Vitesco Technologies has boosted the performance of its fifth generation automotive DC-DC converter, incorporating a move from liquid to air cooling, writes Nick Flaherty. This Vitesco Gen5+ DC-DC converter uses 650 V CoolGan transistors from Infineon Technologies to achieve an efficiency of over 96% by increasing the switching frequency from 100 kHz to 250 kHz with an energy density of 4.2 kW/l.

Using gallium nitride CoolGaN transistors at 250 kHz enables lower switching losses, even in hard-switched half-bridges, with minimised thermal and overall system losses. The GaN devices have a lower on resistance of

50 mΩ compared with the previous design and the design handles a maximum constant of 30 A and a peak current of

60 A at a voltage of 850 V, even though the devices are rated for 650 V.

A chip package with the cooling on the top, called TOLT, allows air-cooled designs that eliminate the need for liquid cooling and reduce the overall system costs and energy density. “The ultimate value of GaN is demonstrated when it changes the design, as in this example of moving from a liquid-cooled system to an air-cooled system,” said Johannes Schoiswohl, senior vice-president & general manager, GaN gystems business line head at Infineon.

In an automotive application the DC-DC converter is connected to an 800 V battery pack to provide 12 V power for headlights, interior lights, wiper and window motors, fans; and at 48 V, pumps, steering drives, lighting systems, electrical heaters, and air conditioning compressors. The smaller size that comes from air-cooling rather than liquid cooling allows the converters to be flexibly positioned in the vehicle.