Power Module Crossover Delay for Shoot-Through Prevention
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Solution Overview
Problem
In DC drive systems, faults occur due to 'shoot through' currents between forward and reverse power modules during transitions, which are exacerbated by faster switching regulators and longer recovery times in high-power modules, leading to potential damage from re-enabled gate pulses during fixed time delays.
Innovation Solution
A crossover delay system that blocks gate pulses during transitions from forward to reverse or reverse to forward, using crossover detection and lockout logic to ensure one power module is fully off before the other is turned on, independent of drive regulator firing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed time delay is inserted at the power module transition, then shoot through currents are reduced, but gate pulses may be re-enabled in the middle of a gate pulse pattern causing power module damage
Solution Approach 1:
The patent uses feedback by monitoring the actual gate pulse patterns and regulator firing angle changes to dynamically adjust the crossover delay timing. The system detects when gate pulses are shifted due to firing angle changes and modifies the delay accordingly, ensuring that the delay period always aligns with complete gate pulse patterns rather than fixed time intervals.
Solution Approach 2:
The patent transitions from a static fixed time delay to a dynamic delay mechanism that adapts to changing operating conditions. The crossover delay is adjusted in real-time based on regulator firing angle changes and actual gate pulse timing, making the system responsive to dynamic conditions rather than relying on predetermined fixed intervals.
2Productivity
If faster switching is provided by newer regulators, then productivity is improved, but power modules do not have sufficient time to recover before the opposite power module is commanded to turn on
Solution Approach 1:
The patent applies preliminary action by proactively inserting a crossover delay period before the opposite power module is commanded to turn on. This delay is configured to ensure that the current power module has sufficient time to complete its turn-off recovery process before the next power module switches on, preventing shoot through currents while maintaining fast switching overall.
Solution Approach 2:
The patent uses preliminary anti-action by blocking gate pulses to the opposite power module during the crossover delay period. This preventive measure stops the harmful shoot through current from occurring in the first place by ensuring the first power module is fully off before the second power module can turn on.
3Reliability
If gate pulses are blocked during crossover delay, then shoot through currents are prevented, but gate pulse patterns may be interrupted causing power module damage
Solution Approach 1:
The system uses feedback to monitor the regulator firing angle and actual gate pulse timing, adjusting the crossover delay duration dynamically. This ensures that the delay period is synchronized with complete gate pulse patterns, so when gate pulses are re-enabled after the delay, they align with the start of a new complete pulse pattern rather than interrupting an ongoing pattern.
Data Source
AI summary
Systems and methods detect when a transition from a first power module to a second power module is taking place and generates a lockout pulse when the transition is detected. The lockout pulse initiates the blocking of a predetermined number of gate pulses from reaching the second power module. When the predetermined number of gate pulses are blocked, the systems and methods reset to allow complete gate pulses to reach the second module, and continues to detect when the next transition takes place.