The innovative developments in power electronics belong to the future key technologies in order to increase system efficiency as well as performance in automotive and energy-saving applications. Silicon is the major material for electronic switches for decades. Advanced fabrication processes and sophisticated electronic device designs have optimized the silicon electronic device performance almost to their theoretical limit. Therefore, to increase the system performance, new materials that exhibit physical and chemical properties beyond silicon need to be explored. A number of wide bandgap semiconductors like silicon carbide, gallium nitride, gallium oxide, and diamond exhibit outstanding characteristics that may pave the way to new performance levels.
ELE Times’s Correspondent Sheeba Chauhan had an exclusive interview with Stefan Obersriebnig, Product Line Head High Voltage Conversion of Infineon’s Power & Sensor System Division, and Steve Roberts, Innovation Manager of RECOM Power. This interaction covers majorly about the power electronics in Semiconductor and some major technologies ahead.
The new Smart Power initiative based on GaN technology
Talking of the same Stefan Obsersriebnig, Product line head of Infineon said that GaN offers the technological possibility to integrate high voltage power components like normally-off HEMTs and low voltage peripheral devices such as gate drivers, level shift, current and voltage sense circuitry onto one die with the same fabrication process. This allows creating devices that are highly integrated and provide all necessary circuitry within a single package for the highest power density and ease-of-use with “digital in, power out” behaviour.
While Steve Roberts, Innovation Manager of RECOM Power responded, Smart Power can refer to ways of cleverly managing existing resources to avoid energy poverty, especially in rural areas. The term is also used to describe managing power distribution in big cities and large factories to avoid grid interruptions and over-loads. Either way, the balancing of limited energy resources requires shifting power around efficiently. GaN technology is crucial to this concept because it allows power supplies to be made with efficiencies approaching 99%.
SiC and GaN technologies drive innovation and efficiency in tomorrow’s power electronics
Stefan Obsersriebnig responded that SiC and GaN are wide-bandgap semiconductors that enable higher electrical fields in the devices and thus thinner layers with higher doping for blocking the voltage. This reduces the required area for a given on-resistance, which decreases the parasitic capacitances. As a result, SiC and especially GaN can operate at much higher switching frequencies than their Si counterparts. This leads to smaller passive components and higher power densities of the power electronics systems. Furthermore, since in SiC and GaN no minority carriers are involved in the conduction phase, these devices can also be hard-switched. This means that new control schemes become possible, that, for example, use a mix of hard- and soft-switching over the load and/or input and output voltage ranges. This offers new degrees of freedom for designers of power electronic systems and higher efficiencies by choosing the optimal modulation scheme for each operating point.
Steve Roberts supported his response with some practical examples and said that GaN transistors are so efficient that they use a different construction and switching mechanism. A normally-off GaN is an example of a high electron mobility transistor (HEMT) in which the source and drain are positioned laterally. The crystal structure of GaN allows electrons to move very easily through it – so easily that it is called an electron gas. Thus the two terminals would be effectively connected together, were it not for a special depletion region formed under the gate electrode:
Thus to turn on (enhance) a GaN HEMT, the depletion region needs to be “canceled” by applying a small voltage to the gate, unblocking the connection between source and drain. This happens VERY fast making switching speeds from 100 kHz up to the MHz regions easily realizable.
For military or space applications, the inherent RadHard withstand capability of the lateral GaN over the vertical Si/SiC construction is also a major pull factor.
SiC transistors are similar to conventional Si-MOSFETs, but use a silicon carbide rather than a silicon substrate. SiC has a much higher breakdown voltage so the individual layers can be made thinner, reducing the switching capacitance and increasing the current handling capability. Thus SiC-MOSFET switches faster and with higher power density than an equivalent Si-MOSFET transistor.
How wide bandgap semiconductors are shaping the future of power electronics?
Stefan Obsersriebnig replied that wide bandgap semiconductors allow breaking the performance barriers of existing Si systems. Efficiency and power density are pushed to new levels, and also new applications are enabled. They play an important role in the electrification and de-carbonization of our lives, as not only less energy is wasted during the conversion processes, but also higher power levels can be processed in less space. As a bottom line, the future of power electronics is greatly shaped by wide-bandgap semiconductors since they open up new research vectors into advanced topologies, modulation and control schemes, integration concepts, filtering methods, and more.
Semiconductor solutions from Infineon support a stable and efficient flow with reduced losses, thus maximize efficiency along the power chain, all of it at high-quality standards for the highest reliability and improved sustainability.
While Steve Roberts stated that Progress on WBG transistors is so rapid, that the support technologies are struggling to catch up; controllers need to be developed with shorter lead times and propagation delays, magnetic materials need to be improved to offer better power performance at very high switching frequencies and the high DV/DT stresses on the isolation barriers may limit lifetimes if new low isolation capacitance products are not developed. RECOM is carrying out research on the long-term DC/DC converter isolation barrier reliability under high frequency switching stress as an isolated gate driver power supply is a critical part of all of these new technologies for both low-side and high-side switches.
The latest power solutions for industrial and automotive applications
Stefan Obsersriebnig responded that in the industrial domain, Infineon recently has introduced to the market new silicon generations such as IGBT7 or CoolMOS 7. New package platforms like EASY 3B have been added, extending the scope for power PCB embedded baseplate-less modules. Furthermore, power packages like QDPAK have been launched to shape the trend of top-side cooling. Next to our Si offering, the wide bandgap is growing substantially. As one example, smart combinations of silicon and silicon carbide chips are launched, offering an optimum cots performance solution to the customer, e.g. in ANPC topology. Furthermore, Infineon launched a broad range of CoolSiC 650 V discrete devices. On top, a compelling CoolGaN 600 V product portfolio addresses those applications and customers that demand superior efficiency especially in combination with ultimate power density.
WBG in automotive applications is also in Infineon’s focal point. At this year’s virtual PCIM trade show, Infineon has also presented the new HybridPACK Drive CoolSiC, a full-bridge module with 1200 V blocking voltage optimized for traction inverters in electric vehicles. The power module is based on the automotive CoolSiC trench MOSFET technology for high-power density and high-performance applications. This offers higher efficiency in inverters with longer ranges and lower battery costs, particularly for vehicles with 800 V battery systems and larger battery capacity. In addition, our power semiconductor solutions and smart control ICs enable multi-target optimization for system cost reduction, increased power density, higher application efficiency, and modular systems— supporting your preferred topology. Semiconductors, particularly the ones produced by Infineon, can play a vital role in building energy efficiency in all phases of the energy supply chain, especially in an electrified vehicle.
By minimizing power losses and maximizing power savings, they increase the overall performance of hybrid and electric vehicles. Our broad key technologies, including Si-based like IGBT and SJ MOSFETs, are addressing the cost-performance segment where WBG solutions based on SiC today and GaN in the future will enable high-performance optimization at the customer side.
Steve Roberts said that in the longer term, GaN technology will also offer massive reductions in AC power supply dimensions. Power densities of 40W/in² are already being developed, double or three times the power densities of conventional Si-based technologies. This means that industrial and medical customers can expect a new generation of AC/DC power supplies that fit into much smaller enclosures with minimal heat generation. As GaN is especially suitable for low-EMI, highly efficient resonant, or active-clamp flyback topologies, many bulky power supplies will be replaced with sleek new designs that will mean that future products will be designed more around the user interface than around the bulky power supply.
For example, RECOM’s next-generation GaN-enabled AC/DC products will offer a 60W AC/DC power supply with a footprint of 3”x1.6” instead of the industry-standard 4” x 2”, a reduction of 40% in size for the same power output.
The latest innovative SiC & GaN power solutions that make industrial and automotive systems smarter and greener.
Stefan Obsersriebnig responded that making life easier, safer, and greener is the mission of Infineon. Our products are being developed to support a more sustainable future. We added new SMD-based discrete products offering superior die attach and thermal cycling stability. New AlN-based modules are launched with SiC. 650V devices complement now the CoolMOS offering. The worldwide first 1200V SiC IPM was launched as well. The automotive world is evolving at an unprecedented pace.
At Infineon, we look back on 40 years of success and proven expertise in supplying high-quality semiconductors to power electronic systems for the automotive industry. One of the core beliefs is to make cars greener and therefore, Infineon is continuously investing in technologies to enable the transition to electrified vehicles faster and more efficient. Infineon WBG based solutions enable system size reduction by up to 80% thanks to higher power density, less cooling effort, and a lower number of passive components. Our customers can increase power density and power conversion efficiency. Both optimization directions are the key, especially in an electrified vehicle segment where higher efficiency can extend the driving range and power density simplifies design and enables higher capacity batteries to be installed in the same body.
SiC-based power electronics for xEV main inverter and Charging electronics (OBC + HV DC-DC converter) is accelerating; this is especially true in premium car segmentation today and volume class automotive tomorrow. To enable green power electronics, Infineon is investing in a broad product portfolio of SiC offering – 750 V and 1200 V SiC-based solutions. In the automotive sector, the portfolio was extended by further MOSFET-based products and hybrid solutions. GaN might be a potential successor of SiC to enable even higher power density in the future, and therefore Infineon will develop also GaN-based solutions for the automotive domain.
Steve Roberts replied astoundingly that Both SiC and GaN transistors switch faster, cleaner and have overall better thermal performance than IGBT (SiC through its chemistry – silicon carbide has about 3.5 times better thermal conductivity than Silicon, and GaN through its very low losses and efficient SMD packaging), but for many applications, super-junction MOSFETs and IGBTs still offer an acceptable performance at a much lower price. So, for many price-sensitive industrial applications, silicon-based technologies still have the edge over the new chemistries; for now, at least.
Furthermore, as WBG transistors are still in early development, the more mature IGBT technology offers higher switching voltages and currents than its younger rivals:
However, there are several key applications where the performance advantages of WBG are crucial: Electric vehicles (EVs) require higher efficiency (higher switching frequency) and better thermal performance (lower switching losses) than is currently available from Silicon-based technologies.
The overall efficiency of a plug-in EV is currently around 60% (conversion of mains power to the kinetic energy of the vehicle). WBG offers the prospect of improving the power control and battery charging efficiency so that the overall efficiency increases to 72%. This represents an effective range increase of more than 20% without changing the existing battery technology. This prospect of high-volume EV applications is very attractive for SiC and GaN technologies.
However, there are several key applications where the performance advantages of WBG are crucial: Electric vehicles (EVs) require higher efficiency (higher switching frequency) and better thermal performance (lower switching losses) than is currently available from Silicon-based technologies.
Sheeba Chauhan | Sub Editor | ELE Times
