Transistor Gate Control Circuit for Cut-Off Overvoltage Suppression
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Solution Overview
Problem
Existing solutions for reducing overvoltage in transistors during cut-off in static converters fail to achieve a satisfactory balance between cost, reaction speed, space occupancy, and electrical losses, particularly when a short circuit occurs.
Innovation Solution
A device with a main control circuit and an auxiliary control circuit that injects an auxiliary current opposed to the current flowing between the main control circuit and the control electrode of the transistor, reducing the temporal variation of current and overvoltage by acting as a capacitor when the transistor is cut off, allowing for fast reaction without high costs or space occupancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transistor is cut off quickly to avoid excessive heating, then the reaction speed is improved, but the overvoltage at the transistor terminals increases
Solution Approach 1:
The auxiliary control circuit applies a counteracting influence before the overvoltage can fully develop. When the transistor is cut off, the auxiliary circuit detects the rapid current decrease and immediately applies a compensating magnetic field through the auxiliary winding, which counteracts the voltage spike caused by parasitic inductances, thereby preventing excessive overvoltage while maintaining fast switching
2Object-affected harmful factors
If known solutions with high-voltage diodes and Zener diodes are used to reduce overvoltage, then the overvoltage is reduced, but the cost and device complexity increase
Solution Approach 1:
The control circuit is enhanced with an auxiliary winding that serves multiple functions: it detects the transistor cut-off event, generates the necessary compensating signal, and applies the counteracting magnetic field. This multi-functional approach eliminates the need for separate protective components like high-voltage diodes and Zener diodes, reducing both cost and device complexity while maintaining overvoltage protection
Solution Approach 2:
The control circuit serves its own protective function by using its existing infrastructure (the auxiliary winding) to detect and counteract overvoltage conditions. The circuit monitors its own operating state and automatically applies the necessary compensating action, eliminating the need for external protective components
3Object-affected harmful factors
If gate resistance is increased to limit overvoltage during short circuit cut-off, then the overvoltage is reduced, but the reaction speed decreases
Solution Approach 1:
The solution dynamically adjusts the effective gate resistance based on the operating condition. During normal operation, the gate resistance remains low for fast switching. When a short circuit occurs and the transistor is cut off, the auxiliary control circuit activates, effectively increasing the gate resistance only at that moment to limit the overvoltage, then returning to normal operation with low resistance for fast response
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
The auxiliary control circuit effectively reduces overvoltage at the transistor terminals, preventing degradation and damage, while being compatible with conventional drivers and not increasing costs or space requirements.
Implementation Method 1
when the transistor is cut off, it acts as a capacitor between the control electrode and one of the other electrodes of the transistor. The reduction of the current flowing from the control electrode toward the main control circuit as a result of the injection of the auxiliary current makes it possible to reduce the temporal variation of the current flowing between the other electrodes of the transistor, and consequently the overvoltage in the transistor
Data Source
AI summary
A device for controlling at least one transistor is disclosed. The device includes the transistor, which includes a control electrode and two other electrodes, a main control circuit connected to the control electrode of the transistor and configured to control the state of the transistor in a main operating mode, and an auxiliary control circuit configured to inject, in an auxiliary operating mode. An auxiliary current opposed to the current flows between the main control circuit and the control electrode of the transistor.