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Summary: In this paper, a multiphase digital control called digital integration constant on‐time (DICOT) control is proposed, which applies the concept of signal accumulation, solves the drawbacks of ripple‐based digital COT control that the switching frequency and transient performance are affected by the A/D sample delay and sampling noise. Besides, the multiphase interleaving approach of the proposed DICOT control is well‐suitable for digital control and no higher calculation frequency is required compared to single‐phase. In the aspect of the current balance, almost all existing researches work on analog COT current balance scheme and few works are investigating the resolution improvement of digital COT current balance. In this paper, the current balance model of multiphase COT control is derived and can be applied in the Buck system with an arbitrary number of phases, the delay‐line‐based high‐resolution COT current balance scheme is proposed to enhance the control resolution. Finally, the two‐phase DICOT control is tested on the multiphase Buck system, the transient performance is tested of 100 A load step with the slew rate of 1000 A/μs, and the voltage undershoot and overshoot are 20 and 36 mV, respectively. The current balance is tested and the errors are 0.01% and 0.11% at the light and heavy loads, respectively. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to study a multi-level reinjection current source converter (MLR-CSC) that adds attracting properties such as the self-commutation and pulse multiplication to the thyristor converter, which is of great significance for increasing the device capacity and reducing current harmonics on the grid side. Particularly, designing advantageous driving methods of the reinjection circuit is a critical issue that impacts the harmonic reduction and operation reliability of the MLR-CSC. Design/methodology/approach: To deal with the mentioned issue, this paper takes the five-level reinjection current source converter (FLR-CSC), which is a type of the MLR-CSC, as the research object. Then, a method that can fully use combinations of five-level reinjection switching functions based on the concept of decomposition and recombination is proposed. It is worthy to mention that the proposed method can be easily extended to other multi-level reinjection circuits. Moreover, the working principle of the three-phase bridge circuit based on semi-controlled thyristors in the FLR-CSC that can achieve the four-quadrant power conversion is analyzed in detail. Findings: Finally, the simulation and experimental results of FLR-CSC verify the effectiveness of the proposed reinjection circuit driving method and the operating principle of four-quadrant power conversion in this paper. Originality/value: The outstanding features of the proposed driving method for FLR-CSC in this paper include combinations of reinjection switching functions that are fully exploited through three simple steps and can be conveniently extended to other multi-level reinjection circuits. [ABSTRACT FROM AUTHOR]

Summary: Multistring arrays of LED in parallel connection are widely applied in lighting fields. Active control and passive methods are utilized to guarantee equal current sharing between different strings with a common voltage source. Compared with active control, the passive methods that adopt purely passive components without real power dissipation are good candidates. Currently, an inductive power transfer (IPT) converter providing a constant voltage (CV) line, followed by some immittance networks that convert the CV line to constant current (CC) outputs, is commonly used to drive multiple LED strings. However, in such a two‐conversion‐stage scheme, the component count is as many as 3×N, where N is the number of LED strings, which deviates from compact, low‐cost, and simple design ideas. To address it, this paper aims to develop a single‐immittance‐network‐based IPT system to drive multistring LEDs with the current balance. The proposed IPT system can directly provide a CV to CC conversion to drive multistring LEDs with the benefits of simplifying the circuit design, size, and cost. The proposed IPT system also features programmable luminous power, zero‐phase‐angle (ZPA) input, IPT technology, and load‐independent‐current (LIC) output. Detailed analysis, implementation, and experiment are presented in this paper. [ABSTRACT FROM AUTHOR]

High step‐up boost converters with large input current capacity are necessary for low‐voltage renewable energy sources, such as photovoltaic panels and fuel cells. Interleaved converters are a suitable topology for low‐voltage, large input current applications. Conventional interleaved converters, however, face a variety of challenges, such as the necessity of additional current control loops for active current balancing, increased voltage stress of semiconductors, and poor extendibility. In this paper, highly extendable interleaved high step‐up boost converters with a passive current balancing and reduced semiconductor voltage stresses are proposed. Current capacities and step‐up conversion ratios of the proposed converters can be arbitrarily enhanced by extending the number of phases and voltage multiplier (VM) stages, respectively. The experimental results of 500‐W prototypes demonstrated passive current balancing, reduced semiconductor voltage stresses, and enhanced step‐up conversion ratios. [ABSTRACT FROM AUTHOR]

A multitransmitter (multi-TX) inductive power transfer system would not only offer better spatial freedom but also improve the overall output capability. Under heavy-load condition, it is desirable to fully utilize the output power capability, and the overall input power needs to be balanced among the multiple TXs. This article proposes a simple and low-cost current sharing method to balance the input power. The current distribution is analytically studied for an example two-TX system, and the sharing path is proposed to balance the power under coupling variation and coil inductance mismatch. It also explores the influence of sharing path on the efficiency and zero-phase operation. Besides, the proposed method is valid for other compensations and can be extended for N-TX (N $>$ 2) systems. Finally, a two-TX system is implemented to verify the sharing effect. The current imbalance factor is effectively reduced from 37% to 2.7% under the worst coupling cases. [ABSTRACT FROM AUTHOR]

In this article, a current balancing coupled inductor (CBCL) based asymmetrically configured quad-active-bridge (QAB) converter is proposed. The QAB converter provides high-frequency isolation for a dc–dc stage of a solid state transformer (SST), as well as provides a modular solution to the SST medium-voltage (MV) dc link. The proposed CBCL ensures current balancing among/three active H-bridges without using any dedicated controller and without expensive sensors when transferring equal power from MV to low-voltage side. The proposed CBCL is the integration of three inductors of the active H-bridges required for power transfer and zero-voltage-switching and does not require an extra magnetic volume. Experimental results are presented to validate the performance. [ABSTRACT FROM AUTHOR]

The equipment cost of pumping unit is one of the main investment costs of No. 2 oil production plant. Its annual power consumption is 41 million kwh, accounting for 10.8% of the energy consumption cost of the whole plant. The existing pumping units mainly include 14 and 16 beam walking units and 900 and 1 000 vertical units. According to the electrical parameter test and calculation, the average system efficiency is only 18.8%, far lower than the domestic average of 27%. Therefore, the management should be strengthened to improve the energy saving of the system. In this paper, the main reason of energy consumption loss of pumping unit in our plant is pointed out through the research and field practice of pumping unit energy saving, and the method of reducing cost and energy saving that is suitable for the second plant is found, which provides a guiding method for the later energy saving of pumping unit, and has great significance for comprehensive promotion. [ABSTRACT FROM AUTHOR]

An LED driver consisting of dimmable current balancing circuits (CBCs) and a boost converter with drain voltage balance (DVB) and phase-shifted pulsewidth modulation (PSPWM) control schemes is presented. To reduce the power loss on conventional linear current regulators, CBCs are employed. The DVB control scheme is proposed to maintain a desired constant voltage across the CBCs, so as to increase current balance and achieve high efficiency of the CBCs. Thus, the bus voltage of the boost converter is adaptively regulated based on the DVB control. The PSPWM control scheme can alleviate the variation of the bus current provided by the boost converter. As a result, the transient ripple of the bus voltage can be reduced when the light-emitting diode (LED) strings are turned on and off. Furthermore, the utilization of DVB control is increased when the PWM dimming duty cycle becomes lower. The experimental results demonstrate that the minimum voltage among the CBCs is always kept at the lowest constant level while maintaining the required current passing through the LED strings. The efficiency of the CBCs is kept almost the same for different LED currents and is over 95%. Thus, a high-efficient parallel-string dimmable LED driver with simple circuitry can be achieved. [ABSTRACT FROM PUBLISHER]

In this paper, a single-switch coupled-inductor-based two-channel light-emitting diode (LED) driver with a passive regenerative snubber is presented. In the proposed LED driver, the energy-transferring capacitor is not only used to step up the voltage gain but also to achieve the current balance among LED strings. Moreover, a passive regenerative snubber is added not only to recycle the leakage inductance energy but also to improve the voltage gain. As compared with the prior work, only one switch is required. Thus, the configuration of the proposed LED driver is simpler. Since the proposed LED driver has a higher voltage gain than the prior work, the turns ratio of the proposed LED driver can be lower. Thus, the magnetic core size can be reduced. In addition, both LED drivers have the same component count. Finally, the operating principle, analysis, and experimental results are provided to verify the effectiveness of the proposed LED driver. [ABSTRACT FROM AUTHOR]

In recent years, R&D trends in the automobile industry have involved developing vehicles that are eco-friendly and have good fuel economy in order to meet increasingly stringent vehicle emission and fuel economy regulations. Among various environmentallyfriendly vehicles, recently-developed hybrid electric vehicles have been considered a successful technology. To improve the hybrid electric vehicle's efficiency, a regenerative braking system is applied that can save waste braking energy and fuel consumption. To date, much research has been conducted that is related to regenerative brake systems for motor-assisted vehicles. In this study, a vehicle brake model and DC motor model have been developed to predict the braking and electric characteristics of vehicle and motor by using MATLAB/Simulink code and compared with brake performance reference data. Since generating current is a key factor for regenerative braking in a hybrid electric vehicle (HEV) system, electric characteristics are the focus of this study. Therefore, in order to investigate the electric characteristics, analysis is also performed using the DC motor model. The main results obtained by this study are that the vehicle braking dynamics calculated by MATLAB/Simulink simulation were in reasonable agreement with reference values. Using the vehicle brake model, analysis is carried out for investigating the numerical model's characteristics and performances at initial velocity, slip ratio and road conditions. Additionally, experimentation is carried out using a chassis dynamometer and a hybrid electric vehicle, and the data are analyzed. [ABSTRACT FROM AUTHOR]

This paper proposes a simple capacitor clamped current-sharing circuit including linear and loop types according to the connection of capacitors for multistring light-emitting diodes (LEDs). The proposed circuit employs interleaved turn-on switches and multicapacitor charge conservation to solve the current imbalance problem caused by voltage drop tolerance and the negative temperature coefficient of LEDs. The operating principle and parameter design of the topologies are analyzed in detail. Based on this analysis, a three-string current-sharing topology has been validated by experiments. Experimental waveforms show that the proposed circuit does not only have good effect on current sharing while the effect is not affected by individual LED short but also has the advantages of low voltage stress, nonmagnetic components, ease of integration, and simple control. [ABSTRACT FROM PUBLISHER]

Higher power applications require a multilevel converter to meet high power ratings. A multimodule current-source converter (CSC) can provide a multilevel current waveforms and at the same time eliminate the bulky transformer at the ac side. However, it is required for the multimodule CSC to use multiple dc-link inductors for the purpose of power balance among different modules. Thus, one key issue in the design of the multimodule CSC is to balance the current through different dc-link inductors. This paper focuses on studying the control strategy of the multimodule CSC and a generalized current balancing method is presented. As presented, zero vectors are distributed based on the deviation of the dc-link inductor currents and the comparison of the capacitor voltages. Therefore, the current imbalance problems, not only those among the upper inductors but also those among the lower inductors are solved. Moreover, since the current balancing algorithm is not dependent on module numbers, the presented control strategy is very suitable for modularization. Especially, with the feedback of the capacitor voltages, the resonance arising from the inductor-capacitor (LC) filter is damped. In addition, a design method of the dc-link inductors is also derived. Finally, simulation and experimental results show the validity of the propositions. [ABSTRACT FROM AUTHOR]

Traditional current-mirror methods require one fixed current reference for controlling other current source or sources. In this paper, a new self-configurable current-mirror method that can dynamically determine the best current branch as the current reference in order to ensure good balance of all parallel current sources is proposed. The operating principle involves a dynamic and self-configurable transistor-based current-balancing circuit that can be operated in saturation or linear mode. In either operating mode, good current balance or sharing among all parallel-connected current sources can be guaranteed. The novel current-balancing circuit does not require a separate power supply for powering their control circuits. The proposal is a modular one that can be expanded to any number of parallel current sources. Its principle has been successfully applied to current balancing of parallel LED strings. [ABSTRACT FROM AUTHOR]

This paper presents a capacitor-isolated light-emitting diode (LED) driver with inherent current-balancing capability. Based on a series resonant converter, the resonant capacitor can be used both for safety isolation and the current balancing with the proposed two-output rectifier structure. Compared to the conventional current-sharing technique, the proposed LED driver circuit is simple and has low cost and high performance. Also, the capacitor-isolated structure is more efficient and compact compared to the conventional transformer isolation. The detailed theoretical analysis and design considerations of the proposed circuit are presented. The performance of the proposed circuit is validated by the experimental results from a 60-W prototype with two balanced outputs. [ABSTRACT FROM AUTHOR]

This paper introduces a new method of passive current balancing for digital control of multiphase dc-dc converters based upon the duty-cycle-matching principle. Current balance is achieved by inserting a digital filter into the control path. The method does not rely on a current balancing loop, and therefore, the stability and performance concerns associated with the traditional current balance loop are obviated. Being sensorless, it is insensitive to current measurement inaccuracies caused by noise, component value tolerance, or variation. It will be shown that effective current balancing can be achieved via some simple modifications to standard voltage-mode control laws, allowing current balancing to be achieved with minor additional complexity. The effectiveness of the method has been demonstrated by experimental validation of a multiphase dc-dc converter. The current share scheme has been shown to perform well dynamically, matching currents cycle by cycle during load steps, and clearly benefiting from the absence of the slow current share loop popular in traditional methods. The proposed current share filter blends well with existing digital controllers. Given the very low complexity in implementing the filter, the degree of matching achieved is exceptional. [ABSTRACT FROM AUTHOR]

Multiphase is an old technique that, nowadays, is widely used in several dc-dc applications such as voltage regulator module and automotive. The number of phases is usually kept relatively low (three or four) in most cases. However, the advantages of multiphase converters (mainly the reduction of input and output filters with its associated increase in maximum control bandwidth) grow with the number of phases in the ideal case. This growth is limited by nonidealities, mainly the tolerances of components (semiconductors and inductors). The purpose of this paper is to evaluate the effect of tolerances of the inductance on the current ripple. This nonideality causes the loss of two important advantages of multiphase converters, such as very high frequency and very low amplitude current ripple. The use of digital control can help to reduce drastically this problem. A simple algorithm, based on changing the triggering sequence of the phases, allows a big reduction of the impact of this nonideality. Experiments are included in the paper. [ABSTRACT FROM AUTHOR]

Cold cathode fluorescent lamps (CCFLs) show complex characteristics, which make it difficult to drive them in parallel. In this paper, a backlight inverter, which can drive multiple CCFLs using single controller and single switching network, is presented. The analysis of the lamp current distribution is presented in detail. The current-balancing condition, under which the lamp currents are well balanced in the presence of the lamp voltage variation, is derived. The effect of the resonant component variation is also investigated. The analysis results are verified from experiments with two 720-mm/4-mm CCFLs for 32-in liquid crystal display televisions. Experimental results with eight CCFLs are also presented in the presence of the lamp voltage and the resonant component deviation. [ABSTRACT FROM AUTHOR]

In order to develop a reactor for a LC resonance-type fault current limiter, we have been studying a pancake-type HTS coil with a low loss and a high current capacity. Double-pancake coils wound by Bi2223 tape wire are adopted as a unit coil for the reactor. In the double-pancake coil, two Bi2223 tapes are wound in parallel to each other to obtain a high current capacity. Besides, a stainless steel wire is co-wound with the Bi2223 tapes in order to increase the mechanical strength. The reactor is designed as an air-core type one to obtain a constant inductance. 12 unit double-pancake coils are manufactured. They are located in a toroidal shape in order to obtain symmetry. 12 unit coils are connected in "3-parallel/4-series" mode. The critical current, the AC loss, and the current sharing ratio between the unit coils are measured. From the experimental results, it has been confirmed that the current sharing among the 3 parallel circuits is uniform, in spite of some deviations between the critical currents of each unit coil. [ABSTRACT FROM AUTHOR]

This paper proposes a gate drive circuit for the current balancing of parallel-connected SiC-JFETs under avalanche mode. For a solid-state DC circuit breaker, the power devices have to be connected in parallel to reduce the ON-resistance and increase the current rating. In addition, it is reported that the SiC-JFET is suitable power devices from the viewpoint of both conduction loss and long-term reliability. This paper presents the behavior of current balancing of SiC-JFETs in parallel, and then proposes a design procedure of gate drive circuits. The gate drive circuits can achieve the current balance equalization of parallel-connected SiC-JFETs under avalanche mode. The validity of the proposed gate drive circuit is verified by the experiment that uses 1.2 kV SiC-JFETs in a 400 V system. [ABSTRACT FROM AUTHOR]