12 Jun The Ultimate Guide to Wireless Charging
The Ultimate Guide to Wireless Charging
What is the Wireless Charging?
Wireless charging is to transfer power through non-conductive means (usually using magnetic field as a bridge for power transfer).
- The transmitter station is directly connected to power source
- The receiver mobile is put on the active area of station surface for charging
- Magnetic Induction (MI): Transmitter coil that creates a magnetic field; receiver coil picks up the magnetic field and generates electric current.
- Magnetic Resonance (MR): Both transmitter and receiver coils operate at approximately same natural frequencies.
What Frequency change can change the output power?
- When the main circuit parameters are determined, circuit gain versus frequency change under a certain load.
- When Fn > 1 , System operates in inductive l oad range
- Wnen Fn < 1 , System operates in capacitive l oad range
- Resonance Frequency calculation
𝐹𝑛=1/2𝜋𝐿𝐶
System Overview
- Base Station
−Contains one, or more transmitters
−Transmitter provides power to receiver
- Mobile Device
−Contains a receiver that provides power to a load (e.g. a battery)
−Receiver provides control information to transmitter
System Overview (Power Conversion)
- Power Conversion Unit converts electrical power to wireless power signal
- Power Pickup Unit converts wireless power signal to electrical power
System Overview (Control)
- Receiver controls the power to the output load
− To the need of the mobile device (required power)
− To the desired operation point (e.g. output current, voltage)
- Transmitter adapts power transfer
− To the need of the receiver (required power)
− To the desired operation point (e.g. primary coil current)
System Overview (Communication)
- Receiver sends messages
−To provide control and device information to the transmitter by load modulation on the power signal
−To receive the device information from the transmitter by de-modulation (to be added in Qi v1.2)
- Transmitter receives messages
−To receive control and device information from the receiver by de-modulation
−To provide device information to the receiver by frequency modulation on the power signal (to be added in v1.2)
Power Pick Up (Receiver)
- Secondary coil (Ls)
- Serial resonance capacitor (Cs ) for efficient power transfer
- Parallel resonance capacitor (Cd ) for detection purposes
- Rectifier: full bridge (diode, or switched) + capacitor
- Output switch for (dis-)connecting the load
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