## 4 The Efficiency of Hybrid Power Stage under Light-Load Conditions
### 125 kW Si IGBT Converter vs. 10 kW SiC Power Stage under Light-Load Conditions
#### 4.1.1 Conduction Losses of IGBT- and SiC-Based Light-Load Setup
\begin{table}
\begin{tabular}{l c} \hline \hline
**Parameter** & **Value** \\ \hline MOSFET on resistance: & \(R_{\text{on,MOS}}=35\) m\(\Omega\) \\ IGBT forward voltage (light-load): & \(V_{\text{T}}=0.7\) V \\ IGBT on resistance (light-load): & \(R_{\text{on,IGBT}}=4.2\) m\(\Omega\) \\ IGBT anti-p. diode forward voltage (light-load): & \(V_{\text{D}}=0.85\) V \\ IGBT anti-p. diode on resistance (light-load): & \(R_{\text{on,IGBT}}=3.5\) m\(\Omega\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Relevant IGBT, dedicated antiparallel diode and SiC MOSFET parameters. frequency of the Si-IGBT modules. An increased switching frequency would reduce the maximum current ripple and thus rms value of semiconductor devices, which results in lower conduction losses (quadratic nature). A higher chip area, on the other hand, will diminish the on-resistance of each MOSFET and therefore reduce conduction losses (linear dependency). Ideally, the SiC-MOSFETs would be mounted on the same heatsink as the Si-IGBT modules. As this heatsink is designed to process much higher losses of Si-IGBTs and diodes during nominal operation, an extremely low thermal resistance of the external cooling setup can be expected. Therefore, the equipped circuit shows some room of flexibility and comes with an additional degree of freedom \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \(\mathbf{\upphi}\) & \(S_{\text{in}}\) & \(I_{\text{IGET,avg}}\) & \(I_{\text{IGET,rms}}\) & \(I_{\text{D,avg}}\) & \(I_{\text{D,rms}}\) & \(I_{\text{MOS,rms}}\) & \(P_{\text{IGET,avg}}\) & \(P_{\text{IGET,rms}}\) & \(P_{\text{D,avg}}\) & \(P_{\text{D,rms}}\) & \(P_{\text{MOS}}\) \\ (\({}^{\circ}\)) & (**0**VA) & (**A**) & (**A**) & (**A**) & (**A**) & (**A**) & (**W**) & (**W**) & (**W**) & (**W**) & (**W**) \\ \hline
0 & 0 & 3.35 & 8.19 & 3.35 & 8.19 & 11.6 & 2.34 & 0.28 & 2.84 & 0.23 & 4.69 \\
0 & 5000 & 2.54 & 7.63 & 4.62 & 10.11 & 12.7 & 1.78 & 0.24 & 3.93 & 0.36 & 5.61 \\
0 & 10,000 & 2.19 & 8.36 & 6.36 & 13.01 & 15.5 & 1.53 & 0.29 & 5.4 & 0.59 & 8.37 \\
180 & 0 & 3.35 & 8.19 & 3.35 & 8.19 & 11.6 & 2.34 & 0.28 & 2.84 & 0.23 & 4.69 \\
180 & 5000 & 4.62 & 10.11 & 2.54 & 7.63 & 12.7 & 3.23 & 0.43 & 2.16 & 0.20 & 5.61 \\
180 & 10,000 & 6.36 & 13.01 & 2.19 & 8.36 & 15.5 & 4.45 & 0.71 & 1.86 & 0.24 & 8.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Documented current stress and losses of IGBT with antiparallel diode and SiC–MOSFET for different phase angles and load conditions. Figure 10: Conduction loss comparison of SiC MOSFET and Si–IGBT with an antiparallel diode for various load situations from 0 to 10 kVA and different phase angles of (**a**) \(\varPhi=0^{\circ}\) which results in \(\cos(\varPhi)=1\), (**b**) \(\varPhi=45^{\circ}\), (**c**) \(\varPhi=90^{\circ}\) and (**d**) \(\varPhi=180^{\circ}\). in terms of operation of the SiC-MOSFET devices (e.g., higher switching frequency to improve the effectiveness of input/output filter (improved THDi) under light-load condition.