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# low pass filter design of an inverterusing a single inductor and capoacitor

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#### gedza

##### Junior Member level 2
Can you please help me with the formulas to design a simple lc filter inductor and capacitor values .The switching frequency is 20khz and cutoff is 5khz .The out put frequency should be 50khz.

Can you please help me with the formulas to design a simple lc filter inductor and capacitor values .The switching frequency is 20khz and cutoff is 5khz .The out put frequency should be 50khz.

Before starting the design of a filter, of course, one should know and understand the corresponding requirements (filter specification).
Therefore my question: Do you understand the meaning of the mentioned data (20 kHz, 5 kHz, 50 kHz) ?

The specification sounds more reasonable if you put in 50 Hz output frequency.

By saying single L and C, you have already selected a filter topology, the cutoff frequency implicitely sets the product L*C. But to define the actual L and C values you need to know the load and source impedance and intended filter Q, respectively a corresponding filter prototype.

Unfortunately, an inverter has a variable load impedance, so you can at best design the filter based on a typical load case, preferably nominal load.

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