30VDC, variable current control circuit

hi guys i need help with making a power supply circuit that produces 30VDC with the ability change the current from 1A to 0A or as near as possible.
the circuit will be battery powed so dc input please
so in summery looking for 30VDC, variable current circuit with a dc input.

if anyone knows how to build one of these or were to get one it would be much appreciated.thanks jesse

What is the battery voltage?

dosnt matter would like to keep it 12v or under but up to 37volts is fine