Building Better Power Sources for Modern Embedded Systems

Miniaturisation of electronics has created numerous modern form factors where a conventional battery does not fit any more. Thus you may need to go for a different battery to power your new mobile design. This article helps you in selecting the one for your next-generation embedded system -- Sneha Ambastha and Dilin Anand

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Chemical composition. The designer will have to select battery technology based on its chemistry and also ensure that it does not have any substance of very high concern (SVHC). Most countries are very specific about Restriction of Hazardous Substances (RoHS) Directive and the EMI/EMC norms of the equipment. In such cases, even the certification stamp on the power supply/type of components used matters for the final design to be approved.

If we need a compact and portable battery, a Li-ion battery is chosen. These batteries are so common because they are some of the most energetic rechargeable batteries available and have a high energy-to-weight ratio. Comparing the different technologies is beyond the scope of the article, but we have featured two very new technologies targeting wearable electronics in the next section.

Battery technology for the Internet of Things
Internet of Things and wearable electronics both have one thing in common—unorthodox device form factors. In devices like watches, where cell batteries were traditionally used, the current generation of smart watches require something that can pack much more punch. With this in mind, vendors have started coming out with batteries that allow designers to custom-build their own batteries for specific sizes.

Solicore is an embedded power solutions vendor, who has a range of very thin 3D printed batteries with lifetime recharging capability, customisable shape option and high energy density with no toxic materials inside.

This solves the problem of the shape, size and overall form factor for a portable electronic device. The lack of toxic materials makes it an easy choice for use in wearable electronics without attracting the ire of the final user.

Imprint Energy is another firm that enabled the creation of rechargeable zinc-based ultra-thin batteries without the safety concerns of other battery technologies. Considering the importance that manufacturers of wearable electronics place on user experience, this could be a must-have technology for the next generation of miniature electronics.

If you are using an ultra-low-power chip in your design, you stand to gain from the availability of computing chipsets that can function at a thermal design power of just 3W. With such an efficient computing platform, one popular application is to use solar-powered wireless devices for bolstering surveillance through hidden sensors in the field.

Ensuring reliable power source designs
A battery requires protection from different electrical conditions such as discharge, overcharge and short circuit. In the absence of adequately protected batteries, your design might turn into a ticking bomb.

The Li-ion battery pack that is used in almost all portable electronic devices, starting from a small mobile phone to a laptop, has two to three main levels of protection.

1A2_Major

The first is the IC level of protection that is done by the battery management unit (BMU). This BMU is responsible for managing charging and discharging of the battery, and it is also the primary protection level. So if something happens and the battery goes too high on voltage or current, it would turn the pack off.

Then there is a secondary level of protection that is made compulsory by the Underwriters Laboratories (UL) test standards so as to ensure that the faults left in the primary level can be removed at the secondary level of protection. Many companies work to provide battery protection, especially for the Li-ion batteries, either at the primary level or at the secondary level.

At these different levels, the types of protections available for the Li-ion batteries are as follows:
1. PTC. A secondary level of protection that is used for automatic reset. It is considered to be a special type of fuse that protects against overcurrent and overheating.
2. CID/pressure valve. Again a secondary level of protection that disables the cells permanently in case of high pressure that may be created due to overcharging.
3. PCB protection. A primary level protection that protects against overcharging, overdischarging and even overcurrent.

Like the other types of batteries and cells, solar cells need to be protected too. Solar cells need fuses called solar fuses, which need to be certified either by UL or International Electro Commission (IEC). IEC certification is now more prominent in India. In IEC, if a fuse is tested for 135 per cent on overload, it should continue working till 60 minutes. On the other hand, in UL it should go on at 145 per cent for 60 minutes. Although certification ensures that the solar fuses are safe to be used with the solar cells, there is a requirement of a perfect material for the fuse that would make it more robust to support the cell in extreme conditions.

Industries are now coming up with a melamine-based fuse that can resist even high hot temperatures and low cold temperatures, thus allowing the solar cells to work with the same efficiency all around.

New tools to spruce up designing
A number of tools have been introduced recently that can help simplify the design process in numerous ways.

Interactive battery power design tool. This is a powerful tool that helps device developers and designers pre-determine the battery power requirements for the product being designed.

This tool helps determine the parameters such as size of the battery required, battery life and energy harvesting, all with respect to the application where the device would be used.

It helps product designers and developers predetermine the battery power requirements for new products. Users are allowed to select a pre-configured product scenario or build their own use case using the defaults provided.

Wattson by Logic PD. Wattson is an application to measure power, to monitor performance and to deliver real-time feedback of the battery-powered device. It helps in minimising power and maximising the battery life for the end product by enabling the engineers to analyse data through a graphical feedback system, without having to use external oscilloscopes or digital multimeters.

Spy on batteries. This is a device that can help to keep a check on the actions of the lithium ions inside a nano battery. This data can, in turn, be used to develop improvised batteries that would last longer, and can also be used to power all applications—starting from an electric vehicle to a small cell phone. As lithium batteries have been so popular, this device can bring a revolutionary enhancement in the market. Designers would not have to restrict their product design because of the battery to be used.


Sneha Ambastha is a technical journalist and Dilin Anand is a senior assistant editor at EFY

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