# US 12,184,239 B2 · Method to reduce noise in microphone circuits > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,184,239 B2 - Document ID: US12184239B2 - Status: Granted - Kind: B2 - Application number: 17/625,074 - Filed: 2020-07-07 - Published: 2022-08-25 - Granted: 2024-12-31 - Earliest claimed: 2019-07-08 - Assignees: Creative Technology Ltd - Applicants: Creative Technology Ltd - Inventors: Yam Fei Lian; Siew Ling Loke - Web page: https://patentgrep.com/patent/US12184239B2 ## CPC - H03F 1/26: Modifications of amplifiers to reduce influence of noise generated by amplifying elements - H03F 3/181: Low-frequency amplifiers, e.g. audio preamplifiers - H03F 3/183: with semiconductor devices only - H04R 3/00: Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) - G06F 3/162: {Interface to dedicated audio devices, e.g. audio drivers, interface to CODECs} - H02M 1/123: {Suppression of common mode voltage or current} - H02M 1/15: using active elements - H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)} - H03F 2200/03: the amplifier being designed for audio applications - H03F 2200/189: the ground, reference or shield potential difference between different chips being controlled - H03F 2200/372: Noise reduction and elimination in amplifier - H03F 2200/459: Ripple reduction circuitry being used in an amplifying circuit - H04R 2410/00: Microphones - H04R 2410/03: Reduction of intrinsic noise in microphones - H03F: AMPLIFIERS - 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) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) ## Abstract A computer sound card includes a power supply noise isolation circuit for reducing ground plane noise generated during application of heavy electrical loads to the power supply, such as loads presented by computer GPUs. The power supply isolation circuit isolates the output ground from the ground presented from the power supply to the isolation circuit input. The isolation circuit in one embodiment includes switching circuitry and a transformer to reduce the power supply ripple noise that might otherwise be introduced by the power supply into an amplifier such as a microphone preamp. In some embodiments a differential amplifier stage is added to the output of the microphone preamp stage to further reduce noise, such as common mode noise. ## Claims ### Claim 1 An audio processing system for use with a computing device, the system comprising: an isolation block between a microphone preamp circuit and a power supply of the computing device, the isolation block configured to receive a supply signal comprising a positive voltage and a first ground reference from a power supply connector of the computing device, the isolation block configured to reduce power supply noise present in the supply signal by providing at an output a positive output voltage and a second ground reference, the second ground reference of a microphone preamp circuit being isolated and different from the first ground reference of the power supply, resulting in an isolated low noise power supply to minimize the voltage ripple noise and provide a clean voltage that is applied to the microphone preamp circuit to prevent amplification by the microphone preamp circuit; the microphone preamp circuit configured with one input receiving a microphone signal, a second input at the second ground voltage, and an output signal; and a digital signal processor block configured to receive the microphone preamp output signal, convert it to a digital format, and to transmit the digitized microphone preamp output signal to a computer bus on the computing device, wherein the computer bus comprises a third ground reference isolated and different from the first ground reference and the second ground reference. ### Claim 2 (depends on 1) The system as recited in claim 1 wherein the computing device is one of a notebook computer or a desktop computer. ### Claim 3 (depends on 1) The system as recited in claim 1 wherein the power supply connector is a PCIe Power Socket and the computer bus is a PCIe bus. ### Claim 4 (depends on 1) The system as recited in claim 1 further comprising a differential amplifier connected between the microphone preamp and the digital signal processor block and wherein the differential amplifier is configured to remove common mode noise from the microphone preamp output signal. ### Claim 5 (depends on 4) The system as recited in claim 4, wherein the differential amplifier is grounded to the third ground reference. ### Claim 6 (depends on 1) The system as recited in claim 1 wherein the isolation block comprises a switching circuit, a rectifier block and a transformer. ### Claim 7 (depends on 6) The system as recited in claim 6 wherein the switching circuit comprises a push-pull configuration. ### Claim 8 (depends on 1) The system as recited in claim 1, wherein the digital signal processor block is grounded to the third ground reference. ### Claim 9 A method for reducing noise in a microphone circuit comprising the steps of: receiving, by an isolation block, a supply signal from a power supply, the supply signal comprising a positive voltage and a first ground reference, wherein the isolation block is between a microphone preamp circuit and a power supply of a computing device; isolating a low noise power supply from a noisy power supply to reduce power supply noise present in the supply signal by providing at an output a positive output voltage and a second ground reference of the microphone preamp circuit, the second ground reference being isolated and different from the first ground reference of the power supply to minimize the voltage ripple noise and provide a clean voltage that is applied to the microphone preamp circuit to prevent amplification by the microphone preamp circuit; configuring the microphone circuit to receive power from the low noise power supply; and configuring a digital signal processor block to receive a microphone preamp output signal from the microphone preamp circuit, to convert the microphone preamp output signal to a digital format, and to transmit the digitized microphone preamp output signal to a computer bus on the computing device, wherein the computer bus comprises a third ground reference isolated and different from the first ground reference and the second ground reference, and the digital signal processor block is grounded to the third ground reference. ### Claim 10 (depends on 9) The method as recited in claim 9 wherein the isolating the low noise power supply comprises isolating with a switching circuit and a transformer. ### Claim 11 (depends on 10) The method as recited in claim 10 further comprising applying the microphone microphone preamp output signal to a differential amplifier to reduce common mode noise, and the differential amplifier is grounded to the third ground reference. ### Claim 12 A computer audio card for coupling to a computing device, comprising: an auxiliary power socket configured to receive an auxiliary power connector supplying supplemental power from the computing device power supply; a microphone preamplifier configured to receive a microphone signal and amplifying it before transmission to an analog to digital converter (ADC); an isolation block between the microphone preamplifier and a power supply, the isolation block configured for conditioning the supplemental power by isolating the supplemental power from power delivered to the microphone preamplifier, the isolation block further configured to receive a supply signal comprising a positive voltage and a first ground reference, the isolation block configured to reduce power supply noise present in the supply signal by providing at an output a positive output voltage and second ground reference, the second ground reference of a microphone preamplifer being isolated and different from the first ground reference of the power supply, resulting in an isolated low noise power supply to minimize the voltage ripple noise and provide a clean voltage that is applied to the microphone preamplifer to prevent amplification by the microphone preamplifer; and a digital signal processing block configured for receiving a digital signal from the ADC, processing the digital signal, the digital signal processing block is further configured to transmit the processed digital signal to a computer bus coupled to the computing device, the computer bus comprises a third ground reference isolated and different from the first ground reference and the second ground reference, and the digital signal processor block is grounded to the third ground reference. ### Claim 13 (depends on 12) The computer audio card recited in claim 12 further comprising a microphone differential amplifier connected between the microphone preamplifier and the ADC in a microphone path for removing common mode noise. ### Claim 14 (depends on 13) The computer audio card recited in claim 13 wherein the microphone amplifier is connectable to a microphone via an input jack. ### Claim 15 (depends on 14) The computer audio card recited in claim 14 wherein the microphone input jack is located on an external audio control module. ### Claim 16 (depends on 13) The computer audio card recited in claim 13, wherein the microphone differential amplifier is configured to receive a differential microphone signal from the microphone preamplifer and configured to transmit a noise reduced output signal to the ADC. ### Claim 17 (depends on 16) The computer audio card recited in claim 16, wherein the microphone differential amplifier is grounded to the third ground reference. ### Claim 18 (depends on 12) The computer audio card recited in claim 12 wherein the computing device is a desktop computer, the computer bus is a PCI Express bus, the auxiliary power connector is an auxiliary PCIe power connector, and the auxiliary power socket is configured to receive the auxiliary PCI Express power connector.