Parallel IGBT-WBG MOSFET Switching in Reverse Conduction
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Solution Overview
Problem
Wide bandgap semiconductor switches and silicon-based switches in parallel configurations face challenges in achieving low conduction losses and high switching performance, particularly in diode mode, due to differences in their operational behaviors.
Innovation Solution
A semiconductor module comprising a reverse conducting IGBT and a wide bandgap MOSFET connected in parallel, with a gate controller managing distinct gate signals for each to optimize switching and conduction states, including applying a positive gate signal to the MOSFET after reverse conduction starts and reducing the gate signal before reverse conduction ends to minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same gate signal is applied to both Si based IGBT and wide bandgap MOSFET in parallel configuration, then the control system is simple, but conduction losses increase and switching performance deteriorates in diode mode
Solution Approach 1:
The gate control system is segmented into separate control paths for the IGBT and wide bandgap MOSFET. The controller generates different gate signals for each device, allowing independent optimization of their operational characteristics, particularly in diode mode where the wide bandgap device benefits from positive gate voltage while the IGBT uses conventional control
Solution Approach 2:
Different gate signal characteristics are applied to different devices based on their specific requirements. The wide bandgap MOSFET receives a gate signal with positive voltage during diode conduction to reduce conduction losses, while the IGBT receives conventional gate control, optimizing each device's performance locally rather than using a uniform control approach
2Loss of energy
If different gate signals are applied to wide bandgap MOSFET and Si based IGBT, then conduction losses are reduced and switching performance is enhanced, but the gate control system becomes more complex
Solution Approach 1:
The gate control system incorporates feedback mechanisms where the controller monitors the operational state of the parallel-connected IGBT and wide bandgap MOSFET, particularly detecting diode mode conduction, and dynamically adjusts the gate signals accordingly. This feedback enables the system to automatically apply positive gate voltage to the wide bandgap device during diode conduction without requiring complex manual intervention
Solution Approach 2:
The controller is configured to apply positive gate voltage to the wide bandgap MOSFET in advance of diode mode conduction or at the onset of diode conduction, preparing the device for optimal performance before the full diode mode is established, thereby reducing conduction losses from the beginning of the reverse current flow
3Reliability
If wide bandgap MOSFET is used in parallel with IGBT, then switching performance and thermal performance are improved, but device control complexity increases due to different operational behaviors
Solution Approach 1:
The gate voltage parameter for the wide bandgap MOSFET is changed from conventional zero or negative voltage during diode conduction to positive voltage, fundamentally altering the operational characteristics of the device in diode mode and enabling reduced conduction losses and improved switching performance
Data Source
AI summary
A semiconductor module comprises reverse conducting IGBT connected in parallel with a wide bandgap MOSFET, wherein each of the reverse conducting IGBT and the wide bandgap MOSFET comprises an internal anti-parallel diode. A method for operating a semiconductor module with the method including the steps of: determining a reverse conduction start time, in which the semiconductor module starts to conduct a current in a reverse direction, which reverse direction is a conducting direction of the internal anti-parallel diodes; applying a positive gate signal to the wide bandgap MOSFET after the reverse conduction start time; determining a reverse conduction end time based on the reverse conduction start time, in which the semiconductor module ends to conduct a current in the reverse direction; and applying a reduced gate signal to the wide bandgap MOSFET a blanking time interval before the reverse conduction end time, the reduced gate signal being adapted for switching the wide bandgap MOSFET into a blocking state.