Showing papers on "Buck–boost converter published in 1994"

Zero-voltage and zero-current-switching full bridge PWM converter for high power applications

Abstract: A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge (FB) pulse-width modulated (PWM) converter is proposed. The new converter overcomes the limitations of the zero-voltage-switching (ZVS)-FB-PWM converter, such as high circulating energy, loss of duty cycle, and limited ZVS load range for the lagging-leg switches. By using the DC blocking capacitor and adding a saturable inductor, the primary current during the freewheeling period is reduced to zero, allowing the lagging-leg switches to be operated with zero-current-switching (ZCS). Meanwhile, the leading-leg switches are still operated with ZVS. The new converter is attractive for high-voltage (400-800 V), high-power (2-10 kW) applications where IGBTs are predominantly used as the power switches. The principle of operation, features, and design considerations of the new converter are described and verified on a 2-kW, 100-kHz, IGBT-based experimental circuit.

Inductorless DC-to-DC converter with high power density

Abstract: A new type of switching-mode power supply containing no inductors or transformers is proposed. The controlled transfer of energy from a unregulated DC source to a regulated output voltage is realized through a switched-capacitor (SC) circuit. A duty-cycle control is used; the driving signals of the transistors in the SC circuit are determined by the feedback circuit. The absence of magnetic devices makes possible the realization of power converters of small size, low weight and high power density, able to be manufactured in IC technology. High efficiency, small output voltage ripple and good regulation for large changes in the input voltage and/or load values are other positive features of the new type of DC-to-DC power converter. The input-to-output voltage conversion ratio is flexible; the same converter structure can provide a large range of constant desired values of the output voltage for a given input voltage, by predetermining the steady-state conversion ratio. The frequency response shows good stability of the designed converter. The experimental results obtained by using a prototype of a step-down SC-based DC-to-DC converter confirmed the theoretical expectations and the computer simulation results. >

Analysis and design of LCL-type series resonant converter

Abstract: A series resonant converter modified by adding an inductor in parallel with the transformer primary (or secondary) is presented. This configuration is referred to as an "LCL-type series resonant converter". A simplified steady-state analysis using complex AC circuit analysis is presented. Based on the analysis, a simple design procedure is given. Detailed experimental results obtained from a MOSFET-based 640 W converter are presented to verify the analysis. A narrow variation in switching frequency is required to regulate the output voltage for a very wide change in load, and the converter has load short-circuit capability. It is shown that by placing the parallel inductor on the secondary side, the parasitics of the high-frequency transformer can be used profitably. >

Synchronously rectified buck-flyback DC to DC power converter

Abstract: A synchronously rectified buck-flyback converter is described which provides multiple synchronous regulated outputs. A synchronous buck converter provides the main output and a synchronous flyback converter, utilizing the primary inductor of the buck converter, provides the secondary output. The converter utilizes a split-feedback signal, whereby each of the regulated outputs provides a component of the signal and a switch controller synchronously activates and deactivates rectification switches based on the feedback signal, required output levels and load. The switches are synchronously controlled such that a power input switch is operated in anti-phase to a control switch for each regulated output.

An optimized DC-to-DC converter topology for high-voltage pulse-load applications

Abstract: This paper presents the study of a high-voltage DC/DC resonant converter which has excellent behaviour to be used in applications with strong variations in output voltage and in output current, because it maintains high efficiency in these types of applications. To do so, the switching losses have been minimized by integrating all parasitic elements (leakage inductance, secondary side capacitance of the high-voltage transformer and parasitic capacitances of the power switches and diodes) into the power topology, and the conduction losses have been minimized by operating the converter in a special mode (optimum switching line) in which no reactive energy is returned from the resonant elements to the input voltage source. The type of control used (PWM phase-shifted) allows one to maintains these desirable characteristics even when the operating point suffers a very strong variation. The final power topology might be called a "full-bridge, clamped mode, LCC-type parallel resonant converter with capacitive output filter". >

Demodulation of an IF-signal by a sigma-delta converter

Abstract: A sigma-delta signal converter is implemented using switched capacitor switching elements in which a first switch (31) serves as a mixer (11). The output of the mixer is directed to the second input of an adder (16), and its second input is the feedback signal (f1) of the sigma-delta signal converter, which is also directed into a base-frequency output signal through a decimator (14) and low-pass filtering (15).

Clamped continuous flyback power converter

Abstract: Size reduction in a clamped power converter can be achieved, and stability of the converter under no-load and transient loads can be substantially improved, by operating the converter in a continuous flyback mode.

Output plane analysis of load-sharing in multiple-module converter systems

Abstract: This paper explores the origin of the DC current-sharing problem of parallel-converter systems and the dual problem of voltage sharing in series-converter systems. Both problems may be studied by examining the output plane (output current versus output voltage) of a particular converter. It is shown that strict current source behavior is unnecessary for good current sharing in parallel-converter systems. Furthermore, a broad class of converters whose output voltage is load-dependent, i.e., those that have a moderate value of output resistance, all exhibit good voltage- and current-sharing characteristics. Such converters are often suitable for a/spl times/b arrays of converters that can meet a large range of power-conversion requirements. The output planes of discontinuous mode PWM converters as well as conventional and clamped series resonant converters are examined in detail. A simple small-signal model of the modular converter system is developed. Experimental confirmation of load sharing and the small-signal model is given for the clamped series resonant converter and the series resonant converter for various configurations of four converters. >

A novel three-phase single-switch discontinuous-mode AC-DC buck-boost converter with high-quality input current waveforms and isolated output

Abstract: In this paper, a new three-phase single-switch AC-DC flyback converter system is presented. The system operates in the discontinuous mode. The simple structure of its power and control circuit, low mains current distortion, and resistive fundamental behavior, as well as the high-frequency isolation of the controlled output voltage, have to be pointed out. Besides the analysis of the stationary operating behavior, the dependencies of the peak values, average values, and rms values of the device currents, and of the maximum blocking voltages across the power electronic devices on the circuit parameters, are given as analytic approximations. The theoretical analysis is verified by digital simulation. >

Development of a DC distributed power system

Abstract: This paper presents design considerations for power converter modules used in a distributed power system, including front-end power converter modules and load power converter modules. The system is designed for a universal input voltage of 90-260 V AC, with a bus voltage of 48 V DC. Several versions of the 600 W power factor corrected front-end power converter modules have been evaluated. One configuration includes a zero-voltage-transition PWM boost PFC circuit followed by a zero-voltage-switched active-clamp forward power converter. The second configuration uses an interleaved active-clamp flyback power converter for both the power factor correction and bus voltage regulation. 150 W and 300 W load power converter modules with 5 V output have been developed using the active clamp forward power converter topology and low-profile magnetics. >

2 MHz Power Converter with Piezoelectric Ceramic Transformer

Abstract: A power converter with a new piezoelectric transformer is presented. The piezoelectric transformer, made of lead titanate solid solution ceramic, is operated with a thickness extensional vibration mode. This transformer can operate at high frequency, over several megahertz, with about 90% efficiency. The resonant frequency for the transformer is 2 MHz. The power converter with the transformer applies the theory for a class-E switching converter using an electromagnetic transformer. Maximum output power is obtained when the switching frequency is slightly higher than the resonant frequency. A 4.4 W output power is successfully obtained with 52% efficiency at 2.1 MHz switching frequency.<>

A new ZCS-ZVS-PWM boost converter with unity power factor operation

Abstract: This paper introduces the self-resonance concept as a new way to obtain power converters without switching losses. Using this new approach, a self-resonant ZCS-ZVS-PWM boost power converter is presented. It is suitable for high switching frequency, high power operation and wide range of power. The converter control is done by using PWM technique, with constant frequency operation. The complete theoretical analysis and simulation results for the self-resonant PWM boost power converter, operating without power factor correction, are presented. Moreover, experimental results for this new boost converter, operating with unity power factor, support the validity of this new approach. >

AC-DC converter having saw-tooth wave generating circuit in active filter

Abstract: This invention provides an AC-DC converter in which the shape and the cost do not increase by a measure for a harmonic distortion in the power factor improved AC-DC converter generating little harmonic distortion. In the AC-DC converter, a control input terminal of a switching transistor of an active filter is connected to an output terminal of a flip-flop, a set input terminal of which is connected to a DC-DC converter to receive a synchronizing pulse signal therefrom. A reset input terminal of the flip-flop is connected to an output terminal of a comparator to receive an OFF-timing signal from the comparator. The comparator determines OFF-timing of the switching transistor by comparing a level voltage with an outout voltage from a saw-tooth wave generating circuit. Thereby since it is not required that an active filter has a multiplier and an an oscillating circuit, its circuit construction is simple and the AC-DC converter in small size and at low cost is realized.

Symmetrical, phase-shifting, fork transformer

Abstract: In 12-pulse and 18-pulse AC/DC converter systems a single wye connected auto transformer using appropriate segments of voltage from each phase connected in fork fashion is used to develop 6-phase and 9-phase voltages in a symmetrical manner such that inherent compensation is made for the dc converter output voltage to be within 4.2% of that of a 6-pulse converter. Additional design adjustments for step-up or step-down of voltage can be made without compromising the transformer symmetry. An unconnected but closed delta winding provides a path in which third harmonic currents, and multiples thereof can flow.

A BIFRED converter with a wide load range

Abstract: In this paper, the boost integrated flyback rectifier energy DC-DC (BIFRED) power converter which incorporates power factor correction, output voltage hold-up and input-to-output isolation is examined The particular problem of high bulk capacitor voltage at light loads is addressed and it is shown how this may be resolved if the boost and flyback sections of the power converter are allowed to operate discontinuously The criteria for ensuring correct operation in the discontinuous mode are investigated It is shown that operating in this mode places no restrictions on the minimum load and simplifies the control loop design >

A novel high power converter for non-contact charging with magnetic coupling

Abstract: A novel non-contact battery charger of high power of high efficiency using a self-oscillated soft-switching converter and a high power detachable transformer is proposed. The starting of the oscillation, the stabilizing of the bias voltage and also the soft-switching are obtained by a simple driving circuit which is made of diodes and resistors. Using this converter, we have obtained a non-contact-type battery charger of 98% efficiency, under the condition of 1 kW output. >

A choppingless converter for switched reluctance motor with unity power factor and sinusoidal input current

Abstract: This paper describes a new converter topology for switched reluctance motor drives. The new topology consists of a pair of boost-buck power converters and a machine converter. The boost converter lets the system deliver sinusoidal input current and enhances the DC source voltage having the capability of fast current rise/decay of the stator windings. It also provides DC voltage regulation. The buck converter is used to regulate the DC source voltage responding to the motor speed variations. The wide pre-voltage regulation by the two power conversion stages eliminates the high voltage-choppings to control the stator winding currents. This enables the machine-drive converter to work in single pulse-current mode, hence, removing the switching losses. >

Method and apparatus for increasing switching regulator light load efficiency

Abstract: A method and apparatus for increasing the light load efficiency of a DC-DC converter by reducing the quiescent power of the control section. In accordance with the invention, the DC-DC conversion is first started using a first regulator circuit to power the converter controller. When the converter output reaches an adequate level, the converter controller power input is switched to the output of the converter. At the same time, the first regulator circuit is turned off, whereby the converter controller continues to operate from the converter output, which has a voltage substantially less than the power supply input voltage. Because controllers all draw about the same current, the lower input voltage to the controller lowers the power consumption thereof, improving the efficiency of the regulator, particularly when subjected to light loads. Various embodiments are disclosed.

Control conditions to improve conducted EMI by switching frequency modulation of basic discontinuous PWM preregulators

Abstract: In this paper the authors analyze the operation conditions to control basic discontinuous AC-DC preregulators with variable switching frequency. The correct use of variable switching frequency control can lead to a reduction of conducted EMI generated. The basic PWM converters (buck, boost, buck-boost, sepic, Cuk and zeta) are studied. The authors achieve results which allow them to operate the converters under the condition proposed maintaining a very small low-order harmonic-current content. Some simulation examples using a buck-boost as DCM-PFP show the amplitude reduction of the high order harmonic content. Experimental results using a sepic converter show the feasibility of the approach. >

Thin type DC/DC converter using a coreless wire transformer

Abstract: A 10 W class thin type DC/DC power converter is developed which uses a new type of coreless wire transformer. The power converter is intended for portable equipment use. The coupling factor of the wire transformer is more than 95% at frequencies higher than 100 kHz. When applied in a 3 output DC/DC power converter, the power converter is only 5.5 mm thick and has 70% efficiency. >

A family of single-switch ZVS-CV DC-to-DC converters

Abstract: A family of single-switch ZVS-CV (zero voltage switching and clamped voltage) DC/DC power converters, i.e., buck, boost, buck/boost, Cuk, Zeta, and Sepic, are presented. Each power converter is realized by employing a commutation inductor circuit which is connected in parallel with either a transistor or a freewheeling diode in a conventional PWM power converter. The steady-state characteristics of these converters are analyzed, including the voltage conversion ratio, the ZVS condition and the input and output current ripple characteristics. These analytical results are confirmed by experiments. The proposed technique is quite simple and output voltage control is easy. >

High precision DC-DC converter

Abstract: A high precision DC-DC converter circuit having improved efficiency is disclosed. The DC-DC converter circuit includes a low accuracy switching regulator circuit for driving a switching field effect transistor (FET) on and off. A high accuracy output voltage regulator circuit is inserted into the feedback loop between the output of the DC-DC converter circuit and the sensing input of the switching regulator circuit such that the accuracy of the output voltage regulator circuit primarily determines the precision of the DC-DC converter. The DC-DC converter also includes a quick shut-off circuit coupled to the gate and source of the FET for driving the gate of the FET negative when the FET is switched off such that switching losses are minimized. A second embodiment of the high precision DC-DC converter is used to convert from 5.0 to 3.3 volts. The second embodiment includes a transformer, one winding of which is used as an output inductor. The second winding is used as part of a multiplying bootstrap circuit that approximately triples the 5.0 volt input voltage to drive the gate of an n-channel switching FET. The second embodiment also includes a circuit for extending the duty cycle of the switching regulator in response to a load transient on the output.

Analysis and implementation of a full-bridge constant-frequency LCC-type parallel resonant converter

Abstract: A comprehensive analysis of the full-bridge constant-frequency LCC-type parallel resonant converter (LCC-PRC) is presented. Owing to operation under constant frequency, the filter designs are simplified and utilisation of magnetic components are improved. The LCC-PRC takes on the desirable characteristics of the pure series and the pure parallel converter, thus removing the main disadvantages. A useful analytic technique, based on classical AC complex analysis, is introduced for designing the LCC-PRC. By using a proper transformation on the state variable, the converter is analysed by means of a two-dimensional state-plane diagram, which shows that the converter possesses three operation modes (I, II, III). It is shown that operating the converter in mode II provides the desirable higher efficiency for a wide load range. A CPU (8031) is used to control the phase-shift time. Its control characteristic is very accurate and the cost is low. Finally, a constant-frequency controlled full-bridge LCC-type parallel resonant converter (LCC-PRC) using the CPU (8031) control is implemented.

DC/DC converter for a variable voltage load

Abstract: The invention relates to a circuit for converting input source energy into output load energy, for example a flyback converter for charging a storage capacitor for defibrilation from a low-voltage battery in an implantable defibrilator. The invention allows the input current to pass through the flyback inductor for a fixed duration and it allows the output current to pass for a duration which is directly proportional to the average voltage of the battery and inversely proportional to the voltage of the capacitor which is charged. When the invention is used in proximity to an electromagnetic communications system, a control circuit, in order to avoid interference, enables and inhibits the converter with a maximum frequency which is substantially below the operating frequency of the system. Moreover, the control circuit drives the converter in such a way that the cycles of energy transfer from the source to the storage capacitor take place at a minimum fundamental frequency which is substantially above the frequency of the system.

Closed-loop characteristics of voltage-mode-controlled pwm boost dc-dc converter with an integral-lead controller

Abstract: A complete analysis of a voltage-mode-controlled pulse-width-modulated (PWM) boost DC-DC power converter is presented using a previously derived small-signal model for continuous conduction mode (CCM). All parasitic components such as the equivalent series resistance (ESR) of the filter capacitor, the ESR of the inductor, the transistor on-resistance, and the diode forward resistance and offset voltage are included in the model. A design procedure for an integral-lead controller including the loading effect of the voltage divider in the feedback loop is given. The Bode plots of the closed-loop control-to-output transfer function, input-to-output transfer function, input impedance, and output impedance are determined and illustrated for three values of the duty cycle. Step response plots of the PWM boost converter in the open-loop and closed-loop cases are shown for changes in line voltage and duty cycle.

A unity power factor resonant AC/DC converter for high frequency space power distribution system

Abstract: This paper presents analysis and design of a resonant AC/DC converter topology, suitable for use in an advanced single-phase, sine-wave voltage, high-frequency power distribution system, of the type that was proposed for a 20 kHz Space Station Primary Electrical Power Distribution System. The converter comprises a transformer, a double tuned resonant network comprising of series tuned and parallel tuned branches, a controlled rectifier and an output filter. A symmetrical phase control technique which generates fundamental AC current in phase with the input voltage is employed. Steady-state analysis of the converter in continuous current mode of operation is provided and the performance characteristics presented. The proposed converter has close-to-unity rated power factor (greater than 0.98), a wide range of output voltage control (0 to 100%), low total harmonic distortion in input current (less than 8%), and high conversion efficiency (greater than 92%). Finally, selected experimental results of a bread-board converter are presented. >

Tolerant power converter

Abstract: A solid-state power converter using a transistor bridge structure and symmetry modulation to improve output stability when driving resonant loads. The power converter utilize a direct coupled driver for each upper switching transistor, permitting a wider control range than a transformer. In addition, various circuits to protect the load and the converter include: power limiting, surge reduction, thermal limiting, input over-voltage protection, output over-voltage shutdown, ground-fault shutdown, re-start delay, soft-start, and low-current off-on switch.

Power sequencing control

Abstract: An apparatus for sequencing turn-on and turn-off of power converters includes a first DC to DC converter responsive to a control signal for asserting a voltage supply signal and a sense circuit responsive to the output of said first converter to sense the level of voltage at the output of the first converter and to provide an enable signal in response to the output of said first converter when the first converter reaches a desired value. The apparatus further includes a second DC to DC converter responsive to said enable signal to provide a second supply voltage at a second different voltage level. The sequencing control has a circuit responsive to said second supply voltage and the first supply voltage, to short the second DC to DC converter to a reference potential.

Variable structure controller for AC/DC boost converter

Abstract: Control of AC/DC converter in presence of unknown time-varying load is a complex task due to the strong nonlinearity inherent in the converter structure and to the ones introduced by the load. When robust control techniques are used for stabilizing converter output voltage, particular care must be used to avoid degradation of the input power factor. A variable structure controller for AC/DC boost converter ensuring both robustness to load variations and near-unity power factor is considered. Owing to the separate dynamics of the input current and of the output voltage, a cascade control structure is used. The reference for the inner current loop is a sinusoidal waveform whose amplitude is modulated by the external voltage controller. The current regulator is a hysteresis-type, in which the zero-voltage control is purposely used within the hysteresis band in order to reduce high frequency chattering and hence harmonic distortion. In the external voltage loop a dynamical sliding-mode regulator is used to guarantee system robustness without introducing discontinuous control action. >

Single-phase composite PWM voltage source converter

Abstract: This paper proposes a novel circuit of a single-phase voltage source converter. A pulsewidth modulation (PWM) strategy is utilized to obtain a sinusoidal input current. The proposed circuit has an auxiliary arm for the bridge circuit and can be operated by a composite PWM strategy which contributes to reduce the ripple in the current. Moreover, the novel circuit has an LC series resonance circuit in the DC side. The DC capacitance necessarily installed in the converter can be greatly reduced by applying the resonance circuit and the constant DC voltage is achieved. The experimental and the theoretical results in the rectifier operation of the converter are shown. The steady state waveforms in the inverter operation with the photovoltaic in the DC side are given. The experiments show that the proposed converter can be used for a single-phase utility interactive photovoltaic system. >