Full-Bridge Active Short Circuit Control for Power Converter Fault Protection
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Solution Overview
Problem
Existing power converter circuits face challenges in handling fault conditions, particularly when Active Short Circuit (ASC) currents exceed the RMS capacity of the low side or lower-bridge switches, leading to overheating and potential damage.
Innovation Solution
The solution involves strategically sequencing the switches of a full bridge circuit to conduct ASC without rectifying current to the DC-bus, effectively blocking current from rectifying back to the DC bus and eliminating the need for dead time, which prevents shoot-through conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If half-bridge ASC implementation is used (turning OFF all high side switches and turning ON all low side switches), then the motor phases are effectively shorted, but the ASC currents can exceed the RMS capacity of the low side switches causing overheating and permanent damage
Solution Approach 1:
The bridge circuit is divided into two functional halves: the upper-bridge half and the lower-bridge half. During ASC operation, only one half is activated at a time to conduct the short-circuit current, while the other half remains inactive. This segmentation distributes the ASC current handling responsibility, ensuring that no single switch or switch pair must handle the full ASC current magnitude, thereby preventing overload and damage.
Solution Approach 2:
The patent employs periodic alternation between upper-bridge ASC and lower-bridge ASC operation. The controller switches between these two ASC modes in a periodic fashion, allowing each half of the bridge to handle ASC currents during its designated time interval. This periodic action ensures that the RMS current through each switch remains within safe operating limits while maintaining continuous fault protection.
2Reliability
If dead time is introduced to prevent shoot-through conditions during switching, then switch safety is improved, but current diode-rectifies back to the DC-bus causing unintended regeneration current and/or DC-bus voltage rise
Solution Approach 1:
The patent extracts and eliminates the dead time requirement from the ASC operation by using complementary switch pairs. Instead of introducing dead time that would allow diode rectification and unintended regeneration, the controller directly transitions between complementary switches (e.g., from high-side to low-side switch) without a non-conducting interval. This extraction of dead time prevents the harmful diode rectification effect while maintaining shoot-through protection through proper complementary switching.
3Strength
If full-bridge ASC is used to handle excess currents, then the RMS current each switch must carry is halved, but switching between lower and upper bridge activation requires dead time causing current to diode-rectify back to the DC-bus
Solution Approach 1:
The patent implements dynamic complementary switching control where the controller actively manages the transition between upper-bridge and lower-bridge ASC modes. By dynamically adjusting which half-bridge is active based on real-time operating conditions and using complementary switch pairs, the system achieves continuous ASC current handling without dead time. This dynamic control allows the full-bridge configuration to utilize both halves effectively, halving the RMS current per switch while preventing diode rectification through seamless complementary transitions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows the full bridge to handle excess ASC currents, reducing the risk of switch damage and overheating, while also lowering the bill of materials costs and improving the robustness of the power converter to failure.
Implementation Method 1
By sequencing the bridge switches strategically, the switch diodes can be utilized to allow opposing switch operation without requiring the dead time, effectively blocking current from rectifying to the DC bus
Data Source
AI summary
Apparatus, methods and articles implement active short circuit (ASC) or diode blocking ASC using a full bridge, alternating between halves (low side, high side) for implementing the ASC via strategic switching of the full bridge. Current is circulated through an inductor, low DC voltage rail with low side switches ON. Current then circulated through the inductor, low DC voltage rail via a diode across an OFF low side switch, with one low side switch ON and one OFF. Current is then passed through the inductor from high side to low side voltage rails via a high and a low side switch in ON states. Current is then circulated through the inductor, high DC voltage rail via a diode across an OFF high side switch, with one high side switch ON and one OFF. Current is the circulated through the inductor, high DC voltage rail with the high side switches ON.