Wireless charging solution, covering 15w-50w

With more and more mobile phones and other terminals supporting wireless charging on the market, the demand for wireless charging continues to release, and gradually infiltrates into the automotive front loading market. Nanxin semiconductor, which has been deeply engaged in the field of charging, has recently launched three vehicle specification chips sc8701q / sc8101q / sc5003q, covering power from 15W to 50W, while continuously increasing R & D investment in wireless charging, contributing to the localization of on-board wireless charging scheme.

The principle block diagram of on-board wireless charging is shown in the figure, which is composed of a wide voltage input DCDC, a wireless charging transmitter (integrated power stage), a general MCU and a high-voltage LDO. The wireless charging transmitter sends the IDM / VDM / ISNs signal to the MCU. According to the power required by the equipment terminal, the MCU adjusts the voltage of DCDC through PWM or I2C on the one hand, and adjusts the working duty cycle of the internal power stage of the transmitter on the other hand, so as to adjust the output power of the transmitter. Here, LDO is used to supply power to MCU. It is an optional option and can also be realized by the buck integrated inside the wireless charging transmitter.

At present, the power level of on-board wireless charging is mainly divided into 15W and 40W / 50W, with a ratio of about 3:1. 15W power level according to different applications, the former DCDC can be divided into buck and buck boost topologies.

The typical voltage of lead-acid battery of passenger car is 12V, but it will fluctuate between 9V and 16V. Therefore, it can be divided into three situations:

(1) In the 15W wireless charging application of some models, when the battery voltage is lower than 12V, the system will reduce the power of the wireless charging module. Therefore, the previous DCDC can be realized with a buck converter.

(2) In the 15W wireless charging application of most models, 15W power output is required in the whole process of battery voltage fluctuation. At this time, the front stage DCDC needs to be realized by a buck boost chip.

(3) In 40W / 50W wireless charging applications, the voltage at the transmitter needs to reach 20V, so a buck boost chip is also needed to realize it.