Kang-Rong Li

Evaluation of conducted EMI measurement without LISN using two-port ABCD network approach for EMI filter design under real operating condition

To demonstrate the impact of the line impedance stabilization network (LISN) on conducted electromagnetic interference (EMI) measurement, an in-circuit impedance extraction method based on inductive coupling approach is developed to extract the common mode (CM) and the differential mode (DM) noise impedances of AC mains, LISN, and switched-mode power supply (SMPS) under operating condition. By treating two inductive coupling probes and the device-under-test (DUT) for impedance extraction as three cascaded two-port ABCD networks, the CM and DM noise impedances can be extracted with ease. The extracted CM/DM noise impedance of AC mains is compared with the extracted SMPS and LISN CM/DM noise impedances, respectively. By analyzing the impedance comparisons, the impact of LISN on conducted EMI measurement for EMI filter design under real operating condition is evaluated. Finally, the evaluation is validated with the conducted EMI currents measured with and without LISN.

Estimation of deviation of conducted emission measurement without LISN

Common mode (CM) and differential mode (DM) conducted emissions without the line impedance stabilization network (LISN) is investigated from the perspective of CM and DM impedances. Using a switched-mode power supply (SMPS) as an equipment under test (EUT), the in-circuit CM and DM impedances of the actual measurement setup with and without LISN are extracted so that the deviation of conducted emission measurement without LISN from that of with LISN can be revealed and demonstrated.

Impact Analysis of Conducted Emission Measurement Without LISN

Common-mode (CM) and differential-mode (DM) conducted emissions without the line impedance stabilization network (LISN) is investigated. Using a switched-mode power supply (SMPS) as an equipment under test (EUT), the in-circuit CM and DM impedances of the actual measurement setup with and without LISN are extracted so that the impact on conducted emission measurement without LISN can be better understood.

Study of EMI filter performance without LISN based on noise impedances

The performance of the electromagnetic interference (EMI) filter under the condition without the Une impedance stabilization network (LISN) are revealed and analyzed from the perspective of the common mode (CM) and differential mode (DM) impedances of the switched-mode power supply (SMPS), AC mains, and LISN. The in-circuit CM and DM impedances of the SMPS, AC mains, and LISN are extracted with an inductive coupling approach based on the theory of the two-port ABCD network and the EMI filter is designed according to the extracted CM and DM impedances. By installing the designed EMI filter on the SMPS and measuring the conducted emissions with and without LISN, the performance of the EMI filter operating under the actual condition without LISN is revealed.

In-circuit common-mode impedance measurement for motor drive system

Optimized common-mode (CM) filter design requires accurate knowledge of both the noise source and the termination impedances. In this paper, an in-circuit impedance extraction method is employed to determine CM impedance of a motor drive system. The CM impedance extracted allows systematic CM filter design without a trial-and-error approach.

On-line impedance monitoring of transformer based on inductive coupling approach

An on-line impedance monitoring method of a transformer is proposed based on two-probe inductive coupling approach. The theory behind the method is described and validated experimentally. As it does not require direct electrical contact with the transformer powered by high voltage power supply, it can be easily installed on site and most importantly, it eliminates the potential electrical hazards imposed on the personnel who set up the measurement instrumentation.

Improved two-probe approach for in-circuit measurement based on three-port network pre-calibration

In high-speed electrical designs, the in-circuit characteristics of the components are usually obtained from in-circuit measurements as the references for designers. The two-probe approach (TPA) is one of in-circuit measurement approaches by adopting the inductive coupling effects of the current probes, and it gains good accuracy below 30MHz. In this paper, we propose an improved two-probe approach (ITPA) by introducing network parameters. Rather than modeling the measurement setup using equivalent circuits in the TPA, the proposed ITPA models it by using a three-port network, and pre-calibrates it before real measurements. By comparing the results measured from ITPA with those from the impedance analyzer (IA), it is proven that, the ITPA extends the highest measurement frequency to 100MHz from 30MHz (with the TPA), while maintaining allowable accuracy; besides, the ITPA avoids the trial-error pre-calibrations required in the TPA.

EMI filter design to improve electromagnetic immunity of hearing aid devices

Electromagnetic interference (EMI) from mobile phones on hearing aids are investigated. Different operating modes of the hearing aid have different impact on the immunity of the device. An experimental study will be carried out to understand the impact of EMI filter on the compliance of the hearing aid under the operating modes.