A conversion control circuit controls plural stackable sub-converters which are coupled in parallel to generate an output power to a load. The conversion control circuit includes a current sharing terminal and a current sharing circuit. A current sharing signal is connected, in parallel, to the current sharing terminals. The current sharing circuit includes: configuration (1): the current sharing signal is generated only according to an inductor current corresponding to one of plural inductors of the plural stackable sub-converters; or configuration (2): the current sharing signal is generated according to plural inductor currents corresponding to plural inductors of plural activated phases of the plural stackable sub-converters, wherein a ratio of a portion of the current sharing signal generated by a master control circuit to a portion generated by one of the slave control circuits is k which relates to a difference between a total phase number and an activated phase number.