design of transformer- less ups (modified sine wave)

Hi,
I want to design a small modified sine wave transformerless ups (400 Watt) .Can anyone help me with the block diagram and schematic?? Will be extremely thankful .

Here you go:

Hi,
If you mean with no transformers, not even ferrite ones, then you have to first step up the battery voltage to high voltage (260-300v) using boost converter and then use H-bridge converter.
I think what you mean, is, without heavy iron core transformer. In that case, use SMPS with a ferrite transformer. First step up battery voltage using a push-pull converter driven by an SG3525 and then use H-bridge converter driven by SG3525 and IR2110. For the charger side of things, use an iron core transformer or a flyback converter using TOP/VIper or UC384x and MOSFET.

I recommend you use a transformer. Using just inductor means, you'll need a very low duty cycle with high peak currents and you'll also require a high voltage MOSFET/IGBT that is likely to have higher RDS(on) resistance, which will result in higher losses.

Hope this helps.
Tahmid.

Hi,
You may find this application note from Microchip helpful -
https://ww1.microchip.com/downloads/en/AppNotes/01279A.pdf

thnx all .yeah by transformerless i mean that it has to use a high frequency transformer.

one more thing . since ill be desigining an offline ups for PC then the system will turn off if the switching is not fast between mains and inverter.what shud be the switching time between mains and inverter so that the system does not turn off .