how to get continuously backup

I have small db and load is very less. I am set full backup at  9:00 pm once a day,and set  transaction log backup to every 15 min.

then i am taking the transaction log backup in 9:15,9:30,9:45..........  . My question is  I lost my data between 9:15 to 9:30 . in those time i will do some transactions.Then how to recover my data even with out lasing single  transactions also.