Wireless power transfer using multiple coil arrays

Abstract

In one embodiment of a wireless power transmitter, two coils are magnetically coupled together by placing both coils on a magnetic layer. A power circuit generates an AC signal of a defined voltage magnitude that causes a current to flow through the first coil, which generates a magnetic field having a first polarity. The second coil is coupled to the first coil. Current flows through the second coil and generates a magnetic field having a second polarity that is opposite from the first polarity. Because the magnetic field generated by each coil has a different polarity, the magnetic fields attract and form a strong magnetic field that flows from the first coil to the second coil. The strong magnetic field can transfer greater amounts of power to a receiver in comparison to coil configurations that emit magnetic fields in the same direction that repel one another.

1 . A wireless power device comprising:
 a first coil configured to receive a time-varying current that flows in the first coil in a first direction; and   a second coil coupled to the first coil in such a way that the time-varying current flows in the second coil in a second direction, wherein the first direction is opposite from the second direction, and the first coil is configured to magnetically couple with the second coil.   
     
     
         2 . The wireless power device of  claim 1 , further comprising a magnetic layer configured to magnetically couple the first coil with the second coil. 
     
     
         3 . The wireless power device of  claim 1 , wherein the first coil is configured to magnetically couple with the second coil by being located in close physical proximity to the second coil. 
     
     
         4 . The wireless power device of  claim 1 , wherein the first coil is coupled in series with the second coil. 
     
     
         5 . The wireless power device of  claim 1 , wherein the first coil is coupled in parallel with the second coil. 
     
     
         6 . The wireless power device of  claim 1 , wherein the first coil and the second coil have an equal number of turns, substantially the same shape, and substantially the same area. 
     
     
         7 . The wireless power device of  claim 1 , further comprising a power source configured to generate the time-varying current, wherein the first coil is configured to receive the time-varying current from the power source. 
     
     
         8 . The wireless power device of  claim 7 , further comprising a capacitor coupled between the power source and the first coil. 
     
     
         9 . The wireless power device of  claim 1 , further comprising a receive circuit coupled to the first coil and the second coil, wherein the receive circuit is configured to generate a voltage from the time-varying current that flows in the first coil and the second coil. 
     
     
         10 . The wireless power device of  claim 2 , further comprising:
 a third coil configured to receive a second time-varying current that flows in the third coil in a third direction;   a fourth coil coupled to the third coil in such a way that the second time-varying current flows in the fourth coil in a fourth direction, wherein the third direction is opposite from the fourth direction;   a second magnetic layer configured to magnetically couple the third coil and the fourth coil; and   an air gap separating the first magnetic layer from the second magnetic layer.   
     
     
         11 . The wireless power device of  claim 10 , wherein the third coil is coupled in series with the fourth coil. 
     
     
         12 . The wireless power device of  claim 10 , wherein the third coil is coupled in parallel with the fourth coil. 
     
     
         13 . The wireless power device of  claim 10 , wherein the third coil and the fourth coil have an equal number of turns, substantially the same shape, and substantially the same area. 
     
     
         14 . The wireless power device of  claim 10 , further comprising a power source configured to generate the second time-varying current and the third coil is configured to receive the second time-varying current from the power source. 
     
     
         15 . The wireless power device of  claim 10 , wherein the third coil is coupled to the second coil in such a way that the first time-varying current that flows in the second coil is the same direction as the second time-varying current that flows in the third coil. 
     
     
         16 . A wireless power device comprising:
 a power source configured to generate a first time-varying current; a first coil configured to receive the first time-varying current from the power source, wherein the first time-varying current flows in the first coil in a first direction;   a second coil coupled to the first coil in such a way that the first time-varying current flows in the second coil in a second direction, wherein the first direction is opposite from the second direction;   a third coil configured to receive a second time-varying current, wherein the time varying current flows in the third coil in a third direction and the third direction is opposite from the second direction;   a fourth coil coupled to the third coil in such a way that the second time-varying current flows in the fourth coil in a fourth direction, wherein the fourth direction is opposite from the third direction and the first direction;   a magnetic layer configured to magnetically couple the first coil and the second coil, and to magnetically couple the third coil and the fourth coil; and   an air gap in the magnetic layer, wherein the air gap separates the first coil from the third coil and the second coil from the fourth coil.   
     
     
         17 . The wireless power device of  claim 16 , wherein the first coil is coupled in series with the second coil. 
     
     
         18 . The wireless power device of  claim 16 , wherein the first coil is coupled in parallel with the second coil. 
     
     
         19 . The wireless power device of  claim 16 , wherein the third coil is coupled in series with the fourth coil. 
     
     
         20 . The wireless power device of  claim 16 , wherein the third coil is coupled in parallel with the fourth coil. 
     
     
         21 - 34 . (canceled)