Showing papers on "Forward converter published in 2003"

Voltage converter control apparatus, voltage conversion method, storage medium, program, drive system, and vehicle having the drive system

Abstract: By using a target voltage Vc* of a capacitor connected to the output side of a DC/DC converter and a voltage Vb of a battery connected to the input side of the DC/DC converter, a duty ratio D (Vb/Vc*) as a drive instruction of the DC/DC converter is calculated (S100, S102). By using the voltage Vb, the electromotive force Vbo of the battery, and the charge/discharge current Ib of the battery, an internal resistance Rb ((Vbo - Vb)/Ib) is calculated (S104). According to the internal resistance Rb and the electromotive force Vbo, the current value (value Vbo/2Rb) when the battery output becomes maximum is set as the upper limit value of the optimal current range IR (S106). the DC/DC converter is driven/controlled by limiting the duty ratio D so that the current Ib is within the range of the optimal current range IR (S108, S110, S112). Thus, it is possible to appropriately convert the battery input voltage.

Step-up switching-mode converter with high voltage gain using a switched-capacitor circuit

Abstract: A new circuit is proposed for a steep step-up of the line voltage. It integrates a switched-capacitor (SC) circuit within a boost converter. An SC circuit can achieve any voltage ratio, allowing for a boost of the input voltage to high values. It is unregulated to allow for a very high efficiency. The boost stage has a regulation purpose. It can operate at a relatively low duty cycle, thus avoiding diode-reverse recovery problems. The new circuit is not a cascade interconnection of the two power stages; their operation is integrated. The simplicity and robustness of the solution, the possibility of getting higher voltage ratios than cascading boost converters, without using transformers with all their problems, and the good overall efficiency are the benefits of the proposed converter.

DC bus voltage control for a distributed power system

Abstract: This paper addresses voltage control of distributed DC power systems. DC power systems have been discussed as a result of the introduction of renewable, small-scale power generation units. Also, telecommunication power systems featuring UPS properties might benefit from a broader introduction of DC power systems. Droop control is utilized to distribute the load between the source converters. In order to make the loading of the source converters equal, in per unit, the voltage control algorithm for each converter has to be designed to act similar. The DC side capacitor of each converter, needed for filtering, is also determined as a consequence. The root locus is investigated for varying DC bus impedance. It is found that the risk of entering converter over-modulation is a stronger limitation than stability, at least for reasonable DC bus cable parameters. The stationary and dynamic properties during load variations are also investigated.

Positive output super-lift converters

Abstract: The voltage lift technique has been successfully employed in design of DC/DC converters, e.g., four series Luo converters. However, the output voltage increases in arithmetic progression. This paper introduces a novel approach-super-lift technique that implements the output voltage increasing in geometric progression. It effectively enhances the voltage transfer gain in power law.

Control of a multilevel converter using resultant theory

Abstract: In this work, a method is given to compute the switching angles in a multilevel converter to produce the required fundamental voltage while at the same time cancel out specified higher order harmonics. Specifically, a complete analysis is given for a seven-level converter (three dc sources), where it is shown that for a range of the modulation index m/sub I/, the switching angles can be chosen to produce the desired fundamental V/sub 1/=m/sub I/(s4V/sub dc///spl pi/) while making the fifth and seventh harmonics identically zero.

Multi-mode renewable power converter system

Abstract: A multi-mode renewable power converter system is disclosed. The system includes a control unit, a boost converter, an inverter and optional bi-directional charger, wherein the boost converter converts DC output of a solar cell or a renewable source to high DC bus voltage, and the inverter converts this DC bus voltage to an AC output. This power converter can be used to support standalone load or grid-connected system with a dynamic maximum power point tracking (MPPT) circuit. The MPPT circuit detects the current and voltage from the solar cell and indicates to the inverter to provide power to the load connected. When the optional bi-directional charger is installed, the MPPT signal is also fed to this charger to make the power efficiency maximized for the system.

Advanced DC/DC Converters

Abstract: INTRODUCTION Historical Review Multiple Quadrant Choppers Pump Circuits Development of DC/DC Conversion Technique Categorize Prototypes and DC/DC Converters Family Tree VOLTAGE-LIFT CONVERTERS Introduction Seven Self-Lift Converters Positive Output Luo-Converters Negative Output Luo-Converters Modified Positive Output Luo-Converters Double Output Luo-Converters POSITIVE OUTPUT SUPER-LIFT LUO-CONVERTERS Introduction Main Series Additional Series Enhanced Series Re-Enhanced Series Multiple-Enhanced Series Summary of Positive Output Super-Lift Luo-Converters Simulation Results Experimental Results NEGATIVE OUTPUT SUPER-LIFT LUO-CONVERTERS Introduction Main Series Additional Series Enhanced Series Re-Enhanced Series Multiple-Enhanced Series Summary of Negative Output Super-Lift Luo-Converters Simulation Results Experimental Results POSITIVE OUTPUT CASCADE BOOST CONVERTERS Introduction Main Series Additional Series Double Series Triple Series Multiple Series Summary of Positive Output Cascade Boost Converters Simulation and Experimental Results NEGATIVE OUTPUT CASCADE BOOST CONVERTERS Introduction Main Series Additional Series Double Series Triple Series Multiple Series Summary of Negative Output Cascade Boost Converters Simulation and Experimental results MULTIPLE-QUADRANT OPERATION LUO-CONVERTERS Introduction Circuit Explanation Mode A (Quadrant I Operation) Mode B (Quadrant II Operation) Mode C (Quadrant III Operation) Mode D (Quadrant IV Operation) Simulation Results Experimental Results Discussion SWITCHED-COMPONENT CONVERTERS Introduction A Two-Quadrant SC DC/DC Converter Four-Quadrant Switched Capacitor DC/DC Converter Switched Inductor Four-Quadrant DC/DC Converter POSITIVE OUTPUT MULTIPLE-LIFT PUSH-PULL SWITCHED-CAPACITOR CONVERTERS Introduction Main Series Additional Series Enhanced Series Re-enhanced Series Multiple-Enhanced Series Theoretical Analysis Summary of this Technique Simulation Results Experimental Results NEGATIVE OUTPUT MULTIPLE-LIFT PUSH-PULL SWITCHED-CAPACITOR CONVERTERS Introduction Main Series Additional Series Enhanced Series Re-Enhanced Series Multiple-Enhanced Series Summary of this Technique Simulation and Experimental Results MULTIPLE-QUADRANT SOFT-SWITCHING CONVERTERS Introduction Multiple-Quadrant DC/DC ZCS Quasi-Resonant Converters Multiple-Quadrant DC/DC ZVS Quasi-Resonant Converter Multiple-Quadrant Zero-Transition DC/DC Converters SYNCHRONOUS RECTIFIER DC/DC CONVERTERS Introduction Flat Transformer Synchronous Rectifier Converter Active Clamped Synchronous Rectifier Converter Double Current Synchronous Rectifier Converter Zero-Current-Switching Synchronous Rectifier Converter Zero-Voltage-Switching Synchronous Rectifier Converter MULTIPLE ENERGY-STORAGE ELEMENTS RESONANT POWER CONVERTERS Introduction Bipolar Current and Voltage Source A 2-Element RPC Analysis P-CLL CURRENT SOURCE RESONANT INVERTER Introduction Mathematic Analysis Simulation Results Discussion CASCADE DOUBLE G-CL CURRENT SOURCE RESONANT INVERTER Introduction Mathematic Analysis Simulation Results Experimental Results Discussion CASCADE REVERSE DOUBLE G-LC RESONANT POWER CONVERTER Introduction Steady-State Analysis of Cascade Reverse Double G-LC RPC Resonance Operation and Modeling Small-Signal Modeling of Cascade Reverse Double G-LC RPC Discussion DC ENERGY SOURCES FOR DC/DC CONVERTERS Introduction Single-Phase Half-Wave Diode Rectifier Single-Phase Bridge Diode Rectifier Three-Phase Half-Bridge Diode Rectifier Three-Phase Full-Bridge Diode Rectifier with Resistive Load Thyrister Rectifiers CONTROL CIRCUIT. EMI AND APPLICATIONS EXAMPLES OF DC/DC CONVERTERS Introduction Luo-Resonator EMI, EMS and EMC Some DC/DC Converter Applications

An interleaved boost DC-DC converter with large conversion ratio

Abstract: A new PWM dc-dc converter is introduced in which large voltage step-up ratios can be achieved without high duty-cycle, with low voltage and current stress and without transformer. The proposed circuit is an extension of the boost interleaved converter, incorporating a multistage capacitor multiplier. A simple nondissipative snubber can be used reducing the reverse recovery current of the diodes and also obtaining low turn-on and turn-off losses. The modularity of the structure allows the increment of the current, voltage and power levels, using the same range of components and maintaining high efficiency, only increasing the number of series and parallel stages. The paper gives a theoretical analysis, and experimental data on a 400 W example that was built and tested: 24 Vdc input, 200 Vdc output, and 40 kHz switching frequency. The measured performance agreed well with the theoretical predictions and the measured efficiency obtained is equal to 95% at full load.

DC Bus Voltage Control for a Distributed Power System

Abstract: This paper addresses voltage control of distributed dc power systems. DC power systems have been discussed as a re- sult of the introduction of renewable, small-scale power generation units. Also, telecommunication power systems featuring UPS prop- erties might benefit from a broader introduction of dc power sys- tems. Droop control is utilized to distribute the load between the source converters. In order to make the loading of the source con- verters equal, in per unit, the voltage control algorithm for each converter has to be designed to act similar. The dc side capac- itor of each converter, needed for filtering, is also determined as a consequence. The root locus is investigated for varying dc bus impedance. It is found that the risk of entering converter over-mod- ulation is a stronger limitation than stability, at least for reasonable dc bus cable parameters. The stationary and dynamic properties during load variations are also investigated. The paper starts with an overview of the simulation model. Then the dc bus voltage controller utilized in the analysis is introduced. The simulation model parameters are given and the controller parameters are discussed. The root locus dependency

Primary-side controlled flyback power converter

Abstract: The present invention provides a primary-side flyback power converter that supplies a constant voltage output and a constant current output. To generate a well-regulated output voltage under varying load conditions, a PWM controller is included in the power converter in order to generate a PWM signal controlling a switching transistor in response to a flyback voltage sampled from a first primary winding of the power supply transformer. Several improvements are included in this present invention to overcome the disadvantages of prior-art flyback power converters. Firstly, the flyback energy of the first primary winding is used as a DC power source for the PWM controller in order to reduce power consumption. A double sample amplifier samples the flyback voltage just before the transformer current drops to zero. Moreover, an offset current is pulled from a detection input of the double sample amplifier in order to generate a more accurate DC output voltage. The offset current is generated in response to the temperature in order to compensate for temperature-induced voltage fluctuations across the output rectifier. Ultimately, in order to maintain a constant output current, the PWM controller modulates the switching frequency in response to the output voltage.

Power converter system

Abstract: A power converter system advantageously employs a modular, bi-directionally symmetrical power converter assembly in a readily customizable configuration to interconnect a direct current power source to a three-phase alternating power grid. Connections external to the power converter assembly are selected to optimize the power converter system for a specific application, such as interconnecting a photovoltaic array to the three-phase electrical power grid. The electrical interconnections of various elements including isolation transformers, voltage sensors, and control switches are optimized to improve efficiency and reliability.

Monopolar DC to bipolar DC to AC converter

Abstract: This invention improves the performance and lowers the cost of DC to AC inverters and the systems where these inverters are used. The performance enhancements are most valuable in renewable and distributed energy applications where high power conversion efficiencies are critical. The invention allows a variety of DC sources to provide power thru the inverter to the utility grid without a transformer and at very high power conversion efficiencies. The enabling technology is a novel inverter circuit topology where the DC source is connected directly to the positive bus of the DC to AC converter and where a negative bus is generated from the positive bus with a flyback converter. The inverter power topology does include or require a transformer. The AC inverter output configuration can be either single-phase or three-phase. The AC inverter output can be either utility interactive or directly supply loads.

Common duty ratio control of input series connected modular DC-DC converters with active input voltage and load current sharing

Abstract: In this paper, active input voltage and load current sharing of DC-DC converter modules connected in series at the input and parallel at the output employing a novel common duty ratio control concept, is proposed. An appropriate analysis and experimental results are presented to verify the proposed concepts.

Dc to ac inverter with single-switch bipolar boost circuit

Abstract: This invention improves the performance and lowers the cost of DC to AC inverters and the systems where these inverters are used. The performance enhancements are most valuable in renewable and distributed energy applications where high power conversion efficiencies are critical. The invention allows a variety of DC sources to provide power thru the inverter to the utility grid or directly to loads without a transformer and at very high power conversion efficiencies. The enabling technology is a novel boost converter stage that regulates the voltage for a following DC to AC converter stage and uses a single semiconductor switching device. The AC inverter output configuration is either single-phase or three-phase.

Voltage converter control apparatus, and method

Abstract: By using a target voltage Vc* of a capacitor connected to the output side of a DC/DC converter and a voltage Vb of a battery connected to the input side of the DC/DC converter, a duty ratio D as a drive instruction of the DC/DC converter is calculated. By using the voltage Vb, the electromotive force Vbo of the battery, and the charge/discharge current Ib of the battery, an internal resistance Rb is calculated. According to the internal resistance Rb and the electromotive force Vbo, the current value when the battery output becomes maximum is set as the upper limit value of the optimal current range IR, the DC/DC converter is driven/controlled by limiting the duty ratio D so that the current Ib is within the range of the optimal current range IR. Thus, it is possible to appropriately convert the battery input voltage.

Optimal control of wide conversion ratio switching converters

Abstract: A switch state controller generating a pulse train is used in a power converter utilizing a plurality of converter stages all simultaneously controlled by a single switch controlled by said pulse train. On time of the pulse train is controlled according to an input or interim node characteristic of the supply and period is controlled by a characteristic of the output of the converter. This allows development of AC-to-DC converters, including power-factor-correction converters, and DC to DC converters with high conversion ratio with minimal parts count & high reliability.

Automotive application of multi-phase coupled-inductor DC-DC converter

Abstract: A set of four coupled inductors is applied to a four-phase interleaved 1 kW bi-directional 14 V to 42 V DC/DC converter for automotive applications. The coupled-inductor structure is optimized, and the performance is examined through simulations and experimental measurements. Although coupled inductors offer bigger advantages in applications that require fast transient response, they also have significant advantages in this type of application.

Methods and circuits for programmable automatic burst mode control using average output current

Abstract: The present invention comprises a user-programmable control circuit for use in a power converter to automatically transition the converter into BURST mode when load current demand is low. The control circuit senses load current demand by monitoring the output current of the converter, and generating a signal representative of the monitored output current. The control circuit may automatically transition the converter into BURST mode when the signal indicative of the average monitored output current decreases below a user-programmable threshold. BURST mode may increase overall converter efficiency by turning OFF a plurality of electronic components, and maintaining the converter's output voltage at a regulated level by energy stored in an output capacitor.

Double-input PWM DC/DC converter for high/low voltage sources

Abstract: A novel double-input PWM DC/DC converter for high/low voltage sources is proposed in this paper With PWM control, the proposed converter can draw power from two different voltage sources simultaneously or individually The operation modes and the steady-state analysis of the proposed double-input DC/DC converter are introduced in detail The control scheme for the power flow balancing is also presented By using a single passive lossless soft-switching cell, switching losses of all power switches can be reduced significantly Finally, experimental measurements are demonstrated to verify the feasibility of the proposed converter

Transformerless DC-DC converters with a very high DC line-to-load voltage ratio

Abstract: By splitting the output capacitor of a basic boost converter, and combining the resulting capacitors with the main switch in the form of a switched-capacitor circuit, a new step-up structure is realized. Without using a transformer, a high line-to-load DC voltage ratio is obtained. An output filter is added as usual in boost converters for getting a free-ripple output. The circuit compares favorably with a quadratic boost converter as regarding the count of devices and efficiency, even if it presents a lower DC gain. A DC analysis of the novel converter is presented. Experimental and simulation results confirm the theoretical expectations. By increasing the number of capacitors in the switched-capacitor circuit, higher gains are obtained. Versatility, high voltage gain and a good transient response are the features of the proposed converter.

DC overvoltage control during loss of converter in multiterminal voltage-source converter-based HVDC (M-VSC-HVDC)

Abstract: Security requires that a system continues to function even when any one subsystem fails. A multiterminal HVDC system consists of N voltage-source converters (VSCs) exchanging power through a DC network. When any one converter is lost, before the surviving (N-1) converters have time to re-establish a new power balance, the excess DC power can produce voltage spikes which are destructive to the power electronic switches. The paper shows that the advanced DC voltage controller (ADCVC), which is a higher hierarchical controller, can meet the targeted voltage margin.

A pwm plus phase-shift control bidirectional dc/dc converter

Abstract: A PWM plus phase-shift control bidirectional DC/DC converter is proposed. In this converter, PWM control and phase-shift control are combined to reduce current stress and both conducting and switching loss, to expand ZVS range. The operation principle and analysis of the converter are explained, and ZVS condition is derived. A prototype of PWM plus phase-shift bidirectional DC/DC converter is built to verify analysis.

Generalized structure of bi-directional switched-capacitor DC/DC converters

Abstract: This paper presents a generalized circuit structure of bi-directional switched-capacitor dc/dc converters that feature voltage step-down, voltage step-up, and bi-directional power flow. The starting point is the derivation of two structures of single-capacitor bi-directional converter cells. Current control scheme is applied in the capacitor-charging phase, resulting in a near-constant capacitor charging current and low electromagnetic interference. A converter string is then formulated by cascading a number of converter cells, in order to meet the input and output voltage requirements and conversion efficiency. By paralleling two similar strings and operating them in the anti phase, the overall converter input current becomes continuous. A reduced-order modeling and state-space averaging technique are used to study the static and dynamic behavior of the converter. The theoretical conversion efficiency in the step-down and step-up mode, respectively, is investigated for different voltage-conversion ratios and numbers of stages. The performance of the proposed structure is experimentally verified on a 5-V/12-V prototype.

Design consideration of the active-clamp forward converter with current mode control during large-signal transient

Abstract: The design issues of the active-clamp forward converter circuit with peak current mode control in small signal stability and large-signal transients are discussed. A design procedure is provided to solve circuit issues under these conditions. It is the first time that with the aid of simulation, we are able to optimize the circuit design of the active-clamp forward converter for large-signal transient behaviors.

Digital loop for regulating dc/dc converter with segmented switching

Abstract: A power control circuit is provided containing a switch array, which includes segmented switches, a flying capacitor, an output voltage terminal, a feedback loop, and a digital voltage regulator block. The digital voltage regulator block includes an A/D converter, an encoder, an add-subtractor, and a gate logic. These power control circuits do not include pass transistors. A method is also provided, where the charge pumps of the power control circuit are operated in two-phase cycles including a charging phase and a pumping phase. The power control circuit is controlled in both of these phases, thereby reducing the ripple of the output voltage.

Predictive DC voltage control of single-phase PV inverters with small DC link capacitance

Abstract: This paper proposes a novel control method for DC voltage in single-phase voltage-source inverters fed by constant-current or constant-power sources. The technique predicts the inverter power require to correct a DC voltage error within one fundamental AC cycle. This is based on the power balance between DC input and AC output, and the energy stored in the DC link capacitor. The fast response means a smaller capacitor can be used, and operation with a large double-line-frequency ripple on the DC bus is possible without causing distortion of the AC output current. This scheme is suitable for applications where substantial DC link buffer energy is unnecessary, e.g.: grid-connected photovoltaic generators. The reliability and lifetime of the inverter can be significantly improved if a non-electrolytic type capacitor is used. Experimental results are presented that verify the inverter operation.

Single inductor dual output buck converter with frequency and time varying offset control

Abstract: A single-inductor dual-output buck converter and control method that facilitates power conversion by converting a single DC power source/supply into two separate DC outputs, each of which can be configured to provide a selected/desired voltage by selection of respective duty cycles. The topology of the inverter includes a pair of diodes or switches that can selectively re-circulate inductor current. The converter is generally operated at a fixed frequency with four stages of operation. A first and third stage of operation provide power to a first and second output, respectively. A second and fourth stage of operation re-circulate inductor current and can partially recharge a battery type power source. The power output for each stage (voltage and current) can be selectively obtained by computing and employing appropriate time periods for the stages of operation that correspond to appropriate duty cycles.

Extended fundamental frequency analysis of the LCC resonant converter

Abstract: Fundamental frequency techniques are used to analyze the series-parallel resonant converter under heavy load conditions, both with a continuous, but distorted parallel capacitor voltage waveform, and with a discontinuous capacitor voltage waveform. The analysis is validated with results from an experimental prototype. The application of the technique to the parallel-loaded L-C resonant converter is also considered.

Power converter controller having event generator for detection of events and generation of digital error

Abstract: A power converter comprises an event detection module detecting various events of the power converter in real time at the switching frequency of a switch in the power converter according to predetermined criteria. A pulse generator generates control signals for controlling the on-times and off-times of the switch based on the various detected events. The events detected by the event detection module include a detection of a “knee” in the reflected secondary voltage on the auxiliary windings of the transformer in a primary side sensing flyback power converter, and detection of a digital error quantifying the difference between the reference voltage and the reflected secondary voltage on the auxiliary windings of the transformer in time domain.

Optimization arrangement for direct electrical energy converters

Abstract: An arrangement is provided for supplying electrical energy to a load from a direct electrical energy converter that optimizes converter power generation efficiency. The arrangement for optimizing converter power generation efficiency includes an impedance transformation circuit coupled between the energy converter and load for regulating current delivered by the energy converter so as to maximize power delivered to the load.