"Is it posible to use adc to convert continously changed signal without sampling the signal first??"

NO!
An analogue signal is continuously varying - in both time & amplitude;
A digital signal can only change in discrete steps - in both time & value.
The sampling process gives you the discrete time steps.

"I just need the digital data from the peak of the signal."

You mean you just want to measure the peak value?
Why not just use a capacitor, which will "smooth" the signal to its peak value?

Is this a case where it might be better if you said what you're trying to achieve, rather than just focus on this one issue of your implementation?
We might be able to suggest alternative strategies.

eg, are you trying to make an AC voltmeter?