IGBT Switching Circuit with Asymmetric Gate Control
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Solution Overview
Problem
In switching circuits using IGBTs, turn-off loss is difficult to reduce at low currents due to the lack of a clear relationship between switching rate and turn-off loss, and the size of the IGBT, making it challenging to minimize losses when current is small.
Innovation Solution
A switching circuit design that includes two IGBTs connected in parallel, with a gate control circuit that adjusts the switching procedure based on current thresholds, turning off one IGBT before the other at low currents to reduce turn-off loss, and distributing current load between both IGBTs at high currents to minimize overall load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the gate resistance is decreased to increase the switching rate, then the turn-off loss decreases at high currents, but the turn-off loss cannot be reduced at low currents
Solution Approach 1:
The patent divides the switching control into two independent controllable parts: the first IGBT and the second IGBT. By controlling them separately through different gate resistance values or switching timings, the system can optimize turn-off loss for each device independently based on current conditions, thereby resolving the contradiction between achieving low turn-off loss at high currents and maintaining effectiveness at low currents
Solution Approach 2:
The patent dynamically adjusts the switching strategy based on current magnitude. When current is high, both IGBTs are switched with low gate resistance to minimize turn-off loss. When current is low, the system adapts by switching only one IGBT or using different gate resistance values, making the control adaptable to varying operating conditions and resolving the effectiveness contradiction
2Power
If both IGBTs are switched simultaneously to distribute current load at high currents, then the load on individual IGBTs is reduced, but the turn-off loss increases at low currents
Solution Approach 1:
The patent implements dynamic switching control where the switching strategy changes based on current magnitude. At high currents, both IGBTs are switched simultaneously to distribute the power load. At low currents, the system dynamically adjusts to switch only one IGBT or use asymmetric gate control, thereby maintaining low turn-off loss while preserving the ability to distribute load when needed
Solution Approach 2:
The patent changes the gate resistance parameter dynamically based on operating conditions. By adjusting gate resistance values for each IGBT independently, the system can optimize both current distribution at high powers and turn-off loss at low powers, resolving the contradiction between these two requirements
Data Source
AI summary
A switching circuit includes a wiring into which a parallel circuit of a first IGBT and a second IGBT is inserted, and a gate control circuit. The gate control circuit has a first switching element configured to control a gate potential of the first IGBT according to a potential of a second principal electrode, and a second switching element configured to control a gate potential of the second IGBT according to a potential of a fourth principal electrode. An output terminal of the control device is connected to the first switching element through a first switch and is connected to the second switching element through a second switch. The control device applies a control signal to the output terminal in a state where the first switch and the second switch are turned on when switching both of the first IGBT and the second IGBT.