With the increasingly powerful functions of smartphones, smartphones are not only a simple call tool, but also office tools, life tools, entertainment tools, information terminals, etc., which have become indispensable electronic devices for most people.
The screen of mobile phones is also getting bigger and clearer, bringing consumers a better user experience. At the same time, the power consumption of mobile phones has increased sharply. Smartphones mostly adopt an integrated design, and the battery cannot be replaced. It is difficult for consumers to accept up to 2 hours of charging waiting. For this reason, fast chargers were born in response to demand.
1 .The origin of fast charging – the first generation of fast charger
At the beginning of this century, the USB2.0 protocol stipulated that the maximum value of the current extracted from the USB interface by peripherals was 500mA. With the emergence of smartphones, the charging current of 500mA would make the mobile phone fully charged for a long time.
Therefore, in 2010, the BC (Bat) under USB-IF The tery Charging) group released the BC1.2 standard, extending the charging current to a maximum of 5V 1.5A, which met the needs of consumers for a period of time. However, when smartphones with a battery of more than 3000mAH appeared, some consumers also thought that the charging time of the BC 1.2 standard was too long.
At this time, Qualcomm, a well-known mobile phone chip manur, launched QC1.0 in 2013, and the charging current was extended to 5V. 2A broke through the 1.5A current limit of BC1.2, and the charging speed was increased by 40%. For a while, it was adopted by major mobile phone manufacturers such as Samsung, Google, HTC, Nokia, etc., thus opening the door to fast charging.
2 .The second generation of fast charging – high-voltage fast charging
QC1.0 does bring a better charging experience to consumers. Consumers like fast chargers more and more, and the pursuit of charging speed is also getting higher and higher, which has promoted the rapid development of fast charging technology, and thus triggered a mutual competition between various mobile phone solution providers and mobile phone manufacturers for fast charging.
In Android mobile phones before 2015, most of the charging interfaces adopted Micro USB interfaces. Theoretically, the maximum current that the conventional Micro USB interface can carry is 2A. If the current is increased, there is a risk of overheating the interface.
Therefore, at this time, 5V2A becomes the maximum power of the mobile phone charger. However, the screen is getting bigger and bigger, the battery is getting bigger and bigger, and the time for users to charge is getting shorter and shorter. Therefore, Gaotong Lingji thought of a way. Since the charging current cannot be increased, we can increase the charging voltage to improve the charging power, so there is QC2.0.
In 2014, Qualcomm launched QC2.0. The current of QC2.0 is still 2A, but the voltage is increased to 9V or 12V (classB is increased to 20V, less used, not detailed). At this time, the maximum power can reach 24W (most applications at that time were still 12W and 15W. ), the charging speed is much better than 10W.
Many people may wonder if 9V charges the mobile phone, won’t it burn the mobile phone? In fact, at this time, the internal charging circuit of the mobile phone adds a DC voltage down chip, which converts the input 9V voltage into 5V voltage and charges the mobile phone. In order not to burn 9V charging mobile phones that do not support fast charging, Qualcomm has made a handshake agreement at this time.
Only after the charger shakes hands with the mobile phone will the 9V voltage be output. When there is no handshake, the default 5V voltage is still output, which can charge non-fast charging mobile phones. Thanks to Qualcomm’s influence in the mobile phone market, Qualcomm has a built-in handshake protocol in its Snapdragon (Chinese name: Snapdragon) processor, which is very convenient to use. QC2.0 was quickly widely used by LG, HTC, MOTOROLA, Google, LeTV, Xiaomi and other mobile phone manufacturers All have adopted.
At the same time, some mobile phone manufacturers have seen this business opportunity and launched similar charging protocols, such as Huawei’s FCP, Samsung’s AFC, MTK platform’s PE+, etc. These protocols are somewhat different from QC2.0 in detail, but the overall charging principle is similar. In addition, most of the above protocols use USB D+ and D- to transmit protocols.
Only MTK’s PE+ does not need D+, D-, and directly uses Vbus and GND to transmit protocols, which seems to be more advantageous, but with the MTK scheme, the adoption rate of mobile phone manufacturers is not as high. In the end, MTK’s PE+ fast charging protocol is not as popular as Qualcomm QC2.0.
In 2015, Qualcomm launched an upgraded version of QC3.0 in a timely manner. Compared with QC2.0, QC3.0 raises the voltage accuracy to 200mV and can be continuously adjusted in 3.6 to 12V. In this way, you can choose the most suitable voltage for the internal step-down chip of the mobile phone, so that the mobile phone The heating of the end step-down chip is minimized, and the low temperature can further improve the charging current.
I will not describe this working process in detail here. For details, you can refer to the work “A Brief Discussion on the Evolution and Future Development Trend of Mobile Phone Chargers” in Electronic World in October 2018. The minimum power of the QC3.0 charger is required to be 18W, and it requires an output capacity of 6V3A (6V2.5A was allowed in the early days).
At this time, the charger terminal generally adopts the USBA interface, and the mobile phone terminal generally adopts the Type C interface, which can support current up to 3A, and the charging speed is one Step improvement, but the charging mode is similar to the aforementioned QC2.0, AFC, PE+, etc. At this time, there are also many charger chips compatible with multiple protocols, because their working principle is basically similar.
Manufacturers only need to put multiple protocols in and select them when shaking hands. To illustrate briefly, Samsung’s mobile phone processor has always adopted dual platforms, namely Qualcomm’s Snapdragon and its self-developed Exynos. Therefore, Samsung’s mobile phones generally support both its own AFC charger and Qualcomm’s QC charger.
3. The pioneer of direct charging – VOOC
As mentioned above, high-voltage intelligent fast charging will have a voltage reduction chip on the mobile phone. This voltage reduction chip will have a certain loss and generate heat. As we all know, the battery cannot work at high heat (generally considered to be <60℃), so the heat will limit the power of charging.
While everyone was still studying high-voltage fast charging, a mobile phone manufacturer realized this problem and found another way to adopt the low-voltage high-current direct charging method, which is unique. In 2014, mobile phone manufacturer OPPO launched VOOC1.0, which adopts direct charging mode, that is, the output of the charger is directly loaded to the battery, and there is no voltage conversion circuit inside the mobile phone, so that the mobile phone terminal has the least heat.
When the battery is charged, it is very sensitive to the voltage loaded on it. Slightly higher voltages may cause a decrease in battery life, or even swell, causing safety hazards. Therefore, in direct charging mode, the output voltage of the charger is required to be very accurate, reaching tens of mV. Adopting the low-voltage direct charging mode, the output voltage of the charger cannot be increased, but only the current can be increased.
As mentioned earlier, the current that the general MicroUSB interface can pass is 2A. Since the general one is not possible, VOOC adopts a customized MicroUSB interface, in the ordinary 5PIN Micr On the oUSB interface, add a PIN on both sides to 7 PINs, and share 4 PINs to transmit Vbus and GND. The current is increased to 5A for low-voltage direct charging, so as to achieve “charging for 5min and calling for 2h”.
In this charging method, the power has been increased to 25W, but the heat of the mobile phone itself is very small, which quickly won the love of some consumers. However, this charging mode is a complete set of customized solutions. Chargers, wires and mobile phones must be matched. If there is one that is not matched, it cannot enter the fast charging mode.
The current is also large, and the cost of the corresponding charger and wire is relatively higher. In addition to some patent protection reasons, other mobile phone manufacturers do not have horses. Follow up, continue to use QC2.0 or QC3.0, which is not bad, and have a wait-and-see attitude towards low-voltage direct charging.
4 .The culmination – PD Protocol
The PD (Power Deliver) protocol was actually launched in 2012. The purpose of PD is to unify the interfaces of all power supply devices and all charging methods. Because the standard PD must use the Type C interface for power transmission and handshake, at that time, mobile phones mostly used Micro USB interfaces, so in the early days, it was not adopted by mobile phone manufacturers.
In addition to supporting higher power charging, the Type C specification has also increased the data transmission speed by more than 10 times compared with the previous USB2.0, which is of great help to big data transmission. Therefore, well-known manufacturers Apple and Google took the lead in adopting it on their laptops, driving notebooks. The use of PD of computer manufacturers.
In 2017, USB-IF put forward the concept of PPS (Programmable Power Supply) in PD, which supports a maximum current of 5A and a maximum of 100W of power, allowing voltage to be adjusted from 3.3 to 21V, and allowing manufacturers to be in this category. Custom output voltage and current in the perimeter. Judging from this definition, almost all fast-charging voltage and currents are included, which is also the original intention of USB-IF.
At this time, the mobile phone fast charging camp is going in two directions: foreign mobile phone manufacturers gradually accept the PD protocol and begin to adopt it on mobile phones, such as Apple, Google, Samsung, LG, etc.; while domestic mobile phone manufacturers are more likely to be compatible with the previous charging heads and charging cables, so they hope to still adopt USBA on the charger end. Interface, so in the process of development, it did not immediately cut into the PD protocol, and still retained the mode of D+ and D-communication. Along this road, various manufacturers have derived various charging protocols.
5.Hundreds of flowers compete for the song – the emergence of high-pressure direct charging
Although QC3.0 can reach a maximum power of 60W (Class B), as mentioned earlier, its typical power is still 18W, because if the power is increased, the voltage reduction circuit inside the mobile phone will be very hot, which restricts the further improvement of the power of the charger. If you want to increase the charging power, the heat of the step-down circuit on the mobile phone terminal must be reduced to be realized.
The development of science and technology has two ways: from top to bottom and from bottom to top. The infinite pursuit of charging speed by consumers has promoted the development of upstream devices. In 2017, the charge pump began to be applied to the mobile phone charging system. The charge pump is also known as a switching capacitive voltage converter.
Compared with the traditional inductance switching converter that uses inductance as an energy storage element, it can only get a certain proportion of voltage, such as 1/2 times, 2 times, 3 times, etc. But because there is no high-speed electromagnetic transformation in it, it is more efficient. The mobile phone terminal usually uses a 1/2 times charge pump, and the efficiency can be as high as 98%. The maximum voltage of the mobile phone battery is 4.2V (some use 4.35V, the principle is the same, not to elaborate).
The function of the charge pump is to halve the input voltage and double the corresponding current. Therefore, the input voltage of the charge pump must reach more than 8.4V. Considering some line losses at the mobile phone, usually The supply is matched with the fast charging of the charge pump mobile phone. The output voltage of the charger is generally called 10V, and the current is large.
Considering the greater loop loss, it is nominally called 11V. This is the origin of some 10V2.25A and 11V5A chargers at present. Although the voltage of this kind of charger is not directly loaded on the battery, because the charge pump is only a half-voltage conversion, it does not affect the accuracy of the input voltage and current. The whole charging principle is similar to direct charging, so we generally call it high-voltage direct charging.
Although in this charging mode, the mobile phone terminal will still have a voltage reduction loss, because the efficiency of the charge pump is as high as 98%, the loss at this point is still smaller than the line loss at high current. Compared with low-voltage direct charging 5V5A and high-voltage direct charging 10V2.5A, the latter’s system loss will be better than the former, and the devices used require The required current stress will be lower, the transmission line can also be much thinner, and the cost and safety will be better. Therefore, this kind of fast charging is quickly adopted by domestic mobile phone manufacturers.
Because the voltage of the charger is unconventional 5V, and the power is also much increased, the safety of mobile phone charging is particularly important. In order to prevent their mobile phones from being damaged, domestic mobile phone manufacturers have set up their own handshake protocols, such as Huawei’s SCP, vivo’s Flash-Charge, O PPO’s VOOC3, etc., Xiaomi also adopts a similar mode, but it is not named after its fast charging method.
The emergence of private protocols has indeed improved the security of the entire charging system, and accessories that fail to shake hands will not enter the fast charging mode. But it also brings a disadvantage: it cannot be universal to each other, that is, to achieve fast charging mode for mobile phones of various brands, they must use their own chargers and replace them with other brands of chargers. They cannot enter the fast charging mode, and can only be charged with the most basic 5V2A.
6.Moving forward – the rapid increase of charging power
When QC2.0 first came out in 2014, it is no exaggeration for consumers to describe its charging speed as “surprised”, which also triggered a competition for the charging speed of mobile phones in the Android camp.
In a few years, the power of the charger has risen from 18W to 30W, 45W, 65W, and even at present Rise to 120W. The charging time has also been reduced from the original 90min to 60min, then to 30min, and then to 15min. In the past, charging for 5 minutes, 2 hours of calls became 5 minutes of charging, 2 hours of black, 5 minutes of charging, and 5 hours of entertainment.
At present, the 120W charger, which is full of a battery with a total capacity of 4000mAH, only takes 15min to charge half of it, and only takes 5min. This is undoubtedly very attractive to business people and game enthusiasts who use mobile phones frequently. When traveling, it only needs to charge for 5min to charge 50%, meeting the needs of more than half a day, will be the best support for high-end business people who cherish time like gold.
At present, high-power charging systems basically adopt the mode of high-voltage direct charging. However, in order to increase the power, the charge pump was processed in parallel and the battery was treated in series. For example, the current 120W mobile phone charging system adopts two or three parallel charge pumps on the mobile phone end, and two 6C 2000mAH batteries are connected in series.
The charger outputs 20V6A of power to the mobile phone. After the charge pump, it is converted to 10V12A, and then divided into two batteries. Each battery bears a charging power of 5V12A, as shown in Figure 1.
7.Miniaturization of GaN materials and the clever application of peak power
Mobile phone charger is a frequently used electronic accessory, so consumers want it to have a small size and be easy to carry. However, the power of the charger is gradually increasing. Under the same conditions, the power and volume are proportional.
Therefore, driven by the market, various charger manufacturers are researching small-shaped chargers. To reduce the volume of the charger, there are two common ways: – to improve the efficiency of the charger; the second is to reduce the volume of the internal components of the charger. At this time, some high-end power devices, such as CoolMOS and GaN, began to be applied.
Such devices have low losses and also support higher frequencies. CoolMOS can support frequencies of about 200KHz, while GaN devices can support up to 500KHz or even 1 The switching frequency of MHz can greatly reduce the volume of the product.
With the power supply of such devices, the 65W charger is equivalent to the previous 30W, which greatly meets the needs of consumers for portability. Is there any other way besides relying on the technical improvement of the power supply to reduce the size? The wise manufacturer has come up with an excellent solution in terms of product application.
Most people’s demand for charging speed is reflected in the hope that they can charge part of the power in a short time to meet the emergency needs. For example, you are going on a business trip now, but you find that your mobile phone is out of power. At this time, you hope to charge more than 25% within 5 minutes to meet your needs for temporary business trips.
Based on this, the manufacturer put forward the concept of peak power, such as a 65W mobile phone charger, which can quickly charge 27% of the power within 5 minutes of connection. After that, the mobile phone and the charger will communicate and reduce the power to 35W (approximate value) through the comprehensive evaluation of various conditions such as timing and temperature. ) to charge.
One of the advantages of this is that because it is instantaneous high power, the power of the product will decrease before it reaches the highest point. Compared with long-term full-power charging, the temperature rise of the charger will be much lower.
In this way, the volume of the whole product will be comparable to that of a 35W charger, but it can also enjoy a short-term high-power charging. It is a very ingenious application. At present, Huawei, vivo, OPPO and Xiaomi all adopt such a design on high-end flagship models. Such products are generally marked with the word Max behind the power on the product nameplate.
8.Qualcomm unwilling to fall behind
After 2017, although Qualcomm’s QC3.0 is still widely used, high-end models have begun to use high-voltage direct charging or PD protocol. The position of Qualcomm’s fast charging big brother is gradually not guaranteed. Although in 2016, Qualcomm has strongly launched QC4.0, which has also pulled the typical power to 2 7W, but mobile phone manufacturers don’t seem to be cold.
Only a few manufacturers such as Hammer, Nubia, etc. adopt it, which looks cowardly. QC4.0 itself is compatible with PD. More people think that it just adds some Qualcomm customized things on the basis of PD. As mentioned above, foreign mobile phone manufacturers are more willing to adopt the more influential PD protocol, while domestic mobile phone manufacturers are reluctant to change to the Type C interface.
At the same time, they think that direct charging is more advantageous and begin to switch to direct charging of customized private protocols. As the world’s largest mobile phone solution provider, Qualcomm is obviously unwilling to lag behind, so it launched QC3+ and QC5 in 2020 to compete with the middle and high-end markets.
Many people will definitely wonder why Qualcomm already has QC4.0 and returns another QC3+. In fact, QC3+ is a fast charging protocol with Chinese characteristics. In fact, it is a combination of Q3.0 and high-voltage direct charging. As mentioned earlier, in order to be compatible with the old charging head and charging cable, Chinese mobile phone manufacturers did not immediately switch to the Type C interface at the charger end, but still used the early USBA. QC3+ is the traditional USBA’s D+, D- to shake hands, but compared with QC3.0, it The step is increased from the original 200mV to 20mV, so that direct charging can be achieved.
Compared with QC4.0 or PD, its protocol is relatively simple. At present, the packaging of SOT23-6 can be installed. The chip manufacturers Yingji Core and Weiyu have corresponding chips. In this case, relatively For the QC3.0 chip, the cost increase is very small, but it can achieve direct charging. The earliest chipsets that Qualcomm supported QC3+ were Snapdragon 765 and 765G.
Now the 6 series has begun to be supported (Note: Qualcomm’s high-end is the 8 series, which also supports QC3+). A new protocol is not first launched on the highest-end model, but compatible with high-end models, which is Qualcomm’s fast charging. For the first time in history, it can be seen that Qualcomm hopes to increase its market share with this most cost-effective charging scheme.
Let’s talk about QC5. The official claim of QC5 supports 100W+ power and dual charging technology (dual battery charging). In fact, it is a protocol similar to the 120W charging principle shown in the figure above, which is used for super-power charging of mobile phones.
Qualcomm strongly launched the “Purple and Blue Double Sword” in 2020 — QC3+ and QC5, hoping to return to the throne of the hegemon of mobile phone fast charging.
9 .The development of fast wireless chargers
The application of wireless charging of mobile phones has been tried by NOKIA, Plam and other manufacturers as early as the early 10s. Wireless charging has a very good experience, but due to the charging speed and cost, it was not popular at that time. Until the release of Apple’s iPhone8 series that supports wireless charging in 2017, it once again drove the development of the industry.
As early as 2008, the WPC (Wireless Power Consortium) Association began to formulate wireless charging standards. At present, wireless charging of mobile phones basically follows the Qi protocol under WPC, which brings great convenience to consumers: as long as it complies with the Qi protocol The cable charger can charge your mobile phone. At present, more and more mobile phone brands are releasing mobile phones that support wireless charging, such as Apple, Meizu, Huawei, OPPO, Xiaomi, Samsung, etc.
However, at present, the Qi protocol only defines the maximum power of 15W (EPP). Obviously, this charging power is difficult to satisfy users. In order to get a better experience, mobile phone manufacturers are gradually improving the charging power of wireless charging.
30W has become a mainstream, and 65W wireless charging has also begun to appear. Because it has exceeded the scope of EPP, each family can only carry its own private protocol, so only the standard wireless charger can support more than 15W of charging power; when equipped with non-own chargers, the maximum charging power can only be achieved at 15W, usually about 10W.
Based on this, WPC is also considering increasing the maximum power defined by the Qi protocol. In addition, Qualcomm also saw the development momentum of wireless charging and launched the QC-Wireless certification, which considers the ability of wireless charging with QC chargers and certifies the compatibility of the QC protocol of the wireless charging input terminal.
Because at present, many mobile phones are still equipped with QC chargers, and there are also a lot of stocks on the market. If the QC charger can be directly used to supply power to the wireless charging transmitter, then wireless charging does not need to be equipped with a separate adapter, which is also a kind of energy saving.
However, random matching may cause danger. Qualcomm launched QC-Wireless certification at this time, which is also a guarantee for wireless charging that supports QC.
10.Apples that are not fast or slow
As an Apple outside the Android camp, mobile phones have always been at the forefront of high technology and innovation, but in terms of charging, they have been slow. From the beginning to the end, the charging head is equipped with a 5V1A charging head as standard, to this day.
Some careful consumers also found that the iPhone6 Plus released in 2014 can support about 5V2A charging, and the iPhone 8 series released in 2017 can support up to 9V2A PD charging. In 2020, Apple will upgrade the power of the charging head.
At 20W, this is the maximum power of the iPhone charger at present. Compared with the 65W or even 120W charging head in the Android camp, the power is indeed difficult to compare.
Whether Apple chooses to be conservative or prepare to thick and thin on the basis of safety, we don’t know, and we don’t have to speculate. We are more looking forward to the emergence of new technologies from Apple.