Wide Bandgap Semiconductors – Increasing Charger Performance

(Joseph Gottlieb, CTO, Tuesday December 8, 2020)

One of the most exciting developments in power electronics in the past decade has been theemergence of wide bandgap semiconductors such a silicon carbide (SiC) and gallium nitride (GaN) for power electronics. Wide bandgap semiconductors have several interesting properties that make them a great  replacement for doped silicon in power electronics: high thermal conductivity; a low coefficient of thermal expansion; high maximum current density; a breakdown voltage of nearly 10kV; and very high switching speeds when compared to silicon-based power electronics. Even though wide bandgap-based semiconductors are significantly more expensive than standard silicon insulated gate bipolar transistor (IGBT) components, their superior capabilities allow systems based on them to be significantly smaller than silicon-based systems.

The first wide bandgap semiconductor components were launched in 2011 (they were based on SiC), with application in emerging industries such as renewable power (wind, thermal, and solar), and electronic drive trains for electric vehicles (EVs). For EV chargers, especially high-power DC charging systems for medium/heavy duty (M/HD) EVs, wide bandgap semiconductors allow a rack-size cabinet (which can hold a 60kW charger today using IGBT designs) can now accommodate a 120kW charger. Just as  importantly, the efficiency of SiC and GaN based systems are significantly greater than that of IGBT-based systems. This not only reduces energy losses, but also increases the reliability of these systems by reducing component junction temperatures. Rhombus is actively developing M/HD EV chargers based on wide bandgap semiconductors so that we can bring these capabilities to our customers and improve our market-leading reliability.

Rhombus has built high-power inverters for renewable energy such as “behind the meter” grid energy storage systems for several years. We have applied that expertise to the design of our latest-generation bi-directional EV charging systems (which are designed from the start for the needs of fleet operators) and bi-directional smart inverter systems for microgrids. Rhombus expertise in energy management system (EMS) software is also embedded in our VectorStat EMS controller and software which is embedded in our EV charging systems and smart inverters. Rhombus also excels in the design and testing of high-power electrical equipment to meet the requirements of UL and other certification organizations. We have built hundreds of V2G-capable high-power, high-reliability chargers and bi-directional smart inverters for a variety of different sizes and classes of EVs. Find out how we can help you by contacting us at news@rhombusenergy.com, or by reading our Vehicle to Grid Solution Brief.