System and method for power-efficient charging and discharging of a capacitive load from a single source

• US 5,473,526 A
• Filed: 04/22/1994
• Issued: 12/05/1995
• Est. Priority Date: 04/22/1994
• Status: Expired

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Svensson, Lars, Athas, William C., Koller, Jeffrey G.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Krishnan, Aditya
• Application Number:
  US08/231,637
• Time in Patent Office: 592 Days
• Field of Search: 307/109, 307/110, 363/60, 363/59, 363/61
• US Class Current: 363/60
• CPC Class Codes: G05F 1/565 sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor G05F1/563 takes precedence
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A system and method for efficiently charging and discharging a capacitive load from a single voltage source. The system includes a first switch for selectively connecting the voltage source to the load and a second switch for selectively providing a short across the load as may be common in the art. A particularly novel aspect of the invention resides in the provision of plural capacitive elements and a switching mechanism for selectively connecting each of the capacitive elements to the load whereby the load is gradually charged or discharged. In the illustrative embodiment, the switching mechanism includes a set of switches for selectively connecting each of the capacitive elements to the capacitive load and a switch control mechanism for selectively activating the switches.

Claims

1. A system for efficiently charging and discharging a capacitive load from a single voltage source of a first potential consisting of:

a first switch for selectively charging the load;

a second switch for selectively discharging the load;

plural capacitive elements; and

switch means for selectively connecting each of the capacitive elements to the capacitive load to gradually charge or discharge the capacitive load.

2. The invention of claim 1 wherein said switch means includes plural third switches connected between said capacitive elements and said load.

3. The invention of claim 2 wherein said switch means includes means for selectively activating the first, second and third switches.

4. The invention of claim 3 wherein the capacitive load has a first terminal connected to the first switch and a second terminal connected to a source of a second potential.

5. The invention of claim 4 wherein the second switch has a first terminal connected to the first terminal of the load and a second terminal connected to said source of a second potential.

6. The invention of claim 5 wherein each of the third switches has a first terminal connected to the first terminal of the load and a second terminal connected to a first terminal of an associated one of the plural capacitive elements.

7. The invention of claim 6 wherein the means for selectively activating the first, second and third switches includes a finite state machine.

8. The invention of claim 7 wherein the finite state machine is designed to receive a clock signal and an input signal and provide selective activation signals for the first, second and third switches in response thereto.

9. The invention of claim 8 wherein a second terminal of each of the plural capacitive elements is connected to said source of a second potential.

10. The invention of claim 9 wherein each of the capacitive elements has a capacitance which is at least an order of magnitude greater than the capacitance of the load.

11. A method for efficiently charging and discharging a capacitive load from a single voltage source including the steps of:

providing a first switch for selectively connecting the voltage source to the load;

providing a second switch for selectively providing a short across the load;

providing plural capacitive elements;

providing plural third switches for selectively connecting each of the capacitive elements to the capacitive load; and

selectively activating the first, second and third switches to gradually charge or discharge the capacitive load.