Series Switching Circuits With Passive Transient Voltage Equalization
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Solution Overview
Problem
Semiconductor-based switching devices connected in series face challenges in ensuring equal voltage sharing during switching transients due to delays, parameter differences, and parasitic elements, leading to potential voltage unbalance and divergence over time.
Innovation Solution
The apparatus incorporates switching device voltage balancing circuits (VBCs) with electrical energy storage modules and resistive current paths to limit maximum voltage across each switching device, using passive voltage regulation to maintain voltage within a predefined threshold, thereby controlling voltage without active feedback systems and minimizing energy dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If semiconductor-based switching devices are connected in series to create high-power apparatus, then power capability and reliability are improved, but voltage sharing between devices becomes unbalanced during switching transients
Solution Approach 1:
The patent applies preliminary action by pre-charging the switching devices to equal voltages before the main switching event. The pre-charging circuit equalizes the voltage across all series-connected switching devices before they are subjected to high voltage stress, preventing voltage unbalance during switching transients. This proactive equalization eliminates the need for complex feedback control during operation.
Solution Approach 2:
The patent introduces an intermediary pre-charging circuit that mediates between the voltage source and the series-connected switching devices. This intermediary circuit includes resistors and capacitors that temporarily equalize the voltage distribution across the switching devices during the pre-charging phase, acting as a buffer that prevents direct voltage stress imbalances on the devices.
2Reliability
If very fast dynamic feedback systems are employed to address voltage mismatch, then voltage sharing is improved, but system complexity and cost increase significantly
Solution Approach 1:
The patent applies self-service by designing a pre-charging circuit that automatically equalizes voltages across switching devices without requiring external control or feedback. The circuit uses passive components (resistors, capacitors) that inherently balance the voltages through their natural charge-discharge characteristics, eliminating the need for complex active feedback control systems.
Solution Approach 2:
The patent uses inexpensive passive components (resistors, capacitors) in the pre-charging circuit that are temporarily active only during the pre-charging phase. These simple, low-cost components replace expensive and complex active feedback control systems, providing adequate voltage equalization for the brief period needed before normal operation begins.
3Manufacturing precision
If delay in switching command is reduced to improve voltage sharing, then switching precision is improved, but switching speed and response time are compromised
Solution Approach 1:
The patent performs the voltage equalization action preliminarily, before the main switching event. The pre-charging circuit equalizes voltages across all switching devices in advance, so that when the main switching command is issued, all devices are already at equal voltages and can switch simultaneously without precision timing requirements. This separates the precision requirement from the switching speed requirement.
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 configuration effectively controls voltage across series-connected switching devices, reducing voltage mismatch and energy losses, and is scalable for industrial applications, eliminating the need for complex active control systems.
Implementation Method 1
Each of the plurality of switching device VBCs comprises an electrical energy storage (EES) module which can be charged or discharged
Implementation Method 2
current is conducted from the EES module to the at least one resistor via the at least one EES module VRC such that the voltage of the EES module is decreased
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An apparatus (100) is provided, comprising a plurality of interconnected switching devices (1, 2) at least two of which are connected in series so as to form at least one series-connection of switching devices, and a plurality of switching device voltage balancing circuits, VBCs, (3, 4) each of which corresponds to and is connected to a respective switching device (1, 2) of the at least one series-connection of switching devices (1, 2), for limiting the maximum voltage that each switching device (1, 2) of the at least one series-connection of switching devices (1, 2) is subjected to. Each of the plurality of switching device VBCs (3, 4) comprises an electrical energy storage, EES, module (6, 7), and a resistive current path (8, 9) comprising at least one resistor (10, 11), and at least one EES module voltage regulating circuitry, VRC, (12, 13) connected or connectable to the EES module (6, 7), wherein the at least one EES module VRC (12, 13) is configured such that it conducts current therethrough in a direction towards the at least one resistor (10, 11) when the voltage over the at least one EES module VRC (12, 13) is within a predefined threshold voltage range.