# Can I put several LM2577 in parallel for greater power?

Discussion in 'The Projects Forum' started by BringMeAnother, Oct 21, 2012.

1. ### BringMeAnother Thread Starter New Member

Oct 21, 2012
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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?

Jun 22, 2012
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Oct 21, 2012
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4. ### bountyhunter Well-Known Member

Sep 7, 2009
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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).

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.

Last edited: Oct 21, 2012
5. ### BringMeAnother Thread Starter New Member

Oct 21, 2012
12
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Thanks. Well, I can always go with brute force. If two doesn't work, I'll put three or four.

Jun 22, 2012
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