The correct term for the electronic variants of transformers would be “primary switched switching power supply”, but the term “electronic transformer” is often used in the lighting industry. So we stick with it. In contrast to conventional power supplies, the electronic transformer operates at a higher frequency and can thus be more efficient. This is because, at higher frequencies, transformers need less magnet core volume for the same power. For this purpose, the main voltage has to be rectified and “screened”, then chopped into a higher frequency voltage and after the transformation in a high frequency base, re-aligned to the desired alternating voltage 11.5 -12V. This happens in fractions of seconds and time and time again.
The electronic switching devices, which are smaller, lighter, cheaper and more versatile, are very popular. They are indispensable especially for recessed lighting, as they pass through a hole cut through the small flat design and do not have to be hidden anywhere in the ceiling. Also for table lamps electronic switching power supplies are popular, then as a rule as a plug transformer.
Further advantages of the electronic transformers are the integrated overvoltage protection, which means that the transformer switches off when too much voltage is generated in the power supply. The cable length should not exceed approx. 2m, in order to avoid problems with voltage loss and EMC (electromagnetic compatibility). Electronic transformers are usually available with max. 250 VA, since for larger versions, a much higher level of protection would have to be used.
Also a lot of LED-based lamps (via an LED driver) work with a transformer or switch to reduce the voltage of the power line.