Abstract：Wireless power transfer（WPT）load voltage，current and other state information need to be sent to

the original side for closed-loop control and monitoring processing，the secondary side to the original side of the

communication is very important. Firstly，the topology and working principle of capacitive modulated WPT system

were introduced. With or without capacitance modulation，the system topology was changed，the original and

secondary side topologies were series/series（S/S）structure when unmodulated，and the original and secondary side topologies were series/series-paralle（l S/SP）structure during modulation. The switching of the modulation capacitor formed two states to transmit communication information，and the change of the state can be reflected in the primary current. Secondly，the amplitude-shift keying（ASK）demodulation circuit was used to process the primary current to restore the communication signal. In order to improve the demodulation accuracy and anti-interference ability，the ASK demodulation circuit was improved. Finally，the effectiveness of the scheme was verified by simulation and experiments，and the experimental results show that the system can accurately complete

communication from the secondary side to the primary side at a power of 100 W and a communication frequency of

2~5 kHz.

      Key words：wireless power transfer（WPT）；carrier communication；modulation capacitance；amplitude-shift

keying（ASK）demodulation