| dc.description.abstract | The dynamic measurement of the devices employs the double pulse test (DPT). The primary operating modes for double pulse test include resistive load and inductive load. In this study, the dynamic measurements use the inductive load mode. In this mode, apart from the device under test (DUT) as the switching device, an additional freewheeling diode is required to provide a current path when the DUT is turned off. The reverse recovery characteristics of this freewheeling diode will affect the switching losses when the DUT turns on.
This study uses 1200 V commercial devices with Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) structure, specifically the Cree C2M0080120D, Infineon AIMW120R060M1H, and Toshiba TW060N120C, as well as 1200 V commercial devices with SiC Schottky Barrier Diode (SBD) structure, specifically the Infineon IDW30G120C5B and Rohm SCS230KE2HR, for use as the freewheeling diodes investigation including three types of measurements and analysis, (1) the switching characteristics of the switching device, (2) the forward characteristics of the body diodes and SBDs, (3) the reverse recovery characteristics of different commercial devices when they are used as freewheeling diodes.
It was found that using different freewheeling diodes results in different switching losses for the switching device. This is due to the structural differences between body diodes and SBDs, leading to different reverse recovery characteristics and forward voltage. SBDs generally exhibit lower reverse recovery and forward voltage compared to body diodes. Consequently, when current flows through the freewheeling diode, the power loss through the Schottky barrier diode is lower. The lower forward voltage of SBDs also allows current to pass through the built-in Schottky barrier diode of the MOSFET rather than the body diode, resulting in lower power loss when current flows. However, due to the influence of the MOSFET’s output capacitance and the junction capacitance of the built-in Schottky barrier diode, the reverse recovery characteristics at room temperature do not show significant improvement, but the advantages of the Schottky barrier diode become apparent at high temperatures. SBDs exhibit more stable reverse recovery characteristics, which do not deteriorate with increasing temperature. Therefore, using SBDs as freewheeling diodes in half-bridge circuits results in lower turn-on switching losses at high temperatures.
This study also uses Silvaco TCAD simulation software to observe the mechanisms behind the changes in forward voltage and reverse recovery characteristics of body diodes at different temperatures. It was found that increasing temperature lowers the built-in voltage, making the diode easier to turn on, and increases the number of minority carriers, thereby deteriorating the reverse recovery characteristics. | en_US |