The invention provides a charging protection method and device and a control device that are applied to a direct-current/direct-current converter. The charging protection method comprises: a chargingcurrent and a ground voltage of a direct-current/direct-current converter during a charging process are obtained; and according to the ground voltage and the charging current, the direct-current/direct-current converter is controlled to carry out charging. According to the invention, the charging current and the ground voltage of the direct-current/direct-current converter are obtained and the direct-current/direct-current converter is controlled to carry out charging flexibly based on the ground voltage and the charging current. Therefore, a phenomenon of flowing back of a charging current from a common-ground electrical device to a negative electrode of a direct-current/direct-current converter during a charging process is avoided.