System and method for applying a sound signal to a multi coil electrodynamic acoustic transducer

Patent metadata

Field	Value
Publication number	US-10623865-B2
Application number	US-201815936937-A
Country	US
Kind code	B2
Filing date	Mar 27, 2018
Priority date	Mar 27, 2017
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

A transducer system, comprising an electrodynamic acoustic transducer (1) with a membrane (3), a plurality of voice coils (7, 8) electrically switched in series, and a magnet system (9, 10, 11) is presented, wherein just an outer tap/terminal (T2) of the serially connected voice coils (7, 8) is electrically connected to an audio output of an amplifier (17). Moreover, a method for feeding a sound signal to an electrodynamic acoustic transducer (1) is presented, wherein the voice coils (7, 8) are driven by an audio signal just via an outer tap/terminal (T2) of the serially connected voice coils (7, 8).

First claim

What is claimed is:

1. Transducer system, comprising:
an electrodynamic acoustic transducer with a membrane;
a coil arrangement attached to the membrane, wherein the coil arrangement comprises two voice coils electrically connected in series;
a magnet system being designed to generate a magnetic field transverse to a longitudinal direction of a wound wire of the coil arrangement;
a tap/terminal of the coil arrangement /serially connected voice coils being electrically connected to an audio output of an amplifier; and
an electronic offset compensation module/circuit connected to the coil arrangement, and configured to apply a control voltage U CTRL to at least one of the voice coils and to alter said control voltage U CTR until the electromotive force U emf1 of the first coil or a parameter derived thereof and the electromotive force U emf2 of the second coil or said parameter derived thereof substantially reach a predetermined relation.

2. Transducer system according to claim 1 , wherein the amplifier is the only amplifier electrically connected to the coil arrangement.

3. Transducer system according to claim 1 , wherein a connection point between two voice coils is electrically connected to an input of the amplifier.

4. Transducer system according to claim 1 , comprising an electronic zero detection module/circuit, which is designed to be connected to the coil arrangement of the electrodynamic acoustic transducer, and wherein the electronic zero detection module/circuit is designed to
a) measure a voltage U 1 at the first coil and a second voltage U 2 at the second coil;
b) calculate a ratio U 1 /U 2 between the first voltage U 1 and the second voltage U 2 and
c) determine the magnetic zero position of the membrane by detecting a state, in which
the above ratio U 1 /U 2 equals 1 and
a gradient dU 1 /dU 2 of the above ratio is negative.

5. Transducer system according to claim 1 , comprising an position calculation module/circuit, which is designed to be connected to the coil arrangement of the electrodynamic acoustic transducer, wherein the position calculation module/circuit is designed to
d) calculate a velocity of the membrane based on an input voltage U in and an input current I in to a coil of the transducer and based on an idle driving force factor of the transducer in an idle position or in a magnetic zero position of the membrane;
e) calculate a position of the membrane by integrating said velocity;
f) calculate the velocity of the membrane based on the input voltage U in and the input current I in to the coil of the transducer and based on a driving force factor BL(x) of the transducer at the position of the membrane calculated in step e) and to
g) recursively repeat steps e) and f).

6. Method for feeding a sound signal to an electrodynamic acoustic transducer with a membrane, a coil arrangement attached to the membrane, wherein the coil arrangement comprises a plurality of voice coils, in particular two voice coils, electrically connected in series and arranged in-between first and second outer taps/terminals, and a magnet system being designed to generate a magnetic field transverse to a longitudinal direction of a wound wire of the coil arrangement, wherein the coil arrangement is driven by sound signals fed only to one of the outer taps/terminals of the coil arrangement/serially connected voice coils, and wherein a control voltage U CTRL is applied to at least one of the voice coils and altered until the electromotive force U emf1 of the first coil or a parameter derived thereof and the electromotive force U emf2 of the second coil or said parameter derived thereof substantially reach a predetermined relation.

7. Method as claimed in claim 6 , wherein the sound signals are fed to one of the outer taps/terminals of the serially connected voice coils by a single amplifier.

8. Method as claimed in claim 6 , wherein the control voltage is applied to one of the outer taps/terminals of the serially connected voice coils.

9. Method as claimed in claim 6 , wherein the electromotive force U emf1 of the first coil and the electromotive force U emf2 of the second coil are calculated by the formulas
ti U emf1 =U in1 ( t )− Z C1 ·I in ( t )
ti U emf2 =U in2 ( t )− Z C2 ·I in ( t )
wherein Z c1 is the coil resistance of the first coil, U in1 (t) is the input voltage to the first coil at the time t and I in (t) is the input current to the first coil at the time t and wherein Z C2 is the coil resistance of the second coil, U in2 (t) is the input voltage to the second coil at the time t and I in (t) is the input current to the second coil at the time t.

10. Method as claimed in claim 6 , wherein a parameter derived from the electromotive force U emf1 , U emf2 is an absolute value of the electromotive force U emf1 , U emf2 , a square value of the electromotive force U emf1 , U emf2 or a root mean square value of the electromotive force U emf1 , U emf2 .

11. Method as claimed in claim 6 , wherein the control voltage U CTRL is applied to at least one of the voice coils and altered until the low pass filtered electromotive force U emf1 of the first coil or a parameter derived thereof and the low pass filtered electromotive force U emf2 of the second coil or said parameter derived thereof substantially reach a predetermined relation.

12. Method as claimed in claim 6 , wherein a delta sigma modulator is used for applying a control voltage U CTRL to at least one of the voice coils.

13. Method as claimed in claim 12 , wherein a signal output of the delta sigma modulator is filtered before it is applied to the coil arrangement.

14. Method as claimed in claim 6 , wherein a control voltage U CTRL is applied to both the first coil and the second coil.

15. Method as claimed in claim 6 , wherein a sound signal is applied to the first coil and/or the second coil during application of a control voltage U CTRL .

16. Method as claimed in claim 6 comprising the steps of:
a) measuring a voltage U 1 at the first coil and a second voltage U 2 at the second coil;
b) calculating a ratio U 1 /U 2 between the first voltage U 1 and the second voltage U 2 and
c) determining a magnetic zero position of the membrane by detecting a state, in which
the above ratio U 1 /U 2 equals 1 and
a gradient dU 1 /dU 2 of the above ratio is negative.

17. Method as claimed in claim 6 comprising the steps of
a) measuring a voltage U 1 at the first coil and a second voltage U 2 at the second coil;
b) calculating a ratio (U 1 +K)/(U 2 +K) between the first voltage U 1 plus a constant value K and the second voltage U 2 plus the constant value K, wherein the constant value K is above the negative minimum of the second voltage U 2 or below the negative maximum of the second voltage U 2 and
c) determining the magnetic zero position of the membrane by detecting a state, in which
the above ratio (U 1 +K)/(U 2 +K) equals 1 and
a gradient d(U 1 +K)/d(U 2 +K) of the above ratio is negative.

18. Method as claimed in claim 16 , wherein in said state additionally the electromotive force U emf1 of the first coil and/or the electromotive force U emf2 of the second coil is positive.

19. Method as claimed in claim 17 , wherein in said state additionally the electromotive force U emf1 of the first coil and/or the electromotive force U emf2 of the second coil is positive.

20. Method as claimed in claim 16 , wherein in said state additionally the electromotive force U

Assignees

• Sound Solutions Int Co Ltd
• Aac Technologies Pte Ltd
• Aac Tech Nanjing Co Ltd

Inventors

• Reining Friedrich

Classifications

• H04R9/063 Primary

  using a plurality of acoustic drivers (H04R1/24 and H04R1/403 take precedence) · CPC title

• H04R9/046

  Construction · CPC title

• H04R9/045

  Mounting (H04R9/043 takes precedence) · CPC title

• H04R9/025 Primary

  Magnetic circuit · CPC title

• H04R2209/041

  Voice coil arrangements comprising more than one voice coil unit on the same bobbin · CPC title