【電磁技術(shù)在線】【EMC篇】- 2. DCDC轉(zhuǎn)換

講師：Waldemar Schulz

00：00 模型介紹

01：20 電路介紹

03：15 demo：PCB導(dǎo)入，監(jiān)視器，combine result，新建電路任務(wù)

20：30 傳到發(fā)射結(jié)果分析，修改PCB

In modern electronic applications a majority of devicesutilizes switched AC/DC or DC/DC converters in their power networks. The powerprovided from a source, is switched by the converter in order to adjust theoutput voltage level (Switch Mode Power Supply - SMPS).

Unfortunately the switching always creates noise, which may be significant at higher frequencies. Furthermore, this unwanted emissioncan upset the source or any other device in the same supply power network, because it is easily transmitted through the power lines.

The main goal of the workflow, is to calculate the overall level of the conducted emission and to design filters to suppress it. With simulation, this can be performed before a prototype of the device is manufactured.

CST allows to import an EDA layout and perform a forementioned studies. The subject of this workflow is a bulk step-down DC/DC converter designed for the automotive industry.

In this application， the converter is reducing an input DC voltage from 12V to the 5V. Taking into account the operational frequency ofthe converter (488 kHz) and values of all lumped elements inside the switching loop, the duty cycle of the signal which controls the switch on/off state, should be 48.7%. Therefore the switch should be closed (in on – state) for 1us(0.487*T), and opened (in off – state) for 1.05us (0.513*T).

T – time period:T=1/488kHz = 2.05us

A “boost loop” for increasing the switching efficiency of the converter, is created with help from Schottky diode (D2) and capacitor (C2). The SPICE models were imported for both diodes. Decoupling is provided by capacitors (C5, C7). The device is connected to the source thru LISN (Line Impedance Stabilization Network).