Parallel IGBT Gate Coupling for Transient Current Equalization
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Solution Overview
Problem
Power converters face issues with current imbalances among parallel-coupled transistors during transient operating conditions, leading to transistor degradation and reduced output capability due to unequal gate voltages.
Innovation Solution
The electrical switching device employs impedance circuits and resistors to ensure equal gate-to-emitter voltages across multiple IGBTs or MOSFETs, maintaining balanced currents by coupling gate terminals through these circuits and resistors, thereby regulating the voltage signals to maintain equal current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple transistors are parallel coupled to increase output capability, then power conversion capacity is improved, but current imbalance occurs during transient conditions leading to transistor degradation
Solution Approach 1:
The patent implements a feedback mechanism where sense resistors detect the collector currents of each transistor, operational amplifiers compare these currents and generate correction signals, which are then applied through additional resistors to the gate terminals. This closed-loop feedback system automatically balances the currents among parallel transistors during transient conditions, preventing any single transistor from being overloaded and thus improving reliability while maintaining high output capability.
2Speed
If gate voltages are applied directly to parallel transistors, then switching speed is improved, but unequal current distribution occurs among transistors
Solution Approach 1:
The patent introduces intermediary components between the gate voltage source and the transistor gates: sense resistors are placed in the collector circuits to detect current, operational amplifiers act as intermediary controllers to process the current differences, and additional resistors are inserted in series with the gate terminals to provide current correction. These intermediary elements enable precise current balancing without compromising the fast switching performance, as they only subtly adjust the gate voltages rather than fundamentally changing the switching mechanism.
Data Source
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AI summary
An electrical switching device (10) having a plurality of parallel coupled IGBTs (14, 16, 18) is provided. The electrical switching device balances electrical currents in each of the IGBTs that are supplied to a load (64).