High-resolution power electronics measurements

Abstract

In described examples of a measurement circuit to measure a drain voltage of a drain terminal (106) of the high voltage transistor (M0) during switching, the measurement circuit includes an attenuatorcircuit (102) to generate an attenuator output signal (VDCLAMP) representing a voltage across the high voltage transistor (M0) when the high voltage transistor (M0) is turned on, and a differential amplifier (124) to provide an amplified sense voltage signal (VO) according to the attenuator output signal (VDCLAMP). The attenuator circuit (102) includes a clamp transistor (M1) coupled with the drain terminal (106) of the high voltage transistor (M0) to provide a sense signal (VSENSE) to a first internal node (110), a resistive voltage divider circuit (116) to provide the attenuator output signal (VDCLAMP) based on the sense signal (VSENSE), and a first clamp circuit (Z1) to limit the sense signal voltage (VSENSE) when the high voltage transistor (M0) is turned off.

Description

technical field [0001] The present invention relates generally to measuring transistor operating characteristics, and more particularly to systems and circuits for measuring the voltage across a high voltage transistor during switching to determine on-state impedance during switching. Background technique [0002] Gallium Nitride (GaN) and Aluminum Gallium Nitride (AlGaN) High Electron Mobility Transistors (HEMTs), Silicon Carbide (SiC) and other high voltage transistors are used in become popular in high voltage power conversion applications. Under certain dynamic conditions, electron trapping in AlGaN / GaN HEMTs leads to current collapse and increased drain-source on-state resistance (RDSON). However, measuring the dynamic RDSON performance of HEMTs is difficult. Measurements made by semiconductor test instruments cannot simulate real device states in real power electronics circuits. For example, switching transistors in typical power converters undergo hard-switching tr...

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Problems solved by technology

Therefore, direct measurements with common oscilloscope voltage probes may saturate the oscilloscope channel when the high voltage transistor is off

In addition, traditional high-voltage oscilloscope probes cannot accurately measure the measured drain-source transistor voltage due to their high division (voltage) ratio (typically 100x) resulting in signals that are too small for the oscilloscope to resolve when the transistor is on

Traditional voltage clamping circuits can be used to limit the maximum voltage seen by the oscilloscope, but these circuits introduce large RC time constants and therefore do not provide a sufficiently short settling time to accurately evaluate the dynamic drain-source voltage characteristics and thus the Dynamic RDSON of High Voltage AlGaN / GaN and SiC Transistors under Real Conditions

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