AC-AC Converter With Bidirectional Switch
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Solution Overview
Problem
Existing AC-AC converter devices face high switching losses due to the recovery of slow body-drain diodes in high-frequency switching, which limits efficiency and requires precise timing to prevent phase shift between line and load voltage.
Innovation Solution
The AC-AC converter device incorporates a bidirectional switch and fast recovery diodes, replacing one half-bridge leg, allowing for higher switching frequencies without reverse recovery losses and enabling phase shift between input and output voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-frequency switching is used to improve converter efficiency and reduce filter size, then switching losses increase due to slow body-drain diode recovery
Solution Approach 1:
The patent changes the switching characteristics by using fast recovery diodes instead of slow body-drain diodes, fundamentally altering the recovery time parameter to enable high-frequency operation without excessive losses
Solution Approach 2:
The patent introduces an intermediary circuit configuration with separate rectifier and inverter half-bridge legs, using a common DC bus as mediator to decouple the switching operations and eliminate reverse recovery losses
2Reliability
If precise timing control is implemented to prevent phase shift between line and load voltage, then timing precision requirements increase
Solution Approach 1:
The patent segments the converter into separate rectifier and inverter half-bridge legs with independent switching control, allowing each leg to operate autonomously without requiring precise timing coordination between them
Solution Approach 2:
The common DC bus acts as an intermediary that decouples the timing requirements between input and output stages, eliminating the need for precise phase-synchronized switching
3Reliability
If larger capacitance is used to filter DC voltage and maintain constant voltage over line period, then device size and cost increase
Solution Approach 1:
The patent changes the operating frequency parameter to higher values, which allows reduction of filter component sizes while maintaining the same voltage stability performance
Solution Approach 2:
The patent uses high-frequency periodic switching actions to maintain voltage stability, replacing the need for large energy storage capacitance with frequent switching control
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 reduces switching losses, enhances efficiency, and allows for higher frequency operation with smaller filter components and reduced ripple, while maintaining phase shift capabilities.
Implementation Method 1
The AC-AC converter device incorporates a bidirectional switch and fast recovery diodes, replacing one half-bridge leg, allowing for higher switching frequencies without reverse recovery losses
Implementation Method 2
an input device connected between an input node, a common node, a positive DC terminal and a negative DC terminal, where the input node is connected to the first AC input terminal via a first input inductor
Implementation Method 3
The DC voltage can be provided from a battery or any other type of energy storage. The DC voltage can also originate from a solar panel or a wind generator provided with a suitable energy conversion module
Data Source
AI summary
An AC-AC converter device includes first and second AC input terminals and first and second AC output terminals. An input device is connected between an input node, a common node, a positive DC terminal and a negative DC terminal, wherein the input node is connected to the first AC input terminal via a first input inductor. An output device is connected between an output node, the positive DC terminal and the negative DC terminal, wherein the output node is connected to the first AC output terminal via an output inductor. A common device is connected between the common node, the positive DC terminal and the negative DC terminal, where the common node is connected to the second AC input terminal via a common inductor. A control device is provided for controlling the switches of the output device and the common device.