Full-Bridge Converter Precharge to Reduce Power Switch Voltage Stress
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Solution Overview
Problem
Full-bridge power converters face challenges in reducing voltage stress on power switches due to the electrical energy stored in the transformer, which can lead to shortened switch life.
Innovation Solution
The proposed full-bridge power converter includes a transformer circuit, an input-side full-bridge circuit with four power switches, an input inductor, an output-side full-bridge circuit, and an output capacitor. A controller manages the switching of the power switches, releasing energy stored in the transformer during the first period and precharging the output-side full-bridge circuit during the second period, thereby reducing voltage stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transformer stores electrical energy to enable power conversion operation, then the power conversion function is achieved, but voltage stress is applied to the power switch which shortens its life
Solution Approach 1:
The patent applies preliminary action by pre-charging the output-side full-bridge circuit before the main power conversion operation begins. The controller activates the output-side full-bridge circuit in advance to charge the output capacitor, so that when the transformer releases stored energy, the voltage stress on power switches is reduced because the output circuit is already prepared and buffered. This preliminary preparation protects the power switches from excessive voltage stress while maintaining the power conversion function.
2Productivity
If the transformer releases stored electrical energy during operation, then power delivery to the load is enabled, but voltage stress from the transformer reduces power switch reliability
Solution Approach 1:
The patent uses the output capacitor as an intermediary element between the transformer and the power switches in the output-side full-bridge circuit. When the transformer releases stored energy, the output capacitor acts as a buffer that absorbs and smooths the voltage fluctuations, preventing direct high voltage stress from reaching the power switches. This intermediary component enables power delivery while protecting the switches, resolving the contradiction between productivity and reliability.
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 reduces voltage stress on the power switches, minimizing the risk of switch damage and potentially lowering power loss in the converter.
Implementation Method 1
the controller turns on the first power switch, the second power switch, the third power switch, and the fourth power switch during the first period, causing the transformer circuit to release an electric energy stored in the transformer circuit
Implementation Method 2
the controller turns on the first power switch, the second power switch, the third power switch, and the fourth power switch in the second period after the first period, and controls the output-side full-bridge circuit to precharge the output-side full-bridge circuit by using an energy stored in the output capacitor
Data Source
AI summary
A full-bridge power converter is provided. The full-bridge power converter includes a transformer circuit, an input-side circuit, an output-side circuit, and a controller. The input-side circuit includes an input-side full-bridge circuit and an input inductor. The input-side full-bridge circuit includes multiple power switches. The input inductor is coupled between a positive power terminal of the battery module and the input-side full-bridge circuit. The output-side circuit includes an output-side full-bridge circuit and an output capacitor. The controller turns on the power switches during a first period, causing the transformer circuit to release an electric energy stored in the transformer circuit. The controller turns on the power switches during a second period after the first period, and controls the output-side full-bridge circuit to precharge the output-side full-bridge circuit by using an energy stored in the output capacitor.