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Very high gain transformerless boost converter - is it possible

Started by Nomadic Electron September 2, 2018
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
Website: https://www.seventransistorlabs.com/

"Nomadic Electron" <themerchantbay@gmail.com> wrote in message 
news:8eeae69c-e937-4471-9340-130584cdbd61@googlegroups.com...
> 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?
Wow thanks very much for all the replies. I will think about what to do because 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. Maybe 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 what some of these ideas are about firstly.
Nomadic Electron
>Wow thanks very much for all the replies. I will think about what to do because >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. Maybe >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 what >some of these ideas are about firstly.
And do not forget the 12V DC motor driving a 350V DC generator solution :-)
<698839253X6D445TD@nospam.org> wrote...
> > And do not forget the 12V DC motor driving a 350V DC generator solution :-)
100 relays switching 100 Li-ion cells from parallel to series. -- Thanks, - Win
On 3 Sep 2018 05:15:10 -0700, Winfield Hill <hill@rowland.harvard.edu>
wrote:

><698839253X6D445TD@nospam.org> wrote... >> >> And do not forget the 12V DC motor driving a 350V DC generator solution :-)
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.
> > 100 relays switching 100 Li-ion cells from parallel to series.
Overkill. Two banks of 30 relays each should do it. -- John Larkin Highland Technology, Inc trk jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
The best bet would be Dickson triplers stacked. 

The first one takes it to 36, the next one takes it to about 100, the next one takes it to just about 300. More like 290 I would say depending on the parameters you give the convertors. Can you get by on 290 ? If not then stack another one on top but fed from the original 12 or maybe just a doubler off the 36. Caps will not be cheap because they need low ESR and high voltage rating. 

I would not attempt to multiply it all at once but am at a loss to explain exactly why. It just seems the current in the choppers would be too high for good efficiency. Though more junctions means more drop, they are not as significant at higher voltages. 

For each stage of the convertor, you are talking 4 good power transistors, 4 very good capacitors and 6 low loss diodes, Shottkies in the first stage at least. In the first stage you might try to find something like the 1N6095, but those do lose at higher currents. 

One nice thing about using Dicksons is that the main output filter has very little to do because it is fed with 2 polarities of a square wave, and I mean a real square wave not some rounded spiked and "rung" out waveform. 

However the cost is ridiculous compared to just biting the bullet and using a transformer. Also with a transformer it can have isolated output. 

It is so much easier and cheaper just to go to Digikey and find a transformer with a ~1:20 ratio, feed it with a totem pole at its resonant frequency and use a doubler on the output. Use a chopper before the main filter for regulation, or synchronous rectification if you can handle designing it. (more efficient)

At 150 watts that will be a fairly good size transformer and will cost money, but still cheaper than the stacked Dicksons. And much less designing, because with the Dicksons each stage has to be different. Different outputs, different diodes and different caps, you must choose them all. With this many components you don't want too much overkill. With a transformer you design ONE circuit and call it a a day. 

Your call. I like to avoid transformers because they can become unavailable. But sometimes you can't always get what you want. 

I just checked Digikey and no suitable transformer is readily available. Wind your own. At the right frequency you only need a few turns in the primary. So 4 turns there and you want 80 turns on the secondary. For a one off it may be alot of work but handleable. For production forget it, the Chinese probably have something.
jurb6006@gmail.com wrote...
> > The best bet would be Dickson triplers stacked.=20
Do you have a few good references for the Dickson voltage multipliers? I only found two recent locked Academic papers (used my Harvard access to get them). No mention of why called Dickson, no paper by him, etc. Looks like Cockcroft-Walton. -- Thanks, - Win
tirsdag den 4. september 2018 kl. 00.23.05 UTC+2 skrev Winfield Hill:
> jurb6006@gmail.com wrote... > > > > The best bet would be Dickson triplers stacked.=20 > > Do you have a few good references for the Dickson > voltage multipliers? I only found two recent > locked Academic papers (used my Harvard access to > get them). No mention of why called Dickson, no > paper by him, etc. Looks like Cockcroft-Walton. >
https://en.wikipedia.org/wiki/Voltage_multiplier#Dickson_charge_pump ;)
Wow. I invented the thing (not first though) and can't find the Spice file right now. I guess I'll have to make another one. 

I actually posted a hand drawing of it back when I had hosting. Someone replied with a Spice file. I remember it. 

I'll get to it. 
On Monday, September 3, 2018 at 5:32:13 PM UTC-5, Lasse Langwadt Christensen wrote:
> tirsdag den 4. september 2018 kl. 00.23.05 UTC+2 skrev Winfield Hill: > > jurbgmail.com wrote... > > > > > > The best bet would be Dickson triplers stacked.=20 > > > > Do you have a few good references for the Dickson > > voltage multipliers? I only found two recent > > locked Academic papers (used my Harvard access to > > get them). No mention of why called Dickson, no > > paper by him, etc. Looks like Cockcroft-Walton. > > > > https://en.wikipedia.org/wiki/Voltage_multiplier#Dickson_charge_pump > > ;)
That's not what I designed.