Mains Power Converter With Gated Rectification For EMI Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solutions for converting AC mains power to low DC output voltage, such as using high-voltage capacitive dividers, switched mode DC-DC converters, and linear voltage regulators, are inefficient, expensive, and generate Electromagnetic Interference (EMI) due to the challenges of controlling duty cycles and isolating EMI sources.
Innovation Solution
A power converter design that includes a gated rectification stage and a switched mode DC-DC power conversion stage, where the DC-DC conversion occurs only during the high-voltage part of the AC mains cycle, using a capacitor to store intermediate voltage and a controller to manage switches, thereby isolating EMI sources without the need for inline filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a switched mode DC-DC converter is used to convert high voltage to low voltage, then conversion efficiency is improved, but EMI is generated and device complexity increases
Solution Approach 1:
The patent applies periodic action by enabling the DC-DC converter only during specific intervals (when the AC voltage exceeds a threshold) and disabling it during other intervals. This periodic operation allows the system to achieve efficient conversion when needed while periodically isolating the EMI source from the mains input, thereby resolving the contradiction between conversion efficiency and EMI generation.
2Power
If a DC-DC converter operates at low duty cycles to convert high voltage to low voltage, then voltage conversion is achieved, but control difficulty increases
Solution Approach 1:
The patent applies dynamics by making the duty cycle variable rather than fixed. The converter operates at high duty cycle when AC voltage is high and automatically reduces duty cycle when AC voltage drops below the threshold. This dynamic adjustment simplifies control by allowing the system to operate in a more favorable regime most of the time, avoiding the challenges of sustained low duty cycle operation.
3Ease of manufacture
If a linear voltage regulator is used to down-convert mains voltage, then device cost is reduced, but energy efficiency deteriorates
Solution Approach 1:
The patent combines a linear regulator with periodic action by enabling the regulator only when AC voltage is below a threshold and using a DC-DC converter when voltage is high. This hybrid approach allows the system to use the cost-effective linear regulator for low-voltage conditions while switching to the efficient DC-DC converter for high-voltage conditions, thereby resolving the contradiction between device cost and energy efficiency.
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 approach effectively isolates EMI sources, reduces the need for costly EMI filters, and achieves efficient conversion with high harmonic quality, suitable for applications requiring low DC output voltages like 3.3V, 5V, or 12V, while maintaining high efficiency and reducing the size and cost of the power converter.
Implementation Method 1
a capacitor configured to store charge at a voltage range which is intermediate the peak voltage and the DC output voltage
Implementation Method 2
a rectifier for rectifying an AC mains power
Data Source
AI summary
A power converter, configured to convert AC mains power to a DC output voltage which is lower than the AC mains' peak voltage, is disclosed. It comprises: a capacitor configured to store charge at a voltage range which is intermediate the peak voltage and the DC output voltage; a gated rectification stage comprising a rectifier for rectifying an AC mains power, and at least one switch configured to supply the rectified AC mains power to the capacitor during only a low-voltage part of a half-cycle of the AC mains; and a switched mode DC-DC power conversion stage comprising at least one further switch and configured to convert power from the capacitor to the DC output voltage during only a high-voltage part of the half-cycle. A controller for use in such a converter, and a corresponding method, are also disclosed.