Control method, system and controller of power conversion circuit

The invention relates to the technical field of power supply control, in particular to a control method and system of a power supply conversion circuit and a controller, and the method is suitable for the power supply conversion circuit. The power conversion circuit comprises a pre-stage LLC circuit and a post-stage BUCK circuit; the method comprises the following steps: determining the gain of the power conversion circuit according to the working scene of the power conversion circuit, and recording the gain as the total gain of the power conversion circuit; selecting a working gear of the power conversion circuit from a plurality of set gears according to the total gain of the power conversion circuit and the load condition of the power conversion circuit; the plurality of gears are set according to the open-closed loop working state of the preceding-stage LLC circuit, the gain of the preceding-stage LLC circuit, the open-closed loop working state of the backward-stage BUCK circuit and the value of the duty