Electrolytic Capacitor-Less Research Articles

Electrolytic Capacitorless AC/DC LED Driver

This paper presents electrolytic capacitorless AC/DC LED driver. It adopts Boost–Buck topology, through modulation of the conduction time [Formula: see text] and the change of input current reference, to reduce the instantaneous input and output power difference, so a smaller film capacitor can be used instead of the electrolytic capacitor. Therefore, LED driver power life has been effectively improved. The Buck converter operates in the inductor current discontinuous conduction mode to achieve constant output current by controlling the peak current. The control IC is fabricated in TSMC 0.35-[Formula: see text]m 5-V/650-V CMOS/LDMOS process, and verified in a 72-V/150-mA circuit prototype. The test results show that when the range of input voltage is 175–264 Vac, the efficiency of the system is 83%, the voltage linear regulation is [Formula: see text]%, the load regulation is [Formula: see text]%, and the electrolytic capacitor is replaced by 470-nF CBB capacitor under the condition that the power factor is above 0.7. Therefore, the design of the control chip in the LED driver has a very good application prospect.

Dual Antiovervoltage Control Scheme for Electrolytic Capacitorless IPMSM Drives With Coefficient Autoregulation

Electrolytic capacitorless vector-controlled interior permanent-magnet synchronous motor (IPMSM) drives have many advantages, such as higher reliability, longer lifetime, and lower cost. However, the dc-link may suffer from the overvoltage during motor transient process due to the use of slim film capacitors in the diode rectifier front end. The conventional antiovervoltage method by controlling the quadrature axis current will lead to energy control error, which causes large dc-link voltage control error. In this paper, a novel antiovervoltage control scheme with coefficient autoregulation is proposed based on the concept of system loss. A dual antiovervoltage controller is designed to enhance the voltage control performance by controlling both the direct and quadrature axis currents to achieve more effective active braking. The coefficients of the dc-link voltage controller are autoregulated to maintain the enough stability margin during the regenerative braking. By using the proposed method, the dc-link overvoltage phenomenon can be avoided while guaranteeing the maximum copper loss during the braking process. The proposed algorithm is ultimately verified on an electrolytic capacitorless IPMSM drive.

LED Driver Achieves Electrolytic Capacitor-Less and Flicker-Free Operation With an Energy Buffer Unit

Electrolytic capacitors are often needed to provide the high-density energy storage required by ac-powered LED drivers; however, they are also well known for their short lifespans. Eliminating electrolytic capacitors in ac–dc LED driver design has become a very important target to improve LED driver technology. In this paper, a cycle-by-cycle energy buffering LED driver has been proposed to achieve electrolytic capacitor-less flicker-free operation. An energy buffering unit, with high-voltage film capacitors being the energy storage device, is introduced in the design to buffer the imbalanced energy in every switching cycle. The switching current can be controlled to meet high power factor correction requirement, while maintaining dc LED output current at the same time. Compared to previous electrolytic capacitor-less designs, this technology can reduce circulating power and, therefore, power conversion loss. A 15-W experimental prototype had been built and tested to verify the proposed LED driving method.

Single-Stage LED Driver Achieves Electrolytic Capacitor-Less and Flicker-Free Operation With Unidirectional Current Compensator

AC-connected light emitting diode (LED) drivers experience imbalanced energy between input and output in a half-line cycle. To achieve the flicker-free operation, the imbalanced energy needs to be buffered, often by energy-dense electrolytic capacitors. However, electrolytic capacitors are also well-known for their short lifespan. These capacitors are the limiting factor of an LED drivers’ lifespan. High voltage film capacitors and a buck converter have been used in the proposed LED driver to buffer the imbalanced energy. When P in > P LED, the extra energy is transferred from the ac input directly to the high voltage film capacitors. When P in P LED, the energy is transferred from the high voltage film capacitors to the output by the buck converter. The imbalanced energy goes through two power conversion steps in the proposed LED driver, which is one time less than other comparable electrolytic capacitor-less designs, enabling a higher efficiency to be achieved. A 28 W flyback topology based experimental prototype had been built and tested to verify the proposed design.

An Antiovervoltage Control Scheme for Electrolytic Capacitorless IPMSM Drives Based on Stator Current Vector Orientation

Three-phase input diode rectifier interior permanent magnet synchronous motor (IPMSM) drives with small-volume film capacitors have many merits, such as high reliability, high power density, and low cost. However, in regenerative braking mode, the dc link may suffer from overvoltage due to the application of slim film capacitors. In this paper, a novel antiovervoltage strategy is proposed by controlling the motor voltage using stator current vector orientation. The relationship among the braking torque, the dc-link capacitance, and the antiovervoltage ability is analyzed quantitatively. Based on the analysis of principle, a closed-loop antiovervoltage regulation scheme is presented, which is easy for applications. Additionally, this method has the merit of low motor parameter dependence. Meanwhile, the small signal model of the electrolytic capacitorless IPMSM drive is derived for the coefficient design of the voltage controller. The proposed algorithm is finally implemented on a 2.2-kW electrolytic capacitorless IPMSM drive platform to verify the effectiveness of the antiovervoltage control scheme.

Analysis and Control of Electrolytic Capacitor-Less LED Driver Based on Harmonic Injection Technique

AC-DC LED drivers may have a lifespan shorter than the lifespan of LED chips if electrolytic capacitors are used in their construction. Using film capacitors solves this problem but, as their capacitance is considerably lower, the low-frequency ripple will increase. Solving this problem by limiting the output ripple to safe values is possible by distorting the input current using harmonic injection technique, as long as these harmonics still complies with Power Factor Regulations (Energy Star). This harmonic injection alleviates the requirements imposed to the output capacitor in order to limit the low-frequency ripple in the output. This idea is based on the fact that LEDs can be driven by pulsating current with a limited Peak-To-Average Ratio (PTAR) without affecting their performance. By considering the accurate model of LEDs, instead of the typical equivalent resistance, this paper presents an improved and more reliable calculation of the intended harmonic injection. Wherein, its orders and values can be determined for each input/output voltage to obtain the specified PTAR and Power Factor (PF). Also, this harmonic injection can be simply implemented using a single feedback loop, its control circuit has features of wide bandwidth, simple, single-loop and lower cost. A 21W AC-DC buck converter is built to validate the proposed circuit and the derived mathematical model and it complies with IEC61000 3-2 class D standard.

Hybrid-Modulation-Based Bidirectional Electrolytic Capacitor-Less Three-Phase Inverter for Fuel Cell Vehicles: Analysis, Design, and Experimental Results

This paper presents a novel six-pulse low-frequency (LF) fluctuating high-voltage dc-bus-based power system architecture for fuel cell vehicles (FCVs) application. A novel hybrid modulation scheme consisting of six-pulse modulation at LF scale and modified secondary modulation and 33% pulse width modulation at high-frequency (HF) scale is proposed. Three-phase ac waveforms for the propulsion system of FCVs are generated from LF fluctuating high-voltage dc bus. The proposed modulation technique significantly reduces the switching losses of the bidirectional dual-stage inverter: 1) soft-switching of both sides of the front-end current-fed full-bridge converter is realized; and 2) at any moment, only one leg of back-end three-phase inverter is switched at HF, while the other two legs are kept in on or off states. This tremendously reduces the bidirectional inverter's switching losses and improves the system efficiency. The LF fluctuating high-voltage dc bus allows the elimination of large electrolytic dc-link capacitor, which contributes to a more reliable and compact design. This paper presents the operation, analysis, and design of a bidirectional inverter implementing the proposed hybrid modulation technique. Simulation results obtained from power electronics simulation software PSIM and experimental results from the lab prototype clearly validate the effectiveness of the proposed modulation technique.

One-Cycle Control for Electrolytic Capacitor-Less Second Harmonic Current Compensator

The input power of the single-phase power factor correction ac–dc converter pulsates at twice the line frequency, while the output power of the single-phase dc–ac inverter pulsates at twice the output frequency. The pulsating power will result in second harmonic current (SHC) in the ac–dc converter and dc–ac inverter. In this paper, electrolytic capacitor-less second harmonic current compensator (SHCC) is presented to compensate the SHC. The SHCC has two operating modes, namely, charging mode and discharging mode. To achieve an excellent SHC compensation performance, a hybrid one-cycle control (OCC) is proposed to regulate the port current of the SHCC, and the SHCC can stably operate in both the charging mode and discharging mode. To avoid the mode detection required in the hybrid OCC and ensure seamless transition between the two modes, the OCC with dc bias is further proposed. Besides, a peak voltage control is proposed to regulate the storage capacitor voltage in the SHCC for reducing the power losses of the SHCC at light load. A 1-kW two-stage inverter with the SHCC is fabricated and tested, and the experimental results are provided to verify the effectiveness of the proposed control schemes.

An Electrolytic Capacitor-Less High Power Factor LED Driver Based on a “One-and-a-Half Stage” Forward-Flyback Topology

A “one-and-a-half stage” forward-flyback converter for electrolytic capacitor-less light-emitting diode (LED) driver with high power factor (PF), high efficiency, low output ripple current, and long lifetime has been proposed and studied in this paper. The basic topology of the proposed topology is a single-switch forward-flyback converter for achieving high PF. In addition, a buck converter is inserted between the forward subconverter and the load for creating two paralleled power transfer paths. The most of input energy directly reaches the load through flyback subconverter, and only about 1/4 of total energy is transferred to the load through forward subconverter and buck converter. Therefore, the proposed topology is a “one-and-a-half stage” converter and can achieve higher efficiency than the traditional two-stage topologies. At the same time, power decoupling can be realized and the electrolytic capacitor can be eliminated. Optimal control scheme, detailed analysis, and design considerations for this improved converter are presented. Finally, an experimental prototype for 28 V/700 mA LED driver was built up to verify the theoretical analysis.

An Electrolytic Capacitorless Bidirectional EV Charger for V2G and V2H Applications

In this paper, a bidirectional battery charger is proposed for grid-to-vehicle, vehicle-to-grid, and vehicle-to-home operations of electric vehicles. The proposed charger adopts sinusoidal charging to eliminate the use of electrolytic capacitors. A nonregulating series resonant converter is employed for isolation, thereby minimizing the ratings of the components and achieving zero-current switching turn on and off of switches. Meanwhile, an ac–dc converter is employed to control each mode and their mode changes, making the whole control scheme simple and the mode changes seamless. A 3.3-kW prototype was built in the laboratory to validate the proposed concept. Our experimental results demonstrate that the proposed charger has high efficiency and can seamlessly switch between the three operation modes.

Fine Current Harmonics Reduction Method for Electrolytic Capacitor-Less and Inductor-Less Inverter Based on Motor Torque Control and Fast Voltage Feedforward Control for IPMSM

In an electrolytic capacitor-less and inductor-less single-phase-to-three-phase inverter, the inverter controls not only the motor but also the input power factor. If the motor has large spatial harmonics, the harmonics flow into the input current at the source side. This paper proposes two new power factor correction methods to improve the input current response of a fundamental frequency and to reduce the input current harmonics. The first method realizes high-power-factor operation by adopting a motor torque control strategy that focuses on the relationship between the input power and the motor torque. The motor torque control allows for designing the gain of the controller to realize a high power factor and enhances the robustness against motor parameter variations. The second method improves the inverter output power response by using a fast voltage feedforward control (FVFFC) that controls the inverter output power directly by focusing on the average dc-link current. The FVFFC reduces the input current harmonics owing to the spatial harmonics of an interior permanent-magnet synchronous motor, and the input current harmonics satisfy the recommendations of guideline JIS 61000-3-2. The effectiveness of the proposed methods is verified through experiments.

A Reduced Component count Single-stage Electrolytic Capacitor-less Interleaved Totem-pole On-board Battery Charger

A Reduced Component count Single-stage Electrolytic Capacitor-less Interleaved Totem-pole On-board Battery Charger

Delay-Lock-Loop-Based Inductorless and Electrolytic Capacitorless Pseudo-Sine-Current Controller in LED Lighting Systems

Light-emitting diode lighting system with the proposed pseudo-sine-current controller removes most of the external passive components, which include inductor, electrolytic capacitor, freewheel diode, blocking diode, and the bleeding circuit for Triac dimming control, for low cost and small volume. Delay-lock loop control can ensure the in-phase operation of ac input voltage and current for high power factor (PF) and low total harmonic distortion (THD). In addition, redundant power loss in Triac dimming control is eliminated to get a high efficiency of 85%. Furthermore, a high PF of 0.997 and a low THD of 7.74% are also achieved owing to in-phase line voltage and current.

A High Power Factor, Electrolytic Capacitor-Less AC-Input LED Driver Topology With High Frequency Pulsating Output Current

Light emitting diode (LED) lamps with ac-input (50 or 60 Hz) usually require an electrolytic capacitor as the dc-link capacitor in the driver circuit to: 1) balance the energy between the input and output power, and 2) to minimize the low-frequency component of the output ripple across the LEDs. The lifetime of this capacitor, however, is much shorter than that of a LED. To maximize the potential lifetime of the LED lighting system, a new pulsating current driving LED driver that does not require any electrolytic capacitors or complicated control circuits to minimize the low-frequency (i.e., 100 or 120 Hz) output ripple is proposed in this paper. The proposed circuit is simple and a single-switch topology is designed to simplify the controller design. The proposed circuit is able to reduce the energy storage capacitance to a few microfarads range, so that film capacitor can be used to replace the unreliable electrolytic capacitor. The circuit operating principles and its theoretical analysis are provided in this paper. Simulation and experimental results are given on a 9-W LED lamp to highlight the merits of the proposed circuit.

1단 전력변환기를 가진 3상 절연형 커패시터리스 충전기

In this paper, we propose a three-phase isolated electrolytic capacitorless charger available for quick charger. In the proposed charger, electrolytic capacitor in DC link is eliminated by direct conversion from AC input to DC output. Conventional chargers are two stage structure including AC-DC and DC-DC converters, but the proposed charger can be simplified into single stage converter by using a matrix converter. And the waveform of input currents is improved by giving the weighting factor to the duty ratio of auxiliary switches. In order to verify the effectiveness of the proposed charger, simulations are carried out and a 1.2kW charger was constructed and experimented.

Feed-Forward Scheme for an Electrolytic Capacitor-Less AC/DC LED Driver to Reduce Output Current Ripple

In order to achieve high-efficiency, high-power-factor, high-reliability, and low-cost, a flicker-free electrolytic capacitor-less single-phase ac/dc light emitting diode (LED) driver is investigated in this paper. This driver is composed of a power-factor-correction (PFC) converter and a bidirectional converter. The bidirectional converter is used to absorb the second harmonic component in the output current of the PFC converter, thus producing a pure dc output to drive the LEDs. The spectrum of the output capacitor voltage of the bidirectional converter is analyzed, indicating that the output capacitor voltage contains harmonic components at multiples of twice the line frequency apart from the dc component and second harmonic component. A feed-forward control scheme with a series of calculation operation is proposed to obtain the desired modulation signal, which contains the corresponding harmonic components, to ensure the bidirectional converter fully absorb the second harmonic current in the output of the PFC converter. Finally, a 33.6 W prototype is fabricated and tested in the lab, and the experiment results show that the proposed control scheme greatly reduces the ripple of the LED driving current.

A New DC Anti-Islanding Technique of Electrolytic Capacitor-Less Photovoltaic Interface in DC Distribution Systems

This paper proposes a photovoltaic (PV) generation system interfaced with a dc distribution system. DC interface allows for the improvement of system efficiency by fully utilizing dc-based renewable sources and storage devices. In this paper, issues on PV interface for dc distribution systems are discussed for energy-efficient and reliable system implementation. AC and dc PV interfaces are mathematically analyzed. In dc distribution, eliminating electrolytic capacitors in PV interfaces improves system reliability, increases system efficiency, and reduces cost. In addition, this paper proposes a new anti-islanding technique for dc distribution as a system protection scheme. The operating principle is presented in detail and analysis shows that the proposed injected current perturbation technique is an effective solution for anti-islanding operation. A prototype converter features a simple structure with no electrolytic capacitor, which ensures a longer lifetime of the PV power circuit. Experimental results of the prototype circuit show a maximum efficiency of 98.1% and a European efficiency of 97.5%. The proposed anti-islanding technique shows fast response to the islanding condition in less than 0.2 s. It also shows that the average maximum power point tracking efficiency is 99.9% in normal conditions, which verifies the performance of the proposed scheme.

Optimum Injected Current Harmonics to Minimize Peak-to-Average Ratio of LED Current for Electrolytic Capacitor-Less AC–DC Drivers

The lifetime of an ac-dc LED driver can be increased by eliminating the electrolytic capacitor. Unfortunately, it results in pulsation with twice the line frequency in the driving current. Injection of the third and fifth harmonics into the input current can reduce the peak-to-average ratio of the driving current, which is beneficial for reliable operation of the LEDs. This letter discusses the relationship between the peak-to-average ratio and the injected harmonics, and the optimum injected third and fifth harmonics to minimize the peak-to-average ratio are obtained, while ensuring that the input power factor is higher than 0.9 to meet the regulatory requirement such as the ENERGY STAR. This optimum injected current harmonics is verified by a flyback-based electrolytic capacitor-less LED driver with 25 V, 0.35 A output.

A Method of Reducing the Peak-to-Average Ratio of LED Current for Electrolytic Capacitor-Less AC–DC Drivers

This paper proposes a concept of electrolytic capacitor-less light-emitting diode (LED) driver, which converts the commercial ac voltage to a pulsating current with twice the line frequency driving high-brightness LEDs. As no electrolytic capacitor is used, this driver possesses the unique advantage of long lifetime to match with that of LEDs. A method of injecting the third and fifth harmonics into the input current to reduce the peak-to-average ratio of the output current is also proposed. While ensuring that the input power factor is higher than 0.9 to meet regulation standards such as ENERGY STAR, the proposed method allows the peak-to-average ratio of the output current to be reduced to 1.34 theoretically, which is beneficial for the safe operation of the LEDs. As an example, a flyback-based electrolytic capacitor-less LED driver is proposed, and its operation is analyzed. In order to inject the third and fifth harmonics into the input current, the function of the duty cycle in a half-line cycle is derived. It is then simplified to a fitting function, which can be easily implemented with the input voltage sensing. A 25 V, 0.35 A output prototype is built and tested in the laboratory, and the experimental results are presented to verify the effectiveness of the electrolytic capacitor-less LED driver and its control method.

Development of a Long Life Three Phase Flywheel UPS using an Electrolytic Capacitor-Less Converter/Inverter

Development of a Long Life Three Phase Flywheel UPS using an Electrolytic Capacitor-Less Converter/Inverter