On-State Voltage Measurement of High-Side Power Transistors in Three-Phase Four-Leg Inverter for In-Situ Prognostics

This paper presents the challenges of implementing in-situ prognostics to practical power converters and proposes a new on-state voltage (V
DSON
) monitoring circuit for the high-side power transistors. The proposed approach references the drain of the high-side transistors for their V
DSON
measurement. This circuit allows V
DSON
measurement of not only multiple high-side transistors but also multiple low-side transistors at the same time. The measured V
DSON
is used to calculate on-state resistance (R
DSON
) in real-time using the drain-current measured using an off-the-shelf hall effect current sensor. The proposed circuit is used in a 75 kW 1000 V
DC
three-phase DC-AC inverter for in-situ prognostics. Validations of the proposed V
DSON
measurement circuit and R
DSON
monitoring are presented using theoretical circuit analysis and experimental results. The measured R
DSON
is found to be in the datasheet specified range.