Event-Driven Commutation for Reverse-Conducting IGBTs
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Solution Overview
Problem
Existing methods for commutation between reverse conducting IGBTs operated in diode mode and IGBT mode are sensitive to propagation time tolerances, requiring precise timing and effort due to potential isolation in signal paths, leading to inefficiencies in switching and loss management.
Innovation Solution
The method switches the gate of the reverse conducting IGBT operated in diode mode event-controllly, using inductive voltage drops or current transformers to detect the start of current flow in the IGBT mode, allowing for precise determination of commutation initiation without the need for high temporal precision, thus reducing sensitivity to propagation times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-controlled commutation method is used with predetermined delay times, then commutation timing can be predetermined, but the system becomes highly sensitive to propagation time tolerances and requires great effort for matching delay times
Solution Approach 1:
The patent replaces the mechanical/time-based delay circuit system with an event-based detection system using voltage drop sensing. Instead of relying on predetermined delay times and propagation time matching, the system detects the actual commutation event through voltage monitoring across an inductance, substituting temporal precision requirements with event-based triggering that is inherently more robust to timing variations.
Solution Approach 2:
The system uses the inherent voltage drop across the commutation inductance as a self-generated signal to trigger the gate voltage reduction. The commutation process itself generates the detection signal, eliminating the need for external timing references or complex synchronization circuits, thereby reducing control complexity while maintaining precision.
2Loss of energy
If gate voltage is reduced below threshold voltage before reverse current peak, then reverse recovery losses are reduced, but the timing window becomes very narrow and sensitive to propagation delays
Solution Approach 1:
The system implements feedback by continuously monitoring the voltage drop across the commutation inductance and using this information to trigger gate voltage reduction at the optimal moment. The detection circuit provides real-time feedback about the commutation state, enabling precise control of the gate voltage timing window without requiring predetermined knowledge of propagation delays or current peak timing.
Solution Approach 2:
The system performs preliminary detection of the commutation event through voltage monitoring before the reverse current peak occurs. By detecting the voltage drop early in the commutation process, the system can proactively reduce the gate voltage at the optimal moment, preparing the device for efficient commutation before the critical current peak is reached, thereby reducing losses without requiring extremely precise timing.
3Reliability
If potential isolation is used in signal paths from control device to driver circuits, then electrical isolation is achieved, but propagation time tolerances increase significantly
Solution Approach 1:
The patent introduces an intermediary detection circuit that monitors the voltage drop across the commutation inductance. This intermediary system acts as a mediator between the control device and the driver circuits, providing a local event-based trigger signal that eliminates the need for precise timing over isolated signal paths. The detection circuit translates the physical commutation event into a control signal, bridging the isolation gap without propagating timing uncertainties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient commutation with reduced sensitivity to propagation time tolerances, allowing for effective anode efficiency reduction and minimized turn-on losses, improving the overall performance and ease of control in power converter phases.
Implementation Method 1
The rate of current rise in the commutation circuit is greater by at least one power of ten than in an associated load circuit. As a result, the beginning of the commutation can be clearly determined at the inductive voltage drop without great effort.
Implementation Method 2
A further possibility for detecting the point in time of the current flow in the RC-IGBT operated in IGBT mode consists in measuring the collector current of the RC-IGBT operated in diode mode.
Data Source
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AI summary
The invention relates to a method for commuting from a reverse-conducting IGBT (T1) operated in the diode mode to a reverse-conducting IGBT (T2) operated in the IGBT mode. The reverse-conducting IGBT (T1) operated in the diode mode is switched off only when a current starts to flow in the reverse-conducting IGBT (T2) operated in the IGBT mode. As a result, the commutation method is event-driven, thereby rendering it less sensitive to misapplied operating times.