Optimal load selection method and device under offset working condition of wireless charging system

The invention discloses an optimal load selection method and device for a wireless charging system under an offset working condition, and the method comprises the steps: switching on a switch 1, and reading a primary voltage U1 and a primary current I1; disconnecting the switch 1, and calculating mutual inductance M according to the mutual inductance test resistor R0; if M is smaller than the set maximum offset mutual inductance M0, the switch 2 is closed, and the optimal load RLopt is obtained according to M; setting an initial duty ratio D0 of the MOSFET module; calculating the equivalent resistance RL of the battery according to U1, I1 and D0; and calculating the optimal duty ratio Dopt under the current offset position according to the RLopt and the RL, and setting the duty ratio of the MOSFET module as Dopt until the charging is completed. The beneficial effects of the application are that the M is measured through the electrical quantity to obtain the RLopt, and the RL is monitored through the electrica