A power switch apparatus for a power converter includes a semiconductor power switch and a gate drive unit connected to the semiconductor power switch for supplying gate drive signals to the semiconductor power switch to switch it on and off to cause the power converter to generate an alternating current voltage having a nominal operational frequency based on command signals received from a controller. The gate drive unit receives command signals based on the AC voltage to be generated and to alter the switching events of the semiconductor power switch by addition of a pre-defined jitter-like deviation to the gate drive signals such as to cause the power converter to generate an AC voltage having a modified operational frequency which partly and temporarily deviates from the nominal operational frequency by a pre-defined minimum percentage. A power converter comprising such a power switch apparatus is also disclosed.