Sine wave power inverter

[barkerben]

I think we used a PIC for two rasons. Firstly, we wanted the option of going to full sine wave. Secondly, we could eliminate regulation by dynamically changing the deadtime in the quasis sine wave. The 10% (I think it was 10% - lng time ago now) was without any feedback, when running at full load (250W). The PIC was also useful at startup.

Ben

[psdayama]

Hi barkerben !
thanks. It was just curiosity as just few months ago Electronics For You (EFY)
India magazine has published simple inverter with just few ICs and Mosfets.
Of course there are some commercially available inverter cards (Digital Inverter)
with PICs costing no more than Rs.500/- with Quasi sinewave output and frills
of DSP. These are good for PCs and lighting but give lots of problem with fans & motors. They also give regulation of better than 1% in inverter mode and +/-10% in mains mode.
psdayama

[barkerben]

Yep - our circuit may not have been all that good after all, but it was good fun to make! We were building from scratch as much as possible - winding our own transformers, etc. There were a few of us doing it at once. One group had a novel way of stopping their mosfets from frying - a constant stream of freeze spray! Not exactly very practical, but certainly impressive :-)

One group tried a resonant inverter, but got bogged down with the problem of sensing the load parameters to match the resonance...

[barkerben]

Oh yes, that was it... I remember now.

We had 24v in, chopped using a full bridge to 20Khz AC, fed into a transformer, then rectified to high voltage DC using a diode ring. The ide of high frewuency was to reduce transofrmer size and losses. The high voltage DC was then chopped usign a second H bridge to a quasi sine output.

The trigger signals for both bridges were generated by the PIC. We wanted to replace the quasi sine bridge trigge with full sine, but never got around to it :-(

[psdayama]

Oh yes, that was it... I remember now.

We had 24v in, chopped using a full bridge to 20Khz AC, fed into a transformer, then rectified to high voltage DC using a diode ring. The ide of high frewuency was to reduce transofrmer size and losses. The high voltage DC was then chopped usign a second H bridge to a quasi sine output.

The trigger signals for both bridges were generated by the PIC. We wanted to replace the quasi sine bridge trigge with full sine, but never got around to it :-(

That was good!!! U should have made the output of hi freq. transformer centre tapped and used bridge to get dual supply i.e. +/- side. This requires
only half bridge ckt and only 2nos of Hi voltage Mosfets and get good sine wave
from it.(U require small inductor/capacitor filter for non inductive loads.) Again U can prevent the Mosfets from frying with including some current limiter in HT side rectified high voltage rather than spraying freezant.