You are right about the Dimming Ballast + Peripherals being smaller (and more efficient) is a result of improved Technology (Partly from the introduction of modern Electronic Components).
Current designs range from "Hybrid" components (Passive and Active, or combinations of core/coil and discrete Electronic components), to complete IC based VLSI components.
I am totally impressed with the Technology and Equipment found in the Lighting Industry today!!!
It has evolved drammatically in a relatively short time (since the 1980's).
The improvements affect all lighting applications - some with small effects, others with major effects.
Dimming Ballasts now come in 3 flavors:
* Standard Design (Phase "Chopped" by switching device),
* Integrated Circuit (IC) design - used in Program RS applications,
* Controllable Integrated Circuit (CIC) design.
Electronic Ballasting has reached into the HID application recently. The primary intentions are energy efficiency and a "Uniform" component which can be used for several different applications, instead of targeted to one specific application.
Testing and studies have found that High Frequency operation of HID lamps does not always result in optimum performance - and at times may reduce performance!
This is not 100% proven yet - only laboratory studies across a limited range.
This seems contradictive for discharge lamps!
Fluorescent lamps perform much better at Higher Frequencies (>20 KHz), but the HIDs seem to perform better at Lower Frequencies (<200 Hz).
I could go on and on about the things I have recently studied regarding Lighting equipment!, so to keep from putting everyone in the forum to sleep (bored to sleep), I'll end here.