Showing papers on "Flyback converter published in 2009"

Advanced Integrated Bidirectional AC/DC and DC/DC Converter for Plug-In Hybrid Electric Vehicles

Abstract: Hybrid electric vehicle (HEV) technology provides an effective solution for achieving higher fuel economy, better performance, and lower emissions, compared with conventional vehicles. Plug-in HEVs (PHEVs) are HEVs with plug-in capabilities and provide a more all-electric range; hence, PHEVs improve fuel economy and reduce emissions even more. PHEVs have a battery pack of high energy density and can run solely on electric power for a given range. The battery pack can be recharged by a neighborhood outlet. In this paper, a novel integrated bidirectional AC/DC charger and DC/DC converter (henceforth, the integrated converter) for PHEVs and hybrid/plug-in-hybrid conversions is proposed. The integrated converter is able to function as an AC/DC battery charger and to transfer electrical energy between the battery pack and the high-voltage bus of the electric traction system. It is shown that the integrated converter has a reduced number of high-current inductors and current transducers and has provided fault-current tolerance in PHEV conversion.

Three-Port Series-Resonant DC–DC Converter to Interface Renewable Energy Sources With Bidirectional Load and Energy Storage Ports

Abstract: In this paper, a three-port converter with three active full bridges, two series-resonant tanks, and a three-winding transformer is proposed. It uses a single power conversion stage with high-frequency link to control power flow between batteries, load, and a renewable source such as fuel cell. The converter has capabilities of bidirectional power flow in the battery and the load port. Use of series-resonance aids in high switching frequency operation with realizable component values when compared to existing three-port converter with only inductors. The converter has high efficiency due to soft-switching operation in all three bridges. Steady-state analysis of the converter is presented to determine the power flow equations, tank currents, and soft-switching region. Dynamic analysis is performed to design a closed-loop controller that will regulate the load-side port voltage and source-side port current. Design procedure for the three-port converter is explained and experimental results of a laboratory prototype are presented.

A Universal-Input Single-Stage High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck-Flyback Converter

Abstract: Due to the high rise in luminous efficiency that HB-LEDs have experienced in the last recent years, many new applications have been researched. In this paper, a streetlight LED application will be covered, using the Integrated Buck-Flyback Converter developed in previous works, which performs power factor correction (PFC) from a universal ac source, as well as a control loop using the LM3524 IC, which allows PWM dimming operation mode. Firstly, the LED load will be linearized and modeled in order to calculate the IBFC topology properly. Afterwards, the converter will be calculated, presenting the one built in the lab. Secondly, the converter will be modeled in order to build the closed loop system, modeling the current sensor as well in order to develop an adequate controller. Finally, experimental results obtained from the lab tests will be presented.

A Novel Three-Phase Three-Leg AC/AC Converter Using Nine IGBTs

Abstract: This paper proposes a novel three-phase nine-switch ac/ac converter topology. This converter features sinusoidal inputs and outputs, unity input power factor, and more importantly, low manufacturing cost due to its reduced number of active switches. The operating principle of the converter is elaborated; its modulation schemes are discussed. Simulated semiconductor loss analysis and comparison with the back-to-back two-level voltage source converter are presented. Finally, experimental results from a 5-kVA prototype system are provided to verify the validity of the proposed topology.

Bidirectional, High-Power DC Transformer

Abstract: This paper studies a bidirectional dc-dc converter concept which is capable of achieving very high stepping ratios with MW level power transfers. The converter can find potential application in connecting high-power dc sources, interfacing to high-voltage dc transmission or to flexible ac transmission system elements. The converter is based on two resonant circuits which share a common ac capacitor. The topology is simple and utilizes thyristors with potentially all soft switchings. Complete analytical modelling is presented which enables systematic design procedure for the converter. The detailed digital simulation on PSCAD platform confirms satisfactory operation on a 5-MW test system, which connects 4-kV dc source to an 80-kV high voltage dc grid. The converter shows good responses to rapid changes in power magnitude/direction and it is concluded that robustness to terminal voltage disturbances is excellent. Since the highest-power phase-control thyristors are employed, the converter can potentially be used at much higher power levels. The passive components are of reasonable size.

An Interleaved Boost Converter With Zero-Voltage Transition

Abstract: This paper proposes a novel soft-switching interleaved boost converter composed of two shunted elementary boost conversion units and an auxiliary inductor. This converter is able to turn on both the active power switches at zero voltage to reduce their switching losses and evidently raise the conversion efficiency. Since the two parallel-operated elementary boost units are identical, operation analysis and design for the converter module becomes quite simple. A laboratory test circuit is built, and the circuit operation shows satisfactory agreement with the theoretical analysis. The experimental results show that this converter module performs very well with the output efficiency as high as 95%.

Multiphase Bidirectional Flyback Converter Topology for Hybrid Electric Vehicles

Abstract: For hybrid electric vehicles, the batteries and the drive dc link may be at different voltages. The batteries are at low voltage to obtain higher volumetric efficiencies, and the dc link is at higher voltage to have higher efficiency on the motor side. Therefore, a power interface between the batteries and the drive's dc link is essential. This power interface should handle power flow from battery to motor, motor to battery, external genset to battery, and grid to battery. This paper proposes a multi-power-port topology which is capable of handling multiple power sources and still maintains simplicity and features like obtaining high gain, wide load variations, lower output-current ripple, and capability of parallel-battery energy due to the modular structure. The scheme incorporates a transformer winding technique which drastically reduces the leakage inductance of the coupled inductor. The development and testing of a bidirectional flyback dc-dc converter for hybrid electric vehicle is described in this paper. Simple hysteresis voltage control is used for dc-link voltage regulation. The experimental results are presented to show the working of the proposed converter.

An Analytical Investigation of DC/DC Power Electronic Converters With Constant Power Loads in Vehicular Power Systems

Abstract: Stability of multi-converter power systems, which exist in advanced more electric vehicles, is of great importance. The stability issue is investigated in this paper, and design considerations and limitations of the methods that stabilize the open-loop converters are presented. By stabilizing the open-loop converter, it is shown that the feedback loop design is usually translated into a conventional feedback design task. The behavior of the unstable converter is also discussed, and a method for decreasing the amplitude of the output voltage oscillations is proposed. The model of a tightly regulated practical converter is presented. This model is used to decide how much damping should be added to make the feeder converter stable. Furthermore, because we have this information about the load converter, the feeder converter can be redesigned so that it does not see the load converter as a constant power load.

Novel Forward–Flyback Hybrid Bidirectional DC–DC Converter

Abstract: This paper presents a novel topology named forward-flyback bidirectional DC-DC converter (BDC), which is a hybrid of forward and flyback converters The windings of forward and flyback transformers are connected in series on the primary side and in parallel on the secondary side The proposed converter has no startup problem and no high voltage spikes on the switches, which otherwise are inherent for current- and voltage-fed-type bidirectional converters It is easy to achieve soft switching by proper control and design The built-in flyback transformer acts as a filter inductor, so the current ripple is smaller than flyback BDCs In this paper, the operation principles and characteristics of the proposed topology are analyzed in detail The advantages aforementioned are verified with experimental results of a 300-W prototype

KY Converter and Its Derivatives

Abstract: In this paper, a voltage-boosting converter, named KY converter (i.e., 1-plus-D converter), is presented. Unlike the traditional nonisolated boost converter, this converter possesses fast load transient responses, which is similar to the buck converter with synchronous rectification. In addition, it possesses nonpulsating output current, thereby not only decreasing the current stress on the output capacitor but also reducing the output voltage ripple. Besides, 1-plus-2D and 2-plus-D converters, derived from the KY converter, are presented based on the same structure but different pulsewidth-modulation control strategies. Above all, the main difference between the KY converter and its derivatives is that the latter ones possess higher output voltages than the former one under the same duty cycle. A detailed description of the KY converter and its derivatives is presented along with some simulated and experimental results.

Photovoltaic-Battery-Powered DC Bus System for Common Portable Electronic Devices

Abstract: Renewable energy sources based on photovoltaic (PV) along with battery-based energy storage necessitate power conditioning to meet load requirements and/or be connected to the electrical grid. The power conditioning is achieved via a dc-dc converter and a DC-AC inverter stages to produce the desired AC source. This is also the case even when the load is of dc type, such as the typical portable electronic devices that require AC adaptors to be powered from the AC mains. The letter presents a hybrid PV-battery-powered dc bus system that eliminates the DC-AC conversion stage, resulting in lower cost and improved overall energy conversion efficiency. It is also shown experimentally that the switching ac adaptors associated with the various commonly used portable electronic devices can be reused with the proposed dc bus system. A novel high-gain hybrid boost-flyback converter is also introduced with several times higher voltage conversion ratio than the conventional boost converter topology. This arrangement results in higher DC bus levels and lower cable conduction losses. Moreover, the voltage stress on the hybrid boost-flyback converter power switch is within half the output voltage. Experimental results taken from a laboratory prototype are presented to confirm the effectiveness of the proposed converter/system.

DC-Voltage-Ratio Control Strategy for Multilevel Cascaded Converters Fed With a Single DC Source

Abstract: Recently, a multilevel cascaded converter fed with a single DC source has been presented. An analysis of the steady-state working limits of this type of converter is presented in this paper. Limits of the maximum output voltage and the minimum and maximum loading conditions for stable operation of the converter are addressed. In this paper, a way to achieve any DC voltage ratio (inside the stable operation area of the converter) between the H-bridges of the single-DC-source cascaded H-bridge converter is presented. The proposed DC-voltage-ratio control is based on a time-domain modulation strategy that avoids the use of inappropriate states to achieve the DC-voltage-ratio control. The proposed technique is a feedforward-modulation technique which takes into account the actual DC voltage of each H-bridge of the converter, leading to output waveforms with low distortion. In this way, the dc voltage of the floating H-bridge can be controlled while the output voltage has low distortion independently of the desired DC voltage ratio. Experimental results from a two-cell cascaded converter are presented in order to validate the proposed DC-voltage-ratio control strategy and the introduced concepts.

Method and apparatus for controlling a hybrid power system

Abstract: The present invention provides a simplified method of controlling power among the various sources and loads in a power system. Power generating sources are each connected to a common DC bus through a converter. The converter selectively transfers energy to the DC bus at a maximum rate or at a reduced rate according to the level of the DC voltage present on the DC bus. At least one storage device is preferably connected to the common DC bus through a power regulator. The power regulator selectively transfers energy to or from the DC bus as a function of DC voltage level present on the DC bus. Further, an inverter may be provided to bidirectionally convert between the DC voltage and an AC voltage for connection to a customer load or the utility grid. Each power conversion device is independently controlled to provide a modular and simplified power control system.

Step-up DC-DC converter for megawatt size applications

Abstract: This study describes a novel DC-DC converter concept which is capable of achieving very high step-up gains with megawatt (MW) level power transfers. The converter is based on two four-switch bridges around a LC circuit and does not utilise iron core transformers. The converter topology is simple and utilises thyristors as switches, with potentially soft switching operation. The high-voltage circuit does not suffer from excessive switch stresses or reverse recovery problems. The analytical modelling indicates that loading, and not the voltage gain, determines the converter size and the control input magnitude. For a given converter, the gain and either loading or operating frequency can be arbitrary selected. The converter shows good controllability with a linear characteristic if the operating frequency is used as the control input. The detailed digital simulation on PSCAD platform confirms conclusions from theoretical analysis on a 5 MW test system, which connects 4 kV source to 80 kV high voltage DC grid. The simulation studies of loses, with realistic internal resistances, indicate that efficiencies of around 95% could be expected.

A New Topology With High Efficiency Throughout All Load Range for Photovoltaic PCS

Abstract: In this paper, a new topology is proposed that can significantly reduce the converter rated power and increase the efficiency of total photovoltaic (PV) system. Since the output voltage of PV module has very wide operating range, in general, the DC/DC converter is used to produce constant high-DC-link voltage for DC/AC inverter. According to the analysis of the proposed topology, only 20% of total PV system power is processed by the DC/DC power conversion stage. The DC/DC power conversion stage used in proposed topology has flat efficiency curve throughout all load range and very high efficiency characteristics. In the proposed topology, because the converter efficiency curve is almost flat throughout all load range, the total system efficiency at light load is dramatically improved. The proposed topology is implemented for 250-kW power conditioning system. This system has only three DC/DC power conversion stage with 24-kW rated power. It is only one-third of total system power. The experimental results show that the proposed topology has good performance.

A Soft-Switching Scheme for an Isolated DC/DC Converter With Pulsating DC Output for a Three-Phase High-Frequency-Link PWM Converter

Abstract: This paper outlines a soft-switching mechanism based on zero-voltage-zero-current-switching (ZVZCS) principle for the front-end isolated DC/DC converter of an isolated three-phase rectifier-type high-frequency-link bidirectional power converter. In conjunction with a back-end DC/AC converter operating with a novel patent-filed hybrid modulation scheme outlined in , , and that reduces the number of hard-switched commutation per switching cycle, the proposed ZVZCS scheme can lead to less overall switching losses than other conventional switching schemes. The proposed ZVZCS scheme is effective for various load conditions, operates seamlessly with a simple active-clamp circuit, and is suitable for applications where low-voltage dc to high-voltage three-phase ac power conversion is required.

Two Types of KY Buck–Boost Converters

Abstract: A novel voltage-bucking/boosting converter, named as KY buck-boost converter (i.e., 2D converter), is presented herein. Unlike the traditional buck-boost converter, this converter possesses fast transient responses, similar to the behavior of the buck converter with synchronous rectification. In addition, it possesses the non-pulsating output current, thereby not only decreasing the current stress on the output capacitor but also reducing the output voltage ripple. Furthermore, it has the positive output voltage, different from the negative output voltage of the traditional buck-boost converter. Above all, there are two types of KY buck-boost converters presented herein. In this paper, the basic operating principles of the proposed converters are first illustrated in detail, and second, some experimental results are offered to verify the effectiveness of the proposed topologies.

A Simple Current-Balancing Converter for LED Lighting

Abstract: In this paper, a current-balancing converter is proposed herein and applied to driving LED strings paralleled, so as to make the required current shared among LED string. There are two stages of the proposed current-balancing converter. The first stage is one buck converter under constant current control and transfers DC current to AC current, whereas the second stage is passive AC-DC rectifiers with front-end current-balancing transformers. Some experimental results, together with a simple mathematical derivation, are provided to verify the proposed scheme.

A Single-Inductor Step-Up DC-DC Switching Converter With Bipolar Outputs for Active Matrix OLED Mobile Display Panels

Abstract: A single-inductor step-up DC-DC switching converter with bipolar outputs is implemented for active-matrix OLED mobile display panels. The positive output voltage is regulated by a boost operation with a modified comparator control (MCC), and the negative output voltage is regulated by a charge-pump operation with a proportional-integral (PI) control. The proposed adaptive current-sensing technique successfully supports the implementation of the proposed converter topology and enables the converter to work in both discontinuous-conduction mode (DCM) and continuous-conduction mode (CCM). In addition, with the MCC method, the converter can guarantee a positive output voltage that has both a fast transient response of the comparator control and a small output voltage ripple of the PWM control. A 4.1 mm2 converter IC fabricated in a 0.5 mum power BiCMOS process operates at a switching frequency of 1 MHz with a maximum efficiency of 82.3% at an output power of 330 mW.

A 0.2 $-\hbox{1.2}$ V DC/DC Boost Converter for Power Harvesting Applications

Abstract: In this paper, a dc/dc converter is presented that can boost very low voltages to the typical supply voltages of current integrated circuits (1.2 V-1.5 V). The converter is based on a new hybrid inductive and capacitive architecture and it is suitable for power harvesting applications too. The measured prototype can supply 1.2 V by converting an input voltage of 200 mV delivered by a thermopile exposed to a 5degC thermal gradient. A chip was designed and fabricated using a United Microelectronics Corp. (UMC) 180-nm low-threshold CMOS process. Measurements on the chip confirm the validity of the design.

A cost optimized battery management system with active cell balancing for lithium ion battery stacks

Abstract: A method for active cell balancing of lithium ion battery stacks is presented. Balancing the charge of cells in a multi-cell lithium ion battery stack is often employed to guard against damage and improve the lifetime of the battery. Battery stacks which are in production today largely use a passive cell balancing method, which dissipates charge through a resistor, as heat. The method described uses a flyback converter to pass charge from cell to cell with low losses and only a small cost increase from a typical passive system.

Ac-ac dual active bridge converter for solid state transformer

Abstract: This work investigates the application of an ac-ac dual active bridge converter for solid state transformer. The proposed converter topology consists of two active H-bridges and one high frequency transformer. Four-quadrant switch cells are used to ensure bi-directional power flow. The advantages of direct ac-ac conversion include fewer power conversion stages and minimized passive components. The ac-ac dual active bridge converter is controlled with phase shift modulation. Operating modes for both power flow directions are described and zero-voltage switching criteria are analyzed. One design example is presented. Simulation results verify the theoretical analysis.

Single-Stage AC/DC Boost–Forward Converter With High Power Factor and Regulated Bus and Output Voltages

Abstract: Unlike existing single-stage AC/DC converters with uncontrolled intermediate bus voltage, a new single-stage AC/DC converter achieving power factor correction (PFC), intermediate bus voltage output regulation, and output voltage regulation is proposed. The single-power-stage circuit is formed by integrating a boost PFC converter with a two-switch-clamped forward converter. The current stress of the main power switches is reduced due to separated conduction period of the two source currents flowing through the power switch. A dual-loop peak-current-mode controller is proposed to achieve PFC and ensure independent bus voltage and output voltage regulations. Experimental results on a 24-V/100-W hardware prototype are given to confirm the theoretical analysis and performance of the proposed converter. The converter has conversion efficiency ranging from 86% to 92% at full-load condition.

Forward-flyback converter with active-clamp circuit

Abstract: The present invention discloses a forward-flyback converter with active-clamp circuit. The secondary side of the proposed converter is of center-tapped configuration to integrate a forward circuit and a flyback circuit. The flyback sub-circuit operating continuous conduction mode is employed to directly transfer the reset energy of the transformer to the output load. The forward sub-circuit operating discontinuous conduction mode can correspondingly adjust the duty ratio with the output load change. Under the heavy load condition, the mechanism of active-clamp flyback sub-circuit can provide sufficient resonant current to facilitate the parasitic capacitance of the switches to be discharged to zero. Under the light load condition, the time interval in which the resonant current turns from negative into positive is prolonged to ensure zero voltage switching function. Meanwhile, the flyback sub-circuit wherein the rectifier diode is reverse biased is inactive in order to further reduce the power losses.

High step-up resonant push-pull converter with high efficiency

Abstract: A high-efficient current-fed push-pull converter is proposed for high output voltage applications supplied by low-voltage and high-current sources such as fuel cells and solar cells. The proposed converter conserves inherent advantages of a conventional current-fed push-pull converter such as low input current stress and high-voltage conversion ratio. The converter employs a voltage-doubler rectifier in order to remove the reverse-recovery problem of the output rectifying diodes and to provide much higher voltage conversion ratio. Additionally, by allowing the duty ratio < 0.5, the converter operates in wider input voltage range, and the ripple current of a boost inductor is reduced, compared with the conventional one. Moreover, as the duty ratio approaches 0.5, the ripple of the inductor current moves in close to zero. The operation of the proposed converter is analysed and experimental results obtained from a prototype verify the analysis. The prototype was implemented for an application requiring a 1.5 kW output power, input voltage range varying from 35 to 60 V, and 350 V output voltage. Experiment results show that minimum efficiency at full load is about 95.5%.

Power factor corrected 3-phase Ac-dc power converter using natural modulation

Abstract: A 3-phase pfc 100% duty-ratio buck converter and a 3-phase 0% duty-ratio boost converter can be used in parallel with their outputs in series to greatly reduce the ripple voltage in the output. They can also be used in series with their outputs in parallel to greatly reduce the ripple current in the output. A 3-phase 0% duty-ratio boost converter having isolated primary circuits for each phase is used when the inputs are in series.

DC bus voltage control for two stage solar converter

Abstract: Systems, methods, and apparatus for supplying AC power to an AC power grid from a DC power source, such as a photovoltaic (PV) array are disclosed. The systems and methods can include a converter coupled to the DC power source that provides DC power to a DC bus at a DC bus voltage. The systems and methods can further include an inverter coupled to the DC bus for converting the DC power of the DC bus to an output AC power. The systems and methods can further include a control system configured to regulate the DC bus voltage of the DC bus to operate at a variable DC bus voltage setpoint. The control system can adjust the DC bus voltage setpoint based at least in part on the DC bus voltage and the output AC current of the inverter.

A Three-Level Resonant Single-Stage Power Factor Correction Converter: Analysis, Design, and Implementation

Abstract: This paper presents a new single-stage power factor correction AC/DC converter based on a three-level half-bridge resonant converter topology. The proposed circuit integrates the operation of the boost power factor preregulator and the three-level resonant DC/DC converter. A variable-frequency asymmetrical pulsewidth modulation controller is proposed for this converter. This control technique is based on two integrated control loops: the output voltage is regulated by controlling the switching frequency of the resonant converter, whereas the DC-bus voltage and input current are regulated by means of duty cycle control of the boost part of the converter. This provides a regulated output voltage and a nearly constant DC-bus voltage regardless of the loading condition; this, in turn, allows using smaller switches and consequently having a lower on resistance helping to reduce conduction losses. Zero-voltage switching is also achieved for a wide range of loading and input voltage. The resulting circuit, therefore, has high conversion efficiency making it suitable for high-power wide-input-voltage-range applications. The effectiveness of this method is verified on a 2.3-kW 48-V converter with input voltage (90-265 Vrms).

Single-Switch Quasi-Resonant Converter

Abstract: A single-switch quasi-resonant converter is proposed to obtain high efficiency. Using a variable switching frequency control, this converter is continuously operated at the critical conduction mode for soft switching of the power semiconductor switch. By the resonance, the proposed converter reduces the turn-on loss of the switch without additional active switches and alleviates the reverse-recovery losses of the rectifying diodes. Furthermore, the voltage stress of the rectifying diodes due to the output series resonant circuit is clamped to the output voltage. Experimental results for the 48-V/160-W converter at the variable switching frequency are obtained to show the performance of the proposed converter.