CHARGE RECYCLING SYSTEM AND METHOD

• US 20130057481A1
• Filed: 09/07/2011
• Published: 03/07/2013
• Est. Priority Date: 09/07/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Lee, Yongman
• Granted Patent: US 9,201,540 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2330/023 using energy recovery or conservation
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

Techniques for operating a touchscreen display are disclosed herein. In one embodiment, the touchscreen display device includes power regulation circuitry that supplies a first set of voltages to a display panel using high and low supply rails during a display period. During the blanking period following the display period, the high and low supply rails may be adjusted to a second set of voltages that provide for proper operation of touch-sensitive elements in the touchscreen display. Following the end of the blanking period, a portion of charge from the low supply rail is recycled by transferring the charge from the low supply rail back to the high supply rail to bring the high and low supply rails back to the first set of voltages for the next display period.

Claims

1. A method comprising:

providing a first high voltage and a first low voltage to a high power supply rail and a low power supply rail, respectively, of a power regulation device;

using the first high and low voltages to operate a display device during a display period;

at the end of the display period, detecting the start of a blanking period and providing a second high voltage and a second low voltage to the high power supply rail and the low power rail, respectively, wherein the second high voltage is less than the first high voltage and the second low voltage is less than the first low voltage;

using the second high and low voltages to operate the display device during the blanking period; and

at the end of the blanking period, recycling at least a portion of charge from the low power supply rail to the high power supply rail.

2. The method of claim 1, wherein providing the first high voltage and the first low voltage to the high power supply rail and the low power supply rail, respectively, comprises using an internal charge pump of the power regulation device.

3. The method of claim 2, wherein using the internal charge pump comprises controlling a first group of switches of the internal charge pump during a charge period and a second group of switches of the internal charge pump during a subsequent boost period to provide the first high voltage and the first low voltage to the high power supply rail and the low power supply rail, respectively.

4. The method of claim 2, wherein providing the second high voltage comprises discharging the high power supply rail from the first high voltage to the second high voltage and using a first charge pump circuit of an external charge pump of the power regulation device to maintain the high power supply rail at the second high voltage during the blanking period.

5. The method of claim 2, wherein providing the second low voltage comprises using a second charge pump circuit of the external charge pump to decrease the first low voltage to the second low voltage and maintain the low power supply rail at the second low voltage during the blanking period.

6. The method of claim 2, wherein recycling at least the portion of charge from the low power supply rail to the high power supply rail comprises:

(i) controlling a third set of switches of the internal charge pump to cause the portion of charge from the low power supply rail to be transferred to at least one capacitor; and

(ii) controlling a fourth set of switches of the internal charge pump to cause the portion of charge from the at least one capacitor to be transferred to the high power supply rail.

7. The method of claim 6, comprising repeating steps (i) and (ii) until the voltages of the high power supply rail and the low power supply rail are approximately equal to the first high voltage and the first low voltage, respectively.

8. The method of claim 1, wherein using the second high and low voltages to operate the display device during the blanking period comprises using the second high and low voltages to operate touch sensing circuitry of the display device.

9. A power regulation circuit comprising:

a positive supply rail and a negative supply rail configured to provide positive supply voltages and negative supply voltages, respectively, to a display device;

internal charge pump circuitry comprising a plurality of switches configured to provide a first positive voltage to the positive supply rail and a first negative voltage to the negative supply rail during a display interval;

external charge pump circuitry configured to cause the positive supply rail and the negative supply rail to be adjusted to a second positive voltage and a second negative voltage, respectively, during a blanking interval following the display interval; and

control logic configured to control the switches of the internal charge pump, wherein, following the blanking interval, the control logic is configured to control the switches to cause a portion of charge from the negative supply rail to be transferred to the positive supply rail prior to the start of a next display interval.

10. The power regulation circuit of claim 9, wherein the internal charge pump comprises:

a first capacitor arranged between a first node and a second node;

a second capacitor arranged between a third node and a fourth node;

first and second power sources arranged in series between a fifth node and a sixth node, wherein a positive terminal of the first power source is coupled to the fifth node, a negative terminal of the first power source is coupled to a grounding point, a positive terminal of the second power source is coupled to the grounding point, and a negative terminal of the second power source is coupled to the sixth node, wherein the fifth node has a positive voltage corresponding to the first power source and the sixth node has a negative voltage corresponding to the second power source;

a first switch arranged between the first node and the fifth node;

a second switch arranged between the second node and the sixth node;

a third switch arranged between the third node and the sixth node;

a fourth switch arranged between the fourth node and the fifth node;

a fifth switch configured to connect the first node to the positive supply rail and to a third capacitor when the fifth switch is in a closed position;

a sixth switch arranged between the second node and the fifth node;

a seventh switch configured to connect the third node to the negative supply rail and to a fourth capacitor when the seventh switch is in a closed position;

an eighth switch arranged between the fourth node and the sixth node;

a ninth switch arranged between the second node and the negative supply rail; and

a tenth switch arranged between the fourth node and the positive supply rail.

11. The power regulation circuit of claim 10, wherein the fifth and sixth switches are controllable using a common first control signal provided by the control logic, wherein the seventh and eighth switches are controllable using a common second control signal provided by the control logic, and wherein the eighth switch is also independently controllable using a third control signal that is separate from the second control signal.

12. The power regulation circuit of claim 10, wherein, to provide the first positive voltage to the positive supply rail and the first negative voltage to the negative supply rail during the display interval, the control logic is configured to:

during a charge period, control each of the first switch, second switch, third switch, and fourth switch to a closed position, such that the fifth node is connected to both the first node and the fourth node and the sixth node is connected to both the second node and the third node, wherein the first capacitor is charged such that the difference between the first node and the second node is equal to the difference between the positive voltage at the fifth node and the negative voltage at the sixth node, and wherein the second capacitor is charged such that the difference between the third node and the fourth node is equal to the difference between the negative voltage at the sixth node and the positive voltage at the fifth node; and

during a boost period following the charge period, control each of the first switch, second switch, third switch, and fourth switch to an open position and each of the fifth switch, sixth switch, seventh switch, and eighth switch to a closed position, such that first node is connected to the positive supply rail and the third capacitor, the second node is connected to the fifth node, the third node is connected to the negative supply rail and the fourth capacitor, and the fourth node is connected to the sixth node, and wherein the first positive voltage provided to the positive supply rail is equal to twice the positive voltage at the fifth node minus the negative voltage at the sixth node and the first negative voltage provided to the negative supply rail is equal to twice the negative voltage at the sixth node minus the positive voltage at the fifth node.

13. The power regulation circuit of claim 12, wherein, to adjust the first positive and negative voltages to the second positive and negative voltages, respectively, during the blanking interval, the control logic is configured to:

discharge the positive supply rail from the first positive voltage to the second positive voltage and, when the positive supply rail equals the second positive voltage, use a first charge pump circuit of the external charge pump to maintain the positive supply rail at the second positive voltage for the remainder of the blanking interval;

use a second charge pump circuit of the external charge pump to pump down the negative supply rail until the voltage of the negative supply rail equals the second negative voltage and to maintain the negative supply rail at the second negative voltage for the remainder of the blanking interval.

14. The power regulation circuit of claim 13, wherein the control logic is configured to cause the portion of charge from the negative supply rail to be transferred to the positive supply rail prior to the start of the next display interval by:

detecting the end of the blanking interval; and

after detecting the end of the blanking interval, controlling the switches of the internal charge pump circuitry by;

controlling each of the first switch, fourth switch, seventh switch, and ninth switch into a closed position to cause the portion of charge to be transferred to the first and second capacitors;

controlling each of the first switch, fourth switch, seventh switch, and ninth switch into an open position; and

controlling each of the third switch, fifth switch, sixth switch, and tenth switch into a closed position to cause the portion of charge stored in the first and second capacitors to be transferred to the positive supply rail.

15. A display device comprising:

a liquid crystal display panel, wherein the display panel comprises an array of display pixels and touch-sensitive elements;

touch-sensing circuitry configured to control the touch-sensitive elements;

display driver circuitry configured to a drive a frame of image data to the display pixels of the display panel during a display period of operation;

power circuitry configured to;

supply a first positive voltage and a first negative voltage to the display device during the display period using a positive supply rail and a negative supply rail, respectively;

supply a second positive voltage and a second negative voltage to the display device during a blanking period of operation following the display period;

supply the first positive voltage and the first positive voltage to the display device during another subsequent display period by transferring charge from the negative supply rail to the positive supply rail.

16. The display device of claim 15, wherein the first positive and negative voltages are used to operate the display panel during the display period and the second positive and negative voltages are used to operate the touch-sensing circuitry during the blanking period.

17. The display device of claim 15, wherein, following the blanking period, charge is transferred from the negative supply rail to the positive supply rail until the positive and negative supply rails reach at least approximately the first positive and negative voltages, respectively.

18. The display device of claim 15, wherein the second positive voltage is less than the first positive voltage, and wherein the second negative voltage is less than the first negative voltage.

19. The display device of claim 15, wherein the touch-sensing circuitry and the touch-sensitive elements are configured to provide at least one of a capacitive touchscreen display or a resistive touchscreen display.

20. An electronic device comprising:

one or more input structures;

a storage structure encoding one or more executable routines;

a processor capable of receiving inputs from the one or more input structures and of executing the one or more executable routines; and

a touchscreen display configured to display an output of the processor, wherein the display device comprises;

a liquid crystal display (LCD) panel comprising a plurality of pixels arranged in rows and columns;

touch-sensing circuitry configured to control touch-sensitive elements that receive touch inputs from a user; and

power regulation circuitry comprising;

a high voltage supply rail and a low voltage supply rail configured to provide high supply voltages and low supply voltages, respectively, to the display panel;

internal charge pump logic configured to provide a high display period voltage to the high voltage supply rail and a low display period voltage to the low voltage supply rail when the display panel is operating in a first display period;

external charge pump logic configured to provide a high blanking period voltage to the high voltage supply rail and a low blanking period voltage to the low voltage supply rail when the display panel is operating in a blanking period following the first display period; and

control logic configured to, after the blanking period and prior to a second display period, return the high voltage supply rail and the low voltage supply rail to the high and low display period voltages, respectively, by transferring a portion of charge from the low voltage supply rail to the high voltage supply rail.

21. The display device of claim 20, wherein the voltage difference between the high and low display period voltages is equal to the voltage difference between the high and low blanking period voltages.

22. The display device of claim 20, wherein the power regulation circuitry is part of a display driver configured to send image data to the display panel.

23. The display device of claim 20, wherein the high voltage supply rail and the low voltage supply are returned to the high and low display period voltages, respectively, in at least two line times of the display panel.

24. The electronic device of claim 20, comprising at least one of a laptop computer, a desktop computer, a portable media player, a mobile phone, a tablet computing device, or some combination thereof.

25. A method comprising:

providing a first voltage to a first supply rail and a second voltage to a second supply rail during a first time interval;

providing a third voltage to the first supply rail and a fourth voltage to the second supply rail during a second time interval subsequent to the first time interval; and

providing the first voltage to the first supply rail and the second voltage to the second supply rail during a third time interval by transferring charge from the second supply rail to the first supply rail to achieve the first and second voltages.

26. The method of claim 25, wherein providing the third voltage to the first supply rail comprises discharging the first supply rail from the first voltage to the third voltage.

27. The method of claim 26, wherein providing the fourth voltage to the second supply rail comprises using a charge pump circuit to pump the second supply rail from the second voltage to the fourth voltage.

28. The method of claim 26, wherein the first and third voltages are positive voltages and the second and fourth voltages are negative voltages.