Introduction
Currently, wireless power is very popular due to efficient
energy transfer, short charging time and ease of use. But power shortages are
common when transferring over longer distances. This is because they have
limited distance between transmit and receive while charging process.
Basic Theory
Faraday's law:
Faraday's law:
Figure 1
From the figure 1 that shows EMF
is proportional to the number of turns in the coil and multiplied by the rate
of change of effective magnetic flux generated by the magnetic source. We will
assume that the flux source will be the charging station. Mutual coupling is
ignored and the charging station is assumed to be very close to the device, which
means minimum flux leakage.
The Faraday's law is shown in figure
2. The EMF will be induced when they have movement from the magnet. The voltmeter
is used to show the EMF was created.
Figure 2
From the mechanism at figure 2 we can be used to charge a battery with a voltage
rating lower than the EMF. Example, for a charger rating of 5 volts, 0.7 A
charging a Li-ion battery of rating 3.7 volts 1650 mAh, i.e., the battery at a
voltage of 3.7 volts can output 1.65 A for about an hour (or 6.11 Wh) it will
take about 1 hour 45 mins to completely charge the battery from nil. Other
factors like battery age and temperature also determines charging time.
Shows in figure 3, the EMF that induced at receiver is used to charge a battery, just like an AC adapter.
Shows in figure 3, the EMF that induced at receiver is used to charge a battery, just like an AC adapter.
Figure 3
Figure 4 is shows the concept of charging
station, Magnetic flux will be induced inside the coil. The principle of ampere
circuit law [4] is used that can determine the magnetic field associated with a
current. The EMF will control by number of turn coil and flux that induce.
Figure 4
How the
wireless charging work for Smartphone.
Basically, wireless charging have 2 parts. It calls
transmit and receive. They have no physical contact between this part. The
electrical current is then used to charge or re-charge the battery at the smartphone.
Transmit (TX): The alternating current (AC) is sent to the
transmitter coil from the transmitter circuit. The AC then induces
a time varying magnetic field in the transmitter coil.
AC will flowing within the transmitter coil and magnetic field will induces which extends to
the receiving coil (within a specified distance).
The magnetic field generates current within the
receiver and transmit coil of the device.
The process also referred as magnetic or resonant coupling and is
achieved by both coils resonating at the same frequency.
Receive (RX): Current will flowing within the receiver coil and
converted into direct current (DC) by the receiver circuit, which will be used
to charge the battery in smartphone
Source :
Referance :
1. http://powerbyproxi.com/wireless-charging/.
2. https://www.quora.com/How-do-wireless-charging-pads-work.
3. http://www.qiwireless.com/wireless-charging-htc-one-m8/ (21 Dec 2015)
4. https://en.wikipedia.org/wiki/Amp%C3%A8re's_circuital_law
