Simple Switcher Regulator for Midibox projects

[thepcman]

Hi,

I'm a newbie already, have little to talk about the project itself, but i've realised a power supply issue on the designs.

The Core is equipped with 7805, which is a lossy regulator and warms up when loaded above 50% capacity (that's over 400mA or so). This warm up issue also depends on what is the input voltage to the system (that's what the output of the wall adapter is).There are designs which include lots of modules, pots, faders etc, which will load the regulator and may blow it up suddenly. Instead, there's a good option.

LM2575-5V / LM2576-5V Simple switcher regulators use simple buck topology (voltage step down) to regulate output to desired voltage. LM2575 has 1A guaranteed output current and the efficiency is about 88%. LM2576 has 3A guaranteed output current and has efficiency about 76%. All they need to operate is an inductor (330uH for 2575, 100uH for 2576), an input and an output capacitor (330uF is enough for all) and a schottky diode (1N5819 for 2575, 1n5822 for 2576). The IC's work with standard inductor packages.

I've used those for various circuits which include PIC's, LCD's, 74/4000 series IC's and some other stuff. I even drove a waterpump with 1A current. The output voltage is clean enough to work with digital/analog IC's. I have not measured ripples higher than 20mV!!

Another good thing about using switching regulators is you can use smaller wall adapter. As the regulator very low loss and wide input voltage range (upto 40V), say if you need an output  5V 1A, for 7805 regulator, you need a 1-1.1A output adapter (7805 probably won't give 1A output, it fails about 0.8A). But if you are feeding the box via an 12VDC adapter, a 500mA adapter will do it very well if you use 2575.

Here's a datasheet link for LM2575:

http://www.datasheetcatalog.org/datasheets2/20/200304_1.pdf

[thepcman]

OK Here's a complete PS:

regulator.JPG

regulator.JPG