james knott gjaidadguarogerscom randall r schulz wrote thursday 14 february 2008 1226 james knott wrote quite replying transformer comment switching supplies transformers often used input incoming ac rectified filtered resulting dc used power switching regulator provides desired output yowsa isolation provided transformer input things get ul regulatory agency approval guess youve forgotten old 5 tube acdc radios ran directly line power without power transformer whatsoever entirely possible design build safe power supply without using transformer provided theres appropriate electrical isolation supply exposed metal parts load mentioned another note switching power supplies transformer thats used covert high frequency oscillator power lower voltage fact theres rectifier capacitors ahead transformer doesnt make unsafe required proper isolation techniques used dont forget line frequency transformer handle hundred watts large heavy use openofficeorg tue 05 aug 2008 211146 0500 opensuse ot much power pc really consume