On the importance of smart power audio amplifier to smart phones
Time:2022-06-25
Views:2076
Source: Eric Eklund, product manager, cirrus logic
There seems to be no end to what people consume on smartphones, tablets or other portable devices. With the smart phone screen becoming larger and brighter, and providing a better overall visual experience, consumers are not only experiencing mobile content through headphones, but also experiencing mobile content in a new way. It is common for friends to get together, turn their mobile phones sideways, and use the external speakers of their mobile phones to watch videos and share the experience of watching and listening. Over the years, many mobile phones have grown in screen size, but the audio experience has not always kept pace, especially in "loud" speaker mode. Therefore, more high-end mobile phones offer stereo as an additional function, usually with micro speakers at the top and bottom. Now, when users look at their stereo enhanced phone from the side (i.e. landscape view), they will find a speaker on both sides to help create a better "stereo" listening experience.
The trend of using stereo audio in smart phones and other audio playback devices shows that audio amplifiers play a particularly important role in smart phone design. As a result, audio amplifiers have seen substantial growth in both capacity and Technology (see Figure 1 below). According to SAR insight & Consulting audio power amplifier market growth report 1: "compared with 2010, the market shipment of audio amplifier in 2018 increased by 3 times, which is not only due to the increase in the shipment of audio playback equipment, but also due to the increase in the number of channels per equipment." The report also points out that stereo speakers have been widely used in the high-end smartphone market with a price of more than $550, especially since the iPhone in 2016 ® 7 mobile digital devices since the introduction of stereo. Since then, many other flagship smartphones have also used stereo speakers in their products. The analysis company also predicts that stereo will be extended to mid-range mobile phones priced between $200 and $500. It is estimated that nearly 600million amplifiers will be used in the mid-range market in 2018, and it is expected to increase to nearly 700million by 2023.
Figure 1: overview of the global market for independent horn amplifiers in the terminal market
(source: the first quarter report of 2019 issued by SAR insight & Consulting)
Increasing importance of boost audio amplifier
However, the broad trend to include stereo in smartphones does not necessarily ensure a high-quality audio experience. For this purpose, the micro horn shall also be equipped with an intelligent boost audio amplifier to maximize the loudness of the horn while protecting the horn from damage. Smart phone audio designers should use high-voltage audio amplifier, horn monitoring analog-to-digital converter (ADC) and advanced algorithm to keep micro horn in safe operation state to ensure better, louder and clearer audio sound. In addition, two horns usually mean two amplifiers. Therefore, size, efficiency, battery current management, and audio performance are all twice as important. Therefore, as smart phones move towards stereo, the audio amplifier that did not appear before plays a more important role.
The following is a design list to ensure that the smart boost audio amplifier can play its maximum role.
Size - board space is always a consideration when integrating various functions into portable devices. One option is to place two miniature speakers on the top and bottom of the phone. The audio amplifier must be smaller and more integrated, especially when there are now two. In order to solve the size problem, cirrus logic uses 55nm technology to design its latest cs35l41 intelligent boost amplifier with DSP, making it easier for OEMs to adopt the dual horn design without sacrificing the space required for other new functions.
Efficacy - SAR insight research also confirmed that class D audio amplifiers have almost replaced class AB amplifiers in many markets due to the improved efficiency of class D audio amplifiers. Higher efficiency can also be achieved in the design. For example, cirrus logic‘s 11 volt boost class D amplifier also uses a class H DC-DC converter to enhance supply more efficiently than Class G, while additional battery management systems predictably adapt to changing audio, speaker, and battery conditions to regulate battery current and save power. This emphasizes the evolving technology and "enhancement" role of the boost audio amplifier, as shown in Figure 2.
Figure 2: Class G and class H supply rail voltage vs time
Horn protection - according to SAR insight & consulting, in many applications using small horns, such as smart phones, it has become more and more common for embedded DSPs in amplifiers to use horn protection algorithms. These algorithms can achieve higher output without damaging the horn. For example, the cirrus logic audio amplifier achieves more than 5 watts in a 1-Watt horn. This new boost audio amplifier can provide the power required for higher offset to generate louder and clearer audio, especially on hands-free phones, without damaging the subminiature speakers. The SAR insight report further pointed out that "since 2013, the use of horn protection in mid-range smartphones has grown rapidly, because OEMs want to maximize horn performance and combine it with other enhancements (such as high-end codecs) to achieve differentiated design."
Audio enhancements - even with all these features, not all audio enhancements are the same. In order to produce better definition and enhanced stereo audio to match those vivid, larger screens and visual content, advanced algorithms in integrated DSP should also solve audio design problems, such as equalization, compression and psychoacoustic enhancement, to fine tune audio playback.
As users abandon traditional cable or satellite TV and want to see more unrestricted content, smartphones and other mobile devices are rapidly becoming the main platforms for streaming media and content appreciation. In order to match the clearer and brighter visual experience, more and more mobile phones are shifting from mono or mono audio design to dual channel stereo to provide a better listening experience. With the continuation of this trend, the demand for intelligent power amplifier becomes more and more important. This means that smart phone OEMs will not only seek to save space in the headset and hands-free mode, but also seek to improve energy efficiency and audio clarity, so that their products can stand out in the market competition.
1 the data comes from the audio power amplifier report released by Peter conney, chief researcher of SAR insight & Consulting in the fourth quarter of 2017: market growth, channel number, amplifier type, input type, class and horn protection. The updated data comes from the audio signal chain IC forecast database released by SAR insight & Consulting in the first quarter of 2019.
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