The post explains probably the most easiest 400 watt sine wave inverter circuit, which requires lowest number of components and yet is able to produce optimum results. The circuit was requested by one of the active participants of this blog.
The circuit is not actually a sine wave in true sense, however it's the digital version and is almost as efficient as its sinusoidal counterpart.
How the Circuit Works
From the circuit diagram we are able to witness the many obvious stages of an inverter topology. The gates N1 and N2 form the oscillator stage and is responsible for generating the basic 50 or 60 Hz pulses, here it has been dimensioned for generating around 50 Hz output.
The gates are from the IC 4049 which consists of 6 NOT gates, two have been used in the oscillator stage while the remaining four are configured as buffers and inverters (for flipping the square wave pulses, N4, N5)
Until here, the stages behave as an ordinary square wave inverter, but the introduction of the IC 555 stage transforms the entire configuration into a digitally controlled sine wave inverter circuit.
The IC 555 section has been wired up as an astable MV, the 100K pot is used for optimizing the PWM effect from pin#3 of the IC.
The negative going pulses from the IC 555 are only utilized here for trimming the square wave pulses at the gates of the respective MOSFETs, via the corresponding diodes.
The MOSFETs used may be any type able to handle 50V at 30 amps.
The 24 batteries need to be made out of two 12V 40 AH batteries in series. The supply to the ICs must be provided from any of the batteries, because the ICs will get damaged at 24Volts.
The 100K pot should be adjusted using an RMS meter for making the RMS value at the output as close as possible to an original sine wave signal at the relevant voltage.
The circuit has been exclusively developed and designed by me.
Feedback from Mr. Rudi regarding the waveform issue obtained from the above 400 watt inverter circuit
i need your help sir. i just finished this circuit. but the result is not as what i expected, please refer to my pictures below.
This is the wave measure from the gate side (also from the 555 and 4049 ic): it look just nice. freq and duty cycle almost at desire value.
this is the wave measure from mosfet drain side. everything is mess up. freq and duty cycle are changes.
this is i measure from output of my transformer (for testing purpose i used 2A 12v 0 12v - 220v CT).
how to get the transformer output wave just like a gate one? i have a ups at home. i try to measuring the gate, drain, and transformer output. the waveform is almost the same on that small ups (modified sinewave). how do i achieve that result in my circuit?
please kindly help, thanks sir.
Solving the Waveform Issue
it's probably happening due to transformer inductive spikes, please try the following:
first increase the 555 frequency a bit more so that the "pillars" across each square wave cycles look uniform and well distributed..may be a 4 pillar cycle would look better and more atable than the present waveform pattern.
connect a large capacitor, may be a 6800uF/35V right across the battery terminals.
connect 12V zener diodes across gate/source of each of the mosfets.
and connect a 0.22uF/400V capacitor across the transformer output winding....and check the response again.