The concept is again inspired from a mosfet based powerful amplifier design.Looking at the main power amp design we can see that basically it's a 250 watt powerful audio amp, modified for an inverter application.
All the stages involved are actually for enabling a frequency response of 20 to 100kHz, though here we won't need such high degree of frequency response, I didn't eliminate any of the stages as it wouldn't do any harm to the circuit.
The first stage consisting of the BC556 transistors is the differential amplifier stage, next comes the well balanced driver stage consisting of the BD140/BD139 transistors and finally it's the output stage which is made up of the powerful mosfets.
The output from the mosfets are connected to a power transformer for the required inverter operations.
This completes the power amp stage, however this stage requires a well dimensioned input, rather a PWM input which would ultimately help to create the proposed digital sine wave inverter circuit design.
The next CIRCUIT DIAGRAM shows a simple oscillator stage which has been suitable optimized for providing adjustable PWM controlled outputs.
The IC 4017 becomes the main part of the circuit and generates square waves which very closely matches the RMS value of a standard AC signal.
However for precise adjustments, the output from the IC 4017 has been provided with discrete voltage adjustment level facility using a a few 1N4148 diodes.
One of the diodes at the output may be selected for reducing the amplitude of the output signal which would ultimately help in adjusting the RMS level of the transformer output.
The clock frequency which must be adjusted to 50Hz or 60Hz as per the requirements is generated by a single gate from the IC 4093.
P1 can be set for producing the above required frequency.
For getting a 48-0-48volts, use 4 nos. 24V/2AH batteries in series, as shown in the last figure.
Power Inverter Circuit