Thread: PSU 12V issue

After reading many posts here in the board i see that one of the main problems in making a power supply is to get the 12V line to give more power, well, how about the L296 Switching regulator from St (www.st.com) it can put out 4A with a Voltage input of 9 to 46V ( i know 9 is a bit high but with a tank circuit i think it would hold up when crancking up the engine). Currently i have (not yet but almost) a PSU that has:


3.3V@10A
12V@8A
-12V@1A
-5V@1A
the 5 volt line has 30A but it also feeds the 12V, -12V and -5V line so
(5*30) - ((12*8)+(12*1)+(5*1), this leaves 37W in the 5 volt line, 37W/5V thats about 7.4A remaining in the 5V line, but since the 12V line isn't always pulling 8A (nor does the negative ones pulling out 1A each) there is always a bit more than just 7.4A in the 5V line.

You have to admit, these are pretty good specs for a home-made power supply. But my problem is SIZE, this power supply is 20cm by 10cm (figure out the inches), it is all MAXIM based, so you can imagine the enourmous number of choke's, schootky diodes, MOSFET, that i'm using.

Thats when i got the idea of looking inside of a normal PCs PSU and i saw that many used ST chips, so i went to their website and found the L296 chip ( http://us.st.com/stonline/books/pdf/docs/1333.pdf ),if i use this chip i don't have to use 5V line to power the 12V one, i could just put the 5V line giving out 13.4A (67W), in order that 12W would go to the -12 line and 5W would go to the -5V line the leaves 50W in the line so 50W/5V = 10A, so the specs would be:

5V@10A
3.3V@10A
-5V@1A
-12V@1A
12V@ at least 4A (could put two chips in paralell to have 8A).

At the best of all, i could reduce DRASTICALLY the size of my PSU

Tell me what you think, is it doable and does ST give out free samples?

Sorry for the long post.