Electronics > Projects, Designs, and Technical Stuff
Half-Bridge 0-30V, 0-20A Feedback loop problem
paladyn:
The connection I mentioned is in the schematic of the power supply, which I put in the attachment.
xavier60:
--- Quote from: paladyn on July 26, 2019, 11:49:02 am ---The connection I mentioned is in the schematic of the power supply, which I put in the attachment.
--- End quote ---
I don't understand the description, another language of some sort.
He is possibly trying to partly cancel 66Khz ripple that's getting into the error amp.
Something looks odd with the MOSFET Gate drive transformer. I think that the high-side MOSFETs would get half of the drive voltage.
paladyn:
I made an experiment and connected pin 1 to pin 5 (SG3525) with an adjustable resistor 500 kohm, no visible effects.
EDIT:
I just realized what a blunder I made.
After all, I do not use the error amplifier in the external SG3525 only. Maybe you would have to connect pin 5 to the COMP9 pin output
xavier60:
Does it run smoothly by controlling PWM by applying filtered DC to pin 2 of the SG3525's error amp?
paladyn:
Does it run smoothly by controlling PWM by applying filtered DC to pin 2 of the SG3525's error amp?
pin 1 and pin 2 of the SG3525 system are not used and not connected. Pin 9 is connected to an external operational amplifier that realizes the loops.
I am using an external operational amplifier, but yesterday I did a test where I connected an adjustable 500kohm pin 5 resistor with pin 9 of the SG3525 chip
I must admit that I did not notice the difference in the operation of the inverter. At a small value of the resistor some soft anomalies already appeared in the noise at the inverter output and I stopped reducing the resistances.
Overall, I noticed that the problem occurs when SG3525 can no longer reduce PWM because it has almost reached zero. Perhaps the use of a huge choke would help?
Summing up the problem of squeezing the transformer occurs mainly at low resistance loads and low output voltages.
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