You may have to design two separate circuits then cascade them. The first circuit is a rectifier which may not need SCRs (Diodes can do); then a DC/DC converter (voltage regulator).
Without basic knowledge of power electronis, it may be necessary to read more than the title to understand how the literature is related to your problem. Actually the book has a complete chapter on controlled rectifiers, it is valuable to understand the operation principles and possible design variations. AC/DC circuits are generally regarded as power converters, by the way.
You can design a scr "regulator" from the scratch using standard components and basic electronic circuits as building blocks, e. g. ramp generator, PI controller, comparator, trigger pulse generator. The circuit shown by largosoft should be a starting point.
P.S.: Using a saturated BJT (or more general, a turn-off-capable switch) instead of a SCR as in the patent presentec by mister_rf, is also a good idea. It reduces control process deadtime considerably and eases voltage regulation, but increases power circuit complexity. Also additional measures to prevent from switch desaturation may be necessary.