Silicon carbide (SiC) is a promising material to use in power devices for hybrid vehicle power control units (PCU). Compared to current power devices made of silicon (Si), SiC power devices are expected to help PCUs produce higher power with a smaller size, since SiC can withstand higher voltage and higher temperatures with less power loss than Si.

One of the biggest hurdles in commercializing SiC power devices is the need to create SiC wafers with the high crystallinity required in on-vehicle power devices. DENSO has been working to produce higher crystalline SiC wafers, and succeeded in producing SiC wafers with the smallest level of defect density in the world-some hundreds per 1 square centimeter.

This year DENSO introduced a new PCU for the Lexus LS 600h and the Lexus LS600hL.

The PCU consists of a boost converter that raises the main battery voltage (288V) to the maximum system voltage (650V), and two inverters that convert direct current (DC) into alternate current (AC) to drive the main traction motors. For the PCU, DENSO developed a unique cooling structure that significantly improves cooling performance for the power devices. As a result, the newly developed PCU can produce output power that is approximately 60 percent higher per unit volume, compared to the company's conventional technology, thus improving hybrid system performance. When the PCU is designed to produce the same output as conventional technology, it can be reduced approximately 30 percent in size and approximately 20 percent in volume.

DENSO will continue to develop innovative technologies using its wide range of technologies and make hybrid products more compact and inexpensive while improving their performance.