Abstract：Currently，the optimal modulation strategies for SS resonant networks under different operating

conditions have not been fully explored. Therefore，the optimal modulation strategy of SS resonant network was

investigated in low-power situations to improve the transmission efficiency and charging stability of the wireless

charging system，and to reduce the switching loss. Firstly，the mathematical model of SS resonant network was

established，its transmission characteristics were analyzed，the relationship between its output current and each

parameter was derived，and the current gain curves under different modulation strategies were further analyzed，and the irregularity of its output current gain under FM modulation was identified. Then，the effects of phase-shift

modulation and FM modulation on the working state of the system were compared through experiments，and the

optimal modulation strategies under different working conditions were derived. Finally，the correctness and validity

of the analysis of the optimal modulation strategy for wireless charging were verified through experiments.

      Key words：wireless charging；SS resonant network；electromagnetic coupling；FMmodulation；full-bridge phaseshift modulation