RC-IGBT Drive Control to Block Free-Wheel Diode Power Loss
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Solution Overview
Problem
In reverse-conducting insulated gate bipolar transistors (RC-IGBTs), the active gate control can inadvertently turn on the switching element during current feedback control, leading to increased power loss and heat generation in the free-wheel diode, which compromises the reliability of the RC-IGBT.
Innovation Solution
A drive unit for RC-IGBTs is designed with a judging means to detect forward current in the free-wheel diode, an inhibiting means to prevent charge transfer during forward current flow, and a disabling mechanism to inhibit active gate control during current feedback, ensuring that the switching element is not erroneously turned on, thereby preventing power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If active gate control is applied to RC-IGBT, then switching loss is reduced and surge voltage is suppressed, but the switching element may be erroneously turned on during current feedback control, accelerating power loss in the free-wheel diode
Solution Approach 1:
The control unit determines in advance whether to permit active gate control based on the operating state of the RC-IGBT. Before active gate control is executed, the control unit checks if the switching element is in a state where active gate control would be harmful (i.e., when forward current is flowing through the free-wheel diode). This preliminary determination prevents erroneous turn-on and the associated power loss acceleration.
Solution Approach 2:
The control unit continuously monitors the operating state of the RC-IGBT, including the current state of the free-wheel diode. Based on this feedback information, the control unit dynamically adjusts whether active gate control is permitted. When forward current is detected in the free-wheel diode, the control unit prohibits active gate control, thereby preventing harmful interactions between the two control modes.
2Productivity
If active gate control is permitted without restriction, then switching performance is improved, but power loss in the free-wheel diode is accelerated when forward current flows
Solution Approach 1:
The permission state for active gate control is made dynamic rather than fixed. The control unit continuously adjusts the permission state based on the real-time operating conditions of the RC-IGBT. When conditions are favorable, active gate control is permitted to optimize switching performance; when conditions are unfavorable (forward current in free-wheel diode), active gate control is prohibited to prevent power loss acceleration.
Data Source
AI summary
In a drive unit for a reverse-conducting switching element which is a driven switching element, a process to transfer electric charges to a conductive control terminal of the driven switching element is performed on the basis of a turn-on command or a turn-off command, thereby turning on and off the driven switching element. A transfer rate of the electric charges is changed in a period from when the transfer of the electric charges to the conductive control terminal is started until when it is completed. While judged that forward current flows in a free-wheel diode, the electric charges are inhibited from being charged to the conduction control terminal which corresponds to the free-wheel diode in which the forward current is judged to flow. While the electric charges are inhibited from being charged to the conductive control terminal, a change of the transfer rate is disabled.