Bidirectional Switching Assembly With Cascode MOSFET-HV Switch Layout
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Solution Overview
Problem
Conventional bidirectional switching units for power systems in aircraft and vehicles suffer from high voltage drop, high power loss, and large footprint requirements, limiting their efficiency and applicability in power converters and battery chargers.
Innovation Solution
A bidirectional switching assembly comprising a first and second low-voltage MOSFET and a normally ON high-voltage semiconductor switch, such as a JFET or HEMT, arranged in series with the high-voltage semiconductor switch sandwiched between the MOSFETs, where the switching units are controlled by the MOSFETs, which are connected through high-voltage diodes with an input and output side of the switching assembly, thereby blocking the MOSFETs, and the switching units are controlled by the switching assembly, which are controlled by the MOSFETs, which are connected through the high-voltage diodes with an input and output side of the switching assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional bidirectional switching units use two MOSFET or IGBT devices in common source/collector or common drain/emitter configuration, then bidirectional conducting and blocking capability is achieved, but voltage drop increases, power loss increases, and footprint area increases
Solution Approach 1:
The bidirectional switching unit is segmented into two separate unidirectional switching paths: a first switching path for forward current using a first MOSFET, and a second switching path for reverse current using a second MOSFET. Each MOSFET operates optimally in its designated direction, reducing overall voltage drop and power loss while maintaining bidirectional capability.
2Adaptability or versatility
If conventional bidirectional switching units use two MOSFET or IGBT devices in common source/collector or common drain/emitter configuration, then bidirectional conducting and blocking capability is achieved, but device area increases
Solution Approach 1:
The switching unit is divided into two independent unidirectional paths, each handled by a single MOSFET. This segmentation allows for more efficient space utilization compared to using two MOSFETs/IGBTs in a common configuration, reducing the overall footprint area required for the bidirectional switching unit.
3Adaptability or versatility
If conventional bidirectional switching units use two MOSFET or IGBT devices in common source/collector or common drain/emitter configuration, then bidirectional conducting and blocking capability is achieved, but voltage drop increases
Solution Approach 1:
The bidirectional switching function is segmented into two separate unidirectional paths, each optimized for its specific direction. The first MOSFET handles forward current with optimal voltage characteristics, while the second MOSFET handles reverse current, thereby reducing the overall voltage drop compared to conventional common configuration approaches.
Solution Approach 2:
Each switching path is locally optimized for its specific current direction. The first MOSFET is optimized for forward conduction, and the second MOSFET is optimized for reverse conduction, allowing each component to operate in its most efficient mode and minimizing voltage drop in both directions.
Data Source
Figure 1~1A
Figure 2A~2B
Figure 2C~2D
AI summary
The invention regards a bidirectional switching assembly (100) which comprises: a first switching unit (S1) which comprises a first low voltage MOSFET (T1), wherein the first low voltage MOSFET (T1) comprises a first gate (G1), a second switching unit (S2) which comprises a second low voltage MOSFET (T2), wherein the second low voltage MOSFET (T2) comprises a second gate (G2), and a third switching unit (S3) which comprises a normally ON high voltage semiconductor switch (T3, T31, T32), wherein the normally ON high voltage semiconductor switch (T3, T31, T32) comprises a third gate (G3, G31, G32) and wherein the third gate (G3, G31, G32) is connected through high-voltage diodes (D1, D2) with an input side (IN) and with an output side (OUT) of the switching assembly (100). The first switching unit (S1), the third switching unit (S3) and the second switching unit (S2) are arranged in series, with the third switching unit (S3) sandwiched between the first switching unit (S1) and the second switching unit (S2), wherein in one direction the third switching unit (S3) and the second switching unit (S2) form a cascode and in the other direction the third switching unit (S3) and the first switching unit (S1) form a cascode. The switching assembly (100) is configured to conduct a current in either direction when the third switching unit (S3) is switched on and configured to block a current in either direction when the third switching unit (S3) is switched off, wherein the third switching unit (S3) is switched on and off by switching on and off at least one of the first and second switching units (S1, S2).