Circuit help! For input: 5v to output:12v DC. Using USB port (laptop)

[ikzton24]

Hello Everybody!!

I want to change my usb fan which is 5v to a 12v source.

I want to create a circuit that would have an output of 12V DC. Its input is 5v DC in the usb port of my laptop.

Can anyone help me with this??

 

[Boncuk]

Why would you want to use a 5V fan with 12V?

It'll burn up within a short time.

Boncuk

 

[ikzton24]

I would change the 5v fan with a 12v fan. All I want is to step up the 5v dc of the usb port to 12v dc. hope you get it.

 

[picbits]

At what kind of current ?

 

[ikzton24]

That's my problem. I don't know about the current of the usb port. The 12v Dc fan can operate at 0.12 Amp.

 

[ronv]

Take a look at these.

**broken link removed**

 

[picbits]

The USB port will support a maximum of 500ma (around 2.5 watts). A 12 volt fan at 0.12 amps is 1.44 watts.

You will need to build or buy a switching regulator which is around 58% or more efficient. The item ronv linked to above should do the job nicely.

 

[ikzton24]

Is this circuit is right for these? take a look at it. **broken link removed**

This is the link of the project https://www.eleccircuit.com/lm2577-5v-to-12v-dc-converter-step-up-voltage-regulator/ the forum disable the comment.

Is the circuit is right for the a usb port source (5v) as input? Or it can cause surge current?

 

[picbits]

It should work ok but you're better off getting the switcher off Ebay as pointed out above as you won't be able to build it from parts for less than they are selling it for.

If you want to be extra sure, put a fast blow 500ma fuse in series with the USB port and the switcher.

 

[WTP Pepper]

Take a look at these.

**broken link removed**

I have a use for these. Thanks for the link.

 

[ikzton24]

If you want to be extra sure, put a fast blow 500ma fuse in series with the USB port and the switcher.

How a fast blow fuse work by the way? I would series it between the INPUT and PIN 4 which is the switch, right?

 

[picbits]

I have a use for these. Thanks for the link.

That seller doesn't ship to the UK but if you go to the UK Ebay and type in LM2577 there are plenty of others who do (and pretty cheaply !)

 

[picbits]

How a fast blow fuse work by the way? I would series it between the INPUT and PIN 4 which is the switch, right?

You can connect it inline with either of the supply pins to the boost converter (preferably the +5v line though)

If there is a surge of more than approx 500ma then the fust will blow and in theory protect your USB port from overload

 

[ikzton24]

You can connect it inline with either of the supply pins to the boost converter (preferably the +5v line though)

If there is a surge of more than approx 500ma then the fust will blow and in theory protect your USB port from overload

Thanks man. I got it. I will try that circuit.