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Wireless charging is the use of magnetic induction to charge a
mobile phone. AC voltage is applied to a coil integrated in the
charger (transmitter). This produces a constantly changing mag-
netic field. The receiver (mobile phone) also has a coil in which a
voltage is induced by the changing magnetic field. The electronics
in the receiver then supply charging voltage to the mobile phone.
Audi uses the Qi standard developed by the Wireless Power Consor-
tium for this purpose. The Qi standard permits communication
between the charger and the mobile phone during the charging
phase.
Maximum power is 5 watts
1)
. As smartphones have a working
voltage of 5 volts, the maximum current is 1 ampere.
The wireless charging adaptor is integrated in the Audi phone box.
The adaptor consists of the charging electronics and 4 separate
magnetic coils. In this case, the aerial required for mobile phone
reception is wound around the coils.
If the MMI is active (NO contact on), the charging electronics are
activated by the phone-on signal. The charging electronics use
(inductive and capacitive) sensors to check if there is an object in
the Audi phone box. When a mobile phone which supports wireless
charging is detected, the system starts the charging cycle by
increasing the electrical current. This minimises power consump-
tion in case charging is not needed. A charging cycle is depicted in
the telephone menu by a symbol at the bottom right-hand side of
the MMI display.
Only one coil is used per charging cycle. The charging electronics
always use the best coil. In this case, the coil which transfers the
highest electrical current to the mobile phone is the best. To
continuously use the optimal coil, the mobile phone sends infor-
mation to the charging electronics. In very simple terms, the
mobile phone indicates when the received power level is too low.
The charging electronics then increase the power output or switch
over to another coil. If the mobile phone if receiving enough power
again, this coil is used until the mobile phone requests charging
again. Some mobile phones can also indicate that the battery is
fully charged. The charging cycle stops when the charging electron-
ics receive this information.
Wireless charging (country-dependent)
1)
The actual possible power consumption depends on the receiver.
Note
Only mobile phones with suitable hardware are charged
The term Qi is of Chinese origin and means "vital energy".
Coupling aerial
Magnetic coils
Display at starting of charging
Audi phone box from below
PCB with coupling aerial and
magnetic coils
Audi phone box
Telephone
Navigation
Map
The mobile device is being charged
in the charging cradle
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