Digital driving circuits, methods and systems for liquid crystal display devices

• US 8,704,818 B2
• Filed: 01/31/2013
• Issued: 04/22/2014
• Est. Priority Date: 01/14/2010
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Wright, David G., Van Ess, David, Keeser, Christopher C., Murphy, Robert L.
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): Chow, Yuk
• Application Number:
  US13/755,709
• Publication Number:
  US 20130141416A1
• Time in Patent Office: 446 Days
• Field of Search: 345/212, 345/34, 345/50, 340/324
• US Class Current: 345/212
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 3/04 for presentation of a single character by selection from a plurality of characters, or by composing the character by combination of individual elements, e.g. segments using a combination of such display devices for composing words, rows or the like, in a frame with fixed character positions
• CPC Class Codes: G09G 3/18 using liquid crystals
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A method may include generating display driver signals that vary between only two levels and applying the display driver signals to opposing electrodes of a display segment within a display device. The method varies a correlation between the display driver signals to select or de-select the display segment based on an average voltage magnitude across the display segment over a time period. The display segment is activated when the average voltage magnitude exceeds a threshold value.

Claims

1. A method comprising:

generating display driver signals that vary between only two levels;

applying the display driver signals to opposing electrodes of a display element within a display device, wherein the display driver signals comprise common drive signals and segment drive signals; and

in a first mode,

varying a correlation between the common drive signals and the segment drive signals to select or de-select the display element based on an average voltage magnitude across the display element over a time period, wherein the display element is activated in the first mode when the average voltage magnitude exceeds a threshold value, wherein the average voltage magnitude exceeds the threshold value when a respective one of the common drive signals and the corresponding one of the segment drive signals are correlated and the average voltage magnitude does not exceed the threshold value when the respective one of the common drive signals and the corresponding one of the segment drive signals are not correlated; and

in a second mode,

varying a pulse density of the display driver signals applied to the opposing electrodes to select or de-select the display element; and

filtering the display driver signals applied to the opposing electrodes using electrical characteristics of at least a portion of the display device in the second mode to provide voltage levels at the display element to vary according to pulse density, wherein the display element is activated in the second mode when a second average voltage magnitude exceeds a second threshold value.

2. The method of claim 1, wherein the varying the correlation between display driver signals comprises generating a plurality of common driver signals that each comprises frames of N timeslots, comprising one selection time slot and N-1 de-selection timeslots, the selection timeslot being different for each common driver signal.

3. The method of claim 2, wherein the varying the correlation between display driver signals comprises generating at least one segment driver signal comprising frames of N timeslots corresponding to the common driver signals, wherein the segment is activated when the average voltage magnitude between corresponding common and segment driver signals exceeds a voltage threshold in a timeslot.

4. The method of claim 2, further comprising:

repeating each common driver signal every frame; and

generating at least one segment driver signal comprising frames of N timeslots corresponding to the common driver signal, the segment driver signal varying a correlation to at least one common driver signals in response to display data.

5. A method comprising:

generating display driver signals that vary between only two levels;

applying the display driver signals to electrodes of display elements within a display device, wherein the display driver signals comprise common drive signals and segment drive signals;

in a a high power mode,

varying a pulse density of the display driver signals; and

filtering the display driver signals using electrical characteristics of at least a portion of the display device to provide voltage levels across the display elements that vary according to pulse density, wherein the display element is activated when the average voltage magnitude across the display element over a time period exceeds a first threshold value;

in a low power mode,

varying a correlation between the common drive signals and the segment drive signals to select or de-select the display element based on a second average voltage magnitude across the display element over a second time period in the low power mode, wherein the display element is activated when the second average voltage magnitude exceeds a second threshold value, wherein the second average voltage magnitude exceeds the second threshold value when a respective one of the common drive signals and the corresponding one of the segment drive signals are correlated and the second average voltage magnitude does not exceed the second threshold value when the respective one of the common drive signals and the corresponding one of the segment drive signals are not correlated; and

switching between the high power mode and the low power mode in response to a mode indication.

6. The method of claim 5, wherein the filtering the display driver signals comprises filtering with a frequency filter that comprises the portion of the display device, wherein the display device is a liquid crystal display device.

7. The method of claim 5, further comprising:

generating a plurality of time division multiplexed common driver signals and segment driver signals that vary substantially between the two levels;

in the low power mode, activating display elements by varying a correlation between common and segment driver signals connected to such display elements; and

in the high power mode, activating display elements by at least varying voltage levels of a common driver signal as received by the display elements.

8. The method of claim 7, further comprising:

in the low power mode,

generating common driver signals that vary according to a predetermined sequence; and

generating segment driver signals that selectively correlates with at least one common driver signal in response to display data to exceed a minimum average voltage over a time period, wherein

a display element is activated or not activated depending upon whether a voltage exceeds exceed the minimum average voltage over the time period.

9. The method of claim 8, wherein the common and segment driver signals comprises frames, each comprising a plurality of timeslots, and the time period comprises one of the time slots.

10. The method of claim 7, further comprising:

in the high power mode,

generating common driver signals comprising a variable pulse density, and

filtering the variable pulse density signals to generate the varying voltage levels received by the display elements.

11. The method of claim 10, wherein the filtering the variable pulse density signals comprises forming a frequency filter that comprises the portion of the display device, wherein the display device is a liquid crystal display.

12. The method of claim 7, further comprising further varying a pulse density of at least the common driver signals or the segment driver signals in response to an intensity value.

13. A system comprising:

a plurality of programmable digital blocks to be coupled to display element of a display device, wherein the plurality of programmable digital blocks are configured into the following circuits;

a first signal generator circuit that generates control signals that vary between only two levels; and

a selection driver circuit coupled to the first signal generator circuit, wherein the selection driver circuit is to apply the control signals to opposing electrodes of the display element, wherein the control signals comprise common drive signals and segment drive signals, wherein the selection driver circuit comprises a first mode that varies a correlation between the common drive signals and the segment drive signals to select or de-select the display element based on an average voltage magnitude across the display element over a time period, wherein the display element is activated in the first mode when the average voltage magnitude exceeds a threshold value, wherein the average voltage magnitude exceeds the threshold value when a respective one of the common drive signals and the corresponding one of the segment drive signals are correlated and the average voltage magnitude does not exceed the threshold value when the respective one of the common drive signals and the corresponding one of the segment drive signals are not correlated, wherein the selection driver circuit comprises a second mode that varies a pulse density of the control signals applied to the opposing electrodes to select or de-select the display element and filters the control signals applied to the opposing electrodes using electrical characteristics of at least a portion of the display device to provide voltage levels at the display element to vary according to pulse density, wherein the display element is activated in the second mode when a second average voltage magnitude exceeds a second threshold value.

14. The system of claim 13, wherein the selection driver circuit comprises:

a common section that time division multiplexes the control signals to a plurality of common connection points in a predetermined sequence; and

a segment section that time division multiplexes the control signals to a plurality of common connection points in response to at least display data.

15. The system of claim 13, wherein the plurality of programmable digital blocks are further configured into the following circuits:

a second signal generator circuit that generates a plurality of intensity signals that substantially do not correlate with the control signals; and

an intensity varying circuit that logically combines the intensity signals with signals output from the selection driver circuit.

16. The system of claim 13, further comprising

a display structure coupled to the common and segment connection points comprising an inherent capacitance that forms at least a portion of a frequency filter, the predetermined frequency being outside a passband of the frequency filter.

17. The system of claim 13, wherein the display device is a liquid crystal display coupled to the common and segment connection points.