Switching Substrate With Interlocking Bus Bars
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Solution Overview
Problem
The complexity of shutting down current flow in both directions using MOSFET switches is challenging due to parasitic diodes, leading to complications in switching board design, and existing solutions are cumbersome.
Innovation Solution
A switching board configuration with bus bars and semiconductor switching elements arranged in a simple layout, where two MOSFETs are connected in series with opposite parasitic diode orientations, and bus bars are designed with projecting and recessed portions to prevent breakage under force, allowing for a straightforward installation between main and auxiliary power supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two MOSFETs are connected in series with opposite parasitic diode orientations to shut down current in both directions, then current blocking capability is improved, but circuit complexity increases
Solution Approach 1:
A body-biased NMOS transistor is introduced as an intermediary element between the two series-connected MOSFETs. The body of the intermediate MOSFET is connected to the junction between the two MOSFETs, creating a controlled path that allows the parasitic diodes to be forward-biased only when necessary for current blocking, while maintaining simple series connection topology for normal operation.
Solution Approach 2:
The body bias voltage of the intermediate MOSFET is dynamically changed based on the operating state. When current blocking is required in reverse direction, the body bias is adjusted to forward-bias the parasitic diode of the intermediate MOSFET, enabling controlled current flow through the body region rather than through the drain-source path, thus achieving bidirectional current blocking with simple series connection.
2Strength
If bus bars are designed with projecting and recessed portions to prevent breakage under force, then structural durability is improved, but manufacturing complexity increases
Solution Approach 1:
The bus bar structure is segmented into multiple regions with projecting portions and recessed portions along its length. These segments are designed to interlock with corresponding features on the control circuit board, distributing mechanical stress across multiple contact points rather than concentrating force at single attachment points, thereby preventing breakage while using simple extrusion or stamping processes.
Solution Approach 2:
The bus bar features asymmetric projecting and recessed portions that are strategically positioned to match the asymmetric mounting holes and attachment features on the control circuit board. This asymmetric design creates a natural mechanical interlock that resists pull-out forces and bending stresses, enhancing structural durability without requiring complex multi-step manufacturing processes.
Data Source
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AI summary
A switching board (10) includes: a control circuit board (20) that has, in a first surface thereof, a control circuit (22B), a connection circuit (22A), a first mounting window (24A), and a second mounting window (24B); a circuit structure (11) including an input bus bar (30) and an output bus bar (40) that are arranged in a second surface of the control circuit board (20); and a first semiconductor switching element (60A) and a second semiconductor switching element (60B). The first semiconductor switching element (60A) is arranged inside the first mounting window (24A). The drain terminal (62), the source terminal (63), and the gate terminal (64) of the first semiconductor switching element (60A) are connected respectively to the input bus bar (30), the connection circuit (22A), and the control circuit (22B). The second semiconductor switching element (60B) is arranged inside the second mounting window (24B). The drain terminal (62), the source terminal (63), and the gate terminal (64) of the second semiconductor switching element (60B) are connected respectively to the output bus bar (40), the connection circuit (22A), and the control circuit (22B).