Operation analysis for Buck PFC converter in discontinuous capacitor voltage mode

The buck converter with LC input filter operating in discontinuous capacitor voltage mode has inherent power factor correction properties and continuous input current. The paper presents a detailed analysis of the converter operating in this mode, leading to design criteria. Finally, experimental results for a 48 V/sub dc//100 W converter are presented.

In this paper, a new bridgeless single phase ac-dc power factor correction (PFC) rectifiers based on Buck topology operating in Discontinuous Capacitor Voltage Mode (DCVM) is proposed. The bridgeless topology and the presence of only one or two semiconductor switches in the current flowing path during each interval of the switching cycle result in lower conduction losses compared to the conventional DCVM Buck PFC rectifier. The DCVM operation offers additional advantages such as: zero-voltage turn-off in the power switches, zero-voltage turn-on in the output diode, and continuous input current. Hence, the electromagnetic interference (EMI) noise emission is minimized. The converter achieves high power factor naturally with low total harmonic distortion (THD) in the input current. Theoretical analysis and experimental results for 100 W/48 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> at 100 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> line voltage are provided to evaluate the performance of the proposed scheme. The measured conversion efficiency reached 96.4%.

A new single‐switch, single‐stage power factor correction (PFC) converter based on discontinuous capacitor voltage mode (DCVM) is presented in this study. The conventional single‐stage PFC converters have high voltage across their bulk capacitor which imposes high voltage stress on the switch and also the bulk capacitor voltage stress increases at light load condition. The most important advantage of the proposed topology is that the voltage across the bulk capacitor is low and the input current is continuous. Furthermore, this topology does not have high voltage stress across the bulk capacitor at light loads. The proposed topology is derived from a DCVM buck converter integrated with a flyback converter. The proposed PFC topology contains low number of passive components and employs only one switch, resulting in reduced complexity and cost. The presented simulation and experimental results of the proposed converter justify the theoretical analysis.

In this paper, a series-capacitor-based interleaving buck power factor correction (PFC) converter is proposed, the intermediate energy storage capacitance of which is operated at discontinuous capacitor voltage mode (DCVM), and automatic power factor (PF) correction for this converter is obtained. Moreover, the voltage across the series capacitor of the proposed PFC converter is clamped at the input voltage, and thus peak voltage stress existed in the traditional DCVM buck PFC could be relieved. By effectively regulating the charge/discharge time for the series capacitor, ultrahigh step-down conversion ratio of the proposed converter is achieved, the conversion ratio of which is independent of the duty cycle and only related to the switching frequency and circuit parameters. Therefore, high PF can be obtained due to very narrow deadtime of the input current. Meanwhile, the proposed PFC converter can realize the soft turn- on of part power switch and soft turn- off of part power diodes. In addition, comparing with the traditional discontinuous inductor current mode PFC, the input current of the proposed PFC converter is continuous so that the peak value and root-mean-square value of input current can be reduced. The operational principle, performance analysis, and parameter design principle are given in this paper. The analysis results show that the PF and total harmonic distortion are also independent of the duty cycle. Finally, a 220-Vac input, 60 W/15 V output experimental prototype is built to verify the validity of the theoretical analysis.

Based on systematic decomposition of circuit graphs, a computer method for modelling a class of periodically switched networks is developed. The method is applicable to any switched network whose switching frequency is much greater than the natural frequencies of the constituent topologies. The method involves identifying the fast part of the circuit and separately modelling it as a time-invariant N-port. In modelling the fast part, the remaining slow part is treated as being composed of constant sources. The dynamics of the slow part is then restored in the final stage of the overall modelling. In this paper, the authors specifically discuss the modelling of the fast part of a periodically switched circuit such as the DC/DC converter, and demonstrate how it can be used to obtain a complete averaged model. The method is suited for any pulsewidth modulated (PWM) converter that operates in either operating modes. To illustrate the proposed method, the Cuk converter is considered and its averaged models derived for the three possible operating modes, namely continuous inductor current mode, discontinuous inductor current mode, and discontinuous capacitor voltage mode. >

The authors introduce a computer program based on an exact analytical description of the dynamic behaviour of the parallel resonant power converter. The program provides both time-domain and state-trajectories simulation of the converter state variables under different control strategies in continuous or discontinuous capacitor voltage mode. As a result, the regulator asymptotic stability can be predicted for large-signal operation. Experimental results verify the theoretical predictions. >

The duality principle is applied to derive new single‐stage power‐factor‐correction (PFC) voltage regulators. This paper begins with an application of duality transformation to conventional discontinuous‐conduction‐mode buck, buck‐boost and boost converters. The resulting dual converters operate in the discontinuous capacitor voltage mode. These new converters provide the same PFC property, but in the dual manner. It is proved that in the practical case of the input being a voltage source, the mandatory insertion of inductance between the voltage input and the ‘dual PFC converter’ does not affect the power‐factor‐correcting property. A new single‐stage PFC regulator is derived by taking the dual of a well‐known circuit based on a cascade of conventional boost and buck converters. Analytical design expressions are derived, illustrating the relation between current stress and component values. Experiments are performed to confirm the operation of the circuit and its power‐factor‐correcting capability. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Discontinuous capacitor voltage mode operation offers inherent power factor correction properties and continuous input current. A detailed analysis of a flyback-derived converter operating in this mode is presented in the paper and its application as a high power factor rectifier is studied. Finally, experimental results are presented.

A full bridge high-frequency link series parallel resonant converter (SPRC) operating in discontinuous current mode is analyzed using the state-space approach. The equations are solved using the PROMATLAB software. Design curves for the converter gain and other component stresses are presented in normalized form. The converter has been optimized for peak component stresses, and the corresponding design curves obtained from PROMATLAB and SPICE3 simulation are presented. Using the optimal design curves, a 250-kHz experimental converter operating on a wide input voltage (1:2) has been built to verify the theoretical and SPICE3 simulation results.

The boost cell operating in discontinuous conduction mode based on an approximate discrete-time difference equation is investigated. A qualitative discussion of the steady-state and open-loop dynamical behavior is presented. A linearized small-signal equation that leads to a linear feedforward control law for regulating this type of converter is derived. The conventional linear scheme provides satisfactory control in the neighborhood of the operating point, but ceases to meet the requirement as soon as the small-signal assumption is violated. A nonlinear feedforward control law whose validity extends over a wider range of fluctuation of the variables about the operating point is proposed, along with some simulation results that confirm the superiority of the proposed nonlinear control over its linear counterpart.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper presents the operating principle, analysis, design, simulation and experimental results for a high frequency (HF) transformer isolated AC-to-DC series-parallel resonant converter (SPRC) operating on the utility line, in discontinuous current mode (DCM). The equivalent models, the state space analysis of the SPRC in DCM are presented. PROMATLAB software is used to solve the equations and to obtain important design parameters. SPICE simulation and experimental results obtained from a 150 W prototype are presented to verify the analysis. High power factor operation (>0.99) with low harmonic distortion ( >

By adding a suitable LC filter to the input of a Buck converter, a high-power-factor buck converter is proposed. The converter can operate in the discontinuous-output-current mode operation. A Buck converter in this operation mode features simple control as the constant duty cycle PWM used. The operation condition of the converter is studied. The validity of analysis is verified by Simulation and Experimental results.

This study analyses the frequency response of a bidirectional series‐resonant DC/DC converter (SRC) working in a discontinuous mode (DCM). The converter can reach a voltage conversion ratio higher or lower than one, depending on whether the operation mode is step‐up or step‐down. The analysis is based on a novel mixed technique using both the state‐space average method and the Fourier method to obtain a state‐space averaged model of the converter. The study presents the model for the two operation modes. It also presents the frequency response of the output voltage as a function of the input voltage and as a function of the off‐time, which is the control parameter of the converter. The results of those transfer functions are compared with measurements in a 2000 W prototype. The model provides enough information to properly control the SRC in DCM.

This article describes a general method for studying the behavior of converters with three discontinuous conduction modes as automatic power factor correctors (PFCs). Some converters with a single discontinuous conduction mode (such as Buck-Boost, Flyback, SEPIC, Ćuk, and Zeta converters) can behave as automatic PFCs when operating in that discontinuous conduction mode, with a nearly constant duty cycle during each cycle of the line voltage. There are also dc/dc converters that, due to multiple diodes and inductors, can operate in different discontinuous conduction modes. A systematic method for studying these three discontinuous conduction modes was recently presented. This article extends that method to using the aforementioned dc/dc converters as part of an ac/dc converter with low harmonic injection in the line, identifying when the converters behave as “ideal automatic resistor emulators” (i.e., configuring ideal automatic PFCs) and when they behave as “quasi-ideal automatic resistor emulators” (i.e., as quasi-ideal automatic PFCs). As an example, the article examines a SEPIC converter used as a resistor emulator. In this case, three discontinuous conduction modes are possible, if the inductance of the input inductor is low enough to allow the input bridge rectifier diodes to stop conducting when the transistor is <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>. The study allows us to determine of the line current waveform when the converter operates in any of the possible discontinuous conduction modes. The results show that quasi-ideal automatic PFC behavior can be achieved in discontinuous conduction modes with low inductance values. Moreover, the results for the SEPIC can be easily extended to the Ćuk converter operating in the same manner. Finally, the theoretical predictions for the line current from the proposed study were verified through simulation using PSIM (in the case of both the SEPIC and Ćuk topologies), and through experimentation (in the case of SEPIC).

This paper presents a new single phase front-end ac-dc bridgeless power factor correction (PFC) rectifier topology. The proposed converter achieves a high efficiency over a wide range of input and output voltages, a high power factor, low line current harmonics and both step up and step down voltage conversions. This topology is based on a non-inverting buck-boost (Zeta) converter. In this approach, the input diode bridge is removed and a maximum of one diode conducts in a complete switching period. This reduces the conduction losses and the thermal stresses on the switches when compare to existing PFC topologies. Inherent power factor correction is achieved by operating the converter in the discontinuous conduction mode (DCM) which leads to a simplified control circuit. The characteristics of the proposed design, principles of operation, steady state operation analysis, and control structure are described in this paper. An experimental prototype has been built to demonstrate the feasibility of the new converter. Simulation and experimental results are provided to verify the improved power quality at the AC mains and the lower conduction losses of the converter.