AC-DC Converter Boost Front End Flat Current Active Blanking
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Solution Overview
Problem
Existing AC-DC power supply topologies with flyback converters face suboptimal utilization of energy storage components and large component sizes due to varying input voltages, leading to inefficient power density, especially in multi-voltage systems.
Innovation Solution
A power converter design incorporating an input boost converter stage operating in flat current mode with active blanking, coupled with a flyback converter stage, maintains a constant DC bus voltage over a wide range of AC input voltages, optimizing energy storage component utilization and reducing component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relatively large DC bulk capacitor is used to store sufficient energy during zero-crossing intervals, then the converter can power the load during low line input voltages, but the capacitor size and voltage rating increase, reducing power density
Solution Approach 1:
A boost converter stage is introduced as an intermediary between the rectifier and the bulk capacitor. This boost stage actively regulates the DC bus voltage, preventing it from dropping during zero-crossing intervals. The boost converter transfers energy from the input to the DC bus, serving as a mediator that eliminates the need for oversized capacitors to handle voltage sags.
Solution Approach 2:
The boost converter performs preliminary action by maintaining the DC bus voltage at the desired level before the zero-crossing intervals occur. By continuously regulating the voltage during the entire AC cycle including zero-crossings, the system prepares and maintains adequate voltage levels in advance, eliminating the need for large energy storage capacity in the bulk capacitor.
2Adaptability or versatility
If the flyback transformer turns ratio is selected for proper output regulation over the expected DC voltage range, then the transformer can work with DC bus voltage variation from 70V to 375V, but the transformer size increases with excessive design margin, reducing utilization efficiency
Solution Approach 1:
The boost converter changes the DC bus voltage parameter from a widely varying range (70V to 375V) to a tightly regulated range around a nominal value (e.g., 400V). This parameter transformation allows the flyback transformer to be designed for a specific, optimized turns ratio rather than requiring excessive design margin to accommodate wide voltage variations, thereby reducing transformer size while maintaining adaptability through the boost stage's voltage regulation.
3Reliability
If a high voltage rating capacitor (400V or higher) is used to accept the rectified peak voltage at high line input voltages, then the capacitor can handle the maximum DC voltage, but the capacitor size and cost increase, reducing power density
Solution Approach 1:
The boost converter acts as an intermediary that decouples the rectifier output voltage from the bulk capacitor voltage. The boost stage's regulated output provides a stable DC bus voltage to the capacitor, allowing the capacitor to be rated for this lower, regulated voltage rather than the peak rectified voltage, thereby reducing capacitor size while maintaining reliable voltage handling capability.
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 design enhances power density by allowing smaller, more efficiently utilized energy storage components and transformer designs, maintaining stable output voltage regulation across varying input voltages.
Implementation Method 1
a current flowing through an inductor of the boost converter
Implementation Method 2
a primary resonant flyback converter
Data Source
AI summary
A power converter can include an input boost converter stage having an input configured to receive a rectified AC input voltage and an output configured to deliver a DC bus voltage and a second switching converter stage having an input configured to receive the DC bus voltage and an output configured to deliver a regulated output voltage. The input boost converter may be configured to be operated in a flat current mode to maintain a substantially constant DC bus voltage over a broad range of AC input voltages. The input boost converter may be further configured to be operated in an active blanking mode, wherein operation of the boost converter is prevented during a controlled blanking interval of each cycle of the rectified AC input voltage. The controlled blanking interval may be increased responsive at least in part to an increase in the AC input voltage and/or may be decreased responsive at least in part to a decrease in the AC input voltage.