Highest power density for DC/DC converters demonstrated

DC/DC converters are essential to connect the high-voltage battery to the low-voltage auxiliary circuits in any EV or HEV. This includes 12V power headlights, interior lights, wiper and window motors, fans, and at 48V, pumps, steering drives, lighting systems, electrical heaters, and air conditioning compressors. Also, the DC/DC converter is important for developing more affordable and energy-efficient vehicles with increasing low-voltage functions. GaN, in particular, plays a crucial role here, as it can be employed to improve the power density in DCDC converters and OBC. For this reason, Vitesco Technologies has selected GaN to improve the power efficiency of its Gen5+ GaN Air DC/DC converter. The CoolGaN Transistors 650V from Infineon Technologies AG significantly improve the overall system performance while minimising system cost and increasing ease of use. As a result, Vitesco created a new generation of DC/DC converters that set new standards in power density (efficiency of over 96%) and sustainability for power grids, power supplies, and OBCs.

The advantages of GaN-based transistors in high-frequency switching applications are significant, but even more important is the high switching speed, which has been increased from 100kHz to over 250kHz. This allows low switching losses, even in hard-switched half-bridges, with minimised thermal and overall system losses. Also, the company's CoolGaN Transistors feature high turn-on and turn-off speeds and are housed in a top-cooled TOLT package. They are air-cooled, eliminating the necessity for liquid cooling and lowering overall system costs. The 650V devices also improve power efficiency and density, enabling an output of 800V. In addition, they feature an ON-resistance (R _DS(on)) of 50mOhm, a transient drain-to-source voltage of 850V, an I _DS,max of 30A, and an I _DSmax,pulse of 60A.

"We are delighted to see industry leaders like Vitesco Technologies using our GaN devices and innovating with their applications," said Johannes Schoiswohl, senior vice president and general manager, GaN Systems Business Line Head at Infineon. "The ultimate value of GaN is demonstrated when it changes paradigms, as in this example of moving from a liquid-cooled system to an air-cooled system."

With GaN Transistors, Vitesco Technologies could design its Gen5+ GaN Air DC/DC converters with passive cooling, reducing the system's overall cost. The GaN devices also provide for simplified converter design and mechanical integration. As a result, the converters can be flexibly positioned in the vehicle, decreasing the workload for manufacturers. The use of GaN also allows the power of the converters to be scaled up to 3.6kW and the power density to be increased to over 4.2kW/l. The converters offer an efficiency of over 96% and improved thermal behaviour compared to the Gen5 Liquid-Cooled converters. They provide a two-phase output of 248A at 14.5V continuous. The phases can be combined to achieve the maximum output power. Still, it is also possible to switch off one phase under partial load conditions and interleave the switching frequency between the two phases. In addition, by switching the input of two phases in series, the converters based on the CoolGaN power transistors 650V can be used to implement 800V architectures without exceeding the maximum blocking voltage of the device. The converters also feature an isolated half-bridge topology consisting of a GaN-based half-bridge, a fully isolated transformer, and an active rectifier unit for each phase.