A Breakthrough in Wireless Charging Enables Two Devices to Be Charged on the Road

August 28, 2020 by Jake Hertz

A new solution from NXP allows multiple devices to charge from one MWTC controller, making it the first of its kind in the in-car wireless charging field.

Anyone who owns a smartphone undoubtedly knows the struggle of being tethered to an outlet to keep one's phone alive. Wired charging has been the standard for a long time, but it comes with drawbacks, such as easily-damaged wires and undesired clutter.

Charging a phone in the car is a particularly cumbersome challenge because it requires adapters and minimal charging ports, plus the driver has to deal with the distraction of a loose wire near the gear shifter. 

It wasn’t until the late 2010s that wireless charging was integrated into most smartphones, offering a much-desired alternative to conventional charging. Now, car manufactures are looking to integrate wireless charging capabilities into their vehicles in order to alleviate some of these issues. 


Inductive Charging and Faraday’s Law 

Wireless charging, also known as inductive charging, is a relatively new technology; however, it's built on the well-known and longstanding principle of electromagnetism. 


Graphical depiction of Faraday’s Law

Graphical depiction of Faraday’s Law. Image used courtesy of Live Science


The underlying principle is that of electromagnetic induction, famously described by Faraday’s Law. Essentially, Faraday’s Law of Induction describes how an electric current produces a magnetic field and, conversely, how a changing magnetic field generates an electric current in a conductor.

This is the same principle leveraged in modern electricity generation and distribution infrastructure (i.e transformers and generators). 


Inductive Charging

Using electromagnetic induction, wireless chargers work on a basic level as follows: 

An alternating current is sent through a transmitter coil, which creates an oscillating magnetic field. On the receiver end, there is a receiving coil that has a current induced in it from the transmitter’s alternating magnetic field.


Example wireless charging system

Example wireless charging system. Image used courtesy of Renesas


A full wireless charging system will require other components, including:

  • Coil driver
  • Capacitors to achieve a resonant frequency
  • Diode rectifiers to convert to DC
  • Battery charging circuit
  • Battery

Today, wireless charging has to meet the QI standard, which allows for universality and reliability in wireless charging systems. 


Charge for Two Mobile Devices

Recognizing the demand for wireless charging in cars, NXP has recently announced its newest inductive charging solution. NXP claims that this new solution is “the first multi-device vehicle wireless charging solution driven by a single MWCT controller.”

This claim is significant because it allows both passenger and driver to charge their device wirelessly and simultaneously through a single console. On the design side, carmakers benefit from a reduced cost and physical footprint for the charger. 


NXP claims that this multi-device wireless charging solution for vehicles is a "market first." Image used courtesy of NXP

NXP claims the solution is able to charge two devices both at 15 W. To put this into perspective, a standard iPhone charger operates at 5 V and 1 A, or 5 W. This implies that charging speed is improved three times over a traditional wall charger.


Wireless Charging: a New Staple in Cars?

This news from NXP is relevant in that it provides benefits to end-users and designers. Wireless charging is a developing technology that is continuing to grow in popularity. This news nods to its progress, pushing for a future in which wireless charging is a staple in all vehicles.