Abstract: For an Apple mobile phone wireless charger with a broken external lead at hand, remove it and observe its internal circuit process design. However, because the main chip model text on the circuit is not clear, it is not clear about its main working principle and has not been repaired.
Wireless charger
The cord of the wireless charger for the phone at hand is broken. Now it is no longer like before when the electrical appliance is damaged, but "the old does not go, the new does not come", but for the broken charger or hope to open to see the engineering design.
The basic parameters of the charger
The wireless charger includes a charging tray and a type-c USB port. Mechanical parameters of the charging disk:
Diameter: 56mm
Thickness: 5.40mm
Weight: 31.4 g
Measure the diameter and thickness of the charging tray
Basic structure
There is a white rubber surface within 3mm of the front edge of the charging disc.
The front structure of the charging tray
Internal structure
Use the one-word cone to pry open the white surface shell, revealing the charging coil behind it. There is a thin ferrite sheet between the charging coil and the structure below, which has cracked by the time the coil plastic shell is pried open.
Charging coil with internal structure
Remove the broken ferrite flakes and underneath is a circuit board sealed with white latex. There is also a ring of white plastic permanent magnet stops around it. This plastic flap is a rigid permanent magnet that is evenly distributed around the charger in a metal housing.
Ferrite fragments, white encapsulated latex, white plastic magnet flaps
Here is the structure of the exposed charger interior:
Metal shell, after magnet testing does not belong to ferrous materials, guess should belong to the aluminum shell;
Ring magnets are distributed at the edges for adsorbing the charger to the phone case;
Special-shaped charging circuit board, LC output power part in one corner of the circuit board;
Internal circuit board
Circuit boards
The figure below shows the main structure of the charger's internal circuitry.
Charger internal circuitry
Using a small one-word taper to pry open the circuit board, it can be found that the circuit board and the metal shell behind it are glued together directly. The heat dissipation of the circuit board can be done directly through the charger metal shell.
Pry the charging board open
The two QFN-encapsulated chips on the circuit board are not clearly visible on the surface text information.
Two chips on the board in the main QFN package
LC device parameters
Coils and resonant capacitors used for magnetic field coupling at wireless points are easier to identify. Its parameters were initially measured using SmartTweezer.
The coil corresponding to the electromagnetic coupling and the resonant capacitor
Using a circuit on-breaker, it can be determined that the four capacitors are in parallel, and the output inductor presents a series resonant circuit.
Output LC series resonance relationship
External magnetic field
In the external electromagnetic field test of the wireless charging board of the Apple mobile phone, the characteristics of the alternating magnetic field outside the charging coil were tested by using an I-shaped inductance. As the phone approaches the charger, the I-shaped inductor measures an alternating magnetic field of 360kHz approximately sine wave signal. Measure the waveform of the alternating electromagnetic field next to the charger using an I-shaped inductor:
The waveform of the alternating electromagnetic field next to the charger is measured using an I-shaped inductor
Inductive alternating signal obtained by the inductor:
The inductive alternating signal obtained by the inductor
Here there is a question, the resonant frequency of the previous measurement circuit board output LC series is only about left and right, why is the actual resonant frequency induced to be about three times its frequency?
summary
Remove an Apple mobile phone wireless charger with a broken external lead at hand and observe its internal circuit process design. However, because the main chip model text on the circuit is not clear, it is not clear how it works. Previous measurements of its operating frequency found a nearly three-fold difference from the internal primary LC resonant frequency.
So if the charge is broken, you should buy one yourself!