Provided are a charging system, charging method, and device, said charging system comprising a battery; a first rectifier, configured to output a first voltage with a first pulsating waveform; a switch unit, configured to modulate the first voltage; a transformer, configured to output a second voltage with a second pulsating waveform; a second rectifier, configured to output a third voltage with a third pulsating waveform, and the third voltage is configured to be applied to the battery charge the battery; a first current sampling circuit, configured to sample current to obtain a current sampling value; and a control unit configured to output the control signal to the switch unit, adjust the amplification factor of the operational amplifier, and adjust a duty ratio of the control signal according to the current sampling value, such that the third voltage meets a charging requirement of the battery.