Does Apple Reject PPS? In-Depth Analysis of Why the Dynamic Fast Charging of iPhone 17 Is More Powerful
For years, "charging speed" has been an unspoken pain for iPhone users and a source of pride for the Android camp, which often boasts about its "far - ahead" technology. While an Android phone next to you can "recharge" in just twenty minutes at a café and be ready for another half - day of use, iPhone users can only anxiously watch the battery percentage creep up at a snail's pace.
After all, in the fast - paced modern life, the sense of security brought by a "flash charge" in the last ten minutes before going out is irreplaceable by any fancy features.
However, at the September 10th press conference, the "40W Dynamic Power Adapter (up to 60W)" that quietly debuted alongside the iPhone 17 series seems to signal the end of this long - awaited wait. Apple's press release states that the new iPhone 17 can charge up to 50% in just 20 minutes.
The key to this leap is not simply increasing the power (after all, Apple's 140W charger was launched in 2021), but an unassuming protocol abbreviation on the charger image: AVS (Adjustable Voltage Supply).
More precisely, it's SPR AVS (Standard Power Range Adjustable Voltage Supply).
Image | Apple's official website
SPR AVS is a new protocol that was only officially implemented in the USB PD 3.2 standard proposed at the end of 2024.
While Android manufacturers generally embrace the well - established PPS protocol, why has Apple chosen a completely different open - technology path?
Behind this is a trade - off between efficiency, safety, and the future ecosystem. It also marks an impending radical change in the fast - charging technology of the entire consumer electronics field.
I. The "Heating Curse" of Fast Charging
To understand Apple's choice, we first need to understand the same physical problem faced by all fast - charging phones: heating.
For a long time, Apple devices, including the iPhone 16, have relied on the "fixed - voltage charging + in - device secondary voltage reduction" model for their fast - charging solutions.
We can use a common analogy: the charger is like a reservoir at a high place, releasing water to the phone at a fixed high "water level" (e.g., 15V voltage). The power management chip (PMIC) inside the phone is like a complex and precise valve and pipe system that needs to reduce the high - pressure water flow step by step and convert it into a low - pressure water flow (e.g., 4.2V) that the battery can "drink."
The problem lies in the "conversion" process. According to the law of conservation of energy, every voltage conversion is not lossless, and some energy is always dissipated in the form of heat. The higher the charging power, the more energy needs to be converted, and the more severe the heating inside the phone. It's like the faster the water flow, the more heat is generated by the friction between the valves and pipes.
More importantly, the lithium - ion battery itself is a heat source during the charging process due to internal electrochemical reactions. When the heat generated by the internal voltage - reduction conversion loss and the heat from the battery's own charging are combined in the small and enclosed space of the phone, the temperature rises rapidly. To protect the battery's chemical activity, extend its lifespan, and ensure user safety, the phone's temperature control system will immediately intervene and force the charging speed to slow down.
— This is the fundamental reason why the "peak fast - charging" of many devices can only last for a few minutes to a dozen minutes, after which the power drops significantly.
For illustration only. Image | ChargerHead.com
Here is a great example: electric vehicle charging. Why do home AC chargers have a power of only a few thousand to a few tens of kilowatts, while public DC high - speed chargers can reach hundreds of kilowatts? The core difference is that DC fast - charging chargers place the bulky and heat - generating AC - DC conversion module outside the vehicle and directly supply power to the battery.
The logic of phone fast - charging is the same: By "outsourcing" the voltage - conversion process, which generates a lot of heat, from the phone to the charger as much as possible, the heating inside the phone is significantly reduced, and the battery can withstand higher charging power for a longer time.
II. The "Overtaking Lane" of the Android Camp: An Imperfect Shortcut
Facing the same problem, Android manufacturers have long had solutions: their ultra - high - speed fast - charging technologies, which can reach up to hundreds of watts, are based on the above - mentioned logic of "the charger does more work, and the phone generates less heat." To implement this logic, the Android camp mainly uses three solutions: proprietary protocols, the PPS protocol, and the UFCS protocol.
a) Proprietary protocols: Developed by each manufacturer, they have the best performance but are criticized for their closed ecosystem and poor compatibility. A 100 - watt charger from brand A may charge a phone from brand B at only a few watts.
b) PPS (Programmable Power Supply) is an optional standard introduced in the USB - PD 3.0 specification. It allows for more precise voltage and current adjustment between the charger and the phone, thereby reducing the voltage - reduction work inside the phone.
c) UFCS (Universal Fast Charging Specification) is a domestic Chinese fast - charging standard with a design concept similar to that of PPS.
Thanks to its openness and good performance, PPS has quickly become the most mainstream public fast - charging protocol in the Android camp. Some relatively open domestic phones can even achieve nearly 100W of PPS fast charging. Since there is a ready - made and widely supported solution, why doesn't Apple just adopt it?
The answer is that Apple has seen through two major "flaws" beneath the shiny surface of the PPS protocol. This is not simply a technical choice but a design limitation left over from history, which fundamentally conflicts with Apple's uncompromising engineering philosophy.
1. Overly Idealistic Precision: The "Pseudo - Science" of 20mV Steps
The PPS protocol stipulates a voltage step of 20mV and a current step of 50mA. This precision looks great on paper, but in the complex and ever - changing real world, it is almost an unattainable skill.
The line loss of an ordinary USB - C data cable can easily exceed 20mV. Coupled with factors such as the voltage ripple of the charger itself, voltage drift at different ambient temperatures, contact resistance at the interface contacts, and even dirt and dust on the interface, the electrical error introduced by each factor may be greater than 20mV.
Trying to control the voltage with a precision of 20mV is like trying to measure the length of a cat with a vernier caliper. No matter how fine the scale is, it's useless.
2. The Bizarre Power Limit: The "Power Cliff" at Low Voltages
This is the most fatal and counter - intuitive design flaw of PPS. It introduces a concept of "maximum power," but this power is not constant at all voltages. The maximum power of PPS is actually a simple product of the maximum current and the maximum voltage, and the limits of the maximum current and maximum voltage take effect simultaneously.
For example, a PPS charger rated at 45W is advertised as 21V/2.15A (21V × 2.15A ~ 45W). When your phone's battery is very low at the beginning of charging (e.g., the battery voltage is 3.6V, and an input voltage of 10.8V, three times the battery voltage, is required), you might expect to get a full - speed power of 10.8V × 4.15A ~ 45W. However, due to the limitations of the PPS protocol, the maximum current the charger can provide is still locked at 2.15A. So, the maximum power you actually get is only 10.8V × 2.15A = 23.22W, and the power is directly halved!
This "high - voltage for high - power" model causes significant power loss and seriously violates the original intention of fast charging, which is to charge the most amount of electricity in the shortest time.
Although the high - voltage and low - current approach is a mature technology route, there is also an important branch of low - voltage and high - current technology in the industry. The design of the PPS protocol is clearly unfriendly to the latter and lacks universality. Since the protocol and standard are biased towards a certain technology route, it is not adopted to solve practical problems.
Actually, the proprietary protocols of some domestic phone manufacturers are also a last - resort measure because it is difficult to implement low - voltage and high - current charging with PPS.
— It is these two core flaws that have ultimately led Apple, which pursues an ultimate and reliable user experience, to abandon PPS. Apple needs a solution that is not just beautiful on paper but full of compromises and uncertainties in practical applications.
Image | WHYLAB
III. SPR AVS: The Next - Generation Charging Standard Endorsed by Apple
Beyond PPS, Apple has chosen a better solution: SPR AVS (Standard Power Range Adjustable Voltage Supply).
AVS didn't come out of nowhere. It was first introduced in the PD 3.1 EPR (Extended Power Range) specification designed for high - power devices such as laptops and can provide a maximum power of 48V 5A = 240W.
Apple's own 16 - inch MacBook Pro was the first mainstream commercial product to use AVS. The SPR AVS supported by the iPhone 17 is an advanced voltage - regulation technology that the USB - IF Association has officially extended to the standard power range (below 100W) in the latest PD 3.2 specification.
Image | Sugar Factory
Compared with PPS, AVS has a more practical and efficient design philosophy and precisely solves all the historical problems of PPS.
Meanwhile, since this is an extension of the standard, SDC (Software - Defined Charger) products can immediately support the new protocol through protocol upgrades, allowing existing devices to "transform" and support the new standard.
1. Practical Precision: 100mV Steps
AVS abandons the unrealistic 20mV step and adopts a 100mV voltage step instead. This precision is "just right": it is fine enough to make the voltage output by the charger highly match the current voltage required by the battery (usually in combination with a charge - pump chip inside the phone for 2:1 or 3:1 voltage reduction), thereby minimizing the heating inside the device. It is also wide enough to easily withstand electrical interference in the real world, such as cable loss and voltage ripple, ensuring the stability of voltage adjustment and the robustness of the system. This is an embodiment of engineering wisdom: only pursue effective precision, not ineffective precision.
2. True Constant - Current Output: Farewell to the "Power Cliff"
AVS completely abandons the awkward "constant - power limit" model of PPS. Its working mode returns to a more intuitive mode in electrical engineering, similar to the traditional fixed - voltage levels, where the voltage and current limits are independently controlled.
This means that the charger can be defined as "always providing a maximum of XX amperes of current within a certain voltage range." As a result, even at a lower voltage, the charger can continuously output the set maximum current. This is great news for batteries that require high - current direct charging and efficient charge - pump architectures. It ensures that throughout the charging cycle, regardless of the technology route used, high - power input can be maintained efficiently, completely solving the power - loss problem of PPS.
3. An Open Standard: Apple's Ecosystem Philosophy
Like ifanr, Apple is a member of the USB - IF Association, the institution that formulates the PD protocol. In promoting the AVS standard, Apple has once again demonstrated its ability to define and lead industry standards. Instead of building a wall with a proprietary protocol, Apple uses its huge market influence to push a more advanced open standard into the mainstream.
Behind this is Apple's consistent ecosystem philosophy: by being the "first to try" with its star products, it promotes the entire industry to adopt better open standards.
This not only avoids the ecological fragmentation caused by proprietary protocols but also clears the way for third - party accessory manufacturers. They can manufacture efficient fast - charging accessories that are perfectly compatible with iPhones without any proprietary chips or licensing fees. An open, unified, and high - performance standard will ultimately benefit all consumers and the entire industry chain.
Looking back at Apple's pioneering and significant decisions in consumer electronics technology, from abandoning the floppy disk drive to embracing wireless networks and then fully transitioning to the USB - C interface, each decision was accompanied by controversy and doubt, but ultimately led the industry to change with its forward - looking vision.
The logic behind Apple's choice of the SPR AVS technology route for the iPhone 17 is the same. This not only enables the iPhone's charging speed to catch up with that of Android phones but also, more importantly, Apple is setting a new and better fast - charging benchmark for the entire industry in terms of technology and logic.
It is foreseeable that with Apple's strong entry and the rapid follow - up of Sugar Factory's AI - powered SDC, SPR AVS will quickly shed its "obscure" status. It is very likely to become the fast - charging technology benchmark for all mainstream smart devices in the next few years, leading the entire industry to bid farewell to the current chaotic protocol disputes and move towards a smarter, more efficient, and cooler fast - charging era.