Effects of Auxiliary-Source Connections in Multichip Power Module

Auxiliary-source bond wires and connections are widely used in power modules with paralleled mosfets or insulated gate bipolar transistor (IGBTs). This paper investigates the operation mechanism of the auxiliary-source connections in multichip power modules. It reveals that the auxiliary-source connections cannot fully decouple the power loop and the gate loop such as the Kelvin-source connection, owing to their involvement in the loop of the power source current. Three effects of the auxiliary-source connections are then analyzed, which are 1) the common source stray inductance reduction, 2) the transient drain-source current imbalance mitigation, and 3) the influence on the steady-state current distribution. Finally, simulations and experimental results validate the theoretical analysis.

I. Introduction

Multichip power modules with paralleled power semiconductor devices are widely used with today's power electronics applications, such as the renewable power systems [1]– [3], variable speed drives [4], and electrification of transport [5], [6]. With the new generation of power semiconductor devices switching faster, e.g., wide band gap (WBG) devices, the effects of the parasitic circuit parameters in the power module tend to be more apparent [7]–[10]. One challenge is that the common source stray inductance limits the switching speed and causes more switching losses [11]. Common source stray inductance is the stray inductance in both the gate–source current loop and the drain–source current loop. To avoid the common source stray inductance, auxiliary-source connections are usually used in fast switching multichip power modules [7], [12].