Contents I. Introduction
The parallel connected insulated gate bipolar transistors (IGBTs) typology has become a common and effective way in extending the power rating of an IGBT-based power converter. However, the current difference among IGBT branches is a main and critical problem because it induces device reliability issues, such as device fail earlier than its baseline lifecycle. The root cause of current imbalance is device fabrication and assembly processes induced physical difference as well as power circuit parasitic parameters induced a difference in application. For instance, most of the spec limit and control limit of fabrication or assembly processes have a range, so even the devices in the same manufacturing lot, they have minor differences which are strong enough to cause current differences. The similar situation can be found in IGBT-based application circuits, such as the variance of parasitic parameters caused by the layout and so forth. Many literature give deep investigations of the factors that impact the current balance of parallel connected IGBTs, such as [1]–[7]. In brief, the unpreventable process errors in manufacturing and application cause the current imbalance of parallel connected IGBTs.
