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Voltage controled variable resistor?

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carpenter

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Hello ,
I have switching power supply (130kHz) adjust for variable output voltage. 5-50V 150W max
Now I have in regulation loop potenciometer instead R12 on picture.
I would like the loop was adjusted so that the output voltage to control processor, such as a voltage 0-5V.
I have no idea how to do it your advice?

VCR.jpg
 

FvM

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A controllable resistor would be a theoretical (or an unimaginative) way to implement a variable output voltage. Adding a variable voltage to the voltage divider is a smarter way, I think.
 

carpenter

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VCR I said just like the basic idea, not against anything.
Can you expand on the idea with additional voltage in divider?
Do you support the R13 control voltage?
 
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Have a third resistor connected to the TL431 sense input and a variable voltage between ground and the resistor. Then you can play around with resistor values that give the intended control range. I presume you know, that the control loop tries to achieve a voltage of 2.5V at the sense pin.

The control voltage operation will be inverted, increasing the voltage reduces the output voltage.
 
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