tag:blogger.com,1999:blog-4774014561040227748.post5908601107946315766..comments2024-03-22T10:42:05.161-06:00Comments on KA7OEI's blog: Quieting high-current switching power supplies used in the ham shack.Unknownnoreply@blogger.comBlogger4125tag:blogger.com,1999:blog-4774014561040227748.post-36078882541859397732019-01-15T23:06:44.304-07:002019-01-15T23:06:44.304-07:00This is very helpful, as I study for the Amateur E...This is very helpful, as I study for the Amateur Extra exam. Thanks. Posted by Earnest Hart | LifeFlicks, LLChttps://www.blogger.com/profile/11329435725692766710noreply@blogger.comtag:blogger.com,1999:blog-4774014561040227748.post-12239045778625615982016-09-20T17:37:46.486-06:002016-09-20T17:37:46.486-06:00I didn't make extensive measurements of the ou...I didn't make extensive measurements of the output ripple of the supply under the rated load, but I've never found it to be an issue.<br /><br />I must admit that I don't even remember the AC frequency ripple across the power supply's output terminals at load, but I do know that once I had done the modifications described above to reduce the "chassis to output terminal" noise depicted in Figures 4 and 5 the supplies became "invisible" from an RFI standpoint.<br /><br />KA7OEIhttps://www.blogger.com/profile/01153508130273704727noreply@blogger.comtag:blogger.com,1999:blog-4774014561040227748.post-42458095353464492322015-03-07T12:30:28.922-07:002015-03-07T12:30:28.922-07:00On the AC input inductors - which are typically du...On the AC input inductors - which are typically dual winding to suppress common-mode currents - the inductance values are typically in the range from 100uH to 10's of milliHenries: The ones depicted in the pictures are in the milliHenry range, potentially providing many ohms of reactance at frequencies of hundreds of kHz and up.<br /><br />Since it is practical to use only a fraction of a microfarad of capacitance across the AC mains and to "ground" to minimize "leakage" currents due to efficiency and safety issues - which can have ohms of reactance at the low frequency end - this high inductance is appropriate and necessary to suppress these signals.<br /><br /><br />On the high-current output the inductance is typically in the 10's of uH range, partially as a matter of practicality as it would be difficult to get a lot of inductance with a small amount of heavy-gauge wire with a reasonable-sized inductor that could also handle 10's of amps. <br /><br />At DC and low voltage it is practical to use large, high-quality capacitors that have fractions of ohms of reactance at the low end of the frequencies to be blocked (e.g. a few tens/hundreds kHz) so by the time one gets to HF, these relatively small amounts of inductance will have 10's or hundreds of ohms reactance and the (good quality!) bypass capacitors will do their job in shunting residual RF to the case ground, containing it within.<br /><br />73!<br />KA7OEIhttps://www.blogger.com/profile/01153508130273704727noreply@blogger.comtag:blogger.com,1999:blog-4774014561040227748.post-91199040933936009452015-03-07T09:44:18.606-07:002015-03-07T09:44:18.606-07:00Thanks this was very helpful. What are some typica...Thanks this was very helpful. What are some typical values of inductors you have seen?Ryan O'Connorhttps://www.blogger.com/profile/09174310851632889175noreply@blogger.com