Showing papers on "Buck–boost converter published in 2002"

Z-source inverter

Abstract: This paper presents an impedance-source (or impedance-fed) power converter (abbreviated as Z-source converter) and its control method for implementing DC-to-AC, AC-to-DC, AC-to-AC, and DC-to-DC power conversion. The Z-source converter employs a unique impedance network (or circuit) to couple the converter main circuit to the power source, thus providing unique features that cannot be obtained in the traditional voltage-source (or voltage-fed) and current-source (or current-fed) converters where a capacitor and inductor are used, respectively. The Z-source converter overcomes the conceptual and theoretical barriers and limitations of the traditional voltage-source converter (abbreviated as V-source converter) and current-source converter (abbreviated as I-source converter) and provides a novel power conversion concept. The Z-source concept can be applied to all DC-to-AC, AC-to-DC, AC-to-AC, and DC-to-DC power conversion. To describe the operating principle and control, this paper focuses on an example: a Z-source inverter for DC-AC power conversion needed in fuel cell applications. Simulation and experimental results are presented to demonstrate the new features.

LLC resonant converter for front end DC/DC conversion

Abstract: A new LLC resonant converter is proposed for front end DC/DC conversion in a distributed power system. Three advantages are achieved with this resonant converter. First, ZVS turn on and low turn off current of MOSFETs are achieved. The switching loss is reduced so we can operate the converter at higher switching frequency. The second advantage is that with this topology, we can optimize the converter at high input voltage. Finally, with this topology, we can eliminate the secondary filter inductor, so the voltage stress on the secondary rectifier will be limited to two times the output voltage, better rectifier diodes can be used and secondary conduction loss can be reduced. The converter utilizes leakage and magnetizing inductance of a transformer. With magnetic integration concept, all the magnetic components can be built in one magnetic core. The operation and characteristic of this converter is introduced and efficiency comparison between this converter and a conventional PWM converter is given which shows a great improvement by using this topology.

Multi-input DC/DC converter based on the multiwinding transformer for renewable energy applications

Abstract: A multi-input DC/DC power converter based on the flux additivity is proposed in this paper. Instead of combining input DC sources in the electric form, the proposed converter combines input DC sources in magnetic form by adding up the produced magnetic flux together in the magnetic core of the coupled transformer. With the phase-shifted pulsewidth-modulation (PWM) control, the proposed converter can draw power from two different DC sources and deliver it to the load individually and simultaneously. The operation principle of the proposed converter has been analyzed in detail. The output voltage regulation and power flow control can be achieved by the phase-shifted PWM control. A prototype converter with two different DC voltage sources has been successfully implemented. Computer simulations and hardware experimental results are presented to verify the performance of the proposed multi-input DC/DC power converter.

Analysis and design considerations of a load and line independent zero voltage switching full bridge DC/DC converter topology

Abstract: The analysis and design of a zero voltage switching (ZVS) full bridge DC/DC power converter topology is presented in this paper. The converter topology presented here employs an asymmetrical auxiliary circuit consisting of a few passive components. With this auxiliary circuit, the full bridge converter can achieve ZVS independent of line and load conditions. The operating principle of the circuit is demonstrated, and the steady state analysis is performed. Based on the analysis, a criterion for optimal design is given. Experiment and simulation on a 350-400 V to 55 V, 500 W prototype converter operated at 100 kHz verify the design and show an overall efficiency of greater than 97% at full load.

A new matrix converter motor (MCM) for industry applications

Abstract: The trend in electrical drives is to integrate the frequency converter, the electrical motor, and even the gear or the pump into a single unit, in order to reduce the costs, to increase the overall efficiency and the equipment reliability. This paper presents the first integrated regenerative frequency converter motor for industry applications, based on a matrix converter topology. The low volume, the sinusoidal input current, the bidirectional power flow, and the lack of the bulky and limited-lifetime electrolytic capacitors recommend this topology for this application. This paper shows how the matrix converter disadvantages-the lack of bidirectional power devices, the lower voltage transfer ratio, and the overvoltages caused by the input filter during power-up-that have delayed the industrial implementation have been overcome. In order to demonstrate the validity of the solution, a 4-kW matrix converter motor prototype is built using a standard frequency converter motor enclosure for testing the requirements for an industrial drive. The tests demonstrate the good performance of the drive.

A magnetic-less DC-DC converter for dual voltage automotive systems

Abstract: The automotive industry is moving toward 42 volt to meet the more electric needs. Several dual voltage (42 and 14 volt) architectures have been proposed for the transition and accommodation of 14-volt loads. A DC-DC converter that connects the 42 and 14 volt architectures is one key device in any dual voltage architecture. This paper presents a compact, efficient, magnetic-less bi-directional DC-DC converter for dual voltage (42/14 Volt) automotive systems. The DC-DC converter is based on the generalized multilevel converter topology having the ability to balance battery voltages, emit zero or low electromagnetic interference (EMI), and have low cost by using low-voltage metal oxide field effect transistors (MOSFETs). The main circuit of the DC-DC converter is analyzed and its control scheme is presented in the paper. A self-powered gate drive circuit is developed for the DC-DC converter to reduce costs, signal connections, and circuit complexity. A prototype has been built and experimental results are presented.

A new ZVT-PWM DC-DC converter

Abstract: In this paper, a new active snubber cell that overcomes most of the drawbacks of the normal "zero voltage transition-pulse width modulation" (ZVT-PWM) converter is proposed to contrive a new family of ZVT-PWM converters. A converter with the proposed snubber cell can also operate at light load conditions. All of the semiconductor devices in this converter are turned on and off under exact or near zero voltage switching (ZVS) and/or zero current switching (ZCS). No additional voltage and current stresses on the main switch and main diode occur. Also, the auxiliary switch and auxiliary diodes are subjected to voltage and current values at allowable levels. Moreover, the converter has a simple structure, low cost, and ease of control. A ZVT-PWM boost converter equipped with the proposed snubber cell is analyzed in detail. The predicted operation principles and theoretical analysis of the presented converter are verified with a prototype of a 2 kW and 50 kHz PWM boost converter with insulated gate bipolar transistor (IGBT). In this study, a design procedure of the proposed active snubber cell is also presented. Additionally, at full output power in the proposed soft switching converter, the main switch loss is about 27% and the total circuit loss is about 36% of that in its counterpart hard switching converter, and so the overall efficiency, which is about 91% in the hard switching case, increases to about 97%.

Integrated magnetic for LLC resonant converter

Abstract: A new LLC resonant converter is proposed for front end DC/DC conversion in a distributed power system. This converter shows some potential benefits in this application. This paper proposes several integrated magnetic designs for LLC resonant converter. This converter has three magnetic components. With magnetic integration, first, a number of components can be reduced; secondly, flux ripple cancellation is achieved so that core loss is reduced. From these benefits, higher power density can be achieved. In design of the integrated magnetic structure for LLC resonant converter, a general model of four winding integrated magnetic structure is derived which can be used to derive integrated magnetic structure for different topologies. Finally, the test result is shown.

Novel zero-voltage and zero-current-switching (ZVZCS) full-bridge PWM converter using coupled output inductor

Abstract: A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge pulse-width-modulated (PWM) converter is proposed to improve the previously proposed ZVZCS full-bridge PWM converters. By employing a simple auxiliary circuit with neither lossy components nor active switches, soft-switching of the primary switches is achieved. The proposed converter has many advantages such as simple auxiliary circuit, high efficiency, low voltage stress of the rectifier diode and self-adjustment of the circulating current, which make the proposed converter attractive for the high voltage and high power applications. The principles of operation and design considerations are presented and verified on the 4 kW experimental converter operating at 80 kHz.

A new soft switching technique for buck, boost and buck-boost converters

Abstract: A new soft switching technique for buck, boost and buck-boost converters using a coupled inductor is proposed in this paper. The principles of operation of these converters are analyzed in detail. An additional winding is added on the same core of the main inductor for the purpose of commutation. By using hysteresis current control, zero voltage switching (ZVS) conditions are ensured over wide load range. The main inductor current is kept in continuous conduction mode (CCM) with small ripple, which allows high output power and small filter parameters. Also, the switching frequency is kept constant when load changes. Prototypes of buck, boost, and buck-boost converters have been built to verify the proposed concept. The experimental results are presented and they verify the analysis.

A new green power inverter for fuel cells

Abstract: This paper presents a new grid connected inverter for fuel cells. It consists of a two stage power conversion topology. Since the fuel cell operates with a low voltage in a wide voltage range (25 V-45 V) this voltage must be transformed to around 350-400 V in order to invert this DC power into AC power to the grid. The proposed converter consists of an isolated DC-DC converter cascaded with a single phase H-bridge inverter. The DC-DC converter is a current-fed push-pull converter. A new dedicated voltage mode startup procedure has been developed in order to limit the inrush current during startup. The inverter is controlled as a power factor controller with resistor emulation. Experimental results of converter efficiency, grid performance and fuel cell response are shown for a 1 kW prototype. The proposed converter exhibits a high efficiency in a wide power range (higher than 92%) and the inverter operates with a near unity power factor and a low current THD.

Multiple energy-source power converter system

Abstract: A flexible integrated power converter system that connects various types of electrical power sources together and supplies a defined type of electrical energy to a load, such as a standard household mains voltage supply, is provided. Each of the electrical power sources is electrically isolated from the load, as well as each other. A respective input converter is coupled to each power source. Each input converter may include a small high-frequency transformer driven by an efficient soft-switched dc-dc converter. The voltages produced by each of the input converters are combined in parallel and delivered to a single output inverter. The output inverter converts the combined voltages to an ac voltage that may be delivered to a load.

DC-DC converter and bi-directional DC-DC converter and method of controlling the same

Abstract: A DC—DC converter has converter circuit portions 11 and 12, transformers Tr1 and Tr2, and rectifier circuit portions 21 and 22. Two sets of converter circuit portions 11 and 12 respectively include two pairs of switching elements Q1 to Q4, and two pairs of switching elements Q5 to Q8 connected in full bridge configuration, series capacitors C1 and C2 are inserted and connected between the converter circuit portions 11 and 12 and the transformers Tr1 and Tr2 respectively. The switching phase of one switching element Q4 or Q8 is shifted by a 1/3n period from the switching phase of the other switching element Q1 or Q5 in the pair of switching elements. The switching phases of corresponding switching elements Q1 and Q5 in the converter circuit portions 11 and 12 are shifted by a 1/2n period from each other.

A novel tri-state boost converter with fast dynamics

Abstract: A challenging problem in the design of boost converters operating in continuous-conduction mode is posed by the dynamically shifting right-half-plane (RHP) zero in the converter's small-signal control-to-output transfer function. The paper proposes a novel tri-state boost converter without such a zero in the transfer function. The additional degree of freedom introduced in the converter in the form of a freewheeling interval has been exploited through an easy control technique to achieve this elimination. The absence of the RHP zero allows the control scheme to achieve larger bandwidth under closed-loop conditions, resulting in fast response. Analytical, simulation and experimental results of the tri-state boost converter have been presented and compared with those of the classical boost converter both under open-loop and under closed-loop operating conditions. The results clearly demonstrate the superior dynamic performance of the proposed converter. The proposed converter can be used in applications wherever fast-response boost action is needed.

High-voltage multilevel converter with regeneration capability

Abstract: This paper presents a multilevel converter with regeneration capability. The converter uses several power cells connected in series, each working with reduced voltage and with an active front end at the line side. This paper presents the following: (1) the control method of each cell; (2) the use of phase-shifting techniques to reduce the current and voltage distortion; and (3) criteria to select the connection of the cells. The converter generates almost sinusoidal currents at the load and at the input and works with very high power factor.

Frequency converter for different mains voltages

Abstract: The invention is directed to controlling an electric motor by means of a frequency converter. The frequency converter can be connected to one of several different mains voltages. According to the present invention, the maximum output power of the frequency converter, is limited when the actual mains voltage is lower than the maximum nominal mains voltage, for which the frequency converter is designed, and during the limitation the frequency converter controls the speed of the motor within a power range up to a limited maximum output power. This gives a genuine multi-voltage unit, which can be connected to a wide range of mains voltages.

Dual input AC and DC power supply having a programmable DC output utilizing single-loop optical feedback

Abstract: A dual input AC/DC power converter ( 10 ) having dual inputs ( 12,14 ) adapted to receive both an AC and DC input and provide a selectable DC voltage output ( 16 ) and a second DC output ( 18 ). The dual input AC/DC power converter ( 10 ) comprises a power converter circuit ( 20 ) having an AC-to-DC converter ( 22 ), a DC-to-DC booster converter ( 24 ), a feedback circuit ( 26 ), a filter circuit ( 25 ) and a DC-to-DC buck converter ( 28 ). Advantageously, the power converter ( 10 ) resolves many of the system management problems associated with carrying all of the different interface components necessary to power a wide variety of mobile products from either an AC or DC power supply. In addition, the feedback circuit ( 26 ) comprises single feedback loop having stacked photocouplers, one (PH 1 ) controlling the AC-to-DC converter ( 22 ) and the other (PH 3 ) controlling the DC-to-DC booster converter ( 24 ), to select the overall DC output voltage.

Full bridge ZCS PWM converter for high-voltage high-power applications

Abstract: This paper presents a comprehensive study of a full bridge (FB) zero-current switched (ZCS) PWM converter which is suitable for high-voltage and high-power DC application that achieves ZCS for all active switches, and zero-voltage-switched (ZVS) operation for all diodes on the high voltage side. The given converter utilizes component parasitic parameters, particularly for the high-voltage transformer, and employs fixed-frequency phase-shift control to implement soft-switching commutations. Detailed steady state analysis of the converter power stage is presented for the first time and the major features of the converter's power stage are discussed. Small-signal characteristics are also presented and accompanied by a discussion of the controller design and implementation. A design example is also presented based on the steady state analysis and is validated by simulation. Theoretical and simulated results are in good agreement.

Adaptive off-time control for variable-frequency, soft-switched flyback converter at light loads

Abstract: The soft switching of a flyback converter can be achieved by operating the circuit in the critical conduction mode. However, the critical-mode operation at light loads cannot be maintained due to a very high switching frequency and the loss of the output voltage regulation. A control which regulates the output down to the zero load and maintains soft switching at light loads is proposed. The proposed control scheme was implemented in the 380 V/19 V, 65 W flyback DC/DC converter.

Multiple output power supply having soft start protection for load over-current or short circuit conditions

Abstract: A protection circuit for a multiple output switching mode power converter protects against an over-current or short circuit failure condition. The protection circuit activates the soft-start circuit of the PWM control circuit upon detection of the over-current or short circuit condition. The soft-start circuit then shuts off operation of the power converter and restarts the power converter after a period of time defined by the soft-start circuit. The protection circuit is effective with any type of power converter topology (e.g., buck, boost, flyback, and forward converter), isolated or non-isolated, having dual or multiple outputs.

Power converter circuit arrangement for generators with dynamically variable power output

Abstract: A power converter circuit for wind power devices which feed into a high-voltage grid consisting of a power converter circuit arrangement to transform the variable frequency and variable voltage alternating current generated in the AC voltage generator into DC. The DC is chopped to again produce AC but with a fixed frequency and voltage. The power converter consists of a cascaded serial arrangement of several power converter cells. The power converter cells are made dynamically active or inactive by the master control unit, depending on the power being generated by the AC voltage generator. Each phase of each power converter cell supplies a primary winding of an output transformer.

Multi-phase converter with balanced currents

Abstract: A multi-phase DC/DC converter having an output voltage and including a plurality of converter channels. Each converter channel includes a converter channel input and a converter channel output. Each converter channel is configured for generating a converter channel current and for adjusting said converter channel current in response to a control signal electrically connected to each converter channel input. A control circuit generates an error signal representative of a comparison of the converter output voltage to a reference voltage. The control circuit includes a plurality of control circuit channels, each of which correspond to a converter channel. Each control circuit channel generates a channel current signal representative of a corresponding converter channel current, and generates a differential channel current signal representative of a comparison of the channel current signal to an average current signal. The average current signal is representative of an overall average current for the converter channels. Each control circuit channel generates a differential error signal representative of a comparison of the error signal to the differential channel current signal. Each control circuit channel includes a pulse width modulator having a ramp input and a control input. The control input is electrically connected to the differential error signal. The pulse width modulator generates the control signal based upon the differential error signal. The control signal is electrically coupled to a corresponding converter channel input. The control circuit generates the average current signal.

New two-inductor boost converter with auxiliary transformer

Abstract: A new, two-inductor, two-switch boost converter topology and its variations suitable for applications with a large difference between the input and output voltage are described. The output voltage regulation of the proposed converters is achieved in a wide load and input-voltage range with constant-frequency control by employing an auxiliary transformer that couples the current paths of the two boost inductors.

Photovoltaic grid-connected inverter using two-switch buck-boost converter

Abstract: This paper presents a two-stage photovoltaic grid-connected inverter. The first stage is a two-switch buck-boost circuit that performs various functions; tracking a maximum power point of the photovoltaic array and controlling current using fixed frequency current mode control technique; as well as reforming a direct current waveform to an absolute sinusoidal waveform. The second stage is a H-bridge switch that converts an absolute sinusoidal waveform to a sinusoidal waveform with a low harmonic distortion current and connected to utility. The system configuration is reliable using a single-chip DSP controller. Experimental results satisfy with simulation.

Accelerated commutation for passive clamp isolated boost converters

Abstract: An efficient and cost effective bidirectional DC/DC converter reduces switch voltage stress via accelerated commutation allowing use of a low-cost passive clamp circuit in boost mode. The converter includes a primary circuit, transformer and secondary circuit. The primary circuit takes the form of a “full bridge converter,” a “push-pull converter,” or an “L-type converter.”. The primary circuit may include a dissipator such as a snubber circuit or small buck converter. A secondary side of the transformer is momentarily shorted by the secondary circuit by, for example, turning on at least two switches in the secondary circuit simultaneously for a minimal calibratable period when a pair of primary circuit controllers turn off to protect the primary circuit switches from voltage spikes during switching conditions.

Bi-directional regulator/converter with buck/boost by fuzzy logic control

Abstract: An interface between software and hardware, as well as a fuzzy logic control algorithm, for controlling a DC-DC converter or an AC-DC or DC-AC inverter are provided. A control circuit receives commands from a control logic to operate a converter or inverter in various operation modes. Control software inputs can be translated into signals to operate the converter or inverter. Control variables in the control software can be configured to operate under various control modes. If the converter or inverter cannot simultaneously meet the demands placed on two or more variables, the control logic can use prioritization to choose a more important constraint.

Analysis and design of asymmetrical half bridge flyback converter

Abstract: The detailed circuit behaviour of the asymmetrical half bridge flyback converter is analysed. The specific relationships between the duty cycle and the different types of energy in the energy storage elements are thoroughly investigated. From the analytical results, the maximum duty cycle is not bounded by 50%, which means that the converter can now be optimally used for the different applications. The zero voltage switching (ZVS) conditions of the power switches are derived. Mathematical equations and design considerations are also given. According to the presented design guidelines, the ZVS operations of the power switches can be maintained from no-load to full-load conditions. A 5V/20A prototype has been built to verify the analytical results under real life conditions.

A megahertz switching DC/DC converter using FeBN thin film inductor

Abstract: A dual spiral sandwiched thin film inductor with a dimension of 5 mm /spl times/ 5 mm was fabricated by a LIGA-like micromachined process. FeBN magnetic films were used as a core material. The inductance and quality factor value of the inductor were measured approximately 1 /spl mu/H and 4 up to 5 MHz, respectively. Using the FeBN film inductor, a hybrid dc/dc converter (15 mm /spl times/ 12 mm /spl times/ 1.5 mm) was designed and fabricated. The circuit topology of the converter was a zero voltage switching clamp voltage (ZVS-CV) buck converter. An input of 3.6 V was bucked to 2.7 V at a switching frequency of 1.8 MHz. The maximum power was 1.5 W. The measured efficiency of the buck converter reached a maximum value of 80% and kept stable up to 300 mA of load currents at 1.8 MHz.

Method for regulating an inverter system

Abstract: The invention describes a method of regulating a rectifier inverter system ( 1 ), whereby electrical power is generated and/or supplied via a power source ( 6 ) and is transmitted from at least one d.c.-to-d.c. converter ( 3 ) to an intermediate circuit ( 4 ), from where it is fed via a d.c.-to-a.c. converter ( 5 ) to an alternating voltage supply ( 8 ) and/or delivered to a consumer. The d.c.-to-d.c. converter ( 3 ) is regulated in such a way that a virtually constant current flow is applied from the input of the d.c.-to-d.c. converter ( 3 ), in other words from the power source ( 6 ), to the output of the d.c.-to-d.c. converter ( 3 ), in other words the intermediate circuit ( 4 ), during a pre-settable period irrespective of the power drawn off from the intermediate circuit ( 4 ), whereas during this same period power is drawn off from the intermediate circuit ( 4 ) to feed it to the alternating voltage supply ( 8 ) or deliver it to the consumer. A controller or a control system of the d.c.-to-d.c. converter ( 3 ), in particular a desired value for regulating the current flow through the d.c.-to-d.c. converter ( 3 ), is re-set whenever the period elapses.

A new ZVS-PWM full-bridge converter

Abstract: A full-bridge converter which employs a coupled inductor to achieve zero-voltage switching of the primary switches in the entire line and load range is described. Because the coupled inductor does not appear as a series inductance in the load current path, it does not cause a loss of duty cycle or severe voltage ringing across the output rectifier. The operation and performance of the proposed converter is verified on a 670-W prototype.