Parallel Thyristor Gate Voltage Sensing for Trigger Detection
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Solution Overview
Problem
Detecting if a thyristor has been properly triggered in an electric circuit with multiple parallel-connected thyristors is challenging, as existing methods like temperature sensors provide delayed feedback and current sensors increase costs and circuit complexity.
Innovation Solution
An electric circuit with gate drive units that measure the gate voltage of each thyristor after gate pulses, using voltage sensors and configurable integrated circuits to determine if thyristors have been triggered, and adjust gate pulses based on measured voltages to improve current symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature sensors are used to monitor parallel-connected thyristors, then detection capability is provided, but feedback delay occurs due to thermal constraints
Solution Approach 1:
The patent replaces temperature-based thermal sensing with direct electrical voltage measurement at the gate terminal. Instead of using temperature sensors that rely on thermal diffusion (mechanical/thermal system), the invention uses voltage sensors to directly measure the electrical parameter (gate voltage) that immediately reflects thyristor triggering status. This substitution of measurement principle eliminates the inherent thermal delay while maintaining reliable detection capability.
2Reliability
If current sensors are used to detect current flow through each thyristor, then triggering detection is achieved, but cost and circuit complexity increase
Solution Approach 1:
The patent extracts the essential information needed for triggering detection (gate voltage level) from the complex current measurement system. Instead of measuring current directly through each thyristor using current sensors, the invention measures the gate voltage, which is a simpler electrical parameter that directly indicates whether the thyristor has been triggered. This extraction of the key diagnostic parameter simplifies the overall circuit while maintaining detection reliability.
Solution Approach 2:
The gate voltage measurement serves multiple functions: it detects triggering status, provides feedback for synchronization, and enables protection functions. By using a single measurement point (gate voltage) that provides multiple diagnostic capabilities, the invention avoids the need for separate current sensors for each thyristor, thereby reducing circuit complexity while maintaining comprehensive monitoring.
3Reliability
If voltage across parallel-connected thyristors is monitored, then triggering detection may be achieved, but the method is not suitable for parallel-connected thyristors due to voltage breakdown
Solution Approach 1:
The patent applies local quality by measuring the gate voltage at the specific gate terminal of each individual thyristor rather than monitoring the overall voltage across parallel-connected devices. This localized measurement at the control terminal provides triggering status information for each thyristor independently, making the method suitable for parallel connections where voltage breakdown occurs. Each thyristor's gate voltage can be measured and evaluated separately without being affected by the parallel connection voltage characteristics.
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2
AI summary
An electric circuit is described. The electric circuit may be part of a power converter and may include a plurality of electrically connected thyristors (Ta, Tb, ..., Tn). Each thyristor (Ta, Tb, ..., Tn) has a gate terminal (26a, 26b, ..., 26n) electrically connected to a gate drive unit (28a, 28b, ..., 28n) adapted to generate gate pulses for triggering the thyristor. At least one of the plurality of gate drive units (26a, 26b, ..., 26n) is adapted to measure the gate voltage of the respective thyristor (Ta, Tb, ..., Tn) after one or more gate pulses have been applied to the respective thyristor. The measured gate voltage may be used to determine if a thyristor has not been triggered by the gate pulse(s) - e.g., if the gate voltage is below a voltage threshold.