Near-Field Communication (NFC) began as a data protocol, but can now simultaneously transmit power and data, allowing for the facilitation of wireless data transfer protocols, including UART, Inter-IC (I2C) and even Serial Peripheral Interface (SPI). Today, we’re focusing on NFC Power Harvesting, an established technology that’s being used in never-before-seen ways by NuCurrent and Infineon Technologies.
NFC Power Harvesting is appropriate for space-constrained devices, allowing product developers to harness the small amount of power required to send over the data authentication, and utilize it for other functions with the ultimate goal of eliminating batteries. Before diving into this blog, make sure to read NFC Wireless Charging Explained, and NFC Wireless UART Explained.
Breaking Power Harvesting
Breaking Down Power Harvesting
To start: What is power harvesting? In simple terms, power harvesting is the process of capturing energy from an electronic system’s environment and converting it into usable energy. Processes like solar, piezoelectric, radiowaves, and even sound have been used to try and power products such as ultra low power sensors and lights all without the need of a physical connection to a power source. The question is always: How much can I actually harvest? Historically, product designers have relied on batteries or a powered connection (i.e. cords) for energy storage, in lieu of direct harvesting, because the product’s power requirements were relatively high.
Above: a garden light is illuminated by solar power harvesting
Enter: NFC Power Harvesting
Wireless power is an invaluable technology for eliminating components that are prone to failure, and following connectors, batteries are the next most common point of device failure. Whether it’s the harshness of fast charging; extreme environmental conditions or just the ordinary loss of lithium inventory (LLI) … no battery can last forever.
And as the name implies, NFC Wireless Charging still requires batteries – which is appropriate for non-stationary devices (e.g. earbuds, wearables). However, some devices are stationary… so why keep the battery? Further, if the device is small enough to be appropriate for NFC Power Harvesting, then could it benefit from further miniturization due to eliminated battery space (and cost) savings?
Enter: NFC Wireless Charging
One of the benefits of NFC is that the components are quite small and the systems don’t require additional power from either communicating device to actually transmit the data. Rather, the same NFC coil transmits a very small amount of energy (<50mW) to “push” the data to the receiving device.
That, essentially, is what lead to the development of NFC WLC 1.0 and 2.0 and now presents the question and opportunity of NFC Power Harvesting: How can product developers take advantage of existing NFC Power Harvesting technology and maximize its functionality?
Today, NFC’s Power Harvesting capabilities cap at 50mW, largely due to the existing technology that’s on the market today*: Smartphone NFC coils. However, 50mW does provide some access to the market – again, for stationary, low-power devices (e.g. smart locks and sensors).
Above: Block diagram of a green near-field communication (NFC) – based sensor system
Image Source: A Survey of NFC Sensors Based on Energy Harvesting for IoT Applications
Given those constraints, NuCurrent, in partnership with Infineon Technologies, is working to increase the power capabilities of NFC Power Harvesting, by first maximizing the functionality of the receiving antenna. Based on Infineon silicon, NuCurrent is developing the world’s most advanced Energy Harvesting offering via NFC as a reliable, low-maintenance and secure replacement to batteries that significantly reduces e-waste. This low-cost, single-chip solution enables the development of cost-effective, miniaturized actuation or sensing applications operating in passive or active mode, again with the objective to augment batteries, prevent “dead battery” scenarios and, ultimately, eliminate batteries altogether.
Technology Application: Smart Locks
Technology Application: Smart Locks
Now that we’ve covered the basics, let’s run through a production application example: Smart Locks. As mentioned above, smart locks are stationary, low-power devices. Challenges existing for devices on the market to day is that:
- They run on batteries that frequently need to be replaced. This problem can be exacerbated by extreme hot or cold weather.
- The “backup” user experience is very poor, typically requiring users to connect a 9V battery to an external terminal on the smartlock to briefly turn on the device and grant access. If a 9V battery is not on hand – the user is locked out.
- The Consumer Product Safety Commission (CPSC) enacted regulations that lithium-ion batteries cannot be installed in doors or smartlocks.
- In this power harvesting example below, a battery-less smart lock is unlocked by tapping a smartphone to the device. After 1.5 seconds, the lock opens.
Above: Passive NFC padlock developed using Infineon NAC1080 controller
In this application, NFC Power Harvesting can prevent the user from being locked out or not getting the data they need by…
- Significantly extending the battery life by allowing NFC harvesting to add an additional “boost” reducing the amount of power drawn from the battery
- Preventing “dead battery” instances entirely
- Eliminating batteries from the device, allowing for a slimmer, more discrete form factor that requires fewer materials and is fully sealed, and finally
- Replacing the 9V battery “backup” method, allowing for a more realistic, convenient user experience to preventing locked-out scenarios
And that’s just an example of what’s possible with just 50mW today.
Path to Mass Production
Path to Mass Production
How do you know if that’s enough for your product design, there are several things to consider:
- Power is one metric, but you must consider the energy required to perform your desired function. How much power in what time? Opening a lock or extracting data from a sensor require time to execute a function, understanding this is critical to a successful design.
- What is your expected use case and what will your product interact with to harvest the power? Phones are everywhere and have certain capabilities of being able to deliver power. What will is the most intuitive for your user base?
- What is the size of your product? Size and material selection is critical to maximize user experience. A system the size of a quarter will have different characteristics when compared to a product the size of a business card.
NuCurrent’s engineers are developing methods to improve the functionality of this technology by increasing the amount of power that can be received in an NFC Power Harvesting system. For more information on how to become a first-mover with this technology, contact NuCurrent today.
*According to the NFC Forum, mobile device NFC is also increasing in transmitted power capability beyond 50mW, allowing NuCurrent to evaluate other applications that did not seem feasible previously.
