AC/DC Converter With Bidirectional Switch and Leakage Transformer
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Solution Overview
Problem
Conventional AC/DC converters face inefficiencies when handling middle or high power, experiencing increased peak current in secondary windings, potential for unintentional forward operation leading to abnormal heating or breakdown, and require complex circuits for software switching and reduced responsiveness due to constant delay times and high drive current consumption.
Innovation Solution
The AC/DC converter employs a leakage transformer with a bidirectional switch, resonant capacitor, full-wave rectification, and a control circuit to extract both forward and flyback voltages, enabling zero-volt switching and reducing switching losses, while a driving circuit charges and discharges parasitic capacitors to manage gate voltage efficiently, minimizing current consumption and enhancing responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional AC/DC converter uses only flyback voltage output with selected ON/OFF ratio, then the converter can operate, but peak current in secondary winding increases making it unsuitable for middle or high power applications
Solution Approach 1:
The patent segments the voltage output into two distinct components: forward voltage (extracted during switch ON period) and flyback voltage (extracted during switch OFF period). By separating these voltage components and processing them through different circuits (forward voltage circuit and flyback voltage circuit), the converter can utilize both voltage types to deliver power, thereby reducing peak current requirements while maintaining high power handling capability.
2Device complexity
If a conventional AC/DC converter uses constant delay time for software switching, then the switching control is simplified, but switching drive timing errors occur leading to deteriorated conversion efficiency
Solution Approach 1:
The patent implements a feedback mechanism where the actual voltage across the resonant capacitor is continuously monitored. Based on this real-time feedback, the control circuit dynamically adjusts the switching drive timing to achieve precise zero-voltage switching. This feedback-based timing control eliminates the timing errors inherent in constant delay methods while maintaining relatively simple control logic.
3Ease of operation
If a conventional driving circuit continuously applies drive voltage to primary winding during ON/OFF pulse output, then the switching element can be driven, but drive current continuously increases over time causing large current consumption
Solution Approach 1:
The patent employs periodic pulse-width modulation to drive the switching element. Instead of continuously applying drive voltage, the control circuit applies voltage only during specific ON and OFF pulses with controlled widths. This periodic driving method, combined with resonant capacitor discharge control, ensures the switching element is driven effectively while minimizing average current consumption by eliminating continuous voltage application.
4Extent of automation
If a conventional AC/DC converter activates when excitation energy becomes zero with constant delay, then the switching can be controlled, but the delay time is not accurate as it varies with input and output state
Solution Approach 1:
The patent replaces the mechanical/time-based constant delay mechanism with an electronic sensing and control system. Instead of using a fixed delay circuit, the control circuit electronically detects the actual voltage across the resonant capacitor in real-time and generates switching drive signals based on this detected state. This substitution of mechanical delay with electronic sensing achieves precise timing adaptation to varying input and output conditions.
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 allows for high-efficiency direct conversion of AC to DC voltage in middle or high power applications, reducing peak current, preventing abnormal heating, and simplifying circuitry for precise software switching and improved responsiveness.
Implementation Method 1
a transformer (10) including a primary winding (11) connected to an AC power source and a secondary winding (12) electromagnetically coupled to the primary winding
Implementation Method 2
a resonant capacitor (30) connected in parallel or series to the bidirectional switch (20)
Implementation Method 3
a full-wave rectification circuit (40) arranged to perform full-wave rectification of an induced voltage generated in the secondary winding
Data Source
AI summary
An AC/DC converter includes a transformer including a primary winding connected to an AC power source and a secondary winding electromagnetically coupled to the primary winding, a bidirectional switch connected in series to the primary winding, a resonant capacitor connected in parallel or series to the bidirectional switch, a full-wave rectification circuit arranged to perform full-wave rectification of an induced voltage generated in the secondary winding, a smoothing capacitor arranged to smooth an output of the full-wave rectification circuit, and a control circuit arranged to turn on and off the bidirectional switch. The transformer is a leakage transformer or a resonant transformer having leakage inductance. The AC converter takes out both forward voltage and flyback voltage from the secondary winding, so as to directly convert an AC input voltage supplied from the AC power source into a DC output voltage.