SMPS

A switched-mode power supply (SMPS), also called switching-mode power supply, switch-mode power supply, switched power supply, or simply switcher, is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently.

Interior view of an ATX SMPS:

A: Bridge rectifier;

B: input filter capacitors;

Between B and C: heat sink for switching active components of primary voltage ;

C: transformer:

Between C and D: heat sink for switching active components of at least five secondary voltages, per the ATX specification;

D: output filter coil for the secondary with the largest power rating. In close proximity, filter coils for the other secondaries;

E: output filter capacitors.

The coil and large rectangular yellow capacitor below the bridge rectifier form an EMI filter and are not part of the main circuit board.