For the alternating drive of switches of a pulse frequency converter acting on a common AC-side terminal, the control pulses of the switches must be jointly latched at each alternation. For each switch, the control signal applied for its latching may be regarded as a set value for its switch voltage, whereas the actual switch voltage occurs only if after a storage time this switch actually extinguishes. By integration of the deviance, therefore, a correction signal is formed which is proportional to the storage time of the last fired switch or to the voltage-time area occurring at the output during the latch time. Thereby the distorting influence of voltage-time areas which are caused due to the spread between units of different latch times of different switches can be taken into consideration in the formation of the width-modulated control pulses.