I came across this power supply for an IBM laptop at the thrift store - couldn't pass it up for a couple bucks.

But instead of the typical rating of x volts at y current, it's labeled like this:

16 - 10 Volts

2.2 - 3.2 Amps

It's a single output supply, with two conductors.

Most wall-warts are fixed voltage. Increasingly, some wall-warts are constant current for powering LEDs. This one is a bit of a mystery.

 

I wonder if it negotiates the power like USB PD. I would have expected more wires if it does.

Or maybe it's a regular power supply but for some reason had to give it a rating based on two different loads.

 

It seems to be an "unregulated" power supply. That is, at 2.2A, the voltage will be about 16V. Once you draw 3.2A, the voltage will drop to 10V.
But, that seems a bit of a large range to me. Many capacitance filtered wall-warts will show this type of behavior.
Are you sure it has only 2 output wires? If there is a 3rd wire, it may switch the voltage upon detection of the laptop.

 

Transformers have internal resistance that causes the output voltage to fall as the current increases.
A transformer rated at say 10VDC would output about 16VDC with no load.
This is saying that it can deliver 2A at 16VDC and 3A at 10VDC.

 

Of that, I am well aware.

This is a switching power supply, which usually are pretty tight in their regulation.

Also most switchers, when pushed too hard, drop their output voltage, so the current falls.

 

I do have a bit of experience in this area. Here's a study I did some years back.

AC-DC Power Supplies-- Using Wall-warts

 

Look at the input specs. It is rated 100-240V 50/60Hz. I would expect that based on the input voltage the output voltage would differ. Apparently unregulated and dependent on regulation within the supplied equipment.

 

This one is a bit of a mystery.

This is a switching power supply, which usually are pretty tight in their regulation

I do have a bit of experience in this area. Here's a study I did some years back

Hello there nice to meet you so to speak.
I would say you are an expert in Wall warts.
https://sites.google.com/a/clever4h.../home/ac-dc-power-supplies---using-wall-warts

 

Searching P/N 85G6670 85G6670 Adapter (psaparts.co.uk) Tells me it's for a Lenovo Laptop and rated 16VDC out (15-17VDC). Apparently universal input with the proper cordset.

 

It seems to be an "unregulated" power supply. That is, at 2.2A, the voltage will be about 16V. Once you draw 3.2A, the voltage will drop to 10V.

This link seems to support that idea.
https://memoryclearance.com/85g6670-ibm-16v-2-2a-10v-3-2a-ac-power-adapter-for-thinkpad-750-755.html

 

I do have a bit of experience in this area. Here's a study I did some years back.

AC-DC Power Supplies-- Using Wall-warts

FYI, Jon: All of your equations say:

 

I suspect that it is just a normal switching supply that can produce 2.2A at 16V. Unlike others though, they chose to characterize what happens at higher current.

Bob

 

FYI, Jon: All of your equations say:

View attachment 264472

It's an 11+ year old article and the equations were on-line Latex. If I get a chance, I'll fix them.

 

16-10V is puzzling, unless it has some characteristics of a battery charger with constant current/constant voltage modes. That could have some advantages over charging batteries from a fixed input voltage.

 

Can you test it with a varying load?