Earphone Line Control Circuit PWM Button Detection
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Solution Overview
Problem
Wire control earphones using resistor dividers generate harsh POP noise when buttons are pressed during calls, affecting call quality due to changes in microphone bias voltage.
Innovation Solution
The use of pulse-width modulation (PWM) signals with different frequencies to convey button information, avoiding noise by attenuating and amplifying these signals within the earphone and mobile terminal circuits, allowing for precise button detection and execution of corresponding functions without disrupting voice signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a resistor divider is used to detect buttons in wire control earphones, then button detection function is achieved, but POP noise is generated when buttons are pressed during calls due to microphone bias voltage changes
Solution Approach 1:
The patent replaces the traditional resistor divider detection mechanism with a capacitor-based detection mechanism. The capacitor couples the button detection circuit to the microphone bias voltage line, allowing button presses to be detected through capacitive coupling rather than direct resistive division. This substitution prevents the microphone bias voltage from changing during button presses, thereby eliminating POP noise while maintaining button detection functionality.
Solution Approach 2:
The patent introduces a capacitor as an intermediary element between the button detection circuit and the microphone bias voltage line. This capacitor acts as a coupling element that allows the button detection signal to pass through while blocking the direct connection that would cause bias voltage changes. The intermediary capacitor thus mediates between the button detection function and the microphone operation, preventing harmful interactions.
2Device complexity
If traditional button detection methods are used, then simple circuit structure is maintained, but call quality deteriorates due to noise interference
Solution Approach 1:
The patent substitutes the traditional resistor divider circuit with a capacitor-based detection circuit. This replacement maintains relative circuit simplicity while dramatically improving call quality by eliminating the POP noise that degraded reliability. The capacitor-based approach achieves both goals: keeping the circuit structure manageable while ensuring reliable, noise-free call performance.
3Ease of manufacture
If resistor divider is used for button detection, then circuit implementation is straightforward, but button detection precision is insufficient
Solution Approach 1:
The patent replaces the resistor divider detection system with a capacitor-based detection system that offers superior detection precision. The capacitor coupling method provides better signal isolation and reduced noise interference, resulting in more accurate button detection. While the implementation approach changes, it remains straightforward and manufacturable, thus improving precision without sacrificing ease of manufacture.
Data Source
AI summary
An earphone wire control circuit and wire control method for a mobile terminal. The wire control circuit includes a circuit in the earphone and a circuit in the mobile terminal which are coupled via a signal wire. The circuit in the earphone includes a micro controller unit and an attenuation and microphone circuit coupled to the micro controller unit of the earphone. The circuit in the mobile terminal includes an audio analog input channel and an amplifier which are coupled in parallel. The amplifier is coupled to a micro controller unit of the mobile terminal via a wire. The micro controller unit of the mobile terminal is coupled to a central processing unit of the mobile terminal via a wire. The micro controller unit of the earphone includes a button detection module and a pulse-width modulation module.