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so it appears a large input capacitor (C1) is both good for stability and EMC reductionġ) Does this sound correct, or am I out in left field again?Ģ) If I have two of these SMPS both running at about 350kHz, is there any reason I can't feed both from one filter? I'm mostly concerned with impact on stability of the SMPS's. This application note presents design techniques that reduce conducted EMI emissions in TOPSwitchpower supplies below normally specified limits. Improper conducted emission level estimation leads to changes in the layout and the schematic of the device, which entails additional costs or increase the module development time. if large the peak disappears, and the resonant peak shifts down slightly. A Pi filter consists of Inductors and Capacitors (3 in total) arranged in a configuration. if too small say 3uF the resonant peak starts to grow significantly and fr shifts up slightly the filter seems quite effective >50dB 370kHz 28 proposed the use of an inductor, choke, and pi filters to reduce the CM and DM noise of conducted EMI. it was based on the analysis of conducted EMI, which had been induced by a DC-DC converter. makes we wonder if its not wise to add a small value resistor in series with Cd to allow for control of Q just in case stability issues arise?Ģnd simulation is looking the other way, how much of the 370kHz noise from the converter makes it back out to the line? High power density is the primary design consideration for power converters in more electric aircraft (MEA) to meet both space and weight requirements. A new EMI-filter design method based on the optimization of stray elements was proposed, and. ESR of C2 has very significant effect on the Q of the LC. For this reason, the input filter has to be adjusted to be more effective. In case, the filter is not effective enough, the conducted emission test will fail and the designer has to improve the design regarding conducted emissions. Essentially, an EMI filter is an electrical device/circuit that will help mitigate the high-frequency electromagnetic noise present on the power lines as well as on signal lines (Fig. I ran a few simulations and this is what I observed:įirst simulation is the response of the PI filter in the RECOM document with input and output as shown. Conducted Emission (CE) Test and is part of the defined standard like the CISPR standard. I'm starting to get a better feel for this.