Equalization Circuit Research Articles

A Low-Complexity Hybrid Readout Circuit for Lidar Receiver

This brief presents a low-complexity hybrid readout architecture that can extract both timing and amplitude information of the return pulse concurrently for a light detection and ranging radar (Lidar) receiver. To reconstruct the short return pulse, the core circuit of one sampling and storage array with an embedded time-to-digital converter (SSA-TDC) is proposed. Instead of relying on the conventional power-hungry high-speed ADC, it selectively samples the interested return pulse with high speed and stores the voltages for later quantization in the long idle interval. In the preceding stage of the SSA-TDC, the analog front-end circuit cascaded of a narrow-bandwidth transimpedance amplifier, a voltage amplifier, and an equalizer circuit is included. The prototype chip of the eight readout channels is designed and fabricated with the 0.18- $\mu \text{m}$ CMOS process. The active circuit occupies an area of $1200\,\,\mu \text{m}\,\,\times 2100\,\,\mu \text{m}$ , and the power consumption of one single channel is 45 mW with 3.3-V supply. The proposed SSA-TDC has achieved a dynamic error of 180 ps in the experimental study.

Double-Layer E-Structure Equalization Circuit for Series Connected Battery Strings

In order to eliminate the voltage imbalance among battery cells when they are connected in series, the paper proposes a double-layer E-structure (DLE) equalizer based on bidirectional buck–boost converters, which has the advantage of quick equalization speed and can be applied to arbitrary number batteries. Furthermore, a novel two-stage equalization control strategy is proposed for the DLE equalizer to decrease maximum voltage gap between the maximum and minimum voltage cells. The paper analyses the working principle of proposed equalizer in detail and describes the detailed design of the control strategy and implement process. Simulation and experiment results show that the proposed equalizer can improve equalization performance of battery cells compared with adjacent cell-to-cell (AC2C) equalizer.

Design of Lithium Battery Equalization Circuit for Energy Multipath Transmission

Design of Lithium Battery Equalization Circuit for Energy Multipath Transmission

Active Battery Equalization Method Based on Redundant Battery for Electric Vehicles

In this paper, an active equalization method based on redundant battery is proposed. A redundant battery is added to a battery pack consisting of several series batteries. According to the capacity and SOC (state-of-charge) of series batteries in the battery pack, one of these batteries is in parallel with the redundant battery in a certain time period. On the one hand, the energy is transferred between the redundant battery and the equalized batteries. On the other hand, during the charging or discharging process, the redundant battery acts as a power source, which reduces the current of the equalized battery. By adjusting the length of time that redundant battery and series batteries are connected in parallel, the purpose of battery equalization will be achieved. The balance current is limited only by the maximum charge–discharge ratio of the batteries. As long as the sum of the difference of series batteries capacity is less than the redundant battery capacity, the balance of all batteries can be achieved. Compared with other active equalization methods, the energy storage element (redundant battery) is used to be the main component of the equalization circuit in this method. It not only has the advantages of simple equalization circuit and large equalization current, but also has higher energy density of battery pack. In this paper, the equalization circuit is given, and the equalization strategy with accurate battery parameters and uncertain battery parameters is proposed. The experimental results also verify the correctness of the theoretical analysis and modeling.

Zero Current Switching Switched-Capacitors Balancing Circuit for Energy Storage Cell Equalization and Its Associated Hybrid Circuit with Classical Buck-Boost

To overcome the problem of switching loss during the balancing process, a novel cell balancing circuit is proposed with the integration of a zero current switching technique. Moreover, the balancing circuit proposed can change between a classical buck-boost pattern and a resonant switched-capacitor pattern with flexible control to cater to the balancing requirements under different driving scenarios. The results of the simulation of field experiments demonstrate successful balancing, various balancing speed, and low energy loss. The proposed balancing circuit proves to be effective for a wide range of application and is the first attempt to integrate a dual balancing function in a single balancing circuit for cells.

Control Strategy for Active Hierarchical Equalization Circuits of Series Battery Packs

Most series battery active equalization circuits implement the equalization first within the series and then between the series, which restricts the equilibrium speed. A hierarchical equalization circuit topology based on the Buck-Boost module is applied in this paper. The equalization is divided into two different equalization processes according to the equilibrium energy flow. The two equalization processes can be performed simultaneously, and the currents in the different hierarchical circuits do not affect each other, thus achieving simultaneous equalizations within the series and between the series. An equalization condition of the terminal voltage is applied and simulations and experiments on charge, discharge, and static equalizations in the four series-connected ternary lithium-ion batteries are performed.

A Novel Li-ion Battery Equalizer Circuit Design Based on LC Resonant Tank

A novel Li-ion battery string equalizer based on LC resonant tank is designed. The circuit includes switched control module, LC resonant tank and voltage peak detecting module. By detecting the voltage peak position of the capacitor in the LC resonant tank, the equalizer circuit successfully switches batteries near the zero-current point to improve the equalization efficiency. The equalizer circuit is verified by Matlab/Simulink simulation and experiment. The simulation and experimental results shows that the proposed circuit can be applied for battery equalization.

A Series Resonant Energy Storage Cell Voltage Balancing Circuit

A novel cell voltage equalizer using a series LC resonant converter is proposed for series-connected energy storage devices, namely, battery or super (or ultra)-capacitor cells. The proposed circuit is an active voltage equalization circuit for energy storage devices that is low cost, small in size, and equalizes the voltages quickly. Compared to the state-of-the-art solutions, the proposed series LC resonant circuit eliminates the complexity of multiwinding transformers, and it can balance series-connected energy storage devices in a short time by transporting energy successively between the cells having highest voltage difference. The detailed circuit operation and theoretical analysis are provided. Simulation and experimental results are presented to demonstrate the voltage equalization process from an initial voltage difference of 527 mV to a final difference of 10 mV in 900 s for three series-connected supercapacitor cells.

Charge-Based Self-Equalization for Imbalance Battery Pack in an Energy Storage Management System: Developing a Time-Based Equalization Algorithm

A variation in batteries' physical or chemical specifications right from the manufacturing process causes a slight difference in battery capacity in a battery pack. The imperfection resulting from the production causes the imbalance state of charge (SoC) level that will eventually start to become significant over long-term operation and lead to irreversible damage to the whole battery pack earlier than the expected battery life cycle. To solve the cell imbalance issue and maximize the usable battery pack capacity, an active cell self-equalization algorithm based on the estimated SoC with 24 lithium-ion batteries connected in series was developed. A bidirectional flyback converter equalizer circuit topology was implemented, allowing the charge transfer from cell to pack and from pack to cell. The results prove that the algorithm is applicable for real-time equalization on an imbalanced battery pack in energy storage management systems (ESMSs).

A novel dual loop adaptive equalizer based on spectrum balancing technique

Inductorless circuits are gaining advantage in RF and high-speed serial link circuits due to the reduced silicon area. This paper presents an inductor-less adaptive equalizer featuring both data rate adaptation and channel loss adaptation. The conventional adaptive equalizers use spectrum balancing technique. The spectrum balancing technique balances the power in low and high frequency components with cutoff frequency of the filters as 0.28Tb (Tb is the minimum bit period of the incoming data stream). The proposed technique removes the necessity of using high pass filter and uses only a programmable low-pass filter in the adaptive equalization loop. This technique leads to the tunability of the equalizer over a wide range of throughput and channel losses. For the proof of concept, the entire equalizer circuit is designed and fabricated in 180 nm mixed mode CMOS technology. The measurements with lossy channels show that the proposed adaptive equalizer is able to work well for the channel losses up to 6 dB and wide throughput of 1–3.125 Gbps. The design is targeted to operate at a maximum data rate of 3.125 Gbps to meet JESD 204 standards. The proposed adaptive equalizer consumes a power of 9.8 mW/Gbps including IO buffers.

Switch Matrix Algorithm for Series Lithium Battery Pack Equilibrium Based on Derived Acceleration Information Gauss-Seidel

With the rapid development of energy internet and new energy-related industries, lithium-ion batteries are widely used in various fields due to their superior energy storage characteristics. To reduce the influence of the inconsistency of the individual cells in the battery pack, a switch array DC equalization circuit together with an acceleration information Gauss-Seidel (DAIGS) method is proposed. The aging factor is added in the system state matrix considering the battery time effect. In this method, the energy transfer path can be optimized by updating the switch control matrix in each iteration. Hence, it can avoid the repeated charging and discharging of the battery and also reduce energy loss in rapid equalization. A four-cell battery string equalization model simulation was built in the PSIM and the experiment was also carried out to prove the feasibility of the proposed method. It was verified that the DAIGS had better performance under the same precision or number of iterations.

An active battery equalization scheme for Lithium iron phosphate batteries

A battery-equalization scheme is proposed to improve the inconsistency of series-connected lithium iron phosphate batteries. Considering battery characteristics, the segmented hybrid control strategy based on cell voltage and state of charge (SOC) is proposed in this paper. The simulation model of equalization circuit with bidirectional fly-back transformer are established. Furthermore, a comparison is made with the proposed hybrid control strategy. The simulation results show that the proposed hybrid control strategy is more capable of effectively enhancing the consistency of batteries.

Ultra-Short-Reach Interconnects for Die-to-Die Links: Global Bandwidth Demands in Microcosm

To meet the ever-increasing demand of global data traffic, the Hybrid Memory Cube (HMC) specification and High-Bandwidth Memory standard call for an aggregate bandwidth of 8 Tb/s in next-generation memory-to-processor links [1], [2]. At the same time, the data rates processed by individual line cards in data center switches will soon go beyond 25 Tb/s [3]. However, as the data rate of serial links over copper interconnects increases, the links appear highly lossy. Further, the power consumption of a wireline transceiver, including all clocking and equalization circuits, increases. Publications suggest a tenfold increase in power consumption with a 30-dB increase in channel loss [4]. Hence, energyefficient communication equipment should be engineered to keep the channel loss as low as possible.

Bidirectional Multi‐Input and Multi‐Output Energy Equalization Circuit for the Li‐Ion Battery String Based on the Game Theory

Energy inconsistency among Li‐ion battery cells widely exists in energy storage systems, which contributes to the continuous deterioration of the system durability and overall performance. Researchers have proposed various kinds of battery energy equalizers to reduce such inconsistency. Among them, the inductor equalizer is a predominant type in fast equalization applications. However, it requires relatively more complex control than other types of equalizers. In order to reduce the control complexity of inductor equalizers, a bidirectional multi‐input and multi‐output energy equalization circuit based on the game theory is proposed in the present work. The proposed equalizer has the modularized circuit topology and the mutually independent working principle. A static game model is developed and exploited for the mathematical description and control analysis of an energy equalization circuit comprised of these equalizers. The feasible control of each equalizer was obtained by solving a series of linear equations for the Nash Equilibrium of the model among the states of charge of the battery cells. The complexity of equations grows linearly with the cell number. The equivalent simulation model for the four‐cell equalization is established in the PISM software, where the operational data and simulation results justify the static game model and verify the control validation, respectively. It is concluded that the proposed inductor equalizer is suitable for large‐scale battery strings in energy storage systems, electrical vehicles, and new energy power generation applications.

Design of Large Connectors of Overhead Power Lines

It is found that the voltage at the lowest points of the wire or cable sag and at the points of their suspension on the pillars in the same span, determined in accordance with the properties of a perfectly flexible filament (similar to which the wires and cables are located in the span), differ slightly, and taking the difference of the mentioned values into account is only of methodologycal importance. The article presents the results of the calculation of wire and cable sag of large spans of power transmission line of 500 m or more length using both the traditional theory of the catenary line and the theory of equal resistance, when the cross-sectional area of a wire or cable, proportional to their tension, is considered variable in the span length, which provides the same probability of breaking them at any point of the span. When calculating the wires and cables in normal and emergency conditions, the largest sags are determined, which take place either at a higher ambient temperature or at a load of the wire with ice. The wire must be mounted in such a way as to ensure the normalized permissible dimensions to crossed engineering structures, water barriers or land, that are determined depending on the nominal voltage of the line. It is noted that the values of the wire and cable sags determined using the theory of the catenary line for the transition spans are less (although slightly) as compared to the data obtained on the basis of the theory of the equal resistance circuit. This must be taken into account in the design process.

Optimization of the two-stage common-emitter transistor amplifier for equalization circuit in visible light communication system

The equalization circuit in the visible light communication (VLC) system has large impacts on the frequency response and can greatly improve the 3-dB modulation bandwidth. The optimization of the two-stage common-emitter transistor amplifier for equalization circuit is presented in detail and the design rules are disclosed. At first, the frequency response of the single-stage amplifier is derived and the simulated characteristic curves illustrated the changing regularity of four main factors are given. Subsequently, the frequency response of the two-stage amplifier is investigated by simulation. It is shown that the capacitors in the resistance–capacitance (RC) network has large impacts on the low-frequency range, while the resistors in the RC network can adjust the high-frequency, and the resistors in the emitter can adjust the low-frequency. Experimental measurements of the fabricated equalization circuit demonstrated the simulation results. Then, the two-stage amplifier is induced as post-equalization circuit (post-EQC) or pre-equalization circuit (pre-EQC) and the measured frequency response curves are given. The equalization circuit with proper sets of capacitors and resistors would flatten the frequency response curve of the VLC system. It is shown that the 3-dB modulation bandwidth of the VLC system equipped with post-EQC or pre-EQC can be expanded to 292 MHz or 304 MHz, respectively. Moreover, if the photoelectric receiver and the post-EQC are combined in the optimization, the 3-dB modulation bandwidth can be expanded to 375 MHz.

Equalization of Lithium-Ion Battery Pack Based on Fuzzy Logic Control in Electric Vehicle

A nondissipative equalization scheme based on fuzzy logic control (FLC) is presented to improve the inconsistency of series-connected Lithium-ion batteries. The two-stage bidirectional equalization circuit with energy transferring inductors is designed to implement the equalization of cell to cell for battery packs, and the equalization circuit paves the way for module-based equalization of hardware. Equalization based on the state of charge (SOC) is proposed in this paper, and the Thevenin equivalent circuit model of the Lithium-ion battery, as well as the extended Kalman filter (EKF) algorithm, is employed for SOC estimation. For effective equalization, the FLC is proposed to reduce energy consumption and equalization time. The FLC strategy is constructed with a set of membership functions to describe the equalization behavior of the cell. A comparison of the proposed FLC with the mean-difference algorithm is carried out to validate the advantages of the proposed scheme. Simulation results show that the standard deviation of final SOC reduces by ${\text{18}}{\text{.5}}\%$ , and equalization time decreases by ${\text{23}}\%$ for FLC compared with the mean-difference algorithm under new European driving cycle working conditions. The energy efficiency improves by ${\text{5}}{\text{.54}}\%$ compared with the mean-difference algorithm. In addition, the two-stage bidirectional equalization circuit has good performance and improves the inconsistency.

Modular battery charge equalization circuit based on state of charge for electric vehicle application

Electric Vehicle (EV)/Hybrid Electric Vehicle (HEV) enabled by high-efficiency electric motor and controller, provide the means for a clean, efficient and environmental friendly transportation system. Portable rechargeable batteries are the essential basic component in EVs. In EV/HEV system a large number of cells should be connected in series to supply enough energy, while the voltage balancing problem between cells leads to poor performance. This paper attempts modular battery charge equalization based on state of charge (SOC) under MATLAB Simulink environment.

A Voltage Equalizer Circuit to Reduce Partial Shading Effect in Photovoltaic String

Partial shading is one of the main causes in reducing the output power of photovoltaic (PV) systems. This paper proposes a circuit to recover the energy of shaded PV modules during partial shading condition (PSC). The proposed circuit, which is a combination of a buck–boost converter and the switched-capacitor (BBSC) circuits, equalizes the voltage of PV modules and prevents bypass diodes from bypassing the shaded modules in a string. Hence, shaded PV modules can have a contribution in output generated power instead of being bypassed. The main features of the BBSC are the utilization of the reduced number of switches in comparison with buck–boost and switched-capacitor circuits, a simple switching control strategy, and fast voltage equalization. In addition, a BBSC circuit is almost a lossless circuit during uniform shading conditions. To validate the effectiveness of the proposed BBSC circuit, both simulation results in PSCAD/EMTDC software and experimental results are presented.

Modified voltage equaliser based on Cockcroft–Walton voltage multipliers for series‐connected supercapacitors

It is essential for electric vehicle to equalise the voltages of battery or supercapacitor (SC) cells in series connection. Comparing with other equalisation methods based on energy transfer, Cockcroft–Walton (CW) voltage multiplier brings great benefits to the simplification of equalisation structure. Voltage equaliser formed by voltage multiplier can realise voltage balance automatically without voltage detection and control unit. However, the traditional (CW) voltage multiplier structure has two demerits. One is incapable of realising the voltage balancing for all the cells in series; the other one is the large inrush current of parallel capacitors that reduces the lifetime of the equaliser. To solve these problems, a modified voltage equalisation circuit is proposed. The new equaliser is constituted by a half-bridge frontend and a multiplier backend. The half-bridge generates the alternating voltage, and the multiplier accomplishes the voltage balancing. The operation principles, circuit analysis and parameters calculation are examined in detail. The performance is evaluated by simulation and experimental with three SCs in series. The accordance between simulation and experiment further proves that the voltage balancing is achieved for all the series cells and the inrush current of capacitors is declined at the turning on of power switches.