Why is the battery life of mobile phones always insufficient? How much do you know about the strategies for optimizing power consumption?

In the design of mobile consumer products, power consumption and battery life are always a big challenge. Take mobile phones as an example. Battery capacity is getting bigger and bigger, and chip power consumption is getting lower and lower, but the battery life of mobile phones has not brought consumers a significantly improved experience. This is mainly because the addition of new functions to mobile phones has increased the power consumption of the whole device, so that the extended battery life of large-capacity batteries and low-power ICs is eaten up by new functions.

Where does the power consumption go?

For example, the high refresh rate screen is popular nowadays. The refresh rate of early mobile phone screens was only 60Hz, but now 90Hz and 120Hz are gradually becoming popular. Users who are not sensitive to screen refresh rate are now gradually experiencing the better visual experience brought by high refresh rate. High refresh rate often means high data rate, which requires more power consumption.

At the same time, the brightness of the screen is getting higher and higher. The display of early mobile phones was basically invisible in the sun. Thanks to the advancement of technology, the brightness of current mobile phones can easily reach 400nit, or even approach 1000nit. The screen is a big power consumer. In high-brightness mode, high power consumption causes serious heat, and heat further affects power consumption. Therefore, our mobile phones will feel hotter when we are outdoors during the day in summer.

Apart from the CPU and GPU, the speaker is also a big power consumer. In order to provide a better audio-visual experience, stereo speakers have been favored by many consumers in the mobile phone field in recent years. In addition to the increased power consumption of the speaker itself, the speaker's smart amplifier and the sound effect algorithm behind it will also increase power consumption .

In addition, there are various sensors such as cameras, fingerprints, infrared, etc., all of which, without exception, snatch power consumption resources from the battery.

The optimization of mobile phone power consumption has always been a topic worthy of in-depth research. It is also a very difficult topic. It requires understanding of software architecture strategies, hardware principle solutions, manufacturing process technology, etc. It is a research direction that involves a wide range, complex knowledge, and relatively high requirements for practitioners.

How to make software?

The power consumption optimization solutions are listed from top to bottom. The first one is software strategy optimization. The simplest direction is to reduce the main frequency. In our daily use of mobile phones, there is no need for the mobile phone CPU to run at full load, and there is no need to use DDR at full power. Reasonable scheduling of various work tasks according to the user's usage environment and reasonable allocation of resources are the most direct strategies to optimize power consumption.

For the screen, although it supports high refresh rate, for static display scenarios such as reading, chatting, browsing the web, etc., the screen switches slowly. At this time, the frame rate can be lowered. Reasonable configuration of the frame rate can greatly reduce power consumption without affecting the user experience. So how to define high and low frame rate scenarios and then reasonably call different display frame rates. This requires each mobile phone manufacturer to investigate user usage habits and form their own set of control optimization strategies.

I believe most people know that when we are not using the camera, the camera is turned off, and it will not take pictures or record videos (the behavior of QQ browser secretly starting the camera is not discussed here). This is a direct solution to reduce power consumption. Modules that are not in use by users must be powered off or enter bypass mode to reduce power consumption. Furthermore, there are hundreds of IO pins in the mobile phone CPU. These pins need to be reasonably configured according to their respective working states, and they must be set low when they should be. Otherwise, there may be abnormal power consumption of hundreds of uA or even mA level, which will undoubtedly increase the power consumption of the mobile phone for no reason and reduce the battery life experience.

How to make the hardware?

As for hardware, it seems that there is nothing that can be done on the surface. In fact, in addition to choosing efficient and low-power hardware implementation solutions, mobile phone manufacturers can also design a reasonable hardware architecture to reduce the useless power consumption of mobile phones without affecting performance.

For example, the power supply should be reasonably distributed. Whether it is a BUCK, BOOST switching power supply or an LDO linear power supply, their efficiency is not constant. We need to design a reasonable power supply architecture to make them work under efficient conditions to reduce power consumption. Generally speaking, the efficiency of a switching power supply is better than that of an LDO. Therefore, a switching power supply can be used preferentially in places that are not sensitive to power supply noise. For an LDO low-voltage dropout linear power supply, it needs to be used at the lowest possible voltage drop to reduce power consumption.

In early 2020, a mobile phone manufacturer launched a mobile phone with a 4 POWER screen. Its promotional point is to improve the battery life experience. There is a power line in the screen, which is converted from 1.8V to 1.2V. If it is powered by a linear power supply, the efficiency is about 67%. If it is replaced with a switching power supply, the efficiency will be improved and the power consumption will be reduced. The improved efficiency does not seem to be very large, but considering that the screen is a constantly on working module, the energy consumed is proportional to the usage time. The longer the time, the more obvious the power consumption saved by this solution. This is actually not some black technology.

In addition, some people may have such questions: if my mobile phone screen displays a static image, such as the desktop or a static picture, is it still interacting with data?

This is limited by the hardware solution. A small cache can be added to the screen to store the display image. If the image is not updated, the screen will directly display the content in the cache, reducing the data flow with the CPU and thus reducing power consumption. For example, the mobile phone screen display uses this small storage space. When the screen is off, the CPU does not always interact with the screen for data. The screen only reads the display image from the internal cache. However, if the mobile phone has extreme requirements for cost, this storage may be deleted. In this case, the CPU must maintain communication with the screen, and power consumption will increase accordingly.

The above is some discussion about mobile phone power consumption optimization. Power consumption optimization is a complex and arduous project, so let’s stop here for today.