Prevent Delta table merge to create a lot of small files?

Question

I am merging an update dataframe into a big Delta table. When doing so I noticed that the amount of parquet files increases drastically. I know that afterwards I can perform a vacuum command on that table with a retention period of 0 hours. However, I think this is pretty inefficient. Is there a way to turn off the delta versioning? I thought of converting that delta table into a parquet table but then I'm not able to perform a merge anymore...