how to make ~30v from 2.5v ?

[darron]

hey there guys. i've got a project in mind, and i need to get 2.5 volts up to around 30 volts. what's the best way to go about doing this? my first though is a transformer but i don't understand transformers very well. i also looked at voltage multipliers with cap/diode combos, but that might not be well suited for the purpose since the voltage difference is so much. i also looked at the 18v from 9v article on the geofex site but it's very similar, and according to the specsheet the IC used probably won't meet the amp requirements. is there some sort of inverter that i could use?

could someone please point me in the direction of a product or schematic etc. that will do this? i live in australia but i don't mind waiting for the part from the USA if someone can push me in the right direction. any help would be greatly appreciated.

by the way, it's for a power supply project

thanks HEAPPPPPS

[GibsonGM]

Maybe some more info would be useful, Darron?  Are you talking stepping 2.5VAC up to 30VDC?  What current is available? If you used a transformer, there will be trade-offs. 
How about just using another transformer, and making a separate 30v supply (or use a tranny w/multiple secondaries)?

Jumping 2.5vDC up to 30V DC would be a whole different game!  Some sort of power transistor circuit, maybe, provided you have >30V available to play with elsewhere in the circuit...

[darron]

Maybe some more info would be useful, Darron?  Are you talking stepping 2.5VAC up to 30VDC?  What current is available? If you used a transformer, there will be trade-offs. 
How about just using another transformer, and making a separate 30v supply (or use a tranny w/multiple secondaries)?

Jumping 2.5vDC up to 30V DC would be a whole different game!  Some sort of power transistor circuit, maybe, provided you have >30V available to play with elsewhere in the circuit...

hey there GibsonGM, thanks for your interest (:

i want to get 2.5vDC up to 30vDC. available current is HEAPS since it's coming from capacitors. the plan is to build a matrix of several 55f capacitors, charged at low voltage, and then pump those up to go through 9vDC regulators. I've already got a way to charge them, and make a battery power meter, but getting them to the right level (efficiently or not!) is something that i'd like a little bit of help with.

thanks!

darron

[Sir H C]

To do this you would need a synchronous boost regulator.  These are made by Linear Tech, TI among others.  The problem is that these are  not trivial circuits to design or lay out.  I know that Linear Tech has sample modules you can get with a small board and all the other bits.  If you need any current at 30 volts it is going to be a huge current at 2.5 volts since the power at the two voltages is the same, so lower voltage = higher current, over 10x the current.

[darron]

To do this you would need a synchronous boost regulator.  These are made by Linear Tech, TI among others.  The problem is that these are  not trivial circuits to design or lay out.  I know that Linear Tech has sample modules you can get with a small board and all the other bits.  If you need any current at 30 volts it is going to be a huge current at 2.5 volts since the power at the two voltages is the same, so lower voltage = higher current, over 10x the current.

hi. the source current shouldn't be a problem since it's coming from capacitors, should it? i've googled boost regulator spec sheets and the minimum voltage that the sort of begin working at is around 2v to 3v. the capacitors are going to drain and be around 1v or so after a decent amount of usage and i'd like to get as much as i can out of them. essentially i'm looking for something that's going to give a 10-12 times voltage gain. if i can get something to just regulate it to a constant 9v regardless of source voltage (to a point of almost say 70% exhausted) then that would be jut as good or better.

[Sir H C]

It makes more sense to go from the low voltage directly to 9 volts.  You can regulate within 50mV or better with many regulators, and your efficiency will be a lot better than going to 30 and then a linear regulator dropping back down.  Still getting below 2 volts you might have to do something more convoluted, but since they make regulators that worked of a single AA battery, it is possible to go there too.  Also by going straight to 9 volts, there are more options for devices to do this than if you went up to 30 volts.

[darron]

It makes more sense to go from the low voltage directly to 9 volts.  You can regulate within 50mV or better with many regulators, and your efficiency will be a lot better than going to 30 and then a linear regulator dropping back down.  Still getting below 2 volts you might have to do something more convoluted, but since they make regulators that worked of a single AA battery, it is possible to go there too.  Also by going straight to 9 volts, there are more options for devices to do this than if you went up to 30 volts.

Thanks Sir H C, I'll look into this one a bit better. So far searching Linear Tech and TI, all the voltage ranges are not working for me. If they are to accept the <2.5v they don't seem to output much past 5v, or they output to about 30v but only from 3v or so.

Still, I'm happier if I can find a boosting regulator, that sounds heaps better.

hunting hunting...

(:

[darron]

how about this?
http://www.sipex.com/Files/DataSheets/sp6690.pdf

found it here:
http://www.sipex.com/productDetails.aspx?part=SP6690

[Sir H C]

That one should be workable.  Trick is that the WLED ones are often trying to keep a current steady not the voltage.  So where the diodes are, you put a resistor and you have a voltage divider, and boom you are set.