Electronics > Repair
18V/3A HY1503 PSU - weird CC/CV behavior while charging battery cells
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xavier60:

--- Quote from: xavier60 on September 19, 2024, 09:25:29 am ---I'm using an LM358. Even a 1000pF across the input only caused a small amount of ringing.
With a 470pF and 2.2K, mine settles in 10us.
That high frequency ringing could be coming from the wiring to your shorter.

--- End quote ---
The test isn't valid as I had omitted R6. With R6 fitted, ringing becomes noticeable with 470pF across the inputs, so not a problem anyway.
This capacitor is likely to prevent RF getting into the opamp, rather than compensation related.

Edit: I can't see any useful purpose of putting a capacitor between pins 5 and 6 on an LM741.
iMo:
Spent a half day with the CC. When it engages the output of the 324 oscillates 0.5Vpp at aprox 2MHz.
I have not found a way how to calm it down..
PS: talking real hw..
xavier60:
 CC loops are usually well behaved. What compensation values are you using and what has been tried?
iMo:
The aprox 2MHz signal at the psu's output is below 40mVpp with active CC, and the CC basically works.
There is a clean signal when CC is set off. Oscillation is visible in entire active CC region.
The original is 120pF in the fb.Tried blocking the inputs, various RC combinations in the feedback (C from 330 to 6n8, R 0/1k/4k7/10k), 22 ohm resistor at the opamp's output, messing with wiring layout, etc. The amplitude at the output of the opamp decreases perhaps by 30% with larger values of caps. The third and fourth opamp in the package is clean, supplies clean. The oscillation is of course visible everywhere with low amplitude as it is boosted by the transistors.
PS: the 1k or 100ohm in the BE of the 2N3055 has no impact on the amplitude.
xavier60:
That's puzzling. The CC opamp is configured as a Miller Integrator which is a low pass filter. With say 1nF and 10K, the attenuation would make a 2MHz signal barely visible if at all at the output of the opamp.
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