# How to increase an output of 5 volts to 9 volts?

I have a fixed input and the output is 5 volts. What type of design must I create to increase my output voltage to 9 volts with the already given output of 5 volts? I am trying to make this charger project as small in size as possible. Any assistance with this would be great. Thank you all!

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-max-2 years ago

Also don't use a joule thief, buy a proper boost converter chip and build a circuit using it. You can often find them in appliances, but usually only as SMD. (everything is SMD nowadays)

You can also make one with a 55 timer and a MOSFET, and a few op amps, I did that and it worked OK, although my design was a bit convoluted, over complicated, and not efficient. Here is a site with some awesome circuit I have never built! lol

http://www.pocketmagic.net/2012/05/simple-switched...

I don't think there are any boost converter circuits on that particulat page, but there is a lot of other cool electrical and programming things there.

-max-2 years ago

You need to use a boost converter to do that. Google that, it is essentially a type of switch mode power supply that uses the physics behind inductors to boost voltage.

A simple boost converter operates by briefly allowing the current from the positive terminal to flow through an inductor, though switching device like a MOSFET, to the negative or ground. That electronic switch is flipped ON and OFF really really fast (although you can sometimes hear it). Electronic switches are used because it is sort of hard to turn on and off a big switch millions of times per second.

When it is ON, electricity begins to flow through the inductor, and as the current increases, a magnetic field is made in the coil, and it begins to act more and more like a short circuit. However, by that time the transistor is turned back OFF immediately, and in the same way that electricity was slow and reluctant to get moving, it's also slow to stop, so electrons keep trying to force their way through the transistor, and a large traffic jam of all those electrons build up and it WILL overpower the transistor if there is no other path for all that huge buildup of electrons! (in physics, all this happens because of the magnetic field being created and collapsing.)

So now we need a way to store them electrons! We can add a diode and capacitor, so that way all those electrons can now flow through the diode and into the capacitor. When current 'flows' through a capacitor through, the voltage across it will increase because it is charging. Since the diode keeps the electrons from going the other way back down the transistor when it is flipped ON, the capacitor just keeps charging every time the transistor turns OFF and the voltage transient occurs. Every time the transistor is abruptly turned off, the current that used to flow through it now HAS to go somewhere, so the voltage will rise until current can flow through the diode and capacitor and charge it to higher and higher voltages.

If it is allowed to go past a few hundred volts though, those electrons will make a (destructive) path to ground through something (usually the poor MOSFET), destroying it. Obviously we cannot let our circuit make such high voltages, so we need to regulate the output somehow. There is another special circuit that detects the voltage and when it gets higher then say, 9V, and it tells the switching circuit that makes the transistor switch ON and OFF to stop and turn off permanently until the voltage falls just below 9V, then it is allowed to turn back ON.

OnLy_you2 years ago

you can use ti ic,TPS40210DGQR

iceng2 years ago

Want to build it yourself, then use a Joule-thief.....

Want half of all the current of a USB 5V in your 9V output, then you need a switching upverter.

mpilchfamily2 years ago

Where is this 5V coming from? How much current or overall power is needed on the 9V output?

It is important to note, in order to increase voltage you will loose current. So if your using 5V from a USB port then your limited to about 400mA of current. If your 9V device needs more than 100mA to charge then it will never work.

So you need to start looking at 5V to 9V boost converters. Understand how much current you have available from your source and how much you will loose in the conversion.