Half bridge dc-ac converter 12VDC-220VAC/50Hz

[jean12]

Hello,there can anyone help me to correct my circuit here so I can get 220VAC at the output with the main source at 12VDC which has passed through a push pull and gives 440VDC;so help me to convert that 440VDC into 220VAC/50Hz.

When measuring the output with LC filter of 2.2mH and a capacitance of 0.47uF I am getting a high DC component and a very low AC component,Please help me.


The code I am using for getting the SPWM to ocntrol the MOSFET are here

unsigned char sin_table[32]={0, 18, 36, 54, 72, 88, 104,
119, 132, 145, 155, 165, 173, 179, 183, 186, 187, 186,
183, 179, 173, 165, 155, 145, 132, 119, 104, 88, 72, 54, 36, 18};

unsigned int TBL_POINTER_NEW, TBL_POINTER_OLD, TBL_POINTER_SHIFT, SET_FREQ;
unsigned int TBL_temp;
unsigned char DUTY_CYCLE;

void interrupt(){
     if (TMR2IF_bit == 1){
        TBL_POINTER_NEW = TBL_POINTER_OLD + SET_FREQ;
        if (TBL_POINTER_NEW < TBL_POINTER_OLD){
           CCP1CON.P1M1 = ~CCP1CON.P1M1; //Reverse direction of full-bridge
        }
        TBL_POINTER_SHIFT = TBL_POINTER_NEW >> 11;
        DUTY_CYCLE = TBL_POINTER_SHIFT;
        CCPR1L = sin_table[DUTY_CYCLE];
        TBL_POINTER_OLD = TBL_POINTER_NEW;
        TMR2IF_bit = 0;
     }
}
void main() {
     SET_FREQ = 410;
     TBL_POINTER_SHIFT = 0;
     TBL_POINTER_NEW = 0;
     TBL_POINTER_OLD = 0;
     DUTY_CYCLE = 0;
     PR2=187; ///for 16Khz at 12MHZ of quartz
     TRISB=0x3F;// PWM output pins
     CCP1CON = 0x4C;
     TMR2IF_bit = 0;
     T2CON = 4; //TMR2 on, prescaler and postscaler 1:1
     while (TMR2IF_bit == 0);
     TMR2IF_bit = 0;
     TRISB=0; //defined my self for PWM out
     TMR2IE_bit = 1;
     GIE_bit = 1;
     PEIE_bit = 1;

     while(1);
}

I am using a PWM signal as shown in snapshot.

Please help me .

Thanks.

 

[andre_luis]

The values of L-C components you are you using produces a resonant circuit of a frequency ~4,95KHz, much above desired 50Hz output.
Take a look on that calculator and try perform selection of other values so that fits closest:

https://www.daycounter.com/Calculators/LC-Resonance-Calculator.phtml


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[jean12]

Is it possible that with a PWM signal like the one I am using I can get a pure AC voltage at the output??

Please help me to know how with that calacultaor I can get 220VAC/50HZ the input is 440VDC and the switching frequency is 16KHZ.

Please help.

THANKS.

 

[andre_luis]

This calculator tool were suggested for select an approximation for output filter value.
Once it is desirable let transfer 50Hz and eliminate 16KHz switching frequency, you must consider 50Hz for calculation.

Once still remains 2 variables to insert on calculator ( C , L ), you must set someone for choose another.
Generally C is candidate for 1st selection, due cannot be tuned as transformer can be on its windings.



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[jean12]

so how may I proceed for getting the 220V/50HZ?

 

[andre_luis]

so how may I proceed for getting the 220V/50HZ?

As mentioned above, the L-C values ​​you informed may be oversized, causing a dampening effect on output voltage, because the frequency of resonance on this net is far beyond the operating frequency of 50Hz.





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