Patents by Inventor Lars Risbo

Lars Risbo has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 10397701
    Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.
    Type: Grant
    Filed: October 31, 2018
    Date of Patent: August 27, 2019
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Lars Risbo, Ryan Erik Lind, Jasjot Singh Chadha
  • Patent number: 10313787
    Abstract: A predictive back-emf protection methodology for an electromechanical system, including a signal processor that processes a source signal to provide a modified source signal, a driver that converts the modified source signal to a drive signal, and an electromechanical transducer that generates, from the drive signal, a transducer response, and a back-emf signal coupled back to the driver output. A predictive back-emf generator (such as a routine in the signal processor) is characterized by a back-emf transfer function (linear parameterized model of the electromechanical transducer) for transforming an input signal into a transform back-emf representation of a back-emf signal predicted by the back-emf transfer function as a response of the electromechanical transducer to such input signal. The signal processor processes the source signal based on the transform back-emf representation to generate the modified source signal input to the driver.
    Type: Grant
    Filed: August 14, 2015
    Date of Patent: June 4, 2019
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Lars Risbo, Anker Bjørn-Josefsen, Kim N. Madsen
  • Publication number: 20190149920
    Abstract: The present invention relates in one aspect to a method of controlling or limiting diaphragm excursion of a loudspeaker. The method comprising steps of receiving a first audio signal and deriving an excursion signal representing diaphragm excursion of the electrodynamic loudspeaker from the first audio signal. The method additionally comprises deriving an excursion envelope from the excursion signal and applying a second audio signal, derived from the first audio signal, to an input of an adjustable low-frequency suppressor. The second audio signal is filtered by the adjustable low-frequency suppressor to selectively attenuate low-frequency components based on the excursion envelope to produce a processed audio signal with reduced low-frequency content.
    Type: Application
    Filed: May 2, 2017
    Publication date: May 16, 2019
    Applicant: Purifi APS
    Inventors: Bruno PUTZEYS, Lars RISBO
  • Publication number: 20190069087
    Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.
    Type: Application
    Filed: October 31, 2018
    Publication date: February 28, 2019
    Inventors: Lars Risbo, Ryan Erik Lind, Jasjot Singh Chadha
  • Patent number: 10158942
    Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.
    Type: Grant
    Filed: February 15, 2018
    Date of Patent: December 18, 2018
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Lars Risbo, Ryan Erik Lind, Jasjot Singh Chadha
  • Publication number: 20180176683
    Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.
    Type: Application
    Filed: February 15, 2018
    Publication date: June 21, 2018
    Inventors: Lars Risbo, Ryan Erik Lind, Jasjot Singh Chadha
  • Patent number: 9967663
    Abstract: Systems and methods for loudspeaker protection against excessive excursion are described. In an illustrative, non limiting embodiment, a method may include splitting an input signal into two or more signals, each of the two or more signals within a given frequency band; independently selecting between a power attenuation or an excursion attenuation for each of the two or more signals; independently applying the selected power attenuation or excursion attenuation to each of the two or more signals; combining the attenuated two or more signals into an output signal; and providing the output signal to a loudspeaker.
    Type: Grant
    Filed: December 2, 2015
    Date of Patent: May 8, 2018
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Anker Bjoern-Josefsen, Lars Risbo, Theis Christiansen
  • Patent number: 9930452
    Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.
    Type: Grant
    Filed: December 30, 2016
    Date of Patent: March 27, 2018
    Assignee: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Lars Risbo, Ryan Erik Lind, Jasjot Singh Chadha
  • Publication number: 20180020288
    Abstract: A system includes a class D amplifier and a current steering digital-to-analog converter (DAC) directly connected to the class D amplifier. The system also includes a common mode servo circuit coupled to a node interconnecting the current steering DAC to the class D amplifier. The common servo circuit amplifies a difference between a common mode signal determined from the node and a reference voltage and generates a feedback current to the node based on the amplified difference. A feed-forward common-mode compensation circuit is included to reduce an alternating current (AC) ripple from the class D amplifier. The feed-forward common-mode compensation circuit includes first and second resistors coupled to respective outputs of the class D amplifier. A current mirror is coupled to the first and second resistors and is configured to sink a current from the node to ground that approximates a common mode feedback current of the class D amplifier.
    Type: Application
    Filed: December 30, 2016
    Publication date: January 18, 2018
    Inventors: Lars RISBO, Ryan Erik LIND, Jasjot Singh CHADHA
  • Patent number: 9661430
    Abstract: Methods for modeling a loudspeaker having a passive radiator include applying a stimulus signal to a speaker within the cabinet, wherein the stimulus is applied over a frequency range. The sound pressure level (SPL) in the cabinet is measured as a function of frequency during application of the stimulus signal. At least one coefficient based on the measured SPL is derived, wherein at least one passive radiator parameter is a function of the at least one coefficient.
    Type: Grant
    Filed: July 27, 2015
    Date of Patent: May 23, 2017
    Assignee: Texas Instruments Incorporated
    Inventors: Lars Risbo, Theis Harboe Christiansen
  • Publication number: 20160192070
    Abstract: Systems and methods for loudspeaker protection against excessive excursion are described. In an illustrative, non limiting embodiment, a method may include splitting an input signal into two or more signals, each of the two or more signals within a given frequency band; independently selecting between a power attenuation or an excursion attenuation for each of the two or more signals; independently applying the selected power attenuation or excursion attenuation to each of the two or more signals; combining the attenuated two or more signals into an output signal; and providing the output signal to a loudspeaker.
    Type: Application
    Filed: December 2, 2015
    Publication date: June 30, 2016
    Applicant: Texas Instruments Incorporated
    Inventors: Anker Bjoern-Josefsen, Lars Risbo, Theis Christiansen
  • Publication number: 20160057533
    Abstract: A predictive back-emf protection methodology for an electromechanical system, including a signal processor that processes a source signal to provide a modified source signal, a driver that converts the modified source signal to a drive signal, and an electromechanical transducer that generates, from the drive signal, a transducer response, and a back-emf signal coupled back to the driver output. A predictive back-emf generator (such as a routine in the signal processor) is characterized by a back-emf transfer function (linear parameterized model of the electromechanical transducer) for transforming an input signal into a transform back-emf representation of a back-emf signal predicted by the back-emf transfer function as a response of the electromechanical transducer to such input signal. The signal processor processes the source signal based on the transform back-emf representation to generate the modified source signal input to the driver.
    Type: Application
    Filed: August 14, 2015
    Publication date: February 25, 2016
    Inventors: Lars Risbo, Anker Bjørn-Josefsen, Kim N. Madsen
  • Publication number: 20160037276
    Abstract: Methods for modeling a loudspeaker having a passive radiator include applying a stimulus signal to a speaker within the cabinet, wherein the stimulus is applied over a frequency range. The sound pressure level (SPL) in the cabinet is measured as a function of frequency during application of the stimulus signal. At least one coefficient based on the measured SPL is derived, wherein at least one passive radiator parameter is a function of the at least one coefficient.
    Type: Application
    Filed: July 27, 2015
    Publication date: February 4, 2016
    Inventors: Lars Risbo, Theis Harboe Christiansen
  • Patent number: 8774419
    Abstract: In an embodiment of the invention, the voice coil of an electro dynamic transducer is protected against thermal overload by estimating the temperature of a magnet in the electro dynamic transducer. When a power limit based on the temperature of the magnet and on a predetermined voice coil temperature limit is reached by an audio signal, the power applied to the voice coil is reduced.
    Type: Grant
    Filed: September 28, 2011
    Date of Patent: July 8, 2014
    Assignee: Texas Instruments Incorporated
    Inventors: Lars Risbo, Milind Anil Borkar, Theis Buchwald Christiansen
  • Publication number: 20130077796
    Abstract: In an embodiment of the invention, the voice coil of an electro dynamic transducer is protected by measuring the power of the input audio signal. When a predetermined power limit is reached by the input audio signal, the power of the input audio signal is reduced.
    Type: Application
    Filed: September 28, 2011
    Publication date: March 28, 2013
    Applicant: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Lars Risbo, Milind Anil Borkar, Theis Buchwald Christiansen, Wendyam Fernand David Traore
  • Publication number: 20130077794
    Abstract: In an embodiment of the invention, the voice coil of an electro dynamic transducer is protected against thermal overload by estimating the temperature of a magnet in the electro dynamic transducer. When a power limit based on the temperature of the magnet and on a predetermined voice coil temperature limit is reached by an audio signal, the power applied to the voice coil is reduced.
    Type: Application
    Filed: September 28, 2011
    Publication date: March 28, 2013
    Applicant: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Lars Risbo, Milind Anil Borkar, Theis Buchwald Christiansen
  • Publication number: 20130077795
    Abstract: In an embodiment of the invention, over-excursion of a diaphragm in an electro dynamic transducer is reduced by attenuating low frequency content in an audio signal when the power of an audio signal exceeds a predetermined power limit. The audio signal is used to drive the input of an amplifier and the output of the amplifier drives the electro dynamic transducer. When the audio signal does not exceed a predetermined power limit, the low frequency content in the input audio signal is amplified.
    Type: Application
    Filed: September 28, 2011
    Publication date: March 28, 2013
    Applicant: TEXAS INSTRUMENTS INCORPORATED
    Inventors: Lars Risbo, Milind Anil Borkar, Theis Buchwald Christiansen
  • Patent number: 8369973
    Abstract: Asynchronous sample rate conversion for use in a digital audio receiver is disclosed. Different algorithms are applied for the upsampling and downsampling cases. In the upsampling case, the input signal is upsampled and filtered, before the application of a finite impulse response (FIR) filter. In the downsampling case, the input signal is filtered by an FIR filter, and then filtered and downsampled. The FIR coefficients of the fractional delay FIR filter are calculated by evaluation of polynomial expressions over intervals of the filter impulse response, at times corresponding to the input sample points.
    Type: Grant
    Filed: March 4, 2009
    Date of Patent: February 5, 2013
    Assignee: Texas Instruments Incorporated
    Inventor: Lars Risbo
  • Patent number: 8189817
    Abstract: System for pulse-width-modulated class D audio amplifiers. In one preferred embodiment an adder is described to generate a difference signal responsive to an input signal and a feedback signal, a pulse-width-modulator coupled to the adder to compare the difference signal to a reference signal and produce a pulse-width-modulated signal based on the comparing, a filter coupled to an output of the pulse-width-modulator, and a loop filter having a first input coupled to the output of the filter and a second input coupled to the input of the filter, the loop filter to generate a feedback signal by applying transfer functions to signals at its inputs. The loop transfer function of the amplifier is minimum aliasing error transfer function. The minimum aliasing error properties provide low distortion and taking the feedback from the output of the filter reduces high frequency output impedance.
    Type: Grant
    Filed: September 8, 2008
    Date of Patent: May 29, 2012
    Assignee: Texas Instruments Incorporated
    Inventors: Lars Risbo, Soeren Poulsen
  • Patent number: 8144043
    Abstract: A signal converting system is described that has a multi-segment digital to analog converter coupled to one or more error shaping loops. Each error shaping loop includes a quantizer with a feedback loop configured to generate a control signal responsive to a stream of symbols and to an error signal. Each error shaping loop also includes an inter-symbol-interference (ISI) shaping loop coupled to receive the control signal and to produce an ISI portion of the error signal that is responsive to inter-symbol transition rate.
    Type: Grant
    Filed: April 28, 2010
    Date of Patent: March 27, 2012
    Assignee: Texas Instruments Incorporated
    Inventors: Lars Risbo, Rahmi Hezar, Burak Kelleci, Anker Bjoern-Josefsen