Headphones PCBA

The headphone PCBA (printed circuit board assembly) is the core electronic control unit of the headphone, which is mainly responsible for audio signal processing, wireless connection, power management and interactive control. The following is an introduction from the aspects of function, composition, technical characteristics, etc.:

Core functions

• Audio signal processing: Decode Bluetooth/wired input audio data, drive the speaker to sound through the amplification circuit, and support noise reduction, EQ sound effect adjustment and other functions.

• Wireless connection and transmission: Realize Bluetooth pairing, audio encoding and decoding (such as SBC, AAC, aptX and other protocols), and some high-end models support LDAC, aptX Lossless lossless transmission.

• Power and battery life management: Charge the lithium battery, control power consumption (such as standby sleep, automatic shutdown), and feedback the remaining battery life through the power display.

• Interactive control: Respond to touch/button commands (such as switching songs, calls, and noise reduction mode switching). Some models support voice assistant wake-up (such as Siri and Xiao Ai).

Main components

• Main control chip/Bluetooth SoC: core processor, integrated Bluetooth module, audio decoding chip (such as Qualcomm QCC series, Hengxuan BES chip), running firmware program.

• Audio amplifier circuit: including power amplifier (AMP), filter capacitor, etc., amplifies the decoded audio signal and drives the speaker (such as 40mm dynamic unit).

• Noise reduction processing module: Active noise reduction (ANC) models integrate noise reduction chips (such as Knowles SPU), with microphones to pick up ambient sound and generate reverse sound waves to cancel noise.

• Power management unit (PMU): integrated charging IC, overcharge protection circuit, support Type-C interface fast charging, some models have wireless charging receiving coil circuit.

• Microphone and sensor: call microphone, ambient sound microphone (for noise reduction), as well as distance sensor (automatically pause when taking off the headphones), acceleration sensor (detect wearing status).

• Interface and storage components: Bluetooth antenna, storage chip (used to save pairing information, sound effect settings), some wired models retain 3.5mm interface circuit.

Technical features

• Low-power Bluetooth design: Using Bluetooth 5.2/5.3 protocol, with power saving mode (such as Idle state current <1mA), the battery life is extended to more than 30 hours.

• High-fidelity audio processing: High-end PCBA supports 96kHz/24bit audio decoding, and improves sound quality through low-distortion op amps (such as OPA series) and independent DAC chips.

• Compact integration and anti-interference: Due to the limited internal space of headphones, PCBA mostly adopts multi-layer board design, and metal shielding covers are used to reduce the interference of Bluetooth signals on audio.

• Noise reduction algorithm and hardware collaboration: The active noise reduction effect (such as -40dB) depends on the cooperation of the microphone array, noise reduction chip and firmware algorithm on the PCBA, and the delay needs to be accurately controlled (<20ms) to avoid ear pressure discomfort.

Application scenarios

• Consumer-grade music headphones: Support Bluetooth connection and basic noise reduction, PCBA cost control priority, and adapt to mass users (such as single-chip solutions for 100-yuan models).

• Professional noise-canceling headphones: The PCBA of high-end models (such as Bose and Sony) integrates a multi-microphone noise-canceling array and an independent audio processing chip, focusing on noise reduction depth and sound quality restoration.

• Gaming headphones: The PCBA adds a low-latency mode (such as Bluetooth gaming mode delay <80ms) and a 7.1-channel virtual surround sound processing circuit to adapt to e-sports scenarios.

• Bone conduction/special headphones: The PCBA of bone conduction headphones needs to drive the vibration unit, and the circuit design focuses on vibration frequency control (such as 100-300Hz frequency band optimization), which is different from the traditional dynamic speaker driving method.

Differences from other PCBAs

The core challenge of the PCBA of headphones lies in the multi-task coordinated optimization of audio-Bluetooth-power supply, especially high-end models need to balance noise reduction effect, sound quality fidelity and battery life (such as when ANC and lossless Bluetooth are turned on at the same time, the power consumption is controlled within 50mA). In addition, its hardware design needs to adapt to the mechanical actions of the head-mounted structure such as folding and rotation to avoid cable bending and damage (FPC flexible circuit boards are often used to connect the left and right ear PCBAs).