Showing papers on "Buck converter published in 1995"

Single-phase three-level boost power factor correction converter

Abstract: In many single-phase power factor correction (PFC) applications, the power level can reach several kilowatts; and in some situations, the input voltage can be quite high too. For high power and/or high voltage applications, the major concerns of the conventional boost PFC converter are the inductor volume and weight, and losses on the power devices, which will affect converter cost, efficiency, and power density. In this paper, a three-level boost converter is adopted for single-phase PFC, which uses a much smaller inductor and lower voltage devices than the conventional boost PFC converter does, yielding high power density, high efficiency, and low cost. >

DC-DC converter design for battery-operated systems

Abstract: This paper describes performance, design and optimization of DC-DC converters for energy limited, battery operated systems. Variable-frequency operation is used to achieve voltage regulation and high efficiency for an extremely wide range of load currents. An experimental 15 W, 3.3 V buck converter has been constructed to demonstrate design and optimization techniques. The converter employs synchronous rectification to reduce conduction losses, and discontinuous, variable-frequency, current-mode control with optimum peak current to maximize efficiency for a wide range of loads. Applications include portable computers, hand-held instruments, and telecommunications. >

Soft switching active snubbers for dc/ac converters

Abstract: A soft-switching active snubber is proposed to reduce the turn-off losses of the insulated gate bipolar transistor (IGBT) in a buck power converter. The soft-switching snubber provides zero-voltage switching for the IGBT, thereby reducing its high turn-off losses due to the current tailing. The proposed snubber uses an auxiliary switch to discharge the snubber capacitor. This auxiliary switch also operates at zero-voltage and zero-current switching. The size of the auxiliary switch compared to the main switch makes this snubber a good alternative to the conventional snubber or even to passive low-loss snubbers. The use of the soft-switching active snubber permits the IGBT to operate at high frequencies with an improved RBSOA. In the experimental results reported for a 1 kW, 40 kHz prototype, combined switching/snubbing losses are reduced by 36% through the use of the active snubber compared to a conventional RCD snubber. The use of an active snubber allows recovery of part of the energy stored in the snubber capacitor during turn-off. The generic snubber cell for the buck power converter is generalized to support the common nonisolated DC/DC power converters (buck, boost, buck-boost, Cuk, sepic, zeta) as well as isolated DC/DC power converters (forward, flyback, Cuk, and sepic).

On lossless switched-capacitor power converters

Abstract: This paper addresses the design of efficient switched-capacitor power converters. The discussion starts with a review of the fundamental limitation of switched-capacitor circuits which shows that the topology of such circuits and the "forced" step changes of capacitor voltages are the inherent attributes of power loss. Although the argument follows from a rather trivial result from basic circuit theory, it addresses an important issue on the maximum efficiency achievable in a switched-capacitor power converter circuit. Based on the observed topological constraint of switched-capacitor power converter circuits, the simplest lossless topology for AC/DC power conversion is deduced. Also discussed is a simple version of lossless topology that achieves isolation between the source and the load. Finally, an experimental AC/DC switched-capacitor power converter, based on the proposed idea, is presented which demonstrates an improved efficiency over other existing switched-capacitor power converters. The proposed AC/DC power converter contains no inductors and thus is suitable for custom IC implementation for very low power applications. >

Design of the half-bridge, series resonant converter for induction cooking

Abstract: The forced commutated, half-bridge, series resonant power converter is well suited for induction cooking. A detailed analysis is made of the operation of this power converter to obtain the information needed for a complete design procedure. The values of the reactive components and the voltage and current requirements for all the power components can be calculated with this procedure for a given cooking vessel (experimental measurement of parameters needed), grid voltage and maximum output power. Experimental results are presented. >

Tracking control of buck converter using sliding-mode with adaptive hysteresis

Abstract: This paper introduces an application of sliding-mode combined with state-feedback tracking principle to control a buck converter. Instead of following an empirical method to obtain the sliding surface equation for the on-off bang-bang switching, the derivation of the control law is completely based an the fundamental tracking control laws, using the state-feedback and bang-bang control approaches. The resulting equation, if being reduced for the case of having a constant voltage reference, is similar to the sliding equation used in previous work. The control concept has proven to be more general, and can be applied to the case of having the output voltage tracking a time-varying reference signal. >

E-beam high voltage switching power supply

Abstract: A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360°/n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load.

An overall study of the half-bridge complementary-control DC-to-DC converter

Abstract: The half-bridge complementary-control power converter has been recently proposed as a low-output voltage DC-to-DC power converter due to its excellent features (efficiency around 90% at as low an output voltage as 33 volts) A study of the statics and dynamics of this power converter is proposed in this paper Thus, DC voltage conversion ratio both in continuous and discontinuous conduction mode, the boundary between both modes, the DC current level in the transformer and a small-signal average model have all been obtained From the latter, transfer functions between duty cycle and output voltage and between input and output voltages have been also obtained, and some simplifications and design rules have been proposed to facilitate the design of the feedback loop >

New, zero voltage switching, high frequency boost converter topology for power factor correction

Abstract: This paper introduces a technique for combining zero-voltage-switching with boost converter technology to enable high frequency, high efficiency operation of the converter. The combination creates a new topology which is effective to meet the power factor correction and harmonic reduction requirements of new EMC standards. The unique topology provides limitation of the recovery current of the boost diode and uses the energy recovered from the reverse current to discharge the intrinsic and stray capacitance of the boost switch while transferring this recovered energy to the output. With the main switching losses removed, the frequency can be increased to reduce the size of the boost inductor while maintaining continuous conduction mode operation for improved input noise filtering.

High efficiency resonant switching converters

Abstract: Resonant DC to DC power converter topologies include a PWM-controlled flyback converter having a single transformer and a primary side resonant subcircuit that is optimally controlled to minimize reverse recovery losses. A second transformer may be added wherein the primary windings are connected in series, the first transformer having substantially greater inductance than the second transformer to more efficiently transfer energy over a wide range of output load conditions. A combined forward-flyback resonant converter utilizing a load-side buck loop for increased power delivery performance and start-up circuitry for initial power connection of the converter to a voltage source utilizing a hysteresis protection circuit are also disclosed.

A three-switch high-voltage converter

Abstract: A novel three-switch HV converter derived from the Cuk converter is presented. This converter can operate into a capacitor-diode voltage multiplier, which offers simpler structure and control, higher efficiency, reduced EMI, size and weight savings than traditional switched-mode regulated voltage multipliers. Two significant advantages are the continuous input current and easy isolation extension. The new converter is experimentally verified. Both the steady state and dynamic theoretical models are correlated well with the experimental data. >

Series compensator inserting real and reactive impedance into electric power system for damping power oscillations

Abstract: A series compensator (11) for damping power oscillations in an electric power transmission system (1) includes a switching power converter (13) which injects a voltage into the transmission line (5) having a phase angle relative to transmission line current which is controlled to provide reactive compensation and to inject virtual real impedance into the line. The switching power converter (13) is a dc to ac converter which is capable of injecting virtual real impedance into the transmission line by virtue of the fact that it has a power exchange device (27) connected to its dc terminals (29). Where the power exchange device (27') is a resistor (37), the switching power converter (13) is capable of absorbing real power during surges in power on the line (5). Alternatively, the power exchange device (27) is a storage device (31) such as a battery bank or a super conducting magnet, in which case the switching power converter (13) can provide both virtual positive and negative real impedance.

Lamp out detection for miniature cold cathode fluorescent lamp system

Abstract: A circuit for supplying power to a fluorescent lamp. A control system comprises a buck regulator for supplying a buck current, an inverter circuit for receiving the buck current and for generating a lamp voltage, a circuit for sensing a current in a fluorescent lamp, a circuit for sensing a no lamp condition, and a controller for controlling the buck regulator and the inverter. The circuit for sensing a no lamp condition monitors a voltage level at the inverter transformer. The controller is coupled to the circuit for sensing a no lamp condition. If a no lamp condition is detected, the controller responds by shutting itself down. The controller can be reactivated by toggling an on/off signal to reset a latch.

Control of power factor correcting boost converter without instantaneous measurement of input current

Abstract: This paper proposes a new control method for the constant-frequency control of power factor correcting boost power converter using a sinewave template modulated PWM signal which eliminates the need for instantaneous measurement of the line current for the switching control of the boost converter. The control strategy is based on the notion that the line current can be forced to trace a deterministic waveform such as a sinusoid by considering the implicit model of the sinewave in the boost converter controller structure. The modulating sinewave template is generated using the line voltage, the boost converter output voltage and the load current. The paper provides the analysis and the design of the controller and presents simulation and implementation results to demonstrate its effectiveness. >

Circuit and method for achieving zero ripple current in the output of a converter

Abstract: A power converter and a method of operating a power converter. The power converter includes: (1) a transformer for receiving bipolar electrical input power from a power source, the power substantially free of dead time and (2) a hybridge rectifier coupled to the transformer and including first and second output inductors of independently selectable, differing inductance, the hybridge rectifier receiving the input power from the transformer and rectifying the input power to produce an output power substantially free of ripple current at a predetermined duty cycle operating point of the converter, the first and second output inductors being of independently selectable, differing inductance thereby to allow the predetermined duty cycle operating point to be adjustable.

DC power supply with enhanced input power factor using a buck and boost converter

Abstract: A direct current or direct voltage power supply operating from a mains AC line is corrected for power factor so that the maximum power can be extracted from the source. The AC line is full-wave rectified, filtered and the resulting pulsating direct voltage is applied to a buck/boost switched inductor switched at a frequency higher than the line frequency. The buck/boost switching action is controlled so that the switchover between buck and boost modes occurs when the instantaneous value of the pulsating direct voltage equals the supply output voltage. The inductor current in the buck mode of operation is controlled to have an input voltage-squared characteristic; the inductor current in the boost mode is controlled to have an input voltage-proportional characteristic. The resulting average current makes the AC line current substantially proportional to the AC line voltage, to achieve substantially unity power factor.

Contactless battery charging system with high voltage cable

Abstract: A high voltage cable system for use with a contactless battery charging system that charge propulsion batteries of an electric vehicle, and the like. The contactless battery charging system includes a primary power converter coupled to a power source and a secondary power converter located on the electric vehicle that is coupled propulsion batteries of the electric vehicle. The primary and secondary power converters are connected by way of a coaxial power cable. An isolation transformer is coupled between the output of the primary power converter and the coaxial power cable. This transformer allows one of the two outputs of the primary power converter to be connected to ground potential. The isolation transformer improves the safety and reduces electromagnetic interference (EMI) when coupling power to the secondary power converter. The isolation transformer 30 allows for the use of a stepped-up voltage level to be used in the primary power converter, which reduces the amount of current in the coaxial power cable required to deliver power to the secondary converter. This allows a much higher charge power to be delivered to the electric vehicle using a reasonably sized coaxial power cable.

Redundant power supply system

Abstract: A redundant power supply system so contrived that, upon occurrence of a fault in any one power unit, the other power unit is capable of performing relief power supply to a load. The power supply system comprises an AC-DC converter for converting an AC voltage to a DC voltage, and a plurality of power units connected in parallel to the output side of the AC-DC converter. Each of the power units includes a power source for feeding the load with a stable DC output corresponding to the DC voltage; a fuse connected to the input side of the power source for cutting off a power line; a coil connected in series to the fuse; and a capacitor connected between a line, which is disposed between the fuse and the coil, and another line between the output side of the AC-DC converter and the input side of the power source.

A detailed R-L fed bridge converter model for power flow studies in industrial AC/DC power systems

Abstract: Because of lower voltage levels and smaller power ratings, the R/X ratio of commutation impedance in industrial AC/DC distribution systems is usually higher than that in HVDC transmission systems. Considerable discrepancies may therefore occur in industrial AC/DC power flow results, especially the reactive power consumption of converters, if the commutation resistances of the converters are neglected. To describe the effects of commutation impedance on converter operations and to precisely relate the fundamental line current and DC output current of the converter, a detailed model of the bridge converter with commutation impedance for use of Newton-Raphson power flow studies in industrial AC/DC power systems is derived in this paper. A coal mine power system and a DC electrified transit railway system with regenerative braking function, a part of Taipei Rapid Transit Systems under planning, have been analyzed to show the improved accuracy and good convergence characteristics of the developed Newton-Raphson power flow formulation with the proposed converter model. >

Three-phase step-down reversible AC-DC power converter

Abstract: Bidirectional DC current flow is not a natural feature of the buck (step-down) switch-mode rectifier, which leaves it at a disadvantage to boost (step-up) designs. A circuit topology is presented that allows bidirectional flow and which, by dual use of components, uses fewer devices than anti-parallel bridges. Sinusoidal current, controlled displacement factor, and variable voltage transfer ratio are demonstrated in a 1.5 kVA prototype. Dynamic performance is investigated through simulation and experiment. A PI plus velocity controller is shown to be adequate provided care is taken over changing between rectification and inversion.

Boost converter power supply with reduced losses, control circuit and method therefor

Abstract: A boost converter power supply circuit (11) uses energy from a diode recovery current (Id5) which flows in a blocking diode (D5) at diode commutation to discharge a capacitance associated with the main switch (S1) of the boost converter (11) in order to achieve zero voltage switching The diode recovering current (Id5) is initially captured in an inductor (L2), is then transferred to a capacitor (C2), and is then transferred back to the inductor (L2) prior to the main switch (S1) being switched on

A three-phase series-parallel resonant converter-analysis, design, simulation, and experimental results

Abstract: A three-phase DC-to-DC series-parallel resonant converter is proposed and its operating modes for a 180/spl deg/ wide gating pulse scheme are explained. A detailed analysis of the converter using a constant current model and the Fourier series approach is presented. Based on the analysis, design curves are obtained and a design example of a 1-kW converter is given. SPICE simulation results for the designed converter and experimental results for a 500-W converter are presented to verify the performance of the proposed converter for varying load conditions. The converter operates in lagging power factor (PF) mode for the entire load range and requires a narrow variation in switching frequency, to adequately regulate the output power.

Current-source parallel-resonant DC/DC converter

Abstract: This paper introduces, analyzes, and experimentally verifies a novel DC/DC converter called the current-source parallel-resonant converter. The converter consists of a large choke inductor, two switches, and a parallel-resonant circuit. Each switch consists of a MOSFET in series with a diode. It has a nonpulsating input current with a very low AC ripple. The MOSFETs are driven with respect to ground and, therefore, have a simple gate-drive circuit. The analysis of the converter is carried out in the frequency domain using Fourier series techniques. Analytical expressions are derived for performance parameters of the converter. A prototype of the converter circuit was designed, built, and tested. The theoretical results were in good agreement with the experimental results. >

Experimental control of chaotic behavior of buck converter

Abstract: The authors report a method for control of chaos in the DC-DC buck converter. The method differs from the existing ones and is particularly useful for piecewise linear systems with switching nonlinearity. >

Power converter with overvoltage protection

Abstract: A switched power converter for a recreational vehicle includes a housing and a switched power supply. The switched power supply has a switch and at least one energy storage component, the switch controlling the supply of power to the energy storage component. The output of the energy storage component is a regulated DC output voltage. A controller generates a switching control signal for controlling the state of said switch. A protection circuit is connected to the controller for protecting the switched power supply from damage resulting when a reverse battery connection is made. The circuit also includes a controller for controlling the pulse-width of the control signals input to the switch. A fan may be provided on the housing which is selectively enabled to move cooling air over the switched power supply only when a detected temperature exceeds a threshold level. The controller may be disabled when an ambient temperature exceeds a threshold level. An optical coupler is utilized in a voltage feedback circuit. The voltage feedback circuit is compared to a current level to control the pulse-width of the pulse signal supplied to the switch. An overvoltage protection circuit is connected to the controller for protecting the switched power supply from damage resulting from an overvoltage condition.

Full wave buck-boost power converter with buck power converter properties

Abstract: A continuous mode full wave power converter topology which integrates the buck-boost (flyback) and buck converter properties. The voltage transfer function is M = (D/(1-D)), characteristic of the buck-boost (flyback) converter. Characteristic of the full wave buck converter, the inductor current is source continuous during the alternate D intervals, source discontinuous during the simultaneous (1-D) intervals, and load continuous during both the D and (1-D) intervals. A continuous mode full wave power converter topology which integrates the buck-boost (flyback) and buck converter properties. The voltage transfer function is Eout = Ein (D/(1-D)), characteristic of the buck-boost (flyback) converter. Characteristic of the buck converter, the inductor current is source continuous during the alternate D intervals, source discontinuous during the simultaneous (1-D) intervals, and load continuous during both the D and (1-D) intervals.

Digital control of a ZVS full-bridge DC-DC converter

Abstract: The paper describes the design and realization of a digital controller for a DC-DC power converter with zero-voltage switching (ZVS). The chosen power converter, usually called the phase-shifted bridge, is valuable because it combines advantages from both conventional PWM and resonant-mode power converters. It is therefore an important topology for investigating the advantages of digital control for DC-DC power converters. The power converter's control equations are nonlinear. The paper explains how the digital technique simplifies the separation of large-signal and small-signal control of the power converter. The loop updates at 25 kHz, and experimental results show the dynamic response achieved. >

Charge redistribution analog-to-digital converter with system calibration

Abstract: A charge redistribution analog-to-digital converter. This converter includes an offset correcting circuit operatively connected in parallel with a capacitor array and responsive to a sampling input of the analog-to-digital converter, and a gain correcting circuit operatively connected in parallel with a sampling capacitor and responsive to the sampling input of the analog-to-digital converter. In another general aspect, an analog-to-digital converter calibration method for a charge redistribution analog-to-digital converter, that includes adjusting an input offset of an input of the analog-to-digital converter and adjusting a gain offset of the analog-to-digital converter. The steps of adjusting are then repeated until a predetermined level of error is achieved for the analog-to-digital converter.

Voltage-follower control in zero-current-switched quasi-resonant power factor preregulators

Abstract: In this paper, we propose to study the use of several zero-current-switched (ZCS) quasi-resonant converters (QRCs) (buck-boost, flyback, SEPIC, Cuk, boost, and buck) with a half-wave switch, working as power factor preregulators (PFPs) with voltage-follower control. The analysis carried out demonstrates that these converters show excellent characteristics to obtain a high power factor (PF) without using any input-current feedback loop, and they also allow high switching frequency to operate because they integrate transformer and rectifier diode parasitics into the power topology.