Cytron Technical Forum

From ribut: I want to convert 5V DC supply from a DAQ card to 12V to run a fan. Which voltage regulator is suitable for me?

This is from Caesar:

Dear admin,

How can I convert a 5V to 12V? Is there any components or microchip can help me through that?

I made a research that IC LM2577 can do the conversion but the product is unavailable in cytron.com.

TQ

Seems like more and more is interested in smps technology now. It's a good phenomenon indeed!

Caesar,
Congrats, you're on the right path! Boost, step-up, flyback, sepic...and etc are the key word you can use to search for more information. There're many ICs designed for DC-DC conversion. Simple Switcher is the series of product from National Semiconductor, and lm2577 is one of them. This product has power transistor or mosfet integrated in the chip itself, so you don't need to put an external switch. By following the application examples provided in the datasheet, you can make it. The hardest part would be getting the correct inductor for it. Cytron doesn't have that kind of inductor for power conversion in stock. So you need to look from other source.

Mr sich
Is it this LM2577 can be control by PWM?
cz i wan vary the output voltage

You can look for LM23577 with the output you want. I remember there's LM2577-12 which outputs 12V if your connection is correct and another one named LM2577-ADJ which allows user to adjust the output voltage using a voltage divider. So what you need to do is find the datasheet and read it properly! There might be some other models with different maximum output current too. Try to search in National Semicon's website.

You can also try from texas instrument.

Take a look at this item here. No need to worry about the coil and fully adjustable output.

http://cgi.ebay.com/LM2577-DC-DC-Step-U ... 255ed8778a

Allen

I use transistor circuit to power 12v fan from 5 volts. It works for small 90mA fan.
Schematics is here: http://pic.hitechworld.org/dcdc.html
It can use 22uH/47uH or 47uh/100uH. Easy to test this circuit on breadboard.
It's important to use good diode for 5v -> 12v.

That circuit looks cool and I have bookmarked it in case I need it!

I have already ordered some LM2577-adj and some LM2575-5V and have used a few of them in my projects. They were running cool and has been running for a few weeks without a heat sink.

Last time I also made a one transistor dc/dc inverter to step up 1.5 volts to 3V to light up a white LED. I forgot what is the web site. It was using a NPN and a ferric ring with just a few turns of copper wire for stepping up the voltage. I'll to find the site and post it here. I am sure if the input is increased to 3V, it will be able to get an output of 5V to run a PIC.

Allen

from 5V to 12V, for a fan. my brushless fan for pc stated 4W power, means that if using 12V, it needs (4/12)=0.33A. 5 to 12 means it a step up. am i right? i've checked LM2577T-12 datasheet, and the sample circuit use IN-100U (inductor 100uH), available at cytron. the diode used in sample circuit is 1N5821, can use 1N5822 (available at cytron). i really recommend cytron to make these dc-dc converter/switching/regulator ic available at cytron as will encourage us to make more amazing projects in the future