Active liquid crystal display drivers and duty cycle operation

• US 8,686,985 B2
• Filed: 12/27/2007
• Issued: 04/01/2014
• Est. Priority Date: 04/18/2007
• Status: Active Grant

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Snyder, Warren, Wright, David, Sullam, Bert, Williams, Timothy, Kutz, Harold
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): ZUBAJLO, JENNIFER L
• Application Number:
  US11/965,520
• Publication Number:
  US 20080259070A1
• Time in Patent Office: 2,287 Days
• Field of Search: 345/204, 345/211, 345/212
• US Class Current: 345/212
• CPC Class Codes: H03K 17/687 the devices being field-effect transistors
• CPC Class Codes: H03K 19/0016 by using a control or a clock signal, e.g. in order to apply power supply
• CPC Class Codes: H03K 19/00369 Modifications for compensating variations of temperature, supply voltage or other physical parameters

Abstract

A liquid crystal display (LCD) driving system includes a reference voltage generator to generate a plurality of reference voltages. The LCD driving system also includes a plurality of drive buffers to generate drive voltages according to at least one of the reference voltages, and to drive at least a portion of a liquid crystal display to present data according to the drive voltages.

Claims

1. A device, comprising:

a reference voltage generator configured to generate a plurality of reference voltages;

a plurality of drive buffers configured to generate drive voltages according to at least one of the reference voltages, and to drive at least a portion of a display to present data according to the drive voltages, wherein at least one of the drive buffers comprises;

a switch configured to receive one or more of the reference voltages from the reference voltage generator and to select at least one of the reference voltages; and

an active driver configured to generate at least one of the drive voltages by actively driving the at least one of the drive voltages at an output of the active driver toward the at least one of the reference voltages selected by the switch;

wherein the active driver is configured to (1) initially adjust the at least one of the drive voltages to a value within a voltage window, wherein the voltage window is a voltage range including the at least one of the reference voltages selected by the switch, and (2) set the at least one drive voltage to substantially correspond to the selected reference voltage subsequent to initially adjusting the at least one drive voltage to the value within the voltage window.

2. The device of claim 1, wherein the active driver includes a high drive buffer configured to initially adjust the at least one of the drive voltages towards the selected reference voltage.

3. The device of claim 2, wherein the high drive buffer is configured to adjust the at least one of the drive voltages to the value within the voltage window.

4. The device of claim 2, where the active driver includes a low drive buffer configured to adjust the drive voltage to substantially correspond to the selected reference voltage subsequent to the high drive buffer initially adjusting the drive voltage.

5. The device of claim 4, wherein the active driver is configured to operate in a no-drive mode in response to the low drive buffer adjusting the load voltage to substantially correspond to the selected reference voltage.

6. The device of claim 5, where the reference voltage generator is turned off when the active driver operates in the no-drive mode.

7. The device of claim 1, wherein the display is a passive liquid crystal display.

8. A method, comprising:

selecting at least one of a plurality of reference voltages received from a reference voltage generator;

generating one or more load voltages by actively driving the one or more load voltages toward the selected reference voltage, wherein actively driving the one or more load voltages includes (1) initially adjusting at least one load voltage of the load voltages to a value within a voltage window, wherein the voltage window is a voltage range including the selected reference voltage, and (2) setting the at least one load voltage to substantially correspond to the selected reference voltage subsequent to initially adjusting the at least one load voltage to the value within the voltage window; and

driving at least a portion of a liquid crystal display to present data according to the load voltages.

9. The method of claim 8 where generating one or more load voltages according to the selected reference voltage includes initially adjusting the load voltage associated with the portion of the liquid crystal display towards the selected reference voltage while in a high drive mode.

10. The method of claim 9 where generating one or more load voltages according to the selected reference voltage includes switching from the high drive mode to a low drive mode to adjust the load voltage to substantially correspond to the selected reference voltage.

11. The method of claim 10, wherein the switching from the high drive mode to the low drive mode occurs when a voltage level associated with the load voltage is within the voltage window, wherein the voltage window is defined according to a preset offset value.

12. The method of claim 10 includes ceasing to drive the liquid crystal display after the load voltage substantially corresponds to the selected reference voltage during the low drive mode.

13. The method of claim 12 further including directing the reference voltage generator to cease generating the reference voltages after the load voltage substantially corresponds to the selected reference voltage.

14. A system, comprising:

a drive buffer configured to select at least one of a plurality of reference voltages received from a reference voltage generator;

an active driver configured to generate one or more load voltages by actively driving the one or more load voltages toward the selected reference voltage, wherein the active driver is configured to operate in a no-drive mode responsive to the one or more load voltages having been adjusted to substantially correspond to the selected reference voltage, and wherein in the no-drive mode generation of the plurality of reference voltages is ceased after the one or more load voltages have been adjusted to substantially correspond to the selected reference voltage; and

a display driver configured to drive at least a portion of a display to present data according to the load voltages.

15. The system of claim 14, wherein the active driver includes a high drive buffer configured to initially adjust a load voltage associated with the portion of the display towards the selected reference voltage while in a high drive mode.

16. The system of claim 15, wherein the active driver includes a low drive buffer configured to adjust the load voltage to substantially correspond to the selected reference voltage in a low drive mode.

17. The system of claim 16, wherein the active driver switches from the high drive mode to the low drive when a voltage level associated with the load voltage is within a voltage window, the voltage window having a range of voltage levels centered around the selected reference voltage and defined according to a preset offset value.

18. The system of claim 16 further comprising a display controller configured to control the operation of the reference voltage generator.

19. The system of claim 18, wherein the display controller is configured to direct the reference voltage generator to cease generating the reference voltages after the load voltage substantially corresponds to the selected reference voltage.