I have esigned a mini power supply which uses as input either a 12V power adapter or a USB-C charger capable of delivering 9-20V.

I have used the Buck booster the as inteface:

https://vi.aliexpress.com/item/1005005029522263.html?spm=a2g0o.order_list.order_list_main.186.4a011802b6vqGm&gatewayAdapt=glo2vnm

and for the USB connection a trigger board:

https://vi.aliexpress.com/item/1005005046765579.html?spm=a2g0o.order_list.order_list_main.462.4a011802b6vqGm&gatewayAdapt=glo2vnm

The switch from the back comuntes from 12V power adapter to the PD trigger board input.