author:
Benwei Xin, Marketing Business Manager, Texas Instruments (TI)
Wenchau Albert Lo, Personal Electronics System Engineer, Texas Instruments (TI)
The competition in the smart speaker industry is becoming increasingly fierce, and major manufacturers are vying to develop more powerful and more convenient products. Today's smart speakers have rich functions such as voice interaction, artificial intelligence, smart home control, and multimedia playback. To take the lead in the competition, the design of smart speakers must have advantages in terms of overall system cost, battery life, thermal effects, echo cancellation, and sound quality.
Total system cost
Reducing system costs is the top priority of the entire smart home industry. In the smart speaker design, the designer is most likely to reduce the system cost through the audio amplifier. The audio design team of Texas Instruments (TI) did not sacrifice sound quality performance in exchange for system cost, but took a different approach and developed a series of solutions around audio amplifiers that can improve performance while reducing system costs.
For example, for audio systems below 10 W, TI's electromagnetic interference suppression technology replaces inductors with ferrite beads. The average cost of 4 inductors is US$0.16, while the average cost of 4 ferrite beads is only US$0.04. In this way, with this item alone, the designer can save an average of US$0.12 in a two-channel system.
Battery life and thermal effects
Small size batteries can make smart speakers smaller, lighter, and more portable. The higher efficiency and optimized thermal effect not only help reduce the battery size, but also maintain the battery's endurance.
Microphones and system-on-chip (SoC) are the main power-consuming components, but they need to continuously listen to instructions. Therefore, to reduce standby power and heat dissipation, designers must start from other aspects. .
Starting with an audio amplifier is one of the ideal choices, because in addition to the SoC, it has the highest standby power consumption and the largest heat dissipation. To reduce standby power consumption, the use of a hybrid modulation module audio amplifier can adjust the duty cycle of the output pulse width modulation and control the current from the inductor to the speaker, thereby reducing the idle current by 50%. In this way, the overall power consumption can be reduced, the heat dissipation can be optimized, and the battery life can be extended without increasing the battery size.
Echo cancellation
The accuracy of speech recognition will affect the performance of the virtual assistant and is also an important indicator of the performance of smart speakers. One of the challenges is that the microphone will pick up a variety of environmental noises, including other electrical appliances, human conversations, and even music being played by smart speakers. In order to filter environmental noise and more accurately recognize the user's voice commands, smart speakers should be equipped with multiple microphones and use comprehensive technology to achieve accurate voice recognition.
One of the technologies is echo cancellation, which can identify the digital signal of the music being played, and then remove the signal from the microphone input. Echo cancellation digitally eliminates all background noise, including music. In order to better filter out environmental noise, the audio amplifier with echo cancellation function has an SDOUT (electronic sound output) signal. As shown in Figure 1, the SDOUT signal is fed into the SoC to filter out the music signal received by the microphone.
Figure 1: Block diagram of echo cancellation system
High sound quality
The design of the smart speaker is small and beautiful. But the size is smaller, the audio output power will also be reduced. The amplifier with good speaker protection function can increase the volume output of the speaker without compromising the sound quality. Using algorithms and models, the speaker protection amplifier can analyze the input music signal, and then provide a peak output power that is 5 times the rated power of the speaker, and finally achieve two to three times the output volume amplification effect without affecting the sound effect of the speaker. In this way, smart speakers with a small form factor can also achieve high-quality sound effects.
What is the next opportunity?
In addition to adding voice interaction functions to traditional speakers, another focus of the smart speaker market is to achieve high-fidelity sound. Although most Bluetooth® speakers on the market currently do not have voice recognition or voice interaction functions, in the near future, Bluetooth plus voice recognition and voice interaction will become the market standard.
Portable smart speakers with batteries need to achieve the same power as line-powered speakers, which will become the next opportunity for smart speaker design.
In the past 10 years, the speaker design has slowly evolved from large and household type to smaller, portable and smarter personal applications. In this process, Texas Instruments has provided a large number of technology and system solutions to realize smart speakers. Longer battery life, better sound quality experience, stable connectivity and fast charging effect, and reduce the system cost as much as possible for customers. Figure 2 shows the block diagram of the smart speaker system of Texas Instruments, which can be used for quick system selection And design.
Figure 2: TI smart speaker system block diagram
Guangzhou Yuehang Audio Technology Co., Ltd , https://www.yhspeakers.com