Denso Corp exhibited an inverter with an output power density of 60kW/L and disclosed its details at the 2012 Automotive Engineering Exposition, which took place from May 23 to 25, 2012, in Yokohama, Japan.
The volume of the inverter is 0.5L. The output density of 60kW/L was recorded when the output was 30kWh. At that time, the temperature of the power device rose to about 180°C.
Denso also reduced power loss. Compared with an inverter using a silicon (Si)-based IGBT, it is possible to reduce power loss by 68% (30Arms). The inverter consists of (1) a module equipped with silicon carbide (SiC)-based power devices, (2) control circuit that drives the devices, (3) cooling fin, (4) cooling fan, (5) capacitor, etc.
For the inverter module, Denso employed a SiC-based trench MOSFET as a transistor, and it uses the body diode in the MOSFET as a diode to reduce module size. The withstand voltage and on-resistance of the SiC-based MOSFET are 1,200V and 30mΩ, respectively. Its chip size is approximately 5 x 5mm.
The inverter module is equipped with SiC-based MOSFETs for the high and low sides (for three phases). For each of the high and low sides for one phase, three SiC-based MOSFET chips connected in parallel are used. Therefore, the entire inverter module has 18 chips.
The MOSFET approximately measures 5 x 5mm. It is possible to flow a current of 100A, but, this time, Denso designed the chip so that a current of 70A flows with three chips. In other words, a current of 23A flows in each chip. Also, the company reduced inductance components of the inverter module's package.
Denso developed the new inverter in a joint research and development project with Toyota Motor Corp and Toyota Central R&D Labs Inc.