Combined IGBT and Superjunction MOSFET for Low Conduction Losses
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Solution Overview
Problem
IGBTs face challenges with high conduction losses at low current due to voltage threshold issues and lack of reverse current conduction, requiring additional components like freewheeling diodes, while combination IGBT and Super-Junction MOSFET devices experience overcurrent problems during high current operations.
Innovation Solution
Structurally coupling an IGBT with a Super-Junction MOSFET on the same substrate, sharing contact layers and gate resistances to enable simultaneous operation, with the Super-Junction MOSFET acting as a freewheeling diode and modifying the device structure to prevent overcurrent by ensuring the IGBT switches before the MOSFET during high current operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a diode is placed anti-parallel to the IGBT to enable reverse current conduction, then reverse current conduction is achieved, but conduction losses at low current are not reduced
Solution Approach 1:
The patent combines an IGBT and a Super-Junction MOSFET into a single integrated device structure. The MOSFET portion provides low conduction losses at low currents while the IGBT handles high current operations. Both devices share common substrate, contact layers, and gate structure, enabling them to work together as a unified power switch that resolves the contradiction between reverse current capability and low-current efficiency.
Solution Approach 2:
The combined device serves multiple functions within a single structure: the IGBT provides high current handling capability and voltage threshold protection, while the Super-Junction MOSFET provides low conduction losses at low currents and body diode for reverse current conduction. This multi-functional integration eliminates the need for separate freewheeling diodes and achieves both reverse current capability and low conduction losses simultaneously.
2Power
If an IGBT is used for high current applications, then high current conductance is achieved, but conduction losses increase at low current due to voltage threshold
Solution Approach 1:
The power switching function is segmented between two device types within the same package: the IGBT segment handles high current operations where its superior conductance is beneficial, while the Super-Junction MOSFET segment handles low current operations where its lower conduction losses are advantageous. This segmentation allows each device type to operate in its optimal current range, resolving the contradiction between high current capability and low current efficiency.
Solution Approach 2:
The patent changes the operational parameters by introducing a second device with different electrical characteristics (Super-Junction MOSFET with lower on-resistance and no voltage threshold) to complement the IGBT. The MOSFET's body diode also provides reverse current conduction capability, changing the overall device parameters to achieve both high current handling and low conduction losses across the full operating range.
3Power
If IGBT and Super-Junction MOSFET are coupled to switch simultaneously, then both devices share current handling, but overcurrent conditions occur during high current operations
Solution Approach 1:
The patent implements preliminary action by configuring the gate drive circuitry and device structure so that the IGBT switches on before the Super-Junction MOSFET during high current operations. The IGBT's voltage threshold characteristic causes it to begin conducting first, establishing a current path that prevents excessive current from flowing through the MOSFET. This sequential switching action, built into the device operation, prevents overcurrent conditions while maintaining both devices' current handling capabilities.
Data Source
AI summary
An apparatus comprising an insulated gate bipolar transistor; and a super-junction metal-oxide semiconductor field effect transistor wherein the insulated gate bipolar transistor wherein the super-junction metal-oxide semiconductor field effect transistor are structurally coupled and wherein the super-junction metal-oxide semiconductor field effect transistor is configured to switch to an ‘on’ state from an ‘off’ state and an ‘off’ state from an ‘on’ state.