Selective Dead-Time Insertion in Power Converter Phase Legs
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Solution Overview
Problem
In electric drive systems of electrified vehicles, the insertion of dead-time in switching devices to prevent shoot-through introduces distortion and control delays in the output waveform, which is undesirable.
Innovation Solution
A power converter system that selectively inserts dead-time into gate signals based on the magnitude of current flow, only inserting dead-time for the switching device not carrying the current to avoid shoot-through while minimizing distortion and control delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead-time is inserted into gate signals to prevent shoot-through, then reliability is improved, but manufacturing precision deteriorates due to waveform distortion
Solution Approach 1:
The patent applies local quality by selectively inserting dead-time only in specific phase legs where current flow indicates potential shoot-through risk, rather than uniformly applying dead-time to all phase legs. This localized approach prevents shoot-through in critical areas while maintaining waveform quality in non-critical areas, thus resolving the contradiction between reliability improvement and waveform distortion prevention.
2Reliability
If dead-time is inserted into gate signals to prevent shoot-through, then reliability is improved, but productivity deteriorates due to control delays
Solution Approach 1:
The patent implements local quality by applying dead-time insertion selectively only to phase legs where current sensors detect potentially dangerous current conditions, rather than applying it universally. This selective application minimizes the overall control delays in the system while still providing shoot-through prevention where needed, thus resolving the contradiction between reliability improvement and productivity maintenance.
Data Source
AI summary
A power converter has one or more phase legs, each with upper and lower switching devices. A current sensor detects a magnitude of a current flow from a respective leg. A gate driver activates the upper and lower devices according to gate signals determined in response to a PWM control signal. When the detected current magnitude is greater than a positive threshold then the lower gate signal includes a dead-time insertion and the upper gate signal does not include a dead-time insertion. When the detected current magnitude is less than a negative threshold then the upper gate signal includes a dead-time insertion and the lower gate signal does not include a dead-time insertion. When the detected current magnitude is between the positive threshold and the negative threshold then the upper gate signal and the lower gate signal both include a dead-time insertion. Output distortion and control delay are greatly reduced.