Showing papers on "Boost converter published in 1991"

Switching converters with wide DC conversion range

Abstract: Compared to basic converter topologies (buck, boost, buck-boost, Cuk, etc.), pulse-width modulation (PWM) converters with quadratic DC conversion ratios, M(D)=D/sup 2/, M(D)=D/sup 2//(1-D) or M(D)=D/sup 2//(1-D)/sup 2/, offer a significantly wider conversion range. For a given minimum ON-time and, consequently, for a given minimum duty ratio D/sub min/, D/sup 2/ in the numerator of M(D) yields a much lower limit on the minimum attainable conversion ratio. By applying a systematic synthesis procedure, six novel single-transistor converter configurations with quadratic DC conversion ratios are found. The simpler, single-transistor realization is the most important advantage over the straightforward cascade of two basic converters. As far as conversion efficiency is concerned, it is clear that a single-stage converter is usually a better choice than a two-stage converter. The quadratic converters proposed are intended for applications where conventional single-stage converters are inadequate-for high-frequency applications where the specified range of input voltages and the specified range of output voltages call for an extremely large range of conversion ratios. >

Pseudo-resonant full bridge DC/DC converter

Abstract: A DC-DC power converter topology that combines the ease of control and wide range of conventional DC-DC converters, with low switching losses, low dv/dt and low electromagnetic interference that is typical of zero voltage switched resonant converters is proposed. Consequently, the ratings of these components are substantially lower than for similarly rated resonant topologies. While resonant elements are used to ensure zero voltage switching of all devices, they have little or no role in the actual power transfer and can thus be reasonably sized. As the resonant elements are not involved in the primary power transfer, the converter is referred to as a pseudo-resonant converter. It is shown that the converter offers significantly higher levels of performance than either the pulse width-modulated (PWM) or typical resonant converters. Operation at very high frequencies is possible and is shown with the fabrication of a 200 W 1 MHz DC-DC converter. >

High efficiency telecom rectifier using a novel soft-switched boost-based input current shaper

Abstract: A novel snubber circuit for the constant frequency pulsewidth-modulation (PWM) boost converter is presented to provide soft-switching transitions for the power switches and thus to reduce the power losses, component stresses, and noise generation. The proposed topology is very useful for the input current shapers in AC-AC applications. The operation of the circuit including its control block is explained and illustrated for a 1.5 kW, 100 kHz high-performance power-factor-corrected telecommunication rectifier. >

A fast-response high power factor converter with a single power stage

Abstract: An offline switching converter which operates with high input power factor while maintaining fast transient response at its output is described. A single power stage with dual output produces both the desired DC output and a boosting supply in series with the input. The resonant boosting supply at the input is controlled by frequency modulation of the power stage, while the desired DC output is PWM controlled. Since both the input boost supply and the output supply can be controlled independently, a fast transient response can be maintained at both the input (for active current wave-shaping), and at the output (for good output regulation). In addition, even without active control of the boost supply, a reasonably good input current waveshape results due to the natural gain characteristics of the boost resonant circuit. Zero voltage switching is maintained, allowing the circuit to be designed at high frequency to reduce size and cost, and increase performance. >

A high frequency AC/DC converter with unity power factor and minimum harmonic distortion

Abstract: A novel forced commutated AC/DC converter and control strategy is proposed that is able to draw nearly sinusoidal currents at unity power factor from three-phase power lines. The power factor is controlled by adjusting the relative position of the fundamental component of an optimized pulse-width-modulation (PWM) type voltage with respect to the supply voltage. Current harmonic distortion is minimized by the use of optimized firing angles for the converter at a frequency where gate turn-off thyristors (GTOs) can be used. This feature makes this approach attractive at power levels of 100 kW to 600 kW. An 8096 microcontroller is used to minimize the interface hardware requirements. The theoretical analysis of the converter, the control energy, and experimental results for a low-power prototype are presented. >

An improved zero-voltage-switched PWM converter using a saturable inductor

Abstract: The saturable inductor is employed in the full-bridge (FB) zero-voltage-switched (ZVS) pulsewidth-modulated (PWM) converter to improve its performance. The current and voltage stresses of the switches as well as parasitic oscillations are significantly reduced compared to those of the conventional FB-ZVS-PWM converter. The theoretical analysis is presented and is verified on a 500 kHz, 5 V/40 A converter. >

Characteristics of load resonant converters operated in a high power factor mode

Abstract: The performance of the parallel resonant converter and the combination series/parallel resonant converter (LCC converter) when operated above resonance in a high power factor mode are determined and compared for single-phase applications. When the DC voltage applied to the input of these converters is obtained from a single-phase rectifier with a small DC link capacitor, a relatively high power factor inherently results, even with no active control of the input line current. This behaviour is due to the pulsating nature of the DC link and the inherent capability of the converters to boost voltage during the valleys of the input AC wave. With no active control of the input line current, the power factor depends on the ratio of operating frequency to tank resonant frequency. With active control of the input line current, near unity power factor and low input harmonic currents can be obtained. >

Apparatus for controlling the input impedance of a power converter

Abstract: A DC-DC power converter, which can be adapted for use with a single- or multiple-phase AC input, uses energy control because it transcends the modulators and is linear. The use of feed back control is minimized by the use of feed forward control, and in particular the feed forward of the output power to control the input power. The dynamic resistance of the input is controlled, ensuring high power factor in the AC input embodiments of the converter. A multiple-input buck derived converter can have parallel or series inputs, and one or more of the inputs can be lower than the output, even zero or negative. A multiple output boost derived converter can have parallel or series outputs, and one or more of the outputs can be lower than the input, even zero.

Interleaved bridge converter

Abstract: A DC to DC power converter is implemented which includes an input switching circuit, an input capacitor, a transformer and an output rectifying switching circuit coupled to the transformer. The input switching circuit consists of a minimum of four transistors which are operated in a timed relationship such that bi-directional currents are developed in both primary windings. The output rectifying switching circuit is operated with switching transistors that provide zero-voltage resonant transition (ZVRT) switching. Timing relationships between the input signals control the ZVRT with switching of the transistors. Bidirectional currents in the primary windings of the single transformer element permit a reduction in volume of the magnetic element and the coils of the transformer for a given level of output power. Overall, converter volume for a given output power is thereby sufficiently reduced to allow a power converter to be mounted on a circuit board, which enables a practical embodiment of a distributed power processing system.

High power-factor converter for motor drives and power supplies

Abstract: A high power-factor converter (50) for use with motor drives and power supplies. A first and "buck"-type converter section (62) is connected to an a.c. voltage source. This section provides an output voltage having preselected voltage characteristics. This section is operational during that portion of an input voltage cycle in which the input voltage level exceeds that of the output voltage level. A second and "boost"-type converter section (70) is also connected to the voltage source. This second section also provides the output voltage, and is operational during that portion of the input voltage cycle in which the output voltage level exceeds that of the input voltage level. A control circuit (66) is responsive to the relative levels of the input and output voltages to operate the first and second converter sections on a time sharing basis in which converter operation is switched between the two converter sections as a function of the sensed actual output voltage characteristics compared to the preselected characteristics. This permits the converter to maintain a nearly full conduction angle, and therefore a high power factor, for any level of output voltage in a range from zero volts to voltage levels higher than the peak input voltage level.

A modified C-dump converter for variable-reluctance machines

Abstract: A new type of converter for variable-reluctance-machine (VRM) drives is described. In this converter topology, the energy extracted from an ongoing phase is stored in a dump capacitor. The energy stored is consequently used either to quickly turn on the next ongoing phase or to energize the conducting phase frequently during the conduction interval instead of being returned to the supply as for a conventional C-dump circuit. Since, the additional switch used to pass the energy to the C-dump capacitor is switched under a relatively-low-voltage condition and its switching frequency is relatively low, the rating of the additional switch is modest. The major advantage os this converter is that it uses a low-switching device/phase ratio while achieving better performance characteristics than the other topologies. >

Standby boost converter

Abstract: A boost voltage converter is combined with any DC-DC converter to provide a power system with significant overall power efficiency improvement in applications requiring continuous operation through low line transient levels. The boost converter is normally in a standby mode and only operates when the input DC voltage drops below a predetermined minimum steady state voltage. During steady state operation, a simple, efficient feedthrough of the DC current directly to the DC-DC converter is provided. Efficiency improvements in the combination of boost converter and DC-DC converter result from the reduction of the effective transient range seen by the DC-DC converter, allowing the DC-DC converter components to be designed and selected to significantly reduce their power dissipation during nontransient input steady-state operation.

High power factor, voltage-doubler rectifier

Abstract: A voltage-doubler rectifier includes an ac fullbridge diode rectifier and a dc-to-dc converter having two output boost circuits. One of the output boost circuits is coupled between the rectifier and a dc link, and the other output boost circuit is coupled, with opposite polarity, between the rectifier and the circuit common. Two series-connected filter capacitors are also coupled between the dc link and the circuit common. In a preferred embodiment, the two output boost circuits each comprise either a series, parallel, or combination series/parallel resonant circuit and a rectifier. A switch is coupled between the junction joining one pair of diodes of the rectifier and the junction joining the two filter capacitors. For a relatively high ac line voltage, the switch is open, and the circuit operates in a low boost mode. For a relatively low ac line voltage, the switch is closed, and the circuit operates in a high boost, or voltage-doubling, mode.

Efficient high-frequency soft-switched power converter with signal processor control

Abstract: DC/AC high-power, high-density converter structures and topologies are evaluated. The direct DC-low frequency-AC structure with the dual active bridge (DAB) topology is selected together with insulated gate bipolar transistor (IGBT) switches at 100 kHz, 20 kVA. A novel control strategy for the DAB and series-loaded resonant converters is introduced. It gives the possibility of fixed-frequency, zero voltage switching in the entire converter output V-I-plane. Design equations are presented. A method for comparing topologies by mapping stress levels in the output V-I plane is demonstrated. Experimental results from a small-scale model are shown, with good correspondence to simulation waveforms. The converter will be driven by an IBM PC/MS Windows based control system, of which the core is a 32-b digital signal processor connected to a programmable gate array holding all switch control circuitry. >

Method and apparatus for controlling the input impedance of a power converter

Abstract: A DC-DC power converter adaptable for use with an AC input, uses feed forward control of the output power to control the input power and the dynamic resistance of the input to ensure a high power factor in the AC input embodiments of the converter. The dynamic response of the power converter is controlled by feed forward, either through scheduling the energy content of a storage capacitor as an explicit function of the output power, the input voltage and the time constant, or through energy deficit feed forward in which the energy deficit caused by a transient is fed forward as an increment of power under feed forward control. Line frequency ripple feed forward compensates the feed forward in the embodiments having an AC input for any half frequency harmonics present in full wave rectified input due to a DC offset or asymmetry in the AC input. With load anticipation feed forward control, input power transitions smoothly without overshoot for a step change of output load from no load to full load and back.

Asymmetrical duty cycle power converter

Abstract: Operating a bridge type PWM switch mode power converter with asymmetrical duty ratios can eliminate switching losses with no increase in conduction loss. Included are three circuits, a full bridge buck converter, a half bridge buck converter, and a full bridge boost converter. These converters are an improvement over existing zero switching loss converter circuits in that they eliminate the large peak switch currents and voltages typical of existing circuits. The peak switch voltages found in these circuits are as low as those seen in standard PWM switch mode converters, and allow the use of efficient low voltage switches. The low peak and rms current delivered by the switches further improves efficiency, and the elimination of switching losses increases efficiency and allows operation at higher frequencies with the resultant benefit of smaller component size.

Control system for a current source converter supplying an ac bus

Abstract: An electrical power converter (10) includes both DC and AC power terminals (26,27; 19) which are respectively connected to a DC current source (42) and an AC voltage source (16), the latter comprising the grid of an AC power utility. A capacitor (24) is coupled to the AC terminals along with a load (22). A control and gating circuit (30) is coupled to the converter for supplying control signals for the thyristors (11) of a converter bridge included in the polyphase converter. When disconnected (at 20) from the utility grid, a relatively fast acting control loop (44) is coupled to the control and gating circuit and is responsive to the current flowing in the capacitor and an AC reference voltage (at 52) to accommodate the current source characteristics of the converter for maintaining an output voltage of substantially constant amplitude across the AC terminals. A second and relatively slower acting control loop (46) is also coupled to the control and gating circuit via the fast acting control loop and is responsible to the AC voltage across the capacitor and the load for providing regulation of the voltage across the AC terminals during steady state operation.

Analysis and design of a saturable reactor assisted soft-switching full-bridge DC-DC converter

Abstract: The analysis and design of a saturable reactor-assisted soft-switching full-bridge DC-DC converter are presented. The converter has advantages such as low switching losses (with no substantial increase in conduction losses), wide load range, and constant switching frequency. In order to show how to utilize the analysis results in designing, a 350 W 500 kHz converter is chosen as an example. The results are verified experimentally on a prototype converter. >

Zero-voltage-switched multiresonant DC to DC converter

Abstract: A multiresonant DC to DC converter which operates at a substantially fixed frequency yet maintains relatively constant efficiency levels despite wide variations in input voltage. The multiresonant converter includes a first transistor switch in series with the DC voltage supply source and the load and a second transistor switch in parallel with the DC voltage supply source and the load. The switching action of the first transistor switch is controlled as a function of the supply voltage input to the converter while the duty factor of the second transistor switch is controlled in accordance with the output voltage of the converter.

Inverse dual converter for high-power applications

Abstract: An inverse dual converter circuit (20) provides continuous voltage step-up or step-down control over a wide range and without the need of a transformer. The converter comprises an input DC voltage source (22) for generating an input DC voltage. An inverse dual converter bridge receives the input DC voltage and comprises a network of source voltage converters (26), an AC link circuit (28), and a network of load voltage converters (32). The source voltage converters (26) and load voltage converters (32) operate at the same frequency, but at a different phase. The AC link circuit (28) stores energy to be transferred from the source voltage converters (26) to the load voltage converters (32) and supplies reverse voltage bias for commutation. The inverse dual DC-DC (20) converter may include circuitry (180) for controlling the output DC voltage and for regulating output current continuity. Topological variations of the basic circuit include transformer coupled (140), multi-phase (80) and multi-pulse derivations. The single-phase inverse dual converter circuit (20) offers a buck-boost operation over a wide range without a transformer, bi-directional power flow, and complimentary commutation of converters. The commutation mechanism provided in the inverse dual converter circuit (20), when combined with gate turn-off switch thyristors provides zero current switching. This allows operation at high frequencies in high-power applications, with high efficiency.

Soft-switching power converter for operation in discrete pulse modulation and pulse width modulation modes

Abstract: A single-phase, soft-switching, ac-to-dc power converter comprises a rectifier for receiving and rectifying an ac voltage and providing the rectified ac voltage to a boost dc-to-dc converter, which in turn is coupled to an active clamped resonant dc link (ACRDCL). Resonant oscillations of the resonant dc link circuit comprising an inductor and a capacitor are maintained via control of an active clamp switching device. Soft-switching in a discrete pulse modulation scheme is achieved by controlling the switching instants of a boost switching device to occur at zero voltage instants of the resonant dc link. Alternatively, if a pair of snubber capacitors are added to the boost converter, soft-switching may be achieved in a pulse width modulation mode, resulting in reduced subharmonics even at higher frequencies and with smaller filter components.

UPS with input commutation between AC and DC sources of power

Abstract: An uninterruptible power supply is disclosed which is cheaper and more adaptable to various utility service inputs than presently available power supplies. A storage capacitor is placed between a boost AC/DC converter at the input and a DC/AC inverter at the output. A storage battery for maintaining constant voltage should the utility service power be interrupted is placed at the input, before the boost converter. Thus, a small battery is required because the boost converter is capable of boosting the battery's voltage to the voltage contained on the storage capacitor. A bidirectional semiconductor switch is provided in the boost converter to allow current to flow in both directions between its switch terminals when a AC input is applied. Appropriate control circuitry is provided which monitors the voltage at specific points throughout the circuit and controls operation of the bidirectional switch. Additionally, the control circuitry controls operation of a relay to switch power input between the utility service input and the storage battery depending in part upon the state of the utility service input voltage.

Power factor correction device provided with a frequency and amplitude modulated boost converter

Abstract: A power factor correction circuit used to improve the ratio of real power to apparent power in an electric power distribution line containing a source of AC sinusoidal voltage and a load. The circuit includes a frequency and amplitude modulated boost converter forcing the input current to have the same wave shape as that of the input voltage.

Regulated bi-directional DC-to-DC voltage converter which maintains a continuous input current during step-up conversion

Abstract: A pulse-width modulated, bi-directional DC-to-DC voltage converter having a regulated output, and capable of converting between a high-potential direct current voltage and a low-potential direct current voltage. The converter's magnetic components, as well as several of its semiconductor rectifiers, perform dual functions (one in the step-up mode, and another in the step-down mode), which serves to minimize the total component count, and allows the converter to be both compact and lightweight. Additionally, as the converter maintains a continuous input current during voltage step-up conversion, the generation of signals which might cause electromagnetic interference is reduced.

6 Switch-mode supply power factor improvement via harmonic elimination methods

Abstract: The authors present power factor improvement methods, for switched-mode power supplies, by using harmonics elimination. Three methods were valuated: a series connected resonant filter, a parallel connected resonant filter, and an active boost converter. The two passive filters are commercial products, and the boost converter is an in-house design using a power MOSFET as the switching device and a dedicated commercial IC for the control circuit. An off-the-shelf PC power supply along with the two passive filters and a boost converter were used as the test specimen. The experimental results show input power factor, distortion factor, crest factor, total harmonic distortion, and harmonic components. Also identified are the power system impacts of nonlinear current, the relative cost of harmonic elimination, and the motivation that may come from new power quality standards. >

Output voltage estimating circuit for a power converter having galvanic isolation between input and output circuits

Abstract: A method of and apparatus for monitoring the output signals of a power converter, having galvanic isolation between the input and output, observes the voltage and current on the primary side of the converter as reflected through a tertiary winding or influenced through the primary winding of the power transformer and applies error corrections thereto to replicate the output signal. These corrections are arrived at by compensating for operational differences between input and output circuitry and by emulating, on the primary side, the output side circuitry that causes the differences between the output signal and the reflected signal, and the conditions to which the output side circuitry is subjected. The resulting replicated signal is applied to feedback control circuitry, in lieu of the actual output signal, and used to regulate the output of the power converter.

Zero voltage, zero current, resonant converter

Abstract: The resonant tank transformer assy is placed in series with either the output or the input of any multi ended transformer used in DC to DC conversion. It has one winding used for the resonant tank which is connected to a resonant capacitor and at least two additional windings, one for each side of the transformers windings if on the primary and at least two windings for each output if placed in the secondary with each of the two windings being placed in series with each respective secondary windings ground. The additional output windings being correctly ratio to achieve balanced reflected voltages. In series with a primary winding is a control switch; in series with the other primary winding is a control switch. The switches are operated alternately, by the control circuit and with a predetermined delay or dead time between the opening of one switch and closing of the other.

Bootstrap modified topologies for wide-input range switchmode DC to DC converters

Abstract: A bootstrap circuit that operates in combination with switchmode DC to DC converter topologies that are based on forward (10), half-bridge/full-bridge (40) and flyback (60) configurations. Each configuration consists of an output circuit (18) and a bootstrap modified input circuit (12) that further consists of a bootstrap circuit (14) and a converter input circuit (16). The bootstrap function is achieved by charging a bootstrap inductor (L1) from current derived from the input voltage source and subsequently discharging the inductor through a bootstrap capacitor (C1) where an augmented voltage that is higher than the input voltage is developed. The converter then operates from the augmented voltage rather than from the input voltage. Thus, the invention is able to provide a constant output when operated over a wide-input voltage range while at the same time reducing the voltage stresses on the converter's primary switches and output rectifiers. Furthermore, reduction of input RF noise is accomplished by judicious choice of size and location of the bootstrap capacitor C1.

Power factor correction techniques used for fluorescent lamp ballasts

Abstract: Various power factor correction techniques used in fluorescent lamp ballast are described. The basic circuit used to control the lamp voltage and current is the current-fed sine wave inverter. Numerous different passive power factor correction circuits were designed, built, and tested. A continuous duty boost converter was designed, built, and tested to make the comparisons. In all cases the wattage line power draw was greater than 300 W. The analytical methodology used to define power factor corrections was reevaluated. A newer version was derived, and a more accurate form of power factor derivation is presented which takes into account distortions of the AC line voltage. An attempt is made to explain the need for low-source impedance to make the correct measurements. >

Enhanced synchronous rectifier

Abstract: A power converter is provided located in a remote terminal of a telephone system, the telephone system having a central office which powers a plurality of telephone loops with a DC voltage having at least two substantially different levels The remote terminal power converter derives remote terminal output load voltages including a low voltage regulated supply from the DC voltage provided to the loop from the central office The remote terminal power converter comprises a synchronous rectifier for providing a predetermined low voltage regulated supply The remote terminal power converter further comprises a receiving circuit connected to the loop for receiving DC voltage from the central office and supplying a low voltage output for producing the low voltage regulated supply A switch is associated with the receiving circuit for producing an output signal on the low voltage output, the output signal having sequential charging, flyback, and discontinuous intervals The discontinuous interval has a variable time duration dependent on at least the voltage level being coupled to the loop by the central office The synchronous rectifier is coupled between the low voltage output and the low voltage regulated supply and includes a power switching device, and a circuit responsive to the termination of the charging interval for driving the power switching device on The synchronous rectifier also includes a circuit for sensing a condition indicative of the onset of the discontinuous interval and turning off the power switching device for at least the duration of the discontinuous interval, independent of the time duration of the discontinuous interval