Design only protects the appearance of the product; When judging infringement, from the point of view of ordinary consumers, it is infringement to think that it is the same product; If there are obvious differences, it is not infringement if it is not the same product.
The utility model protects the structure, that is to say, it protects the internal things. If your structure is the same as the scope of protection in his claim, it is infringement; if it is different, it is not infringement.
There are certain constraints between them, but the utility model is more dominant; Because the scope of design protection is small, it is easier to avoid. However, if there is no problem in the writing of utility model patent documents, it is still difficult to avoid it.