Hello,
for a study project, me and a fellow student created a circuit to convert a wide range input voltage to 13V.
These 13V are to charge a batterypack.
The voltageregulation circuit is based on the buck/boost IC LM25118.
Our problem ist, that the circuit does not behave like intented.
> Below 10V input voltage it converts it into ~6V and below 10V it shuts down.
What ever the problem is, we assume the problem is related to the parts which are crossed out or marked as N/A in the application notes:
http://www.ti.com/lit/ds/symlink/lm25118.pdf (Page: 29)
http://www.ti.com/lit/ug/snva614b/snva614b.pdf (Page: 11)
One big issue for us was, what does it mean "Do not place"? Open ciruit or shortcut?
Both of course, depending on the removing part.
So we tried different possibilities.
General rule: parallel parts are open; series parts are closed.
We expierienced different behaviours by experiementing different circuits.
On one trial, the buck mode was working. But we forgot the precise combination, unfortunately. ;)
So, finally we took the combination suggested in the user's guide:
http://www.ti.com/lit/ug/snva614b/snva614b.pdf (Page: 8)
- C14; C19; R7; R13 open circuit (DNP... Do not placed?)
- R1 shortcut (equal to 0R)
- D1 replaced with 1N5819 to fit the proposal in the list. (It's not just crossed out. ;) )
Again, the result is:
> Below 10V input voltage it converts it into ~6V and below 10V it shuts down.
Do you have an idea what we did wrong?
If it's helpful, here is our circuit diagram:
https://drive.google.com/folderview?id=0B__8TgcLX5sSTFVIeU00NXU0TVk&usp=sharing
Part mapping:
D1 --> D13
R1 --> R49
R7 --> R48
R13--> not in diagram
C14--> C44
C19--> C42
We would be very thankful for every hint you have for us.
Thank you very much
Fabian
Berlin/Germany