IGBT MOSFET Gate Control Segmentation for Switching Loss Reduction
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Solution Overview
Problem
Existing power semiconductor devices using IGBTs and MOSFETs in parallel face challenges in downsizing due to high switching losses and current rating requirements, making it difficult to reduce the overall device size.
Innovation Solution
The implementation of a modularized power semiconductor device configuration where IGBTs and MOSFETs are arranged in series with complementary control circuits, allowing for differential threshold voltage settings and resistive elements with diodes to manage gate control signals, enabling efficient switching operations that suppress current flow in MOSFETs during transient states, thus eliminating the need for high current ratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the IGBT and MOSFET are connected in parallel with commonly connected gates and driven by a common gate drive circuit, then switching loss is reduced, but the current rating of the MOSFET has to be increased which makes it difficult to reduce the chip size
Solution Approach 1:
The patent divides the gate control into separate segments by providing independent gate drive circuits for the IGBT and MOSFET. The gate control signal generation is segmented into multiple paths: one path controls the IGBT gate directly, while another path controls the MOSFET gate through a resistive element. This segmentation allows independent optimization of each transistor's gate control, enabling the MOSFET to operate with lower current rating while maintaining reduced switching loss benefits.
Solution Approach 2:
The patent applies local quality by introducing different control characteristics to different parts of the parallel circuit. Specifically, the MOSFET gate control includes a resistive element with specific resistance value (1kΩ to 10kΩ) that is not present in the IGBT gate control path. This creates locally differentiated control quality that allows the MOSFET to have reduced current rating while still contributing to switching loss reduction through its specific gate control characteristics.
2Reliability
If the ON threshold voltage of the IGBT is set higher than the ON threshold voltage of the MOSFET, then turn-off characteristics are improved, but total current flows in the MOSFET without fail in transient state which requires increased current rating
Solution Approach 1:
The patent changes the control parameter characteristics by introducing a resistive element in the MOSFET gate control path. This resistive element modifies the gate voltage waveform and its rate of change, allowing the MOSFET to achieve proper turn-off characteristics without requiring high current rating. The resistance value (1kΩ to 10kΩ) is specifically chosen to optimize the gate charging/discharging characteristics, enabling reliable operation with reduced current capacity.
Data Source
AI summary
Among first IGBTs and first MOSFETs, a transistor arranged near a first gate control circuit gives, through a gate thereof, a gate control signal supplied from the first gate control circuit to a gate of a transistor arranged at a position farther from the first gate control circuit. Among second IGBTs and second MOSFETs, a transistor arranged near a second gate control circuit gives, through a gate thereof, a gate control signal supplied from the second gate control circuit to a gate of a transistor arranged at a position farther from the second gate control circuit.