So explain to me....

[PspKicks316]

DC to DC step up converters.

Say... maybe 3v to 500V.
Like a photoflash capacitor charger.

[802Chives]

a DC step up converter uses magnetics to build up the voltage potential as well as some diodes to block the flow of current in one direction and capacitors to smooth the output.  Magnetics are inductors or transformers, and in the case of a flash circuit it is common to use a step up transformer in order to generate a high enough voltage to fire the flash bulb sometimes in the thousands of volts.  In the following link they use a capacitor as an intermediate stage between two transformers:

http://electronics.howstuffworks.com/camera-flash1.htm

the thing is with stepping up voltage is you will proportionately step down your available current as well as take around a 10-20% loss due to the effeciecy of the circuit. 

Reguardless of what type of DC to DC step up converter you go with, the basics consist of a circuit that can switch current on and off to your storage medium at a very fast rate.  It will use a clock oscillator that operates generally in the kHz to MHz ranges much the way a computer processor or microcontroller in order to time the switching of the converter.

The reason i say storage medium rather then magnetics or inductor is that there does exist a type of step up converter that utilize capacitors only as a storage medium which is called a switched capacitor step up converter.

The type of step up converter depends on the application so if you have something in mind feel free to spill the beans.

[PspKicks316]

Nope that helped tremendously. Thanks
Post Merge: March 11, 2010, 12:19:06 PMActually, with the oscillator transistor does it have to be a specific one? Or can any NPN or PNP (Which?) one work?

And can something other than a neon lamp be used?

[802Chives]

honestly i havnt played around with anything as high voltage as a neon sign power supplys or even flash circuits.  Mostly i have done handheld battery applications of like 3v to 12v.  The most impressive supply i did bumped 12V to 75V @ 1A continuous draw.

the big difference with say a flash circuit to neon supply is that a flash circuit is a pulsed power application where very high voltage and very low current are needed for a very short amount of time ~mSec.  the Neon supply has to provide a high voltage and low current continuously so the designs will vary considerably.

The question about the transistor is a good one and there are many designs that utilize a high speed NPN transistor.  Probably not a 3904 as that is general purpose, however there are specific transistors designed precisely for this application.  Mosfets are rapidly replacing transistors for switching power supplies as they are much lower loss however they are more expensive.

Diodes are specific for switching power supplies as well, they need to be high speed and low loss.  Schottky diodes are perfect candidates for the task.

You could spend the better part of 4 years in college learning about power supplies.  My expertize lies in DC to DC converters for battery applications 3-24V and that was several years of designing circuits after quite a few years of electrical classes.  My design process would start with choosing an IC that was appropriate for my requirements and then I would lay a circuit board to try the design.  takes a lot of app notes and part sourcing as well as a fair amount of trial and error.

so I really cant help you more specifically then general information without knowing what kind of trouble you are trying to get into

[PspKicks316]

Don't worry about the trouble

Would I be able to just get a diode from radioshack and use it?

Would you know how to step 3v up to 500V?
Or can you charge a 500V capacitor with less voltage than that?

I'm interested in the math involved in finding the ratings of each part needed, too.

Thanks!

[FOOKz™]

For future reference:

Voltage increases and current decreases
Power In = Power Out

Voltage decreases and current increases
Power In = Power Out


** Power never increases in a transformer, voltage multiplier, or any EMF trading type circuit.


Some people have the great idea of "powering their house" with a 9 volt battery when they make a voltage multiplier. -- no good because you will have high voltage, low current.

Its more efficient to transfer high current, low voltage power to a source because of Eddie-current loss is minimal when voltage is low.

To drive halogen lights and neon lights doesn't require much current at all unless it has a filament since the gas inside only needs a buzz of voltage to get the atoms excited!

[PspKicks316]

Okay so, use that for indicators. Got it.

What about the rest=P