Non-electrolytic Capacitors Research Articles

A capacitor-free driving stage for light emitting diodes

Electrolytic capacitors have the disadvantage of pronounced aging. Non-electrolytic capacitors are therefore used in applications where long-life is important. In this paper we present a driving stage for LEDs without any capacitive elements. The basic topology is a Buck converter with one coil, one active, and one passive switch. Instead of the output capacitor, series connections of one or more LEDs and an active switch are connected. An additional diode is connected between the output and the input to achieve a current path, when all LED-paths are off. A nonlinear hysteresis controller is used to achieve a robust control. A system with three switchable LED-strings is analyzed. Design hints are given and the function is proved with the help of LTSpice simulations. The system can be used for lighting purposes with the possibility to change the chrominance. The potentiality to transmit data is also treated.

Bridgeless PFC Converter without Electrolytic Capacitor Based on Power Decoupling

Due to fewer conduction devices in operating condition, the bridgeless power factor correction (PFC) converter is more efficient than the traditional PFC circuit. However, to achieve a low output voltage ripple on the DC side, a large electrolytic capacitor must be connected in parallel to the output end. To reduce the value of capacitance, this paper proposes a dual-boost bridgeless PFC converter with a bidirectional buck/boost power decoupling converter in the latter stage. The bidirectional converter absorbs double-line-frequency ripple, lowering the power pulsation at the output end while realizing power decoupling. The one-cycle control is adopted in bridgeless PFC converter, so that the input current can follow the input voltage to achieve power factor correction and decrease harmonic pollution. The power decoupling circuit is designed with a voltage outer loop using PI control and a current inner loop using model predictive current control, which alleviates the output voltage fluctuation caused by the reduction of the capacitance value of the filter capacitor, for the purpose of realizing non-electrolytic capacitor. Finally, the topology and control strategy involved in this paper are simulated and experimented to verify the validity and superiority of the theory.

A Single-Stage Bimodal Transformerless Inverter with Common-Ground and Buck-Boost Features

This paper proposes a single-phase, single-stage common-ground inverter with a non-electrolytic capacitor and buck-boost ability. The proposed single-stage inverter is employed by a boost stage DC-DC converter and bimodal circuit, which makes it satisfactory for PV systems with a wide input voltage range and lower switch voltage stress. The leakage current of the proposed single-stage inverter can effectively suppress because the parasitic capacitor between the PV panel and the ground is shortened. In addition, the proposed single-stage inverter does not include electrolytic capacitors, which reduces the equivalent series resistance of electrolytic capacitors and also the size of the inverter system. The topology, operating principle, and PWM control method of the proposed single-stage inverter are given. The design guidelines of components and comparative studies of the proposed single-stage inverter are provided. A 500 W laboratory prototype of the proposed single-stage inverter is built to verify the correctness of the simulation and theoretical analysis.

High power non-electrolytic capacitor LED driver with three ports based on energy distribution

To eliminate the influence of electrolytic capacitors on the driving life of high-power LED, a three-port high-power LED without electrolytic capacitor driving power supply based on energy distribution is proposed. The energy difference between the input terminal and the output terminal is balanced by the auxiliary DC-DC circuit to reduce the ripple of the output current. The working principle of the topology and switching mode is analyzed in detail. According to the proposed circuit topology, the mechanism of the output current ripple of the low-frequency circuit is analyzed, and a low-frequency ripple control strategy suitable for the circuit topology is proposed. The specific implementation scheme and the key parameters of the circuit design are given, and the model is verified, which proves that the proposed model is feasible.

Modeling, analysis and experimental verification of two non-electrolytic capacitor Z-source converters

Modeling, analysis and experimental verification of two non-electrolytic capacitor Z-source converters

A Novel Single-Stage Common-Ground Zeta-Based Inverter With Nonelectrolytic Capacitor

Aiming at the key problems of the existing nonisolated photovoltaic (PV) inverter, such as the common mode (CM) leakage current, the voltage up and down ability, and the service life restricted by the electrolytic capacitor, a novel single-stage common-ground zeta-based inverter with nonelectrolytic capacitor is proposed in this article. The proposed inverter is based on zeta dc converter and has the inherent voltage conversion characteristics of zeta converter, which makes it more suitable for PV system with wide input voltage fluctuation range. In addition, common-ground structure is adopted in this inverter, which can shorten the parasitic capacitor of the PV array to the ground. Therefore, it can effectively suppress the CM leakage current, reduce the shutdown frequency of the PV system, and improve the utilization rate of solar energy. Moreover, the proposed inverter does not contain electrolytic capacitors, which avoids the problem of high maintenance cost due to the short service life and high equivalent series resistance of electrolytic capacitors. First, the topology of the proposed inverter is given, and the modulation and operating principle are analyzed. Second, the passive components are analyzed. Finally, a 1 kW prototype is built for experimental verification. The experimental results verify the correctness of the theoretical analysis and simulation.

2021 best paper award winners

Both papers proposed novel designs of critical components for photovoltaic applications. Paper 1 presents a high step-up converter with an hourglass-shaped impedance network. The design allows the use of non-electrolytic capacitors, which leads to reduced size and weight, as well as longer lifetime compared to conventional converters. Meanwhile, paper 2 presents an asymmetrical multilevel inverter capable of producing up to 15 output levels. Compared to state-of-the-art solutions, it uses a minimum number of components per level. In both papers, rigorous design and performance analyses are complemented by comparative studies against existing literature solutions and corroborated by experimental validations. I wish to thank the authors of all nominated articles, wishing them success in the future, and many congratulations to the winners of this year's award. Special thanks go to Dr. Paolo Manfredi (Politecnico di Torino, Italy), member of the Editorial board, for overseeing the nominations and the selection process. My sincere congratulations to the winners.

Non‐electrolytic‐capacitor boost converter with non‐pulsating ripple‐free output current

SummaryA novel boost converter is proposed in this study, which is based on a newly designed impedance network, instead of using the traditional Z‐network structure and large electrolytic capacitors (ECs) to suppress current ripples. Besides, the proposed topology has ripple‐free output current, which is designed to improve the output current quality of the traditional boost converter and to enhance the voltage conversion ratio compared to the traditional Z‐network boost converter. The newly proposed impedance network consists of two inductor and capacitor (LC) pairs—one LC pair function as the intermediate energy transferring branch and the other pair as the output branch to obtain non‐pulsating output current. The operating principle and performance of the proposed converter are analyzed in detail for demonstrating its advanced features. Furthermore, the feasibility of the proposed converter topology is validated by its simulations and experimental studies. Compared to ECs, non‐electrolytic capacitors (NECs) have the benefit of low cost, small size, and long operating life, which brings high economical advantages to the proposed converter with enhanced voltage conversion performances.

A High-Performance Isolated SEPIC Converter for Non-Electrolytic LED Lighting

This paper proposes a high-performance isolated single-ended primary inductor converter (SEPIC) that is integrated with a non-dissipative snubber for a light-emitting diode (LED) driver. The proposed LED driver employs the snubber circuit to minimize any switching overvoltage caused by parasitic leakage inductance of the high-frequency transformer in the isolated SEPIC converter. This paper also presents a detail theoretical analysis of the proposed LED driver including its operating modes and design calculation. The experimental results of the proposed LED driver at the rated power of 18 W shows that it has a high-power factor, low harmonics, employs non-electrolytic capacitors, low switching stress, high reliability and high efficiency.

Hourglass‐shaped impedance network based nonelectrolytic capacitors high step‐up converter with low voltage stress

SummaryIn this study, a novel high‐step‐up converter is proposed with a new hourglass‐shaped impedance network (HIN). Due to the short lifetime of electrolytic capacitors (ECs), the proposed converter uses nonelectrolytic capacitors (NECs), which however can realize all ECs' features. Besides, the proposed converter has low capacitor voltage stresses, ensuring it could be electrolytic‐capacitors‐free. With this feature, the proposed high step‐up converter has smaller size, lighter weight, smaller parasitic resistance, and longer operation life than the conventional ones with ECs. In this paper, detailed operational principle and performance of the proposed converter are presented, to demonstrate its advanced features. Simulation and experimental studies are also carried out, which validate the feasibility and effectiveness of the proposed converter.

A Single-Switch High-Gain PV Microconverter With Low-Switch-Voltage-to-High-Voltage-Bus Ratio

A new soft-switched, single-switch electrolytic capacitor-less step-up dc/dc microconverter for photovoltaic applications is presented in this article. The proposed circuit is an improved coupled-magnetics based single-switch topology that has low-voltage stress across the switch compared to the high voltage dc bus level (380–400 V). The proposed circuit is able to achieve zero voltage switching turn- on and zero current switching turn- off for the switch. Since the input inductor in the proposed circuit operates in continuous conduction mode, the required input filter capacitance is reduced and hence, allows for the small-size nonelectrolytic capacitor to be used. The main advantage of the proposed circuit is that it is able to achieve high voltage gain while the ratio between the peak switch voltage and the output dc-bus voltage is reduced compared to other coupled-inductor based topologies. In addition, the proposed converter is able to achieve maximum power point tracking through variable switching frequency control. Results are provided on a 40-V/380-V, 200-W system to highlight the merits of the proposed circuit.

Control of Single-Phase Electrolytic Capacitor-Less Isolated Converter for DC Low Voltage Residential Networks

In recent years, there has been a desire to improve electricity generation and consumption, to reach sustainability. Technological solutions today allow a rational use of electricity with good overall performance. Traditionally, from production to distribution, electrical energy is AC-supported for compatibility reasons and easy voltage level transformation. However, nowadays most electric loads need DC power to work properly. A single high-efficiency central AC-DC power converter may be advantageous in eliminating several less efficient AC-DC embedded converters, distributed all over a residential area. This paper presents a new single-phase AC-DC converter using one active bridge (most isolated topologies are based on the dual active bridge concept) and a high-frequency isolation transformer with low-value non-electrolytic capacitors, together with its control system design. The converter can be introduced into future low-voltage DC microgrids for residential buildings, as an alternative to several embedded AC-DC converters. Non-linear control techniques (sliding mode control and the Lyapunov direct method) are employed to guarantee stability in the output DC low voltage with near unity power factor compensation in the AC grid. The designed converter and controllers were simulated using Matlab/Simulink and tested in a lab experimental prototype using digital signal processing (DSP) to evaluate system performance.

Optimized Constant Current and Ripple Control of Non-electrolytic Capacitor LED AC/DC Power

For the traditional power supply of the non-continuous load Boost-Buck LED, when it has a high power factor, it will produce a significant low frequency ripple current. In this paper, a new type of LED driver power supply technology based on buck boost topology is proposed. The advantage of this technique is that the low frequency ripple current is greatly reduced without affecting the performance of the power factor and the advantages of high efficiency and low cost of the traditional boost buck LED driver are also preserved. We validate the performance of this new technology through a 30W and 50V-2A experimental prototype.

An Alternative Approach to LED Driver Design Based on High-Voltage Driving

This paper discusses an alternative approach to designing LED drivers based on high-voltage operation. Compared with the conventional approach of driving LEDs with low voltage and high current, the alternative approach aims to deliver the same power to LED load with high voltage and low current so that small and nonelectrolytic capacitor can be used. High-voltage operation also facilitates the use of simple PFC preregulators such as boost or SEPIC converters as single-stage LED drivers. This paper begins with the derivation of the relationship between the nominal output voltage and output capacitor's size of a PFC preregulator for achieving a given output voltage ripple's size, followed by a review of the recently emerged high-voltage LED packages suitable for the proposed application. This paper also discusses the flicker and colorimetric performances of LED light sources under the influence of large current ripple when nonelectrolytic capacitor is used. The method of third-harmonic current injection to the input current of LED drivers is also incorporated as an option for further reducing the output capacitor's size while meeting a specified flicker limit. Finally, a design example of high-voltage LED driver based on a boost PFC preregulator with third-harmonic current injection is presented and verified experimentally.

A Single-Stage Three-Phase Inverter Based on Cuk Converters for PV Applications

This paper presents a new three-phase inverter based on the Cuk converter. The main feature of the proposed topology is that the energy storage elements, such as inductors and capacitors, can be reduced in order to improve the reliability, and reduce size and total cost. The buck-boost inherent characteristic of the Cuk converter, depending on the time-varying duty ratio, provides flexibility for standalone and grid connected applications when the required output ac voltage is lower or greater than the dc side voltage. This property is not found in the conventional current source inverter when the dc input current is always greater than the ac output or in the conventional voltage source inverter as the output ac voltage is always lower than the dc input. The proposed system allows much smaller, more reliable nonelectrolytic capacitors to be used for energy source filtering. The new three-phase inverter is convenient for photovoltaic applications where continuous input currents are required for maximum power point tracking operation. Average large and small signal models are used to study the Cuk converter's nonlinear operation. The basic structure, control design, and MATLAB/SIMULINK results are presented. Practical results substantiate the design flexibility of the Cuk-based topology controlled by a TMSF280335 DSP.

LED Lamp Power Supply without Electrolytic Capacitors based on Integrated Double Buck-Boost Converter Operating in Full DCM

In this paper the integrated double buck-boost converter (IDBBC) operating with both stages in discontinuous conduction mode (DCM) is analyzed. The converter is intended to supply high-voltage LED lamps from the mains, typically in street lighting applications. A high input power factor is assured by operating the first stage in DCM, thus complying with current harmonic injection standards. In this work, the second stage is also operated in DCM as an option to the continuous conduction mode (CCM) that has been studied in a previous paper. The behavior of the converter with both stages in DCM is compared with that of the converter operation with the second stage in CCM. It is demonstrated that with both converters operating in DCM the filter capacitances are reduced even further, allowing for the use of long-life non-electrolytic capacitors. A laboratory prototype to supply a 70 W LED lamp with nominal voltage of 200 V from a 230 V/50 Hz mains maintaining the same design conditions as in the previous work is presented. A comparison of both prototypes is also carried out.

An improved reliability cuk based solar inverter with sliding mode control

Many photovoltaic inverter designs make use of a buck based switched mode power supply (SMPS) to produce a rectified sinusoidal waveform. This waveform is then unfolded by a low frequency switching structure to produce a fully sinusoidal waveform. The Cuk SMPS could offer advantages over the buck in such applications. Unfortunately the Cuk converter is considered to be difficult to control using classical methods. Correct closed loop design is essential for stable operation of Cuk converters. Due to these stability issues, Cuk converter based designs often require stiff low bandwidth control loops. In order to achieve this stable closed loop performance, traditional designs invariably need large, unreliable electrolytic capacitors. In this paper, an inverter with a sliding mode control approach is presented which enables the designer to make use of the Cuk converters advantages, while ameliorating control difficulties. This control method allows the selection of passive components based predominantly on ripple and reliability specifications while requiring only one state reference signal. This allows much smaller, more reliable non-electrolytic capacitors to be used. A prototype inverter has been constructed and results obtained which demonstrate the design flexibility of the Cuk topology when coupled with sliding mode control.