A way to boost a PSU output

[Dave]

G'day all, I have a small laptop PSU that I'm using for a portable HD
based MP3 player.

It can take an input voltage range of 10-18.7V DC and provide:

+5V @ 4A
+12V @ 0.7A
-12V @ 0.1A
-5V @ 0.05A

It works fine from it's normal switchmode AC adapter, (17VDC @ 2.3A
output), but powering it from the car cig. lighter, (12-14.4V), doesn't
seem to provide enough 'oomph' to spinup the drive, (about 1.5A @ 12V).
After it's spinning it only uses about 300mA @ 12V, 500mA @ 5V.

I was just thinking of using a zener to provide an alternative 12V
supply, using a power transistor to increase the current handling.

Can't use a 7812 or similar because there's not enough voltage drop
across it for it to work.

I'd rather not go to the trouble of building another PSU, (ala the 12V
ATX site).

Anyone else got a 'simple' solution I could use?

TIA,
Dave

 

[Spajky]

On Wed, 13 Oct 2004 21:07:18 +1000, Dave <QBXVRAVCYLPD@spammotel.com>
wrote:

G'day all, I have a small laptop PSU that I'm using for a portable HD
based MP3 player.

I'd rather not go to the trouble of building another PSU, (ala the 12V
ATX site).

Anyone else got a 'simple' solution I could use?

http://users.volja.net/jerman55/AutoPSU-atx.zip
--
Regards, SPAJKY ÂŽ
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
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[Dave]

Spajky wrote:

On Wed, 13 Oct 2004 21:07:18 +1000, Dave <QBXVRAVCYLPD@spammotel.com
wrote:


G'day all, I have a small laptop PSU that I'm using for a portable HD
based MP3 player.


I'd rather not go to the trouble of building another PSU, (ala the 12V
ATX site).

Anyone else got a 'simple' solution I could use?


http://users.volja.net/jerman55/AutoPSU-atx.zip

Thanks - it looks like I might have to use the 12V section from either
yours or Mike Warren's site.

Dave