Waveform and Spectral Characteristics of Supraharmonic Unsymmetrical Conducted EMI of Switched-Mode Power Supplies
Abstract
:1. Introduction
2. Selected SMPSs and Measurement Setup
2.1. SMPS Operation and Characteristics
2.2. Setup for Time- and Frequency-Domain Measurements
- Either to an 8-bit DSO with a sampling rate of 10 MSa/s (ensuring that the target frequency interval of 2–150 kHz could be achieved in terms of the sampling time and record length);
- Or to an EMI receiver with a peak detector, followed by max hold and dwell time ranging between 1 and 200 ms.
- A 50 Ω impedance-matching barrel Rm to implement the mentioned 50 Ω loading of the capacitive branch of the LISN;
- An anti-aliasing low-pass filter R1C1, which was designed starting from a maximum frequency of 1 MHz (positioning its cutoff frequency one octave above at 2 MHz, which was very compatible with the said sampling frequency of 10 MHz) and exploiting the input capacitance of the DSO channel (found to be quite accurate and stable at 15 pF), thus resulting in a resistive value R1 = 1.5 kΩ (negligible in terms of the voltage drop in series to the 1 MΩ input resistance of the DSO);
- A high-pass filter C2R2 that further attenuated the 50 Hz mains fundamental and its harmonics and designed around a resistive value large enough not to disturb the impedance matching and to remarkably influence the low-pass filter (set to 5 kΩ) and a resulting series capacitance C2 with a negligible reactance over the desired frequency interval. The use of a high-pass filter is supported by the suggested increase of the decoupling factor in [26] and confirmed by [27] for similar measurements.
3. Discussion of the Form of Data and Their Variability
3.1. Apparent Characteristics of Time-Domain Waveforms
3.2. Basic Post-Processing Methods for the Analysis of Spectral Characteristics
4. Unprocessed Reference Data
- Time-domain waveforms, where signal details in various operating conditions are shown to provide a first visual assessment of signal characteristics, also to better understand the behavior of the processed data; data were sampled at 10 MHz and low-pass filtered for anti-aliasing exigency at 2 MHz, ensuring they are fully valid up to 1 MHz.
- EMI receiver scans similarly extending up to 1 MHz and using an RBW value of 200 Hz, which is compatible with requirements of EMC standards for the 9–150 kHz interval; the adopted dwell time was 1 ms.
4.1. Time-Domain Waveforms
4.2. Frequency-Domain Spectra
- No-load emissions (green curve) could sometimes and for some frequency intervals be larger than curves for the other test conditions such that no load is an important operating condition to include in a test program; see, in particular, Figure 10a, where there was a consistent increase of about 10 dB above 20 kHz, with the appearance of many secondary components.
- The 25% condition, however, presented some secondary emissions that were not visible in the high-load condition, as evident in Figure 10e,f.
5. Conclusions
Supplementary Materials
Author Contributions
Funding
Conflicts of Interest
Appendix A
- Name of SMPS: BALANCE, BLACK, KARIO, KTEC, SHENZEN, WHITE;
- Load level: 0A (no load), P25 (25% of nominal load) and P90 (90% of nominal load).
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Acronym | SMPS | Vno-load (V) | I25%-load (A) | I90%-load (A) |
---|---|---|---|---|
LW | Lacie White (24 W) | 12.94 | 0.51 | 1.83 |
LB | Lacie Black (26.4 W) | 11.75 | 0.47 | 1.72 |
KT | KTEC (18 W) | 12.19 | 0.37 | 1.43 |
SH | Shenzhen Honor (18 W) | 12.45 | 0.38 | 1.45 |
BA | Balance (10 W) | 5.212 | 0.51 | 1.94 |
KA | Kario (10 W) | 5.144 | 0.51 | 1.91 |
Power | Switching Topology | Galvanic Isolation |
---|---|---|
Low | Buck (step-down) | No |
Low | Boost (step-up) | No |
Low | SEPIC (single-ended primary inductance converter) | No |
Low | Flyback | Yes |
High | Forward | Yes |
High | Push–pull | Yes |
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Sandrolini, L.; Mariscotti, A. Waveform and Spectral Characteristics of Supraharmonic Unsymmetrical Conducted EMI of Switched-Mode Power Supplies. Electronics 2022, 11, 591. https://doi.org/10.3390/electronics11040591
Sandrolini L, Mariscotti A. Waveform and Spectral Characteristics of Supraharmonic Unsymmetrical Conducted EMI of Switched-Mode Power Supplies. Electronics. 2022; 11(4):591. https://doi.org/10.3390/electronics11040591
Chicago/Turabian StyleSandrolini, Leonardo, and Andrea Mariscotti. 2022. "Waveform and Spectral Characteristics of Supraharmonic Unsymmetrical Conducted EMI of Switched-Mode Power Supplies" Electronics 11, no. 4: 591. https://doi.org/10.3390/electronics11040591
APA StyleSandrolini, L., & Mariscotti, A. (2022). Waveform and Spectral Characteristics of Supraharmonic Unsymmetrical Conducted EMI of Switched-Mode Power Supplies. Electronics, 11(4), 591. https://doi.org/10.3390/electronics11040591