Modular power supply apparatus wherein a plurality of d.c.-to-d.c. converters are coupled to an internally structured heat exchange channel through which fan driven air is passed in an unobstructed manner along a flow axis. Each of the converter modules is combined with a dedicated module circuit board which provides regulated output terminals in an orientation or direction arranged transversely to the flow axis. The opposite end of the module circuit boards are plugged into a main interconnect circuit board positioned along one side of the heat exchange channel. A support channel is provided outwardly of the main interconnect circuit board within which principal components of supporting circuitry are contained.
