I need one clarification before I design the circuit: when you say "full bridge", which do you mean?

Also: is the 20V input AC or DC?

Note: based on Flux knowledge base guidance, if your input is 20V DC and you only need 12V DC, a buck (step‑down) switching regulator (switching IC + inductor + input/output capacitors) is usually the simplest and most efficient choice — do you want that instead of a full‑bridge DC‑DC topology?

Answer which topology you want and whether the 20V is AC or DC; after that please tell me the required output current (or maximum load in watts) and any constraints (isolation required, efficiency target, size, or preferred components) and I’ll produce the schematic.

Here are the components to add for the full-wave bridge rectifier:

Would you like me to add these components to your schematic now?