'current 1 Battery chargers 1 Charging (batteries) 1 Conducted electromagnetic interference 1 Efficiency 1 Electromagnetic pulse 1 Electromagnetic wave interference 1 Inductive-resonant 1 Load resistances 1 Multiple switching 1 Performance 1 Radiated electromagnetic interferences 1 Resonant circuits 1 Secondary batteries 1 Signal interference 1 Spread spectra 1 Wireless battery charger 1 efficiency 1 electromagnetic interference 1 inductive-resonant 1 spread spectrum wireless battery charger 1