Repopulated Semi's twice now. Both times the board lit up and started to regulate. The first time I unplugged it and it never lit up again. The second time I ramped down the voltage using the variac. It is surviving. Need to understand why. Unloaded the PS produces 62Vdc.
Loaded the PS is producing 55V filtered DC into the regulator. It regulates well at 42VDC out, however, I have some noise on the output. ABout 3mVrms in the MHz region. see attached. I think that part of my problem is I am only using twisted wire for the sense. I will replace that shortly.
Nothing is getting hot, just a comfortable warm.
Loaded the PS is producing 55V filtered DC into the regulator. It regulates well at 42VDC out, however, I have some noise on the output. ABout 3mVrms in the MHz region. see attached. I think that part of my problem is I am only using twisted wire for the sense. I will replace that shortly.
Nothing is getting hot, just a comfortable warm.
Attachments
Repopulated Semi's twice now. Both times the board lit up and started to regulate. The first time I unplugged it and it never lit up again. The second time I ramped down the voltage using the variac. It is surviving. Need to understand why. Unloaded the PS produces 62Vdc.
Loaded the PS is producing 55V filtered DC into the regulator. It regulates well at 42VDC out, however, I have some noise on the output. ABout 3mVrms in the MHz region. see attached. I think that part of my problem is I am only using twisted wire for the sense. I will replace that shortly.
Nothing is getting hot, just a comfortable warm.
Congratulations
Don't forget the coaxial for remote sense could you use a small one RG179 type
Shielded cable for sense actually increased resonance. Now at 4mVrms and in the 4-8mHz region. Error amp is 2N5457 with Idss of 2.5mA.
Watching th scope as I bring the voltage up, I see low level noise <<1mVrms untill it starts to regulate. At 42V the trace shows it starting to oscillate in the MhZ region at the levels described above.
P.S. Corrected units on Idss
Watching th scope as I bring the voltage up, I see low level noise <<1mVrms untill it starts to regulate. At 42V the trace shows it starting to oscillate in the MhZ region at the levels described above.
P.S. Corrected units on Idss
No change at 100% and 200% (66pF and 99pF). I measured off of my scope. Fundemental resonance is 4.8mHz with higher order harmonics spread into it. Fundemental is 25mVpp
I will try the zobel next. When you say termination I assume you mean to ground. If I understand, you want me to run a 47uF across output.
I will try the zobel next. When you say termination I assume you mean to ground. If I understand, you want me to run a 47uF across output.
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Good question Andrew, I will measure CCS current in a minute. I can't easily measure shunt current however.
I put 33uF standard ESR in for Zobel with minimal impact. freq the same, less harmonic spread however. I will put the zobel back in and measure current.
Minimal impact there with such a decisive change in the termination type and value makes me suspicious for a CCS resonance. If it was simply noise should have changed a lot or gone. Parallel one resistor on CCS Mosfet's gate stopper, so it goes half value. Changes something? Also does the decoupler on Vin affects? VR1/R1=CCS current BTW.
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