02-06-2021, 01:07 PM
(This post was last modified: 02-06-2021, 01:25 PM by Diabolical Artificer.)
I've looked at all my references and cannot find how to calculate whether a power supply is potentially resonant at LF or how to design for stability. I've looked in Radio Designers, Morgan Jones Valve amps, Crowhurst and loads more reference books.
As I have it we want a PSU that has a low OP Z and not resonant at VLF, how one works that out I can't find out. My HT PSU consists of an IE tfmr with a Rpri of 7.5r, and an Rsec of 32r. Vsec is 325v AC RMS into a fuse then a bridge rectifier then into a CLC filter of two 700u caps in series (350u) then a 5H choke, the two more 700u caps in series. All caps have 180k series resistors across them. HT is 410v. Load is 2562r as far as I can make out (410v HT/0.160mA) The Idc of 0.160mA is quiescent, I'd expect it to be about 1.5 times that at full whack.
I tried adding some small caps in parallel with the 2nd cap, a 10u and a 1u but no improvement. I worked out Xc and XL which is Xc = 454r and Xl = 3140 at 100hz and the PSU source resistance as 45r, but after that am not sure where to go next. Any ideas welcome.
Andy.
As I have it we want a PSU that has a low OP Z and not resonant at VLF, how one works that out I can't find out. My HT PSU consists of an IE tfmr with a Rpri of 7.5r, and an Rsec of 32r. Vsec is 325v AC RMS into a fuse then a bridge rectifier then into a CLC filter of two 700u caps in series (350u) then a 5H choke, the two more 700u caps in series. All caps have 180k series resistors across them. HT is 410v. Load is 2562r as far as I can make out (410v HT/0.160mA) The Idc of 0.160mA is quiescent, I'd expect it to be about 1.5 times that at full whack.
I tried adding some small caps in parallel with the 2nd cap, a 10u and a 1u but no improvement. I worked out Xc and XL which is Xc = 454r and Xl = 3140 at 100hz and the PSU source resistance as 45r, but after that am not sure where to go next. Any ideas welcome.
Andy.
