AC/DC Converter Inrush Current Limitation Thyristor Control
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Solution Overview
Problem
Existing AC/DC converter architectures face challenges in limiting inrush current peaks during startup phases, particularly in systems using rectifying bridges, which often require complex and loss-inducing control circuits.
Innovation Solution
The proposed AC/DC converter incorporates a rectifying bridge with series-connected thyristors and diodes, controlled by a microcontroller generating progressive control pulses to manage the conduction time of thyristors, coupled with capacitive elements and a transformer for gate control, enabling phase-angle control and voltage-doubling functionality to limit inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rectifying bridge control circuits are used, then the converter can operate, but inrush current peaks occur during startup phases
Solution Approach 1:
The patent extracts the inrush current limitation function from complex control circuits by using the inherent properties of series-connected thyristors with progressive conduction time control. The thyristors naturally limit inrush current through their controlled turn-on characteristics, eliminating the need for separate complex control circuits while maintaining reliability.
Solution Approach 2:
The series-connected thyristors self-regulate inrush current through progressive conduction time control. The first thyristor is turned on before the second thyristor, creating a natural ramp-up effect that limits inrush current without requiring external control intervention, thus simplifying the overall control circuit.
2Loss of energy
If series-connected thyristors with progressive control pulses are used, then inrush current is limited, but control circuit implementation becomes more complex
Solution Approach 1:
The patent uses periodic control pulses with progressively increasing conduction time for the series-connected thyristors. During startup, the control circuit generates pulses that gradually increase the conduction angle of each thyristor, reducing startup losses by controlling the rate of capacitor charging while maintaining a relatively simple periodic control mechanism.
Solution Approach 2:
The control circuit dynamically changes the conduction time parameter of the thyristors during startup phases. By progressively increasing the conduction angle from a small initial value to the full cycle value, the system reduces startup losses without requiring complex control logic, as this is achieved through simple timer-based pulse generation.
3Device complexity
If simple control circuits are used, then device complexity is reduced, but inrush current limitation effectiveness decreases
Solution Approach 1:
The patent introduces series-connected thyristors as intermediary elements between the AC input and the output capacitor. These thyristors act as controlled switches that progressively connect the capacitor to the AC source, providing effective inrush current limitation through simple gate control pulses without requiring complex control circuits.
Solution Approach 2:
The control circuit performs preliminary action by turning on the first thyristor before the second thyristor in the series connection. This preliminary conduction allows the capacitor to charge gradually through a controlled path, ensuring effective inrush current limitation while maintaining simple control circuitry based on sequential pulse generation.
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 effectively limits inrush current peaks by progressively increasing thyristor conduction time, reducing startup losses and simplifying control circuits while maintaining compatibility with voltage-doubling operations.
Implementation Method 1
the gates of the thyristors are controlled by a same transformer, excited by an AC signal
Implementation Method 2
the anode gate thyristor being controllable by extraction of a current from its gate
Implementation Method 3
two series-connected capacitive elements couple the third and fourth terminals
Data Source
AI summary
An AC/DC converter includes: a first terminal and a second terminal for receiving an AC voltage and a third terminal and a fourth terminal for supplying a DC voltage. A rectifying bridge includes input terminals respectively coupled to the first terminal and the second terminal, and output terminals respectively coupled to the third terminal and fourth terminal. A first branch of the rectifying bridge includes, connected between the output terminals, two series-connected thyristors with a junction point of the two thyristors being connected to a first one of the input terminals. A second branch of the rectifying bridge is formed by series connected diodes. A control circuit is configured to generate control signals for application to the control gates of the thyristors.