The Superiority of the IGBT over the MOSFET

The IGBT has the advantage over the MOSFET at higher switching frequencies. But at lower switching frequencies, the MOSFET has the lowest overall loss and the lowest operating junction temperature. (The selected IGBT and MOSFETs have approximately the same matrix sizes and thermal impedances.) This is somewhat contrary to conventional wisdom where it is often argued that MOSFETs perform better at higher switching frequencies. However, these results indicate otherwise and can be attributed mainly due to the significantly lower diode recovery loss component of the IGBT + FRD (fast recovery diode) and the significant improvement in minimizing the tail current behavior of the IGBT.

The lower switching loss of the IGBT + FRD due to a significantly lower diode recovery loss component gives it the advantage over the MOSFET at 20 kHz (a relatively high switching frequency for this application). In addition, the loss of switching of the MOSFET can be significantly reduced by the use of a gate controller with a greater supply capacity and sinking current (for example, a 2-A power supply controller / sinking current). As a result, the total losses of MOSFET would be reduced and would allow the MOSFET to close the gap between it and the IGBT. The resulting higher DV / dt, however, could cause undesirable effects such as high-frequency sounds and a higher level of irradiated EMI. Curiously, At lower switching frequencies where conduction loss dominates, the MOSFET benefits due to the absence of a "knee" in its forward characteristics, along with a relatively low RDS (on). While the IGBT remains the best device to select in this application example, the availability of significantly lower RDS (on) MOSFET along with better diode recovery behavior and a strong gate driver could start tilting the balance towards the MOSFET In that case, it would then reach a cost/performance ratio ("$ / Amp") with the IGBT probably having the edge due to a much higher current density (for a given die size).

Similar IGBTs and MOSFETs are often available for a given application. It is useful to clearly understand the advantages and limitations of both devices and choose the one that best suits the requirements in terms of overall performance and cost. While this is not an easy effort, greater familiarity with these energy devices will be beneficial in navigating these complex decisions.