Instructables

DC-DC HV Boost Converter

Step 1: Operation and Electronics Intro

Boost Converter Basic Not Conducting.bmp
Basic Schematic Symbols.jpg
Capacitor Ratings.bmp
Resistor Color Code Chart.bmp
Mosfet and Diode Connections.JPG
How Does A Boost Converter Work?
Basic Principal:
A boost converter works in two stages, ON and OFF. In the ON stage the Semi-conductive Switch is conducting and current builds up in the inductor producing an
electromagnetic field, this field stores energy. In the OFF stage the Semi-conductive Switch does not conduct and the electromagnetic field collapses. When the field collapses the energy stored
in it can not escape through the Semi-conductive Switch so it goes through the diode and into the load/Capacitor at a much higher voltage. This happens several
thousand times a second via the pulses from the NE555 Timer Chip and the result is being able to charge a high voltage capacitor from a low voltage source.
Below is some aid for those of you who do not know electronics well.

R-Resistor
VR-Variable Resistor (also called a Potentiometer)
B-Battery
V-Voltage Source
C-Capacitor
D-Diode
L-Inductor
U / IC-Integrated Circuit
Q-Transistor / IGBT
M-MOSFET
GND- Ground (Negative terminal of Battery for Portable Applications)

Some Diagrams and Charts are shown below to help you further.
Aiyoku192 months ago

Great project! Thanks for the useful schematics.

jpoopdog5 months ago
hi, i just built this and im having some issues, though im not sure if it is, but i feel it may have something to do with me using an L7812cv instead of lm7812act.

Anyway, whats happening is that the fet seems to wind up locked between on and off, and what happens here is that the voltage climbs only very slowly, and the mosfet starts to generate allot of heat. i think the 555 at this stage just outputs a constant high. any idea on how to solve? at voltages like 150v the 555 has no issue bouncing the voltage up with a few buzzes every time it drops to below, however, once im getting over 200v it seems to get stuck and its really annoying, i might just try modding the circuit to disconnect the power supply to the 555 instead, so that i cant have instances where the lm393's light is on, as well as the 555. perhaps i should setup the 555 to output constantly
Chris944 years ago
Would it be possible to put 2 or 3 DC-DC HV Converters in parallel to decrease the time it takes to charge a capacitor bank;as you did in your other Instructable with the camera circuits????
rwilsford07 (author)  Chris944 years ago
What most people do to get more power out of their boost converters is to use two inductors, two output diodes, and two MOSFETs. The output of the 555 timer is fed into a MOSFET driver (like the TPS2813) with an inverting and non-inverting output. The two complementary outputs are fed into the separate Inductor-MOSFET-Diode configurations which doubles the output power capable with a single boost converter. The 555 would have to be setup to provide about a 50% duty cycle which means that you will have to redesign and test different inductors to get the correct output and efficiency. I would not recommend putting two separate boost converters together as they will not be synchronized and therefore disrupt each others frequency and the combine output would be different each second it is operating. Another thing you can do is use the LT3751 chip from Linear Technology, the data sheet guides you through the whole design process and you can get well over a couple hundred watts if you have batteries capable of it putting out that much power. This is the chip I am using for any portable coilguns or railguns I'll be making in the future.
Eoxan rwilsford079 months ago
What if you used a 556 timer chip instead?
I need to convert a 6v 4.5A battery into 12v that can give around 2A or more current.
Any schematic? Voltage doubler circuits on the web gives around 100mA which is not sufficient for motor driving. Thanks...
they are an ace little chip from the specs. i got a couple free samples, and a breakout board to solder to.
complete failure.
chip kept coming off the breakout board, and since the tracks are so fine, they got ruined pretty quick
dont suppose you know of an equivalent in a more reasonable package rather than those damn smt chips?
Eoxan9 months ago
What if you used a 556 timer chip instead?
nuttyboffin12 months ago
Hello, ive built this circuit as close as i could to the circuit but for some reason the coil and mosfet got burning hot within less then a second of being on....
Vortex181 year ago
I cannot seem to get this circuit to work. I have it built on a breadboard for easy swapping out of components, but after building, rebuilding, checking, double checking, and lastly swapping out components for their duplicates, I cannot get this circuit to output anything higher than what I put into it, being 12v. I have all the components listed for the <12V version of the circuit and have built it according to the schematics posted. Adjusting the potentimeter only allows me to switch between illuminating LEDREG and LEDGATE but there is no change in output voltage. Both ICs do get power to their respective Vcc pins with the Ground pins connected to ground and the MOSFET is inserted in the right orientation, as is the Diode. I've been racking my brain trying to figure this out but I am finally at a loss. All I really have now is a fancy looking multi-LED illuminator. Is there anyone that can help me troubleshoot this thing? Much appreciated.
Hey, can i ordered 8 of the coils, can i put them in paralell or simler to obtain greater output?
jpoopdog1 year ago
I got an inductor from coilcraft, i didnt like the idea of lying about being part of a company using the inductor genuinly as a sample. however, postage costs are very high for inductors and not worthwhile to buy from coilcraft unless in large numbers, are there alternative sources for similar inductors that will work here pretty much the same?

Im talking of course about identical spec inductors that dont cost $50 or more than the total cost at coilcraft.

What really bugs me is that standard postage in checkout to australia is $40, yet the sample they gave me by express post for free, says that it only cost $15.
coilcraft will do free samples of any of their products.
just been to the website, anfd ordered 5 of the PCV-2-394-05L coils for this project for a total cost of nothing!
will update you guys if and when i receive anything!
i love free stuff!
yup, coilcraft sent me a whole bunch of free stuff! yay!
had a few problems with slow charging to start, but that was due to the duty cycle on my 555 being all to hell.
and 13003 trans work well as replacements for the mosfet.
best of all, theres 2 of em in cfl lamps worth 10p from tescos!
does anyone else get this sense of overwhelming pride from being such a cheapskate?
hehe
More power to you, whiskeymonster! Tesco sell cfl's for 10 pence? Is that right??? Bugs me to hell that you can buy products containing parts that are cheaper than buying the parts, though...
ok i lied.
the 13003 dont work.
i have a whole bunch of resued components, and i wasnt using the ones i thought.
still though, i get 730v peak, and can charge 500uf to 320v in about 10s. using a 12v 2a wall wart.
havent added the comparator cutoff yet, will do once i get some more solder tomorro.
AND i havent killed myself at all so far!#
yay!
yah!! me two
luddite202 years ago
Hey guys, so a quick question. Is the purpose of the capacitor in the circuit to provide voltage to the load even when the switch is closed?
obrien0082 years ago
Does anyone have any idea on how to make this output over 600V??
I cant find a MOFSET rated for enough current at over 600V, Can I use a 1200V IGBT instead of the 600V MOFSET??????

Can I use the same inductor???
Just a tip: save some questionmarks for the rest of us ;)

i dont know what you will use this for, but maybe a Cockroft-Walton voltage multiplier would do the job for you.

you build a transformer like this one, and add a Cockroft-Walton voltage multiplier at the output.

Depending on what output you will need, you add steps on the multiplier :)
ptorelli2 years ago
Excellent compact design!

But just a head's up for folks running <12V: this circuit can't drive 5V to 500V because the 555 duty cycle is not high enough even with RST=0. 5 to 500V is a 99% duty cycle in continuous mode. You need a completely different topology to realize those kinds of gains, but finding a NFET with a slew rate that can handle duty cycles that high is unlikely. Depending on the tolerance of your components, you'll likely only realize 100~140V from a 5V DC supply. You'll need a step up transformer (rather than a coil) to achieve higher voltages than that.
How feasible is it to boost a 0.1W I/P to about 3 or 4W? The input is an AC supply at UHF range which would be rectified with schottkey diodes (as hey support high freq). i need to boost this rectified DC to a range sufficient to charge an average cellphone (maybe the NOKIA 1100 model
jpoopdog2 years ago
I think it would be more proficient to build your own inductor for this, especially for those insanely high shipping prices from coilcraft and mouser. asking for a total of $62 between them to send me the parts
obrien0082 years ago
Which resistor values would I need to adjust to get 900v output just VR1? Would I need to change anything else?
ok obivously my ICs will need to be 1kv rated, but I need a suggestion for an inductor, thanks in advance.
Electorials2 years ago
Does this also work on a coil without a feromagnetic core? (so only air).
yes. it works perfectly for a coil gun, and to be fair, blows those silly little camera boards away!

all it does is generate silly numbers of volts, and uses caps in a futile attempt to smooth the output for this beast! the trick is to stop it completely overrating your caps and causing exciting and stinky releases of magic smoke !

those caps you can use for anything you like once they are charged, powering coil guns, houses, doomsday devices etc.
i calculated that from half a dozen camera caps, and this circuit along with another few bits and peices, i can compress the earth to a mathematically insignificant point.
i decided against it. where would i keep my stuff?

but yes. this will power your coilgun famously, and i have gotten it to charge to 500uf in about ten seconds.
i do recommend putting a comparator on the output so it cuts off once it gets to your predefined level.
burst caps stink!
it would be great for coilguns indeed!
Electorials2 years ago
This is really interesting! nice instructable!
is there a way to let's say switch off the charging circuit when the capacitor bank had reached 200V without any human intervention? thanks!
tazerboy2 years ago
how much ma does this unit supply
AgNO32 years ago
Hi,
I've built the circuit and with FCA47N60 and PCV-2-394-05L it works very well, but when I use HGTG11N120CND and PCV-2-564-06L (to reach 1000v) it doesn't work.
Does anyone know why?
dilbert2273 years ago
hmmmmmm dose did anyone happen to find a substitute for the RURG30120 and the MC7812ECDTX, they happen to be on back order for like a year.Any help would be greatly appreciated.
sneezy323 years ago
I have bought the MLCC caps needed for this project...they are uber small. Did you use those types in your model, and will the small one i have work?
hey im pretty sure as long as they are the same value it will be fine :)
eggman3 years ago
trying to troubleshoot here. whats the voltage on pin 1 of the lm393 when the 555 is supposed to be on. currently my 555 never turns on, and i think its the lm393's fault.
wahabfun3 years ago
can u suggest me the software for pc from which i can make this circuit and anylayse it thanks
Well, I've used TINA for a while, now I'm using Multisim instead. Although you should really take any simulator with a pinch of salt: if might work for this circuit or might not (I haven't tested yet). The thing is, I've tried to simulate a few other designs which used a couple of transistors instead of the 555 timer with no luck. They were using a property of the transistors which the simulation doesn't account for though (negative resistance), which the 555 timer doesn't, so it might work for this circuit. Try it and you'll see :P
eggman3 years ago
yessssssssssss, i finally got it to work! i had a bad 555 timer and it blew out my MOSFET. now that it works, it charges my 8400uF caps to 400V super fast.
eggman eggman3 years ago
however, while it does take about 45 seconds to charge, its *very* loud, and my mosfet gets so hot, i can only do about 1 charge per 2 or 3 minutes in fear of overheating, and thats with a heatsink.
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