Measuring Transient I/V Turn-On Behavior of a Power MOSFET without a Current Sensor

Abstract

Double pulse test (DPT) is usually used to characterize and verify turn-on/turn-off operation of power switches. Yet, new high frequency switching devices based on SiC and GaN technologies require much more elaborate DPT circuitry and sensing nodes compared to the established Si devices. Especially, suitable current sensors are challenging to realize and always limit the bandwidth. We propose a Transmission Line Pulsing (TLP)-based technique, which we call sensor gap TLP (sgTLP) and which is capable to monitor the transient currents and voltages during the turn-on sequence of a power MOSFET, without the need of a current sensor. The proposed sgTLP approach is compared to established TLP methods in two applications: the passive switching of a fast transient voltage suppression diode and the active switching of a Si power MOSFET. The novel sgTLP shows the same or better characteristics than both of the standard methods, but needs only one measurement, where standard TLP would need two separate methods. Especially, sgTLP detected rise times of 54 ps of a current and 52 ps of a voltage signal using a pulse duration of 100 ns. The measured characteristics of the MOSFET turnon reveals several inductive and capacitive coupling mechanisms that are not analyzable by the established TLP methods but become visible applying sgTLP.