Simulating the EMI characteristics of flyback DC/DC converters

In this article, the influence of diode reverse recovery on EMI performance of a low power flyback converter is investigated. Two different diode models (SPICE and SABER®) are analyzed and the conducted emissions from a simulated converter with a thorough characterization of the parasitic elements are compared to measurements. It is concluded that the emission levels to a large extent is determined by the mutual couplings within the input filter. The proposed simulation model predicts EMI levels up to 20MHz with good accuracy. Furthermore, it is concluded that the diode reverse recovery is reflected into the conducted emissions. For the investigated case, a recovery peak of IRR=2.8A gives an increase in emission levels with 3dB around 10MHz compared to a diode with IRR=1.0A. Finally, it was found that Schottky diodes may decrease the EMI performance of the converter; the large inherent capacitance can cause large oscillations in the circuit that are reflected into the conducted emissions.

[1]  S. Wong,et al.  SPICE macro model for the simulation of zener diode I-V characteristics , 1991, IEEE Circuits and Devices Magazine.

[2]  S. Basu,et al.  Diode recovery characteristics considerations for optimizing EMI performance of continuous mode PFC converters , 2005, 2005 European Conference on Power Electronics and Applications.

[3]  T. Thiringer,et al.  MOSFET modeling adapted for switched applications using a state-space approach and internal capacitance characterization , 2009, 2009 International Conference on Power Electronics and Drive Systems (PEDS).

[4]  V. Tarateeraseth,et al.  The Comparison of EMI and Electrical Performances of High Frequency Transformer Windings for SMPS Applications , 2007, 2007 Power Conversion Conference - Nagoya.

[5]  Hosein Farzanehfard,et al.  Conducted EMI modeling and reduction in a flyback switched mode power supply , 2011, 2011 2nd Power Electronics, Drive Systems and Technologies Conference.

[6]  P. Lauritzen,et al.  A simple power diode model with forward and reverse recovery , 1991 .

[7]  Jinjun Liu,et al.  An improved method of parameter abstraction for a novel diode reverse recovery model in time-domain simulation , 2008, 2008 Twenty-Third Annual IEEE Applied Power Electronics Conference and Exposition.

[8]  H.A. Mantooth,et al.  A unified diode model for circuit simulation , 1995, Proceedings of PESC '95 - Power Electronics Specialist Conference.

[9]  H. Farzanefard,et al.  EMI evaluation in hard switching and soft switching PWM flyback converters , 2010, 2010 1st Power Electronic & Drive Systems & Technologies Conference (PEDSTC).

[10]  H. Farzanefard,et al.  Precise prediction of conducted EMI in PWM flyback converters , 2010, 2010 18th Iranian Conference on Electrical Engineering.

[11]  K. J. Tseng,et al.  Modified charge-control equation for more realistic simulation of power diode characteristics , 1997, Proceedings of Power Conversion Conference - PCC '97.