Need circuit for 10-12 VDC isolated power at 1 amp from 12 vdc 20 amp power supply

Sid,

If you refer to the TI Powerlab reference design section

http://www.ti.com/lsds/ti/analog/powermanagement/reference_design.page

and input the design parameters, you will get a list of posssible designs.For example the LM5022 is used on the PMP7899 reference design. This is a 48V output but it can be modified for a 12V output