“With the popularity of mobile phones supporting wireless charging, wireless chargers have also begun to enter the car. In response to industry pain points such as cumbersome design of wireless charging products and difficulty in certification, ZLG has launched a complete set of vehicle-mounted 15W wireless charging solutions. MWCT1013A based on NXP is designed as the main control, adopts MP-A9 topology, three coils, and has CAN communication and NFC functions. Provide complete software and hardware support to help customers pass Qi standard certification.
Abstract: With the popularity of mobile phones supporting wireless charging, wireless chargers have also begun to enter the car. In response to industry pain points such as cumbersome design of wireless charging products and difficulty in certification, ZLG has launched a complete set of vehicle-mounted 15W wireless charging solutions. MWCT1013A based on NXP is designed as the main control, adopts MP-A9 topology, three coils, and has CAN communication and NFC functions. Provide complete software and hardware support to help customers pass Qi standard certification.
1. Wireless charging standard
The Wireless Power Consortium (Wireless Power Consortium) was established on December 17, 2008. At present, more than 600 companies have joined the consortium. The Qi standard formulated by it is currently a widely commercial wireless charging standard on the market.
The Qi standard specifies the power transmission and communication protocol between the wireless charging transmitter and the power receiving end, which can adjust the output power of the wireless charger and improve the transmission efficiency of the system.
Figure 1 Qi standard logo
According to the wireless charging power level, power control method, operating frequency, communication control, voltage range, coil parameters and quantity, a number of topology scheme standards have been derived. The MP-A9 topology is commonly used in automotive-grade wireless charging solutions, with three coils, requiring rail voltage range of 1~25V, resolution higher than 25mV, initial default frequency 127.772 kHz, coil current acquisition accuracy higher than 7mA, power adjustment adopts PID Regulate, the inverter circuit is a full-bridge fixed-frequency control circuit.
2. Vehicle wireless charging scheme
The ZLG vehicle-mounted wireless charging solution uses NXP’s MWCT1013A as the main control. The vehicle-mounted 12V battery is used as the power source. The 5V voltage is generated through the EMI filter and DC-DC to supply power for the LDO, MOSFET driver and CAN transceiver. The 3.3V output by the LDO mainly supplies power for the WCT1013A and NFC chip.
The digital full-bridge BUCK-BOOST circuit adjusts the output 1~25V rail voltage according to power requirements. The rail voltage generates a square wave with a default frequency of 127.772 kHz and a duty cycle of 50% through the inverter circuit, which is loaded on the charging coil to generate a magnetic field. The main control chip controls the coil selection circuit according to the signal strength packet returned by the receiving end.
With CAN communication, it can communicate with other nodes in the body; with NFC tag protection, NFC mode (card detection, peer-to-peer and card simulation) and car control mode. In cars, NFC is not only used for infotainment functions, but also a technology that can safely unlock and start the car. The car control mode demonstrates a secure end-to-end authentication method, using NFC to start the car’s engine. This safety certification is achieved by exchanging APDUs, following the ISO7816-4 standard. In order to control the virtual engine, a challenge and response mechanism is implemented using the AES128-bit CBC algorithm.
Figure 2 Block diagram of the scheme
1. Features of ZLG 15W car wireless charging solution:
The design complies with Qi 1.2.4 specification;
Based on WPC MP-A9 topology;
Support frequency hopping, greatly reducing co-frequency interference;
Integrated on-chip digital demodulation;
Support multiple types of RX modulation signals;
Support security-oriented NFC function;
Support CAN communication;
The power transmission efficiency is as high as 73%;
Support FOD, based on Q factor change and calibrated power loss calculation.
2. Software debugging:
Provides Demo routines, supports secondary development, and can be designed flexibly according to the needs of end users.
There is a dedicated GUI tool, based on FreeMASTER, to facilitate the configuration and calibration of system parameters.
Three, program evaluation kit
Aiming at pain points such as cumbersome design of wireless charging products and low certification passing rate, ZLG has launched a complete in-vehicle wireless charging solution, providing complete software and hardware support. And provide the corresponding evaluation kit, which can be used for Qi protocol wireless charging evaluation, including wireless charging module, NFC module and CAN communication module, which is convenient for customers to quickly evaluate.
Figure 3 Main control board and coil
Figure 4 NFC antenna board
1. Demo kit composition:
Main board (bottom board);
Wireless charging multi-coil and shielding board (middle board);
NFC antenna board (top board);
2. Demo function:
Qi protocol wireless charging;
Metal foreign body detection;
CAN message sending and receiving;