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Best three Design Things to consider for EV Charging

Available for commercial and residential use, a typical electric vehicle (EV) charging station design includes energy metering, AC and DC residual current detection, isolation for safety compliance, relays and contactors with drive, two-way communication, and service and user interfaces. While the objective of a charging station would be to efficiently transfer power to an automobile, implementing that power transfer is only the start of its role.

By 2030, approximately 20 million public EV charging stations will connect with the grid, with residential charging stations expected to scale significantly to parallel the demand, according to recent reports from IHS Markit. An EV charging station design includes unique challenges. Electric vehicle supply equipment (EVSE) must incorporate communication, security and safety, while providing a simple upgrade path in order to accommodate the future of grid integration. In this article, I'll briefly introduce three design considerations utilized in a scalable hardware and software demo using TI's Sitara AM625 processor for any Level 2 AC EV charging station.

Design consideration No. 1: Understanding future communication standards and grid integration

Future EVs are required to serve as powers by returning stored energy back to the grid during periods of high demand or power outages. Managing this potential exchange of energy is an aspect of grid integration which makes communication a critical design consideration in EV charging stations. For both the vehicle charging indicate the grid, along with the charging station towards the cloud, the front- and back-end communication design must meet standards for data, security and safety in the charging process, as shown in Figure 1.

Figure 1: V2G technology

The International Organization for Standardization (ISO) 15118 standard outlines a bidirectional communication protocol between your EV and charging station, enabling the exchange of information for car identification, charge control and charging status to enable features for example plug and charge. Incorporating front- and back-end communication requirements to meet ISO 15118 standards enables compliance today and style longevity for future years of grid integration.

Selecting the right level of processor integration and software capability today can enable simple optimization for grid integration tomorrow. The Sitara AM625 utilized in the EV charging design shown in Figure 2 features a mainline Linux kernel having a standard software development kit to ensure efficient maintenance and simplified updates. The AM625 processor also supports secure boot for IP protection having a built-in hardware security module (HSM), and employs advanced power-management support to optimize system power consumption when idle.

Figure 2: AC charger block diagram; DC charger block diagram

Design consideration No. 2: Leverage a module-based design for flexible AC or DC charging options

Determining the best connectivity solution for an EV charger includes thought on its use case, environmental surroundings in which it is going to be installed, and scaling for grid integration. Commercial EV chargers typically require cloud connectivity to manage billing distribution as well as car data insights, and you'll have to think about the potential of centralized data management between multiple charging points. Residential chargers may ultimately be an extension of the smart home and can have to integrate with existing wireless and wired networks.

The Open Charge Point Protocol (OCPP) may be the standard of communication defined between charging stations and also the charging station network that manages data exchange. Designing for this protocol requires choices for multiple connectivity and is achievable with Ethernet, cellular, Wi-Fi(R) or Sub-1 GHz signals.

To address the challenge of flexibility with OCPP readiness, EV chargers need to have multiple connectivity options. For instance, WiFi is ubiquitous. So, it can be used for connecting EV charger to existing infrastructure or provide local connectivity for charging station network where wired connection is not feasible. When EV chargers are deployed in challenging RF environments like underground parking garages, lower frequency communication like Sub-1GHz is preferable to LTE for connection reliability. Regardless of whether the design is for residential or commercial use, or even the location of the charger, the look will need a connectivity solution that is flexible and reliable.

Choosing the best connectivity solution means supporting higher operating temperature ranges ensure stable connection even just in harshest environments with significant temperature changes. Also ensuring interoperability with commercial or home networks. The WL1837MOD WiLink 8 module from TI offers excellent RF performance and powerful interoperability along with other WiFi devices. It also has integrated Bluetooth for simple provisioning and deployment. Coupled using the production-ready Phycor-am62x multicore Arm-based processor system-on-module from Phytec, the WL1837MOD offers both ecosystem software compatibility for simple third-party software integration and an upgrade path for future migration and optimization of OCPP 2.0.1 and above.

Design consideration No. 3: Managing longevity with security and safety options.

With the way forward for ISO 15118 and OCPP 2.0.1 evolving toward increasing data insights for vehicle and user data, secure software is essential for both connectivity and communication. The processor will play a vital role in enabling a scalable future for EV charging, acting as a mix of system monitor for data quality and charging levels while providing a secure gateway for insights into payment and vehicle data.

Both the application and transport layers of ISO 15118 enable data security. Transport Layer Security (TLS) 1.2 or higher encrypts the transport layer communication. Although ISO 15118-2's TLS is only mandatory while using the plug-and-charge identification mechanism, TLS is mandatory later on ISO 15118-20 standard for those use cases and all sorts of identification mechanisms. The AM625 has onboard HSM security measures such as:

  • Secure boot:
  • Self-programmable hardware (eFuse) keys.
  • Support for encrypted and authenticated boot.
  • Debugging (Joint Action Group) port:
  • Closed automatically on high-security devices.
  • An eFuse setting allows permanent closure.

There are multiple aspects of safety built into every EV charging design, including secure internet connections, monitoring for ground faults, relay driving and high-voltage isolation. TI's DRV8220 motor-driver integrated circuit comes with an integrated H-bridge, logic control and protection to enable simple implementations of plug locks, ground fault monitoring and relay drivers.


The EV charging industry is evolving, increasingly standardized, intelligent and efficient. Designers must include flexible connectivity and security to enable long-term integration using the grid. Selecting the right processor-based design necessitates thought on increasing>Authored by:

Errol Leon, System Engineer, Texas Instruments