Wireless Power Transfer Method and System

Abstract

A new resonance-based wireless power transfer system is disclosed. The new resonance-based wireless power transfer system includes a power transmitter and a power receiver. The power transmitter and the power receiver are both oscillator-based circuits, but unlike prior systems, their resonant frequencies are different. The difference between the transmitter's resonant frequency and the receiver's resonant frequency is set between a lower bound and an upper bound to ensure that the new resonance-based wireless power transfer system will have only one oscillation frequency while maintaining high power transfer efficiency over varied distances.

We claim: 
     
         1 . A wireless power transfer system, comprising:
 a power transmitter manufactured to operate only at a first resonant frequency f 1 ; and   a power receiver manufactured to operate only at a second resonant frequency f 2  different from the first resonant frequency f 1 , wherein the power transmitter and the power receiver oscillate together at only one oscillating frequency f o .   
     
     
         2 . The wireless power transfer system of  claim 1 , wherein the power transmitter comprises a first capacitor and a first coil and the power receiver comprises a second capacitor and a second coil. 
     
     
         3 . The wireless power transfer system of  claim 2 , wherein the difference between the first resonant frequency f 1  and the second resonant frequency f 2  is given by Δf, wherein the frequency difference Δf is set such that 
       
         
           
             
               
                 
                   
                     1 
                     4 
                   
                    
                   
                     k 
                     2 
                   
                    
                   
                     Q 
                     2 
                     2 
                   
                 
                 - 
                 
                   1 
                   
                     2 
                      
                     
                         
                     
                      
                     
                       Q 
                       2 
                       2 
                     
                   
                 
               
               < 
               
                 
                   Δ 
                    
                   
                       
                   
                    
                   f 
                 
                 f 
               
               < 
               
                 
                   
                     k 
                     2 
                   
                    
                   
                     Q 
                     2 
                     2 
                   
                 
                 2 
               
             
           
         
       
       where k is a mutual coupling coefficient between the first coil and the second coil, Q 2  is the quality factor of the power receiver, and f=½(f 1 +f 2 ). 
     
     
         4 . The wireless power transfer system of  claim 3 , wherein the second capacitor and the second coil form a parallel LC circuit, and wherein the power receiver further comprises a rectifier and a DC to DC converter. 
     
     
         5 . The wireless power transfer system of  claim 3 , wherein the second capacitor and the second coil form a serial LC circuit, and the power receiver further comprises an AC to DC converter. 
     
     
         6 . The wireless power transfer system of  claim 3 , wherein the second capacitor and the second coil form a serial LC circuit, and the power receiver further comprises a voltage multiplier having a plurality of diodes and a plurality of capacitors. 
     
     
         7 . The wireless power transfer system of  claim 3 , wherein the power transmitter further comprises a power source. 
     
     
         8 . The wireless power transfer system of  claim 3 , wherein the ratio between the first coil's area and the second coil's area is between 2 and 4. 
     
     
         9 . The wireless power transfer system of  claim 8 , wherein the first coil is of a rectangle, square, circle, or hexagon shape and the second coil is of a rectangle, square, circle, or hexagon shape. 
     
     
         10 . The wireless power transfer system of  claim 1 , further comprising a second power receiver manufactured to operate only at a third resonant frequency f 3  different from the first resonant frequency f 1 , wherein the power transmitter and the second power receiver oscillate together at only one oscillating frequency f o1 . 
     
     
         11 . The wireless power transfer system of  claim 1 , further comprising a second power transmitter manufactured to operate only at a third resonant frequency f 3  different from the second resonant frequency f 2 , wherein the second power transmitter and the power receiver oscillate together at only one oscillating frequency f o2 .