All,
I am looking to design a low pass filter that has a cutoff frequency of 20 kHz. The filter needs to be able to handle about 20A of current so the dir ection I have taken is an LC filter. (Inductor with a high current rating).
I simulated the low pass filter tonight (LTspice) using the values of 7.9 u H and 15 uF suggested from some of the online lowpass filter calculators.
From the simulation I see 0 dB in most of the passband but then I see a hug e resonance point of +32 dB at 14.49 kHz!
Here is a link to the simulation result:
1.) Is there a way to eliminate this resonance?
2.) Is there a different filter that would have less peaking but still able to handle the high current for this application (20A)?
3.) There is an H-brige that will be modulated at 200 kHz (pwm) and this wi ll going through the 20kHz lowpass filter to given a DC voltage without all the pulses. If the resonance point is kept as it is what type of issues w ould this cause? Is this even a problem?
4.) From the simulation I see a cutoff frequency of 22.7 kHz instead of 20 kHz. What is the best way to tune this? Maybe to keep the capacitor fixed (
15 uF) and then sweep the inductance value in simulation?
Thank you you so much for your thoughts.
-Mike