An online on-state voltage measurement circuit with dual-diode power balancing for IGBT

The collector-emitter on-state voltage drop (Vce-on) of Insulated Gate Bipolar Transistor (IGBT) serves as a critical parameter for characterizing operational status and enabling junction temperature measurement. Consequently, achieving high-precision online measurement of Vce is of significant importance. However, existing Vce-on measurement circuits based on high-voltage diodes have significant error due to the power imbalance between diodes. To address this challenge, this paper proposes a fast and accurate online measurement circuit for Vce-on based on dual-diode power balancing. By incorporating a control MOSFET, the circuit achieves power equilibrium between dual diodes. Moreover, the frequency-domain characteristics of the measurement circuit are systematically analyzed and the potential factors affecting measurement precision are evaluated. Theoretical analysis results demonstrate that the circuit exhibits high measurement accuracy and rapid response characteristics. Furthermore, experimental verification under both fixed voltage and square wave input conditions confirms that the circuit achieves rapid response speed with static measurement errors below 6mV across various load conditions. The proposed circuit proves suitable for online monitoring of Vce-on and facilitates effective junction temperature monitoring of IGBT.