Nearly all usecases for a power transformer are now better served by a switched mode power supply.<p>They tend to be much smaller, lighter, more efficient, cooler and cheaper. They also have features like adjustable output voltage, current limits, and overheat protection. Some can input and output AC or DC, at a configurable frequency and sometimes waveform. Some offer the same galvanic isolation that a transformer offers too.<p>The core of a switched mode supply usually <i>is</i> a transformer, or at least an inductor, but the key difference is that it operates at far higher frequencies than classic uses of transformers, which allows them to be far far smaller, and therefore cheaper for the same power output.