# US 10,484,791 B2 · Amplifier speaker drive current sense > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,484,791 B2 - Document ID: US10484791B2 - Status: Granted - Kind: B2 - Application number: 16/218,615 - Filed: 2018-12-13 - Published: 2019-04-18 - Granted: 2019-11-19 - Earliest claimed: 2016-07-06 - Assignees: Texas Instruments Incorporated - Applicants: Texas Instruments Incorporated - Inventors: Mohit Chawla - Web page: https://patentgrep.com/patent/US10484791B2 ## CPC - H04R 3/007: {Protection circuits for transducers} - H03F 3/187: in integrated circuits - H03F 3/2171: {with field-effect devices (H03F3/2173 - H03F3/2178 take precedence)} - H03F 3/2173: {of the bridge type} - H03F 3/2175: {using analogue-digital or digital-analogue conversion (H03F3/2173 takes precedence)} - H03F 3/45475: {using IC blocks as the active amplifying circuit} - H03M 3/464: {Details of the digital/analogue conversion in the feedback path} - H03F 2200/03: the amplifier being designed for audio applications - H03F 2200/405: the output amplifying stage of an amplifier comprising more than three power stages - H03F 2203/45116: Feedback coupled to the input of the differential amplifier - H03F 2203/45546: the IC comprising one or more capacitors feedback coupled to the IC - H03F 2203/45594: the IC comprising one or more resistors, which are not biasing resistor - H03M 3/43: {the quantiser being a single bit one} - H03M 3/45: {with distributed feedforward inputs, i.e. with forward paths from the modulator input to more than one filter stage} - H03M 3/452: {with weighted feedforward summation, i.e. with feedforward paths from more than one filter stage to the quantiser input} - H04R 29/001: {for loudspeakers (H04R29/007 takes precedence)} - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - H03F: AMPLIFIERS - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) ## Abstract A class-D amplifier includes measurement of speaker current via the low-side drive transistors of the amplifier. In one embodiment, a class-D amplifier includes two high-side transistors, two low-side transistors, a first sense resistor, a second sense resistor, and a sigma delta analog to digital converter (ΣΔ ADC). The two high-side transistors and two low-side transistors are connected as a bridge to drive a bridge tied speaker. The first sense resistor is connected between a first of the low-side transistors and a low-side reference voltage. The second sense resistor is connected between a second of the low-side transistors and the low-side reference voltage. The ΣΔ ADC is coupled to the bridge to measure voltage across the first sense resistor and the second sense resistor. ## Claims ### Claim 1 A class-D amplifier, comprising: two high-side transistors and two low-side transistors connected as a bridge to drive a bridge tied speaker; a first sense resistor connected between a first of the low-side transistors and a low-side reference voltage; a second sense resistor connected between a second of the low-side transistors and the low-side reference voltage; and a sigma delta analog to digital converter (ΣΔ ADC) coupled to the bridge to measure voltage across the first sense resistor and the second sense resistor. ### Claim 2 (depends on 1) The class-D amplifier of claim 1, wherein the ΣΔ ADC comprises: a first digital to analog converter (DAC) dedicated to measurement of voltage across the first sense resistor; and a second DAC dedicated to measurement of voltage across the second sense resistor. ### Claim 3 (depends on 2) The class-D amplifier of claim 2, wherein the first DAC and the second DAC are trimmed to compensate for a difference between the first sense resistor and the second sense resistor. ### Claim 4 (depends on 2) The class-D amplifier of claim 2, wherein the first DAC and the second DAC are continually active while operating the class-D amplifier. ### Claim 5 (depends on 1) The class-D amplifier of claim 1, wherein the ΣΔ ADC comprises: a differential amplifier; a first switch to switchably connect one of a positive side of the first sense resistor or a negative side of the second sense resistor to a first input of the differential amplifier; a second switch to switchably connect one of a positive side of the second sense resistor or a negative side of the first sense resistor to a second input of the differential amplifier. ### Claim 6 A speaker drive and current measurement system, comprising: a transistor bridge comprising: two high-side switching transistors; a first low-side switching transistor; a second low-side switching transistor; a first sense resistor that connects the first low-side switching transistor to a low-side reference voltage; and a second sense resistor that connects the second low-side switching transistor to the low-side reference voltage; a sigma delta analog to digital converter (ΣΔ ADC) coupled to the bridge, the ΣΔ ADC comprising: a first digital to analog converter (DAC) dedicated to measurement of voltage across the first sense resistor; and a second DAC dedicated to measurement of voltage across the second sense resistor. ### Claim 7 (depends on 6) The system of claim 6, wherein the ΣΔ ADC comprises: a differential amplifier; a first switch to switchably connect one of a positive side of the first sense resistor or a negative side of the second sense resistor to a first input of the differential amplifier; and a second switch to switchably connect one of a positive side of the second sense resistor or a negative side of the first sense resistor to a second input of the differential amplifier. ### Claim 8 (depends on 6) The system of claim 6, wherein the first DAC and the second DAC are continually active while the bridge is driving the speaker. ### Claim 9 (depends on 6) The system of claim 6, wherein the first DAC and the second DAC are trimmed to compensate for a difference between the first sense resistor and the second sense resistor. ### Claim 10 An audio amplifier, comprising: a driver configured to drive a speaker; and a current monitoring system configured to measure the current output by the driver; wherein the driver comprises: two high-side transistors and two low-side transistors connected as a bridge to drive the speaker; a first sense resistor connected between a first of the low-side transistors and a low-side reference voltage; a second sense resistor connected between a second of the low-side transistors and the low-side reference voltage; wherein the current monitoring system comprises a sigma delta analog to digital converter (ΣΔ ADC) coupled to the driver to measure voltage across the first sense resistor and the second sense resistor, the ΣΔ ADC comprising: a differential amplifier; a first switch to switchably connect one of a positive side of the first sense resistor or a negative side of the second sense resistor to a first input of the differential amplifier; a second switch to switchably connect one of a positive side of the second sense resistor or a negative side of the first sense resistor to a second input of the differential amplifier; a first digital to analog converter (DAC) dedicated to measurement of voltage across the first sense resistor; and a second DAC dedicated to measurement of voltage across the second sense resistor.