Hybrid BDBJT-FET Unidirectional Switch for High-Power Circuits
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Solution Overview
Problem
Existing electrical systems using high voltages and currents face challenges with high circuit area and cost due to the need for multiple silicon carbide (SiC) switches, and unidirectional switches using field-effect transistors or insulated-gate bipolar transistors (IGBTs with reverse diodes result in inefficiencies.
Innovation Solution
A switch circuit employing a double-base bipolar junction transistor (BDBJT) with field-effect transistors (FETs) and driver circuits for unidirectional operation, reducing the number of switches needed and enhancing efficiency by using a symmetric BDBJT that allows current flow in either direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple silicon carbide (SiC) switches are used to handle high voltages and currents, then the system can operate at high power levels, but the circuit area and cost increase significantly
Solution Approach 1:
The patent combines a bipolar junction transistor (BDBJT) and a field-effect transistor (FET) into a single hybrid switch device. The BDBJT handles high voltage and current with low saturation voltage, while the FET provides efficient switching control. This merging allows the circuit to handle high power levels without requiring multiple separate SiC switches, thereby reducing circuit area while maintaining power handling capability.
2Ease of operation
If unidirectional switches using field-effect transistors or insulated-gate bipolar transistors (IGBTs) with reverse diodes are used, then the switching control is simplified, but efficiency decreases due to additional components
Solution Approach 1:
The hybrid switch merges the BDBJT and FET into a single integrated device where the FET controls the BDBJT's switching. The FET's gate controls the base current of the BDBJT, which in turn controls the main current flow. This integration eliminates the need for separate reverse diodes and simplifies the switching control mechanism while maintaining high efficiency through the BDBJT's low saturation voltage characteristic.
3Adaptability or versatility
If a symmetric double-base bipolar junction transistor (BDBJT) is used to allow current flow in either direction, then the adaptability for different applications is improved, but the device complexity increases
Solution Approach 1:
While the BDBJT itself has a symmetric structure with two bases allowing bidirectional current flow, the patent applies asymmetry through the control mechanism. The FET is connected to control the BDBJT in a specific configuration that enables unidirectional operation when needed. This selective application of symmetry and asymmetry allows the circuit to adapt to different applications - bidirectional when using the BDBJT's natural symmetry, or unidirectional when the FET control is configured for specific directionality, thereby managing device complexity while maintaining versatility.
Data Source
AI summary
A switch circuit for coupling two circuit terminals together is disclosed. The switch circuit includes a double-base bipolar junction transistor and a field-effect transistor coupled, in series, between a first terminal and a second terminal. Various driver circuits may be employed to activate, in response to an activation of a switch signal, the field-effect transistor, and couple one or both of the base terminals of the double-base bipolar junction transistor to voltage sources to initiate base currents to reduce the channel resistance of the double-base bipolar junction transistor.