Power Converter Diode Overcurrent Protection via Parallel Switching
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Solution Overview
Problem
Conventional power conversion apparatuses fail to adequately protect diodes connected in parallel with switching devices from deterioration or breakage due to overcurrent, especially when the overcurrent capacity of these diodes is low and the number of free-wheeling diodes is reduced.
Innovation Solution
A power conversion apparatus with a control circuit that switches to a current reduction ON-OFF control mode upon detecting overcurrent, where switching devices connected in parallel with diodes are turned ON to reduce the current flowing through the diodes, thereby distributing the current between the switching devices and diodes, reducing the burden on the diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all switching devices are turned OFF when overcurrent occurs, then the overcurrent is blocked, but the current flows entirely through the diodes causing deterioration or breakage
Solution Approach 1:
The patent segments the overcurrent protection response by controlling different switching devices independently based on their parallel diode status. When overcurrent occurs, the control circuit identifies which diodes are conducting current and selectively turns ON only the switching devices connected in parallel with those specific diodes, rather than turning OFF all switching devices uniformly. This segmentation allows the current to be diverted from vulnerable diodes through specific switching devices, protecting the diodes while maintaining controlled current flow.
2Productivity
If the number of free-wheeling diodes is reduced to minimize dead time, then the efficiency is improved, but the overcurrent capacity of the diodes becomes insufficient
Solution Approach 1:
The patent implements dynamic control of switching devices based on real-time detection of diode current flow. The control circuit continuously monitors which diodes are conducting and dynamically adjusts the switching device states in response to overcurrent conditions. This dynamic response allows the system to maintain high efficiency during normal operation with reduced free-wheeling diodes, while automatically activating protective switching actions when overcurrent threatens diode reliability.
Solution Approach 2:
The patent changes the operational parameters of switching devices based on diode current flow conditions. By detecting when diodes are conducting current and subsequently turning ON the parallel switching devices, the system dynamically alters the electrical parameters (current flow paths, resistance states) to protect diodes during overcurrent events while maintaining efficient operation during normal conditions.
Data Source
AI summary
When an overcurrent detection section detects an overcurrent, a control circuit performs ON-OFF control for switching devices each switchable between a forward direction and a reverse direction, in a mode in which a current having flowed is reduced, such that when the mode is a mode in which a current is passed through any of diodes, a switching device connected in parallel with the current-passed diode is turned ON. Thus, even when an overcurrent occurs, the current flowing in the diode connected in parallel with the switching device is reduced, and the diode is protected from being deteriorated or broken by the overcurrent.