Large scale test bed for in-circuit reliability testing of silicon carbide diodes and MOSFETs emulating real life voltage and current stress

This paper introduces an In-Circuit Reliability Test System (ICRTS) for SiC MOSFETs and diodes that can test a large number of high-voltage devices by emulating real life voltage and current stress to get statistical endurance test results. One challenge of testing a large number of devices under real life stress is the unrealistic amount of power consumption. To overcome this challenge, the ICRTS system uses the proposed pump-back converter topology. With this approach, the ICRTS system can stress the devices to their rated voltage and current conditions during each switching event and continuously switch the devices with appropriate switching frequency for an extended time while dramatically reducing the total power consumption to just the system loss. This system's concept was based on a single test unit board to verify its capability of energy cycling and device stressing while minimizing the power consumption. Another unique feature is the system running in open loop mode that enables real time feedback of any shift in the active device parameters. Simulation and experimental test results are provided to verify the operation of the proposed pump-back converter and its capability of operating in open loop mode and accommodate normal device and system variations when this is scaled to large number of parallel systems. To enable long term and safe operation of the test system, various voltage, current and temperature sensors and integrated in the test board that monitor the health in real time and shuts it off when any of the parameters cross a pre-determined threshold. A system level design is presented that can enable these individual converters to be operated in parallel. These features allow for independent test unit board shutdown, replacement, and failure analysis.