designing a low pass filter for inverter

[--BawA--]

i am working on smps based inverter, i have successfully made a hbridge circuit driven by PIC16f877a , this mcu is generating 16khz spwm signal of fundamental frequency of 50hz,, i want to design a low pass filter for the hbridge output in order to get a clean sine wave .. so how to proceed? , i mean which type of filter should be used? ,, which componenets should be used and also calculations required to design the filter ??

 

[Jakie Ee]

use lc low pass filter..easy

the cut off frequency should in range between fundamental and switching frequency...

 

[--BawA--]

i have used 47uf electrolytic capacitor and 40uh inductor, but as i connected this filter to my hbridge, my osfets blown out,, what was the reason behind that,, i have also used film capacitor in place of electrolytic capacitor, but again mosfets blown, , ,,, what should i do now?

 

[Jakie Ee]

check the rating..
or
use ac capacitor..

 

[FvM]

i have used 47uf electrolytic capacitor and 40uh inductor

Impedance of the 40 µH inductactor at 16 kHz is about 4 Ohms. You didn't yet mention inverter output voltage and current rating, but I guess the maximum current will be already exceeded by the reactive current...

 

[--BawA--]

Thanx fvm for ur reply.
My inverter can handle max output of 350watts, 220v.
But I have some doubts
1) how to decide the appropriate impedence to design my filter?
2) should I keep the high impedence filter in my design?
3) what is the role of input and output impedence in filter?
Plz tell me in detail.coz I m designing this type of filter 1st time n till now due to wrong filter implementations my 12 mosfets hve blown .
Plz suggest me a way..

 

[--BawA--]

I am still waiting for your reply.

 

[FvM]

You know that I have told my design method in your other thread.