10Base-T1S Monitoring Solutions of SiC EV Fast-Charger Modules

Article By : Sonu Daryanani

10Base-T1S single pair Ethernet and BLE help monitor the availability and reliability of SiC power modules.

The EE Times Green Engineering Summit that took place from September 13-15 2022 included presentations from experts across a wide range of industries. The theme of this summit was the approach towards a more sustainable, lower carbon footprint future from the generation and storage of renewable energy, manufacturing of essential components and systems in a more efficient way, the use of electronics to give real time control in agriculture, as well as environmental monitoring and modeling.

In this article we will focus on the presentation given by Jonathan Harper, Member of Technical Staff at onsemi. The presentation was titled “Improving EV fast charger availability and reliability using 10Base-T1S single pair Ethernet and BLE”. Maurizio Di Paolo Emilio, Editor-in-Chief of Power Electronics News and EEWeb moderated the session. onsemi is a leading manufacturer of silicon (Si) and silicon carbide (SiC) based power devices that can be used for a wide range of applications including in the use of energy conversion and charging systems. Some examples of these include solar string inverters for photovoltaic (PV) systems, Electric Vehicle (EV) chargers, and in decentralized Energy Storage Systems (ESS) such as for micro-grids. All of these systems are on a fast growth path, as shown in Figure 1, as the world reacts to the need to build greener and more sustainable energy generation systems and loads systems.

Figure 1: Growth in some of the key future renewable energy applications
Figure 1: Growth in some of the key future renewable energy applications

SiC offers many advantages over Si in these applications with its wide band gap, lower parasitics and superior thermal conductivity. This translates to faster switching with improved efficiencies, power densities and a more compact system. Looking specifically at EV chargers, SiC based ones can enable cars to be charged within 20-30 minutes.

The SiC charger would typically be built as a number of parallel modules that together provide the total power needed. For example twelve 25 kW blocks could be used in a 300 kW charging station. Harper pointed out that the status of each module needs to be monitored. Due to parametric mismatch between the devices or other reasons, one of the modules may be running hotter than the others. Remote monitoring of the modules to measure some of the basic characteristics such as fault conditions in the gate drivers, current drawn and temperature can then be used to judge the real-time condition of each one.  Such data would be very valuable to accurately get a sense of the availability and reliability of each module and ensure that system level maintenance can be performed in a timely fashion.

A traditional Ethernet solution would necessitate that each module be connected to its own 4-pair cable. The controller, to access data from each module, would then use a switch. This is a point to point based and is expensive to implement in a parallel system such as the EV charger. A more elegant solution showcased in this presentation uses the 10base-T1S Ethernet standard [1]. The 10base-T1S was developed as part of the IEEE 802.3cg-2019 specification. It is a zonal architecture with broad support in the automotive industry. One of its main features is a multi-drop topology where many nodes are connected over the same twisted pair cable, as shown in Figure 2. This eliminates the need for a switch leading to fewer cables. Each node connects to one pair of wires, instead of the four normally used in Ethernet cabling. The S in the name stands for short reach, which is specified as 25 m for the bus length. All nodes share the 10 Mbit/s bandwidth, with a single PHY needed at each node.

Figure 2: The 10Base-T1S Multi-drop architecture
Figure 2: The 10Base-T1S Multi-drop architecture

On this shared network, data transfer is done through a Physical Layer Collision Avoidance (PLCA) protocol. The PHY on each node gets a transmit opportunity which is then moved to the next node in a round-robin manner.  A frame of data can be transmitted on each opportunity and if a node has no data to transmit it hands over the transmit opportunity to the next node, and a new cycle is started when the master node sends a beacon. In this manner almost the full 10 Mbit/s bandwidth is utilized in an efficient way. 10Base-T1S can provide faster communication in automotive than existing CAN based communication systems and is cheaper than the faster 100Base-T1 systems.

onsemi has developed a solution that provides a Bluetooth (BLE) interface for a local diagnostic interface on each module as well as 10Base-T1S based Ethernet connectivity for remote monitoring. This is based on the RSL10/RSL15 microcontrollers [2] with the BLE interface and the NCN26010 Ethernet MAC/PHY chip [3], as shown in Figure 3. The RSL15 chips feature a secure controller that supports a simple interface to a web browser and controls the NCN26010 chip. The NCN26010 is a small package as shown in Figure 3. With onsemi’s unique Enhanced Noise Immunity feature and collision masking techniques, it is possible to achieve much further distances and node counts than specified in the standard.

Figure 3: Schematic of the BLE and 10Base-T1S EV Charger connectivity solution with the RSL10/RSL15 and the NCN26010 chips
Figure 3: Schematic of the BLE and 10Base-T1S EV Charger connectivity solution with the RSL10/RSL15 and the NCN26010 chips

The RSL15 is the newer part that can replace the RSL10 in this application. It is an ultra-low power ARM™ based controller with a secure Flash memory and low energy BLE 5.2 communication capability.  A block diagram of this controller is shown in Figure 4. onsemi provides the firmware and software support for the user to create a web browser based monitoring solution.

Figure 4: RSL15 Micro-Controller Block Diagram
Figure 4: RSL15 Micro-Controller Block Diagram

The NCN26010 block diagram is shown in Figure 5. This MAC/PHY Ethernet part is 10Base-T1S protocol compliant and can use the SPI bus to communicate with the RLS15 controller. onsemi has drivers and free RTOS and Lightweight IP examples in [3].

Figure 5: NCN26010 Ethernet Chip Block Diagram
Figure 5: NCN26010 Ethernet Chip Block Diagram

References

[1] https://www.ieee802.org/3/cg/public/Jan2019/Tutorial_cg_0119_final.pdf

[2] https://www.onsemi.com/products/wireless-connectivity/wireless-rf-transceivers/rsl15

[3] https://www.onsemi.com/products/interfaces/ethernet-controllers/ncn26010

 

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