A power inverter circuits is normally designed to meet its design specifications when the applied input DC voltage is within specified tolerance limits. Thus, single input inverters are usually specified to work from a DC source having a fixed nominal voltage. This limits the usefulness of the inverter circuit when a DC source having the specified nominal voltage is not available. In this work, a modified square wave inverter system that is specified to work properly from batteries with nominal voltages of 6, 12, 18 and 24 V was designed. A model of the microcontroller-based circuit was developed with Proteus® software and its firmware was written in C language using the MicroC® development tool. A prototype of the circuit was constructed and then tested. The constructed circuit was found to work properly by producing a 50 Hz modified square waveform when it was powered from batteries having nominal voltages of 6 V, 12 V, 18 V and 24 V.
