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CN-122029837-A - Nested controller for an electro-acoustic device

CN122029837ACN 122029837 ACN122029837 ACN 122029837ACN-122029837-A

Abstract

Controlling the electro-acoustic device. The displacement of the membrane is monitored by generating an audio output signal responsive to a time dependent displacement of the membrane in the electro-static acoustic device. The input audio voltage is combined with a first portion of the audio output signal to produce a first error signal as negative feedback. The first error signal is input to the control circuit, and the control signal is output from the control circuit. The control circuit includes an N-order filter, N >3. The control circuit is configured to increase the bandwidth for noise cancellation. Ambient noise may contribute to the displacement of the membrane and the displacement of the membrane due to the ambient noise may be at least partially eliminated within the bandwidth.

Inventors

  • Gabriel Zelzer
  • Mel shaash

Assignees

  • 波音频有限公司

Dates

Publication Date
20260512
Application Date
20240820
Priority Date
20230821

Claims (20)

  1. 1. A method for controlling an electro-acoustic device, the method comprising: Monitoring the displacement of a membrane in the electro-acoustic device by generating an audio output signal responsive to the time dependent displacement of the membrane; inputting an input audio voltage; First combining the input audio voltage with a first portion of the audio output signal to produce a first error signal as negative feedback; inputting the first error signal to a control circuit and outputting a first control signal from the control circuit, wherein the control circuit includes an N-order filter, N >3, and The control circuit is configured to increase bandwidth for noise cancellation.
  2. 2. The method of claim 1, wherein the filter comprises a plurality of nested filters, each nested filter being of second order or higher.
  3. 3. The method of claim 1, wherein ambient noise contributes to displacement of the membrane, the method further comprising: The control circuit is configured to at least partially cancel displacement of the membrane due to the ambient noise.
  4. 4. The method of claim 1, further comprising: the audio output signal is transformed before the first combination with the input audio voltage.
  5. 5. The method of claim 1, further comprising: Combining a second portion of the audio output signal with the output from the first sub-circuit to produce a second error signal; Inputting the second error signal to a second sub-circuit, and The first control signal 26 is output from the second sub-circuit.
  6. 6. The method of claim 5, further comprising: The second portion of the audio output signal is transformed before the second is combined with the output from the first sub-circuit.
  7. 7. The method of claim 1, wherein the control circuit comprises a plurality of serially connected control sub-circuits.
  8. 8. The method of claim 7, wherein each control sub-circuit comprises an integrator circuit and a differentiator circuit connected in parallel.
  9. 9. The method of claim 8, wherein the integrator circuit is a leaky integrator circuit.
  10. 10. The method of claim 8, wherein the differentiator circuit is a non-ideal differentiator circuit.
  11. 11. The method of claim 7, wherein each control sub-circuit comprises a low pass filter and a high pass filter connected in parallel.
  12. 12. The method of any of claims 1-11, wherein the electro-acoustic device comprises a first electrode and a second electrode, wherein the first electrode is disposed parallel to the membrane, wherein the membrane is configured to mechanically respond to a first electric field that varies according to a respective electric potential applied between the first electrode and the membrane, wherein the second electrode is disposed parallel to the membrane opposite the first electrode, wherein the membrane is configured to mechanically respond to a second electric field that varies according to a respective electric potential applied between the second electrode and the membrane, the method further comprising: generating a detection signal varying at radio frequency; first coupling a portion of the detection signal into the first electrode; inverting a portion of the detection signal and secondarily coupling the inverted portion of the detection signal into the second electrode; first applying a first DC bias voltage to the first electrode; Second applying a second DC bias voltage to the second electrode, wherein the second DC bias voltage has a polarity opposite to the first DC bias voltage; sensing a voltage signal from the membrane; inputting the voltage signal from the membrane at an input of a high pass filter that selectively passes at least a portion of the radio frequency of the probe signal and selectively blocks at least a portion of the audio frequency to produce a filtered signal modulated at radio frequency; inputting at least a portion of the radio frequency modulated filtered signal at a first multiplier input; inputting at least a portion of the probing signal at a second multiplier input; Outputting a product signal proportional to the product of the filtered signal and the detection signal at the first multiplier input and the second multiplier input, and Demodulating the product signal to produce the audio output signal responsive to the time dependent displacement of the membrane.
  13. 13. An electronic device, comprising: a detector configured to monitor displacement of a membrane in an electro-static acoustic device by generating an audio output signal responsive to time-dependent displacement of the membrane; an audio input configured to input an input audio voltage; a first comparator configured to combine the input audio voltage with a first portion of the audio output signal to generate a first error signal as negative feedback; a control circuit configured to input the first error signal and thereby output a first control signal, wherein the control circuit comprises an N-order filter, N >3; wherein the control circuit is configured to increase the bandwidth for noise cancellation.
  14. 14. The electronic device of claim 13, wherein the filter comprises a plurality of nested filters, each nested filter being second or higher order.
  15. 15. The electronic device of claim 13, wherein ambient noise contributes to the displacement of the membrane, the electronic device further configured to at least partially cancel the displacement of the membrane due to the ambient noise.
  16. 16. The electronic device of claim 13, further comprising: a transform block configured to transform the first portion of the audio output signal prior to combination with the audio input signal.
  17. 17. The electronic device of claim 13, wherein the control circuit comprises a plurality of serially connected control sub-circuits, wherein the control sub-circuits comprise a first sub-circuit and a second sub-circuit.
  18. 18. The electronic device of claim 17, further comprising: A second comparator configured to combine a second portion of the audio output signal with the output of the first sub-circuit to generate a second error signal; Wherein the second error signal is configured to be input into the second sub-circuit.
  19. 19. The electronic device of claim 13, further comprising: A transform block configured to transform the second portion of the audio output signal prior to combination with the output from the first sub-circuit.
  20. 20. The electronic device of claim 17, wherein each control sub-circuit comprises an integrator circuit and a differentiator circuit connected in parallel.

Description

Nested controller for an electro-acoustic device Background 1. Technical field The present invention relates to operating an electro-acoustic device including headphones and speakers, and in particular, to a control system and method for increasing bandwidth for noise cancellation in an electro-acoustic device. 2. Description of related Art In the field of high-fidelity sound reproduction, electrostatic speakers are attracting attention due to inherent excellent sound quality and smooth response over a wide frequency range. In such devices, a flexible sound-emitting membrane is located adjacent to the electrodes, or in the case of a push-pull arrangement, adjacent to a pair of electrodes, one on each side of the membrane. A dc polarization potential is applied between the membrane and the electrode and an audio signal is superimposed on the electrode such that the membrane moves in response to the audio signal. The electrode is acoustically transparent such that sound generated by the moving film radiates outwardly through the electrode to the listening area. Electrostatic devices are very efficient both electrically and mechanically. The electrical impedance is high and decreases with increasing acoustic frequency. The high electrical impedance results in very low operating currents and minimal electrical losses. In mechanical terms, there are no moving parts other than the very light weight moving film. The electrostatic device is thus inherently more energy efficient than the electro-acoustic devices (electrodynamic acoustic device) currently used in battery-powered electronic devices. Brief summary of the invention Various circuits and methods for controlling an electro-acoustic device are disclosed herein. The displacement of the membrane is monitored by generating an audio output signal responsive to a time dependent displacement of the membrane in the electro-static acoustic device. The input audio voltage is combined with a first portion of the audio output signal to produce a first error signal as negative feedback. The first portion of the audio output signal may be transformed before being combined with the audio input signal. The first error signal is input to the control circuit, and the control signal is output from the control circuit. The control circuit includes an N-order filter, N >3. Ambient noise may contribute to the displacement of the membrane and the displacement of the membrane due to the ambient noise may be at least partially eliminated within the bandwidth. The control circuit is configured to increase the bandwidth for noise cancellation. The control circuit may comprise a plurality of control sub-circuits connected in series, including a first sub-circuit and a second sub-circuit. A second portion of the audio output signal may be combined with the output of the first sub-circuit to produce a second error signal. The second error signal may be input into the second sub-circuit. The second portion of the audio output signal may be transformed before being combined with the output from the first sub-circuit. Each control sub-circuit may include an integrator circuit and a differentiator circuit. The integrator circuit may be a leaky integrator circuit. The differentiator circuit may be a non-ideal differentiator circuit. Alternatively, each sub-circuit may comprise a low-pass filter and a high-pass filter connected in parallel. The electro-acoustic device may include a first electrode and a second electrode. The first electrode may be disposed parallel to the membrane. The membrane may be configured to mechanically respond to a first electric field that varies according to a respective potential applied between the first electrode and the membrane. The second electrode may be disposed opposite the first electrode in parallel to the film. The membrane may be configured to mechanically respond to a second electric field that varies according to a respective potential applied between the second electrode and the membrane. A detection signal may be generated that varies at radio frequency. A first portion of the detection signal may be coupled into the first electrode. A portion of the detection signal may be inverted and the inverted portion may be coupled into the second electrode. The coupling may be capacitive or inductive. A first DC bias voltage may be first applied to the first electrode. A second DC bias voltage may be applied to the second electrode. The second DC bias voltage may have a polarity opposite to the first DC bias voltage. The first and second DC bias voltages may be symmetrically applied to the first and second electrodes with opposite polarities. The respective portions of the detection signal may be symmetrically applied to the first electrode and the second electrode with opposite polarities. The voltage signal from the membrane may be sensed by inputting the voltage signal from the membrane at the high pass filter input. The high pass filter may selectively