公开(公告)号：US11070179B2

公开(公告)日：2021-07-20

申请号：US16562116

申请日：2019-09-05

Applicant: Cirrus Logic International Semiconductor Ltd.

Inventor： Frank Cheng ,  Ruoxin Jiang ,  Zhong You

IPC: H03F1/24 ,  H03F1/56 ,  H03F3/181 ,  H03F3/217 ,  H03M1/24

Abstract: An apparatus measures a speaker impedance. A DAC converts a known digital input signal to an audio frequency first analog voltage signal. Resistors with known resistance attenuate the first analog voltage signal to generate a current. The known resistance effectively determines the current because the known resistance is high relative to the speaker impedance. The current is sourced into the speaker to generate a second analog voltage signal. The known resistance is sufficiently high to cause the second analog voltage signal to be inaudible as transduced by the speaker. An amplifier amplifies the second analog voltage signal with a known gain to generate a third analog voltage signal. An ADC converts the third analog voltage signal to a digital output signal. A processing element calculates the impedance of the speaker proportional to the digital output signal based on the known digital input signal, the known resistance, and the known gain.

公开(公告)号：US20210075384A1

公开(公告)日：2021-03-11

申请号：US16562116

申请日：2019-09-05

Applicant: Cirrus Logic International Semiconductor Ltd.

Inventor： Frank Cheng ,  Ruoxin Jiang ,  Zhong You

IPC: H03F3/217 ,  H03M1/24 ,  H03F1/56 ,  H03F3/181

Abstract: An apparatus measures a speaker impedance. A DAC converts a known digital input signal to an audio frequency first analog voltage signal. Resistors with known resistance attenuate the first analog voltage signal to generate a current. The known resistance effectively determines the current because the known resistance is high relative to the speaker impedance. The current is sourced into the speaker to generate a second analog voltage signal. The known resistance is sufficiently high to cause the second analog voltage signal to be inaudible as transduced by the speaker. An amplifier amplifies the second analog voltage signal with a known gain to generate a third analog voltage signal. An ADC converts the third analog voltage signal to a digital output signal. A processing element calculates the impedance of the speaker proportional to the digital output signal based on the known digital input signal, the known resistance, and the known gain.

公开(公告)号：US20180254757A1

公开(公告)日：2018-09-06

申请号：US15910774

申请日：2018-03-02

Applicant: Cirrus Logic International Semiconductor Ltd.

Inventor： Lingli Zhang ,  Frank Cheng ,  Lei Zhu ,  Christian Larsen ,  John L. Melanson

IPC: H03F3/217 ,  H03F3/183

CPC classification number: H03F3/217 ,  H03F3/183 ,  H03F3/2171 ,  H03F3/2175 ,  H03F2200/03 ,  H03F2200/351

Abstract: An improved Class-D amplifier may include a digital PWM modulator that receives a digital audio signal and that provides a PWM signal as an input to an analog PWM modulator of the Class-D amplifier. A digital PWM modulator may be configured to receive a digital signal and to generate a first PWM signal based on the digital signal. A digital PWM driver may be coupled to the digital PWM modulator. The digital PWM driver may be configured to receive the first PWM signal and to generate a reference PWM signal based on the first PWM signal. An analog PWM modulator may be coupled to the digital PWM driver. The analog PWM modulator may be configured to receive the reference PWM signal and to generate an output PWM signal based on the reference PWM signal.