Method for determining a time of a zero crossing of a winding phase current in a polyphase electric machine, the electric machine being actuated with the aid of a driver circuit (31; 50) with power switches (36; 37; 52, 53) in order to provide a plurality of phase voltages, which are applied to connection nodes (A1, A2, B1, B2) of the electric machine which are associated with corresponding phases, the power switches (36, 37; 52, 53) each being connected in series between a high supply potential (V H) and a low supply potential (V L), the respective connection node (A1, A2, B1, B2) being provided between the power switches (36, 37; 52, 53), at least some of the power switches (36, 37; 52, 53) being actuable cyclically on the basis of pulse width modulation with a duty factor in order to apply different potentials alternately to one of the connection nodes (A1, A2, B1, B2), said method comprising the following steps: - actuating the driver circuit (31; 50) for providing the phase voltages in order to operate the electric machine; - deactivating the pulse-width-modulated actuation for at least one of the power switches (36, 37; 52, 53), with the result that the at least one power switch (36, 37; 52, 53) is switched so as to be permanently nonconducting and said power switch is excluded from the clocking by the pulse width modulation, and, at least during a time segment in each cycle of the pulse width modulation, no potential is applied by the driver circuit (31; 50) to the connection nodes (A1, A2, B1, B2), the cycle being determined by a cyclic actuation of the pulse width modulation; - detecting a diode voltage across a freewheeling diode, with which the deactivated power switch (36, 37; 52, 53) is provided, within the time segment; - fixing the time of the zero crossing of the winding phase current as the time after which, within the time segment, there is no longer a diode voltage present across the freewheeling diode (40; 54), the diode voltage being effected through a diode current in the forward direction; characterized in that the deactivation of the pulse-width-modulated actuation for at least one of the power switches (36, 37; 52, 53) is performed within a measurement time window, wherein only that power switch (36, 37; 52, 53) is deactivated through which the instantaneous winding phase current effects a diode current in the forward direction. - actuating the driver circuit (31; 50) for providing the phase voltages in order to operate the electric machine; - deactivating the pulse-width-modulated actuation for at least one of the power switches (36, 37; 52, 53), with the result that the at least one power switch (36, 37; 52, 53) is switched so as to be permanently nonconducting and said power switch is excluded from the clocking by the pulse width modulation, and, at least during a time segment in each cycle of the pulse width modulation, no potential is applied by the driver circuit (31; 50) to the connection nodes (A1, A2, B1, B2), the cycle being determined by a cyclic actuation of the pulse width modulation; - detecting a diode voltage across a freewheeling diode, with which the deactivated power switch (36, 37; 52, 53) is provided, within the time segment; - fixing the time of the zero crossing of the winding phase current as the time after which, within the time segment, there is no longer a diode voltage present across the freewheeling diode (40; 54), the diode voltage being effected through a diode current in the forward direction;