Laptop PSU question

Okay... so...

I am not entirely sure of what the laptop power adapters are generally capable of, but I've seen a few reviews of certain laptops where the supplied adapter is say maybe a 120w unit but the system is drawing 150w under maximum load.

Now, I know what my old R2's PSU could do. That 240w unit would handle loads of around 270w without a problem, but once they pushed beyond that, it would throttle the game performance heavily...

So, what does that mean technically? How far can most power adapters go beyond their ratings?

 

You're not factoring in PSU efficiency.

If you're drawing 150W at the wall and the PSU is 80% efficient then the machine is only drawing 120W. If you're drawing 270W at the wall only 216W is actually being used to power the laptop, the rest is given off as heat. Which is why more efficient power supplies also run cooler.

 

Octi, any idea how well laptop bricks stack up with desktop PSUs? Desktops have a whole range of PSUs and the high end ones market themselves with gold silver and bronze ratings for 80+ efficiency. Laptop bricks on the other hand never need to market themselves, and vendors have even gone out of their way to prevent 3rd party bricks from being used, thus no reason for being efficient.

 

No idea...

 

Comparing Apples to Oranges....this comparison doesn't help...to answer any pertinent questions here.

 

Feel free to keep reading over octi's well versed explanation on WHY efficiency numbers are needed, and then you might.. just might grasp why I asked if bricks were on average, more or less efficient then desktop PSU units.

 

If you look on the power brick there is an efficiency rating which is usually "V" for external ones which means 87-90% efficiency. See this rating table here: http://www.energystar.gov/ia/partne...International_Efficiency_Marking_Protocol.pdf

Which from this document it shows here:


You can see efficiency rating on the PSU here:


And with the "V" rated devices over 100W power draw devices are required to have at least a 90% efficiency at 100% load.

You basically have to make sure you match up the voltage and typically OEM power supplies are typically much better quality than any third party ones and I would recommend buying an OEM one (i.e. HP, Sony, Dell, etc) if you value your laptop components. If it's an old machine and don't care much then by all means save a few bucks. But power quality is important with these electrically sensitive devices.

The listed rating is the *minimum* rating for amperage so many quality ones can draw over that by some percentage, but over time on a regular basis can kill the PSU prematurely.

It shouldn't damage the motherboard, but likely reduce the life of your power supply.

 

This I agree with 100%. I only recommend to anyone to use OEM power supplies, no matter how expensive they are. Alot of 3rd party ones interfere with your ability to charge your battery properly as many do not include the pin (to tell the motherboard it is a legitimate charger). Most genuine chargers have an EEEPROM chip to tell the BIOS a genuine charger is plugged in. Some older Dells, you had to plug in a Dell charger or it wouldn't even power up past the POST screen. I only recommend 3rd party ones if you are in a pinch (lost your charger, dog ate it, need it to extract 1 document) but I do not recommend them for excessive usage. I've also seen a lady had a DV9000 HP and she used a 3rd party 90W Targus, and the PSU shorted, causing it to melt and it melted the DC input jack, the bottom casing, the plastic bezel and the palmrest.

 

Nice post but try not to confuse power factor, which is a phase relationship between voltage and current on the AC side, with overall efficiency.

 

True. PF is a bit misleading. In any case it has to be at least 87% efficient based on that chart to receive a "V" rating.

 

How about keeping the discussion to laptop power bricks. Desktop PS has so many and different ratings that laptop bricks will never be able to compare to Desktop variations. As to laptop PS one should not mix and match but keep to close OEM specs which is why they have those rating on the manufacture site and listed on the laptop that the PS has to match the rating for efficient operations and longevity of battery life and hardware. Enlightenment only occurs should one talk about relevant information not hypothetical comparison that can't be compared equally.