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Half-Bridge 0-30V, 0-20A Feedback loop problem

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xavier60:

--- Quote from: paladyn on July 01, 2019, 12:18:03 pm ---The switching frequency is 40kHz, while the gate resistors have probably 12 ohms in parallel with the diode. The question is whether 220ohm is not too much? Of course, I can solder and check, but it will definitely affect the amount of heat released.

You used 5.6k and 1uF feedback, tell me how did the inverter work? Have you noticed any squeals of the transformer or noise at the output from the inverter?

--- End quote ---
220Ω would make the IRFP460  too slow. I can't say what the  IRFP460 would need to slow it down by the right amount.
With the  5.6k and 1uF in the feedback, ,mine was stable, just slow with no transformer noises except at low output voltage and no load for reasons that I explained earlier, not a real problem.

xavier60:
Also consider bridging out D8 in case noise is getting in after it.

paladyn:
Yesterday I installed a new TL3474CDR operational amplifier, it is a little better, you can see the difference but still the transformer is squeaking and there are considerable distortions.

I checked the situation again with common mode choke on the output of the inverter and on the same core I wrapped 5 scrolls from Umes. Unfortunately, there are even more distortion on the output waveforms.

I'm wondering if diodes D8 and D9 are really a problem here. Maybe too big capacity? There is also the issue of choke and feedback. I wonder how much CCM or DCM work mode is important in calculating the feedback loop coefficients.

xavier60:

--- Quote from: paladyn on July 03, 2019, 06:30:06 am ---Yesterday I installed a new TL3474CDR operational amplifier, it is a little better, you can see the difference but still the transformer is squeaking and there are considerable distortions.

I checked the situation again with common mode choke on the output of the inverter and on the same core I wrapped 5 scrolls from Umes. Unfortunately, there are even more distortion on the output waveforms.

I'm wondering if diodes D8 and D9 are really a problem here. Maybe too big capacity? There is also the issue of choke and feedback. I wonder how much CCM or DCM work mode is important in calculating the feedback loop coefficients.

--- End quote ---
Because you are testing the CV loop only, it would be ok to connect the output of the op-amp directly to the Comp pin 9 of the SG3525,
Are you using the simple compensation that I described earlier?
I did not think about  CCM and DCM. If there was a loop problem with DCM, it would happen only at low loads.
I would like to see  how you are applying the Common Mode Choke.

EDIT:  No more than 5V should be applied to the Comp pin 9 of the SG3525. It only needs 3V for full duty cycle.

paladyn:
I will try to do some pictures today how it looks. See how the common mode choke and the rest. You write to connect the loop amplifier to pin 9 SG3525, but what to do with the SG3525 amplifier inputs? I could simply desoldute the coupler adding diodes and solder the loop amplifier to pin 9 to leave the internal SG3525 amplifier as it is today, i.e. a voltage follower (pin 9 connected to pin 1).

As for compensation according to your description, I only tried without a C1 capacitor. Do you suggest using compensation as you did in the first post? Should there be voltage feedback? Possibly, could you suggest some element values to start with for testing?

My loop is adapted to 3V voltage.

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