On Tue, Oct 31, 2006 at 10:07:52AM -0800, Yigit Turgut wrote:
> > The above three items are very inconsistent. So please provide
> > more information:
> >
> > 1) Why do you need to convert 12 VDC to 220 VAC?
> >
> > 2) What maximum current at 220 VAC do you need? What
> > current capacity at 12 VDC can you provide?
> >
> > 3) Is the equipment sensistive to the type of output
> > wave generated? i.e. do you need true sine, modified sine,
> > or will a square wave be sufficient.
> >
> > 4) And of course the most pointed question: Why not buy a
> > power inverter? It's a device that solves the problem. So
> > a reason as to why it's not an option would be helpful.
> 
> Well,money is not an issue,I just want to build my own inverter.
> 
> I will be running a pc at my car.So I do need to convert 12VDC to
> 220VAC.I designed the system such as ;

See why you need to specify the application? Actually no you don't. Every
voltage on a PC is DC and low voltage. So there's absolutely no reason to run
12VDC up to 220 VAC simply to downconvert it back to low DC voltages.

Bob Blick on the list has a design for a multi voltage DC to DC converter
specifically for power a car PC from 12VDC for example.

> When car is running between 7000-9000 rpm,energy will be suppilied
> directly from the alternator,if not so,energy will be supplied from
> the car battery (through inverter)

I've built one of these before. There are more issues:

1) When starting there is often a significant voltage drop.

2) Car power is a frightful place. You're going to need good filtering.

The way that I finally resolved the issue was to insert a 12VDC gel cell
before the DC/DC converter (which I purchased from Marlon P. Jones and
associates surplus store http://www.mpja.com). Then when the car started
the gel cell would carry 12VDC long enough for the PC not to shut down.

> 
> Modified sine wave seems to be the easy way.
> 
> What about Pure Sine Wave ?

Neither. You need a DC to DC converter. Also 12V powered ATX power supplies
for mini ITX motherboards already exists. Another option is powering a
laptop via a boosted DC voltage.

I spent a lot of time fighting this particular fight. It's really not worth
fighting. The fight is a useful car PC, not providing power for it.

BAJ
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