Timeline for How to safely generate 200V from low voltage supply
Current License: CC BY-SA 4.0
13 events
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| Dec 18, 2018 at 15:42 | comment | added | Andy aka | You shouldn't need a secondary snubber - maybe you can reveal what you tried? Anything that tries to clamp the negative voltage on the secondary side is going to be problematic. Good news about getting it to work though. | |
| Dec 18, 2018 at 12:55 | comment | added | deltamac | I have this basically working, now. 25uH primary (3 turns). 30 turns to HV winding, 2 turns on the LV windings. My primary side snubber is a 1n +20R and runs just a little warm. The secondary snubber I can't actually get to work. Any reasonable values I try make it oscillate and you can hear the cermic caps pulsing like crazy. I have just left them off as it appears to work reasonably well despit the poor damping on the secondary ring. | |
| Dec 15, 2018 at 6:46 | comment | added | Andy aka | There’s always parasitic capacitance from the mosfet that drives the primary and this is usually the dominator, usually several times higher than reflected capacitance from the secondary. I’m struggling to see that it is capacitance. | |
| Dec 15, 2018 at 2:27 | comment | added | deltamac | If this does work... I’m not actually sure what the problem would have been. Does a large turns ratio exacerbate parasitic capacitance somehow? I still have 30 turns on the secondary... | |
| Dec 15, 2018 at 2:23 | comment | added | deltamac | Good news! I think this is almost working! I re-wound the transformer with a slightly higher primary inductance (3 turns) and a lower turns ratio (1:10). It regulates correctly to 200V with light loads and the crazy sensitive to capacitance is gone. It’s now under-volting on a current trip at 2A. I think I can adjust and make this work. It also now drives all three secondaries simultaneously. | |
| Dec 13, 2018 at 17:56 | comment | added | Andy aka | You must have a load connected that is close to what the maximum is. Did you have a load? You were right about the calculations for not gapping it. I'm so used to gapping flybacks that I really did think you'd screwed up in this area especially how you didn't understand the main reason behind it. Is it operating at 100 kHz and at what duty into what load with what output voltage (and input voltage)? | |
| Dec 13, 2018 at 16:15 | comment | added | deltamac | The other strange thing is that relates to your walk up comment. It limits below the nominal duty cycle on a current limit, and somehow outputs TOO much voltage. | |
| Dec 13, 2018 at 16:14 | comment | added | deltamac | The thing that sticks out is that my turns ratio is probably higher than it has to be. Maybe I can turn that back and maybe reduce the parasitic. Is there a particular winding pattern I should use to minimize them? | |
| Dec 13, 2018 at 16:13 | comment | added | deltamac | I actually do have snubber circuits designed and installed, and they seem to be doing a good job of damping the ringing due to leakage. | |
| Dec 13, 2018 at 16:11 | comment | added | deltamac | This is exactly my calculations, and the reasoning behind thinking it is ok not to use a gapped transformer. | |
| Dec 13, 2018 at 9:25 | history | edited | Andy aka | CC BY-SA 4.0 |
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| Dec 12, 2018 at 21:46 | history | edited | Andy aka | CC BY-SA 4.0 |
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| Dec 12, 2018 at 21:29 | history | answered | Andy aka | CC BY-SA 4.0 |