crappy little laptop Powersupply... 86%+ eff.?

[MrWizard6600]

according to energy star:
http://www.energystar.gov/ia/partne...International_Efficiency_Marking_Protocol.pdf

your (and my) crappy little LiteOn supplied-by-OEM power supply for your laptop is 86% efficient and PFC > 0.9, if its got a "efficiency level: V" rating on it...

really? I was thinking about getting some high grade cable and modding my PSU so that it plugs into my laptop to A) save a wall outlet and B) boost the efficiency of charging my laptop. But if this little 90W thing is 86%+ efficient with PFC > 0.9, why bother? Also its 19W which means I'd have to do something trickey to get my plan to work.

 

[Zero82z]

Considering how much experience Lite-On has with designing and manufacturing laptop PSUs, I wouldn't go and call them "crappy".

 

[RamonGTP]

The circuitry in a desktop power supply is far more complex. You've got 3.3v 5v 12v 5vsb and -12v rails vs a single voltage output typically ranging between 15-24volts depending on the manufacturer and model. All this adds overhead and decreases efficiency

 

[Zero82z]

The circuitry in a desktop power supply is far more complex. You've got 3.3v 5v 12v 5vsb and -12v rails vs a single voltage output typically ranging between 15-24volts depending on the manufacturer and model. All this adds overhead and decreases efficiency

The circuitry in a desktop power supply is not much more complex at all. All newer PSU designs use a single +12V source that is fed into DC-DC VRMs to generate the minor rails. A laptop PSU is just one of those, minus the VRMs (which are built into the laptop's motherboard instead). The principles behind both are the same.

Also, Lite-On has a lot of experience designing very high-quality server PSUs.

 

[RamonGTP]

ok, then it's just a little more complex since the laptop PSU doens't have the VRM's

 

[keenan]

The circuitry in a desktop power supply is not much more complex at all. All newer PSU designs use a single +12V source that is fed into DC-DC VRMs to generate the minor rails. A laptop PSU is just one of those, minus the VRMs (which are built into the laptop's motherboard instead). The principles behind both are the same.

Yes, except in the laptop the efficiency of the DC-DC regulators isn't part of the power supply's efficiency rating. And regardless of design, it's still a much simpler unit.

 

[MrWizard6600]

Yes, except in the laptop the efficiency of the DC-DC regulators isn't part of the power supply's efficiency rating. And regardless of design, it's still a much simpler unit.

Yes they are, they have to be, those guys are the single biggest sources of inefficiency in the whole unit. Its tough to get a transformer and bridge rectifier thats below 95% efficiency... But then yeah I see what you're saying; this thing outputs 19V, which is presumably used to charge the 12V battery, which also means this laptop must have its own internal DC-DC circutry to bring that 19V in down to 12V/5V for the rest of the PC, but in terms of line noise I suspect the 19V is as clean (noise-wise) as the rail gets --which explains the attinuation magnet thing you'll find on your laptops PSU cord between the unit and the laptop itself.

I assumed they were "crappy little things" because they're small... and they ship with the PC. I've got some respect for the PSU's that the OEMS include in their PCs, they're always worth they're salt (read: if it says it'l do 250W it'l do 250W) but never come with much of it, nor do they ever push the 88+ efficiencies we see on the expensive after market stuff. I figured it would be the same story in laptop space: sufficient although not necessiarly brilliant units.

Anyways, I was hoping I could make a project out of it but I can't since its 19V and I dont perticularly feel like ripping apart this thing to put in my own circutry, and any efficiency "gain" by running this laptop off my Neo HE would be nullified by the fact that I'd be doing my own DC-DC conversion to get it up to 19V.

 

[keenan]

But then yeah I see what you're saying; this thing outputs 19V, which is presumably used to charge the 12V battery, which also means this laptop must have its own internal DC-DC circutry to bring that 19V in down to 12V/5V for the rest of the PC, but in terms of line noise I suspect the 19V is as clean (noise-wise) as the rail gets --which explains the attinuation magnet thing you'll find on your laptops PSU cord between the unit and the laptop itself.

The quoted efficiency is just for the power brick, which turns AC into 19VDC or whatever. All the inefficiencies that are inside the laptop are factored out of the number, while the PC supply includes the entire power supply, not just the first stage. If your low current single voltage AC-DC SMPS isn't more than 80% efficient, you're doing something horribly wrong.

Effeciency is also pretty important in these little bricks because the cooling is very poor (they're made out of an excellent thermal insulator and typically have no air gaps at all), and they're often asked to put out 50+W. At 80% effiiciency, that means ~12W dissipation at full load, which is probably not acceptable for this kind of construction and would need better cooling.

 

[MrWizard6600]

The quoted efficiency is just for the power brick, which turns AC into 19VDC or whatever. All the inefficiencies that are inside the laptop are factored out of the number, while the PC supply includes the entire power supply, not just the first stage. If your low current single voltage AC-DC SMPS isn't more than 80% efficient, you're doing something horribly wrong.

Effeciency is also pretty important in these little bricks because the cooling is very poor (they're made out of an excellent thermal insulator and typically have no air gaps at all), and they're often asked to put out 50+W. At 80% effiiciency, that means ~12W dissipation at full load, which is probably not acceptable for this kind of construction and would need better cooling.

more than that, this unit claims to be able to push 4.74A at 19V, which is 90W. And yeah, all plastics are great insulators, but 15W isn't difficult to disperse in delta T under 20, those "little" power bricks have enough surface area to get away with it, granted they've got some thermal piping internally.

If I can get the energy together maybe I'll pop it under the scope.