Series Switching Units for High-Voltage AC-DC Conversion
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Solution Overview
Problem
Conventional AC-DC converters face inefficiencies and high switching losses when dealing with high AC input voltages above 400V, requiring semiconductor devices with high withstand voltages, which are scarce and costly, and complex multi-level circuits are cumbersome to implement effectively.
Innovation Solution
The AC-DC converter design connects multiple switching units in series, each comprising a semiconductor switching device, diode, and capacitor, allowing for low-withstand-voltage semiconductor devices to handle high voltages by dividing the load into independent potential units, and uses isolated DC-DC converters to manage voltage levels, with a control system for pulse width modulation and phase difference in switching timing to maintain balanced output voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If semiconductor devices with high withstand voltage are used to handle AC input voltages above 400V, then the converter can process high voltage, but the switching losses increase and device cost increases
Solution Approach 1:
The patent divides the high-voltage handling function into multiple switching units connected in series. Each unit uses low-withstand-voltage semiconductor devices (e.g., 100V class) that can operate at high switching frequencies with low losses. The series connection of multiple units achieves the required high voltage capability while maintaining low switching losses in each individual device.
2Stress or pressure
If semiconductor devices with high withstand voltage are used, then high voltage can be handled, but device availability decreases and cost increases
Solution Approach 1:
The patent segments the voltage handling requirement across multiple switching units, each using commercially abundant low-voltage semiconductor devices. This approach leverages the availability and cost-effectiveness of standard low-voltage devices while achieving high-voltage operation through series connection of multiple units.
3Stress or pressure
If multi-level circuits are used to handle high voltages, then voltage handling capability improves, but circuit complexity increases
Solution Approach 1:
The patent employs segmented switching units with standardized configurations (switching device, diode, capacitor per unit). This modular segmentation achieves high-voltage capability while maintaining relatively simple and repeatable circuit structures, avoiding the complexity of traditional multi-level circuits.
Solution Approach 2:
The patent changes the operational parameters of the semiconductor devices by operating multiple low-voltage devices in series, effectively achieving high-voltage operation without requiring high-voltage rated components. This parameter change approach simplifies device selection and circuit design.
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, enables efficient high-voltage input handling with lower-cost semiconductor devices, and simplifies the circuit design while achieving performance comparable to multi-level circuits, resulting in a more efficient, smaller, and cost-effective AC-DC converter.
Implementation Method 1
When the AC input voltage Vin has positive polarity and the switching device 7 in FIG. 10 is turned on, the voltage Vr2 becomes 0V and the current flows in the following path: AC power source 1→diode 2→inductor 6→switching device 7→diode 5→AC power source 1. As a result of this, the voltage Vin is applied to both ends of the inductor 6, and the current IL increases.
Implementation Method 2
9 is a capacitor; and 10 is a load. The portion constituted by the inductor 6, the switching device 7, the diode 8, and the capacitor 9 is also known as a so-called boost converter, which boosts a DC voltage to increase output.
Data Source
AI summary
An AC to DC converter is provided with: a rectifier circuit that rectifies an AC voltage generated by an AC voltage source; and a plurality of switching units that collectively receive an output voltage of the rectifier circuit through an inductor, and that are connected in series at an input side, each of the switching units having a semiconductor switching device, a diode, and a capacitor, and performing ON/OFF switching of the semiconductor switching device provided therein to step up a voltage received from the rectifier circuit, each of the switching units supplying the stepped-up voltage to the capacitor through the diode so that a resulting DC across the capacitor can be provided, as a DC output voltage of the switching unit, to a respective load to be connected to terminals of the capacitor.