Deniss Stepins

Measuring Capacitor Parameters Using Vector Network Analyzers

Vector network analyzer (VNA) is versatile measuring equipment which is primarily used for two-port device S parameters measurements. This paper addresses measurement of capacitor parameters using VNA in broad frequency range. The main attention is focused on the measurement accuracy of capacitors parameters using VNA and proper de-embedding of an experimental setup parasitics to get accurate results. Comparative measurement error analysis for different measurement techniques is presented. Suitability of each measurement technique for measurements of capacitor parameters using VNA is discussed and effect of the experimental setup parasitics on the measurement results is addressed. Moreover useful procedures for proper capacitor impedance measurement using VNA are developed.

Effects of increasing switching frequency in frequency modulated power converters

The paper considers the effect of increasing switching frequency on a frequency modulated (FM) buck converter parameters: efficiency, output voltage ripples and electromagnetic interference (EMI) attenuations. The converter operating in continuous and discontinuous conduction modes (CCM and DCM respectively) is analyzed analytically, by simulations in Simulink and experimentally. The results obtained show that increasing switching frequency can significantly reduce the ripples (especially in DCM) and improve effectiveness of the use of FM to reduce EMI. Impact of increasing the switching frequency on efficiency of FM converter is also studied. It is found out that FM does not affect efficiency within the broad range of switching frequencies. The analysis provides useful data to improve the effectiveness of the use of FM in switchmode converters.

Mutual couplings between EMI filter components

This paper deals with modeling of mutual couplings between passive EMI filter components: inductors and capacitors positioned on printed circuit board. 3D electromagnetic software CST MWS is used for the modeling. Three scenarios are considered: mutual couplings between two capacitors, mutual couplings between two inductors and mutual couplings between inductor and capacitor. Modeling results are verified experimentally using a vector network analyzer. Comparison of the measurement and modeling results shows that transfer coefficients and mutual inductance between two capacitors can be predicted accurately. However modeling of the mutual couplings between two inductors has the lowest accuracy.

Modeling of mutual coupling between inductors

This paper is devoted to EMI filter inductor modeling and mutual coupling modeling between two inductors positioned on PCB. 3D inductor models are developed and modeled in CST MWS. Comparison of inductors mutual coupling measurement and modeling results show that transfer coefficients can be predicted accurately. CST MWS has been used also to predict effective mutual coupling reduction techniques.

Analysis of output voltage of switching frequency modulated DC-DC converter operating in discontinuous conduction mode

In this paper analysis of output voltage ripples of a switching frequency modulated (SFM) buck converter operating in discontinuous conduction mode (DCM) is performed. The ripples are analyzed in both time and frequency domains by the use of theoretical derivations and computer simulations. Significant increase in output voltage ripples under DCM is observed after using periodic SFM. Low frequency variations at modulation frequency are considered as the most problematic. Cause of the problem is revealed. Influence of main nonidealities of the converter and modulation parameters on the output voltage ripples is analyzed. Experimental verification is also performed to confirm the theoretical evaluations and simulation results. The analysis can give useful information when designing a SFM power converter.

Differential mode Il-type EMI filter modeling using CST MWS

This paper deals with modeling of differential mode Il-type EMI power filter using 3D electromagnetic field modeling software CST MWS. Two scenarios are considered: inductor is positioned in parallel or perpendicular to capacitors. Capacitor distance and PCB track layout is changed to verify software modeling precision and capabilities. Measurement and modeling results are in good agreement.

Effect of frequency modulation on input current of switch-mode power converter

Comprehensive theoretical analysis of the effect of switching frequency modulation (SFM) on input current of DC/DC switch-mode power converters (SMPC) operating in discontinuous conduction mode (DCM) is presented. Theoretical and SIMULINK simulation results are verified experimentally. Peak input and power components currents increase and low-frequency harmonics appear in the input current due to the use of SFM. Some considerations on the right choice of modulation parameters to reduce the negative effects considering also output voltage ripples and electromagnetic interference attenuation are proposed. The analysis performed can be very useful for a design of DC/DC SMPC with SFM in DCM.

Analysis of switching frequency modulated synchronous buck converters

This paper is devoted to the analysis of the effect of switching frequency modulation (SFM) used for EMI reduction on the synchronous buck converters (SBC) parameters, such us output voltage ripples (OVR), peak power component currents, etc. In the paper SBC are studied analytically, using computer simulations and experimentally. The most careful attention is paid on the peak-to-peak OVR because it is the most problematic parameter due to the use of SFM. Several useful guidelines for the choice of SFM parameters and slight modification of the control circuit to get peak-to-peak OVR as small as possible are also proposed. The results presented in the paper can simplify the design of SBC with SFM.

Conducted EMI of Switching Frequency Modulated Boost Converter

Abstract In this paper conducted electromagnetic interference (EMI) of boost converter with switching frequency modulation (SFM) is theoretically analyzed in details. In the analysis line impedance stabilization network parameters, power inductor and input filtering capacitor parameters are taken into account. The analysis shows that the conducted EMI attenuation due to the use of SFM depends not only on modulation index as it is assumed in numerous research papers, but also on central switching frequency. Useful expressions to numerically calculate SFM boost converter conducted EMI spectrum and attenuation due to the use of triangular and sawtooth modulation waveforms are derived. Additionally experimental verification of the theoretical results is performed using a superheterodyne spectrum analyzer. Moreover a procedure for the choice of optimum SFM parameters (modulation waveform, frequency deviation and modulation frequency) to get maximum conducted EMI attenuation is proposed.

Improving effectiveness of the use of frequency modulation in power converters

In the research the examination of the methods possible to improve the implementation of spread spectrum technique for EMI reduction in switch mode power supplies are searched. The analysis of effects of switching frequency modulation in open loop boost converter reveals that there is additional undesirable amplitude modulation of the input current of the converter. This effect distorted the spectrum of the input current, thus worsening the EMI reduction, achieved by the use of the frequency modulation. Experimental results, using sinusoidal and sawtooth modulating signals, proved the theoretical assumption, asserting that the effectiveness of EMI attenuation and the reduction of spectral asymmetry could be achieved choosing as high as possible operating frequencies and proper modulating profiles.