Multi-microphone direct wired active noise reduction circuit structure for headphones
By employing a multi-microphone direct-connection active noise cancellation circuit in headphones and utilizing the MCU's built-in bias voltage source to eliminate external coupling capacitors, the problems of signal distortion and high cost of traditional circuits are solved, achieving a more efficient noise cancellation effect.
Patent Information
- Application Number
- CN202521748950.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-18
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2035-08-18
AI Technical Summary
Traditional noise-canceling microphone circuits for existing headphones suffer from nonlinear distortion, low-frequency cutoff due to capacitive coupling, and issues such as occupying PCB space and increasing costs.
The circuit adopts a multi-microphone direct-connection active noise cancellation circuit structure, utilizes the built-in programmable bias voltage source of the MCU, eliminates the need for external coupling capacitors, and directly connects the microphone power supply pin to the MCU bias voltage output pin, thus simplifying the circuit structure.
It reduces signal distortion, simplifies circuit design, improves the signal-to-noise ratio, reduces costs, and enhances noise reduction performance.
Smart Images
Figure CN224684348U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of headphones, and in particular to a multi-microphone direct-connection active noise cancellation circuit structure for headphones. Background Technology
[0002] Active noise cancellation (ANC) technology cancels noise by generating sound waves that are out of phase with ambient noise, and has become a core function of high-end headphones. Currently, the mainstream solutions fall into two categories: 1. Feedforward ANC: Microphones are placed on the outside of the earcups to collect ambient noise. It is suitable for canceling mid-to-high frequency noise (>1kHz), but is not sensitive to noise inside the ear canal; 2. Feedback ANC: Microphones are placed on the inside of the earcups to monitor residual noise. It excels at handling low-frequency noise (<500Hz), but is prone to causing feedback.
[0003] Later, some companies in the industry adopted hybrid noise cancellation (Hybrid ANC), combining the advantages of both feedforward ANC and feedback ANC. For example, in the existing technology, the circuit structure of a pair of Bluetooth noise-canceling headphones uses both feedforward and feedback noise cancellation modules to achieve dual-feed active noise cancellation and thus better noise reduction. However, it still uses the traditional noise-canceling microphone circuit of headphones: "noise signal—MIC—TVS capacitive coupling chip," which has some shortcomings, such as: 1. TVS introduces nonlinear distortion, and capacitive coupling causes low-frequency cutoff; 2. External coupling capacitors and bias resistors are required, which occupy PCB space and increase costs.
[0004] Therefore, a new technical solution needs to be researched to address the above problems. Utility Model Content
[0005] In view of this, the present invention addresses the deficiencies of the existing technology and its main objective is to provide a multi-microphone direct-connection active noise cancellation circuit structure for headphones, which adopts capacitor-free direct-connection bias, reduces distortion sources, simplifies the circuit, and improves the signal-to-noise ratio.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A multi-microphone direct-connect active noise cancellation circuit structure for headphones includes an MCU, five MEMS microphones, and a DC-DC power management chip; The MCU has five ADC input channels, a VBAT output pin, an HPVDD input pin, a bias voltage output pin, and a data output pin. The five MEMS microphones include a left feedforward microphone, a right feedforward microphone, a left rear feedforward microphone, a right rear feedforward microphone, and a call microphone. The power supply pins of each microphone are directly connected to the bias voltage output pin of the MCU. The outputs of the left and right feedforward microphones are directly coupled to the MCU's ADC input channel. The outputs of the left and right rear feedforward microphones are connected to the MCU's ADC input channel without external coupling capacitors. The output of the call microphone is connected to the MCU's ADC input channel without external coupling capacitors. The DC-DC power management chip has a VIN input pin, an FB pin, an LX pin, and an EN pin. The VIN input pin of the DC-DC power management chip is connected to the VBAT output pin of the MCU. The LX pin outputs voltage and is connected to the HPVDD input pin of the MCU. The FB pin collects the output voltage signal. The data output pin of the MCU is connected to the EN pin.
[0007] As a preferred embodiment, the DC-DC power management chip is TMI3101.
[0008] As a preferred option, at least the call microphone should be a microphone with built-in TVS electrostatic protection.
[0009] As a preferred embodiment, the MCU also has two pairs of differential audio output pins and drives the speaker through an anti-interference circuit.
[0010] As a preferred embodiment, the anti-interference circuit includes: a ferrite bead connected in series between the differential audio output pin and the speaker, and a capacitor connected in parallel between the output terminal of the ferrite bead and ground.
[0011] As a preferred embodiment, the speaker is equipped with an ESD protection diode.
[0012] As a preferred embodiment, the MCU also includes a clock input pin I and a clock output pin, which are connected to a crystal oscillator respectively.
[0013] As a preferred embodiment, the MCU is further provided with V+ pin, V- pin, POWER pin, and ANC pin. The MCU is connected to a multi-function button group, which is equipped with an ESD electrostatic protection diode.
[0014] As a preferred embodiment, the MCU is also connected to a rechargeable battery circuit, a battery charging management circuit, and a TYPE-C charging management circuit; the TYPE-C charging management circuit, the battery charging management circuit, and the rechargeable battery circuit are connected sequentially and respectively connected to the MCU; the TYPE-C charging management circuit is equipped with a USB Type-C interface, which is multiplexed as follows: The charging input port is coupled to the charging management circuit via an overvoltage protection circuit. The digital audio input port is coupled to the MCU's USB audio channel via a D+ / D data cable.
[0015] As a preferred embodiment, the TYPE-C charging management circuit is equipped with an ESD electrostatic protection diode.
[0016] Compared with the prior art, this utility model has significant advantages and beneficial effects. Specifically, as can be seen from the above technical solution, it mainly achieves direct bias without external coupling capacitors by directly connecting the power supply pins of each microphone to the bias voltage output pin of the MCU; the outputs of the left and right feedforward microphones are directly coupled to the ADC input channels of the MCU; the outputs of the left and right feedforward microphones are connected to the ADC input channels of the MCU without external coupling capacitors; and the output of the call microphone is connected to the ADC input channel of the MCU without external coupling capacitors. In this way, capacitor-free direct bias is achieved, utilizing the built-in programmable bias voltage source of the MCU to eliminate external coupling capacitors, reduce distortion sources, simplify the circuit, and improve the signal-to-noise ratio.
[0017] To more clearly illustrate the structural features and effects of this utility model, the following detailed description of this utility model is provided in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description
[0018] Figure 1 This is a schematic block diagram of the multi-microphone direct-connection active noise cancellation circuit structure of a headset according to an embodiment of the present invention. Figure 2 This is a detailed circuit diagram of the MCU according to an embodiment of the present invention; Figure 3 This is a detailed circuit diagram of DC-DC power management according to an embodiment of the present invention; Figure 4 This is a detailed circuit diagram of the call microphone according to an embodiment of the present invention; Figure 5 This is a detailed circuit diagram of the call microphone according to an embodiment of the present invention; Figure 6 This is a detailed circuit diagram of a loudspeaker according to an embodiment of the present invention; Figure 7 This is a detailed circuit diagram of a crystal oscillator according to an embodiment of the present invention; Figure 8 This is a detailed circuit diagram of the left feedforward microphone and the right feedforward microphone according to an embodiment of this utility model; Figure 9 This is a detailed circuit diagram of the left and right rear feed microphones according to an embodiment of this utility model; Figure 10This is a detailed circuit diagram of the TYPE-C charging management according to an embodiment of this utility model; Figure 11 This is a detailed circuit diagram of a multi-functional keypad assembly according to an embodiment of this utility model; Figure 12 This is a detailed circuit diagram of battery charging management according to an embodiment of the present invention; Figure 13 This is a detailed circuit diagram of the battery according to an embodiment of the present invention; Detailed Implementation Please refer to Figures 1 to 13 As shown, it illustrates the specific circuit structure of an embodiment of this utility model.
[0019] A multi-microphone direct-connect active noise cancellation circuit structure for headphones includes an MCU, five MEMS microphones, and a DC-DC power management chip; The MCU, also known as a microcontroller unit, has five ADC input channels, a VBAT output pin, an HPVDD input pin, a bias voltage output pin (MICLDO), and a data output pin (SDODATA). It is typically responsible for signal processing, mode switching, charging management, and communication with various peripherals. The five MEMS microphones include a left feed-forward microphone (FFL MIC), a right feed-forward microphone (FFR MIC), a left rear-feedback microphone (FBL MIC), a right rear-feedback microphone (FBR MIC), and a talk microphone (Talk MIC). The power supply pin (VDD) of each microphone is directly connected to the bias voltage output pin (MICLDO) of the MCU without external coupling capacitors. The outputs of the left and right feed-forward microphones are directly coupled to the MCU's ADC input channels without external coupling capacitors, and are used to collect external ambient noise, such as... Figure 7 As shown, the power supply pins VDD of the left and right feedforward microphones are directly connected to the MCU's bias voltage output pin MICLDO via resistors R20 and R21, respectively. Capacitors C22 and C23 are connected between their respective power supply pins VDD and GND. The output pins OUT of the left and right rear-feedback microphones are connected to the MCU's ADC input channels without external coupling capacitors, used to monitor residual noise in the ear canal, such as... Figure 8 As shown, the power supply pins VDD of the left and right rear-feed microphones are directly connected to the MCU's bias voltage output pin MICLDO via resistors R22 and R23, respectively. Capacitors C24 and C25 are connected between their respective power supply pins VDD and GND. The output pin OUT of the call microphone is connected to the MCU's ADC input channel without an external coupling capacitor; it is used for directional voice pickup in call scenarios, such as... Figure 4As shown, the power supply pin VDD of the call microphone is directly connected to the bias voltage output pin MICLDO of the MCU via resistor R19. A capacitor C21 is connected between the power supply pin VDD and the GND pin of the call microphone. In this embodiment, five MEMS microphones (2 feedforward + 2 feedback + 1 call microphone) are used. The feedforward microphone (FF) captures external ambient noise, and the feedback microphone (FB) detects residual noise in the ear canal, forming a hybrid active noise cancellation (Hybrid ANC) architecture.
[0020] The DC-DC power management chip has a VIN input pin, an FB pin, an LX pin, and an EN pin. The VIN input pin of the DC-DC power management chip is connected to the VBAT output pin of the MCU. The LX pin outputs a voltage of 1.85V and is connected to the HPVDD input pin of the MCU. The FB pin collects the output voltage signal for feedback adjustment of the 1.85V output voltage. The SDODATA data output pin of the MCU is connected to the EN pin.
[0021] In this embodiment, the DC-DC power management chip is a TMI3101. Specifically, in conjunction with... Figure 2 and Figure 3 As shown, the VIN input pin is also grounded through capacitor C19. The LX pin is connected to inductor L2. The other end of inductor L2 is connected in series with resistors R17 and R18 and then grounded. The FB pin acquires the voltage divider signal of the output voltage and is connected between resistors R17 and R18. The output voltage of 1.85V from the other end of inductor L2 is connected to the HPVDD input pin of the MCU. The other end of inductor L2 is also connected to capacitor C20 and grounded. Capacitor C20 forms a parallel relationship with the series resistors R17 and R18. The EN pin is also connected to resistor R16 and grounded.
[0022] At least the call microphone should be a microphone with built-in TVS electrostatic protection. Preferably, all microphones should be microphones with built-in TVS electrostatic protection.
[0023] like Figure 1 , Figure 2 and Figure 5 As shown, the MCU also has two pairs of differential audio output pins, DACRP / DACRN and DACLP / DACLN, and drives the speaker through an anti-interference circuit. The anti-interference circuit includes: 120Ω ferrite beads (R44, R45, R46, R47) connected in series between the differential audio output pins and the speaker, and 33pF capacitors (C41, C42, C43, C44) connected in parallel between the output terminal of the ferrite beads and ground. The speaker is equipped with ESD protection diodes (ESD26, ESD27).
[0024] like Figure 1 , Figure 2 and Figure 6 As shown, the MCU also has a clock input pin XOSCI and a clock output pin XOSCO, which are connected to a crystal oscillator (Crystal, 24MHz) to provide a precise clock reference for the MCU and ensure the timing stability of digital signal processing.
[0025] like Figure 1 , Figure 2 and Figure 10 As shown, the MCU also has V+ pin, V- pin, POWER pin, and ANC pin, as follows: Figure 1 , Figure 2 and Figure 10 As shown, the MCU is connected to a multi-function button group (KEY*4), which includes physical buttons for power on, volume ±, and ANC mode switching. User commands are input to the MCU via GPIO. The multi-function button group is equipped with ESD protection diodes (ESD4, ESD5, ESD6, ESD7).
[0026] like Figure 1 , Figure 2 ,as well as, Figures 9 to 13As shown, the MCU is also connected to a rechargeable battery circuit, a battery charging management circuit, a TYPE-C charging management circuit, and LEDs (i.e., dual-color status indicator lights, which use red / blue LEDs to indicate charging status, Bluetooth connection, ANC mode, and other working states; the indicator light circuit is also equipped with ESD electrostatic protection diodes (ESD2, ESD3); the NTC thermistor of the rechargeable battery circuit is connected to the battery charging management circuit, and temperature monitoring is achieved through NTC (NTC_DET), with charging and discharging safety managed by the charging chip; the battery charging management circuit includes a charging management chip CL40560 (lithium battery charging management chip), the VIN pin of the charging management chip CL40560 is connected to the VPWR pin of the MCU, and the STAT pin of the charging management chip CL40560 is connected to the FULL pin of the MCU). The DET pin 25 controls the battery charging process (constant current / constant voltage), supports a charging current of 445mA, and detects the full charge status via FULL_DET. The rechargeable battery circuit is connected to the BAT pin of the charging management chip CL40560, and then to the VBAT pin 13 of the MCU. The TYPE-C charging management circuit, battery charging management circuit, and rechargeable battery circuit are connected sequentially and then to the MCU. The TYPE-C charging management circuit has a USB Type-C interface, which is multiplexed as: a charging input port, coupled to the charging management circuit through an overvoltage protection circuit (OVP chip, such as model P14C1S); and a digital audio input port, coupled to the MCU's USB audio channel through D+ / D data lines. The TYPE-C charging management circuit is equipped with ESD protection diodes (ESD8, ESD9, ESD10).
[0027] Furthermore, the signal flow of the above circuit is as follows: MIC array → MCU → speaker SPK_L / R; Type C → OVP → charging chip → battery → MCU; the specific processing flow of noise signals is: ambient noise → FF MIC → ADC channel → MCU algorithm generates inverted wave → DAC output → SPK; residual noise in the ear canal → FB MIC → ADC channel → MCU dynamically adjusts the inverted wave parameters; it integrates a low-noise DAC (driving the speaker) and ADC (acquiring microphone signals), supports differential output (DACRP / DACRN) to improve anti-interference capability, and provides pure analog power through the HPVDD pin. The MCU uses a 24MHz crystal clock for precise timing to perform real-time FFT analysis on the FF / FB microphone signals, dynamically generating an inverted sound wave with the opposite phase and equal amplitude to the noise, which can cover low-frequency noise.
[0028] Furthermore, as described above, this circuit design offers several advantages: the DC-DC circuit (TMI3101) provides a stable 1.85V low-voltage power supply, effectively reducing the noise floor of the analog circuit; the ferrite beads (R44 / R45, etc.) and 33pF capacitors (C41 / C42) can form an RF filter network to suppress interference from the Bluetooth antenna (ANT) on the audio signal. Simultaneously, the microphone circuit omits coupling capacitors (relying on the MCU's built-in bias), reducing signal distortion. Audio differential traces (such as DACL+ / DACL) combined with 120Ω ferrite beads suppress common-mode noise. Multiple ESD protection points (such as ESD1P1G0BH2) cover all buttons / interfaces, enhancing electrostatic discharge tolerance.
[0029] In other embodiments, the noise reduction mode can be switched, and the user can switch the noise reduction mode (such as ambient sound mode) through the ANC button, and the MCU dynamically adjusts the weight of the FF / FB microphone.
[0030] The key design feature of this invention is that it directly connects the power supply pins of each microphone to the bias voltage output pin of the MCU; the outputs of the left and right feedforward microphones are directly coupled to the MCU's ADC input channel; the outputs of the left and right feedback microphones are connected to the MCU's ADC input channel without external coupling capacitors; and the output of the call microphone is connected to the MCU's ADC input channel without external coupling capacitors. In this way, capacitor-free direct biasing is achieved, utilizing the MCU's built-in programmable bias voltage source to eliminate external coupling capacitors, reduce distortion sources, simplify the circuit, and improve the signal-to-noise ratio.
[0031] The above description is merely a preferred embodiment of the present utility model and does not constitute any limitation on the technical scope of the present utility model. Therefore, any minor modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model shall still fall within the scope of the technical solution of the present utility model.
Claims
1. A multi-microphone direct-connection active noise cancellation circuit structure for headphones, characterized in that, Includes an MCU, five MEMS microphones, and a DC-DC power management chip; The MCU has five ADC input channels, a VBAT output pin, an HPVDD input pin, a bias voltage output pin, and a data output pin. The five MEMS microphones include a left feedforward microphone, a right feedforward microphone, a left rear feedforward microphone, a right rear feedforward microphone, and a call microphone. The power supply pins of each microphone are directly connected to the bias voltage output pin of the MCU. The outputs of the left and right feedforward microphones are directly coupled to the MCU's ADC input channel. The outputs of the left and right rear feedforward microphones are connected to the MCU's ADC input channel without external coupling capacitors. The output of the call microphone is connected to the MCU's ADC input channel without external coupling capacitors. The DC-DC power management chip has a VIN input pin, an FB pin, an LX pin, and an EN pin. The VIN input pin of the DC-DC power management chip is connected to the VBAT output pin of the MCU. The LX pin outputs voltage and is connected to the HPVDD input pin of the MCU. The FB pin collects the output voltage signal. The data output pin of the MCU is connected to the EN pin.
2. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 1, characterized in that: The DC-DC power management chip is TMI3101.
3. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 1, characterized in that: At least the call microphone should be a microphone with built-in TVS electrostatic protection.
4. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 1, characterized in that: The MCU also has two pairs of differential audio output pins and drives the speaker through an anti-interference circuit.
5. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 4, characterized in that: The anti-interference circuit includes: a ferrite bead connected in series between the differential audio output pin and the speaker, and a capacitor connected in parallel between the output terminal of the ferrite bead and ground.
6. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 4 or 5, characterized in that: The speaker is equipped with an ESD protection diode.
7. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 1, characterized in that: The MCU also has a clock input pin and a clock output pin, which are connected to a crystal oscillator respectively.
8. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 1, characterized in that: The MCU also has V+ pin, V- pin, POWER pin, and ANC pin. The MCU is connected to a multi-function button group, which is equipped with an ESD electrostatic protection diode.
9. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 1, characterized in that: The MCU is also connected to a rechargeable battery circuit, a battery charging management circuit, and a TYPE-C charging management circuit; the TYPE-C charging management circuit, the battery charging management circuit, and the rechargeable battery circuit are connected in sequence and respectively connected to the MCU; the TYPE-C charging management circuit is equipped with a USB Type-C interface, which is multiplexed as follows: The charging input port is coupled to the charging management circuit via an overvoltage protection circuit. The digital audio input port is coupled to the MCU's USB audio channel via a D+ / D data cable.
10. The multi-microphone direct-connection active noise cancellation circuit structure for headphones according to claim 9, characterized in that: The TYPE-C charging management circuit is equipped with an ESD electrostatic protection diode.