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I needed to power my Dell laptop without having 220V (because my inverter is burnt in the middle of nowhere) in my van.

By using a boost converter that can deliver the required power, I simply set the output voltage to 19.5V and used a spare cable to deliver the power to the laptop. Without the middle pin connected I knew that laptop won't be able to communicate with the charger, therefore it will refuse to charge the battery, but that was okay.

However, after a while I discovered that Dell laptop was degrading its performance by around 3/4 if an original adapter is not found. The only solution at this point is establishing the required middle pin communication.

Is it possible to establish the Dell Charger Identification without using special tools and electronic components?

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    \$\begingroup\$ While it's wonderful that you got yourself out of what sounds like a challenging field situation, this is not an on-topic design question nor a repair question supported by design details. Probably this belongs on a computer usage site, maybe superuser SE. \$\endgroup\$ Oct 5 '20 at 22:31
  • \$\begingroup\$ Check your BIOS settings. I noted on my Dell laptops when I plugged in an 'underpowered' charger, it had asked if it should remember the charger or some such, and, like you, I find the computer runs slower in that mode. It only asked me that once as the choice was stored in BIOS. So it's a bit of a wild guess, but maybe there's a BIOS setting you can tweak to get it to ignore the lack of communication with the charger. If the wild guess is wrong, no harm no foul ;) \$\endgroup\$
    – Kyle B
    Oct 5 '20 at 22:44
  • \$\begingroup\$ @KyleB There is no such in the BIOS. Moreover, some users in dell.com reports that disabling "Intel Speed Step" option in the BIOS would put the laptop in high performance mode all the time. However, in my case disabling that option had put the laptop in low performance, even when it runs from the battery. So, I guess, there is no option in the BIOS suitable for this case. \$\endgroup\$
    – ceremcem
    Oct 5 '20 at 23:27
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    \$\begingroup\$ @ChrisStratton I really want to understand: As tags say, it's a "hacking" and hacking is obviously a valid topic. It is all related with electronics, there is nothing to do with a computer. The computer part is told to explain the background and motivation, that's all. This is all about using a 1-Wire component without removing it from its original device and establishing the communication. How is such an electrical operation related to Superuser SE or anywhere else? \$\endgroup\$
    – ceremcem
    Oct 6 '20 at 9:22
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    \$\begingroup\$ No, "hacking" products is generally not a valid topic here. This site is really about original design questions, and to a very limited degree other things which can be stated in a way that makes them approachable as if they were original design problems. That some tag exists does not mean a question belongs here. In terms of where your question and self answer might fit, the people it could be useful to are computer users not electrical designers. \$\endgroup\$ Oct 6 '20 at 13:38
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There are solutions around if you google for "Hacking Dell Charger Identification". However, they all require specific microcontrollers, programmers, PCB, soldering, etc.

Since 99.99% of SMPS topologies are similar, I decided to use the output stage of original charger as a whole. I cut the original charger's 19.5V cable, reconnect all cables, connected the external source's (+) and (-) in parallel.

enter image description here

How does the OPTIONAL line work?

If you connect the OPTIONAL line, the output stage of original power supply (OPS) is powered by the external power source. The green led of OPS turns on, any circuitry in the output stage of OPS starts working (for no reason, this is kind of waste of energy). The benefits are:

  • You use the output capacitors of OPS, thereby build a greater filter.
  • You use the OPS' 19.5V cable (you won't need a separate 19.5V cable in this setup)

Beware that any voltage surge from the external power supply may also kill your OPS. You have been warned.

Whether you connect the OPTIONAL line or not;

According to this investigation, the 1-Wire chip's 3rd pin is not connected to a power source. That must have meant that the 1-Wire IC is configured to use "Parasite Mode" power.

enter image description here

So connecting GND and Middle-Pin of OPS and laptop is sufficient to power the mentioned 1-Wire IC inside the OPS. When the laptop initiates the communication, the signal will both carry data and power.

I tested unconnecting the OPTIONAL segment and I confirm it works.

Application

Here is the tested and working application of above schema:

enter image description here

Results

Now the Dell laptop both charges the battery and runs in native performance with the external power source.

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  • \$\begingroup\$ What's going on with the "optional" wire? How would the signalling circuitry in the original brick get power without it? How would you know that adding it is safe, when you don't know what failed in the original? \$\endgroup\$ Oct 5 '20 at 22:32
  • \$\begingroup\$ @ChrisStratton The original power supply operates normally when 220V is present, so there is no reason to suspect any harm by its output stage. I added explanation of 1-Wire parasite power mode in my answer, please see the edit. \$\endgroup\$
    – ceremcem
    Oct 5 '20 at 23:21

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