Re: Who ever designed..
@Dave. I've done the reverse. I broke a Samsung monitor by using a 12V supply when it expected 19V. It's a bit counter-intuitive to break something with a lower voltage input. So, I took it apart, and discovered that a fuse is positioned in front of a switching regulator. It was blown, and I figured out what was happening. For sake of example, let's say the monitor used 38W. When 19V is connected, the switcher has to suck 2A to power the monitor. However, when I connected a 12V supply, the switcher is still churning out 38W, but it now needs to source ~3.2A from the input. This was enough to blow the input fuse, let's say it was a 3A fuse. An easy fix, but the lesson is to use the right supply!
P.s. For those of a technical bent, you might be interested in Linear Tech's app note, AN19, which is about the LT1070, an early switcher controller. An especially good read is the 'Troubleshooting Hints' section. My personal favourite is number 12.
12. Didn’t Read the Data Sheet
Then you shall have no pie