The present invention relates to a circuit arrangement and to a method for sensorless commutation of electronically commutated synchronous machines such as, for example, EC motors, wherein the terminal values at the connection terminals of the synchronous machine are processed by means of a rotor position estimator based on the EMF of the synchronous machine and of a known motor model preferably in a PLL structure for sensorless determination of rotor position information, and said information is used for commutation.