Maker Pro
Maker Pro

LM3478MM Sepic problem

L

legg

Jan 1, 1970
0
Hello experts

Still rather new to the world of SEPIC, I have a problem with a design.

I have made a circuit based on the datasheet for the LM3478. It is intended
to run with Vin from 10V to 32V and deliver 24V out with a maximum of 4Amps.

My testsetup runs at 32V input. The circuit is as can be seen here:
www.impc.dk/scm/lm3478sepic.pdf

A colleague of mine recently built something quite similar but with the
LTC1871 controller instead. But I'd rather use the national part, since we
already has this part in stock.

When I run with no load, output is 24V and everything is nice. But when I
load the darn thing, even only by one amp, everything gets so hot and
eventually the sense resistors crack.


You posted a similar thermal problem with the same IC and a similar
power train in Sept of last year.

How was that resolved?

RL
 
H

Henrik [7182]

Jan 1, 1970
0
By engine company 89 and two ambulances ... ? :)

Haha ;-) No, actually. By following the suggestions of that time, I switched
to using inductors that were better for the job at hand and by picking a
MOSFET that did not challenge the driver as much, I was able to get that
design rolling. Even without making a single modification to the PCB's.
Apparantly now, my luck has changed.

Today was familyday, but tomorrow I'll go in and try all the suggestions
that have been set forward since my last post friday evening. Hopefully I'll
get something running then. When I go tell the bossman I need extra time and
money for redesigning and prototyping this one all over, I would feel a lot
more comfortable if I could add a "but now I know how-to" ;-)

Thank you all, who has kindly replied. I value this alot.

Best regards
Henrik
 
Top