Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Dell Laptop Charger?

Status
Not open for further replies.

MikeMl

Well-Known Member
Most Helpful Member
Dell Latitude 810 Laptop and its 19.5V AC-powered charger: The charger plug seems to have three coaxial connections, the outer sleeve, the inner sleeve, and a center pin (see pix).

When plugged-in, 19.5Vdc appears between the outer sleeve and the inner sleeve, with no definite voltage on the center pin, measured with respect to either outer or inner sleeve.

Is the center pin some sort of feedback input to the charger? Is it even connected?
 

Attachments

  • 021.gif
    021.gif
    140.4 KB · Views: 166
There is some means where the charger can tell the laptop what type of charger is connected.

If you connect a charger for a small laptop to a large laptop, the large laptop knows and will inform you on the screen that the charging rate is limited.

I believe that this is done with some serial data from the charger to the laptop.
I don't have any details of the protocol.

JimB
 
I think that the Dell chargers have a Dallas / Maxim 1-wire ROM on the centre pin. The laptop checks that is correct before charging, and uses it to know how much current it can take.

The copy Dell charger I got from eBay had a TO-92 1-wire ROM added to a standard SMPS.
 
Ditto to what JimB and Diver said.

And my HP Pavilion has the same setup. I have two power adapters. The original, and an aftermarket unit. One at home and one at my office, so that I don't need to carry the adapter back and forth.

The laptop knows which adapter is connected and gives me the an alert message when running on the aftermarket adapter.
 
Dell Latitude 810 Laptop and its 19.5V AC-powered charger: The charger plug seems to have three coaxial connections, the outer sleeve, the inner sleeve, and a center pin (see pix).

When plugged-in, 19.5Vdc appears between the outer sleeve and the inner sleeve, with no definite voltage on the center pin, measured with respect to either outer or inner sleeve.

Is the center pin some sort of feedback input to the charger? Is it even connected?

Hy Mike,

My Lenovo T520 power connector has exactly the same set up. But there are only two wires connecting the PSU to the plug: 20V and 0V. The cable is coax with the center being 20V. The coax cable and the inline filter are necessary to meet EMC requirements.

I have also repaired a few other IBM PC laptop PSU cables, which typically fail just before the plug due to flexing- there has never been a third wire from the PSU.

Also, I have adapted laptop PSUs for other uses and have traced out the circuits a few times; there has been no sign of any comms/intelligent functions. They are just straight forward SMPs.

The T520 does object if a PSU with too lower current capacity is connected, but I always thought that it knew by the voltage sag when taking a high current. It does not mind if a high current capacity voltage source is connected though. When new, the T520 occasionally complained about a too lower capacity PSU, even though it was powered from the proper Lenovo PSU for the model. This was a false alert and dissapeared with BIOS/OS/utility updates.

I don't know about Apple, but on IBM type PCs I suspect that any communications would be done over the power line. This is only speculation though.

Incidentally, laptop PSUs common failure modes are: adhesive retaining one of the big inductors has unstuck and the inductor has either fractured its self lead or torn the PCB trace, and breakdown of the mains plug on the cable and possible collateral damage to the mating receptacle mounted on the PSU.

spec
 
Last edited:
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top