Hitachi Automotive Systems delivers compact, high-output inverters and DC/DC converters for Mercedes Benz S500 PLUG-IN HYBRID

4 December 2014

Hitachi Automotive Systems, Ltd. has begun to supply Daimler AG with compact, high-output inverters and DC/DC converters for use in Daimler’s first plug-in hybrid—the S500 PLUG-IN HYBRID (earlier post) and S550 PLUG-IN HYBRID Long being marketed in Europe this autumn and Japan this month, respectively.

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Hitachi Automotive Systems developed a third-generation inverter offering about 40% smaller size and higher output than the company’s second generation product, and a high-output DC/DC converter with a maximum efficiency of 94%.

For reducing the size and increasing the power output of an inverter, it is essential to boost the heat dissipation performance of the power module, which integrates numerous high heat emitting power semiconductors. In second-generation products, heat dissipation was improved by developing a directly water cooled power module that did away with the thermal grease that tended to impede heat radiation.

In third generation products, the ability to eliminate heat was further improved by developing a direct double-sided cooling power module that involved switching from the conventional semiconductor one-side cooling structure to a structure for cooling both major semiconductor surfaces.

The newly developed power module achieves a 35% improvement in heat dissipation performance over the second generation module by utilizing a proprietary cooling structure that immerses the module in cold water. It reduces size and increases power output by around 40%.

A DC/DC converter that achieves a maximum efficiency of 94% was realized by installing a proprietary active clamp circuit, in combination with a high heat emitting transformer and a low loss, high heat dissipation choke coil structure.