The switching power supply provides 12 volts, at 10 amps, maximum, using a discrete transistor regulator with an op-amp functioning as a comparator in the feedback circuit.
http://members.tripod.com/michaelgellis/power4.html
In this small switching power supply, a Schmitt trigger oscillator is used to drive a switching transistor that supplies current to a small inductor. Energy is stored in the inductor while the transistor is on, and released into the load circuit when the transistor switches off.
http://ourworld.compuserve.com/homepages/Bill_Bowden/page4.htm#ps5.gif
Control circuit full bridge
http://www.hills2.u-net.com/electron/smps.htm
This site offers a download area of Christophe BASSO's SMPS Spice models.
http://perso.wanadoo.fr/cbasso/Spice.htm
Uses SG3524 and BUZ11
http://members.tripod.com/valveaudio/images/schematics/switcher1.JPG
switching regulator which uses LM2575-5.0
http://www.hobby-elec.org/e_ckt22.htm
switching regulator which used MC34063A
http://www.hobby-elec.org/e_ckt23.htm