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Part Number: UCC28950
We are developing DC-DC PSU with input voltage range 600-800VDC and output voltage 60VDC@10А using UCC28950. With asinchronous rectifier system works without problems, but power dissipation is too high.
With sinchronous rectifier we got a problem: when SR starting to work we gets a huge noise on all nets - on output, on control nets and even UCC28950 power input. As result, it kills controller. What can cause it?
Oscillograms with enabled SR:
2, 3. Output with asynchronous rectifier without load
4, 5. Output with asynchronous rectifier loaded with 1A
6, 7. Output with SR enabled after stabilization started (load 1A)
In reply to Roman Zavyalov:
Sorry, with SR oscillograms I've took second signal from wrong point. Here's correct images for SR.
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In reply to Colin Gillmor:
That oscillograms was made with low input voltage. We can make previous oscillograms with high input voltage (around 500V, when SR starts to work; above 500V UCC28950 is dying) if needed. Can that plots be usefull?
Today, when we tried to check one theory, we accidently killed UCC28950, so we will make oscillograms tomorrow. Also, unfortunately, rigth now we can't make oscillograms from primary side because we don't have high voltage probes.
I think that the first thing I would like to confirm is whether you have the OUTx signals connected correctly. Ideally, I'd like to see a plot showing the voltages I mentioned in the last post.
However a plot showing OUTA DA1, OUTB DA1, PIn 7 U3 and Pin 5 U3 would do that. They are all low voltage signals and have the same ground reference. You can take this plot at any input voltage where the SRs are active
Top to down lines:
Vin 0V 4 periods
Vin 40V 4 periods
Vin 150V 4 periods
Vin 250V 4 periods
Vin 350V 4 periods
Vin 450V 4 periods
Vin 530V 4 periods
Vin 550V 1 period
Vin 550V 4 periods
Vin 550V 6 periods
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