There are more and more mobile phones that support fast charging, but this is mainly divided into two major solutions:
1. High voltage, low current and fast charge
2. Low voltage, high current, fast charge
The first solution is commonly used by Qualcomm, QuickCharge, MediaTek PEP, Huawei FCP, etc., while the second has OPPO's VOOC and Huawei's SuperCharge, while the USB-PD protocol includes both high-voltage and low-voltage. The just-concluded USB IF WorkSHOP once again took a lot of space to introduce PD, and the future mobile phone's PD fast charge will have a lot of market space.
As is well known, P = UI, increasing the charging power is nothing more than increasing the current or voltage. However, neither voltage nor current can be increased freely without restriction, because both will bring obvious heat to the mobile phone.
The first type of high-voltage low-current fast charge is to increase the charging voltage (7-20V) during the charging process to improve the charging power. The charging process of the fast-charge mobile phone is generally to first reduce the 220V voltage to 5V through the charging head and internal circuit of the mobile phone. Then 5V voltage is reduced to 4.2V and the power is delivered to the battery. The whole step-down process will generate heat energy, while the high-voltage low-current fast charge will increase the 5V charging head output voltage to 7-20V, and then reduce inside mobile phone voltage to 4.2V. The whole charging process will produce more body. Heat, chargers, and mobile phones all have obvious heat, which is not conducive to the improvement of charging efficiency.
The second type of low-voltage high-current fast charge is to increase the current when the voltage is constant (4.5V-5V). Generally, the shunt is used to divide the current. Under constant voltage, the voltage shared by each circuit after parallel shunting is performed. The smaller, the same processing in the phone, the less pressure each circuit will bear. For example, VOOC flash charging enhances the carrying capacity of large currents by increasing the number of lines of the charging cable / the number of USB port contacts. The principle of Huawei SuperCharge fast charging is similar. Avoid high heat generated by the "high pressure to low pressure" conversion inside the fuselage.
Advantages of the PD Fast Charge Protocol
For the advantages of the PD protocol, the author borrows a description from Baidu: PD is Power Delivery, focusing on two or more devices, or even a power transmission process based on the USB interface of the smart grid. The power transmission can be bidirectional, even It is networked and can have a system-level power supply strategy. QC is Quick Charge only pays attention to the problem of fast charging. The power transmission is unidirectional, does not have the ability of networking, and does not support other functions besides power supply.
USB PD3.0: Covers both high voltage, low current, low voltage and high current
The USBPD3.0 specification has a voltage output range of 3.0V to 21V and a step-and-step voltage of 20mV.
This includes the low voltage / high voltage two parts, and the current PD protocol current data seems to be (1.5A, 2A, 3A and 5A), this USBPD3.0 will be able to achieve high voltage / low current, low voltage / High current two fast charging schemes, plus voltage amplitude stepping is 20mV, the overall idea combines high voltage and low current like Qualcomm QC fast charging (also guarantees charging efficiency by step amplitude modulation voltage) and low voltage and high current of VOOC flash charging Kind of program.
In short, USBPD3.0 absorbs the essence of the current fast charge, re-integrates into a big and full; fast charge program, in order to achieve fast charging of mobile phones, all mobile phones that support fast charge can pass a support PPS The technology's charger enables fast charging. Go back to that era when all the phones are not afraid. At present, USBPPS has reached a consensus with the Tel Lab of the Ministry of Industry and Information Technology of China. At the same time, Google emphasizes in the latest Android7.0 OEM specification: fast-charge technology must support USBPD.
Difference between PD2.0 and PD3.0
The change of PD3.0 relative to PD2.0 is mainly three aspects:
First, more detailed description of the built-in battery characteristics of the device has been added.
Second, function of device software and hardware version identification and software update through PD communication is added.
Third, digital certificate and digital signature function have been added.
The first change can make both sides of the connection more aware of each other's power supply status, thus coordinating the power supply strategies of both parties. It is extremely important to build a low-voltage intelligent power supply network using the USBPD protocol. The power supply topology can be coordinated under various power conditions. For example, the emergency power supply and power disposal strategy when the power grid is out of power, the power supply strategy of the grid power supply and the home solar power generation device, and the reverse power supply strategy to the power grid. Can make Power more SMART.
The second software upgrade function can make the compatibility of the device more excellent. All TYPE-C manufacturers can release their latest firmware version to the Internet, so that they can use the PC and mobile phones, etc. The peripheral accessories were updated in a timely manner. Just as Microsoft's win10 system can solve hardware driver problems online in real time. The internal firmware of the USBPD device is also part of the traditional hardware driver resources.
The third point of the digital certificate function is estimated to be the most important feature of this upgrade. It is possible for all TYPE-C products to obtain a digital certificate issued by the USB-IF organization using a private key in order to be unimpeded. Certificate-free products may not be accepted by other manufacturers' TYPE-C products. This feature has a very positive meaning to avoid unqualified TYPE-C interface devices, which can damage normal devices due to quality issues. In the enterprise information security application, the security certificate can also be issued by the enterprise itself, so that the non-enterprise USB device cannot be accessed, which is more secure than the existing USB encryption technology, because before the security certification is completed through the CC line, The storage medium is physically isolated from the system.
Finally, PD2.0 is a subset of PD3.0 from the agreement, that is, PD3.0 is naturally compatible with pd2.0. Secondly, from the hardware level, PD3.0 is fully compatible with the link layer and physical layer of PD2.0. That is to say, when the product is upgraded, no hardware changes are required, and only online software upgrade is required. Therefore, both from the perspective of the protocol itself and from the perspective of market strategy, it is possible to actively develop USBPD2.0 products. When necessary, upgrade the firmware to be compatible with PD3.0.
What will be brought along the popularity of USB PD3.0?
There is no doubt that the popularity of USBPD3.0 is a good thing for users. Nowadays, all kinds of fast charging technologies are developed by manufacturers themselves. The conditions for fast charging are harsh, and mobile phones, chargers and data cables are in one-to-one correspondence. Popularity of USBPD3.0 can get rid of this dilemma, all different brands of mobile phones, different brands of fast charge chargers and data lines will be universal, no longer need to find a full charger and data cable.