Hi, first time posting in this forum. I was wondering with this product I found

http://www.ebay.ca/itm/170792120040...X:IT&_trksid=p3984.m1439.l2649#ht_3694wt_1397

If I need more power than the maximum allowed, can I set up two or more of those in parallel and set them with the same output voltage?

My specific case is that I need 19V output with 5V input. My output power must be 22W, so my input amperage must be a bit less than 5A which is higher than the 3A max.

My question is, if I do put say two of those LM2577 set up with the same output voltage, would the current distribute itself equally in them and would I get the power I need?

 

You would have to use diodes on each output,to prevent feeding back to each other, better still use a single ic of higher rating.

http://www.linear.com/product/LTM4607

 

I think I'll use the diodes for this time. So, to be clear, I'll have to link Vout of each board to a diode so that current only flows out of Vout right? Conventional flow from positive to negative that is.

How much efficiency would I lose with diodes? Not much I hope?

P.S. Would this one do? It has 3A

http://www.ebay.ca/itm/10-pcs-1N540...aultDomain_0&hash=item27c991424e#ht_515wt_906

 

If I need more power than the maximum allowed, can I set up two or more of those in parallel and set them with the same output voltage?

My specific case is that I need 19V output with 5V input. My output power must be 22W, so my input amperage must be a bit less than 5A which is higher than the 3A max.

That is not correct for calculating input current and power for a switcher. The input peak current is not a simple DC power conversion equation. The peak switch current will be a lot higher than the average value.

Read the data sheet for details (page 15).

http://www.ti.com/lit/ds/symlink/lm1577.pdf

The peak allowable is 3A, but with ripple current and duty cycle, the average input current is probably closer to 2A which means about 10W total input power. Subtract a bit for efficiency, and it leaves about 8W - 9W ballpark for load power from each board running 5V input.

I don't think you could get 22W total out of two of these at 5v input.

 

Thanks. Well, I can always go with brute force. If two doesn't work, I'll put three or four.

 

These are better dual diodes used in atx power supplies.

http://cpc.farnell.com/on-semiconductor/mbr20100ctg/diode-schottky-2x10a-100v/dp/SC07394

http://www.farnell.com/datasheets/468452.pdf