EV HEV Charger: Level 3

Block Diagram

Design Considerations

Plug-in Hybrid Electric Vehicles (PHEV) and Battery Electric Vehicles (BEV) are two rapidly emerging technologies that use powerful electric motors and high voltage battery packs as a source of power. Due to the limited capacity of the battery, PHEVs and BEVs must be recharged periodically, which is usually done by connecting to the power grid. When this is done, some form of communication (PLC, wireless or RFID) can be used to manage charging activities and help identify and authenticate the car or be used by the owner for billing purposes. Level 3 charging will play an important role in the public charging field to reduce charging time and enable users to benefit from mobile charging.

The Level 3 charging system for these cars consists of an AC/DC converter that generates a DC voltage from the AC line. These input sources need to undergo power factor correction (PFC) to improve the power factor to meet regional regulatory standards. At the heart of the inverter is a real-time C2000 microprocessor. This controller is programmed to execute control loops to implement all required power management functions, including AC/DC with PFC and DC/DC to create the required battery charging profile. The C2000 controller includes advanced peripherals such as high-precision PWM outputs and ADCs that can read the ADC and adjust the PWM in a single clock cycle, enabling real-time control.

While the C2000 manages power, the host controller is responsible for driving the display and communicating directly with the onboard battery pack using information provided by the communications modem and temperature sensing. Necessary information for the charging profile is sent to the power controller, while important charging diagnostics and battery status are sent to the display of the 3-level charging system.

For safety reasons, it is also necessary to isolate the processor and the current and voltage, as well as the communication bus to the outside world. TI digital isolators have logic input and output buffers that are isolated by TI's silicon dioxide (SiO2) isolation barrier, which provides 4kV isolation. When used with isolated power supplies, these devices can block high voltages, isolate grounds, and prevent noise currents from entering the local ground and interfering with or damaging sensitive circuits. High-performance analog parts can also provide important system functions such as MOSFET drivers, sensor feedback, chip power supplies, and communication transceivers.

Communications on a single system can be handled by a single processor. More sophisticated systems with complex displays and online billing/reporting (e.g., Level 3 charging) may also require a controller. Implementing a low-frequency narrowband PLC (LF NB PLC) solution will provide the best fit for bandwidth, power and cost requirements. Operating in the narrowband domain (up to 500kHz) ensures data integrity while minimizing system cost. To do this, the standard will leverage existing power line infrastructure and provide a cost-effective way to integrate intelligent monitoring and control into new automotive electronic systems. Data rates range from 1.2kbps to hundreds of kbps, depending on existing standards. TI's PLC software is available through the plcSUIte library, allowing developers to support multiple modulations and standards in a single unique design. Developers can implement SFSK IEC61334, PRIME and G3 standards, use FlexOFDM for custom OFDM implementations, and can also be upgraded for future standards. For more information, visit our PLC applications page. Additionally, wireless communication and/or RFID may be required as a second communication protocol and a means of identification and billing.