Integrated EMI/thermal design for switching power supplies

Abstract

This work presents the modeling and analysis of EMI and thermal performance for switch power supply by using the CAD tools. The methodology and design guidelines are developed.By using a boost PFC circuit as an example, an equivalent circuit model is built for EMI noise prediction and analysis. The parasitic elements of circuit layout and components are extracted analytically or by using CAD tools. Based on the model, circuit layout and magnetic component design are modified to minimize circuit EMI. EMI filter can be designed at an early stage without prototype implementation.In the second part, thermal analyses are conducted for the circuit by using the software Flotherm, which includes the mechanism of conduction, convection and radiation. Thermal models are built for the components. Thermal performance of the circuit and the temperature profile of components are predicted. Improved thermal management and winding arrangement are investigated to reduce temperature.In the third part, several circuit layouts and inductor design examples are checked from both the EMI and thermal point of view. Insightful information is obtained. Background and MotivationIn recent years, many of the design issues of a power supply have been intensively addressed. Issues such as power stage topology, control modeling, performance analysis, soft-switching topologies, and magnetic component optimization.However, two major issues, EMI control and thermal management have been far from adequately addressed. Cut and trial method is normally used to solve these problems. Switch-mode power supplies generate high frequency noises because of their switching action. In the continuous effort to increase converter power density, switching frequency is becoming higher which, in general, makes EMI performance worse. The generated noises from the power stage may cause malfunction of control circuitry within the converter itself, as well as electromagnetic compatibility (EMC) problems to the surrounding equipment. EMI noises need to be controlled and minimized. A variety of EMC standards regulates conducted and radiated emission and have become more stringent in recent years.The failure probability of electronic components depends primarily on the operating temperature. According to statistics of the U.S. military department, thermal overstressing is the cause for most of the failures in modern electronic systems [25]. To ensure proper operation, the maximum allowable temperature is usually determined for Introduction 2 the semiconductor device and magnetic components. In the continuous effort to decrease the volume of power converters, the switching frequency is becoming higher, and the power density of converters is higher. The increasing use of surface-mount technology, avoidance of fans to reduce noise and volume, and reduced package dimensions all intensify the thermal design requirement.At the present time, the design practice in power supply industry is that both EMI and thermal requirements are tested at the final hardware implement...

Theoretical and experimental investigation of the fast- and slow-scale instabilities of a DC-DC converter

“…For the averaged model, determination of the stability of the period-one solution can be done using the loop gain of the voltage loop [30]. The loop gain of the closed-loop buck converter can be determined using (34) where modulator gain; feedback sensor gain; control to the output transfer function; as shown in (35) at the bottom of the page, and is the controller transfer function. The phase margin of determines the stability of the closed-loop system.…”

Thermal Modelling and Design of On-board DC-DC Power Converter using Finite Element Method

“…Therefore it is necessary to make some model simplifications. One method can be used when thermal conductivity of the winding block is estimated as equivalent [13], [14]. Each conductor is defined as a heat source inserted within the block.…”

EMI conduzida gerada por conversores estáticos aplicados à correção do fator de potência

“…No caso do conversor boost PFC, o ruído CM está diretamente relacionado a uma única capacitância parasita, conforme mostraram (Zhang, 1998), (Zhang et al, 2000), (Hertz, 2001) e (Zientarski et al, 2009). Trata-se da capacitância parasita que se estabelece entre a trilha do dreno (no caso do MOS-FET) ou no coletor (no caso do IGBT) do interruptor principal e o terra.…”