Not strictly about (retro) computers, but still interesting. Article by Ken Shirriff on the history of the switching power supply and current power supply technology.
It also gives some context to the claim by Steve Jobs that the Apple ][ introduced the switching power supply. Following is from the article:
Power supplies are not without ardent champions, however, including one that might surprise you: Steve Jobs. According to his authorized biographer, Walter Isaacson, Jobs had strong feelings about the power supply of the pioneering Apple II personal computer and its designer, Rod Holt. Jobs’s claim, as reported by Isaacson, goes like this:
Instead of a conventional linear power supply, Holt built one like those used in oscilloscopes. It switched the power on and off not sixty times per second, but thousands of times; this allowed it to store the power for far less time, and thus throw off less heat. “That switching power supply was as revolutionary as the Apple II logic board was,” Jobs later said. “Rod doesn’t get a lot of credit for this in the history books, but he should. Every computer now uses switching power supplies, and they all rip off Rod Holt’s design.”
Jobs’s claim is a big one, and it didn’t sit right with me, so I did some investigating. I discovered that, although switching power supplies were revolutionary, the revolution took place between the late 1960s and the mid-1970s as switching power supplies took over from simple but inefficient linear power supplies. The Apple II, introduced in 1977, benefitted from this revolution but didn’t instigate it.