“With the popularity of mobile phones supporting wireless charging, wireless chargers have also begun to enter the car. ZLG has launched a complete set of in-vehicle 15W wireless charging solutions to address industry pain points such as cumbersome wireless charging product design and difficult certification. The MWCT1013A based on NXP is the main control design, adopts MP-A9 topology, three coils, and has CAN communication and NFC functions. Provide comprehensive 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. ZLG has launched a complete set of in-vehicle 15W wireless charging solutions to address industry pain points such as cumbersome wireless charging product design and difficult certification. The MWCT1013A based on NXP is the main control design, adopts MP-A9 topology, three coils, and has CAN communication and NFC functions. Provide comprehensive software and hardware support to help customers pass Qi standard certification.
1. Wireless charging standard
The Wireless Power Consortium was established on December 17, 2008, and more than 600 companies have joined the consortium. The Qi standard developed by it is the most widely used wireless charging standard in 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 are derived. The automotive-grade wireless charging solution commonly uses the MP-A9 topology, with three coils, requiring a rail voltage range of 1~25V, a resolution higher than 25mV, an initial default frequency of 127.772 kHz, and a coil current acquisition accuracy higher than 7mA. Power adjustment uses PID The inverter circuit is a full-bridge fixed-frequency control circuit.
2. Car wireless charging solution
ZLG’s car wireless charging solution uses NXP’s MWCT1013A as the main control, the car 12V battery is used as the power supply, and the 5V voltage is generated by EMI filter and DC-DC to supply power for LDO, MOSFET driver and CAN transceiver. The 3.3V output by the LDO mainly powers the WCT1013A and the NFC chip.
The digital full-bridge BUCK-BOOST circuit adjusts the output 1~25V rail voltage according to power requirements. The rail voltage is generated by the inverter circuit to generate a square wave with a default frequency of 127.772 kHz and a duty cycle of 50%, 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 receiver.
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 is also a technology that can safely unlock and start the car. Car Control Mode demonstrates a secure end-to-end authentication method that uses NFC to start the car’s engine. This security authentication is achieved by exchanging APDUs, following the ISO7816-4 standard. To control the virtual engine, a challenge and response mechanism is implemented using the AES128-bit CBC algorithm.
Figure 2 Scheme block diagram
1. Features of ZLG 15W car wireless charging solution:
l The design conforms to Qi 1.2.4 specification;
l Based on WPC MP-A9 topology;
l Support frequency hopping, greatly reduce co-channel interference;
l Integrated on-chip digital demodulation;
l Support various types of RX modulation signals;
l Support security-oriented NFC function;
l Support CAN communication;
l Overvoltage/overcurrent/overtemperature protection;
l The power transmission efficiency is as high as 73%;
l Support FOD, based on Q factor change and calibrated power loss calculation.
2. Software debugging:
l Provide Demo routines, support secondary development, and can be flexibly designed according to the needs of end users.
l There are special GUI tools, based on FreeMASTER, to facilitate the configuration and calibration of system parameters.
3. Program Evaluation Kit
Aiming at the pain points of cumbersome design of wireless charging products and low certification pass rate, ZLG has launched a complete solution for in-vehicle wireless charging, providing complete software and hardware support. Corresponding evaluation kits are also provided, 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 consists of:
l Main board (bottom board);
l Wireless charging multi-coil and shielding board (middle board);
l NFC antenna board (top board);
2. Demonstration function:
l Qi protocol wireless charging;
l Metal foreign body detection;
l Over temperature/overvoltage/undervoltage protection;
l CAN message sending and receiving;
l NFC function.