
Macbook charger teardown: Complexity inside Apple's power adapter (2015) - blowski
http://www.righto.com/2015/11/macbook-charger-teardown-surprising.html?m=1
======
bArray
The price list at the bottom [1] isn't fair, a company like Apple usually pays
more for it's components for "higher" quality (usually a probabilistic
reduction in failure rate). Things are so bad in the industry that it's not
possible to get some of the higher rated components because Apple has bought
them all.

[1] List (from reference 19 on the site):

    
    
        Component                                          Cost
        MSP430F2003 processor                              $0.45
        MC33368D PFC chip                                  $0.50
        L6599 controller chip                              $1.62
        LT1460 3.3V reference                              $1.46
        TSM103/A reference                                 $0.16
        2x P11NM60AFP 11A 600V MOSFET                      $2.00
        3x Vishay optocoupler                              $0.48
        2x 630V 0.47uF film capacitor                      $0.88
        4x 25V 680uF electrolytic capacitor                $0.12
        420V 82uF electrolytic capacitor                   $0.93
        polypropylene X2 capacitor                         $0.17
        3x toroidal inductor                               $0.75
        4A 600V diode bridge                               $0.40
        2x dual common-cathode schottky rectifier 60V, 15A $0.80
        20NC603 power MOSFET                               $1.57
        transformer                                        $1.50?
        PFC inductor                                       $1.50?
    

_On a side note..._ I've seen the case where Apple's standards for compliance
are set using the components they buy the highest grade of - making it even
more difficult for external companies to implement compliance. It was bad
enough that the standard chip, recommended circuit and recommended testing
tools failed to meet their requirements.

 __NOTE: __Apologies to any users where the screen is stretched.

~~~
blackguardx
The only parts on that list that would have different grades are the
capacitors. It isn't a measure of quality, but the temperature and stability
specs of the dielectrics.

EDIT: Source: I'm an electrical engineer and design electronics for a living
and have even worked with ex-Apple engineers.

~~~
bArray
EDIT: There certainly seems to be different quality levels for this particular
processor anyway [1], which I'm sure they'll want a premium for higher
quality. Feel free to correct me though.

[1]
[http://www.ti.com/product/MSP430F2013/quality](http://www.ti.com/product/MSP430F2013/quality)

~~~
mng2
Those are various combinations of IC package, temperature grade, and bulk
packaging. They are demonstrating that all the different types they sell have
gone through environmental testing. There is no such thing as 'higher
quality', generally, but a part with extended temperature range or a faster
speed grade does cost more.

~~~
bArray
I think perhaps my wording was misplaced, but a part that has been shown to
reach high temperatures might be more preferable in a charging application -
even if they blow up anyway.

------
rectang
An amazing amount of thought went into the design of these power bricks.
Now... What does that say about their choice of fray-prone insulation?

Obviously they are aware of those of us who have to buy new power bricks
regularly because the insulation has shredded. (I have to buy a new one about
once a year.) In some proportion, we are either 1. a profit opportunity or 2.
collateral damage of an engineering decision to favor that thin insulation for
flexibility or whatever.

I'd love to know their analysis!

~~~
GuiA
My pattern is that I buy a MacBook, use it for a few years, resell it and get
a new one.

I'm at my 5th or 6th MacBook in over 10 years, and I've always sold the
laptops back with their original charger.

I have a 2011 MacBook Air that I take everywhere with me - the battery is at
over a few thousand cycles (and lasts about 40 minutes) last time I checked.
The charger for this one is dirty and chipped, but not frayed.

I've seen frayed cables, so I know it's a real problem, but given my
experience I can't help but wonder... what are people doing with their
chargers?

~~~
Spooky23
They completely unwrap and re-wrap the cord.

The design is defective, and cannot handle the typical stresses that it is
subjected to.

~~~
cookiecaper
Yes. "Blame the user" is not an acceptable approach to resolving a problem
with even a slight incidence rate. "We don't see that behavior often enough to
commit resources to addressing it" is valid, but "they're touching it wrong"
isn't when you're making a mass-produced consumer-grade product, especially a
product that's meant to be carried to and fro (Apple had to learn this with
the iPhone 4 too).

Some people may take pride in carrying their chargers around on special hand
pillows to ensure that they are kept pristine over the years, but I personally
want my products to work without demanding special accommodation for
themselves. I went through 3 chargers in the 4 years I used a MacBook Pro. I
didn't mistreat the stuff, I just didn't pamper it.

The answer in this case is pretty obvious, though; Apple knows that an $85
power cable isn't going to cost them any meaningful quantity of customers, and
actually the breakage tends to net them $85 extra per year, so they kind of
like it. There is no incentive for them to un-plan the planned obsolescence of
the charger.

~~~
Spooky23
The ridiculous thing about it is the power supply itself is almost an
engineering feat unto itself.

In my personal experience, I've owned hundreds or thousands of electrical
devices, but to date I've only gotten an electrical shock from my old MacBook
Pro's power brick, which was an amazing device in every other way.

It speaks to the hubris of their design org.

------
planteen
> A powerful microprocessor in your charger? > One unexpected component is a
> tiny circuit board with a microcontroller, which can be seen above. This
> 16-bit processor constantly monitors the charger's voltage and current. It
> enables the output when the charger is connected to a Macbook, disables the
> output when the charger is disconnected, and shuts the charger off if there
> is a problem. This processor is a Texas Instruments MSP430 microcontroller,
> roughly as powerful as the processor inside the original Macintosh.

I'm not surprised at all. Microcontrollers are ubiquitous. There's little
reason to use something like a 555 timer anymore. I wouldn't have been
surprised if this had been a 32-bit ARM MCU (or a 8-bit PIC).

~~~
kabdib
On one project I was on, we used a 16-bit MCU for a power controller. Cost
less than twenty cents, and we got a lot of functionality out of it (you can
cram a bunch of complex logic into 2K of code).

Near the end of that project, the hardware engineers came to us and
apologized; they had managed to source a part for the same price with twice
the code space. Could have used that, would have saved quite a bit of space
optimization effort.

~~~
planteen
Should have had your supply chain people push the vendor/distributor on price
of the half code space part to make all of that cramming NRE worth it. ;-)

------
pivo
The linked video of how bridge rectifier works is enlightening, funny and
terrifying. Makes me glad I'm a software developer and not an electrical
engineer so I'm in no danger of killing myself if I miscalculate.

[https://www.youtube.com/watch?v=sI5Ftm1-jik&feature=youtu.be](https://www.youtube.com/watch?v=sI5Ftm1-jik&feature=youtu.be)

~~~
wrigby
His videos are extremely entertaining, but his disregard for safety
exaggerates the danger a little bit. My understanding is that most bridge
rectifiers are put in a circuit after a step-down transformer, so they're
operating on a much lower AC input voltage.

Also, don't wrap the safety ground pin on test equipment with kapton tape.
Just don't.

~~~
hatsunearu
They can be, and they are in certain linear PSUs. Linear PSUs generally make
ripply DC with linear power transformer -> rectifier and then use active
linear analog circuits to get clean DC power. Has very low efficiency but
exceedingly low noise.

For most consumer things, you use a classic switch mode power supply design.
You bridge rectify mains directly, and you switch that really fast to get the
DC you need, and you filter it a lot.

------
awesomerobot
Amazing that so much thought goes inside the adapter, but they still manage to
completely skip any worthwhile stress relief on the cable ends. One of the
reasons I know how to solder wire is because I got tired of buying a new
adapter every year.

------
nilved
Previous discussion:
[https://news.ycombinator.com/item?id=10628212](https://news.ycombinator.com/item?id=10628212)

------
dewiz
> One problem with simple chargers is they only draw power during a small part
> of the AC cycle.[5] If too many devices do this, it causes problems for the
> power company.

What kind of problem?

~~~
soneil
I'm mostly familiar with this from UPSes, but I assume it's basically the same
problem on a different scale.

Lets say you have a device that requires 110 Watts - 1 Amp at 110 Volts. And
you have a UPS that is rated to provide exactly the same.

In an ideal world (spherical cows, etc), and a device with a power factor of 1
(e.g., perfect), this works.

But if you have "non-sinusoidal current" (as his footnotes word it), your
device isn't actually pulling 1 Amp. If you graph the voltage and current draw
out, you should see the current draw forms a wave that matches the voltage (in
shape, not value). If it doesn't, then at some parts of the wave, you're
drawing more current than you claim - and at others, you're drawing less. So
you're still drawing 1 Amp on average, but at any given instant, you're
probably not.

So back to our spherical cow UPS. What looks like a perfect match on paper,
goes wrong - 60 times a second, you're drawing more than those 110 Watts and
causing an overload condition. And it's an issue that gets horrible when you
scale it, because every device is receiving exactly the same wave form - so
every device is using more than you think at precisely the same time. Like the
trope of people jumping on a bridge at the same time, each consumer causes the
same condition in perfect unison with each other.

~~~
sitharus
It's not really that your device draws more than the claimed wattage, it's how
the power arrives.

Resistance is proportional to current (I = V/R) so drawing 100W at 240v will
result in a lower resistance than 100W at 110v. In an ideal world this doesn't
matter but the real world had wires with resistance etc.

This means if you draw your peak current at peak voltage you're using as
little current as possible, but if the peak current is offset you'll be
drawing more amps than you would if you were in phase.

This causes parasitic losses in the distribution network and makes utilities
grumpy, amongst other things.

~~~
soneil
I think what you're describing is phase shift (typically seen with inductive
loads), where the current sine is the right form, but lags behind the voltage
sine.

The (fifth) footnote in the article has "The difficulty comes from the
nonlinear diode bridge, which charges the input capacitor only at peaks of the
AC signal." And "If you're familiar with power factors due to phase shift,
this is totally different. The problem is the non-sinusoidal current, not a
phase shift."

So the demand looks like inrush current - but inrush at every single cycle.
This produces a non-constant load, where the current draw instead graphs more
like an ECG and less like a sine wave. If you overlay this ECG-style graph
over a perfect sine, you see that to average the same draw, the spike has to
peak much higher than the sine - because it's drawing nothing for the rest of
the cycle.

The net result is basically the same (which is why both problems come under
'power factor') - you're drawing current in a very inefficient manner - but
that's why I'm describing 'drawing more than the claimed wattage', because at
the peak of each cycle, you do.

------
otterpro
I've owned couple of Macbook and Macbook pros since 2009 and never had any
issue with the fraying, but I've seen one case of fraying from a friend's
Macbook Pro just few months ago. I didn't think she'd abused her adapter in
anyway. On a side note, I had every single original iPhone charging cable fray
after less than couple of years of use (including 30pin and lightning cables
from iPhone 3, 3G, iPhone 4, and my current iPhone 6). It is very annoying.

A good way to fix is to use Suguru ([https://sugru.com/how-to/fix-a-broken-
cable](https://sugru.com/how-to/fix-a-broken-cable)), which seems to be made
to fix things like this, and stronger than heat-shrink tubing.

------
jjellyy
Title would be less ambiguous if it said Macbook Pro charger, since they have
laptop called Macbook and it uses a different charger.

------
sosuke
Are other laptop chargers similarly complex? Dell, HP, Microsoft etc

~~~
revelation
Once your power supply is capable of delivering >=75W, european norm 61000-3-2
requires you to implement power factor correction (PFC), which makes
complexity balloon.

All name-brand laptop chargers will usually have it.

~~~
vonmoltke
> requires you to implement power factor correction (PFC), which makes
> complexity balloon

Depends on how much is required and what your size limits are. Apple used
active PFC here to minimize the size of the brick. An ATX desktop or server
supply might be able to get away with passive PFC, which is not very
complicated but tends to be bulky.

~~~
TD-Linux
All desktop and server power supplies use active PFC at this point, because
the cost of the much bulkier passive components is now higher than the cost of
the active ones.

EDIT: apparently not quite, I went on Newegg and the non-80plus power supplies
still have passive PFC.

~~~
vonmoltke
Sure, simpler active PFC components are pretty cheap now. There isn't much to
a valley-fill circuit, though. That should get you below the legal limit on
harmonic distortion in most cases. I know it is still the standard PFC in
lower-power fluorescent light ballasts.

------
acrefoot
> AC power enters the charger and is converted to DC. The PFC circuit (Power
> Factor Correction) improves efficiency by ensuring the load on the AC line
> is steady. The primary chops up the high-voltage DC from the PFC circuit and
> feeds it into the transformer. Finally, the secondary receives low-voltage
> power from the transformer and outputs smooth DC to the laptop.

I had a hard time reading this. It sounds like the transformer is getting DC
power? Do transformers even work with DC power?

~~~
paulmlewis
> The primary chops up the high-voltage DC from the PFC circuit and feeds it
> into the transformer.

It chops it up to AC for the transformer.

~~~
yayitscaroline
Ah, this makes sense. Do you know how the "chopping it up into AC"works?

~~~
qntty
This transformer would be a flyback transformer therefore doesn't need to be
driven by anything so hard-to-generate as a sine wave. It can be driven by a
"switch" (MOSFET) at it's primary which is connected to DC.

[https://en.wikipedia.org/wiki/Flyback_transformer#Operation_...](https://en.wikipedia.org/wiki/Flyback_transformer#Operation_and_usage)

~~~
cnvogel
All switching power supplies (hence the name) are driven by either full-on or
full-off ("switching") transistors. A "flyback" topology is only one of many
possible ways to build a switching power supply, but as it's the simplest,
it's the most common in low power supplies.

See the Switch−Mode Power Supply Reference Manual from ON Semiconductor for
info on all the other possible ways to build a switching power supply.

------
jheriko
now if they can just make it earthed by not lacquering the connector designed
for that purpose to make it shiny... maybe macbooks everywhere will stop
giving people shocks (!)

~~~
TD-Linux
Double-insulated appliances don't need to be earthed.

~~~
jheriko
a long time ago i used to work in a factory testing fairly low build quality
computers, if i did their qa process on macbooks they would fail this 15 year
old test because of this.

i know that us standards are often different to uk, europe and others in this
regard. maybe it is safe and our standards are paranoid, but i don't enjoy
electric shocks, no matter how small they are... and from talking to others,
this is not an uncommon experience - at least on 2013 and newer macbooks using
the UK version of the plug

------
j_koreth
I wonder if its possible to run linux off a power adapter...

~~~
kirrent
No implementation for the MSP430 as it stands, but I can't see why not.

[https://en.wikipedia.org/wiki/%CE%9CClinux](https://en.wikipedia.org/wiki/%CE%9CClinux)

~~~
monocasa
MSP430's only have 64K of address space, which isn't enough to run even
uCLinux.

~~~
c-smile
But it is quite a lot for CP/M -
[https://en.wikipedia.org/wiki/CP/M](https://en.wikipedia.org/wiki/CP/M)

~~~
monocasa
Eh, it's low even for CP/M. MSP430s have 64K of address space, not RAM. Even
the smallest CP/M machines had that. A lot even had simplistic paging hardware
to exceed that.

------
fpoling
I guess USB-C charger for newer MacBooks is even more complex. Still I wish
Apple paid more attention to designing cables and connectors. In my case the
cable broke within weeks and after a year the USB-C socket on the power supply
became loose randomly disconnecting the cable :(

------
yayitscaroline
Amazing that today's laptop chargers have as much computational power as the
original mac

------
tanqueray
Mine have always lasted for Macbooks, as I never take them out with me.
Phones/iPads start fraying after a year or so if you chuck them in bags etc.

------
tgfgvc
"plugged in, not charging" problems are very common with Macbooks. Maybe a
simple charger would work better.

------
zakomon
Can anyone give me a quick summary?

------
codecamper
oh yes... a classic read. a perennial favorite!

------
Someone1234
Maybe add 2015 to the title. This same blog post has been linked a good amount
before.

