Bridgeless PFC Circuit Common-Mode Interference Reduction
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Solution Overview
Problem
The bridgeless boost PFC circuit experiences high common-mode interference and electromagnetic interference (EMI) due to the reduced number of conducting diodes, leading to increased power loss and efficiency issues.
Innovation Solution
An AC-to-DC conversion apparatus is designed with a bridgeless PFC circuit incorporating a first switch-element, output capacitor, and a bridge circuit formed by series-connected switch-elements, which reduces common-mode interference by controlling the switching of MOSFETs and diodes to minimize power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of conducting diodes is reduced in the bridgeless boost PFC circuit, then conduction loss is lowered and efficiency is increased, but common-mode interference and EMI become more serious
Solution Approach 1:
The circuit is divided into two separate boost PFC circuits with opposite powers, each handling one half-cycle of the AC input. This segmentation allows independent optimization of each circuit path, reducing the number of conducting elements in each path while maintaining overall functionality and reducing common-mode interference through balanced operation.
Solution Approach 2:
A neutral point connection is introduced as an intermediary element between the two boost circuits. This neutral point serves as a reference that balances the common-mode voltages, effectively canceling out the common-mode interference generated by the reduced number of conducting diodes while maintaining the efficiency benefits of the bridgeless topology.
2Loss of energy
If the number of conducting diodes is reduced in the bridgeless boost PFC circuit, then conduction loss is lowered and efficiency is increased, but EMI issues become more outstanding
Solution Approach 1:
The circuit is divided into two separate boost PFC circuits with opposite powers, each handling one half-cycle of the AC input. This segmentation allows independent optimization of each circuit path, reducing the number of conducting elements in each path while maintaining overall functionality and reducing common-mode interference through balanced operation.
Solution Approach 2:
The patent converts the potential harm of reduced diode conduction (which causes EMI) into a benefit by introducing the neutral point connection. This neutral point creates a balanced reference that transforms the unbalanced common-mode voltages into a balanced system, where the EMI-generating asymmetry is converted into a symmetrical operation that cancels out EMI.
3Loss of energy
If diodes D1 and D2 are cut off, then conduction loss is reduced, but leakage current increases due to parasitic capacitor Crss
Solution Approach 1:
The neutral point connection acts as an intermediary that provides a controlled path for displacement current through the parasitic capacitors. Instead of allowing uncontrolled leakage current when diodes are cut off, the neutral point creates a balanced capacitive coupling that channels the displacement current through a defined path, converting harmful leakage into useful reactive power compensation.
Data Source
AI summary
An AC-to-DC conversion apparatus is provided, and which includes a first switch-element, an output capacitor and a bridgeless power-factor-correction (PFC) circuit. The bridgeless PFC circuit is coupled to an AC input, and includes a first inductor, a second inductor and a bridge circuit constructed by second to fifth switch-elements. The first switch-element is connected between bridgeless PFC circuit and the output capacitor. Under such circuit configuration and suitable control manner, the common-mode interference in the provided AC-to-DC conversion apparatus is lowered and thus reducing the power loss.