Electronic – How to reduce noise in SMPS (Switching mode power supply) circuit


I am just using a reference design of SMPS (from Microchip) to boost input voltage from 12V to 90V as the image below:
enter image description here
It's working normally but the problem is the noise at the output of 90V.
I measured the amplitude Vpeak-peak of noise around 150mV and the repetition frequency is 110kHz = switching frequency of HV9110 controller.

My question is how can I reduce this noise to 20mV because it will affect on my signal analysis.

Please help me and thanks in advance!!!

Best Answer

For the Boost convertor like other convertor you have output ripple and EMI. For output ripple reduction the best way is adding a good CLC filter. Increasing the value of C12 and C16 could have direct effect on your output ripple. For the EMI reduction adding an Snubber RC circuit over the D8 diode or from its anode to ground is also a good practice. Reducing the switching speed of M3 also has direct effect on the generated EMI.

Please look at the following document:


Texas Instrument document "slva790" is also a good guide for EMI reduction.