Test Setup for Dynamic ON-State Resistance Measurement of High- and Low-Voltage GaN-HEMTs Under Hard and Soft Switching Operations

GaN-HEMTs impress with excellent properties, and therefore power electronics engineers pay a lot of attention to them. However, during switching operation some devices show increased ON-state resistance. Since, for switch mode power supply designers, the internal device structure is not apparent, measuring the ON-state resistance under the targeted operating conditions is the only method to gain this information. In order to characterize the dynamic ON-state resistance, this article proposes a clamping circuit for accurate measurement. Using a high-resolution digitizer card ensures precise results. The presented measurement setup allows to measure the ON-state resistance under hard and soft switching conditions with parameters of the intended application. In inverter applications, each switch works under hard as well as soft switching. Therefore, the transition between these two operating modes must also be studied in detail. Finally, an extension of the clamping circuit is presented allowing measurements with high-voltage GaN-HEMTs as well. The initial results verify the improved setup.