Tim
Yeh, I designed some electronic transformers for halogens years ago using a saturating base drive transformer (Jensen converter I think) and bipolars.
It's a very simple topology and low cost due to the bipolars, but tricky to design for various reasons. The short circuit protection relied on the leakage inductance of the transformer.
No control electronics available for current limit etc.
Also, the storage time of the transistors eroded the effective duty cycle which limited the operating frequency.
Bipolars, Backer clamps, proportional base drive, RBROA, Second breakdown, all a thing of the past, thank God!
Dick