Which brand excels in fast charging for mobile phones?
Since 2018, an increasing number of smartphones have achieved a fast charging power exceeding 20W. In just a few years, some manufacturers have claimed to have implemented 240W fast charging technology. What is the principle behind such efficient fast charging technology? And what are the differences between various fast charging technologies for mobile phones?
Three types of fast charging technologies, each with its own advantages and disadvantages
To understand fast charging, we first need to know the battery structure of a mobile phone.
The core of a smartphone battery is lithium-ion. When the phone is being charged, lithium ions from the positive electrode move through the insulating separator to the negative electrode and are stored in a sponge-like graphite material. When all the lithium ions from the positive electrode have moved to the negative electrode, it means the battery is fully charged.
Currently, the battery capacity of a typical smartphone is generally above 3000mAh, and it takes 3-4 hours to fully charge using a regular 5V/1A charger. However, fast charging technology can compress the time to about 1 hour, greatly improving efficiency.
Based on the formula for electric power in physics, P (power) = U (voltage) × I (current), we can deduce three principles of fast charging: high voltage with low current, high current with low voltage, and high voltage with high current.
High Voltage, Low Current: The charging process of a typical mobile phone involves first reducing the 220V voltage to a charger voltage of 5V, which is then further reduced to the battery voltage of 4.2V. During the entire charging process, if the charger voltage is increased to 9V, the charging time can be compressed by 50%. However, this has the disadvantage of causing the charger and phone to heat up, and increasing the damage to the battery.
High current and low voltage: By adding multiple parallel circuits, the total current value can be increased. After the circuits are shunted in parallel, each module bears a small sub-power, which can effectively control the heat dissipation of the circuit and prevent the phone from overheating. However, the current cannot be infinitely increased. High-current charging still generates heat. If the heating rate exceeds the heat dissipation rate and there is no protection mechanism, the battery temperature will continue to rise, leading to reduced lifespan or even explosion. Therefore, almost all chargers and products themselves limit the maximum current.
High voltage and high current: Simultaneously increasing voltage and current is undoubtedly the most efficient way to speed up charging, but higher voltage can generate more heat, leading to significant issues such as circuit heat loss and shortened battery life.
The three fast charging methods each have their own advantages and disadvantages. To truly achieve fast charging without compromising battery life, technological breakthroughs are still needed.
OPPO VOOC Flash Charge: Precisely controlling current with chips
VOOC flash charging is a fast charging technology independently developed by OPPO. This technology incorporates an MCU smart chip into the adapter, enabling precise control over current, thus achieving open voltage loop and segmented constant current.
For example, a mobile phone is like a car. With ordinary charging, its power is only 1.2L, which can only achieve a slow start. However, with the VOOC flash charging technology, the power can be increased to 3L by opening the voltage loop. Just a light press on the accelerator can make it move forward quickly. The segmented constant current is similar to the car starting process. When starting, it shifts to high gear for quick startup, changes to medium gear in the middle stage for efficient operation, and finally shifts to low gear for stable and full charging.
It's worth mentioning that VOOC Flash Charge has pioneered a comprehensive five-layer protection system, spanning from the adapter to the interface and deep into the phone's internals. This system utilizes an MCU chip to manage the heat-generating voltage-reducing circuit, effectively addressing the heat issue associated with fast charging in smartphones.
Qualcomm Quick Charge 5.0: 5 minutes from 0% to 50%
In 2020, Qualcomm released the QC 5.0 fast charging protocol, marking its official entry into the era of three-digit power.
Qualcomm QC 5.0 upgrades the INOV algorithm to 4.0, claiming to be the first fast charging platform in smartphones to commercially offer charging power above 100W. It supports 100W+ super fast charging, with a 5-minute charge from 0 to 50%; it also supports multi-charging technology, with voltage adjustments ranging from 3.3V to 20V, making the Qualcomm QC charging protocol more aligned with USB-PD charging standards and characteristics.
In addition, Qualcomm's Battery Saver battery health management and the new Qualcomm adapter power intelligent recognition technology not only enhance charging efficiency but also significantly improve charging safety and battery life. According to Qualcomm's data, charging efficiency is increased by 70% compared to QC 4.0 and 10 times compared to QC1.0, while the charging temperature is reduced by 10℃.
Huawei SCP fast charging protocol: Our own is fast
In the realm of fast charging, domestic smartphone company Huawei is equally competitive. In 2016, Huawei introduced the SCP protocol, featuring a specification of 4.5V/5A or 5V/4.5A, which translates to a power output of 22.5W. This technology was first implemented in the Mate 9, adopting a "low voltage, high current" approach akin to that of OPPO. The advantage lies in increasing power output while reducing heat generation. Building upon this protocol, Huawei further incorporated charge pump technology, reducing the charging voltage to approximately 5V while simultaneously increasing the current from 4A to 8A, achieving a super fast charging speed of 40W. Additionally, the Huawei Mate X also showcased a super fast charging capability of 65W, which follows the same dual-battery charging approach as OPPO. However, with a twist, each battery utilizes electromagnetic isolation to achieve an actual charging speed of 60W.
Xiaomi Super Charge Turbo: Two chips, higher efficiency
Xiaomi's fast charging technology is called Super Charge Turbo, and the highest wired charging power supported is 120W for the Xiaomi 12 Pro. Xiaomi Super Charge Turbo utilizes two P1 chips, internally employing three different voltage-tolerant FLY capacitors, each requiring an independent short-circuit protection circuit. It achieves bidirectional conduction through three conversion modes: 1:1, 2:1, and 4:1. The forward 1:1 mode enhances charging efficiency when the screen is on; the forward 2:1 mode is compatible with a wider range of chargers; and the forward 4:1 mode supports 120W Super Charge Turbo. The reverse 1:2 and 1:4 modes support up to 30W of reverse charging, directly delivering high current to the battery. The resonant topology efficiency is as high as 97.5%, while the non-resonant topology efficiency is 96.8%, with a linear decrease in heat loss by 30%.
Moreover, Xiaomi Super Charge Turbo offers users two modes: low temperature and fast charging, enriching everyone's charging options.
