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|Integrated Protection Circuits for an NMOS Silicon Carbide Gate Driver IC|
|Keywords: Silicon Carbide, Integrated Circuits, Gate Driver|
|Recent work has been done to build a Silicon Carbide (SiC) gate driver IC for use with a 1,200V SiC power DMOS. Using integrated lateral SiC technology for the gate driver provides the opportunity for either direct integration on the power device die or inside the package. Protection circuits form an important part of the complete gate driver/power device system. Under-voltage lockout (UVLO) protection disables the gate driver when power supplies are insufficient to turn the power device fully on. Desaturation detection provides protection to the power device by recognizing over-current conditions and disabling the gate driver for a set duration. The protection circuits described in this paper are integrated with a novel gate-driver architecture utilizing discrete 20 V and 40 V power supplies. Two separate UVLO circuits monitor these power supplies while being powered by the 20 V supply. Previous results described a single 20 V-monitoring UVLO powered by an additional regulated 12 V supply. New developments have eliminated the need for the additional 12V regulated supply and allow monitoring of all gate driver power supplies across an operational temperature range of 25-275℃, all without the need of any external components. The desaturation detection circuit ensures that the power device is in its safe operating area. It does this by monitoring the power device drain voltage during conduction through an external high-voltage diode and voltage-divider network. Drain voltages that exceed a specific threshold trigger the fault output for a fixed duration. The desaturation detection circuit is designed to work with a 20A SiC MOSFET in less than 500ns, while avoiding false triggering on leading-edge spikes. The outputs of the three protection circuits are combined to obtain a single fault signal. This signal can be used as a gate driver input to protect the power device and the overall system. Bench test results of the two UVLOs and desaturation detection circuits were captured and are compared to simulated results.|
|Paul D Shepherd, PhD Candidate
University of Arkansas