BillHo:
This is the circuit that use P-MOSFET to switch the supply line
http://www.edn.com/file/24877-Figure_2.pdf
http://www.edn.com/design/analog/4362161/Transistor-latch-improves-on-off-circuitry
Thanks for all the info guys,
What is the role of the DC/DC converter?
Also is the value of Q1 critial, or will any p channel mosfet be ok?