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Wireless power for mobile phones - System overview

Wireless power for mobile phones - System overview. Nov 25, 2012 V1.1. System overview. Embedded in mobile device After market case/dongle connected through the power connector Add-on connected through dedicated WLC pins. Rx. Tx. Embedded in furniture/car/infrastructure

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Wireless power for mobile phones - System overview

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  1. Wireless power for mobile phones - System overview Nov 25, 2012 V1.1

  2. System overview • Embedded in mobile device • After market case/dongle connected through the power connector • Add-on connected through dedicated WLC pins Rx Tx • Embedded in furniture/car/infrastructure • After market mat

  3. Block diagram Power Source Communication Power Resonance circuit & power driver TXCoil RXCoil Matching circuit & Rectifier Control Unit Control Unit Demodulator Modulator DC/DC

  4. Tx-Rx coils

  5. Tx-Rx coils – Magnetic induction basics Electric current flowing in a wire gives rise to a magnetic field around it. Alternating the current will alternate the magnetic field Shaping the wire as a loop will band that field in a “lung” shape. Figures: http://ipodphysics.com/magnets-loop-or-coil.phpt

  6. Tx-Rx coils – Magnetic induction basics Energy coupling means that an energy source has a mean of transferring its energy to a second object. Transformers may use iron core to deliver the magnetic flux Wireless power system is an air core transformer between planar coils one on top of the other. Figure 1: http://www.electrical4u.com/what-is-transformer-definition-working-principle-of-transformer/ Figure 2: http://makezine.com/2013/11/04/component-of-the-month-transformer/ Figure 3: http://www.britannica.com/EBchecked/media/1355/Magnetic-field-B-of-two-current-loops-with-currents-in

  7. Tx-Rx coils – Coil designs Single coil– Most common design Pros – chip and easy solution / Cons – difficult alignment Large Tx coil – Common in loosely coupled systems Pros – easy alignment / Cons – difficult design and tune Array of small Tx coil – One or more coils provide power simultaneously Pros – easy alignment / Cons – Cost of coils and drivers 3 coil array – Only one coil provides power at a time Pros – easy alignment / Cons – Cost of coils and drivers Fig1:http://www.qitah.com/blog.htmlFig2:http://phys.org/news203691107.htmlFig3:http://patentimages.storage.googleapis.com/US20130119773A1/US20130119773A1-20130516-D00015.png

  8. Resonancecircuit and power driver

  9. Resonancecircuit and power driver Power driver Resonance circuit Resonant circuit - Determines the self resonance frequency of the Tx, Mainly influenced by the coil and the resonance capacitors. Power driver - pushes the current to the resonance circuit in different frequencies around the self resonance Figure 1: HIGH EFFICIENCY LOOSELY COUPLED WIRELESS POWER TRANSFER SYSTEM VIA MAGNETIC INDUCTION By ZHEN NING LOW

  10. Resonancecircuit • The overall impedance the driver “sees” when modeled as a series RLC circuit • At the resonance frequency the capacitive and inductive impedance equals • The driver then sees resistive only minimum overall impedance and the power • delivery to the Rx is maximal • The resonance curve changes with each different : • Rx design (EE & ME) • Phone material • Misalignment from the center • Variation during manufacturing • Load drawn Amplitude Frequency Figure 1: http://perlgeek.de/blog-en/perl-6/rakudo-memory-leaks.html

  11. Driving the power • Frequency control – the driver changes the frequency along the resonance curve • Control becomes difficult when Q is high & at resonance control is unstable • Frequency range shall be dynamic due to curve changes • Passing to the second side of the peak may reverse the control rules Amplitude Frequency Other methods of control: Voltage control – increasing the input voltage will increase the current through the coil and the transmitted power Pulse width control – increasing the on time of the signal will increase the transmitted power

  12. Data modulation

  13. Data modulation Power driver Matching circuit & Rectifier Modulator • load modulation - • Rx modulates the operational frequency by short circuiting the coil to a secondary load • The secondary load changes both the load of the Tx and the resonance curve • The demodulator sense the change in voltage, current or phase between them on the operational frequency Demodulator

  14. Data modulation Example of voltage change at the Tx Example of phase change at the Tx Signals in reality may vary a lot from the simulation presented….

  15. Questions? Comments? Remarks? It’s called wireless power, it’s the future Thanks, Rotem Shraga (shraga.rotem@gmail.com ; 052-6443944) Figure: http://www.fodrizzle.com/wp-content/uploads/2012/02/funny-birds-wire-drawing.jpg

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