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Is this a TL431 self-oscillation?

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jigshaw

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Hi ,guys
Recently I have met a problem with 48V power supply.
I used a TL431 as regulator.
The figure blow is the schematic.I simullated in Multisim.It worked well.
Sch.jpg
But after I soldered the components on board, the output gave a big ripple(200mV Vp-p,4Hz).
I used an oscilloscope and detected a big pulse with the same frequency as the ripple at Q1-Base(As following figure shows).
tek00000.png
Is this a self-oscillation?
How to fix it?
Thanks a lot.
 

Hi,
You may please load the circuit, I think osci will stop.
Also you can try keeping RC b/w pin 4 and pin 3 of tl431
 
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    calin

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I think the latch you used at the gate of Q1 is of very high current gain. Try to increase the resistnace R3 (470 ohm) to a 1 kohm or so. and use a capacitor of 1 pF at the gate (sorry base) of Q1.
 

Thanks for your suggustions.
I would try it later.
 

With other's help,this problem was solved.
Place a ceramic parallel with R6，because the amp in TL431 could not drive load with big capacity.
 

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