the comparison result, in a microprocessor unit, the microprocessor unit gradually decreasing the digital brightness value when the digital detection value is larger than the reference value; and

outputting the digital brightness value from the microprocessor unit to the display driver.

49. A method as claimed in claim 48, wherein the power consumption is determined as a product of power voltage and power current, further comprising the steps of:

detecting the power voltage; and

correcting one of the digital detecting value and the reference value according to the detected power voltage.

50. A method as claimed in claim 48, wherein the digital brightness value is controlled as a function of the digital brightness value and the digital detecting value when the digital detecting value is smaller than the reference value.

51. A method as claimed in claim 48, further comprising the steps of:

monitoring the operating time of the display panel; and

changing the reference value according to the operating time.