Understanding Adaptive Fast Charging (AFC) Technology

Adaptive Fast Charging (AFC)

Definition:

Adaptive Fast Charging (AFC) is a proprietary fast – charging technology developed by Samsung for its Galaxy smartphones, tablets, and other devices. It is a voltage – adaptive protocol that dynamically adjusts charging voltage and current based on the device’s battery state (SoC), temperature, and power needs, while being backward – compatible with Qualcomm Quick Charge 2.0 (QC 2.0) and later integrated into USB Power Delivery (PD) 3.0 with Programmable Power Supply (PPS) for broader cross – device support. It is designed to balance charging speed, battery safety, and longevity, typically delivering up to 50% charge in around 30 minutes for compatible devices.

Core Technical Principles & Specifications

1. Voltage – Current Profiles & Power Evolution

AFC uses a multi – voltage output architecture to enable fast charging, with power levels evolving over generations:

Generation/Device	Key Voltage – Current Profiles	Max Power	Typical Use Case
Early (Galaxy S6/Note 4)	5V/2A (10W), 9V/1.67A (15W), 9V/2A (18W)	18W	Baseline fast charging for mid – range devices
Mid – term (S10 5G)	9V/2.78A, 10V/2.5A	25W	Enhanced speed for flagship devices
Current (Note10+/S20+)	15V/3A, 20V/2.25A (via PD PPS)	45W	Ultra – fast charging for premium flagships

It operates on the Constant Current – Constant Voltage (CC – CV) charging principle. During the CC phase, AFC supplies a high current to rapidly boost the battery’s charge level. When the battery voltage approaches its fully charged threshold, it switches to the CV phase to prevent overcharging and ensure safe completion of the charging process.

2. Adaptive Control Mechanisms

AFC’s core “adaptivity” stems from real – time monitoring and dynamic adjustments:

Battery State of Charge (SoC): As the battery fills up, the charging current is gradually reduced to avoid stressing the cells.
Thermal Regulation: If the battery or charging circuit temperature exceeds a safe threshold (usually 40–45°C), AFC lowers the charging power to prevent overheating and degradation.
Device Power Demand: It prioritizes power for active tasks (like gaming or video streaming) while charging, ensuring smooth device operation without sacrificing charging efficiency.
Charger/ Cable Compatibility: AFC negotiates with the charger and cable to detect their maximum power delivery capability, avoiding unsafe power draws.

3. Protocol Compatibility

QC 2.0 Compatibility: AFC uses the same voltage negotiation signaling as QC 2.0, allowing AFC – enabled devices to charge with QC 2.0 chargers and vice versa.
PD 3.0 PPS Integration: Modern AFC implementations support PD 3.0 with PPS, enabling variable voltage/current output (3.3–21V, adjustable in 20mV steps) for compatibility with non – Samsung devices that adhere to the PD standard.
Backward Compatibility: Works with standard USB chargers (5V/1A or 5V/2A) by falling back to regular charging speeds when fast – charging conditions are not met.

How AFC Works (End – to – End Workflow)

Negotiation Phase: When an AFC – enabled device is connected to an AFC/QC 2.0/PD PPS charger, the device and charger exchange signals over the USB data lines to identify supported voltage/current profiles and confirm cable capacity.
Fast Charging (CC Phase): The charger delivers the maximum safe voltage and current (e.g., 9V/2A for 18W) based on the device’s initial battery state and temperature. This phase rapidly charges the battery to ~70–80% SoC.
Adaptive Adjustment: The device’s battery management system (BMS) continuously monitors temperature, voltage, and SoC. If the battery heats up or nears full charge, the BMS instructs the charger to reduce current or switch to a lower voltage.
Trickle Charging (CV Phase): When the battery reaches ~80–90% SoC, the charger switches to constant voltage mode, gradually reducing current to prevent overcharging and ensure the battery is fully charged safely.
Completion: Charging stops automatically when the battery reaches 100% SoC, with periodic top – ups to maintain full charge (if the device remains connected).

Key Benefits

Rapid Charging Speed: Delivers up to 50% charge in ~30 minutes for most compatible devices, significantly faster than standard 5V/1A chargers (70–75% faster).
Dynamic Safety Controls: Real – time monitoring of temperature and battery health prevents overheating, overvoltage, overcurrent, and short – circuits, extending battery lifespan.
Broad Compatibility: Works with AFC – optimized chargers, QC 2.0 chargers, and modern PD PPS chargers, reducing reliance on proprietary accessories.
Seamless User Experience: Charges the device while powering active applications (calls, streaming, gaming) without significant performance throttling.

Limitations & Challenges

Power Cap Variability: Early AFC implementations are limited to 18W, while newer flagships support 25W–45W, but this requires compatible chargers and cables (e.g., USB – C with 5A capacity for 45W).
Thermal Throttling: In hot environments or during heavy device usage, AFC reduces charging power to manage temperature, which slows down charging speeds.
Charger Dependency: To achieve maximum AFC speeds, users need AFC – certified chargers; non – certified chargers may only deliver standard or reduced fast – charging speeds.
Battery Aging Trade – Off: While AFC includes safety features, frequent fast charging (even with adaptive controls) can accelerate battery capacity loss compared to slow charging over long – term use.

Comparison with Other Fast – Charging Protocols

Feature	Adaptive Fast Charging (AFC)	Qualcomm Quick Charge 4+	USB PD 3.0 PPS	Apple Fast Charging
Developer	Samsung	Qualcomm	USB – IF	Apple
Max Power (Mobile)	45W (flagships)	100W	100W	27W (iPhone 15 series)
Voltage Range	5V, 9V, 10V, 15V, 20V (via PD)	3.3–20V (PPS)	3.3–21V (20mV steps)	9V (PD – based)
Key Compatibility	Samsung Galaxy, QC 2.0 devices	Snapdragon – powered devices	Universal (laptops, phones, tablets)	iPhones, iPads
Safety Features	Thermal monitoring, adaptive current	Dual – core protection, thermal balancing	PPS voltage/current adjustment	MFi certification, thermal controls

Best Practices for AFC Deployment

Battery Health Settings: Enable Samsung’s “Protect Battery” feature (limits charging to 85% SoC) to reduce long – term battery degradation if fast full charging is not required.

Use Certified Chargers: Choose Samsung – branded AFC chargers or third – party chargers certified for AFC/QC 2.0/PD PPS to ensure maximum speed and safety.

High – Quality Cables: Use USB – C cables rated for 3A (for 18–25W) or 5A (for 45W) to avoid voltage drops and power limitations.

Cool Charging Environment: Charge the device in a well – ventilated area, avoid covering it with blankets or cases that trap heat, and refrain from heavy usage during charging.