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I've been looking at dc to dc step up converters/voltage multipliers, and they all seem to make it ac or pulsed dc and reconvert it to dc at the end. Is there a way to step it up directly? A clock circuit is pulsing dc, for whoever got my question closed.

Charlie
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  • Am I allowed to use changing magnetic fields in a vacuum? – jonk Mar 13 '21 at 05:00
  • I don't think so. Are you just asking out of curiosity or do you have an application in mind. Maybe if you explain more about what you want to do, people would have some ideas of how you could do it that don't involve magic voltage stepper-uppers. – user57037 Mar 13 '21 at 05:28
  • I would argue that a garden variety boost converter does not actually make pulsed DC, but I am assuming that you mean to rule out switch-mode boost converters. – user57037 Mar 13 '21 at 05:30
  • #mkeith I haven't heard of a non-switch mode boost converter. Could you name one so I can research? – Charlie Mar 13 '21 at 05:32
  • What about DC motor coupled with dc generator ,by adjusting number of poles or conductors you can get your desired step up DC output current ! – user215805 Mar 13 '21 at 06:47
  • Or take two conductor (make a setup like van-de -graph ) such that one store positive charge and other negative charge ,and make a feedback control system which operates the motor of van de graph generator such that you can always get a desired potential difference between two conductors and hence desired current(step up or step down) through load which is connected between those two conductors – user215805 Mar 13 '21 at 06:59
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    Hmm have you considered Explosively Pumped Flux Compression Generators? They can give you a really nice step up, although they're not great for prolonged loads. – K H Mar 13 '21 at 07:26
  • I'm voting to reopen because no-one has mentioned why it's not practical to do it without using AC or pulsed current yet ;) – bobflux Mar 13 '21 at 08:05
  • @Charlie, sorry if I didn't word that very well. I am only aware of boosters that use switch mode (and switched capacitor which someone else mentioned elsewhere). Personally, I don't feel that a switched mode boost converter makes "pulsed DC". It makes DC with some ripple in it, which is not really the same thing as pulsed DC. And the ripple can be removed with a second stage if necessary. However, I understand your question to be ruling out all switched mode DC-DC converters. Let me know if I understand incorrectly. – user57037 Mar 13 '21 at 08:22
  • "is It possible questions" are off topic for this site, please go to the help center for reasons why – Voltage Spike Mar 13 '21 at 18:45

4 Answers4

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If your converter contains a transformer, or inductors, or capacitors, no. These components require some change to make them work to step up DC. We can use an output filter to remove as much of the pulsing as we like.

We usually put up with this pulsing then filtering approach, as we can get power efficiencies closely approaching 100%

There are much less efficient methods that can do the job under steady conditions.

  1. A LED drives a number of series-connected PV (photo-voltaic) diodes.

This device is actually made and sold for the isolated powering of FET gate-drive circuits. It's hugely inefficient in terms of energy out for energy in, but for low power applications where noise and isolation are at a premium, they are fine. I did buy a little 300 mW solar panel and try driving it with a 10 W LED a while ago. They work together much as you'd expect.

  1. An input Peltier, or a power resistor and heatsink combo, drives a number of series-connected Peltiers operating as TEGs (thermo-electric generators).

To the best of my knowledge, these are not sold commercially. I've often mused on this method for getting a small amount of quiet isolated power to an opto-isolated ADC converter, but then I lie down until the feeling passes. I believe the COP (coefficient of performance) for Peltiers is not too bad for small temperature differences, so you may get reasonable energy efficiency if the elements are under-run by a large fraction. At anywhere near their 'rated' power, efficiency would be awful.

Neil_UK
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  • Illuminating a photovoltaic followed by a linear regulator if needed seems like it would do exactly what the OP was after. Nice going! I didn't think of that approach. – user57037 Mar 13 '21 at 08:25
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Yes, there are switched capacitor voltage multipliers. In one type, you put a number of capacitors in parallel across the input voltage source. Then you reconnect them so they are applied to the load in series. In another approach called a charge pump, you put one capacitor in parallel across the input voltage, and then switch it so it is in series with the input voltage and an output capacitor. Both types are illustrated in the switched capacitor section of this article: https://en.m.wikipedia.org/wiki/Voltage_doubler

10ppb
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  • Your link shows A transformer which is AC and the Switch capacitor which shows a clock. – Gil Mar 13 '21 at 04:22
  • This still requires pulsing the input, which goes against what the question asks. – Hearth Mar 13 '21 at 04:22
  • Check out the switched capacitor section of the linked article. I’ll edit... – 10ppb Mar 13 '21 at 04:24
  • I don’t agree. There is no ac or pulsed dc in a switched capacitor multiplier. Just dancing capacitors with unipolar voltages across them that only vary slightly under low-load conditions. – 10ppb Mar 13 '21 at 04:37
  • @10ppb the switching of the capacitors is pulsing dc current. – Charlie Mar 13 '21 at 05:27
  • I did not expect this to be controversial, but I guess everyone takes the meaning a little differently. The point is to try to be helpful to the person asking the question, isn’t it? In an inductive converter there is no V generated at all without dI/dt. Not so for switched capacitors, where all voltages can have arbitrarily small transients. – 10ppb Mar 13 '21 at 05:41
  • It is up to the OP to reject based on the OP's own definition of "pulsed DC." But I certainly felt that your answer was offered in the spirit of being helpful. I see no reason for the downvote. But don't take it too hard. It happens sometimes. I upvoted to help cancel the downvote. – user57037 Mar 13 '21 at 08:29
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Does a Van de Graaff generator count? Or a Kelvin water dropper? Those step up a small, incremental charge to accumulate a large one.

hacktastical
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  • I would consider that pulsed, because it those both have gaps. – Charlie Mar 13 '21 at 05:29
  • I believe a Van de Graff can be constructed without gaps. You could use one to run current through an LED or something rather than letting it spark. But it may be intrinsically noisy due to the frictional method of generation. Also how do you run it? With a DC motor? If a DC motor is not "pulsed current" then you might as well just use a DC motor and a DC generator mechanically joined. – user57037 Mar 13 '21 at 08:32
  • Just take some of the output and feedback to the motor... oh, wait. Something something second law something... – hacktastical Mar 13 '21 at 14:23
  • @hacktastical I am working on an overunity Van de Graff generator. LOL. – user57037 Mar 13 '21 at 19:34
  • @mkeith I didn't know that they could be run without gaps. Thanks. – Charlie Mar 17 '21 at 23:19
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Short of putting a battery in series, no.

Hearth
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