Showing papers on "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.

A comparison of high power DC-to-DC soft-switched converter topologies

Abstract: Many industrial and military applications are arising that require high power DC-DC conversion. These applications include shipboard, spaceborne, and transportation power systems. By employing new high voltage, high power IGBTs, along with modern soft-switching techniques, the switching frequency can be significantly higher than obtained using GTO devices, which in turn can lead to smaller, lighter weight, and potentially more cost effective equipment. The purpose of this paper is to compare the properties of several soft-switching converter topologies when used to achieve DC-DC conversion at high power and high voltage levels. As an example, a 100 kW transformer isolated converter with 700-1400 V DC input is designed with an estimated weight in the 200 pound range and an energy efficiency of 95%. >

A new maximum power point tracker of photovoltaic arrays using fuzzy controller

Abstract: Studies on photovoltaic systems are increasing because of a large, secure, essentially exhaustible and broadly available resource as a future energy supply. However, the output power induced in the photovoltaic modules is influenced by an intensity of solar cell radiation, temperature of the solar cells and so on. Therefore, to maximize the efficiency of the renewable energy system, it is necessary to track the maximum power point of the input source. In this paper, a new maximum power point tracker (MPPT) using fuzzy set theory is proposed to improve energy conversion efficiency. A fuzzy algorithm based on linguistic rules describing the operator's control strategy is applied to control the step-up converter for the MPPT. Fuzzy logic control based on coarse and fine mode has been incorporated in order to reduce not only the time required to track the maximum power point but also the fluctuation of power. The MPPT algorithm is implemented by a 16 bit single chip 80C196KB microcontroller. Simulation and experimental results show that performance of the fuzzy controller in a maximum power tracking of a photovoltaic array is better than that of controller based upon the hill climbing method. >

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. >

Reduction of voltage stress in integrated high-quality rectifier-regulators by variable-frequency control

Abstract: The Integrated High-Quality Rectifier-Regulators (IHQRRs) suffer from relatively high stress on the internal-energy storage capacitor and, consequently, on primary-side semiconductors. As a result, they are not practical in applications with the universal input-voltage range. In this paper, a variable-frequency control that reduces the voltage stress and makes the IHQRRs suitable for universal input-range applications is described. Evaluation results of a 90 W, experimental BIBRED power converter that uses the proposed variable-frequency control are presented. >

Synchronous switching cascade connected offline PFC-PWM combination power converter controller

Abstract: A synchronous switching cascade connected power converter includes a first power factor correction converter stage and a second DC to DC converter stage for generating an output voltage in response to an input voltage and current. The output voltage is controlled by a circuit which measures a level of current within the circuit, compares that level to a predetermined desired level, and develops a response elsewhere in the circuit. Leading edge modulation for the first stage and trailing edge modulation for the second stage is implemented to realize synchronous switching between the two power stages. A single reference clock signal is used to control both the power stages. The duty cycle of the first stage is varied according to the input voltage. The duty cycle of the second stage is ideally held constant at fifty percent but will vary as the input voltage to this stage varies. A dc ok comparator is coupled to the first stage for comparing an output voltage to a threshold value and preventing the second stage from turning on if the output voltage of the first stage is below the threshold value. A transconductance amplifier is used to control the input current and the output voltage of the power stages. A circuit for capturing a portion of the voltage lost due to the parasitic capacitances of the switches is also included. This capturing stage is coupled to the switch to capture voltage discharged by the parasitic capacitance and use it to then charge the output capacitor of the converter stage.

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. >

A new ZVS-PWM unity power factor rectifier with reduced conduction losses

Abstract: This paper introduces a new single-phase high power factor rectifier, which features regulation by conventional PWM, soft commutation and instantaneous average line current control. Furthermore, thanks to the use of a single converter, instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter, a significant reduction in the conduction losses is achieved. A prototype rated at 1.6 kW, operating at 70 kHz, with an input AC voltage of 220 Vrms and an output voltage of 400 V/sub DC/ has been implemented in the laboratory. An efficiency of 97.8 % at 1.6 kW has been measured. Analysis, design, and the control circuitry are also presented in the paper. >

Novel full bridge zero-voltage-transition PWM DC/DC converter for high power applications

Abstract: A novel full-bridge (FB) zero-voltage-transition (ZVT) PWM DC/DC converter for high power applications is proposed. An auxiliary network which consists of two small switches and one small inductor provides zero-voltage-switching (ZVS) for entire line and load ranges without increasing device voltage and current stresses. Since the ZVS range is independent of the switch capacitance, IGBTs can be used instead of MOSFETs by adding external capacitors to the switches without increasing switching losses, which allows the proposed converter to handle higher power. Operation, analysis, and features are described and verified experimentally. A 1.8 kW ZVT PWM converter prototype is compared with a ZVS PWM converter prototype of the same power rating. >

A novel three-phase utility interface minimizing line current harmonics of high-power telecommunications rectifier modules

Abstract: Based on the combination of a three-phase diode bridge and DC/DC boost converter a new three-phase three-switch three-level PWM rectifier system is developed. It can be characterized by sinusoidal mains current consumption, controlled output voltage and low blocking voltage stress on the power transistors. The application could be, e.g., for feeding the DC link of a telecommunications power supply module. The stationary operational behavior, the control of the mains currents and of the output voltage are analyzed. Finally, the stresses on the system components are determined by digital simulation and compared to the stresses in a conventional PWM rectifier system. >

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.

Experimental study of a bidirectional DC-DC converter for the DC link voltage control and the regenerative braking in PM motor drives devoted to electrical vehicles

Abstract: The use of a bidirectional DC-DC converter operating in the DC link of CRPWM-inverter-fed motor drives devoted to electric vehicles (EVs) application allows a suitable control of both motoring and regenerative braking operations, and it can contribute to a significant increase of the motor drive overall efficiency. This paper deals with the experimental study of a bidirectional DC-DC converter prototype which has been designed for application in small-size EVs propelled by axial-flux PM motor drives. The paper discusses the converter modes of operation and reports the experimental results taken from a converter prototype which has been constructed using an IGBTs power module rated 600 V, 50 A. >

Flash memory and a microcomputer

Abstract: A microcomputer mounted on a single semiconductor chip includes a central processing unit and a nonvolatile flash memory which allows the information to be processed by the central processing unit to be re-programmed by electrical erasing and programming operations. The microcomputer is provided with a normal power supply voltage terminal and a programming power supply voltage terminal and also incorporates a power supply voltage level detection device and an internal voltage boost circuit to decide the re-programming mode for the flash memory according to the level of the voltage supplied and to select between the boost voltage and the external high voltage in performing the erasing and programming of data.

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.

Fuel cell voltage generator

Abstract: The invention relates to a voltage generator including a fuel cell, a d.c. converter and a storage battery, the input terminals of the d.c. converter being connected to the fuel cell terminals and the output terminals of the d.c. converter being connected on the voltage generator terminals in parallel with those of the battery. A microprocessor regulates the maximum intensity value of the current going through the d.c. converter responsive to the voltage measured at the terminals of the fuel cell in order to maintain the voltage near a preset reference value.

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. >

Controller for a gas discharge lamp with variable inverter frequency and with lamp power and bus voltage control

Abstract: A high frequency HID ballast includes an inverter for operating the HID lamp at high frequency and an arc instability controller which detects and adjusts the operating frequency of the inverter to avoid acoustic resonance of the discharge arc The ballast ensures that the power delivered to the lamp remains substantially constant despite variations in the gain of the inverter which occur with changes in the operating frequency Power control is accomplished by sensing lamp power and controlling a boost converter to vary the bus voltage feeding the inverter The boost converter is also controlled during lamp ignition, when the load provided by the HID lamp is low, to clamp the bus voltage at a predetermined level The ballast employs universal techniques suitable for operating HID lamps of different types, wattages and manufacturers despite the occurrence of acoustic resonance/arc instabilities among these lamps over a fairly broad frequency range

Digitally controlled switchmode power supply

Abstract: A digitally controlled switchmode power supply by the use of a pulse width modulated (PWM) controlled field effect transistor, switches an inductor between input and output sides to provide a controllable DC output voltage. The digital processor receives and digitizes the input and output voltages and also the current through the associated inductor and derives a PWM control loop signal driving the associated field effect switching device to switch the inductor. The foregoing compensates for nonlinear changes in the value of the inductance due to changes in inductor currents and also avoids resonance at pole points of the LC circuit in the power supply. In addition a change in buck to boost modes may be accomplished automatically depending on input voltage operating conditions.

Zero-voltage-transition converters using an inductor feedback technique

Abstract: A technique using inductor feedback is presented for achieving zero-voltage switching (ZVS) in PWM controlled topologies. These converters exhibit low voltage and current stresses characteristic of hard-switched PWM converters, yet achieve ZVS with minimal current and voltage rating of the auxiliary soft-switching circuitry. Based on this technique, an experimental 730 W, 300 kHz boost converter is designed for universal off-line power factor correction. A complete analysis and a design procedure are also presented. >

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.<>

Bilateral power converter for a satellite power system

Abstract: A bilateral power converter (10) for a satellite power system comprises a battery (12), an inductor (14), a switching means (18, 20), and a controller (16). The battery (12) preferably has a first and second terminals. The inductor (14) is coupled to the first terminal of the battery (12) and the switching means (18, 20). The switching means (18, 20) selectively couples the second end of the inductor (14) to a bus (28) or to ground ill response to a control signal. The controller (16) monitors the bus (28) voltage, current flow to the battery (12) and the current flow through the switching means (18, 20). The controller (16) also receives control signals from the satellite's computer (13) and automatically regulates the voltage on the bus (28) by adjusting the duty cycle of the signal output by the controller (16) to the switching means (18, 20). Responsive to the duty cycle of the signal output by the controller (16), the bilateral converter (10) acts either as a buck converter or a boost converter to charge or discharge the battery according to the amount of power on the bus (28).

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. >

Efficient switched mode power converter circuit and method

Abstract: A method and apparatus are disclosed for sustaining efficiency of switched mode power converters over wide load ranges. The method and apparatus can be used with any switched mode power converter having at least one synchronous rectifier (Q2) capable of being enabled or disabled and coupled, either by direct connection or otherwise, to an inductor (L1) and a diode rectifier (D1), to provide a current path for the inductor current when the synchronous rectifier (Q2) is disabled. The power converter is initialized by enabling the synchronous rectifier (Q2). Occasionally, the synchronous rectifier (Q2) is disabled, and the energy stored in the inductor (L1) is detected by sensing a voltage representative of the energy stored in the inductor (L1). A power level signal is then generated indicating whether the power converter is operating above a selected threshold. The power converter is configured in response to the power level signal by enabling the synchronous rectifier (Q2) if the power level is above the threshold or by disabling the synchronous rectifier (Q2) otherwise. The steps of disabling, detecting, generating, and configuring are repeated.

Power converter possessing zero-voltage switching and output isolation

Abstract: A modified boost converter accomplishes power transfer to a load with an electrical isolation, a zero-voltage and a zero-current switching, a transformer core resetting mechanism, and component stresses identical to those in the conventional boost converters. The power converter contains two switching devices, a main one connected in parallel and a secondary one connected in series with a transformer primary winding. A secondary winding of the transformer is connected through an output rectifier to the load. Zero-voltage switching and proper transformer-core resetting are achieved from the resonance that exists between the parasitic capacitance of the secondary switching device and the magnetization inductance of the transformer. A transformer leakage inductance facilitates zero-current switching; thus, reducing the recovery time and current in the output rectifier, and the turn-on switching loss in the conventional main switching device. The switching converter contains a lossless clamping circuit, to limit the voltage stresses across both of the power switching devices to the reflected output voltage appearing across the primary.

Power supply unit for electric motor vehicle

Abstract: A main switch with a low withstand voltage usable to prevent a leak current from flowing from a floated running power supply by way of the main switch even when the insulation between the main switch and the body grounding is reduced. A running power supply for supplying power to a running motor, which includes a plurality of batteries connected in series to each other, is kept in the floating state with respect to the body grounding. Moreover, there is provided a step-down DC-DC converter of an input-output insulation type. A diode and a main switch are provided from a battery constituting part of the running power supply in this order to supply a starting power or starting signal to the DC-DC converter for starting the DC-DC converter. Thus, power is supplied to the input side of the DC-DC converter from the running power supply, to obtain a step-down accessary power supply VB.

Zero-voltage-transition converters using a simple magnetic feedback technique

Abstract: This paper presents a simple active energy recovery circuit which can be magnetically coupled to any isolated or nonisolated switching power converter to achieve zero-voltage switching (ZVS) of the power devices. Converters using this soft-switching technique exhibit low voltage and current stresses characteristic of hard-switched PWM converters, yet achieve ZVS thus enabling higher frequency operation. Based on this technique, an experimental 300 W, 250 kHz boost converter is designed for offline power factor correction. Steady-state analysis as well as simulations are also presented. >

Power factor correction circuitry

Abstract: A power factor correction circuit for use with a power supply. The power supply has an input for receiving an AC input signal, a rectifier for producing a rectified AC signal and an output stage for outputting a DC output signal for driving a load coupled to the output stage. The power factor correction circuit comprises an input port coupled to the rectifier for receiving the rectified AC signal; and an inductor coupled to the input port for storing energy in response to excitation by the rectified AC signal. The excitation of the inductor is controlled through the opening and closing of a switch by a controller. A capacitor is coupled to the inductor and charged by the energy stored in the inductor when the switch is opened to produce the DC output signal. The power factor correction circuit includes a diode for blocking the charge path between the input port and the capacitor and also allowing the controller to boost the charge level on the capacitor.