Semiconductor Switch with Capacitor for Bidirectional Blocking
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Solution Overview
Problem
Current four-quadrant switches for AC power conversion applications face challenges such as excessive conduction losses and voltage blocking limitations, making them unsuitable for high-power applications and hindering the development of matrix converters, AC to AC converters, and solid-state circuit breakers.
Innovation Solution
A semiconductor switch configuration using diodes and transistors, with a capacitor providing bidirectional current and voltage blocking capabilities, allowing for efficient power conversion and preventing shoot-through conditions by maintaining a DC bias level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If single-quadrant semiconductors (MOSFETs and IGBTs) with antiparallel diodes are used in a full bridge rectifier, then the circuit can achieve AC power conversion capability, but excessive conduction losses occur due to three semiconductors being in the current conduction path
Solution Approach 1:
The invention divides the single-quadrant switch into two separate single-quadrant switches (first and second switches) that operate in complementary fashion. Each switch handles one polarity of current flow, reducing the number of conducting semiconductors from three to two in the optimized topology, thereby reducing conduction losses while maintaining four-quadrant operation capability
Solution Approach 2:
The patent introduces a capacitor as an intermediary energy storage element between the two single-quadrant switches. This capacitor enables voltage blocking and energy transfer, allowing the switches to operate more efficiently with reduced conduction path while maintaining the required four-quadrant switch functionality for bidirectional current and voltage blocking
2Loss of energy
If two series-connected single-quadrant switches with antiparallel diodes are used, then conduction losses are reduced, but careful sequencing of commutation is required to prevent voltage and/or current overshoots during switching
Solution Approach 1:
The patent employs a capacitor connected in parallel with each switch to provide beforehand cushioning during switching transitions. This capacitor absorbs voltage spikes and current overshoots that occur during commutation, preventing damage to the semiconductors while allowing the use of series-connected topology for reduced conduction losses
Solution Approach 2:
The invention implements control circuitry that monitors the switching states and provides feedback to coordinate the commutation timing of the two switches. This feedback mechanism ensures proper sequencing of switch transitions, preventing voltage and current overshoots while maintaining the reduced conduction loss benefits of the series-connected configuration
3Ease of manufacture
If discrete single-quadrant semiconductor devices are used, then the circuit can be implemented with available components, but the voltage blocking capability places an upper bound on power for high voltage applications
Solution Approach 1:
The patent segments the high voltage blocking requirement across multiple discrete single-quadrant switches connected in series. Each switch only needs to block a portion of the total voltage, making it feasible to implement high power applications using available discrete semiconductor devices while achieving the required overall voltage blocking capability
Solution Approach 2:
The capacitor serves as an intermediary that distributes and balances the voltage across the series-connected switches. By providing a reference potential and enabling controlled charge transfer, the capacitor facilitates the operation of discrete devices at higher overall voltage levels than any single device could handle alone
Data Source
AI summary
A semiconductor switch includes four diodes, two transistors, and a capacitor. The capacitor includes a fourth terminal and a fifth terminal. An anode of a third diode is connected to a third terminal of a first transistor. A cathode of the third diode is connected to a first terminal of the first transistor and to an anode of a first diode. An anode of a fourth diode is connected to a third terminal of a second transistor. A cathode of the fourth diode is connected to a first terminal of the second transistor and to an anode of the second diode. A cathode of the first diode is connected to a cathode of the second diode and to the fourth terminal of the capacitor. An anode of the third diode is connected to the anode of the fourth diode and to the fifth terminal of the capacitor.