Thyristor Anode Gate Control for Fast Turn-Off
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Solution Overview
Problem
Thyristors in semiconductor devices have a prolonged turn-off time due to the time required to evacuate injected holes, which is undesirable for high-power control applications.
Innovation Solution
Active control of the anode gate potential is implemented to reduce turn-off time by ensuring the diode between the anode and anode gate conducts when the thyristor is turned off, allowing for efficient evacuation of holes and maintaining voltage rating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional thyristor structure is used, then device simplicity is maintained, but turn-off time is prolonged due to hole evacuation requirements
Solution Approach 1:
The patent segments the gate function into two independent gates: a cathode gate (CG) and an anode gate (AG). This segmentation allows independent control of hole injection (via CG) and hole evacuation (via AG), enabling the turn-off process to be decoupled from the turn-on process. The anode gate specifically accelerates hole evacuation from the n-type drift region, thereby reducing turn-off time without affecting the basic thyristor structure.
Solution Approach 2:
The anode gate acts as an intermediary element that facilitates hole evacuation from the n-type drift region. By applying a positive voltage to the anode gate relative to the anode, an electric field is created that actively extracts holes from the drift region, serving as a mediator between the anode and the external circuit to accelerate the turn-off process.
2Speed
If turn-off time is reduced by active hole evacuation, then switching speed improves, but device structure becomes more complex
Solution Approach 1:
The anode gate structure serves multiple functions: it accelerates hole evacuation during turn-off, maintains voltage rating during operation, and can be integrated into existing thyristor fabrication processes. The dual-gate configuration allows the device to maintain high switching speed while preserving compatibility with conventional thyristor designs, making the complexity manageable through multi-functionality.
3Productivity
If anode gate potential is controlled to conduct diode during turn-off, then hole evacuation efficiency increases, but control complexity increases
Solution Approach 1:
The anode gate is activated periodically during the turn-off phase of the thyristor operation. A positive voltage pulse is applied to the anode gate relative to the anode when turn-off is required, creating a periodic control action that synchronizes with the switching cycle. This periodic activation ensures holes are evacuated efficiently during the critical turn-off period without requiring continuous control complexity.
Solution Approach 2:
The control system monitors the thyristor's on-state current and timing to determine when to activate the anode gate for hole evacuation. By providing feedback on the operational state of the thyristor, the control circuit can precisely time the anode gate activation to coincide with the optimal moment for hole evacuation, maximizing efficiency while minimizing unnecessary control complexity.
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
This approach significantly reduces the turn-off time of the thyristor while maintaining voltage rating, enabling faster switching operations and potentially smaller, more integrated device designs.
Implementation Method 1
a potential higher than that of said anode is applied to said anode gate, so that the diode between said anode and said anode gate of said thyristor conducts
Data Source
AI summary
A semiconductor device having a thyristor SCR with reduced turn-off time. A third semiconductor region of the second conductivity type (anode AN) and a fourth semiconductor region of the first conductivity type (anode gate AG) are formed in the top layer of a first semiconductor region; fifth semiconductor region of the first conductivity type (cathode CA) and sixth semiconductor region of the second conductivity type (cathode gate CG) are formed in the top layer of a second semiconductor region; a gate insulating film and gate electrode MG are formed on the second semiconductor region. When the thyristor is turned off from the on state, a higher potential than that on the anode is applied to the anode gate, and a diode made up of the anode and the anode gate inside the thyristor is made to conduct so as to control the potential of the anode during driving.