Abstract:The paper designs an electromagnetic resonant wireless charger, through the STM32 to control the frequency of the PWM wave input coil, the receiver coil in the alternating magnetic field of the input coil can produce the same frequency alternating current, then after rectifier, regulator, filter output of +5V voltage for lithium battery charging of portable devices. Experiments prove that: high power utilization ratio of the equipment, wireless charging distance, have over voltage, over current protection at the same time, has practical application value.