Today the mobile phone is not just used to make calls or send messages, rather it has turned into a one-stop shop for value-add applications like GPS navigation, infotainment, social interaction, running vehicle manufacture related applications, data transfer, etc. While, on the one hand, the increase in average time spent by the user on the phone has led the phone makers to build more powerful, long-lasting batteries, there is however still a significant increase in data transfer over phone requiring frequent battery charging.
This growing trend to stay connected on the go in turn generates a parallel demand for easier, faster and safer charging infrastructure, which is both compatible as well as reliable, in passenger vehicles as average time spent in cars increases for users.
The conventional way of charging a phone using cables faces many limitations like cables may get tangled, connecting the cables while driving can be dangerous, connectors are not compatible to all phone ports, charging power from the USB connector may vary and long duration of charging.
To solve this problem, in-cabin wireless charging option has been developed. Wireless charging uses a changing magnetic field to transfer energy between two objects. Essentially, it uses a transformer with AC current in the primary coil that is reflected into the secondary coil in the same ratio, according to the coupling, and this current provides power to charge the battery. As a working principle, the coils in the receiver devices receive electrical power with the identical frequency and generate voltage that charges the device’s battery.
Infineon, along with its partner Spark Connected, offers an Automotive In-Cabin Wireless charging transmitter solution. This 15W charging solution supports Qi standard and fast charging mode. The solution is fully compatible with the automotive environment and operates from 6V-19V input battery supply condition, thus supporting the start-stop feature. It offers protection from load dump, double battery and reverse battery conditions. It supports built-in CAN interface for communication.
The design and development of wireless charger solution system present significant design challenges that include accurate foreign object detection (FOD), handling of EMI-EMC effects and thermal management. It is very important that wireless charging does not emit EMC that causes interference to other systems in a car. Many commercial Qi transmitters operate over a frequency range of 110-250 kHz, but most of the automotive original equipment manufacturers do not allow emissions above 150 kHz. It requires a completely different architecture than the off-the-shelf commercially available wireless transmitters. Infineon’s solution is CISPR25 class 4 certified with unique power drive architecture and controlled frequency operation that minimizes the EMI-EMC effects.
Another design challenge includes accurate detection of foreign objects while charging. Small objects are difficult to detect due to the small impact on the magnetic field of the large primary coil. A safety mechanism technique will prevent heating of metallic objects within the charging field. An improved version of FOD is required since the standard methodology relies on the large primary coil windings for detecting foreign objects which reduces sensitivity and signal to noise ration. Infineon’s solution improves the FOD method of measuring that includes detection of small foreign objects, which greatly increases sensitivity and signal to noise ratio. The FOD capability can be extended beyond the existing Qi standard. Wireless solution preforms other real-time measurements to ensure safe and stable power delivery through environmental changes.
The wireless power transmitter evaluation module is a high-performance, easy-to-use wireless charger solution. The transmitter detects presence of a wireless power receiver on its surface and starts the power transfer. The power level is controlled by the receiver via in-band communication data packets. The system supports WPC v1.24 receiver up to 15W, as well as all legacy Qi-compliant wireless charger for automotive applications. It supports multi-coil configurations (standard and custom). The three-coil transmitter provides the designer a certified platform that drastically reduces the development time of their end application. Smartphones with propriety fast charge capability are also supported. Additional features and changes in future standards can be supported by the easy to upgrade software feature.
Power switches control the selection of coil for power transmission. Internal regulator is used to supply micro-controller and pre-driver for a wide range of battery voltage from 6V-19V. It uses single Aurix MCU to support wireless charging, CAN and NFC functions.
Aurix is Infineon’s brand-new family of microcontrollers serving the needs of automotive, industrial and customer’s applications in terms of performance and safety. Developments using Aurix not only require less effort to achieve the SIL/IEC61508 standard based on its innovative safety concept and multiple hardware safety features. Thanks to its state-of-the-art safety features, the new Aurix TriCore enables systems to achieve the highest safety level up to ASIL-D.
Infineon’s Aurix wireless power controller, based on the TriCore, provides a flexible platform for high performance, smart and safe wireless charging applications. The Aurix wireless power controller helps the next-generation in-cabin wireless charging systems meet strict automotive safety, security, environmental and regulatory requirements, while still enabling industry-leading charging performance and efficiency.
Furthermore, Aurix has enhanced communication capabilities to support communication between CAN, LIN, FlexRay and Ethernet buses. The TC212 family belongs to the TC2xx Aurix 1st generation. Equipped with a TriCore with 133 MHz, 12bit SAR ADC convertor, a single voltage supply of 3.3V and a Powerful Generic Timer Module (GTM), the TC212 series aim for a reduced complexity, best-in-class power consumption and significant cost savings. MCU is available as single and lockstep core. TC212 offers 0.5MB of flash and 56KB of RAM memory with ECC protection.
Infineon has partnered with Spark Connected to offer complete end-to-end system design solutions to customers that cover support for system hardware designs, application software designs and wireless power system integration.
Key highlights:
System benefits of wireless solutions:
- WPC Qi v1.2.4 certified
- Supports 15W charging and all existing standards, including 7.5W and fast charge smartphones
- Charger is backward compatible with low power and legacy devices
- Easily support future standards with a software update
- Single MCU supports wireless charging, system application, CAN and external NFC interface
- Infineon power drive stage improves EMI performance 10-15 dB over existing solutions
- Precise frequency control to prevent adverse effects on other automotive systems
- CISPR 25 class 4 certified, unique power drive architecture to improve EMI
- FOD with improved accuracy quality-factor monitoring
- FOD capability can be extended beyond existing standards to improve detection
- Supports custom coils, and greater than three coils
- Supports charging two devices using a single controller
- Full power charging with a 6V-19V input supply, supporting start-stop feature
- Built in security functionality (HSM) meets latest automotive requirements
- Total front-to-back solution ensures maximum efficiency, minimal thermal impact and ease of certification
- Future path to Device Authentication (WPC Qi v1.3)
By Jahangir Mansoori, Staff Engineer for Automotive Application, Infineon Technologies India