Dual-Active-Bridge Snubber Control for Low-Loss ZVS Switching
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Solution Overview
Problem
Conventional Dual-Active-Bridge (DAB) power converters face challenges in achieving both low turn-off and turn-on switching losses, particularly at high load currents, due to high dv/dt leading to commutation losses, parasitic transistor activation, and increased switching noise, which conventional capacitors struggle to mitigate without compromising ZVS.
Innovation Solution
Incorporation of a dynamically controlled snubber circuit with a snubber capacitor and switch in parallel to switching devices, managed by a controller to minimize turn-off losses and achieve Zero Voltage Switching (ZVS) while reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching frequency is increased to improve power density, then power density increases, but turn-off switching losses and electromagnetic interference increase due to high dv/dt
Solution Approach 1:
The patent applies beforehand cushioning by introducing a snubber circuit that is activated before the main switching device turns off during high current conditions. The snubber capacitor is pre-charged and ready to provide a discharge path for the transistor's parasitic capacitance, cushioning the voltage rise and reducing dv/dt before the actual turn-off occurs. This prevents high turn-off losses and reduces electromagnetic interference while allowing high-frequency operation for improved power density.
2Power
If high load currents are operated to increase power output, then power output increases, but turn-off switching losses increase due to high current stress on transistors
Solution Approach 1:
The patent introduces the snubber circuit as an intermediary element between the transistor and the load. The snubber capacitor acts as a mediator that provides an alternative current path during transistor turn-off, absorbing the high current stress that would otherwise flow directly through the transistor. This intermediary structure enables the system to operate at high power output levels while the snubber circuit handles the harsh switching conditions, protecting the transistor from excessive current stress and reducing turn-off losses.
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
The solution effectively reduces turn-off switching losses, enhances reliability, and improves efficiency and adaptability under varying load conditions, while maintaining ZVS capability, thus improving the performance and longevity of DAB power converters.
Implementation Method 1
a snubber circuit comprising: a snubber capacitor; and a snubber switch disposed in series to the snubber capacitor
Data Source
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AI summary
Disclosed is a power converter (100) and a method (500) for operating thereof. The power converter comprises two or more switching devices (102A-H); a snubber circuit (104A-D) disposed in parallel to at least one of the two or more switching devices. The snubber circuit comprises a snubber capacitor (106A-D); and a snubber switch (108A-D) disposed in series to the snubber capacitor. The power converter further comprises a controller (110) configured to control switching of the snubber switch in each snubber circuit to minimize turn-off switching losses in the power converter while achieving Zero Voltage Switching (ZVS).