Buck Converter controlled with a PWM

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IvanR10

Joined Mar 24, 2016
1
I am trying to make a buck converter that will step down a 9v input into 7-2v output using an MC3406 or LM2596 ( or any other chip really as long as it works). Is it possible to override the feedback pin on the chip by passing a PWM signal from an Arduino through an RC low-pass filter and into the feedback pin using a op-amp buffer. Ive physically tried it using an LM317T and it works, but when i use the MC3406 the voltage at the output drops when i add a load and just seems very unstable. I heard that its possible on the LM2596 but i havent tried it...im waiting for them to come in the mail.
Any suggestions would be great. My next move is to try an use a digital pot to set the feedback resistors on the MC3406.
 

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Alec_t

Joined Sep 17, 2013
14,280
You could try using the PWM for rapid switching of R1 to ground, so that the 'average' resistance is effectively changed.
 
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