Ok, I got a Dell laptop at Christmas time (Christmas 2006.)
It has a cord that plugs into the wall socket. The cord runs from
the wall socket to the back of the PC (of course.) About half way on
the cord is some type of plastic box/power pack or something.
Well, this thing gets very very hot. I was just transferring about three
gigs of video from the laptop to another compute wirelessly. The battery
was low so it was also recharging. After I was done and shut the
laptop down and I unplugged it and felt the plastic box - DANG! IT WAS
HOT!!!
Do all laptop power cords get scorching hot?
Could I have a defective power cord or what? I bought this computer in
December 2006. It's not the cord that gets hot. It's the box that the cord
runs thru. Scorching hot!
> Ok, I got a Dell laptop at Christmas time (Christmas 2006.)
>
> It has a cord that plugs into the wall socket. The cord runs from
> the wall socket to the back of the PC (of course.) About half way on
> the cord is some type of plastic box/power pack or something.
> Well, this thing gets very very hot. I was just transferring about three
> gigs of video from the laptop to another compute wirelessly. The battery
> was low so it was also recharging. After I was done and shut the
> laptop down and I unplugged it and felt the plastic box - DANG! IT WAS
> HOT!!!
>
> Do all laptop power cords get scorching hot?
> Could I have a defective power cord or what? I bought this computer in
> December 2006. It's not the cord that gets hot. It's the box that the cord
> runs thru. Scorching hot!
>
> Is this all normal?
>
>
Define "scorching hot". Different people have different tolerances to
things like heat. Yes, the power boxes can get warm-to-hot. That is
why one puts them places where there is good ventilation. Things should
be OK if the plastic isn't melting or decomposing and there isn't the
acrid smell of burning carbon.
On Jun 15, 6:24 pm, "Von Fourche" <Khonak...@hotmail.com> wrote:
> Ok, I got a Dell laptop at Christmas time (Christmas 2006.)
>
> It has a cord that plugs into the wall socket. The cord runs from
> the wall socket to the back of the PC (of course.) About half way on
> the cord is some type of plastic box/power pack or something.
> Well, this thing gets very very hot. I was just transferring about three
> gigs of video from the laptop to another compute wirelessly. The battery
> was low so it was also recharging. After I was done and shut the
> laptop down and I unplugged it and felt the plastic box - DANG! IT WAS
> HOT!!!
>
> Do all laptop power cords get scorching hot?
Lots do. The more current it must deliver the hotter they get. They
can get *really* hot, for example, if you use a 3.5amp power supply to
power a unit that specifies 4amps. (yes, you can often get away with
that, it's not recommended, though!)
> Could I have a defective power cord or what? I bought this computer in
> December 2006. It's not the cord that gets hot. It's the box that the cord
> runs thru. Scorching hot!
>
> Is this all normal?
The box can get hot. I'd be worried if it were the cord itself.
I don't know how they're made, but if they use the cheapest method of
voltage regulation, the heat produced is proportional to the current
drawn, the energy of excess voltage just being dumped into heat at the
same current as the regulated output device is drawing.
So the heat is a feature, not a bug. The design tradeoff is just the
size of the heat sink.
First, your terminology is all messed up, and it matters. The cord
didn't get hot, the AC adapter did (the plastic rectangle in the middle
of the cord); the cord doesn't "run through it", the cord coming out one
side is not the same cord that went in the other side. Also, it's
slightly confusing in this case to refer to the computer as a "laptop"
in one place and as a "PC in another place.
AC adapters normally get warm. Some get warmer than others. Some get
HOT. It MAY be either defective or normal for that model ... hard to
say, but I've had some that go hot enough that I found it objectionable.
Von Fourche wrote:
> Ok, I got a Dell laptop at Christmas time (Christmas 2006.)
>
> It has a cord that plugs into the wall socket. The cord runs from
> the wall socket to the back of the PC (of course.) About half way on
> the cord is some type of plastic box/power pack or something.
> Well, this thing gets very very hot. I was just transferring about three
> gigs of video from the laptop to another compute wirelessly. The battery
> was low so it was also recharging. After I was done and shut the
> laptop down and I unplugged it and felt the plastic box - DANG! IT WAS
> HOT!!!
>
> Do all laptop power cords get scorching hot?
> Could I have a defective power cord or what? I bought this computer in
> December 2006. It's not the cord that gets hot. It's the box that the cord
> runs thru. Scorching hot!
>
> Is this all normal?
>
>
ALL laptop power supplies are switching power supplies. What you
describe below ("the heat produced is proportional to the current
drawn") is a linear power supply, and this description does not apply to
laptop power supplies (or any other switching power supply). However,
it's also not exactly correct for linear supplies, in that a linear
supply my dissipate the LEAST amount of heat while deliverying the most
power (in the extreme case, the load needs the entire source
voltage/current and the resistance of the linear supply goes to nearly
zero, consequently it's dissipating very little power). However, a
switching power supply doesn't work this way at all, not even remotely.
Ron Hardin wrote:
> I don't know how they're made, but if they use the cheapest method of
> voltage regulation, the heat produced is proportional to the current
> drawn, the energy of excess voltage just being dumped into heat at the
> same current as the regulated output device is drawing.
>
> So the heat is a feature, not a bug. The design tradeoff is just the
> size of the heat sink.
>
Barry Watzman wrote:
>
> ALL laptop power supplies are switching power supplies. What you
> describe below ("the heat produced is proportional to the current
> drawn") is a linear power supply, and this description does not apply to
> laptop power supplies (or any other switching power supply). However,
> it's also not exactly correct for linear supplies, in that a linear
> supply my dissipate the LEAST amount of heat while deliverying the most
> power (in the extreme case, the load needs the entire source
> voltage/current and the resistance of the linear supply goes to nearly
> zero, consequently it's dissipating very little power). However, a
> switching power supply doesn't work this way at all, not even remotely.
>
> Ron Hardin wrote:
> > I don't know how they're made, but if they use the cheapest method of
> > voltage regulation, the heat produced is proportional to the current
> > drawn, the energy of excess voltage just being dumped into heat at the
> > same current as the regulated output device is drawing.
> >
> > So the heat is a feature, not a bug. The design tradeoff is just the
> > size of the heat sink.
> >
Back when I built power supplies, you put in a transformer that produced the
voltages you needed, and there was no heat to speak of generated. I'd tend to
call those linear supplies. If not, what are they called?
Anyway if it's getting very hot under load, I bet it's not a switching supply.
The current drawn is being dropped through some resistance, presumably to get the
right voltage, and there's your heat. A switching supply just increases or decreases
the portion of the cycle used, to keep the sought-after voltage.
That's a linear supply. And it does generate heat. First, the
transformer creates some heat (how much varies widely) as the windings
have resistance, and some current is induced and flows in the iron
laminated core of the transformer. Second, as you noted, the regulator
of a linear supply regulates by "wasting" the difference between what
the transformer puts out and what the load uses as heat (the transformer
is ALWAYS designed to put out at least 2.5 to 5 volts more than the load
uses, and the [linear] regulator works by "wasting" the difference as heat).
A switching power supply works totally differently; the incoming AC is
full wave rectified to DC (150 to 400 volts if it's a line operated
supply), then the DC is switched on and off at a very high frequency (20
to 100 KHz) as a "square wave" passed to the primary of a pulse
transformer. The output of the pulse transformer is full wave rectified
and capacitor filtered (the frequency is so high that tiny capacitors
produce perfect filtering, plus you are full wave rectifying a square
wave ... it's virtually ripple free to begin with). Also, because of
the frequency, the pulse transformer can be small, efficient, low loss.
Regulation is accomplished by comparing the actual output to the desired
output and adjusting the duty cycle of the square wave switching on the
primary side of the pulse transformer. Since the switching element is
either always "on" (near zero voltage across it) or "off" (near zero
current flowing through it), very little power is dissipated in a
switching power supply.
While you may think otherwise, switching power supplies are virtually
always FAR more efficient than linear power supplies. Linear power
supplies require an absolute minimum of 3 volts to be dropped across the
regulator at all times, and in many cases it's two to three times that
much. Taking a 5-volt supply as an example, that means that the
absolute best case efficiency is 5/8 (62.5%), but in fact it's often
less than 50% (and this only takes into account the loss in the
regulator and doesn't include the loss in the transformer, which may be
that much all over again). Switching supplies, on the other hand, have
efficiencies as high as over 90%, and never lower than the 60%'s (and
that's total supply efficiency, not just regulator efficiency).
The efficiency, size, weight and cost ALL favor switching power supplies
by a huge margin once you get above about 10-20 watts or so of total
power required. That's why there hasn't been a laptop made .... EVER
(even 2 decades ago) that used a linear supply. Or, for that matter, a
desktop either since back in the S-100 days.
Ron Hardin wrote:
>
> Back when I built power supplies, you put in a transformer that produced the
> voltages you needed, and there was no heat to speak of generated. I'd tend to
> call those linear supplies. If not, what are they called?
>
> Anyway if it's getting very hot under load, I bet it's not a switching supply.
> The current drawn is being dropped through some resistance, presumably to get the
> right voltage, and there's your heat. A switching supply just increases or decreases
> the portion of the cycle used, to keep the sought-after voltage.
>
Barry Watzman wrote:
> While you may think otherwise, switching power supplies are virtually
> always FAR more efficient than linear power supplies. Linear power
> supplies require an absolute minimum of 3 volts to be dropped across the
> regulator at all times, and in many cases it's two to three times that
> much. Taking a 5-volt supply as an example, that means that the
> absolute best case efficiency is 5/8 (62.5%), but in fact it's often
> less than 50% (and this only takes into account the loss in the
> regulator and doesn't include the loss in the transformer, which may be
> that much all over again). Switching supplies, on the other hand, have
> efficiencies as high as over 90%, and never lower than the 60%'s (and
> that's total supply efficiency, not just regulator efficiency).
Yes, well my experience was usually with 1000 volt supplies, where I
picked up the little-heat observation. Perhaps not true at 5v.
--
Ron Hardin rhhardin@mindspring.com
On Sat, 16 Jun 2007 01:24:05 GMT, "Von Fourche"
<Khonakong@hotmail.com> wrote:
>
>
> Ok, I got a Dell laptop at Christmas time (Christmas 2006.)
>
> It has a cord that plugs into the wall socket. The cord runs from
>the wall socket to the back of the PC (of course.) About half way on
>the cord is some type of plastic box/power pack or something.
>Well, this thing gets very very hot. I was just transferring about three
>gigs of video from the laptop to another compute wirelessly. The battery
>was low so it was also recharging. After I was done and shut the
>laptop down and I unplugged it and felt the plastic box - DANG! IT WAS
>HOT!!!
>
> Do all laptop power cords get scorching hot?
>Could I have a defective power cord or what? I bought this computer in
>December 2006. It's not the cord that gets hot. It's the box that the cord
>runs thru. Scorching hot!
>
> Is this all normal?
My 2 cents. I have had maybe 10 Dell laptops, and have never noticed
the adapter getting scorching hot. At most, I'd call it "warm". Of
course, I never really went out of my way to check them for
temperature. I tried the one connected to my 1405 just now and it's
"warm".
Do you have a digital thermometer or some way to take a temperature
reading?
Dell replaces power cords under warranty. They will send one out to
you quickly and you can send yours in. If I were you I'd do that. If
you call and get someone in India who you aren't comfortable with, I
recommend cutting your losses right away, hanging up, and calling back
until you get someone you like.
I don't talk to tech support people when I can only half understand
their English speaking skills.
At least with power cords diagnosing the problem doesn't require
rebooting your computer or reinstalling the OS :-)
Very Hot Power Cord to Laptop 
Linear Mode
