Fast-Charge Protocols Your Tester Must Cover — and Where Lines Slip

A charger is only as honest as the protocol it speaks. Your tester has to recognize every protocol your customer's device will ask for — from USB PD all the way to the proprietary handshakes vendors won't publish. Miss one and the charger "charges," but slower than the box promises. That is the complaint that survives a spec-sheet review and still costs you the return.

This is a map, not a manual. The numbers below are the public specifications; the proprietary ones are stated as the classes vendors ship. Use it to check what your tester actually exercises before you trust a "pass."

Start with the public standards

USB Power Delivery (PD). The baseline everyone expects. Within PD there are two power ranges:

• Standard Power Range (SPR): fixed voltages 5V, 9V, 15V, 20V at up to 5A — that is the familiar 100W ceiling (20V × 5A).
• Extended Power Range (EPR), added in PD 3.1 (2021): 28V, 36V and 48V at 5A — up to 240W. EPR requires an EPR-rated cable whose e-marker declares 50V/5A; without it the port falls back to 100W. Inside EPR, AVS (Adjustable Voltage Supply) lets a device fine-tune anywhere from 15V to 48V in 100mV steps.

PPS (Programmable Power Supply) is a sub-mode of USB PD, not a separate standard: it varies voltage from 3.3V to 21V in fine 20mV steps, which is why Samsung Galaxy and Google Pixel charge efficiently on PD-PPS. A tester that only checks fixed PD voltages misses PPS entirely.

Qualcomm Quick Charge

Still the most common non-PD scheme on the bench:

• QC 2.0: fixed 5V / 9V / 12V at 3A — about 18W.
• QC 3.0: 3.6V–20V in 200mV steps, roughly 18–24W.
• QC 4 / 4+: adds USB PD compatibility, around 27W.
• QC 5: up to 100W+, built on USB PD PPS, with Qualcomm quoting 0–50% in about five minutes. Backward compatible with QC 2.0 through 4+.

The proprietary jungle

This is where lines slip, because none of it is in the PD book and each vendor's handshake is its own. Your tester must recognize the actual protocol the device requests:

• VOOC / SuperVOOC (OPPO, OnePlus, realme): low-voltage, high-current design on a proprietary cable — VOOC at 20W, SuperVOOC climbing through 50W, 65W, 80W, 100W and beyond. Without the vendor cable and handshake, a port falls back to a trickle.
• Huawei SCP / FCP: SCP is low-voltage high-current (22.5W, then 40W, 66W and 100W+ classes, needing the original 6A cable); FCP is the older high-voltage scheme at 18W. Both need the tester to speak Huawei's handshake.
• Samsung AFC + PPS: AFC is the legacy adaptive scheme (5V/9V/12V, around 15W, QC2.0-derived); the modern Samsung fast charge is PD-PPS at 25W and 45W.
• MediaTek Pump Express (PE): PE 3.0 around 25W, PE 4.0 built on PD-PPS — fading as vendors consolidate on PD, but still on benches that test older MediaTek devices.
• Vivo FlashCharge: 33W, 44W, 66W, 120W+ classes, a dual-cell scheme similar in spirit to VOOC.
• UFCS: China's cross-brand fusion standard (around 40–65W), worth watching as it spreads beyond one brand.

Where lines actually slip

The protocol list is the easy part. The gaps are per-port and per-protocol:

• PD negotiates, the brand protocol doesn't. A port "supports VOOC" on the label but the tester never exercised the VOOC handshake — so it passes and the phone still trickles.
• EPR falls back silently. A 140W charger on a 100W cable delivers 100W, and a tester that doesn't read the e-marker never flags it.
• PPS range the device requests. The phone asks for 3.3–11V in 20mV steps; the bench only checked 5V/9V/20V fixed — "charges," but not at the rate printed on the box.
• Multi-protocol on a multi-port charger. Port 1 speaks PD-PPS, port 2 speaks VOOC, simultaneously. A tester that runs them one at a time misses the interaction.

When coverage doesn't matter

Vendors of testers won't say this, so it belongs here:

• A plain 5V/2A legacy adapter or a fixed-voltage industrial supply doesn't need protocol coverage you'll never see. Paying for a full protocol library there is paying for shelf space.
• A single fixed-voltage product with no fast-charge claim — verify the voltage and current, skip the protocol circus.

Coverage is a consequence of what your customers' devices actually ask for. Buy the library that matches the device mix, not the longest checkbox.

The hidden costs of protocol coverage

1. Protocol firmware drift. Vendors ship new SuperVOOC tiers and PPS ranges; a tester's protocol library is only current the day it shipped. Ask the vendor about the update path before you buy.
2. The "passed PD, failed brand protocol" return. The most expensive one, because the spec sheet looked fine and the failure is slow, not dead.
3. Calibration of protocol measurement. Negotiation timing and voltage steps are measurements too; they drift and they should be in the calibration scope, not assumed.

The acceptance checklist (print this, hand it to the line)

Before a charger batch ships, these are the protocol checks that catch the slow-charge return:

• Per-protocol negotiation verified for every protocol on your device list — not just PD
• EPR e-marker cable check: confirm the port delivers EPR watts only with a declared 50V/5A cable
• PPS range exercised (3.3–21V in 20mV steps), not just fixed PD voltages
• Each brand protocol on the list actually requested and answered (VOOC/SuperVOOC, Huawei SCP/FCP, Samsung AFC+PPS, MediaTek PE, Vivo FlashCharge)
• Multi-port units tested with different protocols running simultaneously
• Protocol-library firmware version recorded; update path confirmed with the vendor