You can use 220V->110V transformers to obtain 55V ac which you can rectify
and feed to your converter.

You can also use a thyristor based voltage regulator that can make 50Vef
ac from 110V ac. This is not an option for us in 220V countries.

You need to check whether the converters have complete galvanic
separation and insulation resistance to 1kV ac at least. Often they have
not and you need to use a transforemer. Note that checking the leakage
current with a 'human' probe is not enough. Imho go for a transformer.

Peter

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