Solid-State Pinch-Off Thyristor Circuits for Fast High-Current Switching
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Solution Overview
Problem
Conventional gate turn-off thyristors (GTOs) face challenges with high current requirements for turn-off, long switch-off times, limited controllable current, and difficulties in commutating at high load currents and high dV/dt due to stray inductances, especially in high-power applications.
Innovation Solution
The development of semiconductor bistable switching devices that integrate a thyristor portion with a transistor portion, including a junction field effect transistor (JFET) to control current flow, allowing for voltage-controlled and low-current turn-off functionality, and utilizing silicon carbide (SiC) layers for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional GTO is used to achieve high current switching capability, then the device can handle high load currents, but it requires large turn-off currents and suffers from long switch-off times
Solution Approach 1:
The device is segmented into two functional parts: a GTO portion for high current handling and a transistor portion for rapid turn-off control. The GTO handles the high load current while the transistor provides fast switching action, dividing the functions to resolve the contradiction between high current capability and fast switch-off time
Solution Approach 2:
The transistor acts as an intermediary between the control circuit and the GTO. Instead of directly controlling the GTO with large currents, the transistor mediates the turn-off process by using its fast switching capability to control the GTO's commutation, enabling rapid switch-off without requiring large turn-off currents from the external circuit
2Power
If a conventional GTO is used for high power applications, then it can handle high load currents, but it requires significant turn-off currents that increase power consumption
Solution Approach 1:
The power consumption issue is resolved by segmenting the control function. The transistor portion consumes minimal power for control while the GTO portion handles the high load current. The transistor's low power gate control mechanism eliminates the need for high power turn-off currents that would otherwise be required by a standalone GTO
Solution Approach 2:
The transistor portion serves itself by using voltage-controlled gating rather than current-controlled gating. This self-service mechanism allows the device to achieve turn-off control with minimal external power input, as the transistor can be controlled by small gate voltages rather than requiring large gate currents
3Ease of operation
If discrete GTO and MOSFET are used in cascode configuration, then turn-off control is achieved, but additional conduction losses occur due to the MOSFET resistance
Solution Approach 1:
The GTO and transistor are merged into a single integrated device structure rather than being separate discrete components. This integration allows the transistor to be optimally sized and positioned to minimize its resistance contribution while still providing effective turn-off control. The merged structure eliminates the need for oversized MOSFETs that would be required in discrete cascode configurations, thereby reducing conduction losses
4Device complexity
If conventional thyristor structure is used, then simple structure is maintained, but the maximum controllable current is limited to about twice the rated operating current
Solution Approach 1:
The device segments the current handling and control functions between the GTO and transistor portions. The GTO is designed to handle high currents while the transistor provides control capability. This segmentation allows the controllable current to exceed the limitations of conventional thyristors, as the transistor can control the GTO's turn-off even at currents much higher than the thyristor's rated operating current
Solution Approach 2:
The integrated structure provides multi-functionality: the GTO portion provides high current handling and the transistor portion provides rapid turn-off control. This universal design combines the advantages of both device types, enabling the single device to achieve both high current capability and fast controllability that neither device could achieve alone
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These devices enable efficient and rapid switching with reduced power consumption, improved controllable current capacity, and faster commutation, addressing the limitations of conventional GTOs by integrating a thyristor and JFET for reliable and efficient high-voltage, high-current switching.
Implementation Method 1
a transistor portion on the thyristor portion, the transistor portion including a source, a drain and a transistor gate. The transistor gate may be operable to receive a turn off signal that causes a current conducting channel between the source and the drain to increase in resistance.
Implementation Method 2
utilizing silicon carbide (SiC) layers for enhanced performance
Implementation Method 3
The gate layer may be operable to receive a gate trigger current that, when the anode layer is positively biased relative to the cathode layer, causes the thyristor portion to latch into a conducting mode between the anode and the cathode.
Data Source
AI summary
Provided is a semiconductor bistable switching device that includes a thyristor portion including an anode layer, a drift layer, a gate layer and a cathode layer, the gate layer operable to receive a gate trigger current that, when the anode layer is positively biased relative to the cathode layer, causes the thyristor portion to latch into a conducting mode between the anode and the cathode. The device also includes a transistor portion formed on the thyristor portion, the transistor portion including a source, a drain and a transistor gate, the drain coupled to the cathode of the thyristor portion.