Hybrid Switch Circuit Timing for Low-Loss Bidirectional Switching
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Solution Overview
Problem
Existing electrical systems using silicon carbide (SiC) switches for high voltage applications face inefficiencies due to the need for multiple switches in parallel, increased power consumption, and slow transition times of bidirectional double-base bipolar junction transistors, leading to high power dissipation and reduced efficiency.
Innovation Solution
A hybrid switch circuit combining SiC switches and bidirectional double-base bipolar junction transistors, where the SiC switches remain closed during the transition of bipolar junction transistors from closed to open, minimizing power dissipation by reducing the time the hybrid switch is dissipating power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bidirectional double-base bipolar junction transistors are used for high voltage switching, then bidirectional switching capability is achieved, but transition time increases and power dissipation increases
Solution Approach 1:
The bidirectional switch is segmented into two separate unidirectional switches (first and second unidirectional switches) that operate in complementary fashion. Each unidirectional switch handles one polarity of current flow, allowing for faster individual transitions while collectively providing bidirectional capability. This segmentation resolves the contradiction by achieving bidirectional functionality without the slow transition times of a single bidirectional device.
Solution Approach 2:
The control circuit dynamically manages the switching states of the two unidirectional switches based on the direction of current flow and switching requirements. By actively controlling which switch is conducting and managing the transition timing, the system achieves fast bidirectional switching. The dynamic control allows optimal performance for both forward and reverse current directions without being constrained by the fixed characteristics of a static bidirectional device.
2Power
If multiple switches are used in parallel to handle high voltage and current, then current handling capability is improved, but device complexity and power consumption increase
Solution Approach 1:
Two unidirectional switches are merged into a single bidirectional switch configuration, effectively reducing the total number of active switching devices needed. The control circuit integrates the operation of both unidirectional switches, managing them as a unified bidirectional switching element. This merging approach maintains high current handling capability while reducing device complexity compared to using multiple independent switches in parallel.
Solution Approach 2:
The bidirectional switch provides multi-functional capability by handling both forward and reverse current directions with a single device configuration. Instead of requiring separate unidirectional switches for each direction, the bidirectional switch performs multiple functions (forward conduction, reverse conduction, forward blocking, reverse blocking) within a unified structure, reducing overall system complexity while maintaining high power handling capability.
Data Source
AI summary
A hybrid switch circuit for coupling two circuit terminals together is disclosed. The hybrid switch circuit includes a set of bidirectional switch devices coupled between a first circuit terminal and a second circuit terminal. The hybrid switch circuit also includes a set of unidirectional switch devices that are also coupled between the first circuit terminal and the second circuit terminal. In some cases, the set of bidirectional switch devices may be implemented using bidirectional double-base bipolar junction transistors, while the set of unidirectional switch devices may be implemented using wide bandgap transistors. In response to a de-assertion of a switch signal, a control circuit may open the set of bidirectional switch devices and, after a period of time has elapsed, open the set of unidirectional switch devices.