Modifying a 12V SMPS for variable voltage.

I required a
variable power supply for my lab test bench. But all the power supply which I saw
in the market is a linear type. They have poor efficiency and dissipate more power. So
I decided to modify a readily available 12V 10A SMPS in the metal cabinet to
get the variable voltage. Although it already has a potentiometer to change the
voltage that goes from 10.5 V to 14 V only.

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The power
and the voltage requirements were all favorable for me but the voltage was
not. So I was only required to change the feedback loop components to get the
variable voltage.

The feedback
loop consists of a voltage divider which senses the output voltage and provides
the error voltage to the controller. Now I replaced the feedback components
with the diagram as shown.