How does the wireless charging module of the smart bracelet achieve a balance between high efficiency and low heat generation?
Release Time : 2026-02-11
The wireless charging module of a smart bracelet needs to achieve high-efficiency power transmission within a limited space, while controlling the impact of heat generation on device performance and user experience. This technical achievement requires a collaborative effort involving electromagnetic design optimization, material innovation, heat dissipation strategies, and intelligent control.
Electromagnetic design optimization is key to improving efficiency. Traditional wireless charging relies on the principle of electromagnetic induction, transmitting energy through magnetic field coupling between the transmitting and receiving coils. However, wearable devices like smart bracelets have small coil sizes due to size constraints, resulting in insufficient magnetic field coupling strength and increased energy loss. To address this, engineers use high-permeability materials (such as ferrite or nanocrystals) to fabricate the coil core, enhancing the magnetic field concentration effect and improving coupling efficiency. Simultaneously, optimizing the coil winding process (such as Litz wire braiding) reduces the skin effect and decreases resistance loss under high-frequency AC, further improving transmission efficiency.
Material innovation is crucial for reducing heat generation. The heat generated by the wireless charging module mainly comes from coil resistance loss and core eddy current loss. For the coil section, using low-resistivity copper alloys or silver-plated copper wire can reduce Joule heating. For the magnetic core, nanocrystalline materials, due to their high resistivity, can significantly suppress eddy current effects and reduce core heating. Furthermore, the rectifier diodes and voltage regulator chips in the receiving circuit must also be selected with low on-resistance and low quiescent current to reduce heat loss during power conversion.
The heat dissipation strategy must balance efficiency and size constraints. The compact internal space of a smart bracelet cannot accommodate traditional cooling fans or large heat sinks; therefore, a combination of passive cooling and structural optimization is necessary. For example, heat-generating components (such as the coil and charging chip) can be positioned near the bracelet band, using the band's metal components or high thermal conductivity plastics as heat dissipation channels to conduct heat to the outside of the bracelet; or thermally conductive gel can be filled between the coil and the circuit board to improve thermal interface contact efficiency and accelerate heat dissipation. Some high-end products also use a graphene coating on the bracelet shell, utilizing its high thermal conductivity to assist in heat dissipation.
Intelligent temperature control technology can dynamically balance efficiency and heat generation. By integrating a temperature sensor and microcontroller, the charging module temperature is monitored in real time, and the charging power is automatically adjusted based on threshold values. For example, when the temperature approaches the safe upper limit, the system reduces the transmitter's output power or switches to intermittent charging mode to reduce heat accumulation; once the temperature drops, high-power charging is resumed. This dynamic adjustment mechanism avoids overheating risks and minimizes charging time.
Resonant coupling technology extends transmission distance and improves efficiency. Traditional electromagnetic induction wireless charging requires strict alignment of the transmitter and receiver coils; otherwise, efficiency drops significantly. Magnetic resonance coupling technology, by tuning the coils to the same resonant frequency, allows for efficient energy transmission within a certain offset range, reducing efficiency loss and heat generation due to misalignment. Although this technology requires more complex circuit design, its application in small devices such as smartwatches is maturing.
Low-power architecture design reduces heat generation at the source. The efficiency of a wireless charging module depends not only on the transmission process but also on the overall circuit design. By using low-power chips and optimizing power management algorithms (such as dynamically adjusting operating voltage and frequency), the module's standby and operating power consumption can be reduced, thereby reducing heat generation. For example, some products automatically reduce charging power when the smart bracelet's battery is low, protecting the battery and preventing high temperatures from accelerating battery aging.
With the application of new materials (such as gallium nitride power devices) and new processes (such as chip-level integration), smart bracelet wireless charging modules will further overcome the trade-off between efficiency and heat generation. For instance, the high-frequency characteristics and low switching losses of gallium nitride devices can increase charging power density while reducing heat generation; and integrating the coil, magnetic core, and charging chip into a single module can reduce parasitic resistance and electromagnetic interference, optimizing overall performance. These technological advancements will drive the upgrade of wireless charging from simply "usable" to an "efficient, safe, and seamless" experience.