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Power/Renewable Energy/EV's / Re: SMPS input filter cut off frequency
« Last post by mtwieg on Today at 12:40:22 pm »The reasoning is likely as follows:
The power supply's control loop will attenuate line disturbances below the controller's crossover frequency.
The LC filter will attenuate disturbances above its cutoff frequency.
In order to attenuate disturbances at all frequencies, then these two bands should overlap, thus the LC filter fc should be lower than the controller's crossover fc.
Of course, whether this is actually worthwhile is very application-specific.
For example, if your primary concern is just passing EMC tests, then there's not much reason to attenuate below 150kHz (or whatever the lower test frequency your device requires).
The power supply's control loop will attenuate line disturbances below the controller's crossover frequency.
The LC filter will attenuate disturbances above its cutoff frequency.
In order to attenuate disturbances at all frequencies, then these two bands should overlap, thus the LC filter fc should be lower than the controller's crossover fc.
Of course, whether this is actually worthwhile is very application-specific.
For example, if your primary concern is just passing EMC tests, then there's not much reason to attenuate below 150kHz (or whatever the lower test frequency your device requires).