How to choose a wireless power supply chipset for wearable devices with large battery capacity and small size?

In recent years, the consumer electronics market has expanded rapidly, wearable devices have continued to increase in volume, and the requirements for their safety performance have become higher and higher. Under this trend, wireless power supply has gradually emerged. Its sealed and non-porous design has greatly improved the waterproof and dustproof performance of the device, which can reduce the risk of electric shock, and it is easier and more convenient to charge when placed.

“When it comes to wireless power supply, many people first think of Qi power supply such as smartphones and tablet computers,” said Wu Juan, director of the technology center of ROHM semiconductor (Shanghai) Co., Ltd.. Although the power supply capacity of Qi standard products can reach 15W, its The size is large, “For small wearable devices, Qi specifications are not applicable.” Therefore, for small wearable devices, Rohm’s Lapistone Technology launched the first generation of wireless power supply chipset “ML763x”.

The first-generation products are mainly used in TWS headsets, wireless keyboards and mice, and can reach 200mW power supply. For products with a slightly larger battery capacity, at least 500mW or more power supply is required. At this time, the previous solutions are not suitable. Wu Juan introduced that in order to meet market demand, ROHM has launched the second-generation wireless power supply chipset “ML766x” with up to 1W power supply, mainly for wrist blood pressure monitors, hearing aids, smart watches, electric toothbrushes and other products.

The wireless power supply chipset released this time includes the transmitter LSI “ML7661” and the receiver LSI “ML7660”. The transmitter LSI adopts a 40pin WQFN package, and the receiver LSI adopts a 30pin WL-CSP package or a 32pin WQFN package. Wu Juan said that customers can choose a suitable package according to the charging target size or the specific requirements of the charging system size.

According to reports, the new generation of wireless power supply chipset “ML766x” adopts the magnetic resonance power supply method to improve efficiency through the resonance frequency of the transmitting end and the receiving end. With the industry’s ultra-small system size, the wearable device has both wireless power supply and non-contact communication. Function.

Generally speaking, the power supply system includes antennas, ICs and peripheral components. The size of the Qi standard product system reaches 650mm2. As mentioned earlier, even if the maximum power supply of Qi standard products is as high as 15W, for small Electronic devices, the size exceeds the specifications and the area is too large. The ML766x chipset increases the communication frequency to 13.56MHz, greatly reducing the antenna size; on the other hand, the chipset has a built-in SPI/I2C communication protocol, and the power supply system can realize communication control without MCU. Compared with common products on the market (power supply 0.5W, frequency 100kHz), the system size and area of ​​the ML766x chipset has been reduced by 30%. In addition, according to the amount of power required, the chipset optimizes the control of the transmit power, thereby suppressing the heat generation of the LSI main body, and achieves a wireless power supply capacity of up to 1W. Compared with ordinary products, the power supply is also twice as high.

In addition, the receiving end of ML766x is also equipped with 496Byte flash memory and 10-bit A/D. It also has built-in NFC Forum Type 3 Tag function. It uses 13.56MHz near field communication technology and is multiplexed with wireless power supply. Only one antenna can be used at the same time. Perform two functions: wireless power supply and wireless communication. NFC typical mode is also added to four communication modes, including card reader mode, card emulation mode, point-to-point mode and wireless power supply mode.

For market applications, the chipset released this time has great advantages in rotating structure equipment. For example, the LED lights on the cooling fan of the game console need to be wirelessly powered to avoid power failure due to twisted wires. At the same time, position sensor information can be obtained through contactless communication to control the fan speed and improve design flexibility. Another example is to detect the torque of an electric bicycle through the chipset and control the speed.

According to Wu Juan, the new product meets the frequency and power standards required by China’s “Radio Management Regulations”, and customers can still use it with confidence in the future. According to reports, the second-generation wireless power supply chipset “ML766x” will be officially mass-produced in April 2022, and the initial mass production scale is expected to be 100,000 pieces per month. In ROHM’s future planning, the next-generation wireless power supply chipset is under development, and the maximum power supply is expected to be set to 250mW. The research and development is further towards miniaturization and thinning, and is committed to expanding the application of wireless power supply to various application products. middle.

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