It is my first power supply project. I will supply 300 watt vehicle audio amplifier with this supply. I will use nominal 24V and 14A at my system Vehicle input 24V and my amlifier 12V-30V but when i measure vehicle input, i see surge and spike some times and exceed the limits. I need to know that, if i design only surgey and input protection circuit. Is it protect my amplifier or am i need buck/boost converter?
The voltage spikes in automotive environments are common, but since they are brief, DC-DC converter is not usually needed - you can go by with linear regulation. What you are looking for is a transient voltage limiter. Unfortunately TVS diodes aren't usually a good solution here, as the transients can be long enough to burn out the TVS and after that you've got no protection.
What you can do is roll your own voltage limiter as described in this article:
By changing the zener (D1) to 24V you'd get 24V limiter.
In my opinion, as the amplifier is an automotive amplifier, it is likely already protected from the voltage surges that are typical of that environment. If you are still on the belt and braces approach, then I suggest to look at this post of a couple of months back, where myself and others have described the best ways of removing these spikes. TVS is one of the different stages, which as someone else mentioned, is not enough to cope. you need to add a number of other parts, which include capacitors and common mode chokes. Another solution is to buy a ready made automotive surge suppressor.