Dc-dc power supply with modular transformer and transformer assembly

A transformer assembly configured for a DC-DC power supply with a primary circuit and a secondary circuit, the transformer assembly comprising:

• M transformer sets electrically connected in parallel between the primary circuit and the secondary circuit, wherein each of the M transformer sets comprises N transformers, where M and N are positive integers, wherein each said transformer comprises a first primary winding, a second primary winding, a first secondary winding, and a second secondary winding, a connection node of the first secondary winding and the second secondary winding is electrically connected to an output capacitor of the secondary circuit, and each of the first secondary winding and the second secondary winding is electrically connected to a corresponding secondary switch of the secondary circuit,
• wherein the first and second primary windings of the N transformers in each of the M transformer sets are electrically connected in series, all M*N transformers of the M transformer sets are arranged along a first direction, and each of the M*N transformers comprises a first side column, a center column, and a second side column arranged along the first direction with each extending along a second direction, which is perpendicular to the first direction.