3 phase supply design

I think you are confusing a few things that need to be addressed. Firstly, I believe that the 90VAC that you are taling about is a "WYE" type voltage which would be normally referenced to line NEUTRAL and the 440VAC voltage
is the voltage line to line accross a "DELTA" which is normally the voltage in a 254/440 WYE/DELTA and low line is really 90/155. This translatesto a 3:1 margin which can be done with a discontinous mode flyback. If you were to three phase rectify this you would get a capacitor voltage in excess of 700 volts from this input at high line as you can not count on having the NEUTRAL connection. This is unfortunately higher voltage than the mosfets that PI uses in their devices. You will have to design a converter with a higher voltage mosfet externally. I suggest that you make the 24VDC and buck regulate for the 3.3v for efficiency reasons. Good Luck

Pls. look at our StackFET circuit technique:
http://www.powerint.com/community/papers-circuit-ideas-puzzlers/circuit-ideas/-high-voltage-input-switching-power-supply-usi

Hi ,

Thank you all for your valuable inputs, i have goen through the stack-FET circuit technique, But i am unable to find necessary documents to carry out a design of the same for my specifiactions...

regards,
Ratheesh

At the top of our website is a search box, to look for previous discussions.
I typed in "StackFET" and found these
http://www.powerint.com/en/forum/power-supply-design/pi-design-software-3-phase-design

http://www.powerint.com/en/forum/ask-pi-engineer/help-me-wide-range-power-supply

--quoting--

"Hello, Most of our parts feature a 700V MOSFET which is ideal for applications that require 85VAC to 265VAC Input. For voltages much higher than that (such as your application which is 400V input), we recommend use of a StackFET which is an arrangement consisting of one our our integrated controllers and a high voltage MOSFET. You can use this technique freely when you use our parts as we have a patent on this technique. The link below provides details of the StackFET

http://www.powerint.com/sites/default/files/PDFFiles/ipStackFET.pdf

We have two design examples that you may be able to use as reference. I am providing the linke to these below.

http://www.powerint.com/sites/default/files/PDFFiles/der58.pdf

http://www.powerint.com/sites/default/files/PDFFiles/di124.pdf

I also suggest that you download our PI-Expert tool which can be downloaded freely from our web site. This tool will enable you to design a transformer suitable for your application. Please use the link below.

http://www.powerint.com/en/design-support/pi-expert-design-software

Hi,

Thank you once again for you valuable inputs....

Regards,
Ratheesh

I do not believe your patent is valid. There is prior art that exists that shows the same technique and even calls out the use of a zener diode across the gate and source of the stecked MOSFET. The prior art is a paper written in 1992 by R.J. Baker and B.P. Johnson titled "Stacking power MOSFETS for use in high speed instrumentation". A pdf of this is readily available on the internet and also attached. The actual circuit design implementation is for a pulse generator, which is very similar to what a power supply pwm circuit does. In describing the stacking of power mosfets a tfigure is shown where three MOSFETs are stacked. If we just concentrate on the two lower MOSFETs in the figure 1 shown in the document and redraw the circuit, we come up with the exact same stacked MOSFET arrangement shown on your patent 5,602,724. I guess the examiners missed this paper or were not aware of it at the time. It is interesting to also not that the arrangement shown on your DI-124 Design Idea application note shows a different arrangement using zener diodes instead of a capacitor resistor combination for driving the gate of the the stacked MOSFET. Interesting in that the claims of the previously mentioned patent are so narrowly written that it would exclude the use of this configuration. This would make this application note public information and would allow use of this design by anyone without regard to the use of your components as you deem necessary in order to use this stacked MOSFET technique.

Dave Moore