How charging works
How a USB-C charger powers your iPhone: Power Delivery, ripple, efficiency, heat, materials and safety testing, explained with sources and measurements.
How your iPhone asks for power
How your iPhone and a USB-C charger agree on power: PDOs, the request–accept handshake, fixed levels vs PPS and AVS, and what 20W really offers.
Ripple and power quality
What output ripple is, how engineers measure it (20MHz limit, tip-and-barrel probing), typical 20W figures, and what it does and does not mean for your iPhone.
Efficiency and heat
How efficient a 20W charger should be, what no-load draw means, the legal minimums, and how hot a charger normally gets, with dated measurements.
Silicon, GaN and SiC at 20W
How silicon, gallium nitride and silicon carbide differ, where each is used in chargers, and why measured results matter more than the material at 20W.
Inside a 20W charger
What is inside a 20W USB-C charger, using published teardowns of Apple’s 20W adapter (A2305, A2940): every stage from mains to USB-C, explained.
Charger safety and testing
What safety tests a USB-C charger goes through, what BIS registration under CRS means in India, and how to tell a registered charger from a counterfeit.
Which charger does my iPhone need?
Apple’s charger requirement for every iPhone from iPhone 8 to iPhone 18 Pro, what a 20W adapter achieves on each, and when to choose 30W, 40W or 60W.
How fast does 20W charge an iPhone?
Real times to 50%, 80% and 100% on a 20W adapter for recent iPhones, why charging slows near full, and what heat, cables and settings change.
20W or 30W: the difference in minutes
How many minutes a 30W adapter saves over 20W on each iPhone, using dated independent tests, and which models gain nothing from more watts.
How to check a charger’s BIS registration
Step-by-step: find the R-number on a charger, verify it in the BIS CARE app, and confirm the exact model is covered by the registration.
When iPhone says “Slow Charger”
Why iOS labels some power sources “Slow Charger”, the common causes from cables to adapters, and the checks that usually clear it.
Sources
Every source behind our charging pages, with publisher, date, evidence grade and the claim it supports.
Changelog
What changed on our charging and research pages, and when: new measurements, corrected figures and updated guidance.
Frequently asked questions
Answers about ERONIX chargers and iPhone charging: compatibility, speed, safety, BIS registration, warranty and troubleshooting.
Charging glossary
Plain-English definitions of charging terms, from USB Power Delivery, PDO, PPS and AVS to ripple, efficiency, creepage and BIS registration.
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