Below is a functional block diagram that abstracts the internal architecture (no copyrighted layout, only a conceptual view).
Even without the official PDF, standard reverse engineering reveals that the JYMC220BI follows a classic topology. Here are the core components you will find on the board: jymc220bi schematic full
[ V_OUT = V_REF \times \left(1 + \fracR_1R_2\right) ] Below is a functional block diagram that abstracts
If you cannot find the full schematic, use a multimeter in diode mode to trace continuity from these connector pins back to the transformer and diodes. This is manual reverse engineering. jymc220bi schematic full