Better On-Board Charging with Added Functionality

The large EV market has given component manufacturers a huge commercial target to aim at, while the availability of advanced components has increased the performance of EVs to an extent that they are now desirable to a much wider base of customers. According to Dr. Gerald Deboy, Distinguished Engineer Power Semiconductors and System Engineering at Infineon, there are plenty more improvements to come, and he further explains how Infineon is perfectly positioned to take advantage.

One of the areas that Dr. Deboy identified as offering the greatest opportunity for improvement, at least in the short-term, is in on-board chargers, especially in the plug-in hybrid sector. The latest silicon carbide technologies will allow designers of on-board chargers to offer customers additional value and differentiation to designs. For example, bidirectional connectivity will allow owners to connect the vehicle to the power grid to supply cheap electricity to the home in peak hours, while recharging in off-peak times. Bidirectionality could also be used to add new features, such as the ability to power tools in work vehicles. Phase-modular systems could also be designed into on-board chargers by manufacturers to provide more flexibility for the owner to use multiple grid configurations. Finally, magnetic integration of the on-board charger would allow a high-voltage-to-low-voltage DC/DC converter to be included into the charger for more compact designs. This, in turn, will allow more flexible bidirectional operation between the batteries in the vehicle and the outside world.

Dr. Deboy claims Infineon’s SiC process gives the company an inherent advantage over other manufacturers. In particular, Infineon purchased Dresden-based startup Siltectra in 2018 for 124 million Euros. Siltectra had developed a cold split technology that allows wafers to be processed and split more efficiently, with much less wastage. That process allows Infineon to double the number of chips it can extract from a single wafer, reducing costs considerably. A second major advantage of Infineon SiC products is that they are designed to be as robust as IGBT-based systems while offering a much higher level of performance. In normal SiC DMOS technology, the designer has to make a trade off between performance and gate oxide robustness when the device is in the on-state. Infineon’s advanced trench technology makes it easier to reach performance targets without violating the gate oxide safe condition. The advanced trench technology is based on a MOS channel that is vertically oriented to structurally protect the gate oxide effectively by providing a safer current path through the device.

One last advantage that Dr.Deboy highlights for the company’s SiC technology allows it to be used to replace silicon or GaN in some areas. The R_DS(on) value of the company’s SiC devices is more stable over the temperature scale than other materials. This allows cheaper SiC components with an initially higher R_DS(on) figure to be used, as when the device reaches typical operating temperature, the R_DS value will be almost the same for the SiC device, but much higher for the GaN and silicon devices. For example, where the initial datasheet values of the three technologies look similar at 25^oC, while operating at 100 °C, the R_DS(on) of the CoolSiC device is 26% lower than CoolGaN device and 32% lower than CoolMOS.

In a practical example of a 3KW totem pole supply, SiC technology could reach 99% with a 94 mΩ R_DS(on) device in comparison to GaN where a 70 mΩ device was required to provide the same performance at 100 ^oC. That translates into a cost advantage for SiC. Dr. Deboy believes that the cost effectiveness of SiC devices will make them the primary choice for a totem pole architectures running at a relatively low switching frequency of 40 to 60 KHz.

Together the advantages of Infineon SiC technology mentioned above will allow automotive manufacturers to be more creative with designs for on-board chargers and other power architectures. The SiC devices will deliver power densities as high as 4KA/I and bring the potential of integrating 3-phase systems, DC/DC converters and multi-port magnetics into the on-board charger, while at the same time allowing bidirectional operation and catering for higher battery voltages. 

http://infineon.com