Switched-mode power supplies (SMPS) are confidently replacing outdated linear power supplies. They are distinguished by high performance, improved stabilization indicators and compactness. The SMPS are widely used in power supply of control systems for small energy facilities. The article is devoted to the research of forward converter parameters. The task of research is to establish quantitative interrelations between the parameters of the converter elements and the energy loss in them. An analytical model of forward converter has been developed, which allowed revealing the main regularities of the processes occurring in the converter. A simulation model of the power source, made on the basis of forward converter has been developed. Using the dependences obtained on the simulation model, rational parameters of the converter elements have been determined, ensuring the maximum level of electromagnetic compatibility and the minimum level of power losses. The optimum values of the forward converter parameters have been used in the design of a power source prototype. The results of studies of the prototype confirm a high level of electromagnetic compatibility.