Say by increasing your budget for targeted keyword, you increase the the clicks (and hence conversions). In theory this will work.
But
There are several other factors that will come into play. May be there is a saturation level in conversions, or there is not enough traffic.
The only way to find out is by doing it.
If your ROI is good you can give it a try, or better increase your spending budget gradually and see if conversions increase in same ratio or not.

Or better try targeting long term keywords which are closely related to your converting keywords.