Modeling and Reduction of Radiated Common Mode Current in Flyback Converters

Yao, Juntao; Li, Yiming; Zhao, Hui; Wang, Shuo; Wang, Qinghai; Lu, Yuliang; Fu, Dianbo

doi:10.1109/ecce.2018.8557687

Cited by 31 publications

(10 citation statements)

References 14 publications

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“…S 21 can not only be measured but also be simulated by FEM simulation tool. Hence, this paper will base on the previous effort [21]- [23] and use FEM full-wave simulation tool to simulate the EMI characteristic of the transformer. Then, the equivalent capacitance C x between power switch and the ground is measured by the proposed method.…”

Section: Evaluation Methods a Traditional Evaluation Methodsmentioning

confidence: 99%

Evaluation Method of Flyback Converter Behaviors on Common-Mode Noise

Chen

2019

IEEE Access

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Common-mode (CM) conduction electromagnetic interference (EMI) is a challenge for switched-mode power supply (SMPS) designers. A flyback converter is a traditional topology used in low-power isolated applications. The size and cost of EMI filters are important considerations for higher power density and lower cost of SMPS design. In most cases, the CM current is generated by voltage pulsation (dv/dt) assigned on the primary winding and the secondary winding. The CM current conduction paths can be mainly categorized into two categories. One is the interwinding parasitic capacitance of the transformer, and the other is the parasitic capacitance between the semiconductor switches and the protective ground. This paper proposed an evaluation method to measure the equivalent CM noise capacitance of the two main CM current conduction paths, respectively. Then, this paper proposed a CM noise cancellation scheme based on the transformer winding design combining the measurement technique and the FEM simulation tool. Planar transformers with PCB windings also have advantages in low profile, good heat dissipation, and good stray parameter consistency. Based on these considerations, an 18-W adapter is designed and tested to verify the effectiveness of the proposed evaluation method and the design scheme. INDEX TERMS Common-mode (CM), flyback, EMI, planar transformer, equivalent capacitance.

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Section: Evaluation Methods a Traditional Evaluation Methodsmentioning

confidence: 99%

Evaluation Method of Flyback Converter Behaviors on Common-Mode Noise

Chen

2019

IEEE Access

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“…Many previous references also have discussed the issue on how to evaluate the CM noise behavior of the transformer [17][18][19][20]. Figure 5a,b depicts the traditional transformer CM characteristic evaluation method.…”

Section: Previous Evaluation Methodsmentioning

confidence: 99%

“…h is the height of the core window. According to (19) and (20), the dynamic CM capacitance CQ can be calculated as…”

Section: Selection Of Resistor Rmentioning

confidence: 99%

“…Therefore, the potential difference between the primary ground and the secondary ground can be omitted when the isolated converter has three wires. In this kind of circuit configuration, the resistance chosen for R2 should be as small as possible, According to (19) and (20), the dynamic CM capacitance C Q can be calculated as…”

Section: Ground Potential Differencementioning

confidence: 99%

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A General Transformer Evaluation Method for Common-Mode Noise Behavior

Chen

Lin

2019

Energies

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In isolated power converters, the transformer is a key part of voltage transformation and isolation. Since common-mode (CM) noise is rather difficult to suppress compared with different-mode (DM) noise, more and more scholars are paying attention to the characteristics of CM noise, especially in high-frequency CM noise behaviors. CM noise can be further divided into conducted CM noise and radiated CM noise, and the main focus of this paper is on conducted CM noise. The CM coupling capacitance of the transformer is one of the main contributors of CM noise, which has been verified in many previous studies. Hence, eliminating the CM noise in a transformer coupling path can significantly lower the whole CM noise level of the converter. Professional conducted electromagnetic interference (EMI) testing instruments are quite expensive. In this paper, a general transformer evaluation technique for CM noise behavior is proposed. Only a signal generator and oscilloscope can achieve transformer CM noise behavior evaluation. PCB planar flyback transformers are designed, and a series of noise spectrums and voltage waveforms can verify the effectiveness of the proposed transformer evaluation method. The flyback adapter porotype can pass the EMI standard limited line EN55022 class B by the proposed evaluation method.

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“…Higher frequency yields more complex impedance and voltage distributions [24]. Hence, the linear voltage distribution assumption in the analysis method is valid only up to several megahertz for transformers used in power converters [25,26]. For another, leakage inductances also resonate with inter-layer capacitances, so CM paths will show resonant peaks and transform from capacitive to inductive [27].…”

Section: Evaluation Of Noise Reduction Effectsmentioning

confidence: 99%

Quantitative analysis of common‐mode current in flyback converter with balance winding

Zhang

2022

IET Power Electronics

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The balance winding of the transformer is a compact and flexible technique for the common-mode (CM) noise reduction of isolated power converters. A proper design of the grounding and turn number of the balance winding will generate an inverse displacement current to balance the CM noise flowing through the transformer. However, a trial and error process to find the optimum design is necessary for practical applications due to the unexplored source of calculation errors. In this paper, a quantitative analysis method of CM currents flowing through all the paths between windings is proposed for error quantifications. Based on an interleaved transformer, the capacitances are extracted with the help of electric field simulations, and the contribution of each path to the CM noise is analysed. Although the paths between adjacent layers are dominant in the CM noise, it is proved that ignoring non-adjacent inter-layer paths will lead to calculation errors due to the high voltage difference even with low capacitances. As both the application and verification of the proposed quantitative analysis method, the accurate evaluation of noise reduction effects and determination of the optimum balance winding turns can be achieved in experiments.

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Modeling and Reduction of Radiated Common Mode Current in Flyback Converters

Cited by 31 publications

References 14 publications

Evaluation Method of Flyback Converter Behaviors on Common-Mode Noise

Evaluation Method of Flyback Converter Behaviors on Common-Mode Noise

A General Transformer Evaluation Method for Common-Mode Noise Behavior

Quantitative analysis of common‐mode current in flyback converter with balance winding

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