so as to：主語は？

あなた：

電源は一定の大きさの電圧を出力する。電源制御手段は電源を制御する。制御部は、前記一定の大きさの電圧を出力させるように電源制御手段を制御する。

Here’s a clean, claim-friendly translation that keeps the actor clear:

The power supply outputs a voltage of a specified magnitude.
A power-supply control unit controls the power supply.
A control unit controls the power-supply control unit so that the power supply outputs the voltage of the specified magnitude.

If you want time-constancy (not just a set value), swap “specified” for “constant” in sentence 1.

How about "A control unit controls the power-supply control unit so as to output the voltage of the specified magnitude."?

Short answer: Grammatically possible, but not ideal.

Ambiguity: so as to output can read as if the control unit (or the power-supply control unit) is the thing outputting the voltage.
Clarity & idiom: Tech writing prefers “so that … outputs” or “to cause … to output” for explicit agency.
Style: so as to is wordier/old-fashioned.

…so as to cause the power supply to output a voltage of the specified magnitude.
…so as to have the power supply output a voltage of the specified magnitude.

(Use a voltage unless it’s already been introduced, in which case the voltage is fine.)

あなた：

How about "so that a voltage of the specified magnitude is output"?

ChatGPT:

Short answer: Grammatically fine, but weaker.

“so that a voltage of the specified magnitude is output” (passive) hides the actor. Readers may wonder who outputs it.
Tech/patent prose usually prefers explicit agency here.

Best:

…so that the power supply outputs a voltage of the specified magnitude. ← clear & active

If you insist on passive, clarify the agent:

…so that a voltage of the specified magnitude is output by the power supply.

Tiny notes:

Use a voltage on first mention; switch to the voltage after it’s been defined.
is output is acceptable; is outputted also exists but is less common.

和英特許翻訳メモ