Showing papers on "Forward converter published in 1990"

Performance characterization of a high-power dual active bridge DC-to-DC converter

Abstract: The performance of a high-power, high-power-density DC-to-DC converter based on the single-phase dual active bridge (DAB) topology is described. The dual active bridge converter has been shown to have very attractive features in terms of low device and component stresses, small filter components, low switching losses, high power density and high efficiency, bidirectional power flow, buck-boost operation, and low sensitivity to system parasitics. For high output voltages, on the order of kilovolts, a cascaded output structure is considered. The effects of snubber capacitance and magnetizing inductance on the soft switching region of control are discussed. Various control schemes are outlined. Coaxial transformer design techniques have been utilized to carefully control leakage inductance. The layout and experimental performance of a prototype 50 kW 50 kHz unit operating with an input voltage of 200 V DC and an output voltage of 1600 V DC are presented. >

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. >

A novel soft-switching full-bridge DC/DC converter: Analysis, design considerations, and experimental results at 1.5 kW, 100 kHz

Abstract: The authors present an improved soft-switching full-bridge converter which is especially suitable for high-power application (e.g. more than 1 kW output) because of its inherently high efficiency. The addition of an external commutating inductor and two clamp diodes to the phase-shifted PWM (pulse width modulation) full-bridge DC-DC converter substantially reduced the switching losses of the transistors and the rectifier diodes, under all loading conditions. The authors analyze the conditions for lossless transitions, discuss the effect of the added components on the operation of the converter, and present practical considerations and test results for a 1.5 kW converter with 100 kHz clock frequency. The converter has an efficiency above 95% at 60 V output, is free from voltage overshoots, and exhibits well-controlled transitions for all switch and rectifier voltages and currents. >

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. >

High frequency link DC/AC converter with PWM cycloconverter

Abstract: A high-frequency link DC/AC converter developed for flexible, compact, and high-efficiency uninterruptible power supply (UPS) systems is discussed. The DC/AC converter consists of a 50% duty ratio rectangular voltage output inverter, a high-frequency transformer, a pulse-width modulation (PWM) cycloconverter, and an LC filter. For this converter, a three-phase output DC/AC converter can be easily realized with only one inverter and one three-phase cycloconverter. Conversion efficiency is inherently high because the inverter can utilize zero-current switching to minimize the switching loss. Output waveform control is improved because the dead time in the cycloconverter PWM can be eliminated. The main circuit configuration, the PWM method of the cycloconverter used to obtain a sinusoidal output voltage and the switching method of the inverter are described. The experimental results of a 1 kVA DC/AC converter using a high-frequency link of 20 kHz in both single-phase and three-phase output are discussed. >

A two switch high performance current regulated DC/AC converter module

Abstract: A high-performance current regulated single-phase DC/AC converter module is proposed in this paper. Its novel features include: a two-switch topology with no "shoot-through" paths, high input to-output voltage gain, low and constant switching frequencies, and practically instantaneous recovery from input or output transients. Moreover, by utilizing an inner filter capacitor current control loop the proposed module can maintain nearly perfect sinusoidal output voltages even with highly nonlinear loads. Furthermore, three-phase operation can be obtained easily by using three of these modules. Finally, the paper includes the analysis and design of the converter power and control circuits and the experimental evaluation of key predicted results. >

Control strategy for multi-module parallel converter system

Abstract: A systematic control-loop design procedure for a multimodule converter system for high-current, low-voltage applications is presented. A small-signal model of the system is derived using the PWM (pulse width modulation) switch model and the small-signal model of the current mode control. The small-signal model for the multimodule converter system is simplified to a equivalent single-module model. The control-loop design is implemented using the single-module model. A three-loop control strategy for the multimodule converter system with a secondary output filter is developed. Significant improvements of small-signal performance and module-failure response are achieved using additional feedback from the intermediate filter stage. The small-signal analysis of the three-loop controlled converter is performed, focusing on the effects of the local voltage feedback on the closed-loop performance of the system. It is shown that local voltage feedback minimizes any detrimental effect of the resonance between the power stage filter of each converter module and the common output filter. >

Fixed frequency single ended forward converter switching at zero voltage

Abstract: A single ended forward DC-to-DC converter is operated with a main switch in series circuit with a primary winding of the isolation transformer and an auxiliary switch for charging a reset capacitor also in circuit with said primary winding. The main switch and auxiliary switch are operated through control logic so that neither switch is ON at the same time. A predetermined dead time is provided between turning OFF the auxiliary switch and turning ON the main switch to allow the output capacitance of the main switch to discharge into the secondary of the transformer. Current discharge into the secondary of the transformer during this time period is limited either by a saturable reactor in series circuit with the secondary or a selectively controlled rectifier.

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. >

Constant frequency resonant DC/DC converter

Abstract: A constant frequency full resonant mode dc/dc converter is provided, suitable for use in low voltage, high current dc power distribution systems. The converter comprises a full-bridge inverter, a resonant circuit, an output transformer, an output diode rectifier, a dc output filter, and a control circuit. The resonant circuit consists of a series branch and a parallel branch. The components of the series branch are selected such that close-to-maximum voltage gain and a near load independent output voltage of the converter are achieved. The components of the parallel branch are, however, chosen to obtain an overall lagging current at the output of the full-bridge for a desired range of output voltage control and no-load to full-load operating conditions.

DC to DC converter with steady control of output DC voltage by monitoring output DC current

Abstract: A constant dc current supplying circuit comprises a dc voltage supply, an inverter providing an ac voltage from said dc voltage, and an ac-to-dc converter providing a dc current from the inverter output and supplying the resulting dc current to a load The inverter includes a switching element driven to turn on and off in order to repetitively interrupt the dc voltage for producing the dc current of which level is determined by on-off time ratio of the switching element A comparator is included to compare a level of the dc current supplied to the load with a predetermined reference level so as to provide a first output and a second output when the dc current level is below and above the reference level Also included in the circuit is a feedback controller which generates first and second feedback control signals, respectively in response to the first and second outputs from the comparator The first and second control signals are defined as a train of pulses of varying duty ratio in order to increase and decrease on-off time ratio of the switching element depending upon the sensed output dc current level, whereby controlling to gradually increase and decrease the output dc current towards the reference level for maintaining the dc current thereat

Time reversal duality and the synthesis of a double class E DC-DC converter

Abstract: The principle of time reversal duality is introduced and applied to DC-DC power converters. Elementary inverters and rectifiers are time reversal duals of each other. When coupled together by a reactive matching network, a DC-DC converter whose properties are determined largely by the matching network is formed. This approach has application in the analysis and syntheses of PWM (pulse width modulation), resonant, quasi-resonant, and multiresonant converters. It is used here to synthesize a Cuk converter, and a double class E DC-DC power converter in which the switch and diode both operate in class E. The converter is ideally lossless for any DC load including open and short circuits. >

Constant-frequency zero-voltage-switched multi-resonant converters: analysis, design, and experimental results

Abstract: The multi-resonant-switch concept is modified to provide constant-frequency operation Complete DC analysis and designs of the constant frequency forward and half-bridge multi-resonant converters are presented Different implementations for the half-bridge topology are discussed The performances of a 50 W forward converter and a 100 W, offline, half-bridge converter are also presented A significant constant improvement of the performance of the constant-frequency zero-voltage-switched multi-resonant converter is expected from the development of MOSFETs with very low on-resistance (synchronous rectifiers) >

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. >

DC analysis and design of forward multi-resonant converter

Abstract: A DC analysis of the forward zero-voltage-switching multiresonant converter is presented. The voltage conversion ratio characteristics and semiconductor device voltage and current stresses are characterized. The results of the analysis are verified by experiments and SPICE simulation. It is found that to minimize the current and voltage stresses, the characteristic impedance must be maximized and the ratio of the primary to secondary resonant capacitances must be minimized. Based on the analysis, a procedure for designing the resonant tank with minimum current and voltage stresses is established. >

Analysis and design of a parallel resonant converter including the effect of a high-frequency transformer

Abstract: A high-frequency (HF)-link DC-DC parallel resonant converter (PRC) operating above resonance is analyzed using the state-space approach. The analysis includes the effect of the leakage and magnetizing inductances of the high-frequency transformer. Steady-state solutions are derived and used to obtain the design curves. A method of obtaining an optimum operating point under certain constraints is developed and used as the basis of a simple design procedure. The analysis shows that including an HF transformer introduces a new mode of operation in between the two general steady-state modes. Experimental results obtained with a MOSFET-based PRC for three different transformer turns ratios are presented to support the theory. Efficiencies of about 89% were obtained for 985 W, 115 V, and 230 V output converters, whereas an efficiency of about 86% was obtained for a 15 V, 63 A converter. It was observed that the introduction of the transformer considerably affected the performance, especially in the case of low output voltage and large load current converters. >

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.

DC-DC converter and a computer using the converter

Abstract: In order to provide miniaturization and increased-frequency operation of a DC-DC converter used with a computer, etc., a capacitor is connected in parallel with a switching element when the switching element is turned off to reduce turn-off loss. When the switching element is turned on, the capacitor and a DC power source are connected in series to supply the energy stored in the capacitor to a load circuit to result in a high initial voltage being applied across the load circuit.

Coupled inductor type dc to dc converter with single magnetic component

Abstract: A coupled inductor type boost DC to DC converter with a single multipurpose magnetic component. The invention includes a conventional switch for converting an input DC voltage to a signal having a time varying waveform. The switch Q1 has a pole terminal connected to a source of input voltage, a control terminal and first and second throw terminals. The single inductive element includes a first winding LN1 connected between an output terminal of the switch and an input terminal of the converter and a second winding LN2 connected between the second throw terminal of the switch and an output terminal of the converter. In a first embodiment, the invention further includes a winding LN3 of the inductive element connected at a first end to the control terminal of the switch which provides a level shifting circuit for shifting the level of a drive signal applied to the control terminal of the switch.

Control method for PWM converter

Abstract: In the control method for a PWM converter according to the present invention, an upper limit value of an inphase component of an instruction voltage for controlling an AC/DC converter is prescribed, and in the region where the upper limit value is exceeded, the inphase component of the instruction voltage is controlled to be within the prescribed upper limit value by setting a reactive component value corresponding to the exceeding quantity. This makes it possible to offer a low priced, stable control method for a PWM converter.

DC/DC switching converter circuit

Abstract: A two switch, DC/DC converter provides sufficient inductive energy storage at the termination of the "on" period of each switch to alter the charge on the intrinsic and stray capacitance of the combination of switches producing zero voltage across the alternate switch prior to its turn on. A short dead-band between the turn on pulses provided by the control circuit allows time for this transition. Thus the energy stored in the capacitance of the switches is returned to the source and load rather than being dissipated in the switching devices. This greatly improves the efficiency of the converter particularly when operating at high frequency. The unique topology of the converter provides other new and useful characteristics in addition to zero voltage switching capability such as operation at constant frequency with pulse-width-modulation for regulation, quasi-square wave output current, and the ability to integrate the magnetic elements with or without coupling.

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. >

High-frequency multi-resonant converter technology and its applications

Abstract: Employing the resonant-switch concept, a family of zero-voltage-switched multi-resonant converters (ZVS-MRCs) is derived from the conventional pulse-width-modulated (PWM) converters. By absorbing all essential circuit parasitics into the resonant network, the ZVS-MRCS are capable of operating in megahertz range, with high efficiency and power density. Characteristics of MRCs are reviewed, and their merits and limitations are assessed. Several applications and designs using the MRC technique are presented. A 50 W forward converter is designed for single and multiple-output on-board applications. The converter is fabricated using thick-film hybrid technique and attains a power density of 50 W/in/sup 3/. A 100 W offline half-bridge converter is designed for a computer distributed power system with 150-350 V input. A full-bridge converter is used for a pulse-load application with 1.5 kW peak power.< >

Bidirectional switching power apparatus with AC or DC output

Abstract: The bidirectional switching power apparatus converts DC input voltage into single AC or multiple DC output voltages. Power transformer is used if line isolation is necessary. Number of switching components and peak currents thereof are minimal. The DC input voltage is lower than the AC or DC output voltages. The switching power apparatus has a first and second capacitors coupled to ground for storing a first and second voltages respectively. One switch selectively applies the DC input voltage across an inductor which attains a current. Another switch selectively applies the current to ground. A diode applies the current to the first capacitor. An amplifier converts the first and second voltages into the AC output signal. Two other diodes apply the second voltage and AC output signal to a node. The DC input voltage is referenced to the node rather than ground.

Selective output disconnect for a single transformer converter

Abstract: A single transformer converter which may switchably disconnect all of its converter outputs, or alternatively just some of the converter outputs. In some electronic systems this would allow the turning-off of some units, such as printers, while leaving on other units, such as a CPU or a twenty-four hour clock. Further, an uninterruptible output is provided by the converter to maintain applications and operating systems software stored a CMOS RAM even in the event of a power outage.

Multiple-output, single-ended, resonant power converter

Abstract: A single-ended, resonant power converter includes an input filter having at least one primary winding and multiple auxiliary, or secondary, windings. A regulated input DC voltage is transformed directly to the auxiliary windings. The voltages across the auxiliary windings are respectively rectified and filtered to provide multiple, auxiliary, regulated output voltages which are independent of the main output voltage and converter switching frequency.

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.