Wireless charging on mobile devices: Innovations and applications

Wireless charging technology has streamlined the way we use mobile devices. Eliminating the need for cables not only increases user convenience but also reduces wear on charging ports and enables the creation of more durable devices. This article explores how wireless energy transfer technology works, its latest applications, and the development directions it is likely to follow in the future.

How does wireless inductive charging work?

Wireless charging is a modern energy transfer method that eliminates the need for cables to power devices. This technology is based on the principle of electromagnetic induction, which uses an alternating magnetic field to transfer energy between two coils—a transmitter and a receiver. This solution not only enhances user convenience but also reduces physical wear on charging ports in devices.

The principle of operation of inductive chargers

The functioning of wireless charging technology is based on Faraday’s law of electromagnetic induction, which states that an alternating magnetic field generates current in a conductor. In the case of wireless charging, the conductor consists of induction coils that operate in tandem:

• Transmitting coil – located in the charger, generates an alternating electromagnetic field through the flow of alternating current.
• Receiving coil – embedded in the device, captures the electromagnetic field and converts it into electrical energy to charge the battery.

Step-by-step wireless charging process:

1. Generation of the electromagnetic field. The charger, equipped with a transmitting coil, is connected to a power source. When the charging process starts, an alternating current flows through the coil, generating an alternating electromagnetic field around it.
2. Energy transfer. The electromagnetic field propagates over a short distance, reaching the receiving coil embedded in the device. To ensure efficiency, the coils must be precisely aligned in terms of position and electromagnetic properties.
3. Induction of electric energy. The receiving coil, located in the mobile device, captures the alternating electromagnetic field and induces an electric current in its circuit, following the principles of electromagnetic induction.
4. Energy conversion and storage. The generated electric current is directed to the device’s energy management system, where it is rectified (converted from AC to DC) and stored in the battery, which powers the device.

Is wireless charging energy efficient?

In electromagnetic induction technology, the distance between the transmitting and receiving coils is of critical importance. Maximum efficiency is achieved when the two coils are positioned very close to each other, typically at a distance of 1 to 5 mm. At greater distances, the transmitted energy becomes less efficient, and heat losses may increase. For this reason, modern wireless charging systems are designed to minimize the distance between the charger and the device.

Advantages and disadvantages

Why choose a wireless charger?

• No physical wear on charging ports, as the device does not require a physical connection to a cable, making the ports less prone to damage.
• Convenience of use – devices can be charged simply by placing them on a compatible surface, eliminating the need to plug and unplug cables.
• Aesthetic appeal – the absence of cables contributes to a more minimalist and organized workspace, such as desks or public areas.

What are the main limitations of inductive charging?

• Proximity requirement, the system works effectively only at short distances. While technology for longer charging distances is under development, most devices currently require physical contact or a very close range between the charger and the device.
• Energy losses, compared to traditional wired charging, wireless energy transfer results in greater losses. In electromagnetic induction systems, energy losses can range from 10% to 25%, depending on the precision and alignment of the coils. By comparison, traditional wired charging incurs only 2% to 5% energy loss during transmission. These losses are mainly caused by thermal resistive losses and inefficiencies in energy conversion.

What is the Qi standard?

Qi is a standard developed by the Wireless Power Consortium, which defines universal principles for wireless charging technology. Its primary goal is to ensure compatibility between various devices and chargers. Qi is based on electromagnetic induction technology and supports charging devices with power levels ranging from 5 watts to 15 watts. The Qi standard is widely implemented in smartphones, smartwatches, and accessories such as wireless headphones.

What is the Qi2 standard?

Qi2 is the next generation of the wireless charging standard introduced by WPC in 2023. It brings technological advancements and improved compatibility with modern devices. The key features of Qi2 include:

• greater precision in positioning, thanks to improved magnetic alignment of the charger and the device, making the charging process more efficient
• Support for higher power. Qi2 enables charging power exceeding 15 watts
• Backward compatibility. Qi2 is compatible with Qi1-supported devices, allowing an easy transition to the new standard.

Comparison of Qi1 and Qi2 standards

Applications of wireless charging

Wireless charging, originally designed for smartphones, has gained popularity in many other fields. Below are some examples:

• Mobile devices such as smartphones and wireless earbuds are the most commonly charged devices using inductive technology. Modern chargers support increasingly higher power outputs, such as 15W or 30W, significantly reducing charging times.
• Wearable electronics, including smartwatches, fitness bands, and other portable devices, benefit greatly from wireless charging technology. Thanks to coil miniaturization, inductive charging systems are becoming more effective for compact applications.
• Electric vehicles make use of wireless charging for cars, marking another technological breakthrough. Systems like Wireless EV Charging (WEVC) enable cable-free charging, improving user convenience significantly.
• Medical equipment now incorporates this technology to wirelessly charge implants and portable devices like insulin pumps and health monitoring sensors, reducing risks associated with tangled or damaged cables.
• Furniture with built-in wireless chargers is becoming increasingly popular. Manufacturers are integrating wireless chargers into tables, desks, and nightstands, enhancing convenience in homes and offices.

Directions of development of wireless charging technology

• Greater energy efficiency. Current wireless charging systems are less energy-efficient than wired solutions— a significant amount of energy is lost as heat. Efforts to reduce energy losses are focused on improving the environmental and economic efficiency of wireless charging technology.
• Multi-device charging. Modern chargers can power multiple devices simultaneously. The future lies in systems that automatically detect the number of connected devices and efficiently distribute power, enhancing user convenience and optimizing the charging process.
• Integration with smart systems and IoT smart chargers. Can this wireless charging innovation positively impact device longevity? In our opinion, yes. Wireless charging technology is advancing toward improved integration with IoT systems. Prototype chargers are designed to communicate with devices, manage energy, and adapt charging settings to user needs. For example, smart home systems are testing features that automatically stop charging once the battery is fully charged, reducing energy consumption and prolonging device lifespan. However, widespread implementation of these solutions remains a significant challenge.
• Remote charging. Companies such as Xiaomi and Energous are developing wireless charging technology based on the use of radio waves or lasers. These systems enable devices to be powered at distances of several meters from the charger, eliminating the need for physical contact with the charging device.
  • Radio wave technology transmits energy via radio waves. Systems developed by companies such as Energous send energy over distances of several meters by converting electrical energy into low-frequency radio waves. Receivers within devices then convert the waves back into electricity. Currently, this technology is in the development phase and is primarily applied in small IoT devices.
  • Laser technology transmits energy via a laser beam, which is received by a dedicated receiver. This receiver converts light energy into electricity, enabling devices to be powered. This solution facilitates energy transfer over significant distances but requires a clear line of sight between the transmitter and receiver. It is advised to avoid exposure to laser beams for safety reasons. Currently, laser technology is mainly used in research and specific industrial environments.
  • Magnetic resonance technology relies on energy transfer between two coils resonating at the same frequency. Although grounded in electromagnetic principles, it differs from conventional electromagnetic induction. In electromagnetic induction, energy is directly transferred through magnetic coupling between transmitting and receiving coils. In magnetic resonance, energy is transmitted via the phenomenon of resonance between coils tuned to the same frequency, enabling energy transfer over longer distances, up to several tens of centimeters, while minimizing power losses. Resonant technology offers greater flexibility in positioning devices relative to the charger, rendering it particularly advantageous for multi-device chargers and mobile powered devices, such as autonomous robots. Although not yet widely adopted, this technology is already finding application in certain commercial solutions.

The future of wireless charging

Wireless charging technology for portable devices transforms our interaction with electronics, offering more convenient and durable solutions. The development of this technology, supported by new applications such as remote charging and integration with smart IoT systems, reveals its immense potential to enhance our everyday lives. Although many solutions are still in the development phase, wireless charging is already widely adopted in mobile devices, medical equipment, and the automotive industry. At Device Prototype, we provide comprehensive support in designing, prototyping, and implementing future technologies. Feel free to contact us for assistance in implementing cutting-edge solutions.