Power management techniques in embedded systems

Power management in embedded systems can make the difference between an efficient and reliable system and one that simply doesn’t offer longevity. It’s often a crucial part of the development process in embedded system design, and it’s sensible to plan accordingly for how a system can use the lowest power while still operating correctly. But how do we achieve that? Two broad power management techniques exist—hardware and software—each leading to different routes on how best to reduce power consumption. To help understand the importance of appropriately controlling power within embedded systems, we’re here to look through what each method actually means and break down the benefits of doing so.

What’s the difference between power management and power efficiency?

Power management and power efficiency may sound like interchangeable terms, but there is a distinct difference. Power efficiency is about making best use of the power a system consumes in general usage such as by extending battery life. Better battery life is a valuable marketing tool for a general consumer device like a smartwatch, but it’s also essential for embedded systems that can’t easily be upgraded. For instance, a deep-sea embedded system may be complicated to access once installed, so an efficient power mode is vital to keep it running.

Power management is generally defined as the practical process of controlling power use in a system, such as by detecting if it’s in use and turning it off if it’s not. Both these ideas frequently dovetail when looking at reducing power consumption in embedded systems.

What are the two methods of power management?

Software power management techniques can be applied during the design and runtime stages. Using software-based measures can be as simple as initiating sleep modes on devices and adjusting power states accordingly. Any time you put your computer into standby or hibernate mode, you’re beginning a form of sleep mode, ergo a type of power management.

The process can also be more complicated , for example, when dynamically adjusting the frequency and voltage of the CPU—effectively like a slow-down mode on a computer or a low-power mode you see on a smartwatch or smartphone once it gets low on power. This process is known as dynamic voltage and frequency scaling, and when done effectively, it can extend the lifespan of a device and lead to such devices being slowed down purposefully to extend battery life and lower power consumption. It’s also possible to temporarily disable unused peripheral circuitry in a process known as clock or power gating, depending on the scenario.

Such software tweaks can be conducted at an operating system level for conventional devices. It may require time to configure by a software developer but will significantly help with power consumption. In other instances, code could be written more effectively to cut down on the number of logical CPU operations, leading to better efficiency and lower power consumption. This is why Linux kernels are popular within embedded computers, as they can be more easily customised to cut down on peripheral tasks running.

Hardware power management is typically designed around low power needs in the first place. There are two types:

• Static power management techniques are developed during the design stage, focusing on software and hardware optimisation.
• Dynamic power management techniques use runtime behavioural changes for controlling power and reducing consumption.

Most modern components are typically very low power, with some experts believing that, in theory, careful design could lead to 30 years of battery life on some systems. While that system may not be able to do anything other than reside in standby mode and may not be particularly useful, it could still function.

Generally, though, something like a processor in embedded systems is a significant power consumer despite improved efficiency. Fortunately, due to their processing power, they can also have an active role in managing power consumption on a software level. Typically, the processor is the first place for managing power. Besides software elements, the processor itself can have onboard features that target energy-saving measures, such as low power modes that are only activated once a specific boundary has been crossed.

What is power management in embedded systems?

Power management within embedded systems differs to those using a regular operating system. While a Windows operating system can be rebooted, recharged, or shut down, many embedded systems have very different roles. Battery power may be crucial here, but charging or replacing the battery may be less viable.

The key to power management here is to combine both software and hardware techniques. A poorly designed device could use too much current even with well optimised software, while poorly optimised software could drain the battery excessively even with the most efficient hardware. Balance is vital to ensure that the device is both operational and efficient.

What are the pros and cons of improved power efficiency?

Improved power efficiency has multiple advantages and disadvantages. The most notable one is that it leads to a more efficient product on the whole. Improved battery life is always a significant selling point for a consumer product. For specialist embedded systems, a system can involve less maintenance than one without appropriate embedded software. This can help with budgetary concerns as well as make deployment more efficient.

Besides battery life improvements, reduced temperatures can be achieved through optimal power efficiency. That means less chance of the system failing or becoming unreliable. For devices that are near people, noise reduction is another advantage, while the impact on the environment should be reduced too.

The downside? Balancing costs is a crucial part of the development process. While making something more efficient and cutting down on power usage leads to lots of benefits , it can be expensive to develop. Such measures need to be cost-effective, which varies depending on the company involved and its needs. It’s also very easy to make a mistake in development and cause the exact opposite effect— consuming far more power than before. Optimisation of embedded software is a critical part of preventing this from happening.

What’s the solution to power consumption in embedded systems?

Components and processors are more powerful than ever, yet they’re also typically more efficient than before too. The key is to master such components to ensure optimal power consumption. Whatever the device or plan, software and hardware power management solutions need to be implemented for maximum efficiency, and to achieve such results, one needs to consider power consumption holistically from the design stage.

While more efficient embedded software can be complex to develop and take more time, the trade-off is a more capable, reliable and functional system. It’s worth dedicating some time to figuring out how best to implement such features in one’s systems, whether that be as simple as adding hibernation modes, wake on LAN, developing better battery management, or optimising application code.