Boost 12Vdc to 100Vdc ?

[electrookie]

Greets all...

I am looking for a circuit to boost 12Vdc(car batt.) to 100Vdc. I find various circuits that give me ideas but not yet found the "right" idea. It seem's that these "charge pumps" are the way to go for this. As I understand, this is due to the lack of inductors. I do find plenty of circuits to boost current and this seems relatively easy to do so I am thinking of using some kind of charge pump design, whatever its current is, then running that thru the current amp. I only want 20 amps or so, more likely just need a few amps, but want as much available as I can get.

I want to avoid converting the 12Vdc to an AC voltage only to have to convert back to the desired DC. That seems to me, a wasted step, wasted design, etc.

I will keep searching, but I throw this out to you all to see if any one has an idea of where I should go with this.

Thank you all for your help on my other projects to date. This seems to be the Forum to go to as I get issue resolving help from you in here. So thanks again...

 

[Sceadwian]

Only want 20 amps of 100VDC? That's going to be a MINIMUM of a 166amp draw from the 12V side and that's assuming 100% conversion, you're not gonna get much better than 70-80% so you're looking at close to 200amps being drawn from the battery... You're going to have to convert it to AC at some point. If you use a commercial inverter to get 200VAC your task is much simpler, you just pass it through a 2-1 transformer and rectify it. Bang your done.
What is this for? That's some pretty serious power. Also, why do you say 1 amp would be okay but you want 20?

 

[electrookie]

Thanks for the info...

Thanks for your reply. When I posted this, I was not to sure about the ability to go DC to DC with that much power. I have been searching all day for info and I can now understand what you are saying. KISS is the best way to go and I was looking for the long way around. Learning by searching the web is hit and miss, questions are answered while more arise. Back to learning then.....

 

[Sceadwian]

Good luck, anyone here will help you learn =) Just be careful!

 

[smanches]

FYI, for that type of scenario, you would use a boost. or a flyback converter. Charge pumps for for small currents that need little regulation, and would not be able to handle the power you're looking at.

The boost can handle the current better than the flyback, but I think the flyback would be a bit more efficient. The biggest problem would be finding a flyback transformer that could handle the 20+ amps.

 

[electrookie]

More DC boost question's for you all...

Hi guys. I have been searching, studying this circuit theory still. I just can't get the idea out of my mind that there is a way to do this DC to DC. Lets drop the 20 amps part all together. Lets say 5 amps max. Even 1 amp, if the case may be, but you will see why I think this is possible. As for the amps, in the end, I do not know what would work and what would not, and I am reluctant to discuss why or what my goal is for this circuit because I just do not want to get any flames going. I would prefer to stay on the subject itself, not the application. Besides, if this can be done, the applications will be numerous.

In the attached file, I collected 4 "article's", for lack of a better word, that deal with this idea. The 1st 2 describe how to boost 1.5 to 6, or 6 to 12, etc... DC to DC boosting.

The 3rd article is a circuit for boosting current. The 4th is a Wickpedia article of the DC boost subject and is included mainly because I have never trusted Wickpedia and am curious if their info on this subject is valid. Its more than what is needed for this discussion, but it may be useful to the same.

So my idea is boost a car battery from 12 to 80 or 100 volts with the concept in the 1st 2 articles. Then, boost that resulting voltage with the circuit, or some similar idea, in the 3rd article.

I understand that getting more out than what goes in is not going to happen. I am not looking for magic here. But if I have a 100 amp 12 volt battery, I think I should be able to get some serious current for the boosted DC in the end, without going thru AC in the process.

I am interested in hearing ideas of how to make this work more than reasons why it will not. Please keep the negative's out of this and lets see if we can not come up with some ideas to make this work. If you are a fan of SG1, then its similar to the episode in which the Asgard get help from the SG1 (humans), to fight the Replicators, because human's think in archaic technology the Asgard's can not reach down too. In this case, you all are the Asgard, I am the "dumb down human". I don't know why it is not supposed to work, so in my mind, it can work. Besides, many an invention came from basements or garages of people who did not know their idea was not supposed to work. They made "it" work and let the scientist figure out how "it" works after the fact. And I have seen such a case personally in my life where there had to be new math created to explain how that "it" worked.

It is nothing short of a challenge to you all. There are a lot of educated people in here and here comes along a rookie such as I who believes you all can make this "it" actually work. Or am I just smoking something other than cigars???

Looking forward to your input...

 

[Sceadwian]

If you've noticed electrookie, ALL DC-DC converters first have to convert the energy to DC pulses. IE it turns it into AC. All you really need is a comercial inverter rated at the total power you want and a transformer/rectifier. The only hard part is the transformer.

 

[ke5frf]

I'm sorry. I hate to seem mean, but if your screen handle indicates you are new to electronics, I don't understand where you are going with this. I think it is great to experiment and come up with ideas, no matter how ludicrous they may seem, and pursue them. But you also have to realize that a certain amount of physics is involved here. Brilliant men (and women) have been looking for solutions to problems like this since electricity was first experimented with. Yes, shadetree scientists and inventors have brought new discoveries throughout history. But generally speaking these people have a firm grasp of the science to base their experiments on.

In other words, and this is just another man's opinion, but I think you have to understand why you CAN'T do something before you go off figuring out how you CAN....i.e. you need to completely understand the known science and accepted assumptions in order to disprove them and discover something new. Do you understand WHY you have to use AC waveforms to step the voltage up through a transformer or coil? Do you understand that this problem dates back to the early experiments of Nikola Tesla, Thomas Edison and even before?

I am interested in hearing ideas of how to make this work more than reasons why it will not. Please keep the negative's out of this and lets see if we can not come up with some ideas to make this work. If you are a fan of SG1, then its similar to the episode in which the Asgard get help from the SG1 (humans), to fight the Replicators, because human's think in archaic technology the Asgard's can not reach down too. In this case, you all are the Asgard, I am the "dumb down human".

This isn't Star Trek or science fiction, it is science. Good luck finding what you are looking for. One suggestion. Before you throw out there "Please help me figure out how to make a time travel machine", it helps first to have some reasonable theory, some phenomenon, or some long forgotten principle or concept, from which to start. Just "wanting to" isn't enough.

 

[Blueteeth]

Ke5frf,

I see your point, and its well said...but...one doesn't have to completely understandall principles and mathematics behind an idea to get a working prototype. Of course, in this particular project dealing with lethal voltages and a high power through-put 'tinkering' becomes a hell of a lot more difficult. If something shorts in a 1W DC-DC converter, you may hear a hiss....at 1kW, it'll sound like a shotgun.

As for something to think about....the large forward transformer inside a typical PC ATX power supply could handle that much current. Its not as simple as 'hooking it backwards' of course, not to mention efficiency troubles (its designed for stepping down...) but an ATX power supply has some useful stuff for medium power DC-DC converters.

 

[blueroomelectronics]

And remember HHO doesn't work.

 

[mneary]

If you want 'serious current' at 100V, you will need 10x 'serious current' at the 12V input. If you accomplish over-unity in a simple voltage boost circuit, you're in line for a Nobel prize.

 

[blueroomelectronics]

I can smell goofy HHO projects from great distances. They are money pits, don't do it and for gods sake don't believe everything you see on the Science Fiction channel (or YouTube)

 

[ke5frf]

Ke5frf,

I see your point, and its well said...but...one doesn't have to completely understandall principles and mathematics behind an idea to get a working prototype. Of course, in this particular project dealing with lethal voltages and a high power through-put 'tinkering' becomes a hell of a lot more difficult. If something shorts in a 1W DC-DC converter, you may hear a hiss....at 1kW, it'll sound like a shotgun.

As for something to think about....the large forward transformer inside a typical PC ATX power supply could handle that much current. Its not as simple as 'hooking it backwards' of course, not to mention efficiency troubles (its designed for stepping down...) but an ATX power supply has some useful stuff for medium power DC-DC converters.

No, I agree with you. Certainly someone can build an electronic circuit without having the first clue how it works. All you need to do is follow someone else's instructions.

I was referring to his statement that he wants to come up with a new way to increase DC voltage, that he believes there has to be "another way" that doesn't use transformers or coils or some sort of AC or pulsed DC component. Well, there may be some way that hasn't been discovered, but I doubt that it will be discovered by someone who doesn't have an exceptional background in electrical theory.

 

[RCinFLA]

Cheapest route would be to buy a simple DC-AC inverter.

They have boost switcher that takes 12vdc to about 155 vdc. An output MOSFET H-bridge chops the 155 vdc to create the modified sinewave.

You can just use the boosted DC. There is a resistor divider that sets the 155vdc output regulation you can modify if you want lower voltage.

https://www.electro-tech-online.com/attachments/power-inverter-schematic-pdf.32270/

 

[tcmtech]

Transformer step up and inductor buck/boost circuits are the simplest and most practical for that power level. Piezo electric can do it at low power levels, milliwatt levels usually, and so can multi stage capacitor based charge pumps.

But as far as anything else reality still holds supreme! Like it or not.

You may want to shut off the Sci-Fi channel for a few more hours a day and join the real world and possibly pick up some electronics and physics books. You will look far smarter if you did.

 

[electrookie]

OK, at least I am learning

I understand the efficiency issue and what unity, over unity is and I am not looking to defeat that. I am trying to figure out if 12 volts could be bumped to 80 volts (as cited in that 1st article) and then be current boosted as in the 3rd article in that file. It seems to me it is something doable at least to some extent.

What I think I now understand better is that DC has to be pulsed in some manner to do this boosting. And in doing this, DC is then AC because of the pulsed signal. Is this the definition of AC you are trying to get me to see? I have always thought of AC as what comes out of the wall socket and had not realized that DC becomes AC when pulsed.

Aside from that, did anyone look at those articles and get a gist of what I am thinking here? I certainly am NOT looking for "magic" nor "over unity" or any other such. I have been searching for info on boosting DC and put these 2 concepts together and want to know if any of you think there is something that can be done there.

And as for the naysayer, I said I would not get into any discussion over the application, so I will not go there with you other than to ask "How do you know what will work?" "Have you tried it?" It took me a number of years to learn that my wife, who always told me something doesn't work, don't spend our money on "it", yet she had never tried the something to KNOW if it could be done or not. Her and her kind are simply pessimist. Perhaps you know her? I'm divorced now!

So far, no one has addressed the original question's about the articles in the original post. If the low DC can be converted to low current higher DC, can that then be current boosted by the type of circuit in that 3rd article about boosting current. I am of the mind to go ahead and build this just to find out if it can be done. I was just hoping someone out there would have some useful suggestions or advice.

Thanks for your input, regardless...

 

[blueroomelectronics]

Well yes the voltage can be increased at the cost of current. Simple ohms law. But the conversion will require energy itself.

So if you need 100V at 1A your 12V supply will need at least 8.35A at 12V. Add to that the power the converter needs (never 100% efficent) and there you go.

 

[Blueteeth]

I understand that getting more out than what goes in is not going to happen. I am not looking for magic here. But if I have a 100 amp 12 volt battery, I think I should be able to get some serious current for the boosted DC in the end, without going thru AC in the process.

This really depends on what your definition of AC is.

For most non-techie people, they use the term 'AC' to refer to mains voltage, as that is always AC, a sine wave, with a frequency of 50/60Hz, and RMS voltage of 240/115V depending on where you are in the world.

Technically speaking, if you were to turn say a flashlight on an off, you're producing AC from DC. Even if you turn it on and off once a week - that just means the frequency is very very low.

When we're talking about 'chopping DC', what we are doing is just that, turning a DC current on and off. You end up with a square wave which goes from 0v to your supply voltage,12v in your case. That square wave has a DC component (becuse its mean voltage isn't 0), AND an AC component (because it changes). So, ALL forms of power converters 'go through AC' (note, this doesn't include linear regulators). - even many of those 'magic over unity' devices alternate current (even if they are just plain wrong).

This does not mean to say you must convert your DC to 'mains AC' at 60Hz. On the contrary, many switch mode power supplies work at a much higher frequency because of efficiency and component size. Exactly 'how' you use a transformer is dependant on the topology used, be it flyback, forward, push pull, boost etc.. - all of which will switch the power supply current into the transformer at a certain frquency/duty cycle, but vary in the way they use magnetic current inside the transformer to transfer energy from its primary winding, to its secondary.

Flybacks and boost converters 'store' small packets of energy in the transformer core itself, as a magnetic field, then collect the energy when it colapses. This means the size of that packet of energy you can transfer is down to the core material and its size. More power through put = bigger transformer.

Forward and push pull transformers however, maintain an average magnetic flux of 0. They can use smaller cores but require more switches (MOSFET's generally) to control the flux in the transformer.

From what I gather, you are just after a 12V to 100V DC to DC converter at reasonably high power. 1-2kW. The principles are pretty much the same as making the same device but with 1W power, so I suggest you start with that. The differences are of course: current. Another tihng to tihnk about is, say you somehow manage to make a boost converter for 1kW.....as nothing is 100% efficienct there will be losses, and for most flyback/boost converters this is arond 80%. At 1kW, you're losing 200W of power in your circuit....effectively making it a 200W heater. At low power,this heat generation is small, and may require a heatsink, albeit a very small one. At 200W its going to be massive.

So, boost and flyback for this power level is a bad idea. I would look at forward and push-pull converters. Or simply google for 'power inverters', there are many >1kW schematics on the web that range in efficiency and complexity. Some use bipolar power transistors (not always a good choice) but many use power MOSFET's.

Regardless of whether you use an existing design, design your own, or re-invent the wheel whth something new and wacky...you're going to have to use magnetics (transformers) to accomplish the task. By far the easiest way to do what you want is to buy a ready made DC-AC inverter, that outputs 115V AC, rectify it with a full bridge, add output capacitors, and possibly drop the output voltage by 15V (at 20A thats not going to be easy). Or modify said power inverter to lower its output voltage (may not be that difficult depending on whether the inverter uses feedback controlled PWM or not).

As from scratch, look up PWM controllers such as the TL494 or SG3524. Their example circuits will give you an idea of what you're up against, plus, they're quite easy to use and will take the sting out of desinging from scratch.

Blueteeth

 

[tcmtech]

Pulsing DC on and off is still not AC.

Alternating current is exactly what its name states. It alternates back and forth from one polarity to the other. Pulsed DC does not AC.

DC can be pulsed through an inductor and used to step voltage and current up or down. Thats how a buck or boost converter circuit works.

 

[Blueteeth]

Pulsing DC on and off is still not AC.

Alternating current is exactly what its name states. It alternates back and forth from one polarity to the other. Pulsed DC does not AC.

DC can be pulsed through an inductor and used to step voltage and current up or down. Thats how a buck or boost converter circuit works.

I see what you're saying, its not PURE AC, that is, without a DC component, but AC is involved. As you said, AC is a regular change in current direction, that is, it goes above and below 0v, zero crossing. Add a DC component to that so it never drops below 0v...and it suddenly becomes 'not' AC? But chopped DC? Perhaps, that depends on your point of view/definiton.
Without any AC component in your power supply, the input voltage/current does not change. Therefore, inductors and magnetics are out. As I stated in my post, it is about the thread starters 'definition' of AC that determines whether or not his 'converter' will use it.