Apple and other USB charger secrets

Everybody seems to be saying that you can’t charge Apple devices with normal USB power supplies. You need a special power supply from Apple or approved by Apple. I saw this kind of discussion at slashdot some time ago.

Usually, device makers need to sign a confidentially agreement with Apple if they want to say their charger ‘works with iPhone / iPod,’ and they’re not allowed to talk about how the insides work. I hate when manufacturers do crap like this to keep peripherals locked into a more profitable licensing agreement. Apples tendency toward total control is one of the things i don’t like about them. And many other manufacturers are just as bad. I wish companies would back off and be more open and/or use standard micro USB chargers.

The mysteries of Apple device charging article includes a 7-minute video we explore the mysteries of Apple device charging. The secret of Apple chargers is simple: just few resistors. If you don’t put these secret resistors on the data lines too, you get the dreaded Charging is not supported with this accessory. Those resistors like a way to signal to the iPhone that it can go ahead and “fast charge” by pulling 1A, or “slow charge” by pulling 0.5A. The iPhone needs to do a power negotiation to determine if the port is capable of providing 1000ma of power, because the upper-limit of a standard USB port is 500 mA. They just didn’t tell anyone about how to do that. I get why the resistors were initially added but I’m not understanding why it needs to be a trade secret.


There is nothing to stop them just drawing the 500mA if the right sort of charger is not detected. Refusing to charge at all unless the licensed parts are present is pure market control, nothing else. Here is the resistor configuration for 500 mA charging:


Resistance is Futile. The The mysteries of Apple device charging article demonstrates how anyone can make their own chargers that work with iPhone 4, 3Gs, etc. The pictures on this blog posting are from that article.

Apple devices are not the only one USB charged devices that can have some problems with USB chargers. So here are some resources on USB charging in general.

USB As A Power Source article gives an introduction USB Power Form.

European Commission has reached a voluntary agreement with some of the biggest names in the electronics industry to introduce a common charger for cell phones that fits all models. Information on this USB charging connector is available at USB Approved Class Specification Documents document directory. Read also Battery Charging v1.1 Spec and Adopters Agreement document.

Dealextreme USB charger discussion posting says that USB standard has 4 lines (+5V, ground and +/- data lines). Most USB chargers let the data lines float. Technically, the USB standard says that a USB charger should set the two data lines to specific voltages (~ 2V) to indicate how much power it can provide (I have not verified that from standards yet). The recent iPhones will not charge if the data lines are set incorrectly (i.e. not according to the USB standard).

USB Charging Guide comment: I believe having the data pins connected to each other is in the latest USB specification for charging. I had to interconnect the D+ and D- pins inside my USB AC charger to get it working with my Zune. Perfectly according specs but frustrating enough.

Wikipedia USB article: The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire from which connected USB devices may draw power. The specification provides for no more than 5.25 V and no less than 4.75 V (5 V±5%) between the positive and negative bus power lines. For USB 2.0 the voltage supplied by low-powered hub ports is 4.4 V to 5.25 V.

A unit load is defined as 100 mA in USB 2.0, and was raised to 150 mA in USB 3.0. A maximum of 5 unit loads (500 mA) can be drawn from a port in USB 2.0, which was raised to 6 (900 mA) in USB 3.0.
All devices default as low-power but the device’s software may request high-power as long as the power is available on the providing bus.

In Battery Charging Specification, new powering modes are added to the USB specification. A host or hub Charging Downstream Port can supply a maximum of 1.5 A when communicating at low-bandwidth or full-bandwidth, a maximum of 900 mA when communicating at high-bandwidth, and as much current as the connector will safely handle when no communication is taking place (USB 2.0 standard-A connectors are rated at 1500 mA by default).

A Dedicated Charging Port can supply a maximum of 1.8 A of current at 5.25 V. A portable device can draw up to 1.8 A from a Dedicated Charging Port. The Dedicated Charging Port shorts the D+ and D- pins with a resistance of at most 200Ω. The short disables data transfer, but allows devices to detect the Dedicated Charging Port and allows very simple, high current chargers to be manufactured. The increased current (faster, 9 W charging) will occur once both the host/hub and devices support the new charging specification.

Without negotiation, the powered USB device is unable to inquire if it is allowed to draw 100 mA, 500 mA, or 1 A. Some non-standard USB devices use the 5 V power supply without participating in a proper USB network which negotiates power draws with the host interface

In most cases, these items contain no digital circuitry, and thus are not Standard compliant USB devices at all. This can theoretically cause problems with some computers; prior to the Battery Charging Specification, the USB specification required that devices connect in a low-power mode (100 mA maximum) and state how much current they need, before switching, with the host’s permission, into high-power mode.

USB Charging Guide tells some more details on mini-USB plug: the mini-USB plug actually has 5 pins in it. This can be important as the extra pin (Pin 4) USB_ID is usually either connected to ground or left floating. Sometimes a pull up resistor needs to be added to from the USB_ID to Pin 1 (VDD) to select “Device Mode” rather than “Host Mode”. This resistor is in the device side plug as the USB_ID pin is not wired through to the PC side connector. The good news is that quite a few USB cables have this. So sometimes you can get round the not charging problem simply by trying out different leads and one may work rather than buying the manufacturers “special” cable. On some Creative players you can also solve this by pulling down both data lines (with 2x15k resistors) at the source to emulate what the host (PC) does when setting line speed. This is not so common.

So the current state of USB charging is a little bit of mess…


  1. Tomi Engdahl says:

    This is the world’s thinnest charger

    Israeli Kado describes well the current mobile phone chargers: no one has ever thought of designing them. According to the company

    The company has introduced the world’s thinnest charger, which is only 5 millimeters thick. Still, it downloads all the USB devices that you want with it.

    Charger plugs fold into the enclosure. Removable, the charging cable inside the device is 85 centimeters long and at its end is a lightning connector suitable for microUSB, USBC or Apple devices. The charging power is 10 watts and supports fast charging.


  2. Tomi Engdahl says:

    How to Power Nearly Anything Off a USB Port

    USB runs at 5v. The max current you can draw is 500ma. Therefore the max load is 5v x 0.5A=2.5. Watts. (W=VxI) If you try and draw more than 500mA, you may overload the port which will cause it to break

    Okay so your going to need to get any USB cable this can be a printer cable or a MP3 player cable

    now you will want to cut it to the length you want it , you only need the Male end so the other bit can be discarded

    Okay you will want to strip the wire to reveal the wire underneath once you have done this there should be 4 wires , you only need the red and black ones as they are the power the green and white are data so they can go :)

    So you will now want to solder the red wire ( positive ) and the Black Wire ( negative ) to the power in to your circuit or appliance

  3. Tomi Engdahl says:

    Ride Bike, Charge Phone

    If you’ve ever used a motor as a generator, then you can see where this is going. That’s the underlying principle behind [Creativity Buzz]’s bike-powered phone charger. As the bike wheel turns, the rim comes in contact with a small wheel attached to the output shaft of a DC motor. Cranking the output shaft of a motor with permanent magnets inside will induce a small voltage, and here it is amplified with a DC-DC boost converter and output to a USB jack.

    Bicycle Mobile Charger

  4. Tomi Engdahl says:

    Weird USB battery charger circuit.

    This is the circuitry inside a cheap USB two cell charger.

  5. Tomi Engdahl says:

    Teardown of an illuminated wire USB charging lead.

    Flowing light USB cable teardown and schematic.

  6. Tomi Engdahl says:

    Samsung USB Charger Failure and Repair

    In this video I’m examining and repairing my faulty USB phone charger (5V 1A switching power supply). It failed after 2 years of seldom use. I’ve drawn a partial schematic in the video. Full reverse engineered schematic of this charger is here:

  7. Tomi Engdahl says:

    USB Adaptive Charger (2.7A per port) with Wattmeter

    A 10.8A, 4 port USB charger with a wattmeter and adaptive intelligent charging.

    We built the Pirl Charger because we were unhappy with the quality of existing chargers. Few consumers know they gradually ruin their expensive devices by using poor quality chargers that deliver high noise, high ripple energy. Every consumer device comes with a charger, and those are usually well-built, but they usually have only one port, and if you lose it, you usually buy an aftermarket charger. However, replacement chargers range widely in quality, and most people don’t know.

  8. Tomi Engdahl says:

    Hacking Qualcomm (Quick Charge) QC 2.0/3.0 with ATtiny85

    Get not only 5 volts but also 9, 12 volts (18 Watts max) out of any QC-compatible charger/power bank for supplying power hungry projects.

    Many USB powered consumer electronic devices comes with Qualcomm QC solution for rapid charging at different voltages rather than usual 5.0 volts. This enables the opportunity to use QC compatible Power Banks for projects require more power or higher voltages like 9/12 volts.

    The purpose of this project is to develop a device that can hack the QC protocol and allow hobbyists, developer, engineers use their power banks for more voltage/power for their next power hungry project.

  9. Tomi Engdahl says:

    The truth inside lightning cable original – XFix

    The truth inside lightning cable original, this is what i found inside a original iphone cable right from apple. I did my best to open it up to show everybody how it looks.

  10. Tomi Engdahl says:

    DC Input, USB Fast Charger

    50W, 10.8A, multiport USB charger with wattmeter that intelligently detects and adapts to device charging speed

    The Pirl Charger is a high capacity USB charger for consumer devices.

    Current USB chargers restrict you to wall outlets and do not provide any information on how much power devices are drawing.

    We solve these problems by with a DC input charger and a wattmeter LED display. Each port fast charges to 2.7A, and it is a robust build of aluminum plates, which makes it durable to be used at home, in a car, with lead acid batteries and battery packs.

    It takes DC input ranging from 7V to 17V, and can be used anywhere with wall outlets,

    We’re live on Kickstarter:

  11. Tomi Engdahl says:

    Power USB devices from a vehicle

    IC1 generates 5V from any 7.5 to 76V input—a wide enough range to include the complete range of car-battery voltage plus the 40V spike that can occur during a load dump. The IC is simple to use because it has an internal power switch and requires no compensation circuit.

    IC2 distributes to two outputs the 5V that IC1 generates. It not only distributes power but also protects against overload conditions. Most portable equipment receives its power or charge through a USB (Universal Serial Bus) interface, whose current limit is 500 mA. Because IC2 targets use in USB applications, it latches off any port that tries to deliver more than 500 mA but does not affect the other port. Automatic-restart capability ensures that the port recovers automatically after the removal of the overload condition.

  12. Tomi Engdahl says:

    Charge Your Phone with a Hand Crank Generator

    Wanna charge your phone in the apocalypse? Maybe my hand crank generator can help you.

    Anyway, let’s get started. Here are the major components: a servo motor, a diode, a polarised capacitor and a 5V boost module.

    Step one, convert the servo motor to a hand crank generator. Disassemble the servo motor. Desoldering all the wires on the board. Solder the wires and motor together. Also, remember to remove all the locking parts on the gear. After that, you can reassemble all the pieces together.

    Step two, solder the boost module, diode, capacity, and server motor together and turn them into a complete circuit. A diode is very important in this circuit. Since the hand crank mechanism can go either clockwise or anti-clockwise, the diode can prevent the current flow in a wrong direction.

  13. Tomi Engdahl says:

    Charge Your Phone with a Hand Crank Generator
    Wanna charge your phone in the apocalypse? Maybe my hand crank generator can help you.

    Solution : A Portable Hand Crank Generator

    In case of emergency, like Bear Grylls, we need a battery charging solution that is robust, accessible and portable. For god’s sake, coin battery and potato battery is apparently not an option.

    Therefore, I decided to make a hand crank battery charger. Using the human-powered generator to create electricity via motion and forces have already got a long history.

    Anyway, let’s get started. Here are the major components: a servo motor, a diode, a polarised capacitor and a 5V boost module.

    Step one, convert the servo motor to a hand crank generator.

    Step two, solder the boost module, diode, capacity, and server motor together and turn them into a complete circuit.

    A boost module is needed because the servo motor can only generate 1–3 volt which is far from the 5-volt standard to charge our mobile phone.

  14. Terri says:

    I do not even know the way I finished up right here, but I thought this put
    up was great. I don’t realize who you might be however certainly you’re going to a famous blogger when you are not already.

  15. Tomi Engdahl says:

    QC3.0 Hacking and Tutorial incl. QC2.0 (Mobile Power Supply) with Arduino

    QC3.0 is the new standard for charger used by many companies, and therefore we get lots of compatible power banks and wall chargers. They deliver up to 12 volts and later up to 20 volts. And the voltage can be adjusted. Sounds like ideal for a Lab or a Mobile power supply. But unfortunately, the standard is proprietary. So let’s hack it using an Arduino Mini or an ATtiny.
    The old USB chargers were able to deliver 5 volts and around 2-amperes max. The new QC chargers provide up to 12 volts and 2A peak. And you can change the voltage on the fly. Sounds interesting and dangerous! I do not want to charge my trusted old iPhone with 12 volts.

  16. Tomi Engdahl says:

    Teardown of a Hidden Spy Camera
    When is a USB charger not just a charger?

  17. Tomi Engdahl says:

    Beat the Heat: Build a Compact, Multi-Standard Dual USB Charger

    USB ports in automotive charging applications must fit inside small spaces without overheating—a problem exacerbated when there are two ports. This automotive-grade dual-port charger solution overcomes those challenges.

    USB ports are pervasive in automobiles. With the intermediation of the proper cable, numerous portable devices, smartphones, and tablet PCs can be charged on the go. The electronic modules that implement these functions must fit inside small spaces without overheating.

    The problem is exacerbated in the case of dual-port dedicated charging solutions

  18. Tomi Engdahl says:

    Apple Power Supply Nightmares (023)

    Courtesy of Gordon Ramsay’s Kitchen Nightmares editing crew, here is a power supply teardown, reality TV style.

  19. Tomi Engdahl says:

    … Apple software engineer Forrest Heller broke down the specs for three consumer USB-C chargers, including the Google Pixel 18-Watt Charger, Huawei 40-Watt SuperCharge, and the Anker PowerPort Atom PD 2.
    Heller compares the Random Access Memory (RAM) between an 18-watt Google Pixel USB-C charger and the Apollo Guidance Computer, for instance. He found that the Anker charger has eight kilobytes of RAM compared to the Apollo computer, meanwhile, has four kilobytes of RAM.
    After looking at RAM, clock speed, program storage space, and a few other components, Heller concluded that today’s USB-C chargers are more or less 563 times faster than the Apollo computer.

    Your USB-C Charger Is More Powerful Than Apollo 11′s Computer
    But your power adapter won’t take you to the moon.

  20. Tomi Engdahl says:

    6 battery life facts about the Galaxy S20, iPhone 11 and other top phones

    We asked battery experts what fast chargers do to our phone’s battery over time and how to extend its life. Here’s what we learned.

  21. Tomi Engdahl says:

    standard USB charging works in such way that the charger supplies 5V and give out some current. The phone at slow charging takes around 500 mA current. If it can determine in way or another (the are standard and manufacturer specific methods) charger can supply more current, it will determine the safest maximum current (up to 2.4-3A), and take that or less as it needs.
    With quick charge the phone can tell the charger that it prefers higher than 5V voltage (like 9V or 12V) for very quick charging and compatible charger can fullfill that wish. USB-C interface can support similar voltage/current adjustment from 5V up to 20V 5A if suitable charger is used.

  22. Tomi Engdahl says:

    Properly designed Lithium battery chargers used in smart phones have tight current and voltage controls what they send to the battery. They give the battery the maximum current it can safely take or maximum current the charger can output, whichever of them is lower.
    Adding a higher current 5V power supply won’t be a problem to such designs. Having power supply with much higher than about 3A current does not make sense with micro-USB (and 5A with USB-C), does not increase charging speed, just increases changes of serious problems if short circuit happens.
    If you connect 5V 100A PSU to your thin USB cable and cause short circuit on output, you have very quicly a flaming smoking fried cable.

  23. Tomi Engdahl says:

    BadPower attack corrupts fast chargers to melt or set your device on fire

    Attackers can alter the firmware of fast charger devices to deliver extra voltage and damage connected equipment.

    Chinese security researchers said they can alter the firmware of fast chargers to cause damage to connected (charging) systems, such as melt components, or even set devices on fire.

    The technique, named BadPower, was detailed last week in a report published by Xuanwu Lab, a research unit of Chinese tech giant Tencent.

    According to researchers, BadPower works by corrupting the firmware of fast chargers

    A fast charger looks like any typical charger but works using special firmware. This firmware “talks” to a connected device and negotiates a charging speed, based on the device’s capabilities.

    If a fast-charging feature is not supported, the fast charger delivers the standard 5V, but if the device can handle bigger inputs, the fast charger can deliver up to 12V, 20V, or even more, for faster charging speeds.

    The BadPower technique works by altering the default charging parameters to deliver more voltage than the receiving device can handle, which degrades and damages the receiver’s components, as they heat up, bend, melt, or even burn.

    When the user connects their infected smartphone or laptop to the fast charger, the malicious code modifies the charger’s firmware, and going forward the fast charger will execute a power overload for any subsequently connected devices.

    The Tencent team said they verified their BadPower attack in practice. Researchers said they selected 35 fast chargers from 234 models available on the market and found that 18 models from 8 vendors were vulnerable.

    The good news is that “most BadPower problems can be fixed by updating the device firmware.”

    Researchers said that 18 chip vendors did not ship chips with a firmware update option, meaning there was no way to update the firmware on some fast charger chips.

    Suggestions to fix the BadPower problem include hardening firmware to prevent unauthorized modifications, but also deploying overload protection to charged devices.

    A demo video of a BadPower attack is available at the bottom of the Tencent report

  24. Tomi Engdahl says:

    By rewriting improperly-protected firmware from the USB port, it’s possible to send 20V to devices only capable of receiving 5V.

    “BadPower” Attack Leverages High-Speed USB Charging to Damage Devices, Start Fires

    By rewriting improperly-protected firmware from the USB port, it’s possible to send 20V to devices only capable of receiving 5V.

  25. Tomi Engdahl says:

    Supply #power to two #USB devices from a vehicle’s cigarette lighter or other power source with this design #DIWednesday #DesignIdeas #CircuitDesign

  26. Tomi Engdahl says:

    Unohda jo koko yön kestävä puhelimen lataaminen – asiantuntija kertoo, miten nykyakun saa kestämään

    Ethän enää lataa puhelinta yöpöydällä kahdeksaa tuntia putkeen? Tämä ohje on jo vanhentunut.

    Nyt, vuonna 2020, älypuhelimen akku tyhjenee aamupäivässä. Lataussuositukset ovat kuitenkin vuosien varrella muuttuneet!

    Akun voi myös pilata niin sanotusti vahingossa. Pahimmillaan vääränlaiset latauslaitteet rikkovat akun, varoittaa Fonum Oy:n huoltopäällikkö Sami Vaittinen.

    – Uusimmissa laitteissa on sisäänrakennettu optimoitu lataus, joten liian pitkään laturissa olo ei varsinaisesti vahingoita akkua. Nykyisten mobiililaitteiden akuille suositellaan kuitenkin porrastettua latausta käyttöiän pidentämiseen, eli laitetta pitäisi ladata muutamia kertoja päivän aikana, ja esimerkiksi illalla akku ladataan täyteen.

    Älä pidä koko työpäivää kiinni laturissa
    Enää puhelinta ei siis suositella ladattavan yöpöydällä yön yli. Sitä ei myöskään suositella pidettäväksi koko työpäivää kiinni laturissa.

    – Suositukset muuttuvat tasaisin väliajoin, ja tällä hetkellä tehokkain lataustapa on porrastettu lataus. Eli esimerkiksi käytät akusta vaikkapa 30 prosenttia, lataat 20 prosenttia, käytät akun loppuun ja lataat taas täyteen. Tällainen porrastettu malli olisi nykyakulle sopivin. Huonoin tapa on ladata koko päivä, Vaittinen sanoo.

    Kun akku on täynnä, se on täynnä. Virtaa ei mahdu akkuun sen enempää, vaikka johto olisi kiinni seinässä 12 tuntia.

    – Kuuma ja kylmä ääripäissään myös heikentävät akkua, joten kuumaa tai kylmää puhelinta ei suositella ladattavaksi. Anna puhelimen lämpötilan tasaantua ennen latausta.

    – Varsinkin vanhemmat akut voivat sammua kylmässä, vaikka akun varausta olisi vielä jäljellä 30 prosenttia. Lämmetessään laite taas käynnistyy normaalisti, mutta sama toistuu usein kylmään mennessä. Uuden akun varaus on voi myös olla erittäin heikko kylmissä olosuhteissa ja kulua erittäin nopeasti, Vaittinen kuvaa.

  27. Tomi Engdahl says:

    Billions of accessories in the bin, and having to buy more dongles, that’s what it means for us.

    No more Lightning port: What will that mean for us?

    Billions of accessories in the bin, and having to buy more dongles, that’s what it means for us.

    It seems increasingly likely that Apple is getting ready to phase out the Lightning port. Whether the iPhone 13 will rip off the Band-Aid in one go, or whether we’re in for a protracted death (a prominent Apple watcher has recently softened on a previous claim it would happen this year), the writing is on the wall, and all signs point to the charging port’s days being numbered.

  28. Tomi Engdahl says:

    Apple not switching to USB-C iPhones in the near future, according to Ming-Chi Kuo
    The dream is dead

    The dream of a USB-C iPhone may be dead, according to the latest research note from Apple analyst Ming-Chi Kuo. The company reportedly has no plans to adopt USB-C on future iPhone devices or integrate a Touch ID sensor into the power button (two technologies that exist on Apple’s iPad hardware, like the 2020 iPad Air).

    The report, obtained by AppleInsider, explains the rationale behind Apple’s decision: “We believe that USB-C is detrimental to the MFi business’s profitability, and its waterproof specification is lower than Lightning and MagSafe,” according to Kuo.

    Therefore, instead of a USB-C iPhone, Kuo suggests that Apple may jump straight to a long-rumored portless iPhone that relies exclusively on wireless charging — and specifically, Apple’s MagSafe technology — to charge. MagSafe, in particular, would provide a neat solution to both of the concerns Kuo raises: by eliminating ports, MagSafe would be even more waterproof than even Lightning, and Apple still controls the MagSafe standard through its MFi program, ensuring it’ll be able to continue to reap the rewards of licensing fees.

  29. Tomi Engdahl says:

    How does a mobile charger work? SMPS with Opto-Coupler.

    This is an animated video on the working of a mobile/smartphone/cellphone charger that converts 220 Volts AC to 5 Volts DC with the help of an optocoupler using Switch Mode Power Supply(SMPS).

    Both the transistors, S8050 and 13001, are NPN Bipolar Junction Transistors.
    The numbers on SMD Resistors are their values in ohm (Ω), not their codes.

    Correction- In the video the fusible resistor is 2.6Ω and not 260kΩ.

  30. Tomi Engdahl says:

    Charging Phone DANGEROUS?! ElectroBOOM Crew EXPOSED!!! (LATITY-004)

  31. Tomi Engdahl says:

    Single Transistor Mobile Phone Charger

    The Single transistor mobile phone charger is known for its size, price, and easy usage.

    These cheap mobile charger use only a few parts, a very simple SMPS design.

    But there’s a drawback too, they got damaged easily.

  32. Tomi Engdahl says:

    We all know not all USB power supplies and cables are created equally, but how bad are they really?

  33. Tomi Engdahl says:

    Pelikoneistaan enemmän tunnettu Razer on esitellyt GaN-pohjaisen minikokoisen laturin, joka voi syöttää virtaa sadan watin teholla kahteen eri laitteeseen.

  34. Tomi Engdahl says:

    A short primer on USB Type-C PD 3.0 specification and design

    The USB Type-C connector and power delivery (PD) specification has brought radical changes to the mobile device industry, and USB Type-C PD 3.0 could optimize battery charging for portable devices. Single cable solutions for consumer electronics and computing device connectivity and PD has simplified life for consumers who were long plagued by a plethora of proprietary power adapters for phones, tablets, and notebook computers. It has also helped drive innovation in charger design with increasingly small form factors and variants such as differing power levels, two or more charging ports in power bricks, and automotive adapters.

    Developed under the auspices of the USB Implementer’s Forum, and subsequently adopted as International Electrotechnical Commission (IEC) standard, there are two compatible specifications for USB-PD; both support bi-directional charging at power levels up to 100 W. The first one—Power Delivery 2.0—supports fixed output voltages including 5, 9, 12, 15, or 20V at specific operating currents, for example 3 A. The second specification—PD 3.0—includes programmable power supply (PPS), a feature that allows the USB Type-C charger’s output voltage to be adjusted in increments as small as 20 mV over voltages ranging from 3.3 to 21V. With a PD 3.0 PPS USB-C charger, portable devices can optimize battery recharging time and battery life.

  35. Tomi Engdahl says:

    Should you buy a GaN Power Adapter? Or is it a scam? || Testing GaN FETs!

    In this video we will be having a closer look at GaN FETs in order to find out whether they will improve power electronics products in the future. For that I got myself a commercial GaN power adapter which I will compare with a more traditional power adapter concerning their efficiency. Afterwards I will measure the resistance and switching speed of a proper GaN FET and finally use it in a buck converter circuit to demonstrate the difference to a normal MOSFET. Let’s get started!

  36. Tomi Engdahl says:

    Anker Nano II 30W USB C Power Adapter Review

    In this video I take a detailed look at the performance of the Anker Nano II 30 watt USB C power adapter. The adapter overall seems like very high quality. It appears to be worth the little extra price you pay.

    Does Small Power Supply Quality Matter?

  37. Tomi Engdahl says:

    How does a modern Power Supply work?! (230V AC to 5/12V DC) DIY Flyback Converter!

    In this video we will be having a look at the kind of power supplies you use every day. I am talking about switched mode power supplies that convert our 230V AC mains voltage into for example 5V or 12V DC to power our electronics. I will not only tell you all about the heart of such a system, a flyback transformer, but I will also show you how it is used in a flyback circuit. At the end I will also show you a DIY attempt of such a mains power supply that you should (please) not replicate. Let’s get started!

  38. Tomi Engdahl says:

    Näin USB4 lataa

    USB-liitäntä on levinnyt jo kaikkialle. Lähes jokainen älypuhelimen käyttäjä on jossain vaiheessa tuijottanut liitäntäporttia miettien, latautuuko puhelin ja kuinka nopeasti. Uusi USB4-versio tuo tähän helpotusta ja vähentää huonoja käyttökokemuksia. Älykkään viestinnän avulla USB4-väylään kytketyt laitteet voivat sopia keskenään tehonsyötön tärkeimmistä yksityiskohdista.

    USB4-kehitystyön päätarkoituksena on kaksinkertaistaa tiedonsiirtonopeus verrattuna USB 3.2 -versioon eli yltää 40 gigabitin sekuntinopeuteen ja mahdollistaa samalla tuki Intelin kehittämälle Thunderbolt-protokollalle. USB4-standardi hyödyntää yksinomaan C-tyyppistä USB-porttia, jossa mekaaninen ohjauslevy sijaitsee soikiomaisen liittimen keskellä. Rakenne tunnetaan erityisesti siitä, että pistokeliitin voidaan työntää porttiin kummin päin tahansa.

    USB4-portin taustalla olevan lataustekniikan on nyt sisällettävä myös USB PD -ominaisuudet, mikä lisää ratkaisun monimutkaisuutta. Aiemmissa USB-määrityksissä, joissa käytettiin C-tyyppistä porttia, oli mahdollisuus sallia PD:n käyttö, mutta USB4 vaatii sen.

    USB4:n vaatima PD-tehonsyöttö

    Liitännän PD-määrityksiä päivitettiin ottamalla mukaan uusia viestintätapoja USB4-moodin havaitsemiseen ja siihen siirtymiseen, mutta itse tehonsyötön ominaisuudet pidettiin ennallaan. Nelosversiossa käytetään yksijohtimista 300 kilohertsin väylää toisella USB-C-liitännän CC-linjoista (Configuration Channel) isännän ja laitteen väliseen viestintään. Sen avulla tunnistetaan ja sovitaan siirrettävät tehot sekä varsinainen datansiirto.

    Toinen CC-linja toimii ’VCONN’-roolissa eli erillisenä teholähteenä elektroniselle markkerille (USB-kaapeliin sijoitettu tunnistuspiiri). USB-porttien kesken syötettävä teho siirretään liittimien sisältämien erillisten johtimien kautta (’VBUS’).

    Kun kaksi PD-laitetta yhdistetään, ne käyttävät CC-johdinta toistensa havaitsemiseen ja tehonsyötön ominaisuuksista sopimiseen (mitkä jännitteet ja kuinka paljon tehoa siirretään kullakin jännitteellä) sekä ilmaisemaan, minkä laitteen tulee syöttää tai vastaanottaa tehoa ja kuinka paljon. Ja sen jälkeen vastaamaan tämän tehon siirtämisestä VBUS-väylälle.

    Tätä 300 kHz digitaalista signaalia käytetään myös tunnistamaan, että liitäntä kykenee tukemaan USB4-linkkiä, joten USB4-liitäntää ei voi toteuttaa ilman tätä tiedonsiirtoa. USB4-porttien ei tarvitse syöttää tai vastaanottaa yli 900 mA virtaa viidellä voltilla, mutta niiden on tuettava PD-tiedonsiirtoa toimiakseen USB4-liitäntänä.

    Aiempien USB-väylien tehotasot

    Arvioitaessa USB4:n latauskäyttöön liittyviä ominaisuuksia, on hyödyllistä ymmärtää erityyppisten USB-liitäntöjen historiaa tehonsyötön kannalta (kuva 2).

    Alun perin Universal Serial Bus tarkoitettiin sarjamuotoiseen tiedonsiirtoon, ja kaapelissa voitiin siirtää enintään 100 milliampeeria virtaa. USB 2.0 -määrityksissä VBUS-linjan virtaraja nostettiin 500 milliampeeriin, mikä riitti tietokoneen perusoheislaitteiden virransyöttöön. USB 3.0 -standardissa virtalukema nousi 900 milliampeeriin, mutta kannettaville laitteille, joissa tarvitaan tehon ja datan syöttämistä saman liittimen kautta, tämä ei riitä.

    Myöhemmin USB-komiteat julkaisivat akun lataamiseen liittyvät BC-määritykset, joista viimeiseksi jäi vuoden 2010 standardi BC1.2, joka salli 1,5 ampeerin virran (7,5 W tehon). Siinä vaiheessa monet älypuhelinten valmistajat kuitenkin luopuivat yhteensopivuudesta USB-määritysten kanssa.

    Tämä johti lataamisessa vapaasti sovellettavaan vakiotapaan, jossa käytetään USB-datalinjoille (D+ ja D-) asetettuja jännitetasoja: 2 volttia toisella linjalla ja 2,7 V toisella linjalla antaa latausta varten 10 watin tehon. Molemmille linjoille syötetty 2,7 V taas antaa lataustehoa 12 wattia. Ja kummallekin linjalle syötetty 3,3 V jännite antaa lataustehoa 20 W (mikä voi olla jo tuhoisaa väärin syötettynä).

    Nämä menettelyt eivät olleet toiminnaltaan yhteensopivia, ja tulokset saattoivat olla arvaamattomia. Lisäksi lataustasojen päättämiseen käytettävät datalinjat eivät olleet enää käytettävissä varsinaista dataa varten. Portti pystyi siirtämään tiedostoja tai lataamaan akkua nopeammin, mutta ei molempia. Jos käyttäjät ovat joskus ihmetelleet puhelimen hiipumista kesken latauksen, syynä on todennäköisesti ollut datansiirtoportti, joka syöttää vain 500 mA USB 2.0 -spesifikaation mukaisesti.

    Tämä ongelma motivoi luomaan ensimmäisen PD-spesifikaation (Revision 1), jotta saataisiin yleinen standardi lataukselle vaihtoehtoisilla (yli 5 V) jännitteillä käyttämällä perinteisiä nelijohtimisia USB-kaapeleita. Yhteensopivuuden ylläpitäminen taaksepäin edellytti kuitenkin kättelysignaalin lisäämistä itse VBUS-linjaan, mikä taas oli monimutkaista toteuttaa, ja koko hanke romutettiin nopeasti ilman merkittävää käyttöönottoa. Soveltajien yhteisö USB-IF toivoisikin kaikkien jo unohtavan, että tätä speksiä on koskaan edes kirjoitettu – ja käytännössä näin pitäisi tehdäkin. Tämä lähestymistapa ei enää ole pätevä eikä sitä tueta.

    Nykyään käytössä ovat PD-versiot 2.0 ja 3.0 sekä niihin sisältyvät ohjelmoitavien teholähteiden PPS-määritykset. Ne luotiin lisäämällä C-tyyppisen USB-portin rinnalle uusia signaaliliitäntöjä. Kakkos- ja kolmosversioiden väliset erot liittyvät lähinnä CC-viestinnän yksityiskohtiin. Molemmat ovat taaksepäin yhteensopivia aiempien USB-toteutusten kanssa (lukuun ottamatta PD-versiota 1) ja käyttökokemukset ovat yhteneviä.

    Laitteet kykenevät sopimaan latausprofiileista parhaimmillaan jopa 20 millivoltin välein (PPS-toteutuksissa). PD-yhteensopivat laitteet voivat (mutta niiden ei tarvitse) tukea jopa 100 watin tehonsiirtoa spesifikaation mukaisesti (5 ampeeria 20 voltin jännitteellä). Soveltajien omat rakenteet vaihtoehtoisten latausprofiilien tarjoamiseksi datalinjojen avulla ovat nimenomaisesti kiellettyjä, mutta C-tyyppinen USB mahdollistaa myös yksinkertaistetun 1,5 tai 3 ampeerin latauksen viidellä voltilla (tunnistuksen hoitavat CC-nastaan liitetyt vastukset digitaalisen signaalin sijaan). C-tyyppiset portit eivät vaadi PD:tä, mutta PD vaatii C-tyyppisen portin, ja siinä USB4 muuttaa asioita – PD-tiedonsiirtoa käytetään USB4-moodin sallimiseksi.

    Vaikka uudet laitteet noudattavat paranneltuja spesifikaatioita, USB-latauksen monimutkaisuus on seurausta vanhoista standardeista, jotka ovat edelleen käytössä perinteisissä USB-porteissa. Uusi USB4 voidaan liittää mihin tahansa näistä vanhoista porteista.

    Kun yritetään ylläpitää taaksepäin yhteensopivuutta yli viiden sukupolven, syntyy monimutkainen näkymä mahdollisista tehonsyötön liitäntätavoista. Se jättää avoimeksi tärkeän kysymyksen siitä, mitä tapahtuu kaikille vanhemmille USB-porteille ja -kaapeleille. Käyttäjät saattavat ihmetellä, latautuuko porttiin liitetty laite lainkaan. Jos jätetään huomiotta valmistajien omat viritykset, tämä onneksi koskee vain muutamia käyttötapauksia USB-latauksen historiassa. Kaikki laitteet latautuvat, mutta ne eivät aina lataudu nopeasti.

  39. Tomi Engdahl says:

    EU haluaa kaikkiin puhelimiin samanlaiset lataus­liitännät

  40. Tomi Engdahl says:

    European Union Will Force Apple to Use the Same Charger as Everyone Else
    A new 18 page directive from the European Commission outlines a beautiful future where everything runs on the same charger.

    The European Union announced on Thursday that it will force manufacturers to adopt a universal phone charger, meaning the iPhone will have to use USB-C or whatever standardized charger regulators decide to use and will no longer be able to use Apple’s proprietary Lightning Charger.

    According to the AFP, the European Commission released an 18 page directive that outlined the new legislation it said was aimed at reducing waste and saving EU consumers millions of dollars a year.

  41. Tomi Engdahl says:

    Kännyköiden ainoaksi latausliitännäksi USB-C

    Euroopan komissio ehdottaa mobiililaitteiden lataukseen USB-C-liitettävää yleislaturia. Käytännössä vain Apple haraa vastaan ja aikoo pysyttäytyä lightning-liitännässään. Vai siirtyykö Apple kokonaan langattomaan lataukseen?

    Matkapuhelinten latausratkaisujen määrää on saatu vähennettyä jo vapaaehtoisuuteen perustuvalla lähestymistavalla 30:stä kolmeen viimeisen vuosikymmenen aikana. Nykyisin on jo Android-laitteissa USB-C ja vanhemmissa MicroUSB. Vain Applen iPhone-laitteissa käytetään omaa Lightning-liitäntää.

  42. Tomi Engdahl says:

    Näin Apple ratkaisee laturiongelman

    Euroopan komissio ilmoitti eilen valmistelevansa lainsäädäntöä, jonka mukaan älypuhelimissa sallitaan vain yksi fyysinen liitin. Universaaliksi liittimeksi on valittu odotetusti C-tyypin USB, mikä aiheutti Applella luonnollisesti valitusta. Yhtiö tulee kuitenkin ratkaisemaan ongelma elegentisti.

    Apple voisi helposti tuoda USBC-latauksen älypuhelimiinsa. Jo nyt useasta Macbook-tietokoneesta löytyy USBC-laturi. Tämä ei ole Applelle iso suunnitteluongelma ja itse asiassa pikalatauksen standardoiminen eli komission ehdotuksen toinen iso asia, voisi jopa auttaa Applea latausnopeuskisassa.

    Jos laturilaki tulee voimaan, Applella olisi 24 kuukautta aikaa muuttaa älypuhelimiensa latausratkaisu. Tämä tarkoittaa aikaisintaan iPhone 15 -polvea, todennäköisesti myöhempiä malleja. Monen analyytikon mukaan Apple tulee ratkaisemaan ongelman poistamalla puhelimistaan kaikki fyysiset liittimet.

    Tälle on paljonkin perusteita. Langattoman latauksen teho on kasvanut selvästi viime aikoina. Esimerkiksi OnePlussalla on langaton laturi, joka yltää parhaimmillaan 50 watin tehoon (kun laitteessa on kaksi erillistä kennoa ja laturissa kaksi latauskäämiä). Apple pääsee langattomassa latauksessa helposti samaan 15-20 watin tehoon, mihin se yltää nyt omia kaapeleitaan pitkin.


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