Step one of an AC to DC switch mode power supply is generally to rectify to DC/filter before chopping up at high frequency (in the KHz). It couldn't care less within reason the frequency of the AC input voltage. Whether certified or not is a different matter.
In the unlikely event you have a mobile device with a power supply which accepts only say 60hz/120v DO NOT use on 400hz. The switch mode PSUs will take say 110-240v 50-60hz.
Last edited by tom775257; 20th June 2017 at 16:14.