Part I: We need more power!
Do you remember the time when mobile phones were actual phones – without being smart? When you only needed to recharge your battery once a week? Unthinkable today. With the steady increase of features, resulting required processing and thus power consumption, we can be happy when our battery lasts a full day. Daily recharging has become the norm.
This story is similar for all wearable devices due to their purpose of – well, being wearable. The form factor limits the amount of energy that can be carried around. Yes, battery technology and energy density are advancing. But not least since burning phones hit the market it still seems wise to limit that amount. If, however, more and more features are being added at the same time, that only leaves us with one option: There is no alternative to utilizing the available energy budget more efficiently.
More and more mouths to be fed in wearables
The wearables with the highest growth rates right now are TWS earbuds. And they are rapidly becoming smarter and smarter. For example, active noise cancellation, which a couple of years ago was only available in larger headphones (with large batteries), can now be found in almost every TWS device. Even though the implementations have been optimized, using ANC significantly reduces the batterie runtime. And the list of further new features is quite long: Additional microphones and algorithms for hearing enhancement, sensors for health monitoring, spatial audio processing, voice recognition and so on.
Needless to say, that all of them want to have a piece of the battery cake… At the same time, product designers call for even smaller devices to increase comfort and to enable all-day use. So again: Increasing the size of the cake is not an option! Consequently, the only option is to have components that are less hungry than the ones currently used.
Two thirds of the power budget are currently consumed by the audio chain!
It is obvious that the component with the highest consumption has the potential for the highest savings. Probably on top of that list for normal use cases is the wireless radio that ensures the connection to the audio signal source. To give a ballpark figure here, measurements on a typical – not brand-new – TWS device show a 10 mW power consumption just for being connected to a smartphone. Having 200 mWh available and considering a normal-use runtime of six hours that would account for approx. 1/3 of the power consumed by the entire system.
Luckily, with the development of new revisions of connection standards, the energy consumption of the wireless radio dropped significantly, yet allowing higher bandwidth and improved audio quality at the same time.
This, in return, makes other components more “visible” in terms of power consumption. And it is becoming increasingly worthwhile to assess which of them needs to be put on a diet. From the systems we examined, approximately two thirds of the power budget go into the audio chain, i.e., DSP, codec, amplifier, and audio transducer. For higher output levels it can be shown that a substantial part is consumed by the latter two components.
Therefore, an important key to solving the energy challenge seems to be finding new ways to generate sound.
In Part II, I am going to speak about electrostatic transducers and why they can be the solution.