Power Inverter With Feedback For Voltage Regulation

Two things mostly inspire some of my design, it is either I need it personally or someone asks of it. The former led to this design as my former inverter could no longer meet up with my load demand and desire constant output voltage for my highly voltage sensitive appliance. In this inverter circuit, I introduce feedback circuitry for voltage regulation by modulating the pulse width of the oscillator output. When the there is a change in the voltage of the inverter battery, the rms value of the AC output voltage changes. When the load increases, voltage drop across the transformer winding increases, hence drop in the rms value of the AC voltage.
However, the feedback circuitry in this inverter circuit senses the changes, and sends the feedback to the oscillator which in return adjusts the width of the output pulse to stabilise the AC output. To really understand how this works, you can check the datasheet of oscillator IC used, SG3524.

 

The transformer use in this inverter has core dimension that give core-area equals 4860 square-mm and window area equals 2187 square-mm and can deliver power of about 1.2KVA. It is a center-tapped transformer and has winding ratio 11-0-11/300. 11/300? Yes, because the design is to deliver a modified sine-wave AC voltage output. You can use the transformer design calculator for your transformer design.

 The values of the electronic components used are well detailed in the circuit diagram. Where precision is needed to get the right value, I replaced fixed resistors with variable ones so as to adjust to get the appropriate value. VR1 is to set the frequency, VR2 to set the desired regulated AC output voltage and VR3 to set the BLVS (battery low voltage shutdown).