Toyota Prius uses double-side cooled power module packaging

According to Nikkei Tech-on! Toyota has reduced by 30% the cost of its power converter by reducing  the size and number of the components.

This has been achieved by using two pairs of diode-IGBT in a module and cooling the module on both sides. This kind of power module packaging is not completely new. It has been already tested on Lexus LS600h hybrid since 2007. Lexus is part of Toyota group and manufactures high-end vehicles. Toyota, as a pioneer in hybrid electric vehicle, did try different types of power modules and cooling solutions on the different vehicles they released. Double sided was thought to be too expensive at the time. Scaling and integration into a sedan like Prius was not expected to happen so fast.

LS600h Lexus power module example

Toyota preferred to use custom designed power modules with standard cooling system in the power electronics converter of its hybrid cars when the first versions of Prius where released in 2006 and 2010.

It’s a new kind of power module that is now used in mass-production of hybrid cars, and its a new step in power module packaging innovation.

We need to note that this is in total opposite direction to the one chosen by Tesla Motors as pointed out in Point The Power insight article. Tesla preferred to use a proven power devices packaging technology for its Model S. They went for TO-247 which are an improvement from TO-220. The design of these packages date from the 1990’s. This choice seems to be made following cooling, reliability and control needs in the inverter. Indeed, Tesla’s inverter is driving much more current (up to 1500A) than the power inverter of an hybrid car like Toyota Prius.