Wireless charging is one of the recent innovations which involves charging without a direct connectivity. A charging mat or a sleeve kind of thing will be available which enables charging. The principle involves magnetic coupling between two coils. When a magnetic coil carrying current is placed near another magnetic coil, due to electro-magnetic induction, current will be induced in another coil. The current will be regulated to charge a battery using power management circuit. The following manufacturers produces chips for power management:
- IDT
- Texas Instruments
- ON semiconductor
- Freescale semiconductor
- Qualcomm
- NXP semiconductor
- Panasonic
Several standards for wireless charging are in existence. the following are the list of these standards:
- Qi
- Power 2.0 by PMAT
- A4WP
The main disadvantage of all these standards is the coupling factor. As the distance of the receiver gets separated more from transmitter, the coupling gets reduced and hence efficiency. This implies that distance from the coil should not exceed coil size. Another disadvantage is that receiver coil must be properly aligned with transmitter coil to get maximum transfer. A new standard by PMAT named Witricity enables the distance from coil exceeding more compared to coil size. This is like charging anywhere in the room.
Standards like A4WP are supported by companies like Intel which can be used in it's smartphone, laptops and net book. Considering the standard, Qi operates in the range 100-205 KHz and Power2.0 operates in the range 277-357 KHz.
Some of the existing products with wireless charging capability:
- Nokia Lumina 920 (uses TI chipset)
- Samsung Galaxy S4
- iPhone 4S
- HTC devices
- Google Nexus 4
- Charging pads by JBL (this also serves up as speaker)
- Charging pads for mobile phones by LG, Nokia, Samsung
- Charging sleeves by Energizer, Duracell
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