Understanding Power Delivery: USB PD, QC, and Beyond

## The Fast-Charging Alphabet Soup

Walk into any electronics store and you'll see cables and chargers branded with USB PD, QC 3.0, QC 5.0, AFC, VOOC, SuperVOOC, Warp, and dozens more. All of them promise fast charging, but they work in very different ways and are often incompatible with each other.

## USB Power Delivery (USB PD)

**Who uses it**: Apple, Google, Samsung, Dell, Lenovo, HP — essentially the entire industry.

USB PD is the open standard developed by the USB Implementers Forum. It is the only fast-charging protocol supported by USB-C on iPhones (iPhone 8 and later), all modern MacBooks, iPad Pro, and most Android flagships.

| PD Version | Max Power | Key Feature |
|---|---|---|
| USB PD 2.0 | 100W | PPS (programmable voltage) |
| USB PD 3.0 | 100W | Refined PPS, fast phone charging |
| USB PD 3.1 | 240W | EPR: 28V / 36V / 48V rails |

**Cable requirement**: Up to 60W, any USB-C cable works. Above 60W, you need an **e-marked** cable with a chip that tells the charger it is rated for 5A. Above 100W (PD 3.1 EPR) you need an EPR-rated cable with 50V insulation.

## Qualcomm Quick Charge (QC)

**Who uses it**: Qualcomm-powered Android phones — Snapdragon 700 / 800 series.

Quick Charge works over both USB-A and USB-C. It keeps voltage at 5V but raises current, or raises voltage in fixed steps (9V, 12V, 20V on QC 3.0). QC 5.0 adds 100W support.

| QC Version | Max Power | Compatibility |
|---|---|---|
| QC 2.0 | 18W | Backward compatible |
| QC 3.0 | 18W | INOV (0.2V steps) |
| QC 4.0+ | 100W | Compatible with USB PD |
| QC 5.0 | 100W+ | Multi-cell charging |

**Important**: QC 4.0 and later are backward-compatible with USB PD. A PD charger can fast-charge a QC 4.0 phone and vice versa.

## Samsung Adaptive Fast Charging (AFC)

**Who uses it**: Mid-range Samsung Galaxy devices.

AFC is Samsung's proprietary protocol over USB-A at 9V/1.67A (15W). On flagship Galaxy S and Note devices, Samsung uses USB PD with PPS.

| Device Generation | Protocol | Max Speed |
|---|---|---|
| Galaxy S23 (USB-A charger included) | AFC | 25W |
| Galaxy S24 series (no charger included) | USB PD PPS | 25-45W |

## Apple Fast Charge

Apple does not use Quick Charge. iPhones and iPads use USB PD exclusively.

- iPhone 15 and later: USB-C, USB PD (up to 30W on Pro)
- iPhone 8-14: Lightning to USB-C cable + USB PD charger (up to 20W)
- MacBook: USB PD up to 140W (M-series MacBook Pros)

## Choosing the Right Charger and Cable

1. **Check your device's max wattage** — in spec sheet or Settings > Battery
2. **Match or exceed that wattage** — a 100W charger safely charges a 30W phone
3. **Use PD for universal compatibility** — it works across phones, tablets, laptops
4. **Cable rating matters** — a 60W cable limits a 100W charger to 60W
5. **GaN chargers** run cooler and smaller than silicon; worth the slight premium

## Quick Decision Guide

| Device | Best Protocol | Min Charger |
|---|---|---|
| iPhone 15+ | USB PD | 20W USB-C |
| MacBook Pro | USB PD 3.1 | 96-140W |
| Galaxy S24 Ultra | USB PD PPS | 45W |
| Pixel 9 | USB PD PPS | 30W |
| Budget Android | May use QC or AFC | Varies |