A simple way to implement a fuel cell (FC) emulator is by means of programming a dc power supply present in all power electronic laboratories. However, in many cases the current and voltage ranges of these dc power supplies are different than those required to emulate a specific FC model. In this paper a possible solution is proposed to emulate a proton exchange membrane fuel cell (PEMFC) system by means of any dc power supply able to provide the maximum power of the FC to be emulated. The solution is the connection of a dc transformer based on the versatile dc-dc noninverting buck-boost converter between the dc power supply and the load to adapt the voltage or current to the fuel cell which wants to be emulated. Simulation results using the recently reported Ballard NEXA 1.2 kW diffusive FC model to control the different dc power supplies illustrate the advantages of this new canonical element, the dc transformer, for power processing.