Help me fix circuit with TL783

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bomba

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What is wrong with this circuit? It doesn’t work....

Thanks in advance

PD: I was implemented this circuit before with other transistor and posted the problem here
 
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tl783 heat or hot

What do you mean by it's not working? It does not regulate, it produces no output, etc?

The BUT56 is not really suitable for this application. I would select another transistor. Also, I noticed that R3P is now 6.8k, instead of 1k.

I still do not know the answer to the original problem. Does the TL783 seem to be still functional? I mean, after burning those resistors, one could expect the IC to be questionable.
 

Re: Help Me!!!!!!

Have you looked at the output with an oscilloscope? As the output current increases, the boost circuitry turns on, dramatically increasing the loop gain and adding another pole(s) into the feedback loop. I think it will oscillate, which could easily overheat your resistors.
 

Re: Help Me!!!!!!

VVV:
The regulator is working fine, without the current booster. The problem is, when I connect the current booster the BUT56A became short-circuited between Collector to emitter. Why you say that the BUT56A is not for this kind of application.
I need to replace the tip30c for another transistor that can support more than 100V VCEO, because with the other configuration, the circuit work fine since the V-Regulated be greater than 40V, down this voltage the VCO through Collector emitter of TIP30C became Greater than 100V, and this problem burn the resistors.
I change R3P because the HFE of 2sa1837 is greater than the HFE of tip30c.

I need to generate a regulated voltage 10-120V, with 3A deliver capability, using the tl783 regulator.

Thank you
 

Re: Help Me!!!!!!

10kangstroms:

The output is stable in the circuit with tip30c and tip152. In the configuration above posted the output is stable at the higest voltage than can deliver the regulator, and the resistor become very hot.

Thanks
 

Help Me!!!!!!

hi bomba.
I have checked the datasheet of TL783, do you have the output capacitor?
Maybe you can increase the output capacitor value and add a small resistor connecting the emitter of Q3p and the OUT pin of TL783 to help stable the current flowing throw Q3P.
 

Re: Help Me!!!!!!

marshel:

I have a 3000uF capacitor conected to output.

Thanks
 

Re: Help Me!!!!!!

So what about quasi-LDO structure?
I think maybe you can change your exertnal circuit like that.
 

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