Cover story
Best applications for IoT in the world of IC power management
By Diarmuid Carey, Central Applications Engineer, Analog Devices W
ith the growing use of IoT devices in industrial equipment, home
automation and medical applications, there is increasing pressure to optimise the power management portion of these devices – either through smaller size, better efficiency, improved current consumption or faster charging times (for portable IoT devices), all of which must be achieved withouth adding to thermals and without interference with the wireless communication in the devices. Generally, IoT devices are smart, most likely battery powered, sending data to the cloud. The data comes from a mixture of embedded systems (processors, communication ICs, sensors, etc.) that collect and send it to a central point or other node in the network. This can be anything from a simple temperature sensor reporting room temperature back to a central monitoring area, all the way up to a machine-health monitor that tracks the long-term status of factory equipment. Ultimately, these devices address
a particular challenge, whether to automate tasks that would typically require human intervention, or improve the useability and longevity of equipment.
Applications The application areas for IoT devices are almost endless, with new devices and uses coming up daily. At present, the IoT focus is on five main areas: • Smart health – supporting vital-signs- monitoring applications at clinical level but also in consumer applications.
• Smart factories – focusing on building
Industry 4.0 by making factories more responsive, flexible and leaner.
• Smart buildings/cities – using intelligent sensing for building security, parking space occupancy detection, as well as thermal and electrical control.
• Smart agriculture – using the technology available to enable automated farming and improve resource-usage efficiencies.
• Smart infrastructure – building on condition-based monitoring technology to monitor movement and structural health.
IoT design challenges The majority of these devices, or nodes, are being retrofitted or are located in hard-to-reach areas, where power is not readily accessible. This makes them require batteries and/or energy harvesting as a power source. Moving power around large facilities can be quite expensive. For example, consider powering a remote IoT node in a factory. The idea of running a new power cable to power this device is costly and time consuming, leaving battery power or energy harvesting as the remaining options to power these remote nodes. The reliance on battery power
introduces a need to follow a stringent power budget to ensure that the lifetime of the battery is maximised, which in turn has an impact on the device’s total cost of ownership. Another downside to battery usage is the need to replace the battery after its life has expired. This includes not only the cost of the battery itself, but that of the human labour to maintain it. Also, it is very easy to just overdesign the battery to ensure that there is sufficient capacity to achieve the lifetime requirement, which should be greater than 10 years. However,
06 July/August 2022
www.electronicsworld.co.uk
overdesign results in additional cost and size, so it is extremely important to not only optimise the power budget but also to minimise the energy usage where possible in order to install the smallest possible battery that will still meet the design requirements.
Power in IoT For the purposes of this power discussion, the power sources for IoT applications can be seen as three scenarios: • Devices that rely on non-rechargeable battery power (primary battery);
• Devices that require rechargeable batteries;
• Devices that utilise energy harvesting to provide system power. These sources can be used individually, or combined.
Primary battery applications Non-rechargeable battery applications are found in applications where only occasional power is used. The main advantage of this approch is that it provides high energy density and simpler design, since there’s no need for battery charging/management circuitry. This method is also cheaper. However, because these batteries have a finite lifetime, they are not so suited to applications where power consumption is higher. Consider a large IoT installation with
many nodes. As you have a technician on-site replacing the battery for one device, very often all the batteries will end up being replaced at one time to save the labour cost. Of course, this is wasteful and adds to the overall global waste problem. On top of that, non-rechargeable batteries provide only about 2% of the power used to manufacture them in the first place.
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