Samsung Patents a Wireless Charger That Spots Metal Objects Before Fast Charging Starts
A stray coin or key left on a wireless charging pad can overheat, damage devices, or worse. Samsung's new patent describes a charger that checks whether something unexpected is sitting on the pad before it ever ramps up to full power.
How Samsung's charger tells coins from phones
You toss your phone onto the charging pad before bed, not noticing the house key sitting underneath it. Right now, many wireless chargers would just start pumping out power anyway, which can heat up that key and, over time, cause real problems.
Samsung's patent describes a charging pad that runs a quick scan first. It sends a small pulse of energy through its coil, then listens to how the coil responds. Every object sitting on a pad changes how that coil "rings" at a particular frequency, a little like how a wine glass sounds different when something is resting on its rim. If the reading looks off, the charger flags a potential problem before committing to a full fast-charging session.
Once the pad confirms your phone is there and nothing else suspicious is present, it checks whether your phone supports fast charging. Only then does it open the throttle. If something foreign is still detected, the pad keeps re-checking periodically rather than just giving up or charging blind.
… in accordance with a first difference between the quality factor and the first reference quality factor meeting a designated condition, determine that the wireless power receiving device is placed on a charging area and control the power providing circuit to apply third power to the transmission coil for performing the fast charging …
Translation: The charger checks the quality factor to confirm a safe device is present before it initiates fast charging.
How the quality-factor check flags foreign objects
The system works in two connected stages: a pre-communication scan and a device-level confirmation.
Stage one: the quality-factor check. The charger applies a small "first power" pulse to its transmission coil, then measures what's called the quality factor (a number that describes how efficiently the coil stores and releases energy, essentially how cleanly it "rings"). Metal objects sitting on the pad absorb some of that energy and drag the quality factor down. A lower-than-expected reading is the charger's first signal that something may be wrong.
Stage two: device handshake and comparison. If the pad doesn't immediately flag a foreign object, it sends a second, communication-level power pulse to wake up the receiving device. The charger asks the phone which charging profile it supports: normal or fast. If the phone reports it supports fast charging, it also sends back its own reference quality factor, the number the coil reading should produce when that specific phone is sitting on it alone.
The charger then compares its measured quality factor against the phone's reference number. A big enough gap between the two means a foreign object is also present. In that case:
- Fast charging is withheld.
- The pad periodically re-applies that first small pulse to check whether the object has been removed.
- Once the pad is clear, normal operation resumes.
… based on a difference between the identified resonant frequency and a reference frequency meeting a designated condition, identify that a foreign object is placed on a charging area of the wireless power transmitting device …
Translation: It measures changes in the resonant frequency to spot rogue metal objects sitting on the charging surface.
What this means for wireless fast-charging safety
For you, the practical payoff is that fast charging, which pushes significantly more power through the coil than standard charging, doesn't begin until the pad is confident nothing dangerous is in the way. That matters because fast-charging pads run hotter by design, and a metal object in the field can concentrate that heat quickly.
Samsung's run of wireless-charging safety filings The check also happens automatically, with no input from you. You don't need to remember to clear the pad. If you forget, the charger simply waits and keeps looking, rather than either refusing to charge at all or blindly proceeding. That's the kind of failure-prevention that mostly goes unnoticed until the one night it actually saves you from a scorched nightstand.
This is the 34th Samsung filing we've tracked in battery and power since May, adding to work like one on cell end-of-life decisions and one on estimates with missing data.
The safety check happens before fast charging starts, not after your phone has been sitting on a hot pad for several minutes. That timing shift is the whole point: catching a problem early, when energy levels are still low, is better than catching it late.
For the person using this, the experience is simply that fast charging either begins or it doesn't, and the reason is handled in the background. You won't notice the detection working. You would only notice it if it failed, and that's precisely what this is designed to prevent.
Small safety improvements in everyday products tend to matter more than they sound because they protect millions of people who never think about them at all.
Get our take in your Top Stories
Liked this breakdown? Add Patentlyze as a preferred source on Google, and our plain-English take shows up more often in your Top Stories the next time Samsung patent news breaks.
There are more where this came from
We read every patent application Big Tech publishes and send you the ones worth knowing. Plain English, free, every week.
The drawings
22 drawing sheets from US 2026/0261153 A1 · click any drawing to enlarge
Show the other 14 sheets
Want this weekly breakdown for a company we don't cover? Patentlyze Pro →
Be the first to weigh in