HV Switch Snubber Feedback for Series Voltage Balancing
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Solution Overview
Problem
High voltage (HV) switches with series-connected semiconductor switches face challenges in balancing voltage distribution due to timing deviations and unequal power loss distribution, leading to potential switch destruction from overvoltage stress.
Innovation Solution
A method is introduced to balance voltage distribution by associating a snubber arrangement with each switch, determining voltages across snubber energy storage components, comparing these voltages, and adjusting the drive signal of at least one switch based on the comparison to achieve equal voltage distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If semiconductor switches are connected in series to achieve high voltage switching capability, then the voltage handling capability is improved, but the voltage distribution uniformity deteriorates due to timing deviations and different capacitances
Solution Approach 1:
The patent adjusts the drive signal parameters (timing, voltage level, or pulse width) of individual semiconductor switches based on detected voltage distribution conditions. By dynamically changing these parameters, the system compensates for timing deviations and capacitance differences, achieving uniform voltage distribution across the series-connected switches while maintaining high voltage handling capability.
2Power
If the number of semiconductor switches in series is increased to handle higher voltages, then the voltage handling capability is improved, but the complexity of voltage balancing control increases
Solution Approach 1:
The patent divides the high voltage switching system into multiple independently controllable segments (individual semiconductor switches), each equipped with its own voltage detection and control circuitry. This segmentation allows distributed control where each switch manages its own voltage share, reducing the overall control complexity compared to centralized control of the entire switch stack.
Solution Approach 2:
The patent implements a feedback mechanism where the voltage across each semiconductor switch is continuously detected and fed back to the control system. Based on this feedback information, the drive signals are automatically adjusted to maintain uniform voltage distribution, enabling self-balancing operation that simplifies control as the system automatically corrects imbalances without complex external intervention.
3Manufacturing precision
If simultaneous switching of all semiconductor switches is enforced to balance voltage distribution, then the voltage distribution uniformity is improved, but the risk of overvoltage stress due to signal propagation delay dispersion increases
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the drive signal timing of individual semiconductor switches based on their position in the series connection and known propagation delay characteristics. This preemptive timing adjustment compensates for signal propagation delays before switching occurs, ensuring that all switches transition simultaneously without experiencing overvoltage stress, thus achieving both uniform voltage distribution and safe operation.
Data Source
AI summary
A method of balancing voltage distribution over a plurality of switches connected in series with each other in a high voltage (HV) switch is provided. A snubber arrangement is associated with each switch of the plurality of switches. The method includes, for a first snubber arrangement associated with a first switch of the plurality of switches, determining a first voltage across a first snubber energy storage component of the first snubber arrangement associated with the first switch. The method further includes, for a second snubber arrangement associated with a second switch of the plurality of switches, determining a second voltage across a second snubber energy storage component of the second snubber arrangement associated with the second switch. The method further includes comparing the first voltage and the second voltage and, based on the comparison, adjusting a first drive signal of at least the first switch based on the first voltage.