A patent application from March 2017 shows that Samsung is developing a dual charging pad that can charge multiple devices using the Qi standard. Two different charging modes, inductive and resonance, will be present in the device. Samsung notes that having both charging methods in one device will eliminate the need to have two separate chargers if a user has multiple devices that require different modes. It's similar to Apple's new AirPower charging pad that was unveiled alongside the iPhone 8 and X.
A charger with tightly coupled coils, or inductive mode, provides the highest amount of power with the best efficiency. The main advantages of this mode are minimal heat buildup and faster charging times. The coils are the same size and the distance between them are much less than their diameter. With inductive mode, the bottom transmitter coil operates at a frequency that's slightly different from the resonant frequency of the receiver coil. This is known as off-resonant operation.
In resonant mode, the coils are separated more, decreasing the magnetic coupling of the two. This type of setup operates at the resonant frequency of the receiver, unlike inductive mode that operates at off-resonant. The main advantage of this mode is convenience. Unlike inductive mode, which requires a very precise alignment between the charger and device being charged, resonant mode broadens the targets. For example, Starbucks and other business that have Qi charges built into tables will use resonant mode. This mode also allows multiple devices to be charged simultaneously with one coil setup. The disadvantages of this are slower charging times and the potential for electromagnetic interference (EMI) during operation.
To put this in layman terms, think of inductive mode as a laser, which is powerful and hits a small target. Resonant mode is like a flashlight, which is less powerful and spreads out to hit a broader target. A flashlight also “leaks” more light throughout a room, illuminating other areas to a degree that are outside of the target area. Think of that as the EMI problem.
Samsung notes in the the patent application that they're providing “a multi-mode charging apparatus and a method for supporting both the magnetic induction method and the magnetic resonant method.” Since the patent application is already several months old, we could see Samsung's new charger launch alongside the Galaxy S9 in early 2018.
Source: Patently Mobile
