Anode-Gate Thyristor Control Circuit Using Transistor Mediators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing thyristor control circuits for AC loads often require galvanic isolation or pulse control, which can be costly and complex, especially when controlling anode-gate thyristors in rectifying bridges.
Innovation Solution
A circuit that uses a first transistor to couple the thyristor gate to a terminal with a lower potential, and a second transistor controlled by a microcontroller to manage the gate current, eliminating the need for isolation transformers or optocouplers and pulse control, by using DC voltages and bipolar transistors to control anode-gate thyristors in AC loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolation (isolation transformer or optocoupler) is used for thyristor control, then safety and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary circuit consisting of a first transistor and a second transistor that acts as a mediator between the control signal source and the thyristor gate. This intermediary circuit enables safe control without requiring galvanic isolation, as the transistors provide electrical isolation through their inherent structure while allowing control signal transmission. The first transistor couples the thyristor gate to a terminal with lower potential, and the second transistor controls the gate current, together forming an intermediary control path that resolves the contradiction between safety and complexity.
2Device complexity
If pulse control is used for thyristor control, then device complexity is reduced, but control precision and reliability deteriorate
Solution Approach 1:
The patent employs periodic action by using the natural alternating current cycles to trigger the thyristor at specific points in each half-cycle. The control terminal receives control signals synchronized with the AC voltage half-waves, allowing the thyristor to be triggered at the desired phase angle in each cycle. This periodic triggering mechanism maintains control reliability without requiring complex pulse generation circuits, as it leverages the inherent periodicity of the AC supply.
3Reliability
If isolation transformer is used for galvanic isolation, then control safety is improved, but cost and device complexity increase
Solution Approach 1:
The patent extracts the galvanic isolation function from the traditional isolation transformer and implements it through the transistor-based intermediary circuit. By taking out the isolation requirement and replacing it with transistor structures that provide inherent electrical isolation, the solution eliminates the need for expensive isolation transformers while maintaining safety. The transistors provide the necessary isolation through their semiconductor structure, removing the costly magnetic isolation component from the design.
4Reliability
If optocoupler is used for galvanic isolation, then control safety is improved, but device complexity and cost increase
Solution Approach 1:
The patent substitutes the optocoupler's optical isolation mechanism with a direct electrical control mechanism using transistors. Instead of using light to transfer control signals through an optocoupler, the invention uses electrical signals controlled by transistor switching actions. This substitution replaces the optical field-based isolation with a simpler electrical field-based control, eliminating the need for optocouplers and reducing circuit complexity while maintaining safety through the transistor's inherent isolation properties.
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 solution simplifies the control of anode-gate thyristors in AC loads, reduces costs, and avoids the risks associated with high-frequency pulse control, while maintaining efficient operation of the rectifying bridge.
Implementation Method 1
a first transistor coupling the thyristor gate to a first terminal applying a potential lower than the potential of a second terminal having the thyristor anode connected thereto
Implementation Method 2
a control terminal of the first transistor is coupled, by a second transistor, to a third terminal for supplying a potential which is positive with respect to the potential of the second terminal
Data Source
AI summary
A circuit for controlling an anode-gate thyristor includes a first transistor that couples a thyristor gate to a first terminal to receive a potential lower than a potential of a second terminal connected to the thyristor anode. A control terminal of the first transistor is driven by a control signal which is positive with respect to the potential of the first terminal.