Weesp (The Netherlands), August 27, 2007 – DENSO Corporation has developed a high-output power control unit (PCU) for the Lexus LS 600h and the Lexus LS 600hL, launched by Toyota Motor Corporation in Europe this summer.

The PCU consists of a boost converter that raises the main battery voltage (288V) up to the maximum system voltage (650V), and two inverters that convert direct current (DC) into alternating current (AC) to drive the main traction motors. DENSO’s new PCU produces approximately 60 percent higher output power per unit volume compared to the company’s conventional technology, thus improving hybrid system performance. When compared to a conventional design with the same output, the new PCU is approximately 30 percent smaller and 20 percent lighter.

To achieve higher PCU output, the power semiconductor devices used in the PCU are required to handle more power, resulting in more heat. For this PCU, DENSO developed a unique cooling structure that significantly improves the cooling performance of the power devices. 

In DENSO’s new cooling structure, the power devices are sandwiched between two heat sinks and inserted in layers between stacked cooling tubes (Fig. 1). This structure allows both sides of the power devices to be cooled, which substantially enhances cooling performance, compared to a conventional cooling structure where power devices are mounted horizontally with only one side facing the cooling unit (Fig. 2). The new cooling structure is also more compact than the conventional structure.

Since both sides of the power devices are soldered to the heat sinks, DENSO reduced the thickness of each power device to ease stress on joint portions, ensuring high reliability.

The new PCU design can easily be used in hybrid systems with different output levels by changing the number of stacked power devices and cooling tubes.

DENSO has been providing a variety of products for hybrid vehicles since 1997. Using its experience and expertise, DENSO will continue to create new technologies and products for vehicles that are less harmful to the environment.

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