How the heck do I Measure a Gate Drive Slewing at 70 kV/Us?

Abstract:
Power Electronic converter efficiency and reliability is determined by a complex tradeoff between gate drive design, switch losses, EMI generation, switch Safe Operating Area and managing parasitic effects. But gate drives can slew common mode at up to 70KV/us, and tools to measure voltage waveforms, power loss, impedance, and stability while exposed to this common mode slew are thin on the ground. We present a new channel isolated oscilloscope which can measure voltage waveforms, the power loss in a switch device, the wideband impedance of a gate drive power supply, and the charge delivered to a gate all while the gate drive is slewing 700V in 10ns. Using phase coherent channels, and an isolated tracking signal generator for stimulus, the oscilloscope can generate a Bode plot of the closed loop gate drive response, and determine stability. The oscilloscope can be applied to measure gate driver performance, switch losses, EMI generation and Safe Operating Area during switch operation in a manner not previously possible, and use the results to formalize the system tradeoffs to achieve highest efficiency and reliability. Some say that without measurement there is no hope. All we know is that this oscilloscope was born for power electronics measurement.