CataM
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Hello everyone,
The output LC filter design is made by knowing the desired output voltage ripple and ripple current desired (e.g. in the buck converter), which means, we do not design the filter based on its frequency domain characteristic, which is how we are been though filters are designed in analog electronics.
That LC low pass filter in the output stage of a converter is simple to make because the output is assumed to be DC, and hence, the time domain characteristics are easy to determine.
My concern is, when trying to design a filter, but the time domain is difficult to determine (unlike the output stage of a DC/DC Converter e.g. Buck), we should employ the standard filter techniques from the frequency domain.
Consider e.g. the design of an 2nd order LC low pass filter for a full bridge rectifier. If one uses the frequency response of the filter and let us say that the cut off frequency is 1/10 of the fundamental frequency, how should one select the capacitor and the inductor ? If the cap is too big, the inductor is small and then the ripple current is big and hence lot of power dissipation.
The point I am trying to make is that one should relate the filter components to the time domain response as well, e.g. overshoot, no overshoot, slow response etc..
Should one go and select components by intuition, or go and follow the procedure of the normalized filters responses (Butterworth, Chebyschev, Bessel...) ?
Any comment is appreciated !
Thank you for your time !
The output LC filter design is made by knowing the desired output voltage ripple and ripple current desired (e.g. in the buck converter), which means, we do not design the filter based on its frequency domain characteristic, which is how we are been though filters are designed in analog electronics.
That LC low pass filter in the output stage of a converter is simple to make because the output is assumed to be DC, and hence, the time domain characteristics are easy to determine.
My concern is, when trying to design a filter, but the time domain is difficult to determine (unlike the output stage of a DC/DC Converter e.g. Buck), we should employ the standard filter techniques from the frequency domain.
Consider e.g. the design of an 2nd order LC low pass filter for a full bridge rectifier. If one uses the frequency response of the filter and let us say that the cut off frequency is 1/10 of the fundamental frequency, how should one select the capacitor and the inductor ? If the cap is too big, the inductor is small and then the ripple current is big and hence lot of power dissipation.
The point I am trying to make is that one should relate the filter components to the time domain response as well, e.g. overshoot, no overshoot, slow response etc..
Should one go and select components by intuition, or go and follow the procedure of the normalized filters responses (Butterworth, Chebyschev, Bessel...) ?
Any comment is appreciated !
Thank you for your time !