Is there an easy way to multiply / step up DC voltage??

I know with transformers/coils I can step up AC voltage easily, what about DC voltage? Is it possible? Will capacitors and coils be able to multiply/step up voltages? How can it be done?

Reply to
Bill T
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a 555 timer or something similar would be a good start, then a series of capacitors and diodes, the same type of circuit as a tripler in a color TV

Oh by the way, I am sure modern technology will not let step up DC voltage, this is why you have to chop up the DC into square wave with a 555 timer IC

If you or someone can find a way of stepping up pure/straight DC to a higher voltage, you might get a Ph.D. with honors.

Reply to
Eric

It's called a step-up, or "boost" DC-DC converter. There are special ICs dedicated to this task which come in two types, inductor based and capacitor charge pump based. Try maxim for starters:

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Some tutorials are here:

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Heaps extra links here:
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You can also build your own with discrete components if you want.

Dave :)

Reply to
David L. Jones

Maxim is one company that produces chips that can either step-up, step-down, or invert voltages. They even have chips that use capacitor charge pumps. The MAX232 chip (it's a ttl to rs232 line driver) has charge pumps on board that can give you about +10V and -10V from a 5v supply, albeit with a very limited output current.

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Linear Technology even has a Spice program (LTSpice/SwitcherCADIII) that allows the user to evaluate switching designs before even building them.

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There's also an active Yahoo Group that is dedicated to users of the LTSpice program.

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Reply to
dmm

Hello Dave, you are clued up on switchmode power supplies. Your last comment "You can also build your own with discrete components if you want." interests me.

A mate of mine has a large 12V car battery in his caravan which he charges via a large isolating diode. The caravan battery is parraled with the car battery but has the diode in series with it. So current can flow from the car to the caravan battery but not the other way. Problem is the caravan battery doesn't get a good charge this way due to the isolating diode.

A DC to DC converter made with discrete components, or common ICs that could charge the caravan battery with

10s of amps and then backs off to a trickle current in the same way the car battery charges up would be a nice thing to have.

Sorry for sucking your brains here Dave, but I just had to ask for your ideas and suggestions. My mate doesn't want to use fancy switchmode power supply chips that are expensive. hard to find, here today but unobtainable in several years time type of thing.

Thanks for those links,

Regards, John Crighton Sydney

Reply to
John Crighton

"John Crighton"

** Lick , lick, lick

** The motive.

** Utter bullshit.

........... Phil

Reply to
Phil Allison

Maxim are good for one offs / samples

Maxim can be dam hard and more expensive to get bits than National , ST or others if you need quantity and even for small quantities.

DC-DC converter chips - Boost , Buck and switching regulators

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has a nice calculator

ST

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Linear

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ST662ACN is good for 5v to 12/20 volts 30mA

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good for making a usb pic programmer

Reply to
Alex Gibson

If the diode is causing that much of a problem when charging the battery, then why not put a (large) relay across the diode, and have it activate only when the alternator is actually running, (charging)so as to bypass the diode. I believe also that SC described a device to replace this diode, and instead used a FET to minimise the losses.

Alternately, connect directly to the AC windings of the alternator (before the alternators internal diode pack) bring the wires out and install a second diode pack on them, take this supply direct to the caravan. A suitable diode pack should be obtainable from an auto electrician

If you are getting bad losses like this at the caravan battery, you should also look at the diameter of the wire running from the car engine bay to the caravan, and the connectors used A diode should lose less than 1.0v under load, I would bet that you would lose substantially more than this (under load) in this wire run to the caravan, unless you used some pretty hefty cable, and good solid connectors. Remember, you could be looking at a cable run of easily around 10 metres or so, and with a load of "10's of amps" at 12v, the cable is going to have to be bloody big cross section area to minimise losses !

Dont forget to have a really good earth too, between the car and van chassis.

Reply to
jj

An isolating switch and a separate charger should fix that problem, John. Your mate may be able to pick one up from a car parts retailer. My brother has one in his Formula Ford, so they shouldn't be too expensive. Connect up a mains based lead acid charger and he can trickle charge it on-site, if there's AC available of course. 8-)

Reply to
dmm

Hello Phil, I live at 18 Talwong Street Hornsby Heights NSW

I don't get involved in slanging matches, or making personal insulting remarks, life is too short. If you are interested in sorting something out face to face with me, techo or otherwise, come on up.

I am quite happy to discuss techo stuff with you or anyone but if involves personal insults then forget it.

I don't very much care for your lick lick remark, take that back and we can continue this discussion. Over to you Phil.

Regards, John Crighton

Reply to
John Crighton

"John Crighton "Phil Allison"

** What damn bad luck.

** The Jock jerk is a raving psycho.

** Boo, hoo - poor baby.

** It was a blatant example of public arse licking.

Revolting stuff to see on a NG.

This quote from the same post conform you motive:

" Sorry for sucking your brains here Dave, but I just had to ask for your ideas and suggestions. "

TIP:

Don't post site like this again if you do not want to draw justified criticism.

........ Phil

Reply to
Phil Allison

so how does a tripler in a color TV works? When you step up the voltage, say if you chopped up the voltage to a square wave etc. what's the limit to the stepping up? ie. how many times you can multiply it? How many volts you can step it up to?

Reply to
Bill T

Hello jj, thanks for those suggestions, I will pass them on to my mate.

The reason I was asking Dave about the smps approach was also to directly charge a 24V battery bank used in the caravan without the hassle of switching two small 12 V car batteries from parrallel to series. I haven't come across a smps charger project in the magazines or the web that would do this.

Regards, John Crighton Hornsby

Reply to
John Crighton

Yes, my friend does that.

jj's suggestion with the FET or relay sounds like the easiest improvement to make.

Regards, John Crighton Hornsby

Reply to
John Crighton

Another method before adding a boost charger (which would be a good idea) is to make up a circuit (just a darlington transistor etc) that turns on a relay or FET to connect the auxiliary battery only when the motor is running. This removes the need for a diode. I have this scheme on my vehicle, the "high" or "low" found on the oil pressure lamp controls the relay.

--
Regards ......... Rheilly Phoull
Reply to
Rheilly Phoull

Hello Rheilly, a bit more icing on the cake! Thanks for that. Regards, John Crighton Hornsby

Reply to
John Crighton

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the top diagram has a circuit (multwork.gif), this is driven from a transformer winding but it could be driven from say a 555 timer

so how does a tripler in a color TV works? When you step up the voltage, say if you chopped up the voltage to a square wave etc. what's the limit to the stepping up? ie. how many times you can multiply it? How many volts you can step it up to?

Reply to
Eric

There are commercial devices available that do this for you. Go to your local 4wd accessory shop and ask them.

Reply to
The Real Andy

Here's one South Australian mans approach to getting 67.5 VDC or more out of four AA cells. A very neat approach using modern semiconductors, I thought.

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PH

Reply to
Peter Howard

"Peter Howard"

** I agree - a nice example of simple design and effective use of "garden variety" componentry.

.......... Phil

Reply to
Phil Allison

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