4/10/2024 0 Comments 12v product pi filter designPrescaler 1:1 Postscaler 1:1 TMR2 Preload = 249 Actual Interrupt Time : 62.5 usĬCPR1L = (sine_table & 0x3FC) > 2 ĬCP1CON.DC1B0 = (sine_table & 0x01) ĬCP1CON. So, I decided to use same values as I have also calculated same values. I choose C = 2.2uF 630V as it is easily available and L as 3.3mH 6A type.įc = 1/(2*3.14159265*sqrt(3.3*2.2*10^(-9))) = 1867 Hz which is close to 1.6 KHz.Īlso, i referred the attached circuit of commercial EG8010 based Inverter and its switching frequency is around 24 KHz and they are also using 3.3mH and 2.2uF for the output filter. My switching frequency is 16 KHz and so, I can choose fc = 1.6KHz It says, fc can be 1/10 of switching frequency and also it tells fc = SQRT(fo * fpwm) Still getting 1.7mH and 1823uF for fc = 90Hz. I think the above equation which I took from here are wrong. What is the work around ?Ĭharacteristic Impedance of Inverter = 220/2.27 = 96.916 = approx 97 Ohms If I keep L small then C increases and I can't get C in Non-Polarized Capacitor type. I can't increase L much because amplitude of the output will decrease. Is 10mH and 330uF values ok ? I chose cutoff frequency as 90 Hz. I can't get more than 4.7uF Non-Polarized Capacitors. If C value is greater than 4.7uF then I have to use two electrolytic capacitors connected back to back. If I choose L as 3.3mH and fc as 90 Hz then C value increases greatly. How can I eleiminate it to get pure sinewave ? I am using IRF840. I know the distortion at ZC is due to Mosfet. Now, I changed the inductor and capacitor values and I am getting this signal at the output. ![]() Another is I am using 12V to 220V step-up output iron core transformer at the H-Bridge output. One is based on DC-DC Converter with switching transformer to get 325V DC VBUS voltage for H-Bridge from 12V Battery voltage. The pi filter is not suitable because of the poor voltage regulation of the filter, and this is because the output voltage rapidly drops along with the increase in current through with the load. I am actually making two versions of the Inverter. The pi filter is an LC passive filter which can be a low pass or high pass filter depending on the design or configuration of the filter. In both I am getting this distorted signal. ![]() I am attaching my Proteus simulation file. SPWM is ok because if I connect RC low pass filter then I get pure sinewave output. I need 50 Hz fundamental sinewave output. My SPWM frequency is 16 KHz and so I chose cutoff frequency for filter as 3 KHz. Please tell me how to design a good LC output filter. The issue is I am not getting sinewave signal at the output. I am using 12V Battery voltage to 325V DC VBUS voltage DC-DC Converter (not shown in simulation). I have designed a true sinewave inverter for single phase 220V 50Hz. True Sinewave Inverter - Output LC filter design help needed
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