Very high gain transformerless boost converter - is it possible

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Is it possible to build a 130-150 Watt, 12V input (for example, car cigarette lighter) to 350V output transformerless boost converter. The efficiency should be at least 85%. Assume a resistor load only.  

If it is not possible, Would there be any other possible tranformerless solutions?

Re: Very high gain transformerless boost converter - is it possible
Possible, yes.  It's possible to shoot onesself to the planet Mars.  That  
doesn't mean it's a good idea, or economically sound. :-)

The best is a tapped inductor, and second best is ordinary flyback (isolated  
at the transformer level, but you don't need to isolate it, it can be tied  
common ground).

Tim

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Electrical Engineering Consultation and Design
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Re: Very high gain transformerless boost converter - is it possible
On 09/02/2018 07:17 AM, Tim Williams wrote:

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It's also probably possible to parallel up the outputs of some boost  
converters you can buy off the shelf, e.g. I have a bunch of these  
modules which claim to be capable of 40 watts (not had a chance to test  
actual full-load capability but the ones I received seem well-built so  
real-world performance may be fairly close to what is claimed)

<https://www.ebay.com/itm/DC-DC-10-32V-to-45-390V-High-Voltage-Boost-Converter-Step-up-Booster-Module-NiHK/223000589035?hash=item33ebdef2eb:g:rZUAAOSwPWRZXF4g

Two of them seem to share load OK with no further effort but to get the  
output power levels as he wants you'd need like four or five, and my  
intuition is they'll wreck each other trying to naively load-share  
without some kind of closed-loop to make sure they share the load  
current equally.

Which you could probably do with current sensing on the input side to  
equalize the power for each, there are a number of schemes online  
but...at that point your "solution" is already rube goldberg and total  
amount of magnetics much larger and heavier and efficiency will deffo  
not be anywhere near 85% so you start to wonder once again what the  
point of these "make a tasty sandwich without bread" exercises are.

Re: Very high gain transformerless boost converter - is it possible
Nomadic Electron typed
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I would not use the word 'gain' here, you meant efficiency I guess.

It's simple (tm)  
350 / 12 = 29.166667
So we need 2 x 29 makes 58  12V batteries, oh why not use 11.1 V lipos
then we need
 350 / 11.1  = 31.531532
say 2 x 31 makes 62 3 cell lipos.

Use a bunch of antique relays, and
put half the lipos parallel to your 12V battery, with some charging control in series with each lipo.
The other 31 lipos  switched in series to the 350V output

Once in a while when output lipos go low, switch the first 32 to the output (in series)
and the second 31 to the battery (in parallel) for charging.

Have a small electrolytic >350 V cap on the output to cover the relay switch-over time.
make sure you use break before make relays,

This also should work with capacitors and MOSFET switches in place of LIPOs.
It is a well known method but forgot what it is called, switched capacitor converter perhaps?
In the case of caps and MOSFETS you need to switch a bit more often.

All depends on what you have in the junk box...
Note the isolation requirement for the MOSFET drivers.

;-)





Re: Very high gain transformerless boost converter - is it possible
On 02/09/2018 11:53, Nomadic Electron wrote:
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A switched mode boost converter would probably work and doesn't need a  
transformer but does need an inductor:

https://en.wikipedia.org/wiki/Boost_converter

Why do you want to avoid transformers?  If you are concerned about the  
size and weight, a high frequency flyback regulator would be a good  
option.  It does require a transformer but it could be fairly small  
compared to the half brick sized things designed to work at 60Hz.

If you want to avoid magnetics altogether then it's going to be more  
difficult.  A Cockroft-Walton voltage multiplier may be an option but I  
don't know what the efficiently would be:

https://en.wikipedia.org/wiki/Cockcroft%E2%80%93Walton_generator

Obviously you would need to generate an AC voltage to drive it but that  
can easily be done.

What are you actually trying to do?

Re: Very high gain transformerless boost converter - is it possible
On Sunday, 2 September 2018 11:54:04 UTC+1, Nomadic Electron  wrote:
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It's possible yes, but the choke would run at a low duty cycle. So to get 85% you'd need a big choke to get low copper loss at short high current spikes.


NT

Re: Very high gain transformerless boost converter - is it possible
Nomadic Electron wrote:

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Switched capacitor converters do exist, but probably not at this power  
level. There are also some experiments with piezoelectric transformers,
but it's still a niche:

http://www.ti.com/lit/an/slyt125/slyt125.pdf

But what's the reason not to use perhaps the most robust electronic  
component in the Universe? Coilophobia?

    Best regards, Piotr

Re: Very high gain transformerless boost converter - is it possible
Nomadic Electron wrote...
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 As others have said, the low duty cycle of an inductor-only
 boost converter, under 4%, spells big trouble for obtaining
 high efficiency.  However, there's an easy trick that can  
 get around the 28x step-up problem: reducing it to two sets
 of sqrt 28 = 6x step-up.  A two-stage boost converter, but
 with one controller, driving two MOSFETs, inductors, diodes
 and capacitors.  Use separate resistors for each gate.  

 The first MOSFET & inductor creates an intermeduate voltage.
 It runs at higher currents, but at lower voltages.


--  
 Thanks,
    - Win

Re: Very high gain transformerless boost converter - is it possible
wrote:

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That's cool. Thanks.

Combine that with my center-tapped inductor trick maybe to get another
4x.




--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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Re: Very high gain transformerless boost converter - is it possible
On 9/2/2018 5:53 AM, Nomadic Electron wrote:
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Get a dynamotor or HV photo flash battery

Re: Very high gain transformerless boost converter - is it possible

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150 Watts?  Not likely.  Not with a flash voltage buildup storage device.

Re: Very high gain transformerless boost converter - is it possible
Oh BTW, this is relevant:
https://www.seventransistorlabs.com/Images/InverterProto1.jpg
just a toy I made.  Toy in that it does what a $30 automotive inverter box  
does.  The left board is a 12V 300mA (isolated) and 170V 1A supply; middle  
is controller, and right is inverter.

I wouldn't suggest doing anything other than a push-pull forward converter.  
A current sourcing inverter (constant current buck supplying PP chopper) is  
better especially at the high voltage output (which will suffer from  
excessive winding capacitance).

Flyback is bad because of the large peak currents required, and single stage  
boost is right out because of the fuckoff enormous inductor and  
semiconductors (and peak currents) required.

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
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Re: Very high gain transformerless boost converter - is it possible
Wow thanks very much for all the replies. I will think about what to do bec
ause there are so many different ideas here. Right now i will probably try  
to do a simulation of the cascaded boost converter idea of winfield hill. M
aybe ill also try simulations using a transformer if it is the best way to  
get the highest efficiency at this power level. Gotta try to understand wha
t some of these ideas are about firstly.

Re: Very high gain transformerless boost converter - is it possible
Nomadic Electron
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And do not forget the 12V DC motor driving a 350V DC generator solution :-)



Re: Very high gain transformerless boost converter - is it possible
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 100 relays switching 100 Li-ion cells from parallel to series.


--  
 Thanks,
    - Win

Re: Very high gain transformerless boost converter - is it possible
wrote:

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Dynamotor. For regulation, control the field of the generator. I think
that's an amplidyne or something. They used them for things like
aiming the guns on battleships.

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Overkill. Two banks of 30 relays each should do it.


--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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Re: Very high gain transformerless boost converter - is it possible
On 2018/09/03 7:55 AM, John Larkin wrote:
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Overkill. Use 4PDT 12VDC relays and I think you are down to around 50  
relays...(2 batteries/relay).

John

Re: Very high gain transformerless boost converter - is it possible
wrote:

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calls the Groucho Marx Generator.


--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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Re: Very high gain transformerless boost converter - is it possible
On 2018/09/04 9:34 AM, John Larkin wrote:
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tion :-)
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k
at Phil

I'd like to see that schematic! I work on both EM and SS equipment and  
so enjoy all forms of electrical abuse...

John :-#)#

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(Please post followups or tech inquiries to the USENET newsgroup)
                      John's Jukes Ltd.
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Re: Very high gain transformerless boost converter - is it possible
wrote:

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My mistake. It was Harpo.

https://www.dropbox.com/s/qycxyrty0hkkzo1/Harpo_Marx.JPG?raw=1

I wonder if there is a variant that doesn't apply so much voltage to
the relay contacts.

How about a rotating cam that drives a lot of switch contacts? Or a
rotating insulated shaft that drives a lot of generators (stepper
motors would work) wired in series.

I'd like to get a bunch of doorknob capacitors, charge them each to
30KV, and then stack or drop them inside a plexiglass tube.


--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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