The battery capacity of modern smartphones is constantly growing, but power consumption is also increasing. An increase in battery capacity has a positive effect on autonomy, but leads to an increase in charging time. If a device like the first iPhone or HTC HD2 could be charged from a USB 2.0 port in 2 hours, now some Lenovo Vibe P2 will take about 10 hours to do this. To reduce the time spent on charging, manufacturers are actively implementing support for the fast charge function.
Fast charging in a smartphone is a technology that works on the principle of increasing the current, which is supplied to the battery from the power supply. Initially, power supplies for charging mobile devices supplied a voltage of 5 V with a force of 500-1000 mA. But with such parameters, theoretically, in an hour, you can replenish the battery capacity of a smartphone for more than 1000 mAh. In practice, this value is even less, since the more the battery is charged, the more the current has to be reduced.
The very first way to speed up the charging process was to increase the amperage. Early technology made it possible to deliver amperage up to 2 amperes at 5 volts, which gave a power of 10 watts. However, it turned out to be difficult to move further in this way: for high currents, thick wires are required, since the resistance of the conductors depends on this. With a low-quality cable, even 2 A is not easy to get, as there will be drawdowns.
It is problematic to use a cable with a large cross-section of conductors, so the manufacturers decided to go by increasing the voltage, while maintaining the same current strength. However, lithium batteries require a voltage in a narrow range to charge; it is impossible to supply "clean" 12 V to the contacts. To solve the problem, special charge controllers have been developed that are built into the chipset or on the motherboard. They accept voltages above 5 volts, converting it to the optimum for the battery cells.
Types of fast charging for smartphones
In order to improve charging speeds, smartphone component manufacturers are developing new fast charging technologies. Qualcomm offers QuickCharge, MediaTek has a rival PumpExpress, and OPPO has a counterpart called VOOC. Samsung offers Fast Adaptive Charging to users. Asus smartphones support Asus BootMaster, Motorola supports TurboPower, and Huawei supports SmartPower.
Current generations of QuickCharge and PumpExpress are capable of using different voltages, power supplies can supply from 5 to 12 V. The charger interacts with the charge controller, from which it receives "hints" what current and voltage should be given at the moment. Both step regulation (5, 9, 12 V, etc.) and smooth (from 3.2 to 20 V, with a step of 200 mV, used in QuickCharge 3.0) can be used.
Since the chipset is responsible for wireless charging, the type of technology used depends on it. The methods of Qualcomm, Samsung, Mediatek, Huawei, that is, companies producing chipsets, can be considered independent. Oppo's VOOC stands out. It is realized through the use of multi-cell batteries that can be charged in parallel. Due to this, you can "fill" 2500 mAh in just 15 minutes.
Other fast charging technologies are usually QuickCharge-based variations with a different name. But in general, they all use the same principle: first, the power supply gradually increases the current and voltage, selecting the maximum possible parameters, then at maximum power, it charges up to 50-70% of the capacity, and then there is a gradual decrease in the current and voltage.
Is wireless charging harmful to smartphones?
Lithium (lithium-ion and lithium-polymer) smartphone batteries are sensitive to charge strength. Using a low-quality charger, charging and discharging with excessively high currents can reduce their resource, therefore, there are statements about the dangers of fast charging.
In fact, a power controller is a rather complex device that is able to select the optimal mode of capacity replenishment. While the charge density in the battery cell is low, it selects the maximum possible charging power. With an increase in density, chemical processes in the battery accelerate, heating increases (and it is he who is harmful). The controller detects this and reduces the power supply to prevent overheating. As a result, the temperature regime is maintained within normal limits, the negative impact on the battery is minimized.
Can a smartphone explode due to fast charging?
News about smartphone explosions often pops up on the Internet, and horror stories about the fact that this is happening due to fast charging are very common. In theory, this is indeed possible, but often the problem is not in fast charging technology, but in faulty equipment. Using low-quality power supplies and cables, using smartphones with a damaged battery, deformed case, etc. - these are the main causes of explosions and fires.
To avoid a fire, explosion or simply swelling of the battery, it is enough to follow a few simple rules. Do not cover an infected smartphone with a pillow or other object, leave it charging on a windowsill or car panel heated in the summer sun. It is also not recommended to use cables and power supplies of dubious origin.
A long process of charging a phone is a very common problem among users of modern gadgets. There is often not enough time to recharge, and the battery will burn out at the most inopportune moment.
Fortunately, smartphone manufacturers, including the Xiaomi brand, solved this problem when they added the function Quick charge- the ability to quickly charge the phone.
What it is
Xiaomi Quick Charge- the ability of Xiaomi smartphones to charge the battery many times faster than normal charging, reaching full battery filling in almost 30 minutes.
Its main task is to fill the battery with the volume that will not damage it as quickly as possible.
How Quick Charge works
The operation of this option is based on a large consumption of current power during the power supply process itself (the limit is 20W). If the battery is completely discharged, the maximum power will be absorbed at the beginning of the power supply, and less and less during the power supply.
Current power according to the formula- product of current (I) and voltage (U). That is, by increasing the current power, either the voltage or the current strength increases, and in this situation the battery receives the required energy charge faster.
A visual explanation of this principle:
How did the creation of Quick Charge begin?
When the Quick Charge function was in its early stages, developers tried different methods to reduce the time to recharge the battery. Initially, Quick Charge relied on boosting amperage. The first power supplies had the ability to receive a current of 2A at a voltage of 5V. As a result, the required power was obtained - 10 watts.
But this method was unpromising, since for subsequent work with the current strength, a change in the wire cross-section was required, and it was decided to increase the voltage instead of the current strength.
Since it was impossible to give the maximum voltage "out of the blue", special controllers began to be added to the motherboard, which are able to receive a voltage higher than the usual 5V, converting it into the required battery charge.
Quick Charge Versions and Maximum Power Consumption
By transforming Xiaomi fast charging, the developers also increased its capabilities, that is, the consumed current.
Features and differences between versions of fast charging Quick Charge
Today there are 4 lines of this technology, but for the most part, Xiaomi uses only three:
- Quick Charge 1.0- version presented in 2013. Literally at once it won consumer sympathy and was used in many phones. Allowed to charge the device 40% faster than usual, which means that the phone could be charged by half after 40-50 minutes. Has been in almost every phone with a Snapdragon processor.
- Quick Charge 2.0- an improved version of fast charging helped to charge the gadget even faster. The charge was halfway already after 30 minutes.
- Quick Charge 3.0- very similar to the previous one, with the exception of a new significant function "INOV" - Intelligent Negotiation for Optimum Voltage - the most accurate selection of the voltage required for charging and control of the "well-being" of the gadget. After 20 minutes the phone can be charged at 50%, and after half an hour - already at 70%!
- Quick Charge 4.0- version based on the new Snapdragon 835 processor. Fills the battery to half after 15 minutes.
In mid-2017, the manufacturer presented a new version from Qualcomm - Quick Charge 4+, which will be able to charge 2750 mAh batteries in half in less than 15 minutes, and with a 5-minute recharge the phone can last up to 5 hours.
INOV technology - Intelligent Negotiation for Optimum Voltage
INOV technology- this is the new ability of Quick Charge to establish an interconnection with the phone during the power process - the unit receives the necessary data about the state of the battery, with the help of which it monitors the received power, current strength, voltage, as well as the temperature of the smartphone.
Similar technology to INOV - Battery Saver Technologies.
Smartphones that support Xiaomi Quick Charge
Unfortunately, not all Xiaomi phones support the fast charging option.
Quick Charge 1.0 version:
- Xiaomi Redmi Note Prime;
Quick Charge 2.0 version:
- Xiaomi Redmi 5;
- Xiaomi Redmi 4x;
- Xiaomi Mi Note;
- Almost the entire Mi range.
Quick Charge version 3.0:
- Mi Note 3;
- Xiaomi Mi Mix 2;
- Xiaomi Mi Mix;
- Xiaomi Mi Max;
- Xiaomi Mi Max 2;
- Xiaomi Mi 6.
Quick Charge version 4.0:
- Already installed on: Xiaomi Mi 8;
- Probably will be installed on: Xiaomi Mi 7, Mi Note 3 Plus, Mi 6 Plus.
Complete list of models:
Some users of the Xiaomi a1 smartphone, after updating the firmware to Android Oreo, thought that the new firmware version supports Quick Charge 3.0, since when the phone is charging, the saying “Fast Charging” appears. However, this is a misconception. Attempts to test have proven the opposite, which suggests that there is no fast charging function on the Xiaomi a1 phone.
If your phone model is not listed, there is no way you can add / purchase Xiaomi Redmi Fast Charger.
How to enable fast charging on Xiaomi
In order to activate the fast charging function on a Xiaomi smartphone, you do not need to go into the settings or use the help of a PC.
Xiaomi phones either have this feature right away or they don't. The Quick Charge is located in the power block itself.
To make sure your smartphone is equipped with this option, inspect the unit. It should contain data on current strength (A) and voltage (V). If these parameters, when multiplied, give power above 10 watts (while conventional chargers absorb only about 4.5 watts), and the fast charging icon is visible, this is indeed a Xiaomi fast charging cable, and you are the lucky owner of a smartphone with this function.
Should I use a power supply that is endowed with a fast charging function with regular phones?
If your smartphone is not in the above lists, then it is not adapted to the ability to charge the battery in a short time. And an attempt to do this using a much earlier released phone with a special block Quick Charge can lead to overvoltage, fire or damage to the gadget - it just stops turning on.
Does the use of this function affect the smartphone itself or the battery
There are a lot of scary opinions about Quick Charge:
- The fast charging option also works in the opposite direction - it absorbs the battery charge faster;
- Damages the battery and leads to its faster "bearing";
- It is not possible or dangerous to charge your phone with Quick Charge while it is turned off.
All of the above has no reasonable arguments and is myths. Moreover, a huge number of people are working on the development of fast charging functions, and many tests and experiments have been carried out to prove that the phone and its battery are completely safe when using Quick Charge or other innovations in this industry.
The only thing that should be avoided when recharging the phone in this case is thick, dense cases and any objects on the phone itself (pillows, clothes, blankets), as this can also lead to excessive heating or overvoltage.
Fast charge function does not work
There are several reasons why Quick Charge refuses to work:
- First of all, the phone will not charge while relying on this feature due to the initial lack of such an option. If this option is important for you, when buying a phone, check with the consultant in advance that it is available in the selected model. As mentioned earlier, simply buying a charger with this function later and putting it into use does not bring anything good in itself.
- If your phone is on the Quick Charge list but still does not charge fast, make sure you are using an original Xiaomi power bank. Do not forget to also find the necessary data on power, amperage and voltage.
- Not updated firmware. Some Xiaomi smartphones, even those equipped with the ability to charge the phone using Quick Charge, need to be updated to the latest version.
- The fast charging option can be disabled if you use the phone to its full extent during power supply, or if there are foreign objects on it;
- Problems with the operation of the firmware or with the phone itself.
Dos and Don'ts While Charging
Many of the myths mentioned above are born from improper use of the fast charging function.
In order not to observe similar failures with the battery in the future from your own experience, you need to be able to properly handle the Quick Charge technology.
Pay attention to the following when using this function:
- Using the phone during power supply (especially excessive) - can lead to overheating, as mentioned earlier, and disrupt the joint operation of the phone with the power supply;
- Charging the phone only at maximum power - if you constantly charge the phone only at the expense of this maximum power, which comes in a fairly short time, and half, the operation of the fast charging function can also be disrupted and soon worn out, so use this function only if necessary.
Articles and Life Hacks
The Quick Charge (QC) set of technologies for fast charging mobile devices, created by the American chip manufacturer Qualcomm, is such a useful thing that almost any smartphone owner has heard about it.
The ability to recharge the battery more than half way in an hour is very attractive.
By now, the fourth version of Quick Charge is already relevant, which clearly indicates that the technology has taken root.
Why fast charging is possible
It would be more correct to put the question differently: why ordinary chargers work so slowly.Each battery model has its own optimal mode, which allows, on the one hand, to avoid damage when the current is exceeded, and on the other, not to charge it for too long.
But in reality it is something averaged: the real values of current and voltage also depend on the degree of filling the battery capacity.
With the growth of the performance level of chipsets, it became possible to dynamically set the memory parameters depending on the current conditions.
Thanks to this, the developers were able to achieve impressive results: accelerating the charging process at the initial and middle stages by several times by increasing the voltage.
This required solving several technical problems.:
- Find the optimal charging modes that do not shorten the battery life.
- Ensure a reliable and safe transfer of sufficient power from the power source to the battery.
- Create hardware and software that allows you to subtly monitor the state of the battery and control the operation of the charger.
What is Qualcomm Quick Charge
If we consider the first and last, fourth, generation of Quick Charge, it becomes clear that this technology has undergone dramatic changes in a short time.
It was originally based on the USB Battery Charging specification, created to standardize the increased power consumption of mobile devices. It allowed the source and receiver to "negotiate" the required voltage parameters.
It is clear that this system requires support of the corresponding protocol by both the chipset and the charger.
The first generation was not very popular, so the mass distribution of the technology began with Quick Charge 2.0, which appeared almost simultaneously with another specification - already "sharpened" specifically for fast charging.
But, unfortunately, Qualcomm's technology, although it had a number of advantages over this standard, was not compatible with it.
The protocol used by INOV (Intelligent Negotiation for Optimum Voltage) technology provided for the ability to intelligently switch between voltage modes of 5, 9, 12 and 20 V. For devices that do not support QC, the default mode is 5 V.
If the presence of QC support was detected, then later the choice of the mode was carried out by the chipset, depending on the state of the battery. The maximum power reached 18 W.
The result appeared to be successful, and the novelty almost became a trendsetter: on its basis, the standards of other companies appeared, completely compatible with it: Samsung and developed by Lenovo, used in Motorola smartphones.
In 2016, a new version appeared - Quick Charge 3.0. The first flagship chipset to support it was the famous Qualcomm Snapdragon 820.
Instead of several fixed modes, it provided for the possibility of discrete voltage variation with a step of 200 mV.
As a result, it took only 96 minutes to fully charge the 3300 mAh battery installed on the top-end LG G6.
The current fourth generation QC has appeared along with the Snapdragon 835 chipset. Compared to the third generation, the charging speed has increased by another 20%. Most importantly, this standard is now fully compatible with USB Power Delivery.
In addition, the Snapdragon 845 has its more advanced 4.0+ version, which brings faster speed and efficiency.
Which devices have Quick Charge
The minimum requirement is the presence of the appropriate type of chipset in the gadget:
- For QC 1.0 - Snapdragon 600.
- For QC 2.0 - Snapdragon 200, 400, 410, 615, 800, 801, 805, 808, 810.
- For QC 3.0 - Snapdragon 821, 820, 620, 618, 617, 430.
- For QC 4.0 - Snapdragon 845, 835.
One of the most famous such situations is OnePlus 3T, but in this case the refusal was justified, since it had its own, albeit losing QC.
But the release of Xiaomi Mi A1 on a "clean" version of Android without a proprietary MIUI shell, which did not have a fast charging function, was met by the fans of the brand without any understanding.
Finally
Qualcomm Quick Charge can be safely considered the most advanced fast charging standard that exists today. And although it did not become the only one, it looks very advantageous against the background of competitors.
And compatibility with the USB Power Delivery specification to a certain extent solved the problem of using "non-native" chargers.
Someone thinks that the future belongs to wireless chargers, someone is nicer than USB Type-C in every outlet. But in any case, QC very seriously makes life easier for users of gadgets, allowing you to save time.
And until they came up with a compact battery with a capacity of several tens of mAh, its relevance is beyond doubt.
The battery life of a modern smartphone is a stumbling block for all manufacturers. You can endlessly increase the power of the chipset, display resolution, use the coolest camera, but all these advantages do not matter if the device lives on charging for only half a day. The obvious solution is to increase the capacity and quality of batteries, but the first is limited by the body of the smartphone, and the second is limited by modern technologies.
As a result, the companies came up with a third, no less elegant way out of this situation: if you can't come up with a smartphone that will run on battery for a week, then you can make it charge so quickly that the operating time is no longer decisive.
About technology
The main factor affecting the rate at which a battery is charged is the current supplied by the power supply. The higher the amperage, the faster your smartphone will charge. However, it is impossible to endlessly and thoughtlessly raise the current strength, as this will entail the need to adapt the rest of the smartphone components involved in charging. In addition, increasing the current will increase the heating of the case.
Therefore, Qualcomm decided to charge smartphones not with current, but with a higher voltage. For this, the power was increased to 10 W, the current - up to 2 A, and the voltage was 5 V. The charging speed with this approach increased by 40%. In the second generation of Quick Charge, they learned to use the voltage of 9 and 12 V, this allowed increasing the power to 36 W and slightly increasing the charging speed.
The main difference between Quick Charge 3.0 is a significant reduction in heating of the case and charger. This is achieved thanks to Intelligent Negotiation for Optimum Voltage (INOV) technology, which allows voltage regulation in 200 mV steps in the range from 3.6 to 20 V.
A point change in voltage depending on the current charge of the battery made it possible not to overheat the case, while the charging time was further reduced. So, Qualcomm promises to charge the smartphone by 80% in 35 minutes. And it completely changes the habits of using a smartphone. Let's talk about this in more detail.
Usage scenarios
Most smartphones now live one business day without charging with average usage. As soon as you switch to a more intense mode (games, for example, or active web surfing in LTE), this time is perfectly reduced to half a day. And then there are three possible options.
In the first case, you turn on the power saving mode and try not to touch the smartphone until the evening, which, you see, is not very convenient.
The second option is to use an external battery. In this case, you must either leave the smartphone alone for an hour or two, or accept the fact that a long wire will stick out of it leading to an external battery. A side disadvantage of this solution is the need to carry such a "power bank" with you, which also weighs as much as a smartphone itself.
Fast charging is a great alternative to the above two scenarios. Finding a free charge for half an hour will not be difficult, especially if you are sitting in a cafe. We connect a smartphone, have a cup of coffee and get an almost fully charged battery, and then use the phone in everyday mode.
Purchase
But why buy such a charger if, in theory, it should come with a smartphone? Unfortunately, even large manufacturers often save on this little thing and put a regular power supply in the box, although the Quick Charge 3.0 inscription flaunts on the package. But even if the smartphone is equipped with an appropriate charger, it usually lies at home, and another one will be needed on the road.
And here the question arises: which power supply to choose? On the one hand, there are expensive solutions from large manufacturers for two thousand and more, but, on the contrary, there are cheap offers from various little-known companies. I don't want to overpay for the brand, but entrusting the charging of the smartphone to a noname company is also scary.
A good alternative to both solutions is the choice of a well-known Chinese company that has been operating in Russia for a long time, but has affordable prices. For example, power supplies with Quick Charge 3.0 are manufactured by Ainy, known to many users for its protective glasses based on Asahi Glass.
All Ainy accessories are tested and rejected at the Shenzhen warehouse. Therefore, at a relatively low price (only 800 rubles), their chargers are of the quality of large manufacturers.
Conclusion
If your smartphone supports Quick Charge 3.0 fast charging, but the kit did not have the appropriate power supply, or you want to have another charger for travel, then it makes sense to look at Ainy chargers. To get the opportunity to charge your smartphone by 80% in half an hour for only 800 rubles is an excellent offer.
Fast forward ten years in thought: the first iPhones, various communicators on Windows Mobile and the first smartphones on Android are being sold on the market. All of them have batteries with a capacity of 1200-1500 mAh and charging for ~ 1 A and 5 V, which made it possible to fully charge the battery in one and a half to two hours. Taking into account that the devices of that time for the most part at least calmly lived until the evening, or even lived for more than a day in general - rarely anyone complained about the long charging time.
But as time went on, the capacity of the batteries began to grow, the battery life began to fall, and the charging remained the same: all this ultimately led to the fact that we often had to spend hours near the outlet, just for the smartphone to survive until the evening. And, of course, manufacturers began to solve the problem: since it is impossible to increase the capacity of the batteries even more, then they need to be charged faster - and this is how fast charging standards appeared, which we will talk about today.
USB Battery Charging Revision 1.2
The standard was adopted by the USB consortium back in 2011 - that is, any manufacturer who equipped their device with a USB port could use it absolutely free of charge. Moreover, if the standard USB 3.0 gave out no more than 900 mA at 5 V, then the current already rises to 1.5 A - more than one and a half times, which can significantly reduce the charging time.
In fact, it did not receive much distribution: often such a powerful USB port was only in top motherboards and laptops, and it was usually marked with red or a lightning icon:
Alas, smartphone manufacturers also continued to include 1 A and 5 V chargers in the kit, that is, they had to buy chargers with Battery Charging 1.2 separately. But, in any case, this made it possible to charge the devices significantly faster without harming them.
Qualcomm Quick Charge 1.0-2.0
Perhaps the most famous fast charging standard announced by Qualcomm in 2013. Version 1.0 only supported the Snapdragon 600 chipset. The voltage still remained the standard for USB - 5 volts, but the current was raised to 2 A - that is, another third more than that of the BC 1.2. The first version of this standard did not receive much distribution, so it makes no sense to dwell on it for a long time.
QC 2.0 was the first really popular fast charging standard. He worked with devices based on Snapdragon 200, 208, 210, 212, 400, 410, 412, 415, 425, 610, 615, 616, 800, 801, 805, 808 and 810. The main difference from previous standards is that the current has stopped growing, which is now limited to 2 A, but the voltage can rise as much as 12 V. The reason for this is trivial: the vast majority of USB-microUSB cables that existed at that time supported a current of no more than 2.4 A, otherwise they could start to overheat, which was already dangerous ( as we know, heat losses are proportional to the amperage and the square of the resistance). Therefore, Qualcomm chose a different path - it was banal to raise the voltage, and as a result, the maximum power is now 18 W (12V and 1.67 A) versus 10 W (5 V and 2 A) in the first version of QC. 
Of course, to regulate the voltage, special controllers were now used, which should have been both in the charger and in the smartphone itself. They "communicated" with each other using the D + / D- contacts in the USB port, and the smartphone chose the required voltage and current. If the charger did not support QC (that is, did not respond to the special voltage on the D + / D- contacts), then the charging was carried out with a standard current of 1 A at a voltage of 5 V.
Alas, with the release of QC 2.0, the first problems began to arise: due to the sufficiently high power of 18 W, the batteries began to overheat, which negatively affected their lifespan. Of course, the standard laid down a safe temperature range, upon exiting which fast charging was turned off, but manufacturers often turned a blind eye to this, so that marketers could delight users with slogans like "80% per hour".
Things got even worse with the release of the hot Snapdragon 810: given the fact that when connected to charging, Android often increases background activity (for example, programs are updated), which heats up the CPU, plus the battery heats up from fast charging - as a result, users massively faced the rapid degradation of batteries and the dying of motherboards from overheating. This happened especially often with the owners of LG G4, Nexus 5x and Flex. The company, in response to complaints, recommended using fast charging only when needed, and charging with a regular slow one overnight - obviously, users did not appreciate this response and filed a class action lawsuit against LG.
Qualcomm itself does not name the charging time - it just says that it now goes 75% faster than with QC 1.0. Independent tests show that a smartphone with a ~ 3000 mAh battery can be charged with QC 2.0 to 50% in about 40 minutes.
USB Power Delivery
In 2015, USB-C devices began to appear en masse. Since this protocol can contain many different others, manufacturers often began to stop at USB 2.0 or 3.0 - respectively, there were no problems with QC 2.0 support.
But then it became more interesting - the USB consortium creates the Type-C 1.2 standard, which supports a current of 3 A at a voltage of 5 V: for example, the Lumia 950 and 950XL smartphones had just such fast charging. It would seem that everything is great, there should not be any problems with QC: on the contrary, such cables have a special control microcircuit inside that can only work at 5 V, and QC 2.0, as we remember, can raise the voltage up to 12 V. And since in the QC standard there is no check for the presence of such a microcircuit in the cable, all this can sadly end for both the cable and the smartphone.
Of course, Google could not stand aside, and officially recommended that smartphone manufacturers refuse to use USB-C along with QC 2.0. However, as was expected, many manufacturers (for example, OnePlus) assured users that there would be no problems with their cables, but if your smartphone burned out from using a third-party cable, this, as they say, is already your problem.
Further - it is even more "fun": in order to differentiate cables that can pass 3 A, 1.5 A and 1 A, the USB consortium decided to build resistors of 10, 22 and 56 kOhm in them, respectively. But the Chinese, as usual, decided to put only 10 kOhm resistors in cheap cables - this led to the fact that devices with USB-C 1.2 support "understand" that you can take 3 A, and asks for them from the charger. The result here can be absolutely anything - at best, charging will give the current that it can (and it is unlikely to be 3 A), and at worst, it will simply burn out, possibly damaging the connected smartphone.
Towards the end of 2015, the USB consortium releases the specifications of the Power Delivery 3.0 standard, which in the future, most likely, will be used by everyone: for example, it allows you to set the voltage from 5 to 20 V and the current from 1.8 to 5 A, so that in the end the maximum power can reach as much as 100 watts - this is already enough to charge a laptop, and many modern solutions such as Xiaomi Notebook or Apple MacBook are already using it. In this case, the type of connector can be any: USB-C, microUSB, even USB-A, and the transfer goes in both directions: that is, you can charge the smartphone from the smartphone. At the same time, there is backward compatibility with USB-C 1.2, that is, you can charge the same Lumia 950 from charging with PD support. All possible combinations of charges are available below: 
Qualcomm Quick Charge 3.0-4.0
Of course, the company understood that problems with overheating need to be solved, and in 2016, with the release of Snapdragon 820/821, QC 3.0 technology was introduced. Qualcomm stopped chasing power - it still remained within 18 W, but now there was a flexible voltage setting: if in version 2.0 5, 9 or 12 V were rigidly set, then here it was possible to change the voltage in 0.2 V steps in the 3.6 range. -20 V. In addition, the smartphone manufacturers themselves could now limit the maximum voltage, for example, at 12 V. Plus here the fact that the new Snapdragon (821, 820, 620, 618, 617 and 430 are supported) were still colder than the failed 810 th, in the end, we can assume that the problem with overheating has been resolved.
Alas, there was still another problem with USB-C, so using third-party cables for fast charging through this port was still risky. As for charging speed, the company promises that most smartphones with QC 3.0 will charge up to 70% in half an hour:
The QC 4.0 standard was introduced at the end of 2016 and solved many problems: firstly, now it could be used with any USB-C cables - of course, the charging speed will depend on them, but it will still go faster anyway. than with the standard 1 A and 5 V. Its second feature is full compatibility with Power Delivery, so that first the charging polls the connected device if it supports PD, and if not, it switches to QC mode.
The QC 4.0 specification is the same as the 3.0 - up to 18W at up to 2A and up to 12V, and up to 27W through the PD standard. Supported chipsets - Snapdragon 630, 636, 835. According to Qualcomm, the new technology will recharge a device with a 2750 mAh battery in just 5 minutes for 5 hours of use, and in 15 minutes to charge the battery from zero to 50%.
The QC 4+ technology, presented in 2017, does not differ much from 4.0: for example, the Dual Charge technology allows you to split the current into two streams, which reduces the temperature by 3 degrees and increases the charging speed by 15%. Supported chipsets are Snapdragon 660, 670, 710, and 845.
The general table of all QC versions looks like this:
backward compatibility
All QC versions since 2.0 are backward compatible: for example, if the phone has a newer QC version than charging, then a protocol will be used that supports charging, but with the energy efficiency of the version used in the phone. If you connect a smartphone with an older version of QC to charging with a newer version, the effect will be completely similar to using charging with the same version of QC that the device supports.
Power Delivery Compatibility with Quick Charge 2.0 and 3.0
As I wrote above, it is not officially there, but in practice, various options are possible: for example, there are smartphones, such as the Nexus 5x or 6p, that support both PD and QC - in both cases they will charge quickly. The second option - the charger and the gadget will not "understand" each other, and standard slow charging with 1 A and 5 V will go, or charging will not go at all. But there may be the worst option: a device without PD support will be supplied with 3 A and 5 V (USB-C 1.2 standard) due to the "wrong" cable with a 10 kΩ resistor, and then the situation will be unpredictable: the QC standard with such currents does not work, that is, the smartphone may simply burn out, or it may simply refuse to charge. Therefore, if your device supports QC 2.0 or 3.0, choose both the cable and the charger very carefully.
In the final part of the article, we will talk about fast chargers from other manufacturers such as Apple, Huawei, Mediatek and others.
