Showing papers on "Buck–boost converter published in 1992"

Small-signal analysis of the phase-shifted PWM converter

Abstract: The specific circuit effects in the phase-shifted PWM (PS-PWM) converter and their impact on the converter dynamics are analyzed. The small-signal model is derived incorporating the effects of phase-shift control and the utilization of transformer leakage inductance and power FET junction capacitances to achieve zero-voltage resonant switching. The differences in the dynamic characteristics of the PS-PWM converter and its PWM counterpart are explained. Model predictions are confirmed by experimental measurements. >

A high-power-factor buck converter

Abstract: A high-power-factor buck converter is proposed. The converter is composed of rectifier diodes, a small input capacitor, and a buck converter. It supplies low output voltages and uses low voltage semiconductor devices and ceramic capacitors. Two operation modes exist in the converter: discontinuous and continuous inductor current modes. Analysis and experimentation show that the converter's power factor is over 0.9 in discontinuous mode by constant duty ratio operation. It is clarified that the power factor decreases to about 0.7 in continuous mode by constant duty ratio operation, and it can be improved to over 0.9 by a new input current control system. >

Steady-state performance of DC motors supplied from photovoltaic generators with step-up converter

Abstract: A simple step-up converter circuit consisting of a single power transistor and an inductor is used as an interface between a PV (photovoltaic) generator and a shunt DC motor driving a centrifugal water pump. The step-up converter allows maximum power output from the PV generator to the motor at all insolation levels. Steady-state performance of the motor is vastly improved as its input voltage and current are stabilized by the regenerative action of the converter. The PV generator operates at maximum power regardless of insolation variations. The converter duty ratio can be set at a fixed optimal value which is valid for all insolation levels. This remarkable property makes this device economically attractive since it is easy to build and does not require any insolation-dependent control as compared to other peak-power tracking devices. >

DC-DC power converter including sensing means for providing an output when the reserve power of the converter falls below a predetermined amount for a given input voltage

Abstract: A DC to DC power converter in the form of a pulse-width modulator is shown which can sense via an indication of duty cycle how much reserve power is available for loads using the present input voltage. The device is for use at the end of a telephone line where the input voltage power supply impedance can be appreciable. When the reserve power, as detected in the power converter, reaches a minimum critical level, a signal is sent out requesting the voltage supply to increase the available voltage to the power converter.

A unity power factor forward converter

Abstract: A novel means of obtaining sinusoidal, unity power factor input currents in switched mode power supplies using minimum additional components is presented. The converter is topologically equivalent to a boost converter cascaded by a forward power converter, but is realized using only a single power stage. A detailed analysis of the operation is presented. A constant frequency current mode control provides excellent transient performance at the output and sinusoidal input currents at the input. Various tradeoffs involved in the design of the converter elements and control parameters are discussed in depth. All the results are backed up by experimental waveforms from a laboratory converter. >

PWM control and input characteristics of three-phase multi-level AC/DC converter

Abstract: The authors discuss the current control and pulse width modulation (PWM) pattern generation of a multilevel power converter which is capable of producing three levels of phase voltage. In the proposed current control, fast response is realized by introducing a converter model in the control algorithm and the effect of parameter difference between the model and an actual system is compensated for through proportional-plus-integral control of current difference. In PWM pattern generation, the balance of two capacitor voltages is taken into account. For the same sampling period, the current distortion factor of the proposed system can be approximately reduced to 60% of that of a conventional two-level power converter. The prototype was made using a digital signal processor, and simulation and experimental results were compared. >

High power factor power supply

Abstract: An off-line switching power supply includes an ac rectifier and a dual-output switching converter having one output coupled between the ac rectifier and the input to the dual-output converter in order to provide a high power factor, the other output of the dual-output switching converter providing a dc voltage as the power supply output. The outputs of the dual-output converter are fully decoupled so as to allow independent control of the ac input current and the power supply output voltage. In a preferred embodiment, a full-wave ac rectifier bridge is coupled in series with the second output of the power converter via an input resonant boosting converter. A full-bridge dc-to-ac converter is coupled between the dc link and ground for providing an ac signal to excite the boosting converter and for providing another ac voltage through a transformer to an output rectifier to generate a regulated dc output voltage. The amplitude of the regulated output voltage is controlled by pulse width modulation, while active frequency control of the boosting converter is provided to control the amplitude of the ac input current. Alternatively, frequency control of the boosting converter is passive, i.e., depends on the gain characteristics of the boosting converter resonant circuit. As a result of the complete decoupling of the input boosting converter and the power supply output voltage, the off-line switching power supply is capable of drawing high quality current waveforms from the ac source while producing a regulated dc output voltage with fast transient response.

Noise Analysis of DC-to-DC Converter with Random-Switching Control

Abstract: The effectiveness of random-switching control, by which the switching-noise spectrum is spread and its level is reduced, is briefly described through experimental results. The noise spectrum by random switching is analyzed in a general approach including a noise-generation model and a switching function with a random process. Taking the normal distribution as an instance, the amount of random perturbation is quantitatively analyzed. The validity of the analysis was confirmed experimentally by a series of pulses serving as an ideal switching-noise. >

Analysis and design of a fixed frequency LCL-type series resonant converter

Abstract: A fixed-frequency LCL-type series resonant power converter which uses an inductive output filter is proposed. Steady-state analysis of the converter is presented using complex AC circuit analysis. 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. The proposed converter requires a narrow variation in pulse-width while maintaining a lagging power factor mode of operation for very wide variation in the load. >

Linear circuit models of PWM flyback and buck/boost converters

Abstract: A method for modeling PWM converters operating in continuous conduction mode (CCM) is introduced. First, static voltage and current transfer functions of the idealized switching part of the converters are found. Second, the linearization of these transfer functions at the operating point is carried out, and the idealized switching part is replaced by dependent current and voltage sources. Third, the equivalent average resistance of parasitic resistances and equivalent average voltage of offset voltage sources of switches are determined using the principle of energy conservation. The method leads to linear DC and small-signal circuit models of a PWM converter. To illustrate the method, the analysis of the PWM flyback converter is given. Design equations for DC voltage transfer function, efficiency, and small-signal characteristics are derived. >

A new high frequency, zero-voltage switched, PWM converter

Abstract: A high-efficiency, high-power-density converter operating at constant frequency and switching at zero voltage is presented. Zero voltage switching (ZVS) conditions are achieved over a broad input voltage and output current range. Continuous power transfer from the input to the output minimizes the output filter requirements, and, by using the integrated magnetics technique, high power density can be achieved. By employing the same configuration as classical pulse width modulation (PWM) topologies, a new family of ZVS-PWM converters can be derived. An experimental 5 V, 100 A converter was designed and built. The converter operates from an input voltage of 200 to 430 VDC, at a 400 kHz switching frequency. >

Master-slave half-bridge dc-to-ac switchmode power converter

Abstract: The invention pertains to a switchmode DC to AC converter, and particularly to a master-slave half-bridge converter. The slave half-bridge power converter (C1, C2, T51, T61) is controlled by a lower power self-oscillating half-bridge master converter (C1, C2, T11, T21). More particularly, the invention pertains to a high frequency ballast for gas discharge devices (H), especially, for high pressure sodium lamps (H), completed by a high voltage ignition apparatus (N32, R71, D71, C71, S71, N72, N71).

Step-up voltage converter with overcurrent protection

Abstract: A step-up converter is utilized to convert a first lower input voltage to a second higher output voltage. The circuit includes a soft start capability such that ringing due to excessive voltage and current is substantially eliminated. In addition, this converter includes an overcurrent protection mechanism if a load failure or other overcurrent condition occurs.

A new active power factor correction method for single-phase buck-boost AC-DC converter

Abstract: A current mode control technique suitable for a single-phase AC-DC converter is presented. It is shown that application of this technique to a single-phase AC fed buck-boost AC-DC converter yields a sinusoidal input current waveform at unity input power factor. The proposed converter retains this property even under distorted AC input voltage conditions. In addition, the proposed technique offers definite advantages over the conventional boost converter and it is easy to understand, is easy to implement, and draws sinusoidal input current from the AC source for any DC output voltage condition. That is, the DC output voltage may be less than the peak AC input voltage. Furthermore, the proposed technique attenuates substantially the low-frequency harmonic components of the rectifier input current while shifting the unwanted harmonic components near the switching frequency. These unwanted high-frequency components can be easily filtered out using lightweight filter components. >

Series resonant converter with third-order commutation network

Abstract: To compensate for the poor output voltage regulation of the series resonant converter (SCR), a converter is derived by adding an inductor in parallel with the resonant capacitor of the conventional SCR. The resulting converter is called the LLC-SRC. This converter is analyzed via a two-dimensional state-plane diagram through a proper transformation of its state variables. Based on the analysis results, a set of characteristic curves is derived showing that the control characteristics and component stresses of the new converter are improved compared with those of a conventional SRC. Based on these curves, the design procedure for the LLC-SRC is formulated. The experimental results from the breadboard model were used to verify the theoretical work. >

AC to DC converter having an enhanced power factor

Abstract: The invention relates to an AC to DC converter having an improved power factor achieved by combining boost converter operation at the beginning and ending of each half wave of the AC input waveform, with passive operation at the middle portion of each half wave. The timing of the operation is based on comparing the instantaneous voltage with a stored average voltage, which has the effect of making boost converter operation go off at a fixed angle after the beginning of each half wave and go on at a fixed angle before the ending of each half wave, the angles being independent of the average AC voltage. The converter increases the power factor to a value between 90 and 97% and reduces the current waveform distortion to between 15 and 29%.

A phase-shift modulated double tuned resonant DC/DC converter: analysis and experimental results

Abstract: Analysis, design, and experimental results of a double-tuned resonant DC/DC converter are presented. The resonant circuit employed in the converter consists of a series branch in which an inductor and a capacitor are connected in parallel. The components of both branches are tuned at the operating frequencies of the converter. The proposed resonant circuit provides reduced switching and conduction losses for a wide range of input voltage and output load variations. A detailed description of the converter circuit, explaining operating modes, it is given. A prototype converter was built. It operates at a 256 kHz clock frequency and delivers 5 V, 100 A DC from a nominal 48 V DC input. Experimental results show an overall efficiency of about 86% from full-load to 1/4 load. >

Synchronized switch tapped coupled inductor regulation circuit

Abstract: A synchronized switch tapped coupled inductor circuit which couples a first closed-loop regulated output of a forward converter switching power supply to a second output to assist in regulating the voltage of the second output. The switched power supply includes a converter transformer which is implemented as a forward converter providing the multiple outputs. The second output includes a storage inductor which is coupled to a storage inductor of the first output. The second coupled inductor includes a center tap which is connected to a synchronized switch. The synchronized switch is further connected to the first output and coupled to the converter transformer to detect the forward and flyback portions of each cycle. During the flyback portion of each cycle, the switch is turned on coupling the center tap to the first output. During the forward portion of each cycle, the switch is turned off, isolating the outputs from each other.

Application of a constant-output-power converter in multiple-module converter systems

Abstract: The origins of the current-sharing problem of parallel-converter systems and the dual problem of voltage sharing in series-converter systems are explored. Both problems are 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, and that converters which behave neither as current nor as voltage sources can share a load equally in an a*b array of converters. One class of converters useful in such systems is that characterized by constant output power (e.g., the clamped series resonant converter). Furthermore, it is shown that constant output power converters are a subset of a broad class of converters whose output voltage is load-dependent, all of which exhibit particular load-sharing good voltage- and current-sharing characteristics. The characteristics of discontinuous mode PWM converters as well as conventional and clamped series resonant converters are examined in detail. A small-signal model of the modular converter system is developed. Experimental results are given. >

Large-signal feedback control of a bidirectional coupled-inductor Cuk converter

Abstract: Under conditions of order reduction, a nonlinear control of a bidirectional coupled-inductor Cuk converter suitable for large-signal applications is presented. The converter is accurately modeled as a second-order bilinear system, and the conditions for local controllability are established. The integration of converter state equations and the subsequent introduction of a linear recurrence between the output variable and an external reference signal lead to a nonlinear control law that is implemented by means of an analog divider, standard operational amplifiers, and a pulsewidth modulator. As a result, the output variable proportionally follows the reference signal, thus allowing different types of power waveforms in the converter output to be obtained. Experimental results verify the theoretical predictions. >

Class e fixed frequency converter

Abstract: A two-stage, Class E, fixed frequency, resonant, DC-to-DC power converter employing phase-shift control achieves outstanding performance over a full range from no load to full load. Each stage of the DC-to-DC power converter comprises a series inductor-diode network in parallel with a feed choke. Such network is connected between a power source input and a switching transistor, and it provides a fast discharge path for a resonant capacitor and lossless turn-on of the switching transistor in each power converter stage.

High performance AC/DC converter for high frequency power distribution systems: analysis, design considerations and experimental results

Abstract: This paper presents a description and analysis of a new AC/DC converter topology for use in the high-frequency power distribution system in Space Station Freedom. Steady-state analysis of the converter is provided, the performance characteristics presented, and transient behavior studied. The proposed converter has close-to-unity rated power factor (greater than 0.98), low total harmonic distortion in input current (less than 5%), and high conversion efficiency (greater than 96%). Finally, to verify the proof of-concept, a bread-board converter was built. >

Optimal control and appropriate pulse width modulation for a three-phase voltage DC-link PWM converter

Abstract: Novel control strategies are presented which use all allowed switching operations of the three-phase voltage DC-link pulse width modulation (PWM) converter such that the converter has a line-friendly performance from the point of view of the utilities or the consumer In the case of an ideal converter and a distortion-free supply network, the power factor becomes equal to unity under steady-state conditions and the dynamic characteristics of the control system are sufficient In order to reach this line friendly performance with an existing converter and to keep the expenditure for the line-side filter low, appropriate PWM at a high switching frequency (>10 kHz) is necessary The theory of the control strategies and appropriate PWM are presented Practical results obtained with an insulated-gate bipolar transistor (IGBT) converter illustrate the dynamic and steady-state performance of the new control system in both energy-flow directions >

Cascaded rectifier and two switched voltage converter circuits with harmonics suppression

Abstract: A power supply circuit includes a cascade arrangement of a full-wave rectifier and a first and a second switched voltage converter. The input terminals of the first voltage converter receive a rectified supply voltage. The second switched voltage converter has input terminals connected to a first storage capacitor of the first voltage converter. The second voltage converter includes the output terminals of the power supply circuit. A control circuit controls the period of conductance of the controlled switches of the switched voltage converters with a switching period which is much shorter than the cycle period of the AC supply voltage. A first inductive element is connected via a first controlled switch across the output terminals of the full-wave rectifier during a part of the switching period. A first rectifier diode is connected to the first inductive element so that the diode is non-conducting during this part of the period and, during the period when the diode is conducting, the diode current does not flow to the input terminals of the first switched voltage converter.

Single stage power factor corrected converter having isolated output

Abstract: A power converter is operative to reduce harmonics at an AC input by controlling its power switching so that a current waveform in a switched inductor is substantially identical to a rectified version of the input AC voltage waveform. The voltage spikes induced by the switching of the inductor into circuitry that includes the leakage inductance of a power transformer are subdued by circuitry that absorbs the initial voltage spike temporarily and then delivers that energy to the output load of the converter.

Switching pulsed resonant DC-DC converter power amplifier

Abstract: A single sided dc-dc converter utilizes a switched resonant circuit having pulsed currents and voltages. A pair of MOSFET switches are used to alternately charge a capacitor in series with an inductor from an input voltage source, and then to discharge the capacitor through a second inductor into an output capacitor. The charge and discharge currents are in the form of pulses, and flow in the same direction into the output capacitor to directly establish the output voltage. Both the "on" and "off" switching of each of the MOSFET switches is accomplished at zero current. For a given input voltage source, the output voltage of the converter is determined by the size of the output capacitor and the repetition rate of the "on-off" charge-discharge sequences. The voltage output of the converter is monitored, and a controller responsive to changes in the output voltage varies the repetition rate of the charge-discharge cycle to maintain constant voltage output. For increased current capability, a series of converters have their outputs connected in parallel. In addition to a controller simultaneously controlling the repetition rates of the paralleled converters, a sequencer connects and disconnects converters as load conditions dictate. Each converter is inherently capable of withstanding a short circuit applied to its output without suffering damage, and each converter returns to full operation on removal of the short.

Voltage control of super high-speed reluctance generator system with a PWM voltage source converter

Abstract: A voltage control system for a reluctance generator with a PWM voltage source converter is proposed. A phasor diagram of the generator is developed by introducing an iron loss conductance. A practical method for achieving optimal efficiency over the complete operating range is suggested. It is based on the optimal-efficiency current angle tracking by adjusting the voltage ratio of AC-to-DC voltage. The performance of the system is investigated by using the new phasor diagram. It is shown that a system with a PWM converter has wider operating range than one with a self-commutated six-pulse converter. The proposed control system is realized on a laboratory prototype, where control routines are mainly implemented by a 16 b single-board microcomputer. Experimental results show that 10% or more improvement compared with that of the system fed by a six-pulse converter is obtained at half full load. >

Reducing the semiconductor losses in a matrix converter

Abstract: The authors look at the implementation of a matrix converter switching strategy under microprocessor control and using IGBTs. The effects of different switching methodologies for the converter are investigated. The power losses in the switching devices of a matrix converter are analysed and quantified. The effects of different switching frequencies and approaches to PWM generation are considered. Comparisons are drawn with a conventional inverter in terms of efficiency and relative cost. The conduction losses in the matrix converter are higher than the conduction losses in a standard inverter. Methods of reducing the switching losses in a matrix converter are proposed. The implementation of these methods means that the total losses in the matrix converter can be less than those in an inverter drive at high switching frequencies. It is shown that even at lower switching frequencies the losses in the matrix converter are not significantly greater than those in an inverter drive.

Analysis and design of series-parallel resonant power supply

Abstract: A modified series-parallel high-frequency resonant DC/DC converter configuration is proposed. A simplified steady-state analysis of the converter, including the effect of a high-frequency transformer using complex circuit analysis, is presented. Based on the analysis, a simple design procedure is given. The effect of magnetizing inductances of the high-frequency transformer on the performance of the converter is discussed. Detailed experimental results obtained from a MOSFET (metal-oxide-semiconductor field-effect-transistor)-based 1-kW converter are presented to verify the analysis. The converter presented has almost constant efficiency from full load to quarter load, and the converter has load short circuit capability. >