Investigating GaN power device double-pulse testing efficacy in the face of VTH-shift, dynamic Rdson, and temperature variations

Double-pulse testing is widely used in the power-electronics industry for rapid evaluation of power devices. These tests aim to allow observation of how a power device under test (DUT) would behave in real-world continuous-mode operation, without having to operate a full converter. It is well known that several device parameters are temperature-dependent, and for full accuracy, in the double-pulse test the temperature of the DUT must be controlled such that it matches the temperature(s) expected in real-world operation. Further and more challenging complications arise if a GaN (Gallium nitride) transistor is being tested, as these suffer from electron/hole trapping between different layers of the device (e.g., p‑GaN, GaN, AlGaN), which can modulate the gate voltage threshold (V
TH
) up or down, and give rise to the phenomenon known as dynamic R
dson
. This paper reviews the factors that give rise to these dynamic effects in the two main families of normally-off p‑gate GaN power transistors: Schottky-gate and ohmic-gate. Experiments performed with a 400 V, 2 kW-rated converter, whose power devices are mounted on a daughter-board so they can be interchanged without affecting the power board, demonstrate the types and levels of discrepancy to be expected between double-pulse testing and continuous-mode operation. Modification of the double-pulse test to an N-pulse test is proposed, and it is shown that this new test method can reproduce the waveforms seen during continuous operation.