1
Spark Gap Tesla Coils (SGTC) / Re: Top load material selection
« on: October 05, 2022, 10:15:42 AM »
I doubt it matters at 100kV...
This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to. 1
Spark Gap Tesla Coils (SGTC) / Re: Top load material selection« on: October 05, 2022, 10:15:42 AM »
I doubt it matters at 100kV...
2
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 06, 2021, 05:16:24 PM »
I think it must be someting linked to the q factor of converter transformer cause i found that even at higher output power of the converter, but different winding the sony power supply can have a cleaner output and no squeaking.Usually power supply phase goes wrong when abused and the scope can't sinc properly for a clear signal picture.
3
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 05, 2021, 07:22:17 PM »
The output of sony playstation smps is quite interesting as there's a resonance that's 1/2...2/3 of the whole duty cycle...which puts it in the quasiresonant smps cathegory.Acually that resonance is 220khz, the main switching frequency is lower .I suspect that resonance get lower...but i need to make some measurements on the power supply itself.
4
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 05, 2021, 07:18:02 PM »
apart from 6 X 470uf paralleled capacitors of the power supply , i have another 3 x 6800uf paralellled capacitors...
5
Light, Lasers and Optics / Re: COHERENT transformerless 81mHz amplifier schematic ?« on: March 05, 2021, 11:54:31 AM »
Never thougt about rf amplifiers as modulated resonant converters working at high frequencie, but i never dived into it too much.I was mostly a low noise audio geek, but it looks like everything is nature, art and science is resonant
https://www.ab4oj.com/dl/eb104.pdf https://www.rf-microwave.com/app/resources/uploads/transistors/Motorola_AN758.pdf 6
Light, Lasers and Optics / Re: COHERENT transformerless 81mHz amplifier schematic ?« on: March 05, 2021, 09:32:25 AM »That amplifier topology was invented by Helge Granberg at Motorola in the early 1990sThank you Sir! 7
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 05, 2021, 09:16:51 AM »
and my final schematic, except the resonant capacitor value which depends on the chosen frequency of operation which seems to be better a subharmonic of the power supply frequncy.Not sure if i can sinc my power suply with the converter but i'll try.
8
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 05, 2021, 08:40:02 AM »I've never had repeatability issues with LTSpice. It is a bit cryptic - many hidden commands that aren't officially documented. However, there are great online resources - wiki and user groups. It is the most powerful free simulator to my knowledge.I am on the last spice version... As for your converter design i can only say thank you! I finished the circuit and tried it today with 2sk941 as driver and 2 paralleled irfz46 on each side.Much better power transfer, much higher achievable frequency range, less heat dissipation.I tried it from 49khz to 190khz.At some frequencies it interfered with the power supply switching frequency which got squeacky at some frequencies.The power supply operates at 220khz and it produces less noise when the converter is operating at a quarter or half its frequency .At around 50khz , the converter got te best power transfer with transistor switching losses being the lowest so the transistors were cold there. I may consider to modify the power supply frequency and hopefully it will work.At higer frequencies the irfz46(with no heatsink) would get warmer but not by much... I got +-11.5v with one winding and a doubler. 420v on 20 kohm and 6v on 3 ohms which is all i need for my phono preamp.I will use this converter to check also an an electrostatic headpones amplifier that needs 600 vdc for anode and 12v for fillaments which was halted in development a year ago due to the lack of a suitable supply. 9
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 04, 2021, 09:35:40 PM »
Never tried simmetrix, but thanks for suggestion!
10
Capacitor Banks / Re: Resonant capacitors on Chinese ZVS drivers« on: March 04, 2021, 04:56:30 PM »
The 100v cap , the bigger one at the right is the low loss one.It might be polypropylene foil or polystirene foil...i ave no idea but usually the low loss capacitors are the bigger ones.They are from a very high quality resonant Hitachi power supply for high speed trains converters.
11
Light, Lasers and Optics / Re: Light, laser and optics - Link collection« on: March 04, 2021, 04:41:06 PM »
I just hope i'm not bothering...
Wikipedia is a very good point to start on this subject too, because every topic provides links to other subjects in the area and from very simple notions you can get to quite advanced concepts in a very constructive manner . Even better start with reading Samuel M. Goldwasser CV: http://repairfaq.cis.upenn.edu/Misc/sambio.htm 12
Light, Lasers and Optics / Re: COHERENT transformerless 81mHz amplifier schematic ?« on: March 04, 2021, 03:18:19 PM »
Cool, now i know the name so i can download some tech papers to maybe understand that better.
The history of RF pumped lasers starts with UK based AEA technology bought probably by Rofin Sinair and implemented in their transverse gas flow lasers too which used parallel anodes placed at about 2mm one from another working as a capacitor which was in series with some paralleled inductors resonating at a fixed frequency delivered by this amplifier in short PWM bursts up to 100khz.With the help of a UV ionizing lamp or a secondary RF amplifier the laser discharge was initiated.This system provided a very high quality laser compared with other pumping methods. You can check their early patents: https://patents.google.com/patent/US4288756 https://patents.google.com/patent/US4077018 Not really sure about the whole history, but transversal flow was better to be used with an RF pumping system. COHERENT , based in the US used same technology later , got better bussiness and a few years ago aquired its mother company, Rofin which had better but more expensive technology. The second patent is the origin of later circular flow Trumpf lasers in Germany which integrated very precise CNC in their machines. You can check any patent linked to rf pumped transverse flow lasers online like this going to Raytheon: https://patents.google.com/patent/US4651325 I'm probably wrong about who's the true inventor of this tecnology, but that's not really important today. 13
Light, Lasers and Optics / Re: COHERENT transformerless 81mHz amplifier schematic ?« on: March 04, 2021, 01:48:05 PM »
Thank you Sir! You've been really helpfull.Never found the time in the last 12 years to go back to lasers altough i still have tons of optical things around me from that era.I think i saw some similar rf amplifier in some Siemens RMN machines two years ago.I knew it was coax coupled , i just wanted to say it doesn't use ferrites indeed.Maybe one day i'll build a 40w co2 laser for myself.I fixed everything in those coherent lasers except the rf units as i didn't have the experience, nor i did have the theoretical background to go there.At the time i was servicing two generations of co2 lasers and the older one used tons of ferrites at 81mHz while this one at 100Mhz scraped them all together.
Is this some Yagy baloon circuit or similar? How is it called technicaly? 14
Light, Lasers and Optics / COHERENT transformerless 81mHz amplifier schematic ?« on: March 04, 2021, 10:42:41 AM »
I'd be interested in the schematic for any of their 40w+ CO2 laser transformerless(no ferrite core) amps like this one:
/>I used to fix their lasers 12 years ago and i remember that kind of amplifier being their last embodiment which blew me away at the time.Looks like their RF manufacturer is alpha telecom apparently doing the amps for yaeshu...I'm not knowledgeable in rf field although i used to have a HAM radio operator licence, but i'd like to learn a bit more on that. 15
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 04, 2021, 09:34:59 AM »
restarted the computer again and it seems that my ltspice math models are unbalanced by default...well...not quite right, thre's the csunt .option there, but i have very unstable results from time to time...so i need to restart the computer sometimes to be sure about ltspice results.
16
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 04, 2021, 09:08:55 AM »With these types of symmetrical circuits the transient sim can sometimes get stuck in perfect balance - since all the parts are mathematically identical. It helps to deliberately unbalance the circuit (like the real world) to get things started. I find adding a few pF to one of the power fet gates is usually enough.here's what i "love" about LtSpice: restarting it next day all its results are screwed: 17
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 03, 2021, 11:20:38 PM »
I don't think i know how to specify the initial current for inductors but for now its clear that until now i couldn't make ltspice accept two transformer primaries in parallel even with series resistance specified....
As i already tried my circuit with Baxandall converter , i will tell that i opted for a different version as having two transformers in parallel is raising the resonant frequency and ask me for bigger parallel capacitor if i don't want the power to go too low.PC 40 core is specified up to 250khz but honestly the power got lower when going from 40khz to 80 khz maybe due to semiconductor inherent losses. So i went a different road: I paralleled a secondary winding from the pc 40 core with the primary of the second high voltage transformer and the coupling losses are covered by the lower resonant frequency while a dead short on the high voltage side will be much more forgiving to the converter's transistors .I already tested that for a few times and it works very well.You have some taste of my circuit in the photo. 18
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 03, 2021, 10:03:26 PM »Indeed , i couldn't make even one transformer work untill i added some 0.2 ohm to the input inductor, then naturally added simillar series resistance to other inductors too, also added some 5...10pf winding capacitance too as i had some convergence rules already that didn't help enough.I still need to find out how to properly sim two transformers in parallel and actually learn to sim true transformers.Just saw some CUK material on TDK PC40, but its a bit too theoretical for me at the moment: https://core.ac.uk/download/pdf/4876634.pdf 19
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 03, 2021, 03:13:30 PM »
Now here's smth i really am worried about: the power dissipation on fet drivers increases proportionally with the number of paralleled fets probably because of the gate capacitance of power transistors so some series resistors might need to be added there just to make the circuit more linear although i tried that already and the dissipated power on drivers is increasing instead of decreasing...just another counterintuitive thing, but it probably interferes with the converter efficiency...
Yet compared with original Mazilli your circuit simulates much better in terms of thermal efficiency.I'll see later how the real thing behaves. 20
Transformer (Ferrite Core) / Re: Baxandall converter strange output« on: March 03, 2021, 01:18:22 PM »
loading a single transformer there's no waveform anymore...
until i add some parasitics to input inductor and the output looks as it should. also the driver power dissipation looks pretty good to me at half the load althoug at full load some oscillations show up but i am really far from a true simulation of te real ting anyway.Now i'm more confident. |