A comparison and accuracy analysis of impedance-based temperature estimation methods for Li-ion batteries

In order to guarantee safe and proper use of Lithium-ion batteries during operation, an accurate estimate of the battery temperature is of paramount importance. Electrochemical Impedance Spectroscopy (EIS) can be used to estimate the battery temperature and several EIS-based temperature estimation methods have been proposed in the literature. In this paper, we argue that all existing EIS-based methods implicitly distinguish two steps: experiment design and parameter estimation. The former step consists of choosing the excitation frequency and the latter step consists of estimating the battery temperature based on the measured impedance resulting from the chosen excitation. By distinguishing these steps and by performing Monte-Carlo simulations, all existing methods are compared in terms of accuracy (i.e., mean-square error) of the temperature estimate. The results of the comparison show that, due to different choices in the two steps, significant differences in accuracy of the estimate exist. More importantly, by jointly selecting the parameters of the experiment-design and parameter-estimation step, a more-accurate temperature estimate can be obtained. In case of an unknown State-of-Charge, this novel method estimates the temperature with an average absolute bias of 0.4. °C and an average standard deviation of 0.7. °C using a single impedance measurement for the battery under consideration

Integration trends in monolithic power ICs: Application and technology challenges

\u3cp\u3eThis paper highlights the general trend towards further monolithic integration in power applications by enabling power management and interfacing solutions in advanced CMOS nodes. The need to combine high-density digital circuits, power-management circuits, and robust interfaces in a single technology platform requires the development of additional process options on top of baseline CMOS. Examples include high-voltage devices, devices to enable area-efficient ESD protection, and integrated capacitors and inductors with high quality factors. The use of bipolar devices in these technologies for protection and control purposes in power applications is also addressed.\u3c/p\u3

State-of-the-art of integrated switching power converters

This paper discusses the state-of-the-art of integrated switched-capacitor and inductive power converters. After introducing applications that drive the need for integrated switching power converters, implementation issues to be addressed for integrated switched-capacitor and inductive converters are given, as well as design examples. At the end of the paper, various integrated power converters are compared in terms of the main specifications

Switched-capacitor power-converter topology overview and performance comparison

Switched-capacitor power converters are interesting candidates to realize integrated power converters with acceptable power efficiencies. Depending on the input and output voltage ranges to be accommodated at a desired efficiency, certain voltage conversion ratio(s) need(s) to be implemented. Though the theoretical minimum number of floating capacitors to realize a desired voltage conversion ratio is known, how to actually synthesize the corresponding topologies and what impact these topologies have on circuit performance is less trivial. Besides two-clock-phase topologies, multiple-clock-phase topologies have recently been introduced. This paper gives an overview of various methods to implement desired voltage conversion ratios with two or multiple clock phases and compares their performance under given boundary conditions

On trade-offs between computational complexity and accuracy of electrochemistry-based battery models

In this paper, we propose several simplifications to the so-called Doyle-Fuller-Newman (DFN) model, which is a popular electrochemistry-based battery model. This simplified DFN (SDFN) model allows for a computationally very efficient implementation. The simplifications are a result of several assumptions, which will be justified for two different parameter sets. Finally, the SDFN model proposed is compared to the DFN model as well as an implementation of the single-particle model, for the two parameter sets. This will show that by making specific assumptions, simplifications can be made that have no significant impact on the model accuracy, while the computation time can be drastically decreased. This leads to a simulation time of over 3600 times faster than real-time

Range maximisation of electric vehicles through active cell balancing using reachability analysis

Due to internal differences between cells inside a battery pack, active cell balancing during discharging potentially leads to an extension of the range of electric vehicles. This paper poses range maximisation of electric vehicles as a reachability problem. It is solved by converting this reachability problem into a feasibility problem for a given range. This leads to a large-scale nonlinear feasibility/optimisation problem, which we propose to solve using sequential linearisation of the dynamics and a dual decomposition. This method provides the necessary balancing currents to extend and maximise the range of the vehicle, if the drive cycle, and the model parameters and states are completely known. This result shows the maximum potential for range maximisation through active balancing and can serve as a benchmark for evaluating controllers which are applicable in real-time

Apparatus and method for determination of the state-of-charge of a battery when the battery is not in equilibrium

The invention relates to a method and an apparatus, like a charger for determining the state-of-charge of a battery which has been charged or discharged and which has not reached its equilibrium state, the method comprising the steps of determining the EMF of the battery by extrapolation of the battery voltage sampled during relaxation after the charge or the discharge process, wherein the extrapolation is based on a model using only variables sampled during the relaxation process and deriving the state-of-charge from the EMF of the battery by using a predetermined relation between the EMF and the state-of- charge. This method is a voltage-prediction method without the need to store parameters beforehand.; Instead, the voltage relaxation end value is determined based on the measured first part of a voltage relaxation curve and mathematical optimisation/fitting of a function to this measured part of the relaxation curve

An inductive down converter system-in-package for integrated power management in battery-powered applications

With the increasing number of voltage conversions that have to be efficiently implemented in a mobile device, the PCB space occupied by switched-mode DC-DC converters with external passive components will become unacceptably high. Therefore, a clear need exists for small-form-factor high-efficiency DC-DC converters having the necessary passive components integrated within one package. This will enable the integration of a DC-DC converter with the load and consequently the system integration of power management. This paper describes the measurement results of an integrated inductive down converter, where the active electronics (power stage and driver circuitry) has been implemented in 0.18-mum CMOS technology and the passive components (output LC filter and decoupling capacitor) have been implemented in a state- of-the-art proprietary passive-integration process technology using high-density trench-MOS capacitors (80 nF/mm2 ) and an 8-mum thick copper top metallization layer. The active die of the converter has been flip-chipped on top of the passive die to reduce parasitic component values. This yields a System-in-Package (SiP) that achieves a step-down DC-DC conversion without any external components. Due to the limited inductance achievable with the used planar air coil in the acceptable area, the switching frequency of the DC-DC converter has been increased. At the same time, Zero-Voltage-Switching (ZVS) measures have been implemented to reduce the switching losses at this increased frequency. A maximum efficiency of 65% at 80 MHz has been achieved for an input voltage of 1.8 V, an output voltage of 1.1 V and an output current of 100 mA. After explaining the motivation behind integrated power management and the choice for an integrated inductive converter, this paper describes the main design aspects of the realized integrated inductive DC-DC down converter. Next, it presents some details of the used passive-integration process, the design of the passi- - ve die including the LC filter and the construction of the SiP. Finally, the measurement results of the converter are discussed and conclusions are drawn

Apparatus and method for chip-scale package with capacitors as bumps

A method and apparatus relating to chip-scale packaging is provided. According to an embodiment of the invention electrical solder bump interconnection between an integrated circuit package and a substrate is replaced by the placement and attachment of discrete SMD components between pads on the integrated circuit and substrate. Said substrate being for example a low-temperature co-fired ceramic such as alumina or a PCB such as FR4. Accordingly discrete SMD capacitors, inductors etc can be packaged with the system design goals of minimizing board real-estate, enhancing performance, and cost addressed in a novel manner without requiring substantial development of new processes by manufacturers. The embodiments of the invention minimizing the parasitic series impedance of decoupling capacitor connections for example whilst allowing a small-form-factor System-in-Package to be realized

Method and apparatus for determination of the state-of -charge (soc) of a rechargeable battery

The present invention relates toa method for determination of the state-of- charge (SoC) of a rechargeable battery as a function of the Electro-Motive Force (EMF) prevailing in said battery. The invention also relates to a method for measuring the relation between the state-of-charge (SoC) and the EMF. The invention further relates to an apparatus for determination of the State-of-Charge (SoC) of a rechargeable battery as a function of the Electro-Motive Force (EMF) prevailing in said battery