Electromagnetic Shielding Techniques for Inductive Powering Applications

1. Electromagnetic Shielding Techniques for Inductive Powering Applications Ronan Dunne Supervisor: Dr. Maeve Duffy Co Supervisor: Liam Kilmartin

2. Topics of discussion • Background • Objectives • Tasks Completed

3. Background • Inductive power transfer is a method of transferring power wirelessly from a source to an object requiring power. • Inductive coupling - Inductive coupling involves the use of magnetic fields to stimulate the movement of current through a wire • Nikola Tesla – Tesla coil. • Recent developments in technology • Charging Platforms for mobile devices • Biomedical applications • Advantage: No hazardous, inconvenient cables and wires.

4. Applications Charging Platform • Contains inbuilt transmitter coils which induce a current in the receiver coils in the mobile devices when they are brought close to the platform. • Transmitter & receiver coils must be close together as the magnetic fields they produce are small. • Bigger the magnetic field, the less efficient it becomes. • Improve efficiency - implement resonant circuits in both the Primary and Secondary sides of circuits.

5. Applications (Cont.) Biomedical applications: • The transmitter and receiver coils in these devices are much further apart resulting in low inductive coupling levels. • Inductive coupling is used to transfer pulses from the externally worn transmitter to the implanted receiver circuit. • These pulses are applied to the relevant nerve endings

6. Objectives • Build demonstrator circuit • Investigate Electromagnetic shielding techniques • Verify calculations and results by applying analytic and finite element analysis techniques

7. Tasks Completed • Demonstrator circuit • Transmitter and receiver coils • Resonance • Electromagnetic shielding • Calculations (Matlab) & Simulations (Maxwell) • Mutual Inductance • Inductance of different coils • Shielding Effectiveness

8. Transmitter and receiver coils • Transmitter coil is connected to power source which produces a magnetic field. • For a current to be induced, must add a receiver coil inside the transmitter coils magnetic field. • receiver coil must be close to the transmitter coil

9. Built demonstrator circuit which contains transmitter and receiver coils. • Capacitors were added to create resonance on the primary and secondary sides which improves power produced. • Inductive power transfer was shown by creating enough power to light an LED.

10. Resonance • By adding resonance circuits that have the same resonance frequency the current can tunnel from the transmitter to the receiver coil. • This improves the efficiency of energy transfer as energy is not scattered in all directions.

11. Measurements and results Vs without capacitor (w/o resonance): Vs increased by 5.06V (pk-pk) Vs with 1nF capacitor, resonating @ 630Khz: Vs increased by 2.72V (pk-pk) Vs with resonance on both sides: Vs with magnetic material added to core of receiver coil: Vs increased by 11.5V(pk-pk)

12. Software • Matlab was used to programme formulas and Maxwell was used to simulate results. • Mutual Inductance between two planar windings Formula for Mutual Inductance Magnetic field around the winding

13. Measurements and Results (cont.) • Power across diode was calculated in Excel using results measured on oscilloscope. The Following results were calculated: @ Vp = 2V (Pk-Pk) P = 885W @ Vp = 4V (Pk-Pk) P = 16.3 mW @ Vp = 6V (Pk-Pk) P = 45.0 mW @ Vp = 8V (Pk-Pk) P = 81.9 mW @ Vp = 10V (Pk-Pk) P = 118 mW

14. Electromagnetic Shielding • EM shielding is the process of limiting the flow of EM fields by using a barrier made to block the magnetic fields. • Several tests to compare shielding performance of different materials. • No shield • Ferrite shield • Copper shield • Ferrite and Copper shield

15. Results SE = 16.48dB

16. Maxwell simulations • Maxwell used to simulate the effects of different shielding techniques by placing the plates within the magnetic field created by the transmitter coil. Magnetic field without ferrite plate Magnetic field with ferrite plate

17. Conclusion • The demonstrator circuit clearly shows Inductive power transfer by creating enough power to light an LED. • implementing resonance circuits, increases power produced. • Adding magnetic material also increases power. • Electromagnetic Shielding was used to block magnetic fields. It was proved that a double layer substrate made of copper and ferrite acts as the best shield. Satisfactory results of up to 16.5dbs were produced. • Maxwell was used to simulate behaviour of magnetic fields and to verify results.

18. Questions???