标签: supplies

We are aware that switching power supplies (converters), whether AC/DC or DC/DC, are almost always more efficient than linear versions. We also know that the weight and size difference is also dramatic, as well as much more tangible and immediately apparent. But sometimes, you have to see the two power supplies side-by-side to have that reality hit you.   Recently, while rummaging through my collection of AC/DC converters (aka "wall warts"), I came across two from way back in the day for an Iomega ZIP drive from around 1995.   The supplied Iomega ZIP drive linear converter (left) and the replacement switching converter (right) both produce a 5 V/1 A DC output, but with very different weight and size.   The numbers for these units, both rated at 5 V/1 A, are dramatic and tell the story beyond just efficiency, which I didn't measure:   - Original unit: 510 grams (18 oz), 55 mm x 80 mm x 55 mm - Replacement: 70 grams (2.5 oz), 45 mm x 50 mm x 25 mm   That’s a huge savings in weight and size: the switching unit is about 1/7 the weight and ¼ the size of the linear one shipped with the drive.   Physically large and hefty linear supplies and converters used to be the standard, of course. I have and still use an Analog Devices model 956 AC/DC converter, rated at 5 V/2 A.   Don't drop this 5 V/2 A linear supply, you could break a toe—but it does inspire confidence due to the size and heft, which were considered state-of-the-art at the time, circa 1977. This epoxy-potted unit comes with four #4-40 threaded inserts for mounting it to a PC board or chassis with screws -- very convenient and necessary.   Not only is it is still working, but due to its heft and size (865 grams, 110 mm × 68 nn × 50 mm), it exudes an aura of providing "serious" power compared to a small, lightweight switcher, even if that aura may be a self-imposed, projected image I have created. You don't mess with this supply, is what it seems to say to the world.   I recently saw one offered on eBay for $60 (why would you want one?) and it says the original price was $525—another example of super-shrinkage, compared to a new switching 5 V/2 A unit.   Do you have any other examples of dramatic change in weight and size, besides the often-cited ones of processors, ICs, phones, and storage?