Power-efficient, pulsed driving of capacitive loads to controllable voltage levels

• US 7,663,618 B2
• Filed: 11/18/2005
• Issued: 02/16/2010
• Est. Priority Date: 09/03/1998
• Status: Expired due to Fees

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Athas, William C., Svensson, Lars G., Lal, Rajat K.
• Primary Examiner(s): Tran; Henry N
• Application Number:
  US11/283,292
• Publication Number:
  US 20060071924A1
• Time in Patent Office: 1,551 Days
• Field of Search: 345211-213, 345/87, 345 98-100, 307/109, 307/110, 307/112, 307125-127, 363/60
• US Class Current: 345/211
• CPC Class Codes: G09G 2330/023 using energy recovery or conservation
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

Power-efficient, pulsed driving of capacitive loads to controllable voltage levels, with particular applicability to LCDs. Energy stored in a portion of the capacitive load is recovered during a recovery phase. Time-varying signals are used to drive the load and to recover the stored energy, thus minimizing power losses, using processes named adiabatic charging and adiabatic discharging.

Claims

1. A circuit for reducing the energy consumed in driving a capacitive load that is being driven to a controllable voltage level, comprising:

one or more first electronic switches connected to the capacitive load for controllably causing the capacitive load to connect to an electronic signal which supplies an adiabatic charging voltage and for charging the capacitive load using the adiabatic charging voltage;

one or more second electronic switches connected to the capacitive load for controllably causing only a portion of the capacitive load to connect to an electronic energy storage system and for discharging only a portion of the load using adiabatic discharging; and

electronic circuitry that generates control signals for causing the first electronic switches to connect the capacitive load to the electronic signal which supplies the adiabatic charging voltage during a first time period and for causing the second electronic switches to connect the capacitive load to the electronic charge storage system during a second time period.

2. The circuit of claim 1 wherein the adiabatic charging and discharging use a ramp signal.

3. The circuit of claim 1 wherein the adiabatic charging and discharging use a staircase signal.

4. The circuit of claim 1 wherein the adiabatic charging and discharging use a half-wave sine pulse.

5. A method for driving one of a plurality of capacitive elements and one or more other capacitance-generating components that are associated with a line other than the capacitive elements, comprising:

electrically connecting each of the plurality of capacitive elements to the line;

storing charge in the one of the plurality of capacitive elements through the line while each of the other of plurality of capacitive elements is electrically connected to the line; and

recovering energy stored in the other capacitance-generating components while maintaining the charge stored in the one of the plurality of capacitive elements.

6. The method of claim 5, further comprising electrically isolating the one of the plurality of capacitive elements from the line prior to recovering the energy stored in the other capacitance-generating components.

7. The method of claim 5, wherein adiabatic charging is used to charge the one of the plurality of capacitive elements along with at least a portion of the capacitance-generating components.

8. The method of claim 7, wherein the adiabatic charging uses a ramp signal.

9. The process of claim 7, wherein the adiabatic charging uses a staircase signal.

10. The process of claim 7, wherein the adiabatic charging uses a half-wave sine pulse.

11. The method of claim 5, wherein adiabatic discharging is used to recover energy from the other capacitance-generating components.

12. The method of claim 11, wherein the adiabatic discharging uses a ramp signal.

13. The process of claim 11, wherein the adiabatic discharging uses a staircase signal.

14. The process of claim 11, wherein the adiabatic discharging uses a half-wave sine pulse.

15. A method for reducing the energy consumed in driving a capacitive load that is being driven to a controllable voltage level, comprising:

controllably causing the capacitive load to connect to a voltage source;

charging the capacitive load using adiabatic charging;

controllably causing only a portion of the capacitive load to connect to a reservoir; and

discharging only a portion of the load using adiabatic discharging.

16. A process for reducing the energy consumed by a display having a plurality of liquid crystal elements arranged in a matrix of rows and columns, the light passed by each liquid crystal element being regulated by a capacitive element associated with the liquid crystal element, each capacitive element having the ability to be selectively charged by the delivery of current through a line associated with the capacitive element, the line also driving one or more other capacitances in the display other than the capacitive elements, each of the plurality of liquid crystal elements being driven to the approximate voltage of a serial video signal, the process comprising:

storing the voltage of the video signal for each capacitive element in a storage device;

applying the stored voltage for each capacitive element to each capacitive element through a first voltage regulator; and

recovering energy from the other capacitances using a second voltage regulator.