01.08.2014, 08:24 PM
Zitat:Original geschrieben von Alex KiticI'm sorry
I just wrote a very long post and found out that in the meantime I had to log again... did not copy my text in time, so now I am writing this short version.
. Ich benutze "Lazarus" 
Zitat:Original geschrieben von Alex KiticDas Problem bei Halogentrafos ist die 100Hz-Modulation.
I am glad that you do not consider the HF AC as some anathema....
Zitat:Original geschrieben von Alex KiticIch habe die Werte gemessen (!) und dabe die Temperatur der Power-BJT überwacht. Ich vermute, dass die "60 Watt" defensiv sind.
As for the high voltage schematics included, you should correct the DC output current
Zitat:Original geschrieben von Alex KiticDas ist gefährlich! Damit umgehst Du die Kurzschlussfestigkeit des Trafos.
My solution includes two steps:
1) Added cap to improve rectification (much lower ripple) in the initial stage, at the input to the half-wave oscillator circuit.
Zitat:Original geschrieben von Alex KiticIch habe am Original nur den Mindestlaststrom reduziert, damit der Trafo auch ohne Anodenstrom schwingt.
2) Adjusted number of turns on the secondary (and the primary if need be) of the ferrite core output transformer of the unit.
Zitat:Original geschrieben von Alex KiticNein! Der Halogentrafo wird 100 mal pro Sekunde gezündet. Das ist der Trick, der einen Halogentrafo kurzschlussfest macht.
A full fledged solution would include a regulator in front of the half-wave oscillator, to get a regulated DC voltage (thus a regulated AC output) and get rid of all relevant ripple (a regulator will have additional -60dB ripple rejection).
Zitat:Original geschrieben von Alex KiticIch habe große Siebkapazitäten verwendet, um die 100Hz Modulation zu sieben. Der elektronische Halogentrafo ersetzt lediglich einen konventionellen Trafo. Die Spannungen wurden gemessen.
If you choose to add a transformer on the output AC side, you should get extremely clean (in terms of 50/100Hz ripple) DC output, because all the ripple would be from a 40-60kHz source, i.e. at 80-120kHz and the output would be regulated as well (due to the regulation of the initial DC that is in direct proportion to the AC output). Of course, regulating the DC in front of the half-wave circuit means a rather large increase of voltage at the output, approximately 1.40x probably. This means that the output of your added transformer would also be at higher voltage and you could probably adjust it to be around 300V without resorting to a doubler, hence getting even more output current...
Zitat:Original geschrieben von Alex KiticJa. Das seh ich auch so.
But my main interest here at the moment is creating interest in the use of HF AC for direct heated tubes, as a promising solution that might one day become "the" best sounding alternative.