Eliminating the Smart Lock Battery Issues with NFC Technology

By: Qi Zhu, Director, Power and Sensor Solutions, Infineon Technologies

Today, battery-powered smart locks with shared access capabilities have become increasingly popular in both consumer and industrial access control applications. However, battery-related issues frequently arise in many use cases. For outdoor applications, fluctuating temperatures and extremes can significantly reduce battery life. Indoor applications, on the other hand, can incur high battery replacement costs -- particularly when dealing with a large number of locks. Additionally, safety concerns in industries such as oil, gas, mining, and aviation prohibit the use of lithium (Li) batteries.

Eliminating the need for batteries in smart lock applications can be achieved through energy harvesting technologies. However, choosing the right technology can be challenging when it comes to ensuring 24/7 serviceability. Photovoltaic technology, for instance, relies on sunlight availability. Piezoelectric and thermoelectric technologies, on the other hand, deliver power in the µW range, which means that the required harvesting time for 24/7 serviceability is too long.

To address this issue, a near-field communication (NFC) energy harvesting solution was chosen for two reasons. First, NFC technology is widely available on smartphones, making it a practical choice for users. Second, NFC energy harvesting can provide the necessary mW range of power needed to ensure 24/7 serviceability.

An integrated NFC lock solution can harvest between 20-50mW from the NFC field, depending on the type of smartphone in use. With a single-chip, highly integrated solution designers have the flexibility to create miniaturized, battery-less, mobile phone-controlled smart lock systems. Expectations are high for this design approach.

Smart Locks Today

Smart keyless entry locks, including deadbolt, lever handles, padlocks, and more, are expected to grow based on the increased use of the Internet of Things (IoT) and increasing acceptance of artificial intelligence (AI), and machine learning (ML) technologies. According to a recent report, the global smart lock market, currently valued at USD 1.95 billion in 2022, is expected to grow at a compound annual growth rate (CAGR) of 19.6% from 2023 to 2030. A potential deterrent to this growth occurs when users, especially industrial and consumer-focused organizations with a large number of locks, are faced with the reality of having to replace the batteries in all the smart locks. In addition to the cost and time it takes to replace the batteries, the replaced batteries are destined to go landfills creating a non-sustainable situation.

NFC Lock Solution

Near-field communication (so-called NFC) is a mature technology for contactless exchange of data over short distances. Besides the data exchange, NFC technology itself can also transfer power with the electromagnetic field. The combination of data exchange and energy transfer in one interface and NFC availability in billions of smartphones make NFC an exciting enabler for passive lock application.

When a mobile phone with active NFC is put close to the NFC antenna of the smart lock, the mobile phone will detect the NFC device and start to build NFC communication (see Figure 1). Spontaneously, the 13.56MHz NFC carrier signal transfers a certain amount of energy to the receive antenna. The received AC signal is converted to DC current after passing through the rectifier and then used to charge the capacitor. As long as the NFC connection is available, energy is transferred from the mobile phone to the capacitor. The energy stored in the capacitor is controlled by an H-Bridge to drive the motor rotation.

The ubiquitous mobile phone, supported by both iOS and Android devices, provides the access to the lock. Smart lock functions of access sharing, key management and others are enabled with mobile apps. Implementation on the lock side can be as simple as an NFC actuation controller, a PCB antenna, a capacitor, and a DC motor. It is simple, small, and cost effective. This design approach provides high level digital security – native security with short distance NFC communication and an encrypted NFC data frame.

The use of battery-free NFC technology could provide even greater momentum for future smart lock growth. Integration in an actuation controller simplifies the use of this design approach and its implementation in several use cases.

Figure 1. The NFC lock system concept with an integrated NFC actuation controller.

Typical Use Cases

An integrated NFC controller is especially suitable for locks that require little mechanical effort. Typical use cases include:

In many sectors, conventional keys are fast becoming obsolete. This development has already reached the self-storage industry. For instance, Keep It Simple Storage (KISS), a US-based provider of state-of-the-art solutions designed to make running self-storage facilities operationally effective, has transitioned from manual locks to battery-free NFC smart locks powered by an NFC actuation controller (see Figure 2). While providing greater convenience and flexibility to the operator and the user, this solution enables instant troubleshooting and remote problem-solving, a feature not previously available in this industry through battery operated smart locks. These features eliminate common self-storage inconveniences such as overlocking for auctions, cutting locks for lost keys, and replacing locks due to wear and tear. It also eliminates the need for operators to provide 24/7 maintenance teams for individual lock incidents.

Figure 2. Battery-less NFC locks for self-storage facility made by KISS Solutions.

One of the more intriguing applications for an NFC actuation controller is the emergency power supply for smart door lock applications. In these instances, the interface provides an emergency solution when the batteries in standard smart locks are out of power. NFC energy is continuously harvested from the cell phone to the lock system to enable the opening action. This use of the interface avoids the need to call an expensive locksmith service to open the lock.

Transitioning to Battery-less Operation: Tools, Software and Design Support

Customers desiring to integrate a battery-less lock into their product or service may lack the necessary resources to develop a complete lock. To address this issue, a partner network is available with various levels of support - from antenna and circuit design to complete lock design and even lock original design manufacturing (ODM) services. Partner examples include:

For the most recent partners visit https://www.infineon.com/cms/en/product/power/contactless-power-sensing-ics/nfc-tag-side-controllers/#!partners.

Unlocking the Future

Implementing NFC technology in smart locks not only eliminates the inconvenience of battery replacements, but it also promotes sustainability and reduces waste. As we continue to embrace smart technology in our homes and businesses, NFC-enabled smart locks have the potential to make our lives easier and more eco-friendly.

References

Grand View Research, Smart Lock Market Size, Share & Trends Analysis Report,

https://www.grandviewresearch.com/industry-analysis/smart-lock-market

https://www.infineon.com/cms/en/product/power/contactless-power-sensing-ics/nfc-tag-side-controllers/nac1080/

https://www.infineon.com/cms/en/product/power/contactless-power-sensing-ics/nfc-tag-side-controllers/#!partners