Radiated EMI study on super‐junction VDMOS in flyback power converters

Abstract

Electronic products must satisfy radiated noise specifications. In this paper, the impact of the power devices structures on the radiated electromagnetic interference (EMI) is investigated. The key stages of turn-on and turn-off waveforms in a flyback power converter using super-junction metal-oxide semiconductor fieldeffect transistor (SJMOS) are first discussed. Then, the impacts of parasitic capacitances on fast slew-rate edges and harmonics are proposed. According to the analysis, the parasitic capacitances are considered to be the decisive factors of radiated EMI in the SJMOS. Furthermore, the unique formation mechanism and characteristic of parasitic capacitances in SJMOS are discussed. Based on the analysis, three groups of SJMOS with grid gate structure are fabricated to adjust the parasitic capacitance and then to validate the theory. The radiated EMI performances of three SJMOS with different structural parameters are then tested and discussed. The theoretical analysis agrees with experimental results. As an important advantage, the structure presented in this paper is provided to adjust the parasitic capacitances purposely to achieve a better tradeoff between the efficiency and EMI performance. relevant capacitors. The waveforms of falling and rising edges are illustrated in Figure 11. With a larger W G and a smaller t OX , the decreasing of edge slope is clearly observed.The experimental setup is shown in Figure 12. A Langer RF-R 400-1 near-field probe associated with a 30-dB active amplifier and an Agilent 4395A spectrum analyzer are adopted to test the radiated EMI performance of these SJMOS. The EUT is fixed on the testing table, and the near-field probe is set 2 cm above the EUT. The spectrum analyzer is set at Maxhold mode. Both 5 and 30-W flyback converters are adopted for test. The near-field radiated EMI test results are shown in Figure 13. Changes on device structures reflect dramatic differences on radiated EMI. Device 2 with the largest C ISS and C GS shows the best radiated EMI performance among these three devices. Above 5-dB differences on EMI testing results can be observed between 2 and 3. The testing results agree well with the theoretical analysis. The efficiency test result is shown in Table II. Less than 0.3% decrease of efficiency can be observed between 2 and 3. Although the decrease of efficiency is inevitable, the results are acceptable for a low-power converter. Figure 12. Experimental setup. [Colour figure can be viewed at wileyonlinelibrary.com] RADIATED EMI STUDY ON SJMOS 1323the analysis, a new grid gate structure is presented. Three groups of grid gate SJMOS are fabricated to validate the theory. The theoretical analysis agrees with experimental results. More than 5-dB suppression is noticeably achieved. As an important advantage, the structure presented in this paper is provided to adjust the parasitic capacitances purposely to achieve a better tradeoff between the efficiency and EMI performance. RADIATED EMI STUDY ON SJMOS 1325

A highly accurate and robust source reconstruction method of printed circuit boards based on complex‐valued neural network

“…The study of equivalent models resorting to simpler structures with similar EMI characteristics to the original model is of great importance in analysis of radiation properties of PCBs working in microwave frequency band. [2][3][4][5] As shown in Figure 1, an equivalent dipole model of a PCB can be constructed by using effective source reconstruction methods (SRMs) likes Tikhonov regularization method (TRM). Then, the equivalent model can be adopted to replace the original PCB in the system-level electromagnetic compatibility (EMC) problem, as illustrated in Figure 2.…”

“…Due to the complexity of practical PCBs, direct and detailed modeling of their electrical properties and intricate structure is cumbersome or unrealistic to even attempt. The study of equivalent models resorting to simpler structures with similar EMI characteristics to the original model is of great importance in analysis of radiation properties of PCBs working in microwave frequency band 2–5 . As shown in Figure 1, an equivalent dipole model of a PCB can be constructed by using effective source reconstruction methods (SRMs) likes Tikhonov regularization method (TRM).…”