Electronics > Repair
18V/3A HY1503 PSU - weird CC/CV behavior while charging battery cells
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xavier60:
I added CC to my mock-up. Works fine with 10K for the compensation resistor and even with no capacitor.
I by chance noticed that the 470pF across the CV opamp inputs was causing a 200KHz oscillation at higher currents. No problems with 120pF.
iMo:
This is 324's CC output with 120pF feedback (in mid of the CC range).
CV wired as in the above schematics.
When I disconnect its output from the 1N4007 output gets clean.
xavier60:
Try the 6n8 and 10K. The attenuation will be about 1000:1 at 2MHz. The only possible reason I can think off so far is that somehow there is too much inductance in series with the CS resistors.
xavier60:
I tried putting 200mV p-p of 2MHz through my output stage. Most of it gets blocked by the 10 ohm resistor at the Base of the 2N3055. I see about 10mV at the output.
What are you loading with?
iMo:
The 10k ser 6n8 increases the amplitude almost twice (500mVpp).
The load is a 10W ww (a white ceramic brick) resistor on aprox 80cm lab wires.

The only thing which lowers the amplitude significantly (10x) is when I put my finger at the 324 output..  :D
So there is a HF coupling somewhere.

My o'scope is isolated via a trafo, but connecting its ground with psu's earth does not help.

The probe is a Tek probe, 10x, grounded to the ground of the schematics.

The tracks around the opamp were cut, the 3 red wires are in+ in- and out of the CC opamp. Rearanging them does not help.
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