need some help designing a Sinewave inverter

I would like to build a pure sinewave inverter and need some help in
designing & component selection.

What ?
A 100-200 Watts, 230 V pure sinewave inverter
Input: preferably one 12V SMF battery. two if absolutely needed.
Output: 230V RMS sinewave capable of 100 ~ 200 watts
Load: 19" LCD TV for now.

You're going about it wrong.

On Tue, 20 Jul 2010, tmpstr wrote:

I would like to build a pure sinewave inverter and need some help in
designing & component selection.

What ?
A 100-200 Watts, 230 V pure sinewave inverter
Input: preferably one 12V SMF battery. two if absolutely needed.
Output: 230V RMS sinewave capable of 100 ~ 200 watts
Load: 19" LCD TV for now.

You're going about it wrong.

Find an LCD tv set with an external power supply, or modify the existing
set. Then figure out the voltages it needs, and supply those directly.

What you propose is to convert a 12v DC source to high voltage AC, so the
tv set can then convert that AC to a low voltage DC source. Chances are
good that the tv set is using a switching supply.

Figure out how to run the set off 12vdc directly, and feed a battery into
it. You may need some regulators to supply some other voltages, depending
on what's in the tv set. Or, replace the existing switching supply with
a supply that takes 12vdc and supplies the needed voltages.

Why ?
Primarily for learning.Yes, i know building one may cost more than
buying. Yes i also know that
lethal voltages will be present.

I would like to build a pure sinewave inverter and need some help in
designing & component selection.

What ?
A 100-200 Watts, 230 V pure sinewave inverter
Input: preferably one 12V SMF battery. two if absolutely needed.
Output: 230V RMS sinewave capable of 100 ~ 200 watts
Load: 19" LCD TV for now.

Constraints:
Design should be simple as this is my first hi-wattage supply.
Would like to use standard off-the-shelf transformer and other
component.(as i have no experience designing transformers)
Should be very fault tolerant (overload/SC etc) and safe to use as i
am the one who will use it.

Why ?
Primarily for learning.Yes, i know building one may cost more than
buying. Yes i also know that
lethal voltages will be present.

What i can:
i am an electronics hobbyist and design digital ckts regularly, but
have not embarked on a high wattage power supply before. Have the
standard tools like DMM/DSO and use LTSpice, gEDA and such tools. Have
designed and programmed PIC18F micros.

My proposed block diagram:
12/24V --> [ DC-DC boost converter] --> 320 VDC --> [ 100 KHz PWM/H-
bridge ] --> [ Filter ] --> 230V RMS sinewave.

What help i need:
Topology: How to get the 325V peak DC in the first place ? does it
require multiple boost stages ?
Transformer: I guess a transformer would invariably be needed. how to
select one (off the shelf one) ?
Snubber: How do i go about design a snubber ?

Any answers or even pointers to above questions would be much
appreciated..
Thanks

I would like to build a pure sinewave inverter and need some help in
designing & component selection.

What ?
A 100-200 Watts, 230 V pure sinewave inverter
Input: preferably one 12V SMF battery. two if absolutely needed.
Output: 230V RMS sinewave capable of 100 ~ 200 watts
Load: 19" LCD TV for now.

Constraints:
Design should be simple as this is my first hi-wattage supply.

"tmpstr" <mahesh_nkr06_at_yahoo.co.in> wrote in message
news:0c0db393-62ab-4b72-b11f-adf13e0c275b_at_u36g2000prg.googlegroups.com...
I would like to build a pure sinewave inverter and need some help in
designing & component selection.

What ?
A 100-200 Watts, 230 V pure sinewave inverter
Input: preferably one 12V SMF battery. two if absolutely needed.
Output: 230V RMS sinewave capable of 100 ~ 200 watts
Load: 19" LCD TV for now.

Constraints:
Design should be simple as this is my first hi-wattage supply.
Would like to use standard off-the-shelf transformer and other
component.(as i have no experience designing transformers)
Should be very fault tolerant (overload/SC etc) and safe to use as i
am the one who will use it.

Why ?
Primarily for learning.Yes, i know building one may cost more than
buying. Yes i also know that
lethal voltages will be present.

What i can:
i am an electronics hobbyist and design digital ckts regularly, but
have not embarked on a high wattage power supply before. Have the
standard tools like DMM/DSO and use LTSpice, gEDA and such tools. Have
designed and programmed PIC18F micros.

My proposed block diagram:
12/24V --> [ DC-DC boost converter] --> 320 VDC --> [ 100 KHz PWM/H-
bridge ] --> [ Filter ] --> 230V RMS sinewave.

What help i need:
Topology: How to get the 325V peak DC in the first place ? does it
require multiple boost stages ?
Transformer: I guess a transformer would invariably be needed. how to
select one (off the shelf one) ?
Snubber: How do i go about design a snubber ?

Any answers or even pointers to above questions would be much
appreciated..
Thanks

1. Topology - how about inverting the 12V into AC then into a transformer.
Then you can simply run the transformer "backwards".

e.g., if I was going to do it:
12VDC->PWM->Step Up-> Filter->sinewave

It shouldn't be hard to find a 230V:12V transformer and hence you just run
it in reverse(although you might get a higher voltage since it won't be
exact).

This method uses cheaper mosfets because of the low voltage(as it is easier
to drive as there is no HS gate... you'll be able to use both n-ch and
p-ch). Of course th current is larger but shouldn't be a bit problem.

In the US I could just take a basic wall-wart and use that. (The difficult
thing is you'll need a 10A wall-wart which I've not ever seen... but you
could take a few and parralel them)

2. Snubber - For AC these are basic cap + res in series. It acts as a simple
HP filter and shunts HF spikes across the switches. There are other methods.
For DC one can use diodes as any reverse spike will flow through the diode
instead of trying to flow through the switch. Most mosfets have built in
diodes and depending on the currents involved you don't have to do anything
but makes sure you get the direction right.

There are lot's of inverter circuits out there that you might want to take a
look at. If I were really going to do this I would follow what you suggest
and simply use a boost converter. Getting the 325V shouldn't be an issue.
The duty cycle will be about 3% which is a bit low but doable.

To get the inductor/transformer for these circuits you have to worry mainly
about three things. DC resistance, Inductance(many calculators on the net
for it), core saturation. (this is assuming your buying off the shelf)

You can compute the total magnetic flux based on the core type and current.

http://en.wikipedia.org/wiki/Saturation_%28magnetic%29

Should help.

If you use wall-warts or they may saturate and not be as effective but by
paralleling them you'll reduce the current and hence the total flux through
each individual core.

If you use wall-warts or they may saturate and not be as effective but by
paralleling them you'll reduce the current and hence the total flux
through
each individual core.


Paralleling the primaries does not reduce flux density. Reducing
excitation voltage, or increasing frequency, does.

All others things being constant, reducing the load current taken from
a transformer secondary *increases* flux density in the core.

"tmpstr" <mahesh_nkr06_at_yahoo.co.in> wrote in message
news:0c0db393-62ab-4b72-b11f-adf13e0c275b_at_u36g2000prg.googlegroups.com...
I would like to build a pure sinewave inverter and need some help in
designing & component selection.

What ?
A 100-200 Watts, 230 V pure sinewave inverter
Input: preferably one 12V SMF battery. two if absolutely needed.
Output: 230V RMS sinewave capable of 100 ~ 200 watts
Load: 19" LCD TV for now.

Constraints:
Design should be simple as this is my first hi-wattage supply.
Would like to use standard off-the-shelf transformer and other
component.(as i have no experience designing transformers)
Should be very fault tolerant (overload/SC etc) and safe to use as i
am the one who will use it.

Why ?
Primarily for learning.Yes, i know building one may cost more than
buying. Yes i also know that
lethal voltages will be present.

What i can:
i am an electronics hobbyist and design digital ckts regularly, but
have not embarked on a high wattage power supply before. Have the
standard tools like DMM/DSO and use LTSpice, gEDA and such tools. Have
designed and programmed PIC18F micros.

My proposed block diagram:
12/24V --> [ DC-DC boost converter] --> 320 VDC --> [ 100 KHz PWM/H-
bridge ] --> [ Filter ] --> 230V RMS sinewave.

What help i need:
Topology: How to get the 325V peak DC in the first place ? does it
require multiple boost stages ?
Transformer: I guess a transformer would invariably be needed. how to
select one (off the shelf one) ?
Snubber: How do i go about design a snubber ?

Any answers or even pointers to above questions would be much
appreciated..
Thanks

1. Topology - how about inverting the 12V into AC then into a
transformer. Then you can simply run the transformer "backwards".

e.g., if I was going to do it:
12VDC->PWM->Step Up-> Filter->sinewave

It shouldn't be hard to find a 230V:12V transformer and hence you just
run it in reverse(although you might get a higher voltage since it won't
be exact).

This method uses cheaper mosfets because of the low voltage(as it is
easier to drive as there is no HS gate... you'll be able to use both
n-ch and p-ch). Of course th current is larger but shouldn't be a bit
problem.

In the US I could just take a basic wall-wart and use that. (The
difficult thing is you'll need a 10A wall-wart which I've not ever
seen... but you could take a few and parralel them)

I would like to build a pure sinewave inverter and need some help in
designing& component selection.

What ?
A 100-200 Watts, 230 V pure sinewave inverter
Input: preferably one 12V SMF battery. two if absolutely needed.
Output: 230V RMS sinewave capable of 100 ~ 200 watts
Load: 19" LCD TV for now.

Constraints:
Design should be simple as this is my first hi-wattage supply.
Would like to use standard off-the-shelf transformer and other
component.(as i have no experience designing transformers)
Should be very fault tolerant (overload/SC etc) and safe to use as i
am the one who will use it.

Why ?
Primarily for learning.Yes, i know building one may cost more than
buying. Yes i also know that
lethal voltages will be present.

What i can:
i am an electronics hobbyist and design digital ckts regularly, but
have not embarked on a high wattage power supply before. Have the
standard tools like DMM/DSO and use LTSpice, gEDA and such tools. Have
designed and programmed PIC18F micros.

My proposed block diagram:
12/24V --> [ DC-DC boost converter] --> 320 VDC --> [ 100 KHz PWM/H-
bridge ] --> [ Filter ] --> 230V RMS sinewave.

What help i need:
Topology: How to get the 325V peak DC in the first place ? does it
require multiple boost stages ?

Transformer: I guess a transformer would invariably be needed. how to
select one (off the shelf one) ?

Snubber: How do i go about design a snubber ?

Alternately, use a transformer with a turns ratio greater than 320:12,
and control the duty cycle down.

If it makes it a wee bit easier to get a right transformer, i am ok to
add one more battery and make the input 24V.

For this you may find it easiest to wind your own. Cores are available
for just this sort of thing.

I believe winding a transformer is some kind of black magic involving
lots of trial-n-error not to mention getting the correct core. Are
there any caveats here ?
If it comes to that, i am ok with winding my own transformer as well;
only that i may tie myself in coils& "learning" would be much more
than i had bargained for

Get isolated 320VDC, drive your AC with an H-bridge, and you shouldn't
need a transformer on the HV side -- just output filtering.

This is what my original plan is. Get the 320VDC, then using PWM+H
bridge on it get the 230V and then filter it.
and the most important question i have is how to get the 320VDC out of
12VDC(or even 24VDC)
let me have a look at the ST design i hit upon...

Thanks

If you use wall-warts or they may saturate and not be as effective but by
paralleling them you'll reduce the current and hence the total flux
through
each individual core.


Paralleling the primaries does not reduce flux density. Reducing
excitation voltage, or increasing frequency, does.

All others things being constant, reducing the load current taken from
a transformer secondary *increases* flux density in the core.



Haha, you really have no knowledge of electronics do you? When are you going
to learn the difference between current and voltage?

e.g., if I was going to do it:
12VDC->PWM->Step Up-> Filter->sinewave

It shouldn't be hard to find a 230V:12V transformer and hence you just run
it in reverse(although you might get a higher voltage since it won't be
exact).

Alternately, use a transformer with a turns ratio greater than 320:12,
and control the duty cycle down.

For this you may find it easiest to wind your own.  Cores are available
for just this sort of thing.

Get isolated 320VDC, drive your AC with an H-bridge, and you shouldn't
need a transformer on the HV side -- just output filtering.

On Wed, 21 Jul 2010 12:19:28 -0500, "George Jefferson"



phreon...@gmail.com> wrote:
If you use wall-warts or they may saturate and not be as effective but by
paralleling them you'll reduce the current and hence the total flux
through
each individual core.

Paralleling the primaries does not reduce flux density. Reducing
excitation voltage, or increasing frequency, does.

All others things being constant, reducing the load current taken from
a transformer secondary *increases* flux density in the core.

Haha, you really have no knowledge of electronics do you? When are you going
to learn the difference between current and voltage?

I took two semisters of Electrical Machinery in college, which
included a lot of transformer theory and practice. I got A's [1]. I've
designed transformers, too, from 60 Hz to over a GHz. How about you?

How's this for a pick-and-place machine?

ftp://jjlarkin.lmi.net/PP5.JPG

That transformer weighs more than one of my employees.

John

[1] My average on tests was about 60. But the class average was around
15, and the prof graded on the curve. I did learn a lot about
transformers.

e.g., if I was going to do it:
12VDC->PWM->Step Up-> Filter->sinewave

It shouldn't be hard to find a 230V:12V transformer and hence you just run
it in reverse(although you might get a higher voltage since it won't be
exact).

Did you mean PWM -> Filter -> Step Up ?
this would allow me to use a 50Hz transformer (quite bulky for 50 Hz,
100 Watts. may need a trolley ).