Noise in ADC Voltage sensing of Boost Converter

[basit701]

Hello Guys!

I am working on feedback of a Boost Converter (40V to 370V) using microcontroller. For voltage sensing i have employed potential divider technique to lower down the value to 200mV when Vout is 370 which is then to opto isolator (HCP 7800. The driver is linear if Vin is below 200mV). The output of isolator is then fed to ADC of the microcontroller. However the ADC readings have fluctuations. I checked the signal on the oscilloscope and to my surprise there is some noise the isolator output. I tried to filter that noise using 3rd order Low Pass Filter with cut off 10Hz but its still there.

After failure with Low Pass Filter i think the noise in the output is common mode noise, is it???

Sensing circuit is patched on breadboard.

Isolator Circuit Schematic


Isolator Output





Boost Converter Output (at 290V)

 

[KlausST]

Hi,

I assume this is not a schematic problem, but a PCB layout problem.
--> Post your PCB layout.


Klaus

 

[basit701]

Hi,

I assume this is not a schematic problem, but a PCB layout problem.
--> Post your PCB layout.


Klaus

Here is the PCB design. I have not design the PCB of opto isolator circuit (currently implemented that part on BREADBOARD).