Efficiency of your typical laptop AC adapter ?

How much is lost in a typical AC adapter ?

 

Desktop PSUs are ~75% efficient, so I would guess the same with laptop adapters.

 

I suppose if it`s red hot and it`s the correct psu, then it`s wasting energy as heat so i suppose less efficient.

 

Wish laptop PSUs would follow suit with desktop PSUs and get into the 80Plus program. Some of the newer desktop PSUs have efficiency of 90+%.

 

What energy are you talking about OP...heat energy? Since an adapter isn't the useful product, I think you should focus on the energy use of the device.

Suffice it to say, laptops (desktop replacement) are more than 50% more efficient than your desktop.

 

When the adapter converts the electricity for use in your computer (AC to DC), it loses efficiency to the conversion process, which is why the adapter feels hot (since energy is never destroyed or lost, it is converted to heat energy form). There's a campaign in the US trying to get people to unplug their phone chargers when not in use because even when not charging, they're wasting electricity.

 

In the case, of the laptop you're already saving money just by owning one.

 

Yeah, but that's not the point. Just because the Toyota Camry (sedan) uses less gas per mile than the Chevy Silverado (truck), doesn't mean the Toyota team should stop caring about making their vehicle even more efficient.

 

In that case, why drive at all? I got that point. But you're not getting the issue: People are going to use energy no matter what machines they use. The best we can do is limit it's foot print--which is what laptop users already do.

Incidentally, unlike a cellphone charger plug which just charges the phone. Your laptop plug is also needed to power the device. Furthermore, I don't know of anyone that leave their laptop power brick plugged in when it's not powering the laptop. If you do, then I agree with your statement.

 

No, that's not the issue at all. Laptops use less power than desktops - well, duh.

The issue (a minor one) here is that if the PSU is not as efficient as a desktop PSU (which I'm not even sure if that's a true statement. I don't know what the actual efficiency of laptop PSUs are). Then companies should put a little effort into making their PSUs more efficient.

I don't think you understand what efficiency is. Efficiency is not vampirism, as in when the PSU draws power when the laptop is not connected. Efficiency is the inevitable drop of power when AC is converted into DC or vice-versa. For example, if a PSU is 50% efficient, and it draws 20 watts from the socket, 10 of those watts end up powering the system, while the other 10 is lost in the conversion.

 

Typical laptop AC adapters are around 25% eficient strictly from caculation from input vs output power. The actual value though will probably not exceed 50% efficient.

 

Didn't even think of doing that.

For my AC adapter:

Input = 120v @ 2A = 240 W
Output = 19v @ 6.32A = 120 W

 

According to apple the uMacbook Pro power adaptor is 88.4% efficient , it is slightly warm to the touch.

 

Ignore what it says on the PSU label.

In my experience, notebook PSUs have 80% to 90% efficiency. ie 60W being drawn from the mains socket becomes around 50W supplied to the computer. As already noted above, an inefficient PSU becomes hot, because the lost energy becomes heat (and conversely, an efficient PSU stays relatively cool).

John

 

90 % is about the hightest the efficiency can get ?

 

Theoretically the highest efficiency possible is 100%, meaning absolutely no energy is lost as heat; every bit of power drawn is used. However, that's a practical impossibility. Many entry-level electronics courses start off with problems revolving around ideal systems like this. Perhaps with superconducting materials, but that's far from mainstream right now.

 

I can see many notebook PSUs getting high 70s and low 80s, but not much more. Every 1% increase after that gets exponentially more difficult.

 

the theoretical maximum is actually below 100%, as is the practical maximum.

The practical maximum is somewhere about 90% for the more efficient power adapters.

 

How do you figure the theoretical maximum efficiency of an ideal system to be less than 100%? Assuming absolutely no resistance, of course...such a system is not practically feasible, hence the difference between theoretical and practical efficiency.

 

I have a feeling we'll never have 100% efficient systems simply because humans are not perfect and never will be.

After all, even if we had the knowledge, a single atomic-level defect during the manufacturing process would make the system less than 100% efficient.

 

One of the highest in efficiency for a PSU:

http://www.80plus.org/manu/psu/psu_reports/SP633_SEASONIC_SS650KM_COMBO_650W_Report.pdf

 

Yep - this falls within the purview of your conundrums of practical impossibility.

 

Is it correct to assume that the typical laptop adapter is less efficient that one for a desktop ?

 

On average, they aren't that different. Desktops have a bigger range than laptops IMO though, since you can find some really shotty built desktop ones with terrible efficiency, but at the same time there are some excellent models, such as the one I posted above (Seasonic X).