CN-121985257-A - Microphone anti-interference circuit applied to wireless camera

CN121985257ACN 121985257 ACN121985257 ACN 121985257ACN-121985257-A

Abstract

The invention belongs to the technical field of microphones and discloses a microphone anti-interference circuit applied to a wireless camera, which comprises a main control SoC, a microphone interface J1 and an anti-interference front-end network arranged between the main control SoC and the microphone interface J1, wherein the front-end network comprises a microphone signal node, a bias power supply branch, a blocking capacitor C60, a ground bypass suppression unit and an electrostatic protection device D2, a microphone bias voltage end of the bias power supply branch is connected with the microphone signal node through a series current limiting resistor, the blocking capacitor C60 is arranged between the microphone signal node and a signal network MICP in series, the ground bypass suppression unit is formed by capacitors arranged between the microphone signal node and a system ground in parallel, and the electrostatic protection device D2 is arranged between the microphone signal node and the system ground in parallel. According to the invention, through establishing a multi-branch ground bypass network and combining with electrostatic clamping, the release of radio frequency interference components and the suppression of transient overvoltage are realized, and the sound pickup noise is reduced.

Inventors

LIU DONGSHENG
LIU GUOPING
CHEN XIAOMING
YI JINHONG

Assignees

东莞市乔安智联科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260209

Claims (6)

1. Microphone anti-interference circuit for wireless camera, characterized by comprising: the anti-interference front-end network is arranged between the microphone interface J1 and the master control SoC; the anti-interference front-end network comprises a microphone signal node, a bias power supply branch, a direct-isolation coupling unit, a ground bypass suppression unit and an electrostatic protection unit; The bias power supply branch circuit comprises a microphone bias voltage end and a series current limiting resistor, and the microphone bias voltage end is connected with a microphone signal node through the series current limiting resistor; the blocking coupling unit comprises a blocking capacitor C60, and the blocking capacitor C60 is arranged between a microphone signal node and a signal network MICP in series; the ground bypass suppression unit comprises a capacitor C61, a capacitor C439, a capacitor C440 and a capacitor C441, wherein the capacitor C61, the capacitor C439, the capacitor C440 and the capacitor C441 are all arranged between a microphone signal node and system ground in parallel; The electrostatic protection unit comprises an electrostatic protection device D2, and the electrostatic protection device D2 is arranged between the microphone signal node and the system ground in parallel.
2. The microphone anti-interference circuit of claim 1, wherein the pick-up end of the microphone interface J1 is a first pin, the first pin is connected to a microphone signal node, and the reference end of the microphone interface J1 is a second pin, the second pin is connected to the ground, so that the electret microphone forms a pick-up loop with the system ground as a reference and provides a reference ground return path for the microphone signal node.
3. The microphone anti-interference circuit for a wireless camera according to claim 2, wherein the microphone interface J1 further comprises a first shielding end and a second shielding end, wherein the first shielding end and the second shielding end are both grounded in a system to provide a shielding grounding path for the microphone interface and reduce the influence of external electromagnetic coupling on a pickup link.
4. The microphone anti-interference circuit for a wireless camera according to claim 1, wherein the master SoC is provided with an analog audio input pin MICLP, and the analog audio input pin MICLP is connected to the blocking capacitor C60 through a signal network MICP, so that the ac component of the pickup signal coupled by the blocking capacitor C60 is input to the analog audio input pin MICLP through the signal network MICP for sampling.
5. The microphone anti-interference circuit of claim 1 wherein the bias supply branch further comprises a filter regulated capacitor C64, the filter regulated capacitor C64 being disposed in parallel between the microphone bias voltage terminal and system ground to decouple the microphone bias voltage terminal and to inhibit coupling of bias branch ripple and transient disturbances to the microphone signal node.
6. The microphone anti-interference circuit for a wireless camera according to claim 1, wherein the ground bypass suppression unit shares a microphone signal node with the electrostatic protection unit to provide a ground bypass path for radio frequency interference components at the microphone signal node and a ground clamp path for abnormal voltages.

Description

Microphone anti-interference circuit applied to wireless camera Technical Field The invention relates to the technical field of microphones, in particular to a microphone anti-interference circuit applied to a wireless camera. Background The existing wireless monitoring cameras are generally integrated with a WiFi module and/or a cellular communication module, and are matched with a radio frequency front end and an antenna structure. In order to meet the requirements of volume and cost, the antenna, the main control processor and the audio acquisition circuit are often compactly arranged on the same main board or adjacent board cards, the microphone pickup link is also usually connected to the audio input end of the main control SoC in a high-impedance and low-amplitude analog mode, the electret microphone needs to be powered by the bias branch circuit, and the signal node and the bias node are sensitive to external electromagnetic disturbance. In the working process of the camera, the scenes of WiFi connection, code stream uplink, link reconnection, cellular network residence, switching and the like can cause periodic or sudden changes of antenna radio frequency emission. The radio frequency energy is easily coupled into a microphone signal node, an offset power supply branch or a ground reference network in a space radiation, near-field coupling or wire conduction mode, and detection rectification occurs in a nonlinear structure of a microphone body, an ESD structure or a main control input end, so that the high-frequency radio frequency component is converted into envelope noise or low-frequency disturbance of an audible frequency band. Thus, the pickup link may present abnormal noise such as galvanic sounds, pop sounds, or whip-like sounds associated with the wireless communication state, reducing the reliability of speech intelligibility and remote intercom, evidence collection. Especially when the distance between the antenna and the microphone is relatively short, the board-level layout is dense, and the ground reflux path is complex, the problem is more remarkable, the interference frequency band is changed along with the change of the communication system, and the single device or the single frequency band inhibition mode is difficult to meet the requirement of multiple working conditions. In view of the above, the present invention provides a microphone anti-interference circuit applied to a wireless camera to solve the above-mentioned problems. Disclosure of Invention In order to overcome the defects in the prior art, the invention provides the following technical scheme that the microphone anti-interference circuit applied to the wireless camera comprises: the anti-interference front-end network is arranged between the microphone interface J1 and the master control SoC; the anti-interference front-end network comprises a microphone signal node, a bias power supply branch, a direct-isolation coupling unit, a ground bypass suppression unit and an electrostatic protection unit; The bias power supply branch circuit comprises a microphone bias voltage end and a series current limiting resistor, and the microphone bias voltage end is connected with a microphone signal node through the series current limiting resistor; the blocking coupling unit comprises a blocking capacitor C60, and the blocking capacitor C60 is arranged between a microphone signal node and a signal network MICP in series; the ground bypass suppression unit comprises a capacitor C61, a capacitor C439, a capacitor C440 and a capacitor C441, wherein the capacitor C61, the capacitor C439, the capacitor C440 and the capacitor C441 are all arranged between a microphone signal node and system ground in parallel; The electrostatic protection unit comprises an electrostatic protection device D2, and the electrostatic protection device D2 is arranged between the microphone signal node and the system ground in parallel. Further, the pick-up end of the microphone interface J1 is a first pin, the first pin is connected with a microphone signal node, the reference end of the microphone interface J1 is a second pin, and the second pin is grounded in a system, so that the electret microphone forms a pick-up loop by taking the system ground as a reference and provides a reference ground return path for the microphone signal node. Further, the microphone interface J1 further includes a first shielding end and a second shielding end, where both the first shielding end and the second shielding end are grounded in a system, so as to provide a shielding grounding path for the microphone interface and reduce the influence of external electromagnetic coupling on the pickup link. Further, the master SoC is provided with an analog audio input pin MICLP, and the analog audio input pin MICLP is connected with the blocking capacitor C60 through the signal network MICP, so that the pickup signal ac component coupled by the blocking capacitor C60 is input to the