This paper is concerned with reliability analysis in relation to optimal switching of resonant power converters, aimed at minimizing their power loss and operational temperature and thus reducing their lifetime degradation. In most cases, high performance resonant converter control requires a continuous adaptation of the power device switching instances depending on the power input source, load current, or parameter variation in passive components. If the resonant converter is switched before or after the resonant swing ends, more loss is added to the system, with effects in operating temperature rise and reliability deterioration. Even if the switching frequency is adjusted to keep the output voltage constant, it may influence the operational temperature. This article is quantifying this problem with a calculation of the lifetime implication for both cases of Zero Voltage Transition (ZVT) and Zero Current Transition (ZCT) buck converters. A broad range of parameter variation in passive components is considered due to ageing or aggravated stress. A thorough performance (lifetime / reliability) evaluation is achieved through a comparative analysis of results obtained for resonant converters with ideal operation, resonant converters with adjusted timing due to parameter variation, and hard-switched converters without any resonance. Conclusions are formulated in the end. The results reported in the paper should be of high interests to the power electronics community, given that resonant converters are used in a wide range of applications due to their ability to reduce power semiconductor losses.

Point-of-Load (PoL) DC-DC Converters are based on buck converter topology which is actuated at a switching frequency. The value of the switching frequency determines the performance of the power converter, including its reliability. This paper quantifies the influence of switching frequency on reliability and lifetime, in addition to efficiency, thermal response, and ripple. The analysis is conducted for a wide range of switching frequency variation (50 kHz to 500 kHz) and a conventional synchronous converter with discrete Si MOSFETs. The failure rate and reliability calculation follow a modern prediction standard, herein was adopted IEC-TR-62380 due to the concept of mission profile that it uses. The reliability calculation is based on the temperature of the device when the converter is working on a common load. A thermal scanning of the power converter provides this temperature under two different loads (mild and strong) is herein achieved with infrared photography.

Many recent studies have revealed that PoL (Point of Load) converters’ output capacitors are a paramount component from a reliability point of view. To receive the maximum degree of reliability in many applications, designers are often advised to derate this capacitor—as such, a careful comprehending of it is required to determine the converter’s overall parameters. PoL converters are commonly found in many electronic systems. Their most important requirements are a stable output voltage with load current variation, good temperature stability, low output ripple voltage, and high efficiency and reliability. If the electronic system in question must be portable, a small footprint and volume are also important considerations—both of which have recently been well accomplished in eGaN transistor technologies. This paper provides details on how derating an output capacitor—specifically, a conductive tantalum polymer surface-mount chip, as this type of capacitor represented a step forward in miniaturization and reliability over previously existing wet electrolytic capacitors—used within a discrete eGaN-FET-based PoL buck converter determines the best performance and the highest MTBF. A setup based on an EPC eGaN FET transistor enclosed in a 9059/30 V evaluation board with a 12 V input voltage/1.2 V output voltage was tested in order to achieve the study’s main scope. Typical electrical performance and reliability data are often provided for customers by manufacturers through technical papers; this kind of public data is often selected to show the capacitors in a favorable light—still, they provide much useful information. In this paper, the capacitor derating process was presented to give a basic overview of the reliability performance characteristics of tantalum polymer capacitor when used within a DC–DC buck converter’s output filter. Performing calculations of the capacitor’s failure rate based on taking a thermal scan of the capacitor’s capsule surface temperature, the behavior of the PoL converter was evaluated.

Simulation techniques implemented with the HFSS program were used for structure optimization from the point of view of increasing the conductivity of the batteries’ electrolytes. Our analysis was focused on reliable “beyond lithium-ion” batteries, using single-ion conducting polymer electrolytes, in a gel variant. Their conductivity can be increased by tuning and correlating the internal parameters of the structure. Materials in the battery system were modeled at the nanoscale with HFSS: electrodes–electrolyte–moving ions. Some new materials reported in the literature were studied, like poly(ethylene glycol) dimethacrylate-x-styrene sulfonate (PEGDMA-SS) or PU-TFMSI for the electrolyte; p-dopable polytriphenyl amine for cathodes in Na-ion batteries or sulfur cathodes in Mg-ion or Al-ion batteries. The coarse-grained molecular dynamics model combined with the atomistic model were both considered for structural simulation at the molecular level. Issues like interaction forces at the nanoscopic scale, charge carrier mobility, conductivity in the cell, and energy density of the electrodes were implied in the analysis. The results were compared to the reported experimental data, to confirm the method and for error analysis. For the real structures of gel polymer electrolytes, this method can indicate that their conductivity increases up to 15%, and even up to 26% in the resonant cases, via parameter correlation. The tuning and control of material properties becomes a problem of structure optimization, solved with non-invasive simulation methods, in agreement with the experiment.

The last decade’s studies show that the PoL (point-of-load) converter’s output capacitor is an important component for reliability, implying that its careful selection may determine the overall converter’s failure rate and lifetime. PoL converters are commonly found in many electronic systems, usually as part of the Intermediate Bus Architecture (IBA). Their important requirements are a stable output voltage at load current variation, good temperature stability, a low output ripple voltage, high efficiency, and reliability. If the electronic system is portable, a small footprint and low volume are also important considerations. These were recently well accomplished with eGaN (enhancement gallium nitride) transistor technology, whose VUFoM (vertical unipolar figure of merit) is 1.48 compared to 1.00 for silicon. This ensures a higher converter power density (watts/area). This paper reviews the most-used capacitor technologies, highlighting the reliability of these components as part of the converter’s output filter by presenting original data related to their best performance. The test was set up with EPC’s eGaN FET transistor, which was enclosed within a 9059/30 V evaluation board with a 12 V input and 1.2 V output. Different output capacitor technologies were evaluated, and reliability was calculated based on measurements of the ripple of the output voltage and thermal scanning.

This paper analyzes the reliability calculation method and elaborates on lifetime implications for an external computer power supply unit. Calculation is performed following MIL-HDBK-217 specifications for reliability of each individual module and the paper can be seen as an example for using this method. Design of the power supply is constrained due to requirements for safety of consumer products, and this somewhat influences the lifetime and reliability aspects. This paper provides a clear perspective on contribution of protection circuits to total reliability. The output capacitor bank yields as the most critical component and options for reliability improvement are next discussed. The effect of voltage derating and the effect of capacitor technology improvement are quantified through calculation of the system reliability and lifetime. Bringing into discussion real numerical values for failure rates, this paper helps knowledge development in the upcoming field of reliability of power converters.