Hiroshi Nakatake

Low on-resistance 1.2 kV 4H-SiC MOSFETs integrated with current sensor

4H-SiC MOSFETs integrated with a current sensor have been fabricated for the first time. The MOSFET shows superior characteristics with a specific on-resistance of 3.7 mΩcm2 and a blocking voltage of 1.4 kV. The deviation of the current ratio (Imain/Isense) stays within 10% in the temperature range between 25°C and 175°C, which is desirable for the current sensor of high power devices. Furthermore, the main current shut-off operation at an over-current detected using the current sensor has been demonstrated successfully.

Switching Characteristics of SiC-MOSFET and SBD Power Modules

Prototype SiC power modules are fabricated using our class 10 A, 1.2 kV SiC-MOSFETs and SiC-SBDs, and their switching characteristics are evaluated using a double pulse method. Switching waveforms show that both overshoot and tail current, which induce power losses, are suppressed markedly compared with conventional Si-IGBT modules with similar ratings. The total switching loss (MOSFET turn-ON loss, turn-OFF loss and SBD recovery loss) of SiC power modules is measured to be about 30% of that of Si-IGBT modules under the generally-used switching condition (di/dt ~250A/μs). The three losses of SiC modules decrease monotonically with a decrease in gate resistance, namely switching speed. The result shows the potential of unipolar device SiC power modules.

High Power-Density SiC Converter

A compact SiC converter having power densities about 9 W/cm3 is designed and fabricated. It is confirmed that the converter operates in a thermally permissive range. The power loss of the module of the converter measured under motor operations is less than 50% of the similar-rating Si module loss. The shrink of the effective volume of DC-link capacitor is necessary to achieve the high power-density SiC converter, in addition to the decrease of the cooling system volume due to the loss reduction caused by SiC devices.