Blog – What is Foreign Object Detection in Wireless Charging, Anyway?

What is Foreign Object Detection in Wireless Charging, Anyway?
What is Foreign Object Detection in Wireless Charging, Anyway?

Nobody can argue that Wireless Charging is an incredibly convenient way to keep our favorite handheld devices charged up, and to provide some remedy for battery anxiety.  Wireless charging is (almost) everywhere nowadays — in our phones, in our cars, in our airports, in our restaurants and coffee shops, and soon to be in places we haven’t even thought of yet.  But is it safe?  We have seen internet articles about wireless charging shortening the life of your smartphone’s battery, or other ways wireless charging can harm your device.  But unfortunately, those articles are not written by people who understand wireless charging, and are false and misleading.  (Spoiler:  There is no difference in charging your phone from a wire or from wireless — it’s just another way of getting energy.)

Back to our question:  Is wireless charging safe?  The answer, of course, is a resounding “yes”, provided it is done correctly.  One of the biggest safety topics to understand in a modern-day wireless charger is how to prevent the wireless charger from heating metal objects to unsafe levels.  Because the frequency used by the wireless charger is very effective at heating metal objects, it is up to us as system designers to ensure that any stray metal objects, such as wayward coins, that present themselves in the middle of a charging session are not a cause for alarm (as in “fire alarm”).  In order to protect ourselves from these “foreign” metal objects, we try to detect this safety threat with something called “Foreign Object Detection”, or FOD.

Historically, ever since the introduction of Foreign Object Detection (FOD) methods in the Wireless Power Consortium Qi (pronounced “chee”) standard, the general public has had a misunderstanding of what FOD really means.

If a random person is asked what FOD must do, in most cases the answer would be that if a coin is placed on the transmitter surface, the transmitter should indicate the presence of a foreign object. This is basically the functionality of a metal detector.

In practice most receivers like phones and battery packs have metal elements around the receiving coil. User experience can be negatively affected if these metal elements are wrongly classified as foreign objects. According to the Qi specification, a foreign object is detected only after a Qi receiver is placed on the transmitter surface, information is exchanged between the two devices and a decision is made about the foreign object presence based on the estimation of how much power would actually be dissipated into the foreign object during power transfer. It is perfectly acceptable to have an object on the transmitter surface during power transfer if it does not heat above certain thresholds.

 

OBJECT PLACEMENT ON THE TRANSMITTER SURFACE

The most popular method to detect the presence of an object on the transmitter surface is the Direct Q Measurement. It monitors for changes to the quality factor (Q factor) of the transmitter coil or for changes in its inductance or resistance. Other methods that detect the presence of objects on the transmitter coil can be based on change in capacitance, light reflection or transmission, changes in weight/pressure, resonance at 1MHz, metal detectors using auxiliary coils, etc.

The Qi specification has an informative section reserved for these mechanisms. The resonance shift method is already described and is related to the change in quality factor. The fact that a resistance change is also induced by most (but not all) receivers can be used to improve the detection of the object but it is not enough to determine if the presumed foreign object would actually absorb enough energy during power transfer to cause a significant increase in its temperature.

 

CONFUSION BETWEEN THE DIRECT Q MEASUREMENT AND THE EXISTING PRE-POWER FOD METHOD

These values are measured when a receiver is placed on a MP-A1 transmitter coil and they are reported by the receiver during the negotiation phase.

The transmitter may not use a MP-A1 coil and in that case its measurements of Q and resonant frequency must be converted from the actual transmitter coil to how they would look like on the MP-A1 coil before a decision can be made regarding the mismatch between the measured values and the reported values from the receiver.

The Qi specification has a high-level description of the pre-power FOD methods but the mechanism used to calculate the Q factor seen by a MP-A1 coil is not provided.

The direct measurement of the transmitter coil quality factor without a receiver present can at most inform the transmitter of the existence of metallic objects on the charging surface, and the transmitter can use this data to inform the user to clear these objects before placing the receiver on the surface. This method can also be used after a confirmed FOD event and subsequent removal of power.  In that case, the transmitter uses this method to ensure the user has removed all objects from the charging surface before allowing the receiver to be placed to restart charging.

This method alone cannot determine if the metallic object will consume sufficient power to heat the object, but it can be used in combination with other power loss methods to educate the user to always remove all metal objects from the transmitter surface before/during/after charging.

Confusing?  The key is in the name of the action:  Foreign Object Detection.  It’s one thing to detect a metal object, but it’s a whole different ballgame to determine if that object will lead to an unsafe situation if we charge a phone while that object is present.  As a charger, what you want to do is charge a user’s battery — that is, after all, the reason you exist.  Therefore a charger must have a robust and deterministic plan for deciding which objects are clearly unsafe, and which objects can still be present during a charging cycle without cause for alarm.  If I am too conservative, then nobody gets to charge.  But if I am too lenient, then somebody gets burned (maybe literally).  Striking the right, and safe, balance is the art of good transmitter design.

Emanuel Stingu Spark Connected, CTO

“It is perfectly acceptable to have an object on the transmitter surface during power transfer if it does not heat above certain thresholds.” – Emanuel Stingu, Chief Technology Officer at Spark Connected.

About Spark Connected

Spark Connected | powering the world, wirelessly

Spark connected is an industry leader specializing in multiple advanced and safe wireless power technologies that benefits a wide variety of applications in the Automotive, Industrial, Infrastructure, Medical, Telecom and Security, Robotics, Factory Automation, IOT, Smart Home, and Consumer markets.

Spark is transforming wireless power delivery and intelligent battery charging with innovative platforms, disruptive technology and breakthrough products enabling an enhanced user experience for all. The company specializes in Product Development and Engineering Solutions with a team of passionate innovators with decades of combined deep domain expertise.

Spark Connected is a Full Member of the Wireless Power Consortium.

Please forward inquiries to:
Marina Wolf/Ruwanga Dassanayake
(972) 855-8026
sales(at)sparkconnected.com

Spark Connected has been elected to multiple co-chair positions at the Wireless Power Consortium

Spark Connected has been awarded co-chair positions at the Wireless Power Consortium.
Spark Connected has been awarded co-chair positions at the Wireless Power Consortium.

Dallas, TX. February 21, 2020.

Spark Connected, a global leader in developing advanced and innovative wireless power technology and system level solutions, has been elected to co-chair positions at the Wireless Power Consortium.

Spark Connected, a global leader in developing advanced and innovative wireless power technology and system level solutions, has been elected to co-chair positions at the Wireless Power Consortium.

Ken Moore, CEO, was elected to the Co-Chair of the WPC Mobile/Laptop Task Force. This task force develops an extension of the Qi Specification that enables laptop charging up to 60W and maintains compatibility with Qi chargers and Qi receivers.

Emanuel Stingu, CTO, was elected to both the Co-Chair of the Automotive Application Group and the New Power Transmitter Review Task Force. The Automotive Application Group discusses requirements for implementing Qi in automotive applications and works to support the WPC members that develop applications in the automotive space voice their concerns and implement solutions that improve the safety and the reliability of the Qi standard.

The New Power Transmitter Review Task Force helps member companies innovate and at the same time guarantee that every new TX design is well designed, safe and fully interoperable, and introduces the 30W-45W transmitter types in the Qi specification.


About WPC

Established in 2008, the Wireless Power Consortium is an open, collaborative standards development group of more than 500 member companies from around the globe. WPC’s member companies are large and small competitors and ecosystem partners representing brands from all parts of the industry and all parts of the globe. Members collaborate with a single purpose: worldwide compatibility of all wireless chargers and wireless power sources.

As wireless charging continues to evolve beyond consumer handheld devices, there are myriad of other new applications, such as laptops, tablets, drones, robots, connected car and the intelligent cordless kitchen. The WPC maintains and develops standards for a variety of different wireless power applications. This includes:

  • The Qi standard, for smartphones and other portable mobile devices. Qi delivers up to 15W today. A future extension will also deliver up to 60W to enable laptop charging in addition to charging smartphones and other portable mobile devices with wide positioning freedom.
  • The Ki Cordless Kitchen standard, for kitchen appliances, for delivering up to 2,200W.
  • The Medium Power standard, a simple low-cost solution delivering 30 – 200W for power tools, robotic vacuum cleaners, e-bikes, and other battery-powered devices that don’t require compatibility with the Qi standard for mobile phones charging.

With more than 5000 different Qi Certified wireless charging products in the market, the WPC uses a network of independent authorized test labs around the globe that test specific properties for safety, interoperability, and usability. Spark Connected is proud to serve on these committees and task forces, and advance the future of wireless charging and power in the market.

Emanuel Stingu Spark Connected, CTO

About Spark Connected

Spark Connected | powering the world, wirelessly

Spark connected is an industry leader specializing in multiple advanced and safe wireless power technologies that benefits a wide variety of applications in the Automotive, Industrial, Infrastructure, Medical, Telecom and Security, Robotics, Factory Automation, IOT, Smart Home, and Consumer markets.

Spark is transforming wireless power delivery and intelligent battery charging with innovative platforms, disruptive technology and breakthrough products enabling an enhanced user experience for all. The company specializes in Product Development and Engineering Solutions with a team of passionate innovators with decades of combined deep domain expertise.

Spark Connected is a Full Member of the Wireless Power Consortium.

Please forward inquiries to:
Marina Wolf/Ruwanga Dassanayake
(972) 855-8026
sales(at)sparkconnected.com

Press Release – Spark Connected Augments LiDAR with Wireless Power Technology

Press Release - The Phoenix wireless power solution by Spark Connected

Spark Connected Wireless Power Solution for LiDAR in Autonomous Vehicles

Spark Connected’s new solution named Phoenix, is designed and engineered to wirelessly power LiDAR (Light Detection and Ranging) applications.

DALLAS, TEXAS. August 20, 2019.

Spark Connected, a leading technology developer of advanced and innovative wireless power system solutions, today announced a proprietary high-performance wireless power solution, named The Phoenix designed and engineered for LiDAR (Light Detection and Ranging) applications.

From self-driving autonomous vehicles to automated services robots in residential to floor robots in connected factories (Industry 4.0), LiDAR can be used to measure distance to a target by illuminating the target with laser light and measuring the reflected light with a sensor and thereby creating a 3D map for the application to operate.

“Basic concepts of LIDAR are the same as radar and sonar. While the technology has been around for a while LiDAR is finding more applications as we live in a more automated world. The Phoenix is a unique solution that can power this technology wirelessly in brushless motor environments,” said Emanuel Stingu, Chief Technology Officer at Spark Connected.

Key Features of the Spark Connected Phoenix Wireless Power Solution:

  • Up to 30W power delivery across higher distances and through rotating assemblies
  • Solution includes transmitter and receiver
  • Custom and irregular shaped charging coils
  • Powered by the Infineon AURIX™ or XMC™ Wireless Power Controller
Emanuel Stingu Spark Connected, CTO

“The Phoenix is a unique solution that can power LiDAR applications wirelessly in brushless motor environments” – Emanuel Stingu, Chief Technology Officer at Spark Connected.

About Spark Connected

Spark Connected | powering the world, wirelessly
Spark connected is an industry leader specializing in multiple advanced and safe wireless power technologies that benefits a wide variety of applications in the Automotive, Industrial, Infrastructure, Medical, Telecom and Security, Robotics, Factory Automation, IOT, Smart Home, and Consumer markets.
Spark is transforming wireless power delivery and intelligent battery charging with innovative platforms, disruptive technology and breakthrough products enabling an enhanced user experience for all. The company specializes in Product Development and Engineering Solutions with a team of passionate innovators with decades of combined deep domain expertise.

Spark Connected is a Full Member of the Wireless Power Consortium.

Please forward inquiries to:
Dana Veal/Ruwanga Dassanayake
(972) 855-8026
sales(at)sparkconnected.com

For more information visit: https://www.sparkconnected.com

Press Release – Spark Connected Boosts VR/AR and Gaming with New Wireless Charging Solution

Press Release - The Griffin wireless power solution by Spark Connected
Spark Connected, a leading technology developer of advanced wireless power system solutions, announced a unique high-performance wireless power solution named The Griffin, designed and engineered for VR/AR and Gaming applications.

DALLAS, TEXAS. April 8, 2019.

Spark Connected, a leading technology developer of advanced and innovative wireless power system solutions, today announced a proprietary high-performance wireless charging solution, named The Griffin designed and engineered for VR/AR and Gaming applications.

From entertainment, to education, to industrial and robotic applications, Virtual and Augmented Reality have become mainstream technologies for advanced user interfaces. The Griffin, comprising both a wireless power transmitter and companion receiver, provides a complete system that can integrate into an end-product resulting in an unparalleled user charging experience.

“One of the exciting advantages of The Griffin platform from a technical perspective is its ability to charge almost any form factor using custom antennas. In the VR and gaming space, this is critical in solving many of our customers’ challenges. The resonant technology in The Griffin not only provides a flexible platform for charging today’s VR headsets, but also provides a way to charge multiple handheld controllers as well. So while our customers bring new innovations to the VR headset which provide freedom of movement that challenges the 5 senses, we believe that freedom of movement should apply to charging devices in the real world as well.” said Emanuel Stingu, Chief Technology Officer at Spark Connected.

Key Features of the Spark Connected Griffin Wireless Power Solution:

  • Complete Transmitter and Receiver Wireless Power System
  • Supports Wirelessly Charging One-to-one and Multiple-devices
  • Unparalleled User Experience in Charging
Emanuel Stingu Spark Connected, CTO

“One of the exciting advantages of The Griffin platform from a technical perspective is its ability to charge almost any form factor using custom antennas. In the VR and gaming space, this is critical in solving many of our customers’ challenges.” – Emanuel Stingu, Chief Technology Officer at Spark Connected.

About Spark Connected

Spark Connected | powering the world, wirelessly
Spark connected is an industry leader specializing in multiple advanced and safe wireless power technologies that benefits a wide variety of applications in the Automotive, Industrial, Infrastructure, Medical, Telecom and Security, Robotics, Factory Automation, IOT, Smart Home, and Consumer markets.
Spark is transforming wireless power delivery and intelligent battery charging with innovative platforms, disruptive technology and breakthrough products enabling an enhanced user experience for all. The company specializes in Product Development and Engineering Solutions with a team of passionate innovators with decades of combined deep domain expertise.

Spark Connected is a Full Member of the Wireless Power Consortium.

Please forward inquiries to:
Dana Veal
(972) 855-8026
sales(at)sparkconnected.com

For more information visit: https://www.sparkconnected.com