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Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE 20041 Integrating switch mode audio power amplifiers and.

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Presentation on theme: "Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE 20041 Integrating switch mode audio power amplifiers and."— Presentation transcript:

1 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Integrating switch mode audio power amplifiers and electro dynamic loudspeakers for a higher power efficiency Søren Poulsen Ph.D. Student Ørsted·DTU Technical University of Denmark Michael A. E. Andersen Professor Ørsted·DTU Technical University of Denmark

2 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Integrating switch mode audio amplifier and loudspeaker Using the voice coil inductance as output filter

3 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Loudspeaker impedance Maximum phase shift ~ 65° –Real part caused by eddy current losses in the magnetic system Resonances at high frequencies –Voice coil inductance –Voice coil capacitance

4 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE PWM modulation schemes 2-level modulation 3-level modulation

5 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE PWM HF output spectra 2-level modulation 3-level modulation M=0.01 M=1

6 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Pushing up ressonance frequency Layer to layer capacity

7 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Pushing up voice coil resonance frequency Minimizing L·C –L  N 2 –C  1/number of winding layers Fewer turns More winding layers

8 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Voice coil fill factor

9 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Efficiency improvement with low impedance voice coils Efficiency constant for same fill-factor Higher fill factor benefits efficiency

10 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Power stage losses, 2-level modulation Output stage losses Using same DIE area and voice coil fill factor for different supply voltages Ripple current included Single ended and full bridge output stage 5V, 10V, 20V, 40V supply

11 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Improving the magnetic system Modifying magnetic system with other materials near the voice coil Ferrite –Exellent HF properties –Bmax  0,5T Powder iron –Exellent HF properties –Bmax  1-1,4T

12 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Prototype magnetic system, FEM simulation -26 iron powder material used

13 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Standard magnetic system Blue: Above gap Green: In gap Red: Below gap Short voice coil

14 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Prototype magnetic system Blue: Above gap Green: In gap Red: Below gap Short voice coil

15 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Standard and prototype magnetic system Blue: Prototype system Green: Std. system Full length voice coil

16 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Magnetic system power loss vs. f s, 2-level modulation Blue: M=0Green: M=0.25Red: M=0.5 Magenta: M=0.75Orange: M=1 Prototype magnetic systemStandard magnetic system

17 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Magnetic system power loss vs. f s, 3-level modulation Green: M=0.25Red: M=0.5 Magenta: M=0.75Orange: M=1 Prototype magnetic systemStandard magnetic system

18 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Audio quality Listening tests carried out –ABC blind test No prove of sound degradation

19 Søren Poulsen, Ørsted·DTU, Automation Technical University of Denmark NORPIE Conclusion Using the voice coil inductance as output filter for the amplifier possible Eddy current losses in the magnetic system can be reduced significantly Higher voice coil fill factor possible Dedication favours low impedance interface Significant improvement of power efficiency achievable


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