Electronics > Projects, Designs, and Technical Stuff
Half-Bridge 0-30V, 0-20A Feedback loop problem
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xavier60:

--- Quote from: paladyn on June 11, 2019, 08:53:17 am ---Do you have a proven material, article or book from which I could calculate the value of the compensator for transconductance mode?

--- End quote ---
This might mean something to someone, http://www.ti.com/lit/an/slva662/slva662.pdf
From experimenting with mine I found that the Type III compensator was not necessary for good stability, it gives faster response than the Type II.
MagicSmoker:

--- Quote from: paladyn on June 11, 2019, 06:12:22 am ---...
I have a problem matching the feedback of the SMPS converter itself. At low power (100W) the transformer starts to beep loudly. Perhaps this is because the transformer has not been stuck together and the windings fall into vibration?
...
I also noticed that the current feedback loop works worse than the voltage loop. The only thing that is different in these loops is an additional operational amplifier INA213, which strengthens the shunt voltage. ...

--- End quote ---

All this suggests that noise is coupling into the feedback pathway, causing instability. The most likely source of such noise is switch and/or diode junction capacitance resonating with stray/leakage inductance at device turn-off. Besides snubbing the likely culprits, good board layout is the ideal cure.
xavier60:
The op's DSO photos can be found here, https://www.edaboard.com/showthread.php?384844-Half-Bridge-0-30V-0-20A-Feedback-loop-problem&p=1653014#post1653014
There appears to be 100Hz ripple rather than loop instability.
Although it doesn't explain the transformer squealing sounds.
As with my experiences, all that hash makes  SMPS  debugging messy.
paladyn:
xavier60

Yes, this is a parallel topic to get a broader spectrum of information. At edaboard, I added some graphs of how the output and input waveforms look like.

The most confusing thing for me is that the theory was described in the book

Switching Power Supplies fromA to Z - Sanjaya Maniktala and article https://www.biricha.com/uploads/8/9/8/0/89803127/foundations__part2.b__2.pdf


is quite agreeable with each other. Despite the calculation of coefficients according to the patterns, the output curves are quite poor. I do not know if the problem lies in calculations or maybe somewhere in hardware.

edaboard and eevblog are the last places I ask for help. Despite the size of the internet, people just do not do such things. Today, he goes to the store and buys a regulated regulated power supply, and does not sit at home and combines how to do it.
xavier60:
Although I got my project to work properly, I did the  compensation by trail and error. I found that the values were not too critical.
I don't understand the formulas and calculations.
Mine runs at 40Khz also. The inductor is about 80µH and 6000µF of output capacitance.
While I was debugging mine, I directly connected the live side ground to the output side ground, I was powering through an isolation transformer of course. This greatly reduced to amount of hash. Later, I mounted the PCB on a metal plate and made the grounding connections to the plate. I can't remember how much this helped in reducing the hash.
 I'm still curious to know the result of removing R1.
The 100Hz ripple seems to indicate too little gain near 100Hz.
Check for missing pulses by doing single shot captures.


 
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