Normally Off Power Component Cascode Configuration
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Solution Overview
Problem
High-voltage transistors used in switching circuits are normally on, leading to risky conditions due to potential current passage without a quenching voltage, and existing solutions are complex with numerous wire connections and parasitic inductances.
Innovation Solution
A normally off discrete power component is designed with a high-voltage normally on transistor and a low-voltage normally off transistor in cascode configuration, where the normally off transistor has its source terminal on the back of the chip, directly connected to a conductive plate, reducing the need for insulation and wire connections, and incorporating a control circuit to slow down switching transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a normally on high-voltage transistor is used, then high voltage switching capability is achieved, but current passage without control becomes possible creating safety risks
Solution Approach 1:
The power transistor is segmented into two separate transistors: a normally on high-voltage transistor for power switching and a normally off low-voltage transistor for safety control. This segmentation allows each transistor to specialize in its function while the normally off transistor prevents uncontrolled current passage by blocking the gate control path when not activated.
Solution Approach 2:
A normally off low-voltage transistor is introduced as an intermediary control element between the control terminal and the normally on high-voltage transistor. This intermediary prevents direct uncontrolled current passage by requiring active gating to enable the high-voltage transistor, thus adding a safety layer without compromising the high voltage switching capability.
2Reliability
If separate chips with wire connections are used for normally on and normally off transistors, then functional requirements are met, but device complexity and parasitic inductances increase
Solution Approach 1:
The normally on high-voltage transistor and normally off low-voltage transistor are merged into a single integrated semiconductor chip. This integration eliminates the need for external wire connections between the two transistors, reduces parasitic inductances, and simplifies the overall device structure while maintaining the cascode configuration for normally off control functionality.
Solution Approach 2:
The integrated chip serves multiple functions simultaneously: it provides high-voltage switching capability, normally off control, and reduced parasitic inductances all in a single device. The unified structure allows the chip to handle both power switching and control functions without requiring separate packaging and interconnections.
3Speed
If rapid switching transitions are used, then switching speed is improved, but oscillations and electromagnetic disturbances increase
Solution Approach 1:
The switching transitions are made dynamic and adjustable through the control circuit that gates the normally off transistor. The control circuit can modulate the switching edges to optimize the balance between switching speed and electromagnetic disturbance reduction, allowing adaptive control of the switching characteristics based on operational requirements.
Data Source
AI summary
An electronic power component including a normally on high-voltage transistor and a normally off low-voltage transistor. The normally on transistor and the normally off transistor are coupled in cascode configuration and are housed in a single package. The normally off transistor is of the bottom-source type.