[ltp] self-made external battery for laptops project

[Thomas Hood]

On Fri, 2002-04-19 at 22:20, Richard Neill wrote:
> I would recommend you add the following to your protection circuit:
> 
> INPUT +                                                  OUTPUT +
> 
> 0--------[--X--]------+------------+-----------+-----------0
>                        |            |           |
>            fuse        |            |           |
>                        |      zener |           |
>                        |            |   /       |
>                      __|__       /-----/     _______ +
>                      \   /      /  / \                 capacitor
>               diode   \ /         /   \      _______
>                      -----        -----         |
>                        |            |           |
>                        |            |           |
>                        |            |           |
>                        |            |           |
>                        |            |           |
> 0---------------------+------------+-----------+-----------0
> INPUT GND                                               OUTPUT GND
> 
> 
> The diode is there to prevent against reverse polarity.

Erm.  The first diode shouldn't be there.  Either that or
the "fuse" element should be labelled 'cigarette lighter'.


> The zener is rated at a little over the voltage you expect to supply to 
> your laptop. It will help with surges and over-voltages. Again, in 
> normal use, it should not conduct, and the aim is to protect the laptop 
> by crowbar-ing the supply for long enough that the fuse will blow.

You might want to stick a MOV in there too.

--
Thomas Hood



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