Reliability Analysis of Capacitors in Voltage Regulator Modules With Consecutive Load Transients

Abstract

Capacitors are critical in voltage regulator modules (VRMs) which contribute to store energy and stabilize the output voltage during load transients. Usually, VRMs work with consecutive load transients, which would bring more electrothermal stress to capacitors and affect the reliability of capacitors compared with the steady-state operation. Recently, some efforts have been made to investigate the reliability of capacitors in power electronic converters. Unfortunately, transient processes are commonly ignored, which can impair the accuracy of the lifetime estimation. Regarding this issue, this paper investigates the influence of transients on the damage of capacitors in VRMs. A 150 W VRM is introduced as a case study. Firstly, the electrothermal stresses during steady state and transients are analyzed.Then, the lifetime calculation is considered from a single capacitor to hybrid capacitor banks. In addition, a suitable capacitor configuration of capacitor banks is also provided, in order to maximize its lifetime.

Real-Life Mission Profile-Oriented Lifetime Estimation of a SiC Interleaved Bidirectional HV DC/DC Converter for Electric Vehicle Drivetrains

“…The DC-link capacitor is responsible for the root cause of 19% of all failures. On the one hand, the electrolytic DC-link capacitor's cost-effectiveness and simplicity make it a preferable choice for the PECs developers [21]. On the other hand, the electrolytic DC-link capacitor can give rise to ageing issues.…”

“…The potential cause of electrolytic DC-link capacitor ageing is the uneven electro-thermal reaction and/or electrolytic evaporation. These ageing factors are accelerated due to excessive electro-thermal stresses on the capacitor [21], [22]. The electro-thermal stresses can be increased due to high ripple current and DC-link voltage variation.…”

Reliability Improvement of Voltage Regulator Modules by a Virtual Series Voltage Source

“…Considering the current distribution of individual capacitor in capacitor banks, the rms current of the k-th capacitor is [27] C,rms, C,rms…”

“…Fig. 14(a) shows the typical thermal model of capacitors, where T h and T a represent the hotspot temperature and ambient temperature, respectively [27]. R ha and τ ha are the total equivalent thermal resistance and thermal time constant from T h to T a , respectively.…”

“…Because of the sampling frequency of mission profiles in traditional schemes is usually smaller than 1 Hz (the sampling rate is 1 hour in [17]), which easily results in missing important transient information. Although Zhao et al investigated the reliability of capacitors in VRMs [27], in which transient stresses have been considered. However, there is a lack of research efforts focusing on the converter-level reliability evaluation of VRMs with frequent loading transients.…”