Showing papers on "Forward converter published in 2000"

A topology survey of single-stage power factor corrector with a boost type input-current-shaper

Abstract: A topological review of the single stage power factor corrected (PFC) rectifiers is presented in this paper. Most of reported single-stage PFC rectifiers cascade a boost type converter with a forward or a flyback DC-DC converter so that input current shaping, isolation, and fast output voltage regulation are performed in one single stage. The cost and performance of a single-stage PFC converters depend greatly on how its input current shaper (ICS) and the DC-DC converter are integrated together. For the cascade connected single-stage PFC rectifiers, the energy storage capacitor is found in either series or parallel path of energy flow. The second group appears to represent the main stream. Therefore, the focus of this paper is on this group. It is found that many of these topologies can be implemented by combining a 2-terminal or 3-terminal boost ICS cell with DC-DC converter along with an energy storage capacitor in between. A general rule is observed that translates a 3-terminal ICS cell to a 2-terminal ICS cell using an additional winding from the transformer and vice versa. According to the translation rule, many of reported single-stage PFC topologies can be viewed as electrically equivalent to one another. Several new PFC converters were derived from some existing topologies using the translation rule.

Investigating coupling inductors in the interleaving QSW VRM

Abstract: The multi-channel interleaving quasi-square-wave (QSW) buck converter has been proved to be suitable for the voltage regulator module (VRM) with low voltage, high current and fast transient response. Integrated magnetic is used to reduce the size of the converter and improve efficiency. However, the structure of the integrated magnetic requires precise adjustment. In this paper, analysis shows that a properly designed integrated magnetic can improve the steady-state and dynamic performance without requiring precise adjustment.

Actively clamped bidirectional flyback converter

Abstract: An actively clamped bidirectional flyback converter is proposed. The converter's operation is examined in detail. All switches in the converter have zero-voltage-switching characteristics. A low-frequency behavior model and small-signal transfer functions are derived. It is found that the flow of current is directly under the control of the duty cycle, and that the transformer's leakage inductance has a significant effect on the control characteristic of the converter. It is expected that such bidirectional converters will find wide applications in the interconnection of multiple sources of DC power to a common bus (e.g., in a DC uninterruptible power supply). Simulation and experiment results are also presented.

White light-emitting-diode lamp driver based on multiple output converter with output current mode control

Abstract: A white light-emitting-diode array driver circuit with a multiple output flyback (or forward) converter with output current mode control. The circuit comprises a power supply source and a transformer. The transformer has a primary winding coupled to, and configured to receive current from, the power supply, and a plurality of secondary windings coupled to the primary winding. The circuit also comprises a plurality of light-emitting-diode arrays, wherein each light-emitting-diode array is coupled to one of the secondary windings. A main controller is coupled to a first of the light-emitting-diode arrays and is configured to control a flow of current to the primary transformer winding. The circuit also comprises a plurality of secondary controllers, each of which are coupled to another of the light-emitting-diode arrays. In addition, each of the secondary controllers are configured to control a flow of current to its corresponding light-emitting-diode array. According to one embodiment of the invention, each of the light-emitting diodes has a resistor coupled to its cathode terminal. An output signal of each resistor is transmitted to the respective controller and is employed to determine the appropriate current flow to the light-emitting-diode array. The circuit may be configured as either a flyback converter, wherein the primary transformer winding is wound in the opposite direction of the secondary transformer windings, or as a forward converter, wherein the primary transformer winding is wound in the same direction as secondary transformer windings.

Operation principles of bi-directional full-bridge DC/DC converter with unified soft-switching scheme and soft-starting capability

Abstract: A new bi-directional dual full-bridge DC/DC converter with a unified soft-switching scheme and soft-start capability is proposed in this paper. A simple voltage clamp branch is used to limit transient voltage across the current-fed bridge and realize zero-voltage-switching (ZVS) in boost mode operation, while achieving hybrid zero-voltage/zero-current switching (ZVZCS) for the voltage-fed bridge in buck mode operation. The theory of operations including soft-start-up process is discussed in this paper.

High efficiency power conditioner employing low voltage DC bus and buck and boost converters

Abstract: A power conditioner interfaces a load to a fuel cell 10 that produces a low voltage that varies with the load. A dc-to-ac inverter 16 operates with a low voltage input provided by a dc bus 14 . When a positive step load change occurs, a low voltage battery 22 provides power equal to the step change until the fuel cell 10 is able to provide enough power to support the entire load. The power from the battery 22 is supplied to the varying dc bus 14 through a boost converter 12 . When very large positive load step changes occur, the battery can feed power to the dc bus through diode D 1 , rather than through the boost converter. Diode D 1 does not need to be used, but its use allows the boost converter to be sized for common load changes rather than for the maximum possible load change (such as might be seen during a faulted output). A buck converter converts the variable voltage on the dc bus 14 to the appropriate float charging voltage of the battery. The buck converter also supplies power for auxiliary equipment when available from the fuel cell. If the fuel cell is unable to provide the auxiliary power (such as during startup or load transients), then the auxiliary power can come directly from the battery.

Power electronic transformers for utility applications

Abstract: The concept of realizing a small size "solid-state" transformer has been discussed for some time. A fairly straightforward approach to accomplish size reduction in a transformer feeding a conventional rectifier-inverter system is to introduce an isolated DC-DC converter in the DC link, isolation being provided by a high frequency transformer. So also, several topologies that employ AC-AC converters connected on primary and secondary sides of a high frequency transformer to reduce the size and weight of the magnetic core have been reported in literature. Such AC-AC converters need switches with bi-directional voltage blocking and current carrying capability, which are commonly realized with pairs of gate turn-off devices such as insulated gate bipolar transistors (IGBT). This paper explores the possibilities of employing AC-AC switched mode power converters in combination with reactive elements to realize a chopped AC link, thereby decreasing the required magnetic core size for voltage transformation and isolation. A primary advantage of this approach is that, the static power converter needs only six devices to implement a three-phase electronic transformer, which makes it an economical solution. Operating principles, magnetic design and other practical issues are discussed. Detailed computer simulations accompanied with experimental verification are presented in the paper.

Symmetrical multilevel converters with two quadrant DC-DC feeding

Abstract: In the technology sector of power electronics and control, the multilevel converter technology is still a rather new research area, but the application possibilities in the field of power drives and energy will demand more solutions with this promising technology. In the future, more converter systems will be realized with the multilevel topology. Up to now, multilevel converters have only been used in very particular applications, mainly due to the high costs and complexity of the multilevel converter system. The high costs are due to the fact that the latest technology on semiconductors, magnetic material for inductor and transformer cores and control system technology had to be used. But nowadays new developments in the fields of power semiconductors such as the IGBT, IGCT and perhaps in the future SiC switches as well as improvements of the performance of magnetic cores used in medium frequency transformers will favor the multilevel converters for many other application fields. It can be noted that the industrial trend is moving away from heavy and bulky passive components towards power converter systems using more and more semiconductor elements controlled by powerful processor systems integrating intelligent multi-task control algorithms. The presented work is a contribution to the large field of multilevel converters. It shows a certain kind of multilevel converter in a single phase and a three-phase configuration, called the series-connected four-quadrant converters (SCFQ). The two specialties of the presented converter type are a) that all the multilevel converter steps are fed by an identical DC voltage and b) that every multilevel converter step is realized with an individual AC-DC converter or four-quadrant converter. This type of multilevel converter is called multilevel converter with symmetrical feeding. In this work, a general theoretical development has been done for the use of this multilevel converter type. A special type of DC-DC converter is presented, in order to feed the individual four-quadrant converters of the multilevel converter with a constant DC voltage. All the developments and methods used are based on mathematical expressions. Various simulations using the latest software simulation tools are accomplished and are used to study different cases. The feasibility of the developments is underlined with a series of experimental results with all types of the used converters, which have been realized in the framework of this thesis. The main application for the multilevel converter presented in this work is the frontend power converter in locomotives. Instead of using a heavy low-frequency transformer to reduce the high-voltage from the catenary to a supportable voltage for the semiconductors, a multilevel converter concept is used. The multilevel converter is directly coupled to the catenary. There are many advantages compared to the existing solutions. In the same context, a novel solution of a multilevel converter has been developed for a locomotive usable on different power lines. The converter allows not only the operation on the high AC voltage power line (15kV), but also can be coupled to a medium-voltage DC power line (3kV). Three different configuration types of the locomotive converter have been developed and tested in a complex simulation environment. Besides the locomotive application, there are many more interesting applications for the symmetrical multilevel converter, e.g. in the fields of energy transmission (FACTS, static VAR compensators, electronic high-voltage transformers, etc.) and industrial drives. But certainly in the future with the availability of cheap semiconductors adapted to the needs of the multilevel converter, even more applications in lower power fields will be realized.

Buck or boost power converter

Abstract: A buck or boost (BOB) power converter circuit. A buck converter is cascaded with a boost converter to form a buck or boost circuit ( 20 ). The BOB converter is controlled by a controller ( 26 ) such that only the buck or boost converter is operating at any given time. A reference signal V ref can be applied to the controller ( 26 ) such that the output voltage from the converter closely tracks the reference signal. Positive and negative ramp signals are generated and an error feedback signal is compared with the ramp signals to control the output in accord with V ref . This is useful in application of the output voltage as the power supply to an RF Power Amplifier ( 16 ) so that the reference signal can represent the envelope of a signal to be transmitted and the RF PA ( 16 ) can operate at high efficiency.

AC power supply apparatus with economy mode and methods of operation thereof

Abstract: A power supply apparatus includes an AC input port, an output port, and a bypass circuit that couples the AC input port to the output port. An AC/DC converter circuit, e.g., a rectifier circuit, produces a DC voltage from an AC input voltage at the AC input port. A DC/AC converter circuit, e.g., a current mode controlled inverter, controls current transfer between the output port and the AC/DC converter circuit responsive to a control input such that respective first and second component currents of a current delivered to a load coupled to the output port pass via respective ones of the bypass circuit and the DC/AC converter circuit. The DC/AC converter circuit may be operated such that current passing through the bypass circuit is constrained to be substantially in phase with the AC input voltage. The power supply apparatus may have another mode of operation in which the DC/AC converter circuit exclusively provides power to the output port, and may include an auxiliary DC power supply circuit that provides a DC voltage to the DC/AC converter circuit. Related power supply methods are also discussed.

Charge pump DC/DC converters with reduced input noise

Abstract: A charge pump DC/DC converter with reduced noise at the input voltage source is provided. The present invention includes buck and boost DC/DC converters with added circuitry coupled between the input voltage and the switches which maintains a substantially constant input current on both phases of the charge pump clock. The added circuitry reduces input current variations to provide reduced noise at the input voltage source. Feedback loop circuitry coupled between the output node and the added circuitry varies the current through the switches to control the output current of the DC/DC converter in order to maintain the output voltage at the regulated value. The added circuitry may comprise a variable resistor, current mirror, or current mirrors.

Power converter mode transistioning method and apparatus

Abstract: A method and apparatus are provided for transitioning a power converter between a switched mode of operation and a linear regulator mode of operation. The power converter operates according to one or more intermediate modes of operation in which the switched mode and linear regulator modes cooperate to produce a shared power converter output. The power converter transitions between the various modes of operation in response to changes in circuit parametric conditions as defined by a series of state transition diagrams. Power converter output voltage is maintained in regulation during all modes of operation and transitions therebetween. The method and apparatus includes an integrated device that may be operated as a switch or a variable resistance device.

Lossless switching DC to DC converter with DC transformer

Abstract: Soft switching DC-to-DC converter operates at record high efficiency despite its small size and weight and ultra high overload current capability of several times the nominal load current. Such performance is made possible by use of unique magnetic and switching circuits with special properties. Other desirable performance features are provided concurrently such as: zero ripple current on input and output, low conducted and radiated Electromagnetic interference (EMI) noise, as well as low component stresses for increased converter reliability.

Operating a power converter at optimal efficiency

Abstract: A power converter control system is provided which combines a pulse train regulation control technique with a pulse train optimization technique, to control the output level of the power converter, while maintaining optimal performance for other power converter parameters. The power converter control system describe herein provides versatility not previously available in power converter control systems by providing features such as quasi-resonant mode control, discontinuous mode control, and/or power factor correction. A pulse optimizer adjusts or customizes, for example, the ON time, duty cycle or frequency of pulse train pulses output by a pulse generator. The adjusted pulses are gated by a pulse rate controller to selectively actuate a power switch, thereby regulating the output power level and optimize the overall performance of the power converter.

Power-factor-corrected single-stage inductive charger for electric-vehicle batteries

Abstract: A novel power-factor-corrected single-stage AC-DC converter for inductive charging of electric vehicle batteries is introduced. The resonant converter uses the current-source characteristic of the series-parallel topology to provide power factor correction over a wide output power range from zero to full load. Some design guidelines for this converter are outlined. An approximate small-signal model of the converter is also presented Experimental results verify the operation of the new converter.

A zero voltage switching three-level DC/DC converter

Abstract: A novel zero voltage switching (ZVS) three-level (TL) DC/DC power converter is presented in this paper. The converter uses a flying capacitor in the primary side to allow operation with phase-shift control and in this way achieves ZVS for all the switches. The principle of operation of the converter is analyzed and verified on a 6 kW, 100 kHz experimental prototype. Additionally, this paper presents improvement of the proposed converter by using different ZVS techniques.

Step wave power converter

Abstract: A single- or multi-phase step wave power converter includes multiple transformers configured to receive DC voltage from one or more power sources. Each of the transformers includes a primary winding and a secondary winding. The transformers are each configured to supply a step for a step wave AC output. Bridge circuits are supplied for controlling input of DC voltage into the primary windings of the transformers. Steps for the step wave AC output are output from the secondary windings based upon the input provided to the primary windings. DC source management circuitry manages which DC power source(s) supplies DC voltage input to each of the bridge circuits. The management circuitry provides seamless power switching between the plurality of DC power sources based on each power source's performance characteristics. A pulse-width modulator can also be provided to the step wave power converter to modulate the input into a selected primary winding. In this way, the step wave AC output can be fine-tuned in substantial conformance with an ideal AC waveform.

Series resonant ZCS-PFM DC-DC converter with multistage rectified voltage multiplier and dual-mode PFM control scheme for medical-use high-voltage X-ray power generator

Abstract: In general, high-voltage DC power supplies employing a variety of high-frequency inverters are implemented for constant value control schemes. In particular, their good transient and steady state performances cannot be achieved under wide load variations for a medical-use high-voltage X-ray generator, ranging from 20 kV to 150 kV in the output voltage and from 0.5 mA to 1250 mA, respectively. A high-voltage DC power supply designed for X-ray power generator applications is considered, which uses a series resonant inverter-linked multistage DC voltage multiplier instead of a conventional high-voltage diode module rectifier connected to the secondary side of a high-voltage transformer. A constant on-time/variable frequency control scheme of this converter operating at zero-current soft switching mode is described. Introducing the capacitor-diode cascaded multistage voltage multiplier, the secondary turn numbers and secondary-side stray capacitance of the high-voltage, high-frequency transformer, as well as the rectifier diode voltage ratings, can be greatly reduced. It is shown that the proposed converter control scheme of the two-step selective changed frequency selection switching is more effective for improving the output voltage responses. The series resonant high frequency transformer-linked voltage-multiplying rectifier is evaluated for an X-ray high-voltage generator on the basis of simulation analysis and observed data in experiment.

High-power-density MHz-switching monolithic DC-DC converter with thin-film inductor

Abstract: In this paper, we report the newly developed DC-DC converter IC termed monolithic DC-DC converter, in which a thin-film inductor and power IC are integrated, and describe the micro DC-DC converter module utilizing this IC. The thin-film inductor used in the monolithic DC-DC converter was fabricated by RF sputtering, photosensitive polyimide lithography and electro-plating onto the power IC. The micro DC-DC converter module using the monolithic DC-DC converter achieved power density of 5.6 W/cm/sup 3/ at output power of 1 W and maximum efficiency of 83.3% at switching frequency of 3 MHz.

Topology and control method for power factor correction

Abstract: In a power factor corrected AC-to-DC power supply system, a DC-to-DC power converter is coupled to the output of an AC-to-DC power converter in order to produce a regulated DC output signal from a rectified AC input signal. The AC-to-DC power converter and the DC-to-DC power converter each includes a switch for controlling the operation of their respective power converter. The AC-to-DC converter includes an inductor. The system provides power factor correction for minimizing harmonic distortion by including a controller that receives the regulated DC output voltage as a feedback signal, and in response, produces a series of drive pulses having predetermined constant duty cycle. These pulses are simultaneously fed to each switch, to operate the respective converters alternately between ON and OFF states. When the AC-to-DC converter is driven by a fixed duty cycle of the series of pulses, power factor correction is improved since the current flowing through the inductor is substantially proportional to the waveform of the rectified AC input signal. By preselecting the value of the inductor, the AC-to-DC converter is operable in a discontinuous mode when the instantaneous rectified AC input signal is low and in a continuous mode when the instantaneous rectified AC input signal is high.

Periodic errors elimination in CVCF PWM DC/AC converter systems: repetitive control approach

Abstract: A plug-in digital repetitive learning (RC) controller is proposed to eliminate periodic tracking errors in constant-voltage constant-frequency (CVCF) pulse-width modulated (PWM) DC/AC converter systems. The design of the RC controller is systematically developed and the stability analysis of the overall system is discussed. The periodic errors are forced toward zero asymptotically and the total harmonics distortion (THD) of the output voltage is substantially reduced under parameter uncertainties and load disturbances. Simulation and experimental results are provided to illustrate the validity of the proposed scheme.

Design, implementation, and experimental results of bi-directional full-bridge DC/DC converter with unified soft-switching scheme and soft-starting capability

Abstract: The PWM control, design and implementation issues of the bi-directional dual full-bridge DC/DC converter with a unified soft-switching scheme and soft-start capability, which was proposed in a companion paper, are presented in this part of the two-paper sequel. Test results on a 5 kW prototype converter, which is connected between a 12 V battery and a high voltage bus, and targeted for alternative energy applications, validate the secure operation, high reliability and superior efficiency of the proposed converter topology.

Multiple voltage output buck converter with a single inductor

Abstract: A low cost, multiple output buck converter is provided using a single inductor, a single pulse width modulator integrated circuit, and two MOSFETs plus one additional MOSFET and capacitor for each voltage output.

Isolated interleaved-phase-shift-PWM DC-DC ZVS converters

Abstract: This paper presents a new isolated DC-DC zero-voltage-switching (ZVS) converter, which is composed of two half-bridge converters associated in series operating at constant frequency. The converter can be seen as an alternative to the ZVS-phase-shift full-bridge DC-DC converter for high-voltage applications. The paper proposes a new command strategy, named interleaved phase shift, which allows equalization of the input capacitor voltage, where each capacitor shares one-quarter of the total input voltage. Due to phase-shift modulation, the current is equally shared among main switches, reducing the converter conduction losses, when compared with conventional pulsewidth modulation. Furthermore, the input capacitors voltage oscillations are reduced due to load variations, as well as due to input DC-bus 120 Hz ripple. Just as with a ZVS-phase-shift full-bridge converter, the proposed converter achieves ZVS in a wide load range, as a function of the transformer leakage inductance. The paper describes the analysis, operating principles, and design procedure for the proposed converter. Experimental results from a 1.5 kW prototype converter operating at 100 kHz with isolated 60 V/25 A output are presented to validate the theoretical analysis and to demonstrate the performance of the proposed converter.

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.

Direct current motor safety circuits for fluid delivery systems

Abstract: A safety circuit system for a DC driven device for use with a fluid delivery system includes a first voltage potential DC power line, a second voltage potential DC power line, a controller and a safety circuit. The first voltage potential DC power line is coupled to provide a first voltage potential to the DC driven device, and the second voltage potential DC power line is coupled to provide a second voltage potential to the DC driven device such that the second voltage potential is different relative to the first potential. The controller controls at least the first voltage potential on the first voltage potential DC power line. The safety circuit has an enable state and a disable state, in which the default state is the disable state. The safety circuit is coupled to the controller, and the controller controls the safety circuit to place the safety circuit in the enable state independently of controlling the first voltage potential on the first voltage potential DC power line. The safety circuit is operatively coupled to at least one of the first and second voltage potential DC power lines to inhibit DC flow and operation of the DC driven device when the safety circuit is in the disable state and to permit DC flow and operation of the DC driven device when the safety circuit is in the enable state such that the operation of the DC driven device will occur when the safety circuit is in the enable state. In one version the DC driven device is a DC motor in an infusion pump, while in other versions the DC driven device is a gas generator in an infusion pump. Preferably, the safety circuit is controlled by an AC signal from the controller such that the safety circuit is enabled by the AC signal to permit DC flow and enable the forward motion of the DC motor while the AC signal is provided by the controller.

A zero voltage and zero current switching three level DC/DC converter

Abstract: This paper presents a novel zero voltage and zero current switching (ZVZCS) three-Level (TL) DC/DC power converter. This converter overcomes the drawbacks presented by the conventional zero voltage switching (ZVS) three-level converter, such as high circulating energy, severe parasitic ringing on the rectifier diodes, and limited ZVS load range for the inner switches. The converter presented in this paper uses a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switches. Additionally, the converter uses an auxiliary circuit to reset the primary current during the freewheeling stage to achieve ZCS for the inner switches. The principle of operation and the DC characteristics of the new converter are analyzed and verified on a 6kW, 100 kHz experimental prototype.

Control of DC/DC converters having synchronous rectifiers

Abstract: A DC to DC power converter includes synchronous rectifiers which respond to a control waveform. Negative current from a load into the power converter is prevented by increasing the converter output voltage at a minimum current limit. The synchronous rectifiers may be held off in response to decision logic by activation of a hold-off circuit connected to a control terminal of a synchronous rectifier or of an ORing transistor at the converter output. When the synchronous rectifier is subsequently enabled, its control waveform may be increased slowly relative to the switching cycle.

Controlling a DC-DC converter by using the power MOSFET as a voltage controlled resistor

Abstract: Most converter designs assume that a closed power switch has zero volts across it. In general, this is a valid assumption that reduces the design complexity. However the fact that a power switch does have a finite resistance means that there will be a nonzero voltage across it during its on time. This voltage can be taken advantage of. This paper proposes a simple control technique that utilizes the variable resistance of the power MOSFET in a dc-dc converter. This is the first switched mode power supply that uses the power switch in more than two states or operating points. It is also the first switched mode power supply that uses the power switch as a variable control device as well as a power device. A 48-5-V 20-W forward converter is implemented to confirm the theory and demonstrate its practicality. The proposed technique provides self oscillation, self overload protection, zero voltage switching (ZVS), input voltage feedforward, and a reduced component count and cost.

Resonant switching power supply circuit with voltage doubler output

Abstract: A switching power supply circuit includes an insulating converter transformer where the insulating converter transformer has a gap formed therein so that a coupling which is efficient for a loose coupling is obtained; switching circuit, a primary side parallel resonance circuit formed from a leakage inductance component from the primary winding of the insulating converter transformer and a capacitance of a parallel resonance capacitor and a secondary side series resonance circuit including a secondary side series resonance capacitor and a secondary winding of the insulating converter transformer; a dc output voltage production means for performing a voltage multiplying full-wave rectification operation to produce a secondary side dc output voltage substantially equal to twice the input voltage level; and a constant voltage control means for varying a switching frequency of the switching element in order to perform constant voltage control of the secondary side output voltage.