Resonant Converter Choke Balancing for Common-Mode EMI Suppression
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Solution Overview
Problem
Existing resonant converters suffer from common mode noise emissions and volume, and efficiency, and the presence of parasitic capacitances cause significant common mode conducted emissions at the input terminal of the DC-link, leading to increased volume, cost, and reduced efficiency and EMI performance.
Innovation Solution
A resonant converter with a DC common mode choke and a resonant tank, including equal inductances and capacitances, and a shielding connection structure to reduce noise emission and volume, and increase power density and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If period doubling modulation is used in LCL-T resonant converter, then wide gain range operation is achieved, but common mode conducted emissions increase significantly
Solution Approach 1:
The patent utilizes the parasitic capacitances that cause common mode emissions by introducing a DC common mode choke with capacitive components that resonate at the switching frequency. This converts the harmful parasitic capacitances into beneficial resonant elements that cancel out the common mode currents, transforming the harmful effect into a solution.
Solution Approach 2:
The DC common mode choke acts as an intermediary element between the resonant tank and the input terminal. It provides a path for common mode currents to circulate and cancel out, preventing them from propagating to the input terminal and causing emissions.
2Object-generated harmful factors
If bulky LC filters are added at the front end to reduce emissions, then EMI performance improves, but volume increases and efficiency decreases
Solution Approach 1:
The patent extracts and utilizes the parasitic capacitances that were previously causing problems, incorporating them into the resonant circuit design. By making these parasitic elements functional components, additional filtering components are eliminated, reducing overall volume.
Solution Approach 2:
The DC common mode choke serves multiple functions: it provides common mode filtering to reduce emissions, maintains the resonant frequency of the circuit, and enables full range zero voltage switching. This multi-functionality eliminates the need for separate bulky filter components.
3Object-generated harmful factors
If DC common mode choke with capacitive components is introduced, then common mode emissions are reduced, but device complexity increases
Solution Approach 1:
The patent merges the DC common mode choke with the existing resonant tank circuit, combining multiple functions into a single integrated structure. The capacitive components of the choke are integrated with the resonant capacitors, reducing the total number of discrete components.
Solution Approach 2:
The parasitic capacitances of the existing components serve the dual purpose of their original function and as the capacitive elements of the DC common mode choke. This self-service approach eliminates the need for additional dedicated components.
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
The resonant converter effectively reduces noise emission, volume, and increases power density and efficiency by balancing inductances and capacitances, and decoupling the rectifier circuit from the resonant tank, resulting in zero common mode current propagation.
Implementation Method 1
The resonant converter includes a DC common mode choke and a resonant tank... A balancing condition is met when a first ratio between two inductances of the DC common mode choke and the first resonant inductor and a second ratio between capacitances of the at least two capacitive components are equal.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A resonant converter (1, 1a, 1b) is provided. The resonant converter (1, 1a, 1b) includes a DC common mode choke (3) and a resonant tank (4, 4a). The DC common mode choke (3) includes two capacitive components (Cp1, Cp2, Cp3, Cp4, Cp5, Cp6). The resonant inductor group (41) includes a first resonant inductor (411) and a second resonant inductor (412). The first resonant inductor (411) and the second resonant inductor (412) are equal. Two sides of the resonant capacitor group (42) are connected with the first resonant inductor (411) and the second resonant inductor (412), respectively. The resonant capacitor group (42) includes two resonant capacitors (C4) in series. A balancing condition is met when a first ratio between two inductances of the DC common mode choke (3) and the first resonant inductor (411) and a second ratio between capacitances of the two capacitive components (Cp1, Cp2, Cp3, Cp4, Cp5, Cp6) are equal.