250 to 5000 watts PWM DC/AC 220V Power Inverter

The schematic circuit design is for a 250 watt output, while the pics are of my 1500 watts inverter that i built, to increase the power of the circuit you have to add more of the Q7 and Q8 transistors in parallel, each pair you add will increase your power by 250 watts, ex: to get 750 watts of power from the inverter you need to add in parallel 2 of Q7 and 2 of Q8 to the original
250 to 5000 watts PWM DC/AC 220V Power Inverter - schematic

design. 2> If you increase the power transistors you have toenlarge the T2 transformer to match the new needs, the circuit`s transformer is rated 25 amps to handle 250 watts of 220v, for every 1 additional amp you need on the 220v side you have to increase 10 amps on the 12v side, of course there are limits to the thickness of the winding so if you need more than 750 watts i recommend that you use a 24VDC supply instead of 12 volts: 4> R2 is to set the frequency to 50 or 60 Hz (R2 range is between 40Hz to 75Hz), so guys that do not have a frequency meter are advised to blindly put this variable resistor mid-way which should drop you in the range of 50~60 Hz. in our case to get a 50Hz output we remove both the 100K and the variable 100K both from pin 6 and we put instead a 260K fixed resistor and we leave the 0. 1uF (the 104 cap) as it is, this change should give out a fixed 50Hz as per the formula : But in reality it will not exactly give 50Hz because the 260K resistor has a specificerror value marginso does the capacitor, that`s why i recommend a variable resistor so that accurate calibration can be achieved. 5> Use either tantalum or polyester film "as in pic" for the 104 caps, ceramic disc caps change value once hot and this in turn changes the frequency of the inverter so they are not recommended. 6> Pin 10 of the SG3524 can be used to auto shut down the inverter, once apositive voltage isgiven instead ofnegative to...

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