Showing papers on "Buck converter published in 1990"

Zero-voltage switching technique in DC/DC converters

Abstract: A novel resonant switch operating under the principle of zero-voltage switching is presented. The basic configurations of the voltage-mode resonant switches are presented. The circuit's operating principles are described using a voltage-mode quasi-resonant boost converter. DC analysis of the converter is carried out. A new family of voltage-mode quasi-resonant converters are derived, and several members of this family are presented. The duality relationship between the zero-current switching technique and the zero-voltage switching technique is derived. These two techniques are compared using an example showing the duality between a current-mode quasi-resonant Buck converter and a voltage-mode quasi-resonant boost converter. The similarities and differences of the voltage-mode quasi-resonant converters and the Class-E converters are discussed. A 5 MHz 50 V to 5 V flyback converter employing the zero-voltage switching technique has been implemented. Design considerations and experimental results of this circuit are presented. >

Design of a simple high-power-factor rectifier based on the flyback converter

Abstract: An equivalent circuit model for the discontinuous conduction mode flyback converter based on the loss-free resistor concept is presented. This simple model correctly describes the basic power processing properties of the converter, including input port resistor emulation, output port power source characteristics, and control characteristics. Based on this model, steady-state design equations are described and are used in a design example. Design of the slow output voltage feedback loop is also considered. A small-signal AC model is developed for both the resistive load and the DC-DC converter-voltage regulator load cases. In addition, a simple first-order approximation for the line current distortion and phase shift caused by 120 Hz duty cycle variations is derived. >

A new continuous-time model for current-mode control with constant frequency, constant on-time, and constant off-time, in CCM and DCM

Abstract: A novel small-signal model for current-mode control of PWM (pulse width modulation) converters is extended to the analysis of converters with constant on-time control, constant off-time control, and discontinuous conduction mode (DCM). Constant on or off-time converters in continuous conduction mode (CCM) have two complex right-half-plane (RHP) zeros in the current loop feedback, but reduced modulator gain eliminates current-loop instability. The modulator gain exhibits a frequency-dependent phase which introduces an extra gain term in the circuit model. The new model for DCM operation does not have RHP zeros in the current feedback loop, but the buck converter exhibits an instability for higher conversion ratios. >

Analysis, simulation and experimental study of chaos in the buck converter

Abstract: A buck DC-DC power converter, whose input voltage is controlled by naturally sampled, constant-frequency PWM (pulse width modulation), is operated in the continuous conduction mode. Two versions are treated, a first-order and second-order circuit. Their behavior is modeled analytically and numerically. For certain values of the circuit parameters instability occurs. Strange phenomena of multiple pulsing, shipped cycles, subharmonics, and chaos are predicted theoretically and observed experimentally, including a period-doubling route to chaos. There is good agreement between theory and experiment. >

Analysis and design of a series-parallel resonant converter with capacitive output filter

Abstract: The objectives are to propose a LCC-type parallel resonant power converter with a capacitive output filter, to present its different operating modes and analyze the converter for these modes, to obtain design curves based on the analysis to present a simple design procedure for the proposed converter, and, finally to provide experimental results. A high-frequency link series-parallel resonant power converter with capacitive output filter is proposed and analyzed using the state-space approach. Analysis shows that the converter enters into three different modes. The normalized load current and other component stresses are plotted against the converter gain. Detailed experimental results are presented to verify the theory. >

A 500 kHz multi-output converter with zero voltage switching

Abstract: A detailed analysis of topological modes of the converter and its relation to the design, development, and performance of a multioutput prototype converter are given. The implemented topology is found to be a good solution for eliminating converter switching losses at high frequencies. The breadboarded converter demonstrates the zero voltage switching very clearly, resulting in improved efficiency. The implementation of the circuit was relatively simple and was not susceptible to noise problems associated with high-frequency converters. >

A fast time-domain algorithm for the simulation of switching power converters

Abstract: An efficient algorithm for the simulation of switched-mode power converters is developed. A Chebyshev series expansion is used to effectively solve the differential equations describing the system in each topology. The power of the new simulation technique lies both in the simple, but accurate, polynomial approximation for the state transition matrices and in the ability to explicitly obtain the instants at which the switching of the circuit topology takes place. The simulation technique is illustrated with reference to a simple Buck converter operating at a constant frequency. The derivation of the new algorithm is presented and its performance is analyzed. The case of a rapidly varying input forcing function is analyzed. Examples illustrating the generality and the computational efficiency of the algorithm are presented. >

Application of magnetic energy storage unit as continuous VAr controller

Abstract: It is shown that magnetic energy storage units can simultaneously operate as continuous VAr (volt-ampere reactive) controllers while performing the role of load-frequency stabilizers in electrical power systems. This is achieved by operating the converter in the buck-boost mode with a switched capacitor bank placed across its terminals. The P versus Q modulation ranges of the 12-pulse converter depend on the source inductance, secondary voltage of the input transformers, and output current. Once the input transformer is chosen, the Q modulation range depends on the active power transfer and the current through the inductor at any instant of time. The actual reactive power consumption of the converter is varied continuously, depending on the requirements of the power system, while keeping within the Q-modulation range. Switching of the capacitor bank keeps the required Q consumption of the converter within the available range. It is shown that this mode of control improves the overall performance of the power system in P-f and Q-V loops and obviates the use of any additional VAr compensator in the power area where the SMES (superconducting magnetic energy storage) unit is located. >

Current distribution control of converters connected in parallel

Abstract: Two schemes of current distribution control in a system of power converters connected in parallel, master-slave and central-limit controls, are analyzed from system block diagrams to determine steady-state distribution errors The performance characteristics of distributive power systems using these two control techniques are presented The comparison between the system performances with and without these distribution controls is discussed The results of a FORTRAN program written to simulate the responses of two buck converters connected in parallel are described It is shown that the master-slave technique provides good current distribution but no control in the output current overshoots that occur in the output of the master converter The central-limit current distribution control is shown to provide tight control to all currents in the converters towards the central-limit reference signal that is the weighted average of the total current to the shared load Therefore the central-limit technique is regarded as superior to the master-slave technique >

Zero-voltage resonant transition switching power converter

Abstract: A single-ended DC-to-DC power converter which is operative at very high switching frequencies with zero-voltage resonant transition switching. A single magnetic element functions as both a storage inductor and a transformer. A charging capacitor is switched to induce a reversal current through the inductor for providing the zero-voltage switching function. Control to output characteristics are identical to those of conventional buck and buck-boost converters. The invention provides efficient, high-frequency operation and isolation of the output from the input power source with minimal component volume. The control system is adaptable to constant frequency pulse width modulation for voltage regulation.

Switched capacitor interleaved forward power converter

Abstract: A DC-to-DC power converter topology utilizing parallel connected transformers in a buck switching configuration with each stage operated 180° out-of-phase, with the primary windings of the transformers sequentially feeding into a common filter capacitor. On each transformer, a secondary winding is switched to a load at the time the primary winding is shunted across the filter capacitor. The circuit provides dual inductor buck power stage operation while maintaining input-output isolation. Interleaved power processing provides continuous capacitance support for the output voltage produced by the power supply.

Optimal feed-forward compensation for PWM DC/DC converters

Abstract: An analytical procedure for optimizing the feedforward compensation for any PWM (pulse width modulation) DC-DC converter is described The aim of achieving zero DC audio-susceptibility was found to be possible for the buck, buck-boost, Cuk, and SEPIC cells; for the boost converter, however, only nonoptimal compensation is feasible Rules for the design of PWM controllers and procedures for the evaluation of the hardware-introduced errors are given A PWM controller implementing the optimal feedforward compensation for buck-boost, CUK, and SEPIC cells is described and experimentally characterized >

Inverse dual converter (IDC) for high power DC-DC applications

Abstract: The inverse dual converter (IDC), suitable for high-power DC-DC conversion applications, is presented. The IDC is a voltage source converter with an AC link and has been derived from an inductor converter bridge. This capacitor commutated converter is capable of continuous voltage step-up or step-down control over a wide range without the need of a transformer. In addition to high-frequency switching the converter is characterized by soft switching techniques, reducing constraints on the ratings of the switches. The average model developed with the help of gyrator theory provides sufficient information for control strategies and design considerations. The results of gyrator modeling and computer simulation are compared with experimental results obtained from a prototype IDC. >

High-efficiency, high-density, power supply including an input boost power supply

Abstract: A power supply includes a dc-to-dc converter with an integral boost power supply for maintaining the effective converter input voltage within a predetermined steady-state range, even if the input voltage to the power supply exhibits substantial voltage transients. In one preferred embodiment, the boost power supply comprises a boost transformer and a rectifier, and the converter comprises two parallel-coupled resonant converter modules, each including either a half-bridge or full-bridge connection of switching devices and a resonant circuit. The primary winding of the boost transformer is coupled between the junctions joining the switching devices of the resonant converter bridges. When the power supply input voltage is outside the steady-state voltage range, the boost power supply is activated by phase shift control of the voltage across the primary winding of the boost transformer.

Power supply with multiple outputs and load balancing

Abstract: A power supply with multiple outputs including at least two power converters, each with multiple outputs, a first output of a first power converter being connected in parallel with a first output of a second converter to provide a first load with current. The power supply further includes a first regulating circuit for delivering to each power converter a command signal that is a function of the current delivered to the first load. The power supply also includes at least one other regulating circuit for delivering to an output regulator (postregulator) connected between each power converter and a load other than the first load, a command signal which is a function of the current delivered by each converter output to the load other than the first load.

Analysis and design of LCL-type series resonant converter

Abstract: A series resonant power converter modified by adding an inductor in parallel with the transformer primary (or secondary) is presented. This configuration is referred to as 'LCL-type series resonant converter'. A simplified steady-state analysis using complex circuit analysis is presented. Based on the analysis, a simple design procedure is given. Detailed experimental results obtained from a MOSFET-based 500 W converter are presented to verify the analysis. A narrow variation in switching frequency is required to regulate the output voltage constant 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. >

Power conversion system with instantaneous real power feedback control

Abstract: A voltage PWM converter/inverter system comprises a converter for converting an alternating current power input into a direct current power output and inverting the direct current power output of the converter into an alternating current power output. A smoothing circuit is inserted between the converter and the inverter and an instantaneous real power calculating unit calculates an instantaneous real power for the inverter to provide an output comprising an instantaneous real power calculated value. The system includes a converter controller for voltage PWM control of the converter based on a set converter command value, a terminal direct current voltage value of the smoothing capacitor, and the instantaneous real power calculated value. The system further includes an inverter controller for voltage PWM control of the inverter based upon a set inverter command value and the alternating current power provided as a an output by the inverter.

Sliding mode-a new way to control series resonant converters

Abstract: The application of the theory of variable structure control systems for the control of resonant DC-DC converters is illustrated. The full-bridge configuration of series-resonant converters (SRCs) is used. The converter is operated at resonant frequency to obtain both output-to-input voltage characteristics similar to those of the buck converter and high efficiency. To arrive at an exact mathematical model, the SRC is viewed as a piecewise linear system. However, under some approximations and a suitably selected set of state variables, the SRC is characterized by a linear continuous-time model which allows determination of the equivalent control via the sliding mode control (SMC) theory. To obtain a sliding regime, the appropriate sliding surface is selected by assigning poles. This control law constitutes a new approach to the control of resonant DC-DC converters. >

Enhancement-mode zero-current switching converter

Abstract: An enhancement-mode converter module, which converts power from an input source for delivery to a load in a series of quantized energy transfer cycles, includes a zero-current switching converter, an enhancement-mode controller, an an input-output port for carrying synchronizing information to and from an external synchronizing bus. The enhancement mode controller adjusts the frequency at which energy transfer cycles are triggered in the zero-current switching converter to be the greater of a first frequency, which will regulate the load voltage to a setpoint voltage, Vsp, characteristic of the enhancement-mode controller, or a second frequency, which is indicated by an input delivered to the input-output port. In an array of such enhancement mode converter modules, wherein the outputs of all of the enhancement-mode converter modules are connected together to deliver power to a load, and wherein synchronizing information carried to a synchronizing bus by the input-output port of any of the converter modules is delivered as an input to the input-output ports of the balance of the converter modules by propagation along the synchronizing bus, all of the converter modules will synchronize to an operating frequency determined by the enhancement-mode controller having the highest setpoint voltage, and each of the converter modules will deliver an essentially constant fraction of the total power delivered to the load by the array.

Analysis, optimization and design of a series-parallel resonant converter

Abstract: A high-frequency link series-parallel resonant converter is analyzed using a state-space approach. Closed-form solutions are obtained under steady-state conditions. Analysis is presented for both continuous conduction mode and discontinuous capacitor voltage mode. The converter gain and other component stresses on the output plane are presented. A method of optimizing the converter under certain constraints is presented, and a simple design procedure is illustrated by a design example. Experimental results are presented to verify the theory. >

Battery charging characteristics in small scaled photovoltaic system using resonant DC-DC converter with electric isolation

Abstract: The system described is a small-scale photovoltaic system with storage batteries. A theoretical analyses is presented of the photovoltaic system using a resonant DC-DC power converter in order to clarify a desirable circuit condition. The experimental results of the battery charging characteristics are presented. >

Comparison between state space averaging and PWM switch for switch mode power supply analysis

Abstract: The state space averaging method and the pulse-width-modulation (PWM) switch method for modeling of DC-to-DC converters are reviewed. The methods are compared through the computation and plotting of typical transfer functions of a buck converter. The state space averaging method begins by writing the state equation and the state matrices describing the system, and requires matrix operations for computation of the system transfer functions. It also leads to a canonical model that represents the four basic DC-to-DC topologies. The PWM switch method leads to a simpler circuit analysis of the converter which can be easily simulated using SPICE-like simulation programs. >

Analysis and design of a dual series resonant converter for utility interface

Abstract: The use of a dual series resonant converter with phase-shifted operation as a utility interface is presented. The inverter operates at a fixed frequency above the resonant frequency to reduce the switching losses in the devices. A simplified analysis of the converter operation is given, and a design example is worked out based on this analysis. A general-purpose power electronic converter simulation program has been used to predict the performance of the converter, and experimental results are given confirming the validity of the simulation results. >

3-Phase converter apparatus

Abstract: A 3-phase converter apparatus, in which a 3-phase A.C. power supply and a 3-phase converter operate in parallel on a common load BUS so as to share the load power, has an output voltage command generating device for generating an instantaneous command of the output voltage from the converter, and instantaneous voltage control device for controlling the converter so as to reduce the deviation of the instantaneous value of the output voltage of the converter from the instantaneous command generated by the output voltage command generating device. The converter includes at least one semiconductor switch for effecting a plurality of switching cycles in a half cycle of the A.C. power, so that the control of the phase of the output voltage of the converter with respect to the A.C. power supply is started at any moment.

Push-pull converter current limiter

Abstract: Method and apparatus for output current limitation of a push-pull d.c. voltage converter. The input current of the push-pull d.c. voltage converter is detected and integrated each switching cycle of push-pull switches in the current paths leading to the transformer of the converter. The integrated signal together with a reference signal are utilized to form a control signal for a pulse frequency modulator, the output of which controls the on-periods of the push-pull switches. The arithmetic mean of the output current of the push-pull d.c. voltage converter is thereby kept constant without additional power elements. Operation with a boost-type switch controller as a pre-regulator becomes possible without problems.

Zero-voltage-switched multiresonant converter for high-power, pulse-load applications

Abstract: A full-bridge zero-voltage-switched (ZVS) multiresonant converter (MRC) was built for a pulse load with a peak power of 1.44 kW and an average power of 360 W. The converter works with an input-voltage range from 220 to 350 V, and delivers 32 V to the pulse load with a constant peak current of 45 A. The efficiency range of the converter was measured from 82.5 to 90.5%. The maximum efficiency occurs at low line and decreases as the input voltage increases. Detailed analysis and design of the converter, along with experimental results, are presented. >

A full-bridge zero-voltage-switched multi-resonant converter for pulse-load applications

Abstract: The zero-voltage-switching multiresonant technique was used to fabricate a full-bridge converter for high-power, pulse-load applications. The complex operation of the full-bridge zero-voltage switched multiresonant converter is analyzed. The converter can operate in four modes, each representing a specific topological sequence. The DC voltage conversion-ratio characteristics encompassing all possible operating modes are derived. These characteristics are used to define a complete, step-by-step design procedure which minimizes the conduction loss in the primary side of the power stage by minimizing the RMS currents through the switches. The design procedure was used to fabricate a converter that operates at an input voltage of from 220 to 350 V and delivers 32 V to pulse load, with a peak current of 45 A. The maximum efficiency of the converter was measured at 90.5%. >

An approximate steady state and small signal analysis of the parallel resonant converter running above resonance

Abstract: A half bridge parallel resonant converter (PRC) running above resonance in the constant output voltage mode is analysed. The steady state analysis the small signal analysis, and the regulation of the power converter are reviewed. An approximated steady state analysis for the constant output voltage mode is reviewed. This analysis is based on an AC equivalent circuit using the fundamental wave of the rectangular input voltage of the resonant tank. Although approximated, the AC equivalent circuit provides physical insight into the behaviour of the PRC since the higher order harmonics of the resonant voltage across the resonant converter are negligible, if the converter operates above resonance. After steady state analysis, design considerations for the PRC running above resonances are given.

Induction motor performance when fed from single to three phase converters

Abstract: The most popular single-to-three-phase converter consists of a capacitor connected between the motor's third phase and either the live or neutral of the single-phase supply. Proper voltage balance at any one given operating point is obtainable with the autotransformer-capacitor converter (ACC), while proper balance over the entire operating range is obtainable with a variable-inductor-variable-capacitor converter (LCC). The appropriate vector diagrams of the above-mentioned converters are developed to provide insight into their operation. An assessment of the derating necessary in the presence of unbalanced voltages and currents is presented. A technique for the measurement of the negative sequence voltage is discussed. Measured results for the case when an induction machine starts directly off a three-phase supply and off the above converters are included. >

A nonlinear continuous formulation for large-signal analysis of switching DC-DC converters

Abstract: A general nonlinear continuous formulation procedure for large-signal analysis of switching DC-DC converters is presented. The method can be applied for fixed or variable frequency in either of the two conduction modes, and it is easily programmed for computer-aided analysis of DC-DC converters. A DC-AC sine generator based on a buck converter operating in constant frequency current-programmed model is used to illustrate the application of the method. >