constant current (Itx) output in response to the detected number of engaged resonator coils.
18. The method of claim 17, further comprising synchronizing the plurality of parallel circuits to an oscillator to provide in-phase combination of AC input voltage.
19. The method of claim 18, further comprising sampling the AC input and the substantially constant voltage (Vtx) and comparing the samplings to one or more threshold values.
20. The method of claim 14, further comprising measuring reactance shift as a function of at least one of substantially constant current, the resonator input voltage and the phase between the current and voltage.
21. A non-transitory machine-readable storage medium storing instructions which, when executed, causes wireless charging of an external device by performing a method comprising:
amplifying an alternating current (AC) input voltage to provide an first voltage;
conditioning the first voltage to provide a substantially constant output voltage (Vtx);
converting the substantially constant voltage (Vtx) to a substantially constant current (Itx) output;
tuning the substantially constant current (Itx) output to electromagnetically engaging and wirelessly charging one or more resonator coils.
22. The non-transitory machine-readable storage medium of claim 21, further comprising phase-shifting shifts the substantially constant voltage output (Vtx) to provide a phase-shifted substantially constant current output (Itx).
23. The non-transitory machine-readable storage medium of claim 22, further comprising phase-shifting the substantially constant voltage (Vtx) by about 90° .
24. The non-transitory machine-readable storage medium of claim 21, further comprising detecting a number of electromagnetically engaged resonator coils and selectively engaging a number of parallel circuits to condition the first voltage to provide an amplified substantially constant output voltage (Vtx) and to convert the substantially constant voltage (Vtx) to the substantially constant current (Itx) output in response to the detected number of engaged resonator coils.
25. The non-transitory machine-readable storage medium of claim 24, further comprising synchronizing the plurality of parallel circuits to an oscillator to provide in-phase combination of AC input voltage.