@ garv ... the 'coil' in your circuit is actually a part of the relay (look above the coil for specs) alongwith the 2 switches. The diode is used as a 'freewheel diode'. The relay 'turns on' the triac and the CFL ... study the individual parts .... will help a lot as this is a very simple circuit.
This circuit is made to run on your domestic supply so that u can use it at your home (the 'core' is dc based though)
For the DC model, replace the input and rectifier section with a dc supply, and you will need a comparator acting as the switch ... as i said earlier ... refer datasheets