A novel method oriented to evaluate the real characteristics ofpractical buck zero-voltage switching quasi-resonant converters

The output characteristics of buck zero-voltage switching quasi-resonant converters (ZVS-QRCs), presented in previously published works, are calculated considering equal input and output energies. Nevertheless, measurements that were taken with breadboarded buck ZVS-QRCs demonstrate an important deviation between the results of the theoretical analysis and the experimental data. This deviation becomes greater when the load current increases. This paper deals with a novel simulation method to approximate the real behavioral characteristics of Buck ZVS-QRCs. Analytical expressions are derived to calculate the power losses in each power converter component as well as the DC-voltage conversion ratio. Computer simulation results are confronted to experimental ones proving the effectiveness of the proposed method     

A zero-voltage and zero-current switching full bridge DC-DCconverter with transformer isolation

A new primary-side-assisted zero-voltage and zero-current switching full bridge DC-DC converter with transformer isolation is proposed. The proposed DC-DC converter uses only one auxiliary transformer and two diodes to obtain ZCS for the leading leg. It has a simple and robust structure, and load current control capability even in short circuit conditions, The possibility of magnetic saturation due to asymmetricity of circuits or transient phenomena is greatly reduced, which is a very attractive feature in DC-DC converters with transformer isolation. The power rating of the auxiliary transformer is about 10% of that of the main transformer. Operation of a 12 kW prototype designed for welding application was verified by experiments     

Utilization of an active-clamp circuit to achieve soft switching inflyback converters

Flyback derived power convertor topologies are attractive because of their relative simplicity when compared with other topologies used in low power applications. Incorporation of active-clamp circuitry into the flyback topology serves to recycle transformer leakage energy while minimizing switch voltage stress. The addition of the active-clamp circuit also provides a mechanism for achieving zero-voltage-switching (ZVS) of both the primary and auxiliary switches. ZVS also limits the turn-off di/dt of the output rectifier, reducing rectifier switching losses, and switching noise due to diode reverse recovery. This paper analyzes the behavior of the ZVS active-clamp flyback operating with unidirectional magnetizing current and presents design equations based on this analysis. Experimental results are then given for a 500 W prototype circuit illustrating the soft-switching characteristics and improved efficiency of the power converter. Results from the application of the active-clamp circuit as a low-loss turn-off snubber for IGBT switches is also presented     

A new active clamping zero-voltage switching PWM current-fed half-bridge converter

A new active clamping zero-voltage switching (ZVS) pulse-width modulation (PWM) current-fed half-bridge converter (CFHB) is proposed in this paper. Its active clamping snubber (ACS) can not only absorb the voltage surge across the turned-off switch, but also achieve the ZVS of all power switches. Moreover, it can be applied to all current-fed power conversion topologies and its operation as well as structure is very simple. Since auxiliary switches in the snubber circuit are switched in a complementary way to main switches, an additional PWM IC is not necessary. In addition, it does not need any clamp winding and auxiliary circuit besides additional two power switches and one capacitor while the conventional current-fed half bridge converter has to be equipped with two clamp windings, two ZVS circuits, and two snubbers. Therefore, it can ensure the higher operating frequency, smaller-sized reactive components, lower cost of production, easier implementation, and higher efficiency. The operational principle, theoretical analysis, and design considerations are presented. To confirm the operation, validity, and features of the proposed circuit, experimental results from a 200-W, 24-200Vdc prototype are presented.     

A novel method to achieve zero-voltage regulation in buck converter

The function control law for a buck converter is derived to achieve zero voltage regulation of the output voltage. A new method to retrieve the low frequency component of the inductor voltage is proposed and analyzed. The stability of the closed loop system using a proportional and differential controller is analyzed. The effect of the supply voltage and load current disturbance is also studied. The analysis, computer simulation by PSPICE and experimental results illustrate that excellent performance can be achieved by the function control law     

A new family of full-bridge ZVS converters

A family of soft-switched, full-bridge (FB) pulse-width-modulated (PWM) converters that feature zero-voltage-switching (ZVS) of all bridge switches over a wide range of input voltage and output load with minimal duty cycle loss and circulating current is described. The ZVS of primary switches is achieved by employing two magnetic components whose volt-second products change in the opposite directions with a change of phase shift between the two bridge legs. One magnetic component is a transformer while the other magnetic component is either a coupled inductor or a single-winding inductor. The transformer is used to provide isolated output(s), whereas the inductor is used to store energy for ZVS.     

A family of zero-voltage and zero-current-switching (ZVZCS) three-level DC-DC converters with secondary-assisted regenerative passive snubber

A detailed analysis and optimized-oriented design of a family of three-level soft-switching converters is presented. The zero-voltage-switching (ZVS) of the outer switches and zero-current-switching (ZCS) of the inner switches is realized by employing a pulse-width-modulation (PWM) phase-shift control and a secondary-assisted passive snubber. The switching operation is discussed by comparing the results produced by the use of different passive snubbers (the author's original one and literature-available ones). The voltage on the rectifier diodes is clamped at a reasonable value, specific to each one of the six snubbers taken into consideration. The voltage stress on each transistor is reduced to half of the input voltage. Lower rated transistors and rectifier diodes can be used, thus reducing the conduction losses. Before turning on/off the inner switches, the snubber's capacitor voltage determines the fall of the primary current to zero, thus avoiding wasteful energy circulation and assuring ZCS. The snubber's energy is recuperated to the load. The outcome of these improvements is a high efficiency in energy processing. Soft-switching-oriented constraints on the converter parameters are expressed as implicit equations, whose graphical solution permits the optimized design of the parameters in order to ensure ZVZCS. A comparative analysis of the effective duty cycle and the boost effect of it, due to the use of the secondary snubber, is performed. The influence of the choices of the parameters values on the regulation capability is pointed out. Experimental results prove the expected high performances of the optimized converters.     

A new method of analysis for PWM switching power converters

A new method of analysis for pulse-width modulation (PWM) switching power converters is presented. It allows one to find an approximate periodic solution for the converter vector state variable. The converter is modelled by a differential equation with periodic coefficients. This equation is substituted by an equivalent system of linear differential equations with constant coefficients. Only the forced (steady-state) solutions should be found for each equation of this system. The equations are solved in sequence. The final steady-state solution of the PWM differential equation is obtained as the sum of these forced solutions. The method allows one to find the converter dc transfer function and efficiency, to evaluate their frequency dependences, and to find the critical frequency and ripple. The first three equations of the equivalent system are usually adequate for practical purposes, and these equations are obtained by an easy formal procedure. One can also obtain the dynamic equation of the state variable dc component, and calculate the converter line to output and duty cycle to output transfer functions. A boost converter is used as an example to confirm the analytical results by numerical simulation.     

A forward converter topology employing a resonant auxiliary circuit to achieve soft switching and power transformer resetting

This paper presents a forward converter topology that employs a small resonant auxiliary circuit. The advantages of the proposed topology include soft switching in both the main and auxiliary switches, recovery of the leakage inductance energy, simplified power transformer achieving self-reset without using the conventional reset winding, simple gate drive and control circuit, etc. Steady-state analysis is performed herein, and a design procedure is presented for general applications. A 35-75-Vdc to 5 Vdc 100-W prototype converter switched at a frequency of 200 kHz is built to verify the design, and 90% overall efficiency has been obtained experimentally at full load.     

A new family of zero-voltage-transition PWM converters with dual active auxiliary circuits

A new family of active auxiliary circuits that allow the power switch in single switch, pulsewidth modulated converters to operate with zero-voltage switching is proposed in this paper. The main feature of an auxiliary circuit belonging to this family is that the auxiliary switch can operate with a zero-current switching turn-on and turn-off without increasing the peak current stresses of the main switch. This is an improvement over previous proposed auxiliary circuits where either the auxiliary switch operates with a hard turn-off or the circuit itself increases the peak stresses of the main switch. In this paper, the fundamental principles behind the proposed family of active auxiliary circuits are explained. Based on these principles, an example auxiliary circuit is systematically derived and presented along with several other auxiliary circuits belonging to the new family. The operation of a boost converter operating with the example auxiliary circuit is discussed in detail, and general guidelines for the design and implementation of auxiliary circuits belonging to the new family are given. The feasibility of the example auxiliary circuit is confirmed by experimental results obtained from a 500-W, 100-kHz boost converter laboratory prototype.     

An algorithm that uses forward planning to expedite conflict-freetraffic assignment in time-multiplex switching systems

In multichannel telecommunication networks, switching systems, and processor-memory interconnects, the need for conflict-free traffic assignment arises whenever packets (or requests) are to be directed from input buffers (processors) to specific outlets (modules). This paper presents an algorithm, based on forward planning, which can be used in the above-mentioned applications for scheduling conflict-free transfers of packets from inputs to outputs. The performance of the algorithm is evaluated in the sense of throughput and delay and is compared with that of system of distinct representatives (SDR), an earlier proposed algorithm featuring 100% assignment efficiency. Then, its worst-case computational complexity is compared with that of SDR and several suboptimal (but low complexity) algorithms reported in literature. The proposed forward planning algorithm is shown to have the lowest order of computational complexity and permits simpler buffer organization and access modes. Moreover, it is shown that forward planning of packet transmissions offers significant performance improvements if the finite capacity of buffers is taken into account     

A new method to regulate resonant converters

A resonant frequency-modulation method is presented as an alternative to the switching frequency-modulation method to regulate resonant converters. A switch-controlled inductor and switch-controlled capacitor, in which switching losses are found to be very low due to zero-current or zero-voltage switching, are developed to do so. A new family of resonant converters that are regulated at a fixed switching frequency is proposed. A steady-state analysis of the Class E resonant converter regulated by a switch-controlled capacitor is presented. Theoretical and experimental results verify the validity of the proposed method. The efficiency measured from a breadboard of 1 MHz, 5 V, 25 W Class E regulated resonant DC-DC converter is up to 83%     

Design-oriented analysis of common switching DC to DC converters

A general, computer-aided analysis of power electronic circuit dynamics is proposed. An automatic generation of dynamic models from a circuit specification is the starting point for a symbolic, automatable, exact, ‘top-down’ procedure, that contrasts with circuit-specific analyses. The algorithm is suitable for analysing any converter containing two reactive elements, covering the common switching power stages: buck, boost, buck-boost converters. The method is illustrated by application to the computation of the transient response of a boost converter; the computer results are compared with those obtained by applying the ‘state space averaging’ method and with laboratory results.     

A novel technique to achieve unity power factor and fact transientresponse in AC-to-DC converters

This paper presents a novel power factor correction technique for single-phase boost type AC-to-DC converters in continuous conduction mode. Instead of using the inductor current or switching device current, in this paper, the diode current in the boost converter is used to formulate the duty ratio of the switch in a special way which makes the input current sinusoidal and in phase with the input voltage. To improve the dynamic performance and minimize the input current harmonic components, a new double-injection compensation method is employed in the voltage feedback loop. The power factor corrector has the following advantages: (1) operation with constant switching frequency; (2) elimination of input voltage sensing, error amplifier in the current loop and multiplier in the output voltage feedback loop; (3) minimal total harmonic distortion in the input current; (4) fast dynamic response of the output voltage loop; and (5) simple implementation of the control circuit. The principles of operation of the proposed control scheme are explained. Simulation and experimental results are presented to verify the feasibility of the control strategy     

A DC-powered Josephson logic family that uses hybrid unlatchingflip-flop logic elements (Huffles)

This paper describes the development of a dc-powered Josephson logic family that uses hybrid unlatching flip-flop logic elements (Huffles). The Huffle circuit used in this study is modified by adding a parallel resistor to the original Hebard-type Huffle circuit. Analysis of the circuit's operation shows that the undesirable hung-up phenomena are prevented by this modification. Based on the result of the analysis, the circuit's parameters are derived and a typical operating margin of ±26% is obtained. Besides AND/OR operations using a threshold logic operation, two-input exclusive OR (XOR), two-input multiplexor (MUX), and three-input majority (MAJ) operations are realized using a Huffle gate in which 2-Josephson-interferometers (2JI) in the standard Huffle gate are replaced by stacked-2JI's. Thus, a Huffle logic family, formed from NOT, AND, OR, XOR, MUX, MAJ, and flip-flop (FF), are constructed. By using this Huffle logic family, a 6-b arithmetic logic operating unit (ALU), a 6-b analog-to-digital converter (ADC), and a 6-b gray-to-binary converter (GBC) have been successfully operated. During high-speed testing, a 1-b comparator was operated up to an input bandwidth of 6 GHz     

A new approach to the modeling of converters for SPICE simulation

An approach to the modeling of DC-DC converters for SPICE simulation is developed in which the average current in the energy-storage inductor is first simulated in a SPICE subcircuit for both the continuous and discontinuous modes of operation. The inductor current is then weighted and redistributed to related branches of the circuit to simulate the average input and output currents of the converter. Based on this technique, various converter models, including that of the Cuk converter with coupled inductors, which are valid for both continuous and discontinuous modes of operation, are developed     

A family of high power density unregulated bus converters

This paper begins by reviewing current bus converters and exploring their limitations. Next, a family of inductor-less bus converters is proposed to overcome the limitations. In the new bus converters, magnetizing current is used to achieve zero-voltage-switching (ZVS) turn-on for all switches. The resonant concept is used to achieve nearly zero-current-switching (ZCS) turn-off for the primary switches and no body diode loss for the synchronous rectifiers (SRs). Meanwhile, the self-driven method can be easily applied to save drive loss of SRs. Based on these concepts, a full-bridge bus converter is built in the quarter-brick size to verify the analysis. The experimental results indicate that it can achieve 95.5% efficiency at 500-W, 12-V/45-A output. Compared with industry products, this topology can dramatically increase the power density. These concepts are also applied to nonisolated dc/dc converters. As an example, a resonant Buck converter is proposed and experimentally demonstrated.     

Function control-a novel strategy to achieve improved performanceof the DC-to-DC switching regulators

The control strategy of the DC-to-DC switching converters is studied to obtain the switching regulators with zero-voltage regulation. A novel control strategy, the function control, is presented for the DC-to-DC switching converters to achieve this objective. The control law and the corresponding feedback are derived directly from the equations governing the switching converters. With the function control strategy presented in the paper, the switching regulators become robust, i.e., the output is independent of the disturbances from either the supply voltage or the load and exhibits other desirable advantages. The strategy is applicable to all the four basic PWM converters, i.e., buck, boost, buck-boost, and Cuk. The analysis is confirmed by experiments and computer simulations     

A family of low EMI unity power factor converters

A new family of soft-switching unity power factor converters with high input power factor and isolated output is presented. A feature of the converters is a significant reduction of conducted electromagnetic interference (EMI). Six converter topologies have been identified that share a zero-voltage-switching (ZVS) phase arm on the input boost converter stage. Detailed analysis and experimental results are presented on the double ZVS phase-arm resonant transition converter     

A new family of ZVS-PWM active-clamping DC-to-DC boost converters:analysis, design, and experimentation

The purpose of this paper is to introduce a new family of zero-voltage switching (ZVS) pulse-width modulation (PWM) active-clamping DC-to-DC boost power converters. This technique presents ZVS commutation without additional voltage stress and a significant increase in the circulating reactive energy throughout the power converters. So, the efficiency and the power density become advantages when compared to the hard-switching boost power converter. Thus, these power converters may become very attractive in power factor correction applications. In this paper, the complete family of boost power converters is shown, and one particular circuit, taken as an example, is analyzed, simulated and experimented. Experimental results are presented, taken from a laboratory prototype rated at 1600 W, input voltage of 300 V, output voltage of 400 V, and operating at 100 kHz. The measured efficiency at full load was 98%, and the power converter kept an efficiency up to 95% from 17% to 100% of full load, without additional voltage and current stresses