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

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.

What is claimed is:  
     
       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.  
     
     
       12. A system for charging and discharging a capacitive load comprising: 
       
         a first switch system that opens and closes a circuit between the capacitive load and a substantially constant first voltage potential;  
       
       
         a second switch system that opens and closes a circuit between the capacitive load and an energy storage system that always stores energy substantially only in capacitance, said second switch system causing said energy storage system to electrically disconnect from any conducting circuit when said second switch system is open;  
       
       
         a third switch system that opens and closes a circuit between the capacitive load and a substantially constant second voltage potential, the second voltage potential being different from the first voltage potential; and  
       
       
         a controller communicating with said first, second and third switch systems and causing said switch systems to close and open in a sequential fashion such that the magnitude of the voltage that is delivered to the capacitive load increases and then decreases in a staircase manner;  
       
       
         whereby energy that is delivered to the capacitive load is recovered during decreases in the magnitude of the voltage, and  
       
         whereby the recovered energy is always stored substantially only in capacitance and is substantially re - delivered back to the capacitive load during increases in the magnitude of the voltage, thus effectuating energy conservation.