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SMPS for vacuum tube power amplifiers.(status: back at it)

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Doctorandus_P:
If you are intesting with non-mainstream audio amplifiers then consider a voltage to current conveyor instead of a voltage amplifier.
For more background info, read:

strawberry:
LLC SMPS topology is the way to go in audio . you can find this kinda power supply on ebay aliexpress

SK_Caterpilar_SK:

--- Quote from: theworldbuilder on April 13, 2019, 01:58:20 pm ---Hey SK_Caterpillar_SK,

Just wanted to say that I'd be really interested in seeing this project progress.....

--- End quote ---

Progress so far:

The noise is caused by the filament heater supply being a crappy chinese PSU. I bought a 5V 8A supply that I modified the feedback to give 6,3V exactly, and some movearround. The entire thing is a Flyback supply. Its putting out 56W at the voltage shown (measured the anode current round about 130mA). The switching transformer for the mains version arrived but I dont know if I will ever use it. I hit so many roadblocks and solved one by other and so far the biggest problem is isolating the output from the input because you dont want mains refferenced output which ground can be either live or not. A second less of a problem is having ground loops. But the main concern is safety which I cannot reach currently. I need to figure out how to isolate the ouput voltage with a opto isolator from the input, and also figure out how am I going to power the TL494 on the mains side, so far I have came up with a capacitive dropper, would work but not ideal. The biggest thing slowing me down right now is the isolation, a problem that would truly need help with someone who knows how that stuff actually works.

Yet still I get told to buy some ebay powersupplies just as on the other forum .

SK_Caterpilar_SK:
So here is my problem. Opto feedback for the TL494. Really the only issue is how do I choose the values for the components. The original values are for 5Voutput voltage. I need it to work in the range of 400 to about 630V. Or I can just have them a fixed a fixed value and solder the components accordingly for the voltages. I would really appreaciate if someone would rather show me a way how to choose these values instead of just giving me the values,  if someone could tell me what values to use.

My idea was to simply lift the entire FB circuit with a resistor, so instead of grounding it directly I would put a resistor where the ground was originally and lift that entire circuit above ground. I just dont have an idea if that would work, and the most criticall of all is that its best to not load the output but very lightly. Small mA currents in a 5V supply dont matter but 1mA at 500V is HALF A WATT. Not like its a big deal considering the output power of the circuit but its there just generating heat.

Edit- the pics are fixed yes I noticed sorry my mistake

TimNJ:
Popular ways to get a low-voltage Vcc rail for powering  your primary side ICs are...

1.) Add another winding to your transformer. Usually called 'aux winding' or similar. You'll still need some sort of "bootstrap" supply to get the thing up at startup.
2.) Use a small offline switcher. Power Integrations makes controllers with integrated MOSFETs. Those are nice.

Regarding the output error amplifier. There are rigorous ways to determine those values, and not-so-rigorous ways to determine them. Ideally, you'd like to know the gain/phase response of your entire system. Then, you apply compensation to your feedback network to ensure that the system is unconditionally stable, under all conditions. You can look up feedback network compensation with TL431.

You can basically change:
1.) DC Gain
2.) Mid-band gain
3.) Frequency of pole
4.) Frequency of zero

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