Hi - according to OralB, you can use it in countries with 110v (resp. it works with 110-240v) - so, you won't need a converter (only found in german on a quick google search:https://www.oralb.de/de-de...)
...but you will need a travel adapter, if you go to country with different than CH-plugs, i think.

hope that helps and BR, have a good trip ;)