1. Introduction to Smart Speakers

Smart speakers are electronic devices that integrate multiple functions such as audio playback, voice interaction, and intelligent control. They are usually composed of speaker units, audio processing chips , microphones, wireless communication modules (such as Bluetooth, Wi-Fi), power management units, etc. In terms of appearance, smart speakers come in various shapes and sizes. Some are small and portable, suitable for outdoor use; some are designed as home decorations and placed in living rooms, bedrooms, etc., to provide users with music playback and voice assistant (such as checking the weather, setting reminders, controlling smart home devices, etc.) services.

 2. The role of smart speakers

1. Audio playback : can play music, audiobooks, radio, etc. Users can use voice commands to request singers' songs, music type playlists or listen to radio programs.

2. Voice interaction : Relying on voice recognition technology to understand commands, such as checking weather, stocks, news, setting reminders, alarms, conversions, translations, etc.

3. Smart home control : Connected to smart devices at home, users can use voice to control smart lights, curtains, air conditioners and other appliances to create a convenient home environment.

3. Application of MOS tubes in smart speakers

Audio power amplification :

The weak signal output by the audio processing chip is amplified by a complementary symmetrical circuit composed of MOS tubes (such as power MOSFET). The N-channel MOS tube works in the positive half cycle, and the P-channel MOS tube works in the negative half cycle, which synergistically amplifies the signal to the strength of driving the speaker, and restores high-fidelity sound quality with high linearity, making the details of classical music appear in every detail.

Power Management :

When playing music, the MOS tube provides stable power supply for the audio, processing chip, and wireless module, and the volume is adjusted dynamically as needed. When in standby mode, the power supply of most circuits is cut off, and only a weak power supply is maintained for the voice wake-up circuit. Once the wake-up command is detected, the entire circuit is quickly turned on, and the power consumption is extremely low.

Wireless communication module :

In the Bluetooth or Wi-Fi communication module, MOS controls power supply and signal transmission. It ensures stable power supply and anti-interference when connected; it sets low power consumption mode when there is no audio transmission, and quickly resumes when needed to ensure smooth communication.

4. Key points for selecting MOS tubes in smart speakers

 Electrical parameters

Withstand voltage (VDS) : The common power supply voltage of smart speakers is in the range of 5-12V. However, when the circuit is running, the voltage may rise suddenly due to power fluctuations, instantaneous pulses, etc. To avoid MOS tube breakdown and damage, products with a withstand voltage of 20-30V should be selected to ensure stable operation in complex electrical environments.

Current carrying capacity (ID) : Determine the current demand based on the power of the smart speaker. Taking a 20W speaker with a 12V power supply as an example, the maximum current can be calculated through the power formula. In actual selection, a margin should be reserved. Select a MOS tube with an ID greater than 2A to provide sufficient and stable current for the audio power amplifier circuit to ensure strong and powerful sound output.

On-resistance (RDS (on)) : In the audio power amplification link, on-resistance is directly related to power loss and heat generation. Smaller RDS (on) can reduce energy consumption, improve power efficiency, and make circuit performance better and operation more stable. Therefore, it is best to use MOS tubes with RDS (on) less than 100mΩ to avoid excessive heating that affects sound quality and component life.

Threshold voltage (Vth) : Smart audio control circuits are generally powered by 3.3V or 5V, and the MOS tube threshold voltage needs to be adapted to it. Selecting a 1-3V MOS tube can ensure accurate and reliable conduction and cutoff under the control signal, without the need for additional drive voltage, reducing the difficulty and cost of circuit design, and making system integration more convenient.

Performance characteristics

Switching speed : Smart audio amplification, power management and wireless communication modules all require MOS tubes to switch frequently and quickly. In particular, audio signals are rich in high-frequency components, and the switching time must reach nanoseconds to accurately amplify high-frequency details and achieve high-fidelity sound effects. At the same time, the fast switching characteristics can improve power management efficiency, speed up wireless communication response speed, and optimize audio performance in all aspects.

Noise characteristics : Sound quality is one of the core competitiveness of smart speakers. As a key component, the noise characteristics of MOS tubes cannot be ignored. In particular, the audio power amplifier circuit uses low-noise tubes with a noise coefficient of less than 1dB to minimize the introduction of additional noise, making music and voice clear and pure, bringing immersive listening enjoyment to users.

Input impedance : At the front end of the audio amplifier circuit, the signal is weak. The MOS tube with high input impedance (megaohm level) can reduce the load impact on the front-stage circuit, efficiently receive, transmit and amplify the audio signal, ensure that the sound details are fully preserved and presented to the audience in their original form.

Reliability and security

Temperature characteristics : When the smart speaker is working, the MOS tube of the audio power amplifier circuit generates significant heat. Therefore, it is necessary to select products with an operating temperature range of -40℃ to 85℃, and the electrical parameter drift should be extremely small at high temperatures to ensure stable operation under different ambient temperatures. At the same time, combined with heat dissipation measures such as heat sinks, heat can be dissipated in time to prevent failures caused by overheating and extend the service life of the MOS tube.

Reliability testing and certification : To ensure the long-term stable operation of smart speakers, the selected MOS tubes must undergo strict reliability testing, including high temperature aging, temperature cycling, humidity testing, etc. In addition, products that have passed relevant industry certifications such as electronic component reliability certification standards should be given priority. With the endorsement of authoritative certification, the probability of audio problems caused by MOS tube failures can be greatly reduced, allowing users to use without worries.

VBsemi's MOSFET products rely on excellent electrical performance, reliable stability and a variety of model options. They not only inject surging power into smart speakers, achieve stunning audio playback effects and intelligent power management, and promote the smart speaker industry to a new height, but also take root in many fields such as 3C digital and smart home. At the same time, the company continues to innovate and forge ahead, carefully building a high-quality service system for customers, meeting the needs of all walks of life, and helping technological innovation and product upgrades.