Abstract: An internal combustion engine with combined pressure charging has an exhaust turbocharger turbine arranged in an exhaust conduit of the internal combustion engine driving a compressor arranged in an intake conduit. A mechanically driven supercharger is arranged downstream of the compressor and is coupled continuously variably to the engine via a Fottinger speed transformer with variable-pitch guide vanes and variable speed slip. To bypass the mechanically driven supercharger, a bypass conduit is provided. A circulating-air slide is arranged in the bypass conduit for controlling the air quantity bypassing the mechanically driven supercharger. The degree of opening of the circulating-air slide and the slip of the Fottinger speed transformer are controlled as a function of operating parameters such that the charge-air pressure is adjusted to a predetermined set point value.