frequency

Hello, everyone! I would like to ask you about my translation. Now I have a trouble with a translation agency, I have to make clear...:) Output voltage becomes three times of the voltage applied to the terminal by controlling. But I want to write it as "Output voltage is controlled..." so 1. Output voltage is controlled (to) three times of the voltage applied to the terminal. 2. Output voltage is controlled so that it is three times the voltage applied to the terminal. 2 is what the translation agency says. But I think it's a little bit diffirent what we want to say. Which is better? and I have to add "to" in the sentence 1? Thank you very much