I've seen a lot of self oscillating power supplies in 12v systems (even when FETs were widely available) but I've never seen any using FETs to drive the transformer. All used BJTs. Are FETs incompatible with self-oscillating power supplies?
Some power jFETs have been available for a small time window; I think they have mostly disappeared.
MOSFETs by contrast are very much alive and well, and easily withstand the 600V required for a SMPS. Some designers follow the easiest route, and opt for a controller IC.
Others chose the hard way, and create a self-oscillating supply from a few active components. If you open a sufficient number of wall-warts, you will see examples of both philosophies, and that applies to "western" supplies and "extreme-eastern" ones as well
MOSFETs by contrast are very much alive and well, and easily withstand the 600V required for a SMPS. Some designers follow the easiest route, and opt for a controller IC.
Others chose the hard way, and create a self-oscillating supply from a few active components. If you open a sufficient number of wall-warts, you will see examples of both philosophies, and that applies to "western" supplies and "extreme-eastern" ones as well