class Devise::RegistrationsController

def after_update_path_for(resource)

this method in your own RegistrationsController.
The default url to be used after updating a resource. You need to overwrite 
def after_update_path_for(resource)
  sign_in_after_change_password? ? signed_in_root_path(resource) : new_session_path(resource_name)
end