Assessing the effectiveness of different test approaches for power devices in a PCB

Power electronic systems employing Printed Circuit Boards (PCBs) are broadly used in many applications, including some safety-critical ones. Several standards (e.g., ISO26262 for the automotive sector and DO-178 for avionics) mandate the adoption of effective test procedures for all electronic systems. However, the metrics to be used to compute the effectiveness of the adopted test procedures are not so clearly defined for power devices and systems. In the last years, some commercial fault simulation tools (e.g., DefectSim by Mentor Graphics and TestMAX by Synopsys) for analog circuits have been introduced, together with some new fault models. With these new tools, systematic analog fault simulation finally became practically feasible. The aim of this paper is twofold: first, we propose a method to extend the usage of the new analog fault models to power devices, thus allowing to compute a Fault Coverage figure for a given test. Secondly, we adopt the method on a case study, for which we quantitatively evaluate the effectiveness of some test procedures commonly used at the PCB level for the detection of faults inside power devices. A typical Power Supply Unit (PSU) used in industrial products, including power transistors and power diodes, is considered. The analysis of the gathered results shows that using the new method we can identify the main points of strength / weakness of the different test solutions in a quantitative and deterministic manner, and pinpoint the faults escaping to each one

Multilevel Simulation Methodology for FMECA Study Applied to a Complex Cyber-Physical System

Complex systems are composed of numerous interconnected subsystems, each designed to perform specific functions. The different subsystems use many technological items that work together, as for the case of cyber-physical systems. Typically, a cyber-physical system is composed of different mechanical actuators driven by electrical power devices and monitored by sensors. Several approaches are available for designing and validating complex systems, and among them, behavioral-level modeling is becoming one of the most popular. When such cyber-physical systems are employed in mission- or safety-critical applications, it is mandatory to understand the impacts of faults on them and how failures in subsystems can propagate through the overall system. In this paper, we propose a methodology for supporting the failure mode, effects, and criticality analysis (FMECA) aimed at identifying the critical faults and assessing their effects on the overall system. The end goal is to analyze how a fault affecting a single subsystem possibly propagates through the whole cyber-physical system, considering also the embedded software and the mechanical elements. In particular, our approach allows the analysis of the propagation through the whole system (working at high level) of a fault injected at low level. This paper provides a solution to automate the FMECA process (until now mainly performed manually) for complex cyber-physical systems. It improves the failure classification effectiveness: considering our test case, it reduced the number of critical faults from 10 to 6. The remaining four faults are mitigated by the cyber-physical system architecture. The proposed approach has been tested on a real cyber-physical system in charge of driving a three-phase motor for industrial compressors, showing its feasibility and effectiveness

Test Solution for Heatsinks in Power Electronics Applications

Power electronics technology is widely used in several areas, such as in the railways, automotive, electric vehicles, and renewable energy sectors. Some of these applications are safety critical, e.g., in the automotive domain. The heat produced by power devices must be eciently dissipated to allow them to work within their operational thermal limits. Moreover, numerous ageing eects are due to thermal stress, which causes mechanical issues. Therefore, the reliability of a circuit depends on its dissipation system, even if it consists of a simple passive heatsink mounted on the power device. During the Printed Circuit Board (PCB) production, an incorrect assembly of the heatsink can cause a worse heat dissipation with a significant increase of the junction temperatures (Tj). In this paper, three possible test strategies are compared for testing the correct assembling of heatsinks. The considered strategies are used at the PCB end-manufacturing. The eectiveness of the dierent test methods considered is assessed on a case study corresponding to a Power Supply Unit (PSU)