I don;t get the point. If the headset is in use, so must be the sound system and that shouldn't allow the system to sleep. The simplest option is to extend the time before the sleep cuts in.
Whoever told you it was in USB Controllers was mistaken but if you plug the headset in and go into Control Panel>Device Manager, and find the headset in the list. Right click it, go into Properties and see if there's a tab named Power Management, tell it not to allow the device to be turned off to save power.
If that doesn't do it for you, try Control Panel>Sound and see if that has that facility to change.